Dissertations / Theses: 'Carbeni'

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Rocchi, Federico. "Triazolilideni funzionalizzati come versatili carbeni mesoionici in complessi luminescenti." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14438/.

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1,2,3-Triazolylidenes belong to the class of abnormal N-heterocyclic carbenes, which are singlet carbenes with the carbonic center directly bound to at least one nitrogen atom of the heterocycle, and no uncharged resonance structure can be drawn. Since their precursors synthesis is quite simple and it allows the variation of the substituents on the triazolic ring, the use of 1,2,3-triazolylidenes as bidentate ligands for appropriate metallic complexes is very interesting. In the present work I report the synthesis of 1,2,3-triazolium salts 1-benzyl-3-methyl-4-(pyridin-2-yl)-1H-1,2,3-triazol-3-ium (L1-X), 3-methyl-1-phenyl-4-(pyridin-2-yl)-1H-1,2,3-triazol-3-ium (L2-X) (X=OTf, I) and 1,1'-dibenzyl-3-methyl-1H,1'H-[4,4'-bi(1,2,3-triazol)]-3-ium iodide (L3-I), that after the formation of the corresponding triazolylidenes have been employed as bidentate ancillary ligands for the synthesis of three cationic Ir(III) complexes (A-BF4, B-BF4 e C-BF4) and a neutral one (D). The synthetized complexes were characterized with NMR spectroscopy, and DFT computational calculations have been performed to compare, once photophysical characterization has been made, the obtained results with experimental measures.

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Trevisan, Mauro <1989&gt. "Preparazione e reattività di "half-sandwich" carbeni complessi stabilizzati da leganti bipiridilici." Master's Degree Thesis, Università Ca' Foscari Venezia, 2016. http://hdl.handle.net/10579/9260.

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Carbeni complessi di rutenio del tipo [Ru(η5-C5Me5)(=CAr1Ar2)bpy]BPh4 1 (Ar1= Ar2= Ph a; Ar1= Ph, Ar2= p-tolyl, b; bpy= 2,2’-bipiridile) sono stati preparati trattando il cloro complesso [RuCl(μ-Cl)( η5-C5Me5)]2 prima con una quantità stechiometrica di dipiridile in presenza di zinco metallico in THF e successivamente con un eccesso dell’appropriato diazoalcano Ar1Ar2CN2usando come solvente una miscela di etanolo e diclorometano (1:1). Lo studio della reattività dei complessi 1 ha dimostrato che questi reagiscono con fosfiti per dare i prodotti di sostituzione [Ru(η5-C5Me5)(P(OEt)3)bpy]BPh4 10. Carbeni complessi di rutenio del tipo [Ru(η5-C5Me5)(=CAr1Ar2)4,4’(CH3)2bpy]BPh4 2 (, Ar1= Ar2= Ph a; Ar1= Ph, Ar2= p-tolyl, b; byp= 4,4’-dimetilbipiridile) sono stati preparati trattando il cloro complesso [RuCl(μ-Cl)( η5-C5Me5)]2 prima con una quantità stechiometrica di 4,4’-dimetilbipiridile in presenza di zinco metallico in THF e successivamente con un eccesso dell’appropriato diazoalcano Ar1Ar2CN2usando come solvente una miscela di etanolo e diclorometano (1:1). Tutti i complessi sono stati caratterizzati spettroscopicamente attraverso l’utilizzo di IR e NMR. Il carbene complesso [Ru(η5-C5Me5)(=C(Ph)p-tolyl)bpy]BPh4 1b è stato analizzato anche mediante diffrazione dei raggi X, determinando così la struttura cristallina.

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Bortolamiol, Enrica <1992&gt. "Sintesi, caratterizzazione e attività antiproliferativa di complessi allilici di Pd (II) con leganti carbeni N-eterociclici." Master's Degree Thesis, Università Ca' Foscari Venezia, 2019. http://hdl.handle.net/10579/14269.

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L’elaborato di tesi descrive lo studio di nuovi composti allilici di Pd(II) da impiegarsi come potenziali chemioterapici. Nello specifico sono stati sintetizzati complessi contenenti come leganti di supporto diversi carbeni N-eterociclici monodentati o chelanti. La loro attività antitumorale in vitro su sei diverse linee cellulari tumorali è stata testata unitamente a quella di altri complessi allilici precedentemente sintetizzati, allo scopo di individuare i composti con la miglior citotossicità verso le cellule tumorali. Nello specifico sono stati trattati carcinoma ovarico, tumore al colon, al polmone e melanoma , valutando infine anche l’effetto dei composti su cellule normali.

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Di, Girolamo Alessandro. "4-Fenil-1,2,3-triazoli come versatili leganti ciclometallanti in complessi luminescenti di Ir(III)." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.

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I complessi luminescenti di metalli di transizione costituiscono una classe di materiali che ha suscitato un notevole interesse soprattutto per le loro proprietà elettrochimiche e fotofisiche. Tra i vari complessi di metalli di transizione, i complessi di Ir(III) giocano un ruolo fondamentale in differenti applicazioni grazie alla loro versatilità sintetica, stabilità chimica e termica, elevata efficienza di emissione e modulabilità del colore emesso. Lo scopo del lavoro di Tesi è stato quello di sintetizzare complessi eterolettici luminescenti di Ir(III), basati su derivati 1,2,3-triazolilidenici e/o 1,2,3-triazolici come leganti ciclometallanti, per poi studiarne le proprietà fotofisiche ed elettrochimiche. E’ stata messa a punto una metodologia di sintesi per tre complessi eterolettici cationici luminescenti di Ir(III), impiegando come leganti ciclometallanti un 4-fenil-1,2,3-triazolilidene e/o un 4-fenil-1,2,3-triazolo. Il legante ancillare impiegato, la 4,4’-di-tertbutil-2,2’-bipiridina, è il medesimo per tutti e tre i complessi ottenuti al fine di studiarne le proprietà fotofisiche ed elettrochimiche al variare dei leganti ciclometallanti. I complessi ottenuti sono stati caratterizzati mediante spettroscopia di Risonanza Magnetica Nucleare (NMR), per avere conferma sulla loro struttura molecolare. Si sono valutate le proprietà elettrochimiche mediante voltammetria ciclica ed a onda quadra e si è proseguito con la caratterizzazione fotofisica. Quest’ultima comprende spettri di assorbimento a 298 K, spettri di emissione con calcolo delle rese quantiche e misura dei tempi di vita in soluzione (a 298 K ed a 77 K) ed allo stato solido. La caraterizzazione sperimentale è stata supportata dai risultati di un’analisi computazionale effettuata precedentemente dal gruppo di ricerca.

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Parise, Chiara. "Complessi carbenici N-eterociclici di rutenio: catalizzatori omogenei in reazioni di idrogenazione e deidrogenazione." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9255/.

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Il presente lavoro di tesi si inserisce in un progetto di ricerca volto alla sintesi di nuovi complessi di metalli di transizione per lo sviluppo di catalizzatori bifunzionali metallo-legante da impiegare in reazioni di catalisi omogenea, in particolare in reazioni redox quali idrogenazione e deidrogenazione attraverso il trasferimento di idrogeno. Il mio progetto ha riguardato la messa a punto della sintesi di complessi di Ru(0) che combinano leganti ciclopentadienonici e carbeni N-eterociclici e la sintesi dei corrispondenti complessi cationici per protonazione. Inoltre, è stato sintetizzato e caratterizzato un nuovo complesso cationico attraverso la metilazione del corrispettivo complesso neutro. I complessi sintetizzati sono stati utilizzati come precursori di catalizzatori nella riduzione tramite trasferimento di idrogeno del 4-fluoroacetofenone, valutandone l’attività catalitica in relazione a leganti, additivi e controioni. Allo scopo di delineare qualche ipotesi sul meccanismo di reazione sono stati effettuati diversi studi sulla reattività dei complessi impiegati in catalisi, in particolare usando la piridina come agente di “trapping”. Infine, è stato condotto uno studio preliminare dell’attività catalitica dei complessi sintetizzati nell’ossidazione di benzilalcol a benzaldeide. The present work is part of a research project that involves the study of new ruthenium-based transition metal complexes in order to develop new metal-ligand bifunctional catalysts to employ in homogeneous catalytic systems, in particular in redox reactions such as hydrogenation and dehydrogenation through hydrogen transfer. My project is focused on the optimization of the synthesis of Ru(0) complexes that combines different ligands as tetraphenylcyclopentadienone and N-heterocyclic carbenes and the synthesis of the corresponding cationic complexes by protonation. Furthermore, it is reported the synthesis and characterization of a new cationic complex obtained by methylation of the corresponding neutral complex. All the prepared complexes were employed as catalyst precursors in the transfer hydrogenation of 4-fluoroacetophenone and their performances were investigated in relation to the type of ligands, additives and counterions. The reactivity of these ruthenium complexes was also investigated with the aim of delineate some hypothesis on the reaction mechanism, in particular employing pyridine as a trapping agent. Finally, preliminary studies on the oxidation of benzyl alcohol have been carried out.

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Conti, Silvia. "Nuovi complessi carbenici-N-eterociclici di argento e rutenio: il ruolo del sale di imidazolio." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/6080/.

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Il presente lavoro di tesi si inserisce in un progetto di ricerca volto alla sintesi di nuovi complessi di metalli di transizione per lo sviluppo di catalizzatori bifunzionali metallo-legante da impiegare in reazioni di catalisi omogenea come, ad esempio, l’idrogenazione di doppi legami polari. In particolare, il mio progetto ha riguardato la sintesi e la caratterizzazione di nuovi complessi carbonilici di rutenio che combinano diversi leganti quali tetrafenilciclopentadienoni e carbeni N-eterociclici. Inizialmente è stato preparato il complesso dimerico ciclopentadienonico di rutenio carbonilico dicarbonil(η4-3,4-bis(4-metossifenil)-2,5-difenilciclopenta-2,4-dienone)dimero, utilizzato come precursore in tutte le sintesi dei nuovi complessi di rutenio. Successivamente, sono stati preparati numerosi sali di imidazolio da impiegare come precursori dei leganti carbenici N-eterociclici e i corrispondenti complessi di argento. La reattività dei complessi di argento nei confronti del precursore dimerico di rutenio dicarbonil(η4-3,4-bis(4-metossifenil)-2,5-difenilciclopenta-2,4-dienone)dimero ha portato alla formazione di complessi differenti a seconda dell’ingombro sterico del legante carbenico N-eterociclico. È stato inoltre approfondito lo studio della reattività dei sali di imidazolio, variandone ingombro sterico e sostituenti, per combinazione diretta con il precursore dimerico di rutenio dicarbonil(η4-3,4-bis(4-metossifenil)-2,5-difenilciclopenta-2,4-dienone)dimero.

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Ranalli, Augusto. "Sali d'imidazolio come precursori nella sintesi di complessi ciclopentadienonici di ferro: studio della reattività in etanolo." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24361/.

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Il progetto di tesi svolto ha avuto l’obiettivo di sintetizzare alcuni complessi ciclopentadienonici di ferro neutri e ionici e studiarne la reattività in etanolo per determinare un’eventuale attività catalitica per la reazione di Guerbet. Il ferro, sebbene ampiamente utilizzato in catalisi eterogenea, è stato impiegato molto poco in quella omogenea data la sua minore attività catalitica rispetto ai “metalli nobili” come il rutenio. Tuttavia, nell'ottica di una chimica più sostenibile, la ricerca si sta focalizzando sulla catalisi condotta da complessi omogenei a base di ferro e altri metalli della prima serie di transizione. Infatti, tale metallo risulta ampiamente disponibile nella crosta terrestre ed è molto meno costoso e meno tossico, pertanto il suo utilizzo in catalisi omogenea rende i processi più competitivi. La reazione che ci si è prefissati di studiare è la reazione di Guerbet che consente di trasformare del bioetanolo, proveniente dalle biomasse di scarto, a n-butanolo. Un processo molto elegante e pulito che permette di ottenere un combustibile alternativo, nonché un composto a maggior valore aggiunto come “building block” per la sintesi di prodotti per la chimica fine. Per poter incrementare l’attività catalitica dei complessi di ferro, sono stati impiegati dei leganti ciclopentadienonici data la loro natura non-innocente nelle reazioni di ossidoriduzione. Inoltre, sono stati impiegati anche i sali d’imidazolio, impiegati tal quali o come precursori dei leganti N-eterociclici carbenici (NHC), che contribuiscono alla stabilizzazione e all’attivazione dei complessi. Pertanto, durante l’attività di tirocinio, sono stati sintetizzati cinque tipi di complessi ciclopentadienonici di ferro e, una volta caratterizzati, sono stati testati in delle prove catalitiche e di reattività nelle condizioni idonee per la reazione di Guerbet di etanolo.

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Olivieri, Diego. "Sintesi e Caratterizzazione di Elettrodi Modificati Chimicamente con nuovi complessi Carbenici del Ferro." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11891/.

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The Chemically Modified Electrodes (CME) are widely used in electroanalytical chemistry as chemical sensors. The interest in the covalent anchoring of a redox mediator on the electrode surface is increasing, because it allows the sensibility and the selectivity of this kind of systems to improve. My work is situated in this field of research and involves the synthesis of new Iron(0) complexes that contain cyclopentadienone, N-heterocyclic carbene (NHC) and carbonyl ancillary ligands. These complexes have shown electrochemical properties similar to those of ferrocene (organometallic compound widely used as electrochemical sensor). These complexes have been properly functionalized with a EDOT group in the NHC ligand side chain that it was after used for the realization of Electrochemically Modified PEDOT thanks to copolymerization reaction between the functionalized complex and the EDOT in different amounts. All the synthetic steps were assisted by suitable characterizations (NMR, IR, ESI-MS, cyclic voltammetry and X-ray for the monomeric compound as imidazolium salt and NHC functionalized complexes; cyclic voltammetry, IR e SEM for the copolymers). The properties of the polymer as a selective sensor was preliminarily investigated for dopamine and 2-propanol.

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Teti, Martina. "Valorizzazione di bioetanolo attraverso la reazione di Guerbet ad opera di catalizzatori di rutenio supportati." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19272/.

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Il presente elaborato finale si inserisce in un progetto di ricerca volto alla sintesi di nuovi complessi di metalli di transizione supportati su resine polistireniche, per lo sviluppo di catalizzatori eterogenei di Rutenio(0), da impiegare nella reazione di conversione dell’etanolo in n-butanolo e alcoli superiori, nota come la reazione di Guerbet. In particolare, il mio tirocinio si inserisce in questo ambito all’interno di una collaborazione fra il gruppo di chimica metallorganica e quello di reattori e catalisi (Prof. Cavani) ed ha riguardato in primo luogo la sintesi e la caratterizzazione di un complesso di Rutenio(0) con leganti non-innocenti quali il ciclopentadienone e carbeni-N-eterociclici. L’attività catalitica del complesso omogeneo è stata valutata nella reazione di Guerbet. Il complesso di Rutenio è stato successivamente supportato su resine polistireniche consentendo così una separazione del prodotto semplificata e la possibilità di recuperare e riutilizzare il catalizzatore. Questa metodologia di sintesi è volta a combinare i benefici della catalisi omogenea con quelli della catalisi eterogenea. I campioni solidi preparati con questa tecnologia, sono stati caratterizzati mediante spettroscopia IR-ATR e ICP, ed infine l’attività catalitica dei composti supportati e la loro riciclabilità è stata valutata nella reazione di Guerbet.

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Sau, Roca Míriam. "From Click Chemistry to catalytic cleavage of unstrained C-C bonds." Doctoral thesis, Universitat Rovira i Virgili, 2016. http://hdl.handle.net/10803/396080.

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Aquesta tesi doctoral es basa principalment amb la síntesis de molècules petites potencialment útils per investigacions avançades. S'han utilitzat diferents metodologies per obtenir-les: 1) Cicloaddicions intramoleculars entre un alkí i una azida lliures de coure per l'obtenció de derivats de benzodiazepines. Obtenint-se una gran varietat de triazols fusionats a heterocicles de set membres. Posteriorment, s'han dut a terme proves d'activitat biològica. 2) a) Trencament d'enllaços carboni-carboni no activats d'amino alcohols i utilització d'aquest com a nucleòfil juntament amb bromurs d'aril en una reacció d'acoplament catalitzada per pal.ladi per l'obtenció de dibenzil amines. S'ha dut a terme una gran optimització dels diferents paràmetres de reacció; base, dissolvent, electròfil, temperatura, catalitzador i lligand. b) Trencament d'enllaços carboni-carboni no activats de N-alil amino alcohols i utilització d'aquest com a nucleòfil juntament amb bromurs d'aril en una reacció d'acoplament catalitzada per pal.ladi per l'obtenció d'aldehids arilats en la posició beta. S'ha dut a terme la síntesis d'un gran nombre d' amino alcohols nous i aquests han estat sotmesos a les condicions optimitzades de reacció. Demostrant que aquest transformació és útil per un gran ventall de substrats (bromurs d'aril i amino alcohols).L'enamina resultant de la reacció d'acoplament s'ha aconseguit alquilar amb vinil metil cetona amb bons rendiments però pobres diastereoselectivitats tot i així s'ha demostrant que la reacció és factible. Per finalitzar, s'ha aconseguit desenvolupar la versió enantioselectiva de l’anterior transformació obtenint bons excessos enantiomerics tot i que baixos rendiments.
Ésta tesis doctoral está basada principalmente en la síntesis de moléculas pequeñas potencialmente útiles para investigaciones avanzadas. Se han empleado diferentes metodologías para obtenerlas: 1) Cicloadiciones intramoleculares entre un alkino y una azida libres de cobre para la obtención de derivados de benzodiazepinas. Se han obtenido una gran variedad de triazoles fusionados a heterociclos de siete miembros. Posteriormente se han realizado pruebas de actividad biológica de las moléculas resultantes. 2) a) Escisión de enlaces carbono-carbono no activados de amino alcoholes y utilitzación de éstos como nucleófilos conjuntamente con bromuros de arilo para una reacción de acoplamiento catalizada por paladio para la obtención de derivados de dibenzil aminas. Se ha realizado una gran optimización de las condiciones de reacción; base, disolvente, electrófilo, temperatura, catalizador y ligando. b) Escisión de enlaces carbono-carbono no activados de N-alilo amino alcoholes y la utilización de éste como nucleófilo conjuntamente con bromuros de arilo en una reacción de acoplamiento catalizada por paladio para la obtención de aldehídos arilados en posición beta. Se ha realizado la síntesis de un gran numero de amino alcoholes nuevos y éstos se han sometido a las condiciones optimizadas de reacción. Demostrando que ésta transformación es útil para una gran variedad de sustratos (bromuros de arilo y amino alcoholes). La enamina resultante de la reacción de acoplamiento se ha alquilado con vinil metil cetona con buenos rendimientos pero pobres diastereoselectividades aunque se ha demostrado que la reacción es factible. Para finalizar, se ha desarrollado la versión enantioselectiva de la anterior transformación obteniendo buenos excesos enantioméricos aunque con bajos rendimientos.
This PhD thesis is based basically on synthesis of small molecules potentially useful for further investigations. Different strategies have been used to obtain them; 1) Copper free intramolecular cycloadditions between an azide and an akyne for the obtention of benzodiazepine derivatives. A wide range of triazoles fused to seven membered heterocycles rings have been obtained. Later, biological studies have been carried out. 2)a) Carbon-carbon bond cleavage of amino alcohols has been carried out with the subsequent use of them as a nucleophile together with aryl bromides to develop a cross-coupling reaction for the obtention of dibenzyl amines. A wide optimization of the reaction parameters was carried out; base, ligand, catalyst, electrophile, temperatura, and solent. b) Carbon-carbon bond cleavage of N- allyl amino alcohols has been carried out with the subsequent use of them as a nucleophile together with aryl bromides to develop a cross-coupling reaction for the obtention of beta arylated aldehydes. An important number of new amino alcohols have been synthesized and these have been subjected to the optimized reaction conditions. It has been demonstrated that this transformation is useful for a wide range of substrates (amino alcohols and aryl bromides). The resultant enamine has been alkylated with methyl vinyl ketone with good yields but poor diastereoselectivity. To finish the enantioselective version of beta functionalization of aldehydes has been developed obtaining good enantioselectivity but poor yields

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Maluenda, Borderas Irene. "(N-heterocyclic carbene) : metal catalysed carbon-carbon and carbon-heteroatom bond-forming reactions." Thesis, University of Sussex, 2018. http://sro.sussex.ac.uk/id/eprint/76274/.

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Sirokman, Gergely. "(N-heterocyclic-carbene)Copper(I)-catalyzed carbon-carbon bond formation using carbon dioxide." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39584.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2007.
Vita.
Includes bibliographical references.
This thesis presents work towards the development of a new catalytic C-C bond forming reaction. Alkynes and olefins insert into [(IPr)CuH]2 (IPr = N,N-bis-(2,6-diisopropylphenyl)-1,3-imidazol-2-ylidene) to give copper vinyl and copper alkyl complexes. These copper complexes insert CO2 into the Cu-C bond to form copper acrylate and copper carboxylate complexes. Acrylic and carboxylic acids can be isolated by hydrolysis. A catalytic cycle based on (IPr)copper(I) was developed. Alkynes undergo reductive carboxylation to give acrylic acids in moderate yields. Unexpected interactions between several components of the catalytic system led to a number of side reaction, most importantly between [(IPr)CuH]2 and the product silyl acrylate. The use of silylcarbonate salts to desylilate the product enhanced yield. In addition, silylcarbonates can also serve as a source of CO2.
by Gergely Sirokman.
Ph.D.

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Morell, Soler Francisco Joaquín. "Soil organic carbon dynamics and carbon sequestration in a semiarid Mediterranean agroecosystem: effects of conservation tillage and nitrogen fertilization." Doctoral thesis, Universitat de Lleida, 2012. http://hdl.handle.net/10803/101151.

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El balanç entre l´entrada de C (dels residus vegetals) i sortides de C (principalment com CO2 de la descomposició del carboni orgànic del sòl -SOC-), determina el contingut de SOC, que és el depòsit de C més voluminós a la superfície terrestre. Als agroecosistemes semiàrids Mediterránis, l’aigua és el principal factor limitant del creixement del cultiu i de l´entrada de residus al sòl. Les pràctiques agronòmiques alternatives poden millorar el creixement vegetal i augmentar la quantitat de residus (entrada de C) en aquestos sistemes. No obstant això la resposta del contingut de SOC dependrà del balanç de les entrades amb les sortides de C. Aquest treball estudia els efectes de l’adopció a llarg termini de sistemes de conreu (NT, sembra directa; MT, mínim conreu CT, conreu convencional) i del nivell de fertilizació nitrogenada (zero; mitjà, 60 kg N ha-1; alt, 120 kg N ha-1) al balanç de C del sòl i el contingut de SOC. El contingut de SOC augmentà finalment 4.3 i 3.9 Mg C ha-1 sota NT repecte a MT i CT. Nivells mitjans i alts de fertilització nitrogenada augmentaren el contingut de SOC en 3.4 i 4.5 Mg C ha-1 respecte al contingut a les parcel•les no fertilitzades. L´adopció a llarg termini de pràctiques de conreu de conservació (sembra directa), juntament amb l’ús adequat de la fertilització nitrogenada van demostrar ser eines per a millorar la sostenibilitat dels nostres secans i emmagatzemar C al sòl.
El balance entre la entrada de C (de los residuos vegetales) y salidas de C (principalmente como CO2 de la descomposición del carbono orgánico del suelo -SOC-), determina el contenido de SOC, que es el mayor depósito terrestre de C. En agroecosistemas semiáridos Mediterráneos, el agua es el principal factor limitante del crecimiento del cultivo y de la entrada de residuos en el suelo. Las prácticas agronómicas alternativas pueden mejorar el crecimiento vegetal y aumentar la cantidad de residuos (entrada de C) en estos sistemas. Este trabajo estudió los efectos de la adopción a largo plazo de sistemas de laboreo (NT, no-laboreo; MT, laboreo minimo; CT, laboreo convencional) y del nivel de fertilización nitrogenada (cero; medio, 60 kg N ha-1; alto, 120 kg N ha-1) en el balance de C del suelo y el contenido de SOC. El contenido de SOC aumentó en 4.3 y 3.9 Mg C ha-1 bajo NT con respecto a MT y CT. Niveles medios y altos de fertilización nitrogenada aumentaron el contenido de SOC en 3.4 y 4.5 Mg C ha-1 con respecto al contenido en las parcelas no fertilizadas. La adopción a largo plazo de prácticas de laboreo de conservación (no-laboreo o siembra directa), junto con el uso adecuado de la fertilitzación nitrogenada demostraron ser herramientas para mejorar la sostenibilidad de los secanos semiáridos Mediterráneos y almacenar C en el suelo.
The balance between C inputs (from plant residues) and C outputs (mainly as CO2 from soil organic carbon -SOC- decomposition) determines the content of SOC which is is the largest terrestrial reservoir of carbon. Under semiarid Mediterranean agroecosystems, water limitation restrains plant growth and the return of crop residues to the soil. Alternative agronomical practices may improve crop growth and increase return of crop residue (C inputs) under these systems. This work studied the effects of long term adoption of tillage practices (NT, no-tillage; MT, minimum tillage; CT, conventional tillage) and nitrogen (N) fertilization level (zero; medium, 60 kg N ha-1; high, 120 kg N ha-1) on the SOC balance and the content of SOC. The stock of SOC was increased by 4.3 and 3.9 Mg C ha-1 under NT in comparison to MT and CT respectively. Long-term medium and high N fertilization increased the stock of SOC by 3.4 and 4.5 Mg C ha-1 in contrast to unfertilized plots. Long-term adoption of conservation tillage practices (no-tillage) together with adequate N fertilizer use, proved to be effective tools to improve sustainability of semiarid Mediterranean drylands and to store C in the soil.

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Monticelli, Marco. "Novel di(n-heterocyclic carbene) ligands and related transition metal complexes." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3422292.

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In the last decades, N-heterocyclic carbenes (NHC) ligands have been studied by many groups due to their peculiarity in terms of major stability and versatility with respect to other type of ligands based on nitrogen (amines, imines, etc.) or phosphorous (phosphines, phosphites, etc.) donor atoms. Nowadays, the role of these ligands in the chemistry of transition metal complexes is pivotal, and the applications of the resulting compounds span from catalysis to luminescence to bioinorganic chemistry. This PhD, a collaboration between the University of Padova and the University of Strasbourg, is focused on the chemistry of di(N-heterocyclic carbene) ligands and can be divided in four families of ligands that constitute the four chapters: i) metal complexes with di(N-heterocyclic carbene) ligands bearing a rigid phenylene bridge between the carbene units; ii) metal complexes combining an imidazole-based NHC ligand functionalized with a triazole in the 5 position of the backbone; iii) metal complexes with heteroditopic ligands based on imidazol-2-ylidene and 1,2,3-triazol-5-ylidene moieties connected with a propylene bridge; iv) bis(benzoxazolium) proligands and attempted synthesis of related transition metal complexes. i) Metal complexes with di(N-heterocyclic carbene) ligands bearing a rigid phenylene bridge between the carbene units. Ortho- meta- and para-phenylene bis(imidazolium) salts have been used as proligands for the syntheses of various silver(I) complexes. These compounds, with general formula [Ag2L2](PF6)2 (L=di(N-heterocyclic carbene) ligand), have been used as transmetalating agents for the formation of the corresponding gold(I) and copper(I) complexes. These compounds maintain the same dinuclear dicationic molecular structure as for the silver(I) precursors, as confirmed by the resolved solid state crystal structures. The photoluminescence properties of the synthesized complexes have been studied and are strongly influenced by the structure of the di(NHC) ligand employed. In particular, the gold(I) complexes show interesting quantum yields of emission modulated by the geometry of the complex (distance between the two metal centers) and also by the packing of the complexes in solid state. With the ortho-phenylene silver(I) diNHC complex, the transmetalation was also successful for the access to mononuclear ruthenium(II) and iridium(III) complexes that show a chelate coordination of the ligand on the metal center. ii) metal complexes combining an imidazole-based NHC ligand functionalized with a triazole in the 5 position of the backbone. The copper catalyzed azide alkyne cycloaddiction reaction (CuAAC) also called “click reaction” has been used for the functionalization of the [5-(trimethylsilyl)ethynyl]-1-methylimidazole with a 1,2,3-triazole ring. As function of the methylating agents, it was possible to alkylate only the nitrogen on the imidazole ring (proligand i) or both on imidazole and triazole rings (proligands l and m). Starting from the proligands l and m, silver(I) complexes of stoichiometry Ag:L 1:1 (L=di(N-heterocyclic carbene) ligand) have been obtained, albeit with poor purity due to the oily nature of the products. Using the proligand i it has been possible to isolate a silver(I) complex of formula AgCl(NHC), which has been successively employed for the synthesis of gold(I), copper(I) and ruthenium(II) complexes. The in vitro cytotoxic activities of these compounds have been evaluated and in these preliminary results the silver(I) complex appears the most active and selective. iii) metal complexes with heteroditopic ligands based on imidazol-2-ylidene and 1,2,3-triazol-5-ylidene moieties connected with a propylene bridge. Heteroditopic proligands have been successfully synthesized using the CuAAC click reaction followed by methylation and anion exchange. A series of novel di-NHC gold(I) complexes, having general formula [Au2L2](PF6)2, have been synthesized and fully characterized through the transmetalation of the di-NHC moiety from pre-formed silver(I) complexes. The same pathway has been adopted for the synthesis of palladium(II) complexes that show the chelation of two ligands on the same metal center (i.e. homoleptic complexes). Due to the presence of two different carbene units (imidazole-2-ylidene and triazol-5-ylidene), it is possible to obtain a mixture of isomers which has been investigated by NMR and mass analyses. iv) bis(benzoxazolium) proligands and attempted synthesis of related transition metal complexes. Finally the chemistry of benzoxazole has been investigated. Different proligands containing benzoxazole rings have been synthesized starting from the corresponding diamine. These organic scaffolds have been used as proligands for the synthesis of metal complexes. Unfortunately, despite the various reaction conditions adopted (deprotonating agent, solvent, temperature, time...), the results obtained in this regard are not satisfactory, probably for the intrinsic instability of the ligand precursors and/or of the corresponding free carbenes.
Nelle ultime decadi, i leganti carbenici N-eterociclici sono stati studiati da numerosi gruppi in virtù delle loro peculiarità, quali maggiore stabilità e versatilità rispetto a leganti con atomi donatori all’azoto (ammine, immine etc.) o al fosforo (come per esempio fosfine, fosfiti ed altri). Attualmente, il ruolo di questi leganti nella sintesi di complessi con metalli di transizione è essenziale e le applicazioni dei corrispondenti complessi spaziano dalla catalisi alla luminescenza fino alla chimica bioinorganica. Questo dottorato, effettuato in collaborazione tra l’Università degli Studi di Padova e l’Università di Strasburgo, è focalizzato sulla chimica dei carbeni N-eterociclici e può essere diviso in quattro differenti capitoli: i) complessi metallici con leganti dicarbenici N-eterociclici legati da ponte fenilene rigido; ii) complessi metallici con legante carbenico N-eterociclico funzionalizzato con un triazolo in posizione 5 del backbone; iii) complessi metallici con leganti eteroditopici basati su unità imidazol-2-ilideniche e triazol-5-ilideniche legate tra loro mediante ponte propilenico; iv) leganti bis(benzossazolici) e tentativi di sintesi dei corrispondenti complessi con metalli di transizione. i) complessi metallici con leganti dicarbenici N-eterociclici legati da ponte fenilene rigido. Complessi di argento(I) sono stati sintetizzati partendo dai sali precursori dei leganti bisimidazolici con ponte orto- meta- e para-fenilenico. Tali complessi, con formula generale [Ag2L2](PF6)2 (L = legante dicarbenico N-eterociclico), sono stati usati come agenti di transmetallazione per l’ottenimento dei complessi di oro(I) e rame(I) corrispondenti; questi composti mantengono la medesima natura dinucleare dicationica dei precursori di argento, confermata dalla risoluzione delle strutture mediante diffrazione ai raggi X. Le proprietà di luminescenza dei complessi sintetizzati sono state studiate e sono fortemente influenzate dalla struttura del legante dicarbenico N-eterociclico utilizzato. In particolare i complessi di oro(I) presentano interessanti rese quantiche di emissione che variano a seconda della geometria del complesso (in termini di distanza tra i centri metallici) e soprattutto per il packing dei complessi allo stato solido. A partire dal complesso di argento con legante dicarbenico a ponte orto-fenilene, la reazione di transmetallazione è stata utilizzata per la sintesi di complessi mononucleari di rutenio(II) e iridio(III) che mostrano la chelazione dell’unità dicarbenica al centro metallico. ii) complessi metallici con legante carbenico N-eterociclico funzionalizzato con un triazolo in posizione 5 del backbone. La reazione di cicloaddizione azide alchino rame catalizzata (CuAAC) comunemente chiamata “reazione di click” è stata utilizzata per la funzionalizzazione del composto [5-(trimetilsilil)etinil]-1-metilimidazolo con un anello 1,2,3-triazolo. Utilizzando differenti agenti metilanti è possibile metilare solamente l’azoto dell’anello imidazolico (precursore del legante, i) o entrambi gli anelli imidazolico e triazolico (precursori dei leganti, l e m). Partendo dai precursori dei leganti, l e m, sono stati ottenuti complessi di argento(I) con rapporto Ag:L 1:1 (L = dicarbene N-eterociclico), anche se con bassa purezza a causa della natura oleosa dei prodotti. Utilizzando il precursore i è stato possibile isolare il complesso di argento(I) con formula AgCl(NHC), che è stato successivamente impiegato per la sintesi dei complessi di oro(I), rame(I) e rutenio(II). L’attività citotossica in vitro di tali composti è stata valutata e risultati preliminari mostrano un’attività e selettività maggiore per il complesso di argento(I) rispetto agli altri complessi metallici studiati. iii) complessi metallici con leganti eteroditopici basati su unità imidazol-2-ilideniche e triazol-5-ilideniche legate tra loro mediante ponte propilenico. Precursori dei leganti eteroditopici sono stati sintetizzati mediante reazione di click CuAAC, seguita da metilazione e scambio di anione. Una nuova serie di complessi di oro(I), con formula generale [Au2L2](PF6)2, è stata ottenuta mediante reazione di transmetallazione dell’unità dicarbenica N-eterociclica a partire dal complesso di argento(I) preformato. La medesima via sintetica è stata utilizzata per la sintesi di un complesso di palladio(II) che mostra la chelazione di due unità dicarbeniche allo stesso centro metallico. A causa della presenza di due diverse unità carbeniche (imidazol-2-ilidene e triazol-5- ilidene) è possibile ottenere una miscela di isomeri la cui composizione è stata analizzata mediante spettri NMR e tecniche di massa. iv) leganti bis(benzossazolici) e tentativi di sintesi dei corrispondenti complessi con metalli di transizione. Precursori dei leganti con anello benzossazolico sono stati sintetizzati a partire dalla relativa diammina. Queste molecole organiche sono state utilizzate come precursori dei leganti per la sintesi di diversi complessi con metalli di transizione. Sfortunatamente, nonostante le differenti condizioni di reazione utilizzate (agente deprotonante, solvente, temperatura, tempo…), i risultati ottenuti non sono soddisfacenti, probabilmente a causa dell’instabilità intrinseca dei precursori e/o dei relativi carbeni.

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Xiang, Ke. "Platinum carbene complexes with one heteroatom bonded to carbene carbon, synthesis and mechanisms." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ27557.pdf.

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16

Raya, Moreno Irene. "Effects of applying pine and corn cobs biochar on soil organic carbon in a Mediterranean agricultural land." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/664011.

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El canvi climàtic, produït per l’increment de la concentració de gasos d’efecte hivernacle a l’atmosfera, amenaça la integritat del nostre planeta. En aquestes circumstàncies el biochar, material obtingut a partir de biomassa pirolitzada, s’ha proposat com a una possible mesura per augmentar el segrest de carboni en sòls. L’aplicació de biochar en sòls pot servir com a magatzem de carboni a llarg termini compensant les emissions de CO2. No obstant, l’eficàcia del biochar depèn del tipus de biochar i sòl utilitzats. L’objectiu principal d’aquesta tesi és avaluar els efectes de l’aplicació de biochars de pi (PB) i de blat de moro (ZB) a una dosi de 6.5 g kg-1 en un sòl franco-arenós amb pH neutre i baix contingut de carboni orgànic (CO) en condicions de camp durant dos anys. Els objectius específics són els efectes de l’aplicació de biochar en : 1) la resistència termoquímica del CO del sòl (Capítol 1 i Capítol 2); 2) la disponibilitat del CO pels microorganismes (Capítol 3); 3) la protecció física del CO per oclusió en els agregats (Capítol 4). Els mètodes utilitzats per estudiar els efectes del biochar sobre la resistència del CO van ser: pèrdua de pes per ignició (LOI), combustió-seca (TOC), oxidació forta (sO) i feble (mO) amb dicromat-potàssic, hidròlisis-àcida (AH), oxidació amb peròxid d’hidrogen (PO) i anàlisis-isotòpic. A més, el CO-resistent del sòl i del biochar es va estimar mitjançant un balanç de masses. També, es van dur a terme dos mostrejos de sòl a curt i llarg termini (2 i 26 mesos), i es van incubar durant 250 dies. El dia 30 i 250 d’incubació va ser determinada la quantitat i la senyal isotòpica del CO2-C respirat. Addicionalment, es va mesurar el CO-dissolt en les mostres de sòl mitjançant el mètode d’extracció amb aigua-calenta. Les propietats físiques van ser avaluades quantificant el pes dels agregats estables amb aigua destil·lada i de la fracció en partícules amb hexametafosfat (per la disgregació dels agregats) utilitzant el wet-sieving apparatus. A més, el CO procedent del sòl natiu i del biochar dins i fora dels agregats es va estimar mitjançant un balanç de masses utilitzant el mO i el TOC. També es va estimar la contribució de CO del sòl i del biochar en els sòls esmenats amb ZB utilitzant el anàlisis-isotòpic. Es van trobar quantitats de ROC similars en els sòls controls estimats mitjançant mO i AH (5 g CO kg-1), mentre que més contingut de ROC es va observar en els sòls esmenats (6-12 g CO kg-1). La presencia de biochar es va detectar en els sòls esmenats mitjançant la comparació del δ13C en sòls esmenats i no-esmenats, independentment de l’origen del biochar. D’altra banda, el 35% del CO del biochar de ZB dels sòls esmenats es va perdre en dos anys com a resultat de la dissolució del biochar en el sòl. A curt termini, es va observar un priming-negatiu en sòls esmenats amb PB i el contrari en sòls esmenats amb ZB, en resposta al major contingut de CO-làbil del ZB. No obstant, un lleuger priming negatiu es va observar en els dos sòls esmenats a mig termini ja que augmenta la protecció física del CO. Mentre el PB tendeix a ser incorporat en els agregats, el ZB promou l’oclusió del CO natiu del sòl. Al esgotar-se el CO-làbil, el CO queda protegit dins dels agregats. Per tant, l’aplicació del biochar en sòls agrícoles mediterranis augmenta la persistència del CO en el sòl com a resultat de la resistència innata del CO del biochar i la protecció física augmentant el contingut de CO dins dels agregats.
El incremento de gases de efecto invernadero en la atmosfera puede tener consecuencias severas para nuestro planeta. El uso de biochar como enmienda, material obtenido a partir de biomasa pirolizada, se ha propuesto como estrategia para el secuestro de carbono en el suelo. Sin embargo, la efectividad del biochar varía mucho dependiendo del biochar y el tipo de suelo. El objetivo principal de esta tesis es evaluar los efectos de dos biochares, de restos de pino (PB) y mazorca de maíz (ZB), incorporados a una dosis de 6.5 g kg-1 en un suelo de viña franco-arenosa con pH neutro y bajo contenido de carbono orgánico (CO), en condiciones de campo durante dos años. Los objetivos específicos fueron la evaluación de: 1) la resistencia del CO en el suelo a los procesos termoquímicos (Capítulo 1 y Capítulo 2); 2) la disponibilidad de CO a ser mineralizada por microorganismos del suelo (Capítulo 3); y 3) protección física de CO por aumento de agregados (Capítulo 4). Los métodos analíticos utilizados para evaluar los efectos del biochar en el CO resistente del suelo fueron: pérdida de peso por ignición (LOI), combustión-seca (TOC), oxidación fuerte (sO) y suave (mO) con dicromato potásico, hidrólisis-ácida (AH), oxidación con peróxido de hidrogeno (PO) y análisis isotópico. Además, se estimó el CO-resistente del suelo y del biochar a través de un balance de masas. Por otro lado, el suelo se muestreó a corto y medio plazo (2 y 26 meses) y las muestras se incubaron en el laboratorio durante 250 días. Se determinó el CO2-C liberado durante la respiración del suelo y la señal isotópica del día 30 y 250 de incubación. Además, se cuantificó el CO disuelto mediante un extracto con agua caliente. Para evaluar las propiedades físicas, se determinaron los agregados estables en agua destilada y el peso de la fracción particulada con hexametafosfato para la disrupción de los agregados usando el wet-sieving apparatus. El CO oxidable del suelo nativo y del biochar dentro y fuera de los agregados se estimó a través de un balance de masas usando mO y TOC. Por otro lado, mediante el análisis isotópico se estimó la contribución de CO del suelo nativo y del biochar en suelos enmendados con ZB. Se cuantificaron valores similares de ROC en los suelos control mediante AH y mO (5 g C kg-1), mientras que se obtuvieron valores de ROC más altos en los suelos enmendados con biochar (6-12 g C kg-1). Además, la detección cualitativa de biochar se logró comparando δ13C en suelos enmendados y controles, independientemente del origen del biochar. Sin embargo, el 35% de ZB-CO se perdió durante los dos años de experimento por dilución del biochar en el suelo. A corto plazo se observó un priming-negativo en suelos enmendados con PB y al contrario en los suelos con ZB debido al mayor contenido de CO-lábil en ZB comparado con PB. Sin embargo, se encontró un priming ligeramente negativo a medio plazo en ambos suelos enmendados con biochar, como consecuencia de una mayor protección física del CO. Mayores cantidades de TOC y BOC se encontraron en los agregados de los suelos enmendados aunque tuvieron lugar dos procesos diferentes, mientras el PB tiende a incorporarse en agregados el ZB promueve la oclusión del CO del suelo nativo. Al agotarse el CO-lábil, el CO-ocluido queda protegido previniendo las pérdidas adicionales por degradación. Por lo tanto, la aplicación de biochar a un suelo agrícola mediterráneo aumenta la persistencia del CO del suelo debido a la resistencia innata al biochar-CO y la protección física del CO, que previene la degradación biótica o abiótica del CO.
The increment of global threats due to climate change, caused by an increase in atmospheric concentration of GHGs, is predicted to have a severe impact on our planet. The use of biochar, obtained from the thermochemical conversion of biomass in an oxygen-limited environment, as a soil amendment has been proposed as one strategy for C-sequestration. Many environmental benefits have been attributed to the application of biochar into soil, including long-term C-sequestration compensating for CO2 emissions. However, biochar effectiveness still remains under debate because effects can vary greatly depending on biochar and soil type. The main objective of this thesis was to assess the effects of two contrasting biochars, from pine wood (PB) and corn cob (ZB) remains, incorporated at a rate of 6.5 g kg-1 on a sandy loam vineyard soil with neutral pH and low organic carbon (OC) content, in field conditions over two years. Specifically, the aims were to evaluate the consequences of the addition of the different biochars on: 1) soil OC resistance to thermochemical processes (Chapter 1 and Chapter 2); 2) the potential OC availability to be mineralized by soil microorganisms (Chapter 3); and 3) physical OC protection by the promotion of aggregates (Chapter 4). The analytical methods used to evaluate the effects of biochar in soil OC-resistance were: weight loss-on-ignition (LOI), dry-combustion (TOC), strong (sO) and mild (mO) acid potassium dichromate oxidations, acid hydrolysis (AH), peroxide-oxidation (PO) and isotope analysis. Moreover, soil and biochar resistant-OC (ROC) was estimated through a mass balance. Also, soil field samples were collected at the short- and the medium-term (2 and 26 months after the application, respectively), and then incubated in the lab for 250 additional days. The CO2-C released as soil respiration and the CO2-C isotopic signature were assessed after 30 and 250 days of the incubation. Additionally, dissolved-OC was assessed in the field soil samples by hot-water extraction. Regarding physical properties, water-stable aggregates and particulate fraction weight were determined using a wet-sieving apparatus, using distilled water or hexametaphosphate for aggregates disruption. Oxidisable and resistant OC (attributed mainly to native soil and biochar, respectively) inside and outside of aggregates was estimated through a mass balance using mO and TOC. On the other hand, native soil and biochar-OC contribution in ZB biochar-amended soil was estimated by isotope analysis. The ROC estimated by AH and mO led to similar values in control soil (5 g C kg-1 soil), whereas higher ROC values were obtained in biochar-amended ones (6-12 g C kg-1 soil). Moreover, qualitative biochar detection was achieved by comparing δ13C in amended and non-amended soils regardless of the biochar feedstock origin. However, 35% of ZB biochar-OC was apparently lost over two years, which was attributed to biochar dilution into soil. In addition, in the short-term, negative-priming was observed in amended-soil with PB (made at high temperature) whereas positive-priming was seen in those amended with ZB (produced at lower temperatures) as a result of the highest labile-OC content in ZB biochar compared to PB. However, in the medium-term, slightly negative-priming effects in both biochar-amended soils were found. This could be explained by promotion of physical protection processes preventing priming. This fact was corroborated as higher TOC and BOC amount was observed inside of aggregates in biochar-amended soils compare to controls. It seems that PB tended to be incorporated into aggregates while ZB promoted native soil-OC occlusion. Then, after labile-OC has been exhausted, the promotion of OC occlusion prevented further losses. Therefore, the application of biochar to a Mediterranean agricultural soil increases soil-OC persistence due to innate biochar-OC resistance and OC physical protection, which decrease OC degradation by abiotic and biotic agents.

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Swain, Nigel Alan. "C H insertion approach to the total synthesis of furofuran lignans and their heterocyclic analogues." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288472.

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18

Harjung, Astrid. "Impact of drought periods on carbon processing across surface-hyporheic interfaces in fluvial systems = Impacte dels períodes de sequera sobre el processat de carboni a través de la interfase superficial i zona hiporreica en sistemes fluvials." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/586040.

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Headwater streams essentially link the terrestrial and the aquatic carbon cycle because they transport terrestrial organic and inorganic carbon downstream towards the oceans. However, most of these inputs are processed during this journey. These processes include down-break of particulate organic matter, transformation and respiration of dissolved organic matter and furthermore, in-stream production of organic matter. In particular, during drought periods the aquatic processes gain importance because terrestrial inputs are diminished. Therefore, carbon cycling in the remaining surface and subsurface flow of the main channel is accelerated and driven by the connectivity of these compartments. As the surface flow ceases carbon processing rates along subsurface flow paths, namely the hyporheic zone, increase. In the light of climate change, longer drought periods, including in currently humid areas, are expected. Within this context, this thesis aims to understand carbon processing across the surface-hyporheic interface of a Mediterranean intermittent stream during a summer drought. Since dissolved organic matter represents the key energy source of aquatic metabolism that ultimately determine in-stream carbon cycling, we focused on the organic matter quantity and quality. We found increasing retention rates of dissolved organic matter along hyporheic flowpaths as water residence time in this compartment increases with the ceasing of surface flow. The evaluation of optical indices of dissolved organic matter quality revealed that the molecular weight decreased and indices related to biological activity increased. Furthermore, we showed that dissolved organic matter from primary production is rapidly respired in the remaining surface water, while humic-like compounds are processed and respired in the hyporheic zone. The dissolved organic matter processing in the hyporheic zone was paralleled with observations of disproportional high partial pressure of CO2 in the interstitial pore water. These CO2 pulses were related to the desiccation of the streambed, as well as dissolved organic matter availability. Our results suggested that the hyporheic zone acts as a humid refuge for microbial activity and that respiration activity immediately restarts when rain events reestablish subsurface flow paths. Associated with this microbial activity, during drought the processing rates of dissolved organic matter, as well as the processing rates of inorganic nutrients were enhanced. Moreover, we explored the effects of a summer drought on subalpine streams by applying different discharge levels in stream-side flumes fed by the water of a subalpine stream. In this experiment, we found high dissolved organic carbon release from in-stream processes in the flumes with the lowest discharges. This dissolved organic carbon release was at the beginning paralleled with a transient increase in gross primary production but continued to rise even when primary production collapsed. While the collapse of primary production might be a consequence of phosphor limitation, respiration and degradation of dissolved and particulate organic matter in the sediment continued throughout. In line with our findings from the Mediterranean stream, this mesocosm experiment highlighted the importance of the hyporheic zone and organic matter stored therein for carbon processing during drought periods. In both study sites, the surface water metabolism was ultimately dominated by respiration, and dissolved organic matter quality of the surface water played an important role on processes in the hyporheic zone. Although the investigated study sites were different in many aspects we found surprising similarities in carbon processing with flow reduction. This suggests that findings from Mediterranean streams might be transferable to other climatic regions under global change scenarios.
Els rius de capçalera connecten essencialment el cicle del carboni terrestre i aquàtic, donat que transporten el carboni orgànic i inorgànic terrestre aigües avall. Durant els períodes de sequera, els processos aquàtics guanyen importància perquè les aportacions terrestres es redueixen. A mesura que l’aigua de la superfície desapareix, les taxes de processament de carboni al llarg de la zona hiporreica augmenta. Atès que, la matèria orgànica dissolta és la principal font d'energia del metabolisme aquàtic que, en aquesta tesis se centra en la quantitat i la qualitat de la matèria orgànica. Hem trobat un augment de la retenció de la matèria orgànica dissolta en medi hiporreic, ja que el temps de residència de l'aigua en aquest compartiment augmenta amb el cessament de aigües superficials. L'avaluació dels índexs òptics de la qualitat de la matèria orgànica dissolta va revelar que el pes molecular es va reduir, i es van incrementar els índexs relacionats amb l'activitat biològica. Vam demostrar que la matèria orgànica dissolta de la producció primària es respira ràpidament en l'aigua superficial restant, mentre que els compostos més húmics es processen i es respiren a la zona hiporreica. Els nostres resultats suggereixen que la zona hiporreica actua com un refugi humit per a l'activitat microbiana i que l'activitat de la respiració es reinicia immediatament quan els esdeveniments de pluja restableixen el flux hyporheic. A més a més, es van explorar els efectes d'una sequera en rius de capçalera subalpins aplicant diferents nivells de caudal en mesocosms. En aquest experiment, vam trobar una elevada alliberació de carboni orgànic dissolt fruit dels processos aquàtics en els mesocosms de cabals més baixos. Al principi, aquest augment de carboni orgànic dissolt va anar acompanyat per un increment transitori de la producció primària bruta, però va continuar augmentant fins i tot quan la producció primària es va col·lapsar. En els dos llocs d'estudi, el metabolisme de l'aigua superficial va estar dominat per la respiració; i la qualitat de la matèria orgànica dissolta de l'aigua superficial va jugar un paper important en els processos de la zona hiporreica.

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19

Martinčić, Markus. "Encapsulation of inorganic payloads into carbon nanotubes with potential application in therapy and diagnosis." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/458136.

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Los nanotubos de carbono representan un grupo de materiales relativamente nuevo con potencial aplicación en diferentes áreas científicas. Esta tesis se centra en beneficiarse de sus cavidades internas para encapsular compuestos biomédicamente relevantes. Los nanotubos de carbono permiten el confinamiento de materiales en su interior impidiendo su fuga y, en consecuencia, reduciendo los efectos secundarios, no deseados, de estos materiales en el medio circundante. Esto hace que los nanotubos de carbono sean unos vectores elegantes para el diagnóstico y tratamiento de enfermedades. Se ha demostrado que el proceso utilizado para purificar muestras de nanotubos de carbono permite no sólo la reducción de impurezas, que podrían causar citotoxicidad, sino también acortar la longitud de los nanotubos. Teniendo en cuenta que el análisis termogravimétrico es una técnica ampliamente utilizada para evaluar la pureza de muestras de nanotubos de carbono, se ha investigado la influencia que tienen diferentes parámetros que controlan este análisis para asegurar que los resultados obtenidos son lo más precisos y representativos posible. El proceso de purificación también ha sido reajustado para minimizar la cantidad de catalizador en muestras de nanotubos de carbono. También hemos desarrollado un protocolo que permite determinar el contenido de catalizador en muestras de nanotubos de carbono mediante espectroscopía ultravioleta-visible de una manera precisa y fiable. Se ha investigado la preparación de cloruro de samario(III) anhidro a partir de óxido de samario(III), así como la capacidad que ofrece el material preparado para el llenado de nanotubos de carbono, ya que éste tiene interés para el desarrollo de radiotrazadores. El proceso de llenado de nanotubos de carbono resulta en muestras que contienen grandes cantidades de material externo, no encapsulado, lo cual puede comprometer el rendimiento del material en el contexto biológico. Hemos desarrollado un protocolo para monitorizar la eliminación del material no encapsulado a través de espectroscopía de ultravioleta-visible, que a la vez permite mejorar el procedimiento de lavado. El uso de nanotubos de carbono multicapa tiene algunos beneficios sobre sus homólogos monocapa debido a la presencia de una cavidad interna más grande que puede contener más material. Se ha investigado el cierre espontáneo de las puntas de nanotubos de carbono multicapa a través de su calentamiento térmico a diferentes temperaturas, así como la encapsulación de distintos materiales en el mismo rango de temperaturas. Finalmente, distintas muestras de nanotubos de carbono multicapa llenos han sido examinadas in-vitro con el fin de evaluar su citotoxicidad y la captación celular de los nanosistemas desarrollados.
Carbon nanotubes present a relatively novel group of materials with potential application in different scientific fields. The scope of this Thesis is to benefit from their inner cavities to encapsulate biomedically relevant payloads. Carbon nanotubes allow the confinement of selected materials within their walls, preventing their leakage and, as a consequence, undesired effects of such materials to the surrounding media. This makes filled carbon nanotubes very elegant vectors for the diagnosis and therapy of diseases. The process used to purify samples of carbon nanotubes proved to be a valuable asset, not only in the reduction of impurities which might cause cytotoxicity, but also for shortening the length of nanotubes. Thermogravimetric analysis is a widely-used technique in evaluating the purity of carbon nanotube samples. The role of different parameters that control the analysis has been investigated to assure that the most appropriate and representative results are obtained. The purification process has also been readjusted to assure the presence of the lowest amount of catalyst possible in the carbon nanotube samples with the employed purification strategy. We have also introduced a simple UV-Vis spectrophotometric assertion of the catalyst content in samples of nanotubes in a precise and reliable manner. The preparation of dry samarium(III) chloride from samarium(III) oxide was investigated, together with the nanotube filling-ability of the prepared material, of interest for the development of radiotracers. Bulk filling of carbon nanotubes results in samples that contain a large amount of external, non-encapsulated material, which can compromise the performance of the material in the biological context. We have developed a protocol to monitor the removal of the non-encapsulated material by means of UV-Vis, which in turn allows improving the washing procedure. The usage of multi-walled carbon nanotubes has some benefits over their single-walled counterparts, due to the presence of a bigger cavity which can host more material. The spontaneous closure of the tips of multi-walled carbon nanotubes by thermal annealing was investigated at different temperatures, along with the encapsulation of different materials. The prepared filled multi-walled samples were tested in-vitro to assess cytotoxicity and cellular uptake of the developed nanosystems.

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Puigcorbé, Lacueva Viena. "Use of 234Th:238U disequilibrium to estimate particulate organic carbon export in the upper ocean." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/399280.

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L’exportació de carboni fixat mitjançant la fotosíntesi pel fitoplàncton, des de la superfície dels oceans a les capes més profundes, és un component clau de la bomba biològica de carboni i, per extensió, del cicle global del carboni, ja que manté els nivells de CO2 atmosfèrics per sota d’on es trobarien en l’actualitat si aquest procés no es donés (Feely et al., 2001; Khatiwala et al., 2009; Parekh et al., 2006). El cicle de les partícules i la seva exportació són també essencials pels cicles biogeoquímics d’altres macronutrients i espècies químiques de vital importància per la biota marina, així com metalls i contaminants d’origen antropogènic. El parell de radiotraçadors 234Th:238U ha estat utilitzat de forma extensa en l’estudi de l’exportació de partícules i en la determinació de la força de la bomba biològica de carboni en els oceans (Coale and Bruland, 1985; Le Moigne et al., 2013b). Aquesta tesi avalua els fluxos d’exportació de carboni als oceans i l’eficiència del segrest de diòxid de carboni mitjançant processos biològics fent ús d’aquest parell de radiotraçadors naturals en diversos règims oceanogràfics i sota contrastades condicions biogeoquímiques. En primer lloc, la variabilitat de l’export a escala de conca oceànica va ser examinada a l’Atlàntic Nord- Occidental al llarg d’un transsecte latitudinal (de 64ºN a l’equador) amb alta resolució espacial, proveint dades addicionals en zones sub-mostrejades. Els resultats, que coincideixen amb estudis previs que varen tenir lloc al Nord Atlàntic, van ser comparats amb diferents models d’exportació derivats de satèl·lits. Aquests models tenen una forta dependència en les estimacions de temperatura superficial del mar i producció primària neta, però normalment no consideren paràmetres biològics que influencien l’exportació de carboni, com ara l’estructura de la xarxa tròfica, la intensitat de depredació, l’eficiència de reciclatge, l’activitat bacteriana o l’exportació de carboni orgànic dissolt (Maiti et al., 2013). Les diferències observades entre les estimacions d’exportació de carboni derivades dels models de satèl·lits o del mètode del 234Th posen de manifest la necessitat d’incloure aquest tipus de paràmetres biològics a escala regional, per la qual cosa són necessaris esforços continuats d’observació. La inclusió d’aquests paràmetres reduiria la incertesa de l’inventari de carboni global i milloraria el monitoratge del cicle del carboni des de plataformes basades en satèl·lits. En segon lloc, la zonació de les propietats de les aigües superficials derivades dels diferents fronts localitzats al llarg d’un transsecte a 10ºE, de 44ºS to 53º S, en el Corrent Circumpolar Antàrtic va ser avaluada en relació amb l’exportació de partícules. Els nostres resultats mostren com, malgrat el contrast en les xarxes tròfiques observades al nord i al sud del Front Polar Antàrtic (~49ºS), la magnitud dels fluxos d’exportació de carboni era similar al llarg del transsecte. Existien diferències, però, en examinar les eficiències de transferència: a la meitat nord de la secció, la qual estava dominada per nanofitoplàncton, presentava eficiències d’exportació altes i eficiències de transferència baixes en comparació a la meitat sud de la secció, dominada per microfitoplàncton. Així doncs, malgrat que els diferents règims de xarxa tròfica donaren lloc a exportacions de carboni similars, el conjunt de partícules que sedimentaven diferia en la seva composició entre el nord i el sud del Front Polar Antàrtic (agregats de partícules petites en el nord vs partícules grans de sedimentació ràpida al sud), donant lloc a dos escenaris diferents pel que fa a la quantitat de carboni exportat que arribà a les capes més profundes. Per últim, les estimes del flux de partícules i l’eficiència d’exportació van ser examinades a una conca semitancada (el Golf de California i les aigües adjacents del Pacífic Tropical Nord Oriental) amb una estacionalitat molt marcada que va acompanyada de canvis en la comunitat fitoplanctònica. Les estimes d’exportació es varen obtenir mitjançant el mètode del 234Th, juntament amb trampes de sediment. Les dades de fraccionament per mides i l’alta ressolució vertical obtingudes amb bombes in situ van permetre la comparació de l’atenuació amb la fondària de les ràtios C/234Th entre partícules petites (1-53 μm) i grans (>53 μm). El resultats indiquen que, sota el domini de pico- i nanoplàncton i amb la presència de diazotrofs, les partícules petites juguen un paper important en l’exportació de carboni i que aquest export, en la zona d’estudi en qüestió, pot ser més eficient que l’export resultant d’una comunitat planctònica dominada per diatomees.
The particulate export of photosynthetically fixed carbon from the surface ocean to the ocean interior by marine plankton is a key component of the biological carbon pump and, by extension, of the global carbon cycle as it helps to maintain atmospheric CO2 levels lower than would occur with out this process (Feely et al., 2001; Khatiwala et al., 2009; Parekh et al., 2006). Particle cycling and export are also essential for the biogeochemical cycles of other major nutrients and chemical species of vital importance for marine biota, as well as anthropogenic metals and pollutans. The radiotracer pair 234Th: 238U as been commonly and extensively used to study particle export and determine the strength of the biological carbon pump in the upper ocean (Coale and Bruland, 1985; Le Moigne et al., 2013b). This thesis evaluates oceanic carbon export fluxes and the efficiency of the biologically mediated uptake of atmospheric CO2 using this naturally occurring radiotracer pair in a variety of regimes under contrasting biogeochemical conditions. First, basin-scale export variability was examined in the North Western Atlantic Ocean along a latitudinal transect (from 64ºN to the equator) with high spatial resolution, providing additional data in under sampled areas. The results agreed with previous studies carried out in the North Atlantic and were also compared with different satellite-derived export models. These models have a strong dependence on sea surface temperature and net primary productivity estimates, but they usually do not consider biological parameters that influence carbon export, such as the trophic structure, the grazing intensity, the recycling efficiency, the bacterial activity and the dissolved organic carbon export (Maiti et al., 2013). The differences observed between the satellite-derived and the 234Th-derived carbon export estimates highlights the necessity to include such biological parameters at a regional scale, for which continued observing efforts are needed. This would thereby reduce uncertainty in the global carbon budget and improve carbon cycle monitoring from satellite-based platforms. Second, the zonation of surface properties derived from the various fronts crossed along a 10ºE transect, from 44ºS to 53ºS, in the Antarctic Circumpolar Current were evaluated in relation to particle export. Our results show that, despite the contrasting food webs encountered north and south of the Antarctic Polar Front (~49ºS), the magnitude of the carbon export fluxes were similar along the transect. However, differences appeared when examining transfer efficiencies: in the northern section, which was dominated by nanophytoplankton, presented high export efficiencies and reduced transfer efficiencies in comparison to the southern section, dominated by microphytoplankton. Thus, and although different food web regimes led to similar export of carbon, the sinking particle pools differed in their composition north and south of the Antarctic Polar Front (aggregates of small particles in the north vs fast-sinking large particles in the south), resulting in two different scenarios regarding the amount of exported carbon that reached greater depths. Finally, estimates of particle flux and export efficiency were examined in a semi-enclosed basin (Gulf of California and the surrounding waters of the Eastern Tropical North Pacific), with a strong seasonality that leads to changes in the planktonic community. Export estimates were assessed using the 234Th approach in combination with surface-tethered sediment traps. Data on size fractionation and high vertical resolution of in situ pump deployments allowed a comparison of the C/234Th ratios attenuation with depth between small (1-53 μm) and large (>53 μm) particles. Results indicate that, under dominance of pico- and nanoplankton and with presence of diazotrophs, small particles play and important role in carbon export and that this export might be more efficient than that resulting from a diatom dominated planktonic community in the study area.

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21

Sandoval, Rojano Stefania. "Functionalization of carbon nanomaterials with nitrogen, halides and oxides." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/394000.

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Los materiales compuestos por grafeno y nanotubos de carbono (CNTs) han despertado un amplio interés debido a sus propiedades excepcionales. La variación de éstas, empleando diversas técnicas de modificación aumentan sus aplicaciones potenciales en muchos campos. Ésta tesis describe la funcionalización de nanomateriales de carbono con nitrógeno y diversos haluros y óxidos. La modificación de la estructura de nanotubos de carbono multicapa (MWCNTs) y derivados de grafeno se llevó a cabo mediante reacciones sólido-gas y sólido-líquido. Hemos empleado diferentes métodos de funcionalización, que incluyen oxidación, funcionalización con nitrógeno y dopaje, así como modificaciones de las cavidades internas y superficies externas de los nanotubos de carbono, para modular las propiedades de las nanoestructuras preparadas. Mediante un estudio sistemático de las condiciones de tratamiento y una exhaustiva caracterización se determinaron las características estructurales de las muestras y se evaluaron algunas de sus propiedades fisicoquímicas. En ésta tesis proponemos un método simple, eficiente y reproducible para la síntesis de óxido de grafeno reducido (RGO) modificado con nitrógeno. La naturaleza de los átomos de nitrógeno dentro de la red del RGO se ha modulado mediante tratamientos de amonolísis de óxido de grafeno (GO) a temperaturas comprendidas entre 25 ˚C y 800 ˚C. El protocolo propuesto permite tanto la introducción de grupos funcionales alifáticos (funcionalización con N) como la de nitrógeno estructural (dopaje con N). Adicionalmente, la composición estructural de las muestras funcionalizadas y dopadas con nitrógeno se modificó mediante tratamientos posteriores empleando altas temperaturas y atmosferas no oxidantes. Éstos tratamientos provocan rearreglos internos que confieren mayor estabilidad térmica a los materiales. Por otro lado, se llevó a cabo el llenado de las cavidades y la decoración de las superficies externas de los MWCNTs con compuestos inorgánicos. Reportamos la formación de nanotubos inorgánicos monocapa dentro de los nanotubos de carbon empleando una técnica de capilaridad del material laminar en su fase fundida. Además, mediante la optimización de los parámetros experimentales conseguimos favorecer el crecimiento de éstos sistemas inorgánicos monocapa con respecto la formación de otras nanoestructuras, tales como, nanopartículas, nanobarras y nanoserpientes de los halogenuros empleados. Hemos descrito una nueva técnica para el aislamiento ó liberación de las sustancias previamente introducidas en las cavidades de los MWCNTs. Así, exploramos el uso potencial de los fulerenos como agentes aisladores o promotores de la liberación de estructuras huéspedes. Finalmente, hemos preparado MWCNTs decorados con óxidos de titanio reducidos empleando tratamientos a altas temperaturas. Mediante la oxidación de los nanotubos se obtuvieron “nanocollares” de titania libres de carbono. Los materiales soportados presentan una actividad fotocatalítica superior a la del material de referencia titania P25.
Graphene and carbon nanotubes (CNTs) are of wide interest in materials science due to their outstanding properties. Several approaches allow modulating their properties further expanding their potential applications in many fields. This thesis reports on the functionalization of carbon nanomaterials with nitrogen, halides and oxides. The modification of the structure of multiwalled carbon nanotubes (MWCNTs) and graphene derivatives has been carried out through solid-gas and solid-liquid reactions. Different methods of functionalization, which include oxidation, nitrogen functionalization and doping, as well as endohedral and exohedral modifications have been employed for tuning the properties of the prepared nanostructures. A systematic study of the conditions of treatment and an extensive characterization has allowed the determination of the structural characteristics of the samples and the evaluation of some of their physical and chemical properties. In this thesis we propose a simple, efficient and reproducible method for the synthesis of nitrogen-containing reduced graphene oxide (RGO). The nature of the nitrogen atoms within the RGO lattice has been tuned by ammonolysis treatments of graphene oxide (GO) in the range of 25 ˚C-800 ˚C. The reported protocol allows the introduction of aliphatic moieties (N-functionalization) and structural nitrogen (N-doping). Additionally, the structural composition of the N-containing RGO has been modified by post-annealing the material under non-oxidizing atmospheres. High temperature treatments induce internal rearrangements, leading to samples with an enhanced thermal stability. On the other hand, endohedral and exohedral functionalization of MWCNTs with inorganic materials have been carried out. We report on the formation of single-layered inorganic nanotubes within the cavities of MWCNTs through a molten phase capillary wetting technique. We have optimized the conditions of the synthesis to enhance the growth of the single-layered nanotubes, while decreasing the formation of other nanostructures (nanoparticles, nanorods and nanosnakes). A new technique for the confinement and/or release of the filled substances within the hollow cavity of the CNTs has also been developed. We have explored the potential of fullerenes as corking agents and as promoting species for the release of guest structures. Finally, we have prepared MWCNTs decorated with reduced titanium oxides employing high temperature treatments. By oxidation of MWCNTs self-standing titania “nano-necklaces” are formed. The photocatalytic performance of the carbon supported materials overpasses that of the reference material titania P25.

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Tortajada, Navarro Andreu. "Nickel-Catalyzed Reductive Carboxylation and Amidation of Organic Matter." Doctoral thesis, Universitat Rovira i Virgili, 2020. http://hdl.handle.net/10803/670204.

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En els darrers anys, el desenvolupament de reaccions de carboxilació reductiva de (pseudo) halogenurs orgànics amb diòxid de carboni (CO") catalitzada per metalls per a la preparació d'àcids carboxílics s'ha convertit en una poderosa alternativa a l'ús d'èspecies organometàl·liques, en la majoria dels casos sensibles a l'aire. Tanmateix, l'ús d'alcohols simples no protegits o d'hidrocarburs insaturats en combinació amb CO" per obtenir àcids carboxílics mitjançant una reacció de formació d'un enllaç C-C han rebut molta menys atenció. Aquests representen una alternativa atractiva als halurs orgànics, ja que són abundants i fàcilment disponibles. En aquesta tesi doctoral es descriu la carboxilació selectiva d'alcohols al·lílics amb CO2, una metodologia capaç d'obtenir àcids carboxílics insaturats amb un control excel·lent de la selectivitat obtinguda.

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Martinez, Espinar Francisco. "NHC-stabilized Rh Nanoparticles as efficient catalysts for the hydrogenation of aromatics and selective H/D exchange in P-based ligands." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/450870.

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Aquesta tesis tracta sobre la síntesi i la caracterizació de nanopartícules de rodi i la seva aplicació en processos catalítics selectius. La síntesi de les nanopartícules de rodi es va realitzar en la presència de lligands carbens N-Heterocíclics, que van ser emprats com a agents estabilizadors. Tècniques de caracterizació como ara TEM, HRTEM, SEM, XRD, WAXS, TGA, IR i NMR en solució i en estat sòlid van ser utilizades per la completa caracterizació del catalizador final. Al que a l'aplicació en catàlisi respecta, aquestes nanoparícules de rodi van ser utilitzades en la hidrogenació selectiva de compostos aromàtics com ara cetones, fenols i piridines i en la deuteració selectiva de lligands basats en fòsfor. Aquests últims estudis van proporcionar informació sobre el mode de coordinació d'aquests lligands a la superfície metàl·lica de les nanopartícules.
Esta tesis trata sobre la síntesis y la caracterización de nanopartículas de rodio y su aplicación en procesos catalíticos selectivos. La síntesis de las nanopartículas de rodio se realizó en la presencia de ligandos carbenos N-Heterocíclicos, que fueron usados como agentes estabilizadores. Técnicas de caracterización como TEM, HRTEM, SEM, XRD, WAXS, TGA, IR y NMR en solución y en estado sólido fueron utilizadas para la completa caracterización del catalizador final. Respecto a la aplicación en catálisis, estas nanoparículas de rodio fueron usadas en la hidrogenación selectiva de compuestos aromáticos como cetonas, fenoles y piridinas y en la deuteración selectiva de ligandos basados en fósforo. Estos últimos estudios proporcionaron información sobre el modo de coordinación de estos ligandos en la superfície metálica de las nanopartículas.
Esta tesis trata sobre la síntesis y la caracterización de nanopartículas de rodio y su aplicación en procesos catalíticos selectivos. La síntesis de las nanopartículas de rodio se realizó en la presencia de ligandos carbenos N-Heterocíclicos, que fueron usados como agentes estabilizadores. Técnicas de caracterización como TEM, HRTEM, SEM, XRD, WAXS, TGA, IR y NMR en solución y en estado sólido fueron utilizadas para la completa caracterización del catalizador final. Respecto a la aplicación en catálisis, estas nanoparículas de rodio fueron usadas en la hidrogenación selectiva de compuestos aromáticos como cetonas, fenoles y piridinas y en la deuteración selectiva de ligandos basados en fósforo. Estos últimos estudios proporcionaron información sobre el modo de coordinación de estos ligandos en la superfície metálica de las nanopartículas.

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Mato, Gómez Mauro. "Streamlining the Access to Metal Carbenes through Aromative Decarbenations." Doctoral thesis, Universitat Rovira i Virgili, 2021. http://hdl.handle.net/10803/672265.

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Els carbens metál·lics son una classe fonamental d'intermedis organometál·lics que mostren patrons de reactivitat únics. Degut a les limitacions que presenten la majoria deis precursors deis carbens metál·lics establerts, proposem l'ús de precursors de carbens basats en el concepte de la descarbenació aromativa o la reacció de retro-Buchner. En presencia de complexes cationics d'or(I), cicloheptatriens 7-substituits participen en una reacció de descarbenació o reacció de retro-Buchner, generan! carbens d'or(I) després d'alliberar una molécula de benze. Hem estés aquest concepte per al desenvolupament de nous precursors de carbens basat en el despreniment de diferents molecules aromátiques o poliaromátiques, mitjan9ant catálisis de diferents metalls a banda de l'or.
Los carbenos metálicos son una clase fundamental de intermedios organometálicos que muestran patrones de reactividad únicos. Debido a las limitaciones que presentan la mayoría de los precursores de carbenos, proponemos el uso de precursores basados en el concepto de descarbenación aromativa, o reacción de retro-Buchner. En presencia de complejos catiónicos de oro(I), los cicloheptatrienos 7-substituídos participan en un proceso de descarbenación (o reacción de retro-Buchner) en el que se genera un carbeno tras la liberación de una molécula de benceno. Hemos extendido este concepto para el diseño de nuevos precursores de carbenos, basados en la liberación de diferentes moléculas aromáticas o poliaromáticas
Metal carbenes are a fundamental type of organometallic intermediates which display very unique reactivity patterns. Due to the limitations presented by most of the stablished metal-carbene precursors, we propose the use of alternative carbene sources based on the concept of aromative decarbenation, or retro-Buchner reaction. In the presence of cationic gold(I) complexes, 7-subtituted cycloheptatrienes can undergo a decarbenation or retro-Buchner reaction, generating gold(I) carbenes upon release of a molecule of benzene. We have extended this concept for the development of new and more reactive carbene precursors, based on the release of different aromatic or polyaromatic molecules, through catalysis of metals other than gold.

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Brun, Massó Sandra. "Metalls de transició en la formació d'enllaços carboni-carboni: cicloaddicions [2+2+2] catalitzades per Rh(I) i acoblaments creuats catalitzats per Pd(0) i Ni(0)." Doctoral thesis, Universitat de Girona, 2012. http://hdl.handle.net/10803/81713.

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Carbon-carbon bond formation reactions catalyzed by transition metals represent one of the most versatile and efficient strategies in organic synthesis. The catalytic transformations contribute to the development of methodologies that are more environmentally benign and with high atomic economy. Despite the progress in this field in recent years, the development of new and more efficient strategies of synthesis continues to be one of the main challenges of organic chemistry. In the present PhD thesis the Rh(I)-catalyzed [2+2+2] cycloaddition reaction of different macrocyclic and acyclic substrates containing double and/or triple bond in their structure are studied. On the other hand, Matsuda-Heck reactions and Suzuki-Miyaura cross-couplings using diazonium salts as electrophiles under Pd(II) catalysis with mild reaction conditions and a totally aqueous medium have been studied. Palladium-catalyzed carbon-carbon bonds a good alternative both in terms of cost and activity is the use of nickel catalysts. Finally, new Ni(0) complexes with macrocyclic and open-chain ligands containing double and triple bonds have been synthesized and completely characterized. Their activity in Suzuki cross-coupling reactions is then studied.
Les reaccions de formació d’enllaços carboni-carboni catalitzades per metalls de transició representen una de les estratègies més versàtils i eficients en síntesi orgànica. Les transformacions catalítiques contribueixen al desenvolupament de metodologies més benignes amb el mediambient i proporcionen una elevada economia atòmica. Encara que siguin molts els avenços fets en aquest camp en els últims anys, el desenvolupament de noves i més eficients estratègies de síntesi segueixen essent un dels reptes principals de la química orgànica. En la present tesi s'ha estudiat la reacció de cicloaddició [2+2+2] catalitzada per Rh(I) de diferents substrats macrocíclics i acíclics contenint dobles i/o triples enllaços. Per altra banda, s’han portat a terme reaccions de Matsuda-Heck i acoblaments creuats de Suzuki-Miyaura utilitzant sals de diazoni com a electròfils sota catàlisi per Pd(II) emprant condicions suaus de reacció i en medi totalment aquós. Una bona alternativa al pal•ladi en termes econòmics i d’activitat és l’ús de catalitzadors de níquel. Finalment s’han sintetitzat i caracteritzat estructuralment nous complexos de Ni(0) amb lligands macrocíclics i de cadena oberta contenint diferents insaturacions i s'ha estudiat la seva activitat catalítica en reaccions de Suzuki.

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Oliveira, Junior Myriano Henriques de. "Propriedades ópticas, mecânicas e estruturais de filmes de carbono amorfo." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277831.

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Orientador: Francisco das Chagas Marques
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Neste trabalho desenvolvemos um sistema de deposição de filmes finos pela técnica de arco catódico filtrado (FCVA- Filtered Cathodic Vacuum Arc), que possibilita o desenvolvimento de ligas metálicas e, sobretudo, a deposição de filmes de carbono amorfo altamente tetraédrico. Utilizando este sistema desenvolvemos filmes de carbono amorfo (a-C) com elevada dureza (estimado em cerca de 50 a 60GPa) e alta concentração de ligações sp3 C-C em função da polarização do substrato. Estudamos as propriedades ópticas, mecânicas (stress e dureza), estruturais (Raman e RBS) e a estabilidade térmica (efusão de gases) destes filmes em função da energia de deposição. Também desenvolvemos e caracterizamos filmes de carbono crescidos por FCVA assistido por um feixe de íons secundário de Ar e Kr com diferentes energias, onde analisamos os efeitos da energia deste feixe sobre as propriedades físicas do material resultante. Além das estruturas de carbono intrínseco realizamos um estudo sobre filmes de carbono amorfo hidrogenado depositados por PECVD (plasma enhanced chemical vapor deposition) com diferentes tensões de bias (de 60 à 550V) e atmosferas mistas de CH4/Kr, onde variamos a pressão parcial deste gás nobre entre 0 e 50%. Estudamos a influência deste gás nobre sobre as propriedades estruturais do material assim como a forma como os átomos deste elemento se distribuem dentro da rede amorfa. Esta última análise foi baseada em estudos conduzidos a partir da absorção de raios-x na borda K do átomo de criptônio, onde verificamos a aglomeração destes átomos na forma de estruturas solidas. Também investigamos os processos de transformações estruturais ocorridas em estruturas a-C:H e ta-C com a temperatura baseadas na efusão de gases. Para este estudo construímos um sistema que funciona em ultra-alto vácuo, com temperatura controlada variando de ambiente até cerca de 1000 graus. Os estudos sobre as propriedades estruturais foram baseados, sobretudo, em medidas de espectroscopia de espalhamento Raman com radiação de excitação na região do visível e do ultravioleta, o que possibilita a obtenção de informações mais detalhadas sobre a forma como os átomos sp2 e sp3 distribuem-se no material. Por fim, exploramos o potencial de aplicação de três tipos de carbono amorfo; tipo polimérico (PLC), tipo diamante (DLC) e tetraédrico (ta-C) como monocamadas antirefletoras para células solares de silício cristalino e comparamos com o desempenho obtido com camadas fabricadas com materiais usualmente empregados na indústria para tal aplicação. Os resultados mostraram que filmes de carbono amorfo podem ser utilizados como camada anti-refletora. Os filmes de carbono tipo polimérico apresentaram resultados muito semelhantes aos obtidos com camadas convencionais de dióxido de estanho
Abstract: In this work we designed, manufactured and characterized a Filtered Cathodic Vacuum Arc (FCVA) deposition system. This technique is usually applied in the preparation of metallic alloys and highly sp3 - hybridized amorphous carbon thin films. By using this system we prepared a series of amorphous carbon films (a-C) with high hardness (up to ~60GPa) and high concentration of sp3 C-C bonds varying the deposition energy of the C+ ions. Mechanical (hardness and intrinsic stress) and structural (Raman, RBS and gas effusion) were investigated. Another series of a-C was developed by FCVA, but using an assisted beam of Ar or Kr as a function of the ion energy. The main purpose of this work is to understand of the effects of the bombardment of an energetic ion beam on the physical properties of the films. Another study performed on hydrogenated amorphous carbon films (a-C:H) were carried out on samples deposited by plasma enhanced chemical vapor deposition (PECVD). The films were prepared with different self-bias, varying from 60 up to 550V, and different mixed atmospheres of methane and krypton gases, varying the partial pressure of krypton from 0 to 50%. Films prepared at low bias are polymeric-like (PLC), while films prepared at high bias are diamond-like (DLC). We had performed investigations on the influence of this noble gas on the structural properties of the a-C:H films and how the Kr atoms are arranged within the amorphous matrix. The distribution of Kr atoms was studied mainly by x-ray absorption on the krypton absorption K-edge. Due to the absence of EXAFS oscillations the spectra were interpreted using the XANES region, which gave us evidences of clustering of Kr atoms. The processes involved in the a-C:H nd ta-C structural transformations during the thermal annealing were analyzed by means of thermal gas effusion measurements (using a quadrupole spectrometer) in a system developed in our laboratory. Raman scattering spectroscopy measurements were carried out with excitation radiation in the visible and ultraviolet ranges. This choice is justified due to the more detailed information obtained by multiwavelength Raman spectroscopy on the distribution of sp2and sp3sites within the amorphous carbon matrix. Finally, we had evaluated the possibility of the application of three types of amorphous carbon structures, the diamond-like and polymeric-like carbon, and the ta-C as antireflective coating on crystalline silicon solar cells. We observed that all amorphous carbon structures (DLC, PLC and ta-C) increase the short-circuit current of the solar cells. In the case of PLC films, the result is comparable to that obtained with conventional antireflective coating such as tin dioxide (SnO2)
Doutorado
Física da Matéria Condensada
Doutor em Ciências

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Nepel, Thayane Carpanedo de Morais. "Efeitos da temperatura e da concentração de CO e CO2 sobre a eletrocatálise da oxidação de hidrogênio em eletrodos à base de Pt e Mo." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-17042012-171421/.

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Um dos grandes desafios a ser vencido para a utilização em larga escala das células a combustível de eletrólito polimérico alimentada com H2 obtido por reforma é a contaminação da superfície do eletrocatalisador de Pt, usualmente utilizado no ânodo,pelos gases CO e CO2 presentes no combustível. Neste trabalho é apresentado o estudo dos mecanismos de tolerância de materiais formados por Pt e Mo (Pt/C, Pt3Mo2/C e Pt1Mo1/C) aos contaminadores CO e CO2 e a influência da temperatura nesses processos. Os estudos foram realizados por meio de curvas de polarização com medidas de espectrometria de massas (EM) on line, experimentos de EM em circuito aberto e voltametria linear de remoção de CO adsorvido no catalisador em diferentes temperaturas. Para os catalisadores Pt/C e Pt3 Mo2 /C os resultados mostraram um aumento em 10 vezes na tolerância ao CO quando a temperatura de operação da célula é elevada em 20°C (de 85°C a 105°C) e uma tolerância significativamente superior do Pt3Mo2/C em relação à Pt/C. A ocorrência do mecanismo bifuncional, do mecanismo Eley-Rideal e da reação de Troca Gás-Água (do inglês Water Gas Shift - WGS) foi confirmada apenas para PtMo/C; porém, a diminuição do sobrepotencial de oxidação do CO com o aumento da temperatura foi notada para ambos os catalisadores. A reação de WGS é acelerada com a elevação da temperatura, confirmando que a cinética é a determinante da reação.Também foi realizada a quantificação do cruzamento do O2 do cátodo para o ânodo, sua participação na eliminação do CO e a influência da temperatura nesse processo. Observou-se que a oxidação parcial do CO pelo O2 efetivamente ocorre, aumenta com a temperatura, porém pouco contribui no processo global de tolerância dos catalisadores Pt/C e PtMo/C. Em relação ao contaminante CO3, confirmou-se a ocorrência da reação RWGS (WGS reversa) para ambos os catalisadores, assim como a reação RWGS eletroquímica. Em termos de desempenho de célula,excelentes resultados foram obtidos com a mesma operando a 105°C - para Pt3Mo2/C e utilizando uma mistura de H2/CO(75 ppm)/CO2(25%), observando-se sobrepotencial anódico de apenas 40 mV em relação ao hidrogênio puro em densidade de corrente de 1 Acm-2.
One of the biggest challenges to be overcome for the widespread use of polymer electrolye fuel cellsfueled with H2 obtained by reform is the surface contamination of the Pt electrocatalyst, usually used in the anode, by CO and CO2 present in the fuel stream. This work presents a study of the tolerance mechanisms of CO and CO2 contaminants on electrode materials formed by Pt and Mo (Pt /C, Pt3Mo2 /C, and Pt1Mo1/C) and the influence of temperature on these processes. The studies were performed using polarization curves with on line mass spectrometry measurements (MS), MS experiments at open circuit, and linear sweep CO stripping at different temperatures. For Pt/C and Pt3Mo2/C catalysts, results showed a 10 fold increase in the CO tolerance when the fuel cell operating temperature is raised by 20°C (85°C to 105°C) and a significantly higher tolerance of Pt3Mo2/C compared to Pt/C. The occurrence of the so called bifunctional mechanism, Eley-Rideal mecanism and the Water Gas Shift (WGS) reaction was confirmed only for PtMo/C, but the decrease in the CO oxidation overpotential with the increase of temperature was noted for both catalysts. Also a quantification of O2 crossover from the cathode to the anode was carried out, together with an evaluation of its participation in the elimination of CO and the characterization of influence of temperature in this process. It was observed that the partial oxidation of CO by O2 does occur, increases with temperature, but it has little effect in the overall tolerance of Pt/C and PtMo/Ccatalysts. The WGS reaction is accelerated by increasing the temperature, confirming that the kinetics of the reaction is rate determinant. Regarding CO2 contaminant, the occurrence of the RWGS reaction (reverse WGS) and the electrochemical RWGS were confirmed for both catalysts. In terms of cell performance, excellent results were obtained with the cell operating at 105°C for Pt3Mo2/C and using a mixture of H2/CO (75 ppm)/CO2 (25%), observing an anodic overpotential of only 40 mVcompared to pure hydrogen was observed at a current density of 1 Acm-2.

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Fenner, Bruna Rossi. "Desenvolvimento de espumas de poliuretano revestidas com formas alotrópicas de carbono para utilização como sorvente de petróleo e outras substâncias orgânicas." reponame:Repositório Institucional da UCS, 2017. https://repositorio.ucs.br/handle/11338/3384.

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Casas, Ruiz Joan Pere. "Controls on the dynamics of riverine dissolved organic matter: insights from a Mediterranean river network." Doctoral thesis, Universitat de Girona, 2017. http://hdl.handle.net/10803/404280.

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In river networks, dissolved organic matter (DOM) constitutes the major pool of organic carbon, and plays a key role as energy source and modulator of toxic substances availability. In this thesis, Joan P. Casas-Ruiz and collaborators provide new insights into the controls on DOM processing, and into how in-stream reactions and changing DOM sources modulate DOM dynamics in river networks. To attain this, the quantity and composition of DOM were evaluated across a river network throughout a full hydrological year. The results compiled in this thesis pose water residence time as the main regulator of DOM processing, while DOM properties as well as nutrient availability determine the net balance of in-stream degradation and production of DOM. A network-scale analysis identifies a pattern of DOM concentration and chemical diversity with maxima in medium-sized rivers, and the same pattern emerges upon analysis of a global data set. On the basis of these results, this thesis proposes a conceptual framework to comprehend and predict the spatiotemporal dynamics of riverine DOM
La matèria orgànica dissolta (DOM) constitueix la major reserva de carboni orgànic en els sistemes fluvials, on també hi juga un paper clau com a font d'energia i modulador de la disponibilitat de substàncies tòxiques. En aquesta tesi, Joan P. Cases-Ruiz i col•laboradors pretenen identificar els controls de processament DOM, i entendre com la combinació de reaccions in situ i canvis en les fonts de DOM modulen les dinàmiques de la DOM fluvial. Per tal d'assolir-ho, es van evaluar la quantitat i composició de la DOM en una xarxa fluvial al llarg d'un any hidrològic complet. Els resultats recopilats en aquesta tesi assenyalen el temps de residència de l'aigua com el principal regulador de processament de la DOM, mentre que les propietats intrínsiques de la DOM, així com la disponibilitat de nutrients determinen el balanç net de degradació i producció de la DOM. Una anàlisi a escala de xarxa fluvial identifica un patró de concentració i diversitat química de la DOM amb màxims en els rius de mida mitjana. En base a aquests resultats, aquesta tesi proposa un marc conceptual per comprendre i predir les dinàmiques espacials i temporals de la DOM fluvial

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Brender, Patrice. "Etude de l'influence de la température sur les réactions tribochimiques des matériaux carbonés : Application au freinage aéronautique de composites Carbone/Carbone." Thesis, Mulhouse, 2012. http://www.theses.fr/2012MULH5872.

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L’objectif de ce travail est d’étudier quantitativement l’évolution des propriétés de surface des matériaux carbonés et leur réactivité dans les conditions proches de celles rencontrées lors du taxiage des avions. Les essais de freinage ont été réalisés à l’aide d’un Banc d’Essai Tribométrique à Simulation Inertielle. Les composites C/C frottés et les débris d’usure sont caractérisés par des techniques non-conventionnelles multi-échelles. Les composites frottés (dans leur totalité) et les débris d’usure sont caractérisés par thermo-désorption programmée et chimisorption d’oxygène. Ces analyses permettent de déterminer la nature et la quantité de groupes fonctionnels et la teneur en sites actifs, caractéristique de la réactivité intrinsèque du carbone et responsable de l’interaction avec les espèces gazeuses de l’environnement. Ces caractérisations sont complétées par des analyses morphologiques, structurales et texturales par microscopies, diffractions des rayons X, adsorption de gaz. L’analyse des caractéristiques physico-chimiques des débris d’usure et des disques frottés permet de remonter aux réactions tribochimiques ayant eu lieu dans le contact : des réactions chimiques entre l’oxygène ou l’eau et les liaisons C-C rompues ont été mises en évidence. Un modèle permettant de justifier les différences de propriétés tribologiques lors des essais de taxiage a été proposé. Ce modèle, basé sur la réactivité du système et sur les propriétés de l’interface de frottement, permet d’élucider les problématiques liées à la température dans ce type de système
The objective of this work is to study quantitatively the evolution of carbon materials surface properties and reactivity under breaking conditions similar to those encountered during taxiing. The breaking tests were carried out using a Tribometric Test Bench. The rubbed C/C composites and the wear debris collected are then characterized by mutiscale unconventional techniques. The whole rubbed composites and the wear debris are characterized by Temperature-Programmed Desorption and by oxygen chemisorption. These analyzes are used to determine the nature and amount of functional groups and the content of active sites that is characteristic of the reactivity of the carbon material and also responsible of its interaction with the surrounding environment. The characterizations are completed by morphological, structural and textural analysis, such as Electron Microscopy, X-Ray Diffraction and gas adsorption. The analysis of the physic-chemical characteristics of wear debris and of the rubbed discs enables to evidence the tribochemical reactions occurring in the mechanical contact: chemical reactions between oxygen or water and the broken C-C bonds have been evidenced. A model is finally proposed, justifying the differences in the tribological properties during taxiing tests. The later is based on the carbon reactivity and on the interface properties and justify the temperature dependence of this system

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Hippolyte, Laura. "New syntheses of N-heterocyclic carbene-stabilized gold nanoparticles." Electronic Thesis or Diss., Sorbonne université, 2018. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2018SORUS148.pdf.

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Récemment, les carbènes N-hétérocycliques (NHC) ont suscité un intérêt important dans le domaine de la chimie des matériaux. En effet, cette nouvelle catégorie de ligands forme des liaisons très fortes avec une diversité de métaux et leur structure, ainsi que leurs propriétés électroniques, peuvent être adaptées par de la synthèse organique. Cette forte liaison est d’un intérêt particulier dans le domaine des nanoparticules d’or (NP) et des synthèses ont déjà été proposées. En effet, les NPs présentent de nombreuses applications potentielles, par exemple dans les capteurs, en catalyse ou médecine, mais ces applications sont parfois freinées par un manque de stabilité du ligand de surface. Ce travail de thèse s’est concentré sur le développement de nouvelles synthèses de nanoparticules d’or stabilisées par des NHC. D’abord, en revisitant une procédure existante à base de sels d’imidazoliums, ce qui a mené à une synthèse n’utilisant que les composés commerciaux : AuCl et NaBH4 et des halogénures d’imidazolium, facilement obtenus. Une synthèse totalement nouvelle a ensuite été développée en utilisant des NHC-boranes qui sont des adduits de Lewis stables. Nous avons montré pour la première fois que les NHC-boranes peuvent être utilisés comme réactifs "2-en-1" dans la synthèse de NP : comme réducteurs du précurseur d’or et comme source de NHC. Enfin, nous sommes les premiers à décrire la synthèse de NP stabilisées par des carbènes mésoioniques (MIC).Les MICs sont une sous-catégorie des NHCs qui sont préparés par « chimie click » et qui présentent des propriétés électroniques uniques. Un intérêt particulier a été porté à la caractérisation des nanoparticules, notamment par XPS
Over the past decade, N-heterocyclic carbenes (NHC) have drawn considerable interest in the field of materials chemistry. Indeed, this relatively new class of ligands forms strong bonds with a wide range of metals and their structures and electronic properties can be tuned “at-will” through organic synthesis. This strong bond is of particular interest for gold nanoparticles. Indeed, gold nanoparticles have many potential applications, for example in sensors, catalysis or medicine, but those potential applications are sometimes hindered by a lack of stability of the surface ligand. A few syntheses of NHC-stabilized gold nanoparticles have already been described in the literature but each presents their own set of drawbacks. This thesis work has focused on the development of new syntheses of NHC-stabilized gold nanoparticles. First, by revisiting a literature procedure starting from imidazolium salts, we managed to develop a one-pot synthesis starting only from commercially available AuCl, NaBH4 and easily synthesized imidazolium salts. A totally new synthesis was developed using NHC-boranes, which are stable Lewis adducts. Here, we reported for the first time their use as a 2-in-1 reagent, able to reduce the metallic precursor and provide the nanoparticles stabilizing ligands. Finally, we are the first to report a synthesis of gold nanoparticles stabilized by mesoionic carbenes (MIC). MICs are a sub-class of NHCs synthesized by well-known “click-chemistry”, which present unique electronic properties. Throughout this work, special care was taken to characterize the nanoparticles, notably by XPS

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Kierkowicz, Magdalena. "Development of carbon nanocapsules for biomedical applications." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/458543.

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La alta superficie y el hueco interior de los nanotubos de carbono (del inglés CNTs) los convierte en candidatos ideales para el desarrollo de nanovectores inteligentes para su aplicación en nanomedicina. Su cavidad interna puede emplearse para alojar compuestos seleccionados para propósitos de diagnóstico o terapéuticos, mientras que las paredes externas pueden modificarse para aumentar su biocompatibilidad e incluso para su direccionamiento. Un reto importante para trasladar los sistemas basados en CNT a su uso clínico es la reducción o eliminación de su toxicidad. Teniendo en cuenta la preocupación sobre salud y seguridad de nanomateriales, se han intensificado los esfuerzos de investigación para mejorar la biocompatibilidad de los CNTs, incluyendo el desarrollo de nuevas estrategias para el acortamiento y purificación de los mismos. La primera parte de esta tesis se enfoca en el estudio de la influencia del vapor de agua sobre la longitud, pureza y la integridad de las paredes de los nanotubos de carbono monocapa (del inglés SWCNTs) producidos tanto por deposición catalítica en fase de vapor (del inglés CVD ) como por descarga de arco. Para obtener nanotubos de carbono individualizados desarrollamos un protocolo que consiste en dispersar las muestras en orto-diclorobenceno y hemos empleado microscopía electrónica de barrido para adquirir las imágenes. CVD CNTs cortos con una longitud media de aprox. 200 nm se obtienen después de 10 h de tratamiento con vapor de agua, mientras que los CNT sintetizados por descarga de arco muestran una baja reactividad frente el vapor de agua. También se investigó la eficiencia de otros métodos de acortamiento comúnmente empleados, como son la molienda de bolas, una mezcla de ácido sulfúrico/nítrico y el tratamiento con piraña, tanto para SWCNTs como para CNTs multicapa (del inglés MWCNT) producidos por CVD. La combinación de piraña y vapor de agua resultó ser la más eficiente para el acortamiento de SWCNTs, y la combinación de ácido sulfúrico/nítrico con vapor de agua para MWCNTs. Estos protocolos proporcionan un buen equilibrio entre la obtención de nanotubos cortos con una distribución de longitud pequeña y la pureza de las muestras con un alto rendimiento de producción. En la segunda parte, estudiamos la encapsulación de distintos haluros metálicos, de interés tanto para imagen como para terapia, dentro de SWCNTs preparados por CVD y por descarga de arco. Se ha investigado el papel que juega la temperatura de calientamiento en el grado de cierre de las puntas de los nanotubos de carbono. Este estudio ha permitido la preparación de CNTs llenos con haluros metálicos de forma eficiente. El llenado de nanotubos de carbono da lugar a muestras que contienen una gran cantidad de material no encapsulado, externo a los nanotubos de carbono, que puede afectar e incluso dominar las propiedades de los nanotubos de carbono llenos. Por lo tanto, desarrollamos un protocolo que permite la eliminación de compuestos no encapsulados en poco tiempo y respetuoso con el medio ambiente, utilizando agua como solvente "verde" en un sistema Soxhlet, a la vez que se minimiza la cantidad de agua residual. La última parte de la tesis describe la modificación de las paredes externas de CNTs llenos. SWCNTs se han funcionalizado covalentemente a través de las reacciones de Tour y Prato, la primera resultando en un grado de funcionalización mayor. Para completar el estudio, las paredes externas de MWCNT llenos con cloruro de lutecio fueron decoradas con nanopartículas de oro. Estas nanocápsulas híbridas tienen interés para su uso como agentes duales para el diagnóstico y la terapia. En resumen, esta tesis aporta nuevos conocimientos sobre la preparación de nanocápsulas de carbono, para el desarrollo de la siguiente generación de agentes teranósticos.
The high surface area and hollow core of carbon nanotubes (CNTs) make them ideal candidates for the development of smart nanovectors in nanomedicine. Their inner cavity can be employed to host selected payloads for either diagnosis or therapeutic purposes while the external walls can be modified to increase their biocompatibility and even for targeting purposes. A major challenge to turn the potential of CNT based devices into customer applications is to reduce or eliminate their toxicity. Taking into account health and safety concerns, intensified research efforts are conducted to improve the biocompatibility of CNTs, including the development of new shortening and purification strategies. The first part of this thesis focused on the influence of steam on the length, purity, and sidewall integrity of chemical vapor deposition (CVD) and arc discharge single-walled carbon nanotubes (SWCNTs). In order to obtain individualized carbon nanotubes we developed a protocol that consisted of dispersing the samples in ortho-dichlorobenzene and employed scanning electron microscopy (SEM) to acquire the images. Short CVD CNTs with median length of ca. 200 nm can be obtained after 10 h of steam treatment, whereas arc discharged CNTs show low reactivity towards steam. The efficiency of other commonly employed shortening methods, namely ball milling, sulfuric/nitric acids, and piranha was also investigated for both SWCNT and multi-walled CNTs (MWCNTs) grown by CVD. A combination of piranha and steam turned out to be the most efficient for SWCNTs, and a combined sulfuric/nitric acids and steam for MWCNTs. These protocols provide a good balance between length distribution, sidewall integrity and purity of samples with a high yield of production. In the second part, we report on the encapsulation of selected metal halides, of interest for both imaging and therapy, inside CVD and arc discharge SWCNTs. The role of temperature on the degree of end-closing has been investigated, which has allowed the preparation of closed-ended metal halide filled CNTs. Bulk filling of carbon nanotubes results in samples that contain a large amount of non-encapsulated material, external to the carbon nanotubes, which can affect and even dominate the properties of filled carbon nanotubes. Therefore, we developed a straight forward approach that allows the removal of non-encapsulated compounds in a time efficient and environmentally friendly manner, using water as a “green” solvent in a Soxhlet setup, while minimizing the residual waste. The last part of the thesis describes the external modification of previously filled CNTs. SWCNTs have been covalently functionalized via Tour and Prato reactions, the former resulting in a higher degree of functionalization. To complete the study, lutetium chloride filled MWCNTs were externally decorated with gold nanoparticles. The developed hybrid nanocapsules hold potential to be employed as dual agents for diagnosis and therapy. To summarize, this thesis brings new insights in the preparation of carbon nanocapsules, i.e. close-ended filled carbon nanotubes with chosen payloads, for the development of the next generation of theranostic agents.

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Vázquez, Cisneros Irais Argelia. "Análisis regional sistémico para evaluar el impacto ambiental y las implicaciones en la política de cambio climático. El caso de estudio de Puebla, México." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/673371.

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A nivell mundial la generació d'energia és la principal causa antropogènica d'emissions de gasos d'efecte hivernacle (GEH), la qual en la seva majoria segueix depenent dels combustibles fòssils. Al 2018, el 30% de les emissions de CO2 a nivell mundial van ser causades per l'ús de carbó per a la generació d'electricitat (IEA, 2019). En el cas de Mèxic i els seus estats aquesta situació no és diferent, ja que la generació d'energia, principalment elèctrica, és la major causant de GEH. Sota aquest context resulta ineludible la quantificació i enteniment de la petjada de carboni causada pel consum elèctric tant a nivell nacional com regional (estats, municipis o ciutats). La importància de quantificar la petjada de carboni a nivell regional rau en la necessitat que els estats, municipis i ciutats han de sumar a la comptabilitat nacional d'emissions, per al compliment de les metes nacionals i compromisos internacionals adquirits per Mèxic a l'ratificar l'Acord de París (SEMARNAT, 2019). Mentre que la rellevància d'analitzar la composició d'aquesta petjada de carboni rau en comprendre l'origen de les emissions amb la finalitat de buscar accions de mitigació a la mida de cada regió i per a cada un dels seus sectors econòmics. No obstant això, no només la comptabilitat de la petjada de carboni és rellevant a l'hora de pretendre comprendre els impactes ambientals causats per les activitats econòmiques d'un país o regió, també és primordial quantificar i entendre el flux de materials i indicadors derivats d'aquesta quantificació, ja que els indicadors intensius i extensius de el flux de materials poden servir com una mesura de la pressió que l'economia exerceix en el medi ambient a l'explotar els recursos naturals i com una font potencial de contaminants a l'aire, aigua i sòl. Aquesta tesi doctoral està estructurada al voltant de tres capítols medul·lars, 5, 6 i 7. En cada un d'aquests capítols es discuteix i presenten els resultats obtinguts de l'anàlisi quantitativa derivat de l'aplicació de tres metodologies; i) anàlisi econòmica de cicle de vida amb taules input-producte, ii) anàlisi de descomposició estructural amb taules input-producte i iii) comptabilitat i anàlisi de flux de materials, tots aquests aplicats a el cas d'estudi de l'estat de Pobla a Mèxic. Tant el capítol 5 com el 6, es desenvolupen al voltant de l'anàlisi de la petjada de carboni causada pel consum d'electricitat dels vuitanta sectors industrials i comercials de l'econòmica mexicana, reportats en la matriu input-producte de la base de dades de Eora, per a l'any 2013. per al capítol 5, es va calcular el consum elèctric necessari per satisfer la demanda intermèdia i demanda final de l'economia mexicana, amb l'ús de l'factor d'emissions elèctric nacional es va calcular la petjada de carboni per a cada un els vuitanta sectors abans esmentats. El capítol 6 es presenten els resultats de l'anàlisi de descomposició estructural. Aquesta anàlisi va tenir com a objectiu identificar el nivell d'influència que van tenir les fluctuacions en la demanda final i els canvis tecnològics en la variació de la producció final de cada un dels vuitanta sectors estudiats, tant a Mèxic com a Pobla, comparant l'any 2008 amb el 2013. En el capítol 7 s'ofereix la prospectiva de el metabolisme comunitari, usant la metodologia de comptabilitat de fluxos de materials, amb la qual s'han obtingut indicadors intensius i extensius de l'ús de materials per part de l'economia mexicana i poblana durant el 2004 fins al 2017 . Aquests indicadors permeten determinar els perfils metabòlics de l'economia de Mèxic (país) i de Pobla (estat).
A nivel mundial la generación de energía es la principal causa antropogénica de emisiones de gases de efecto invernadero (GEI), la cual en su mayoría sigue dependiendo de los combustibles fósiles. En el 2018, el 30% de las emisiones de CO2 a nivel mundial fueron causadas por el uso de carbón para la generación de electricidad (IEA, 2019). En el caso de México y sus estados esta situación no es distinta, pues la generación de energía, principalmente eléctrica, es la mayor causante de GEI. Bajo este contexto resulta ineludible la cuantificación y entendimiento de la huella de carbono causada por el consumo eléctrico tanto a nivel nacional como regional (estados, municipios o ciudades). La importancia de cuantificar la huella de carbono a nivel regional radica en la necesidad de que los estados, municipios y ciudades deben sumar a la contabilidad nacional de emisiones, para el cumplimiento de las metas nacionales y compromisos internacionales adquiridos por México al ratificar el Acuerdo de París (SEMARNAT, 2019). Mientras que la relevancia de analizar la composición de dicha huella de carbono radica en comprender el origen de las emisiones con la finalidad de buscar acciones de mitigación a la medida de cada región y para cada uno de sus sectores económicos. Sin embargo, no sólo la contabilidad de la huella de carbono es relevante al momento de pretender comprender los impactos ambientales causados por las actividades económicas de un país o región, también es primordial cuantificar y entender el flujo de materiales e indicadores derivados de dicha cuantificación, pues los indicadores intensivos y extensivos del flujo de materiales pueden servir como una medida de la presión que la economía ejerce en el medio ambiente al explotar los recursos naturales y como una fuente potencial de contaminantes al aire, agua y suelo. Esta tesis doctoral está estructurada alrededor de tres capítulos medulares, 5, 6 y 7. En cada uno de estos capítulos se discute y presentan los resultados obtenidos del análisis cuantitativo derivado de la aplicación de tres metodologías; i) análisis económico de ciclo de vida con tablas insumo-producto, ii) análisis de descomposición estructural con tablas insumo-producto y iii) contabilidad y análisis de flujo de materiales, todos estos aplicados al caso de estudio del estado de Puebla en México. Tanto el capítulo 5 como el 6, se desarrollan en torno al análisis de la huella de carbono causada por el consumo de electricidad de los ochenta sectores industriales y comerciales de la económica mexicana, reportados en la matriz insumo-producto de la base de datos de EORA, para el año 2013. Para el capítulo 5, se calculó el consumo eléctrico necesario para satisfacer la demanda intermedia y demanda final de la economía mexicana, con el uso del factor de emisiones eléctrico nacional se calculó la huella de carbono para cada uno de los ochenta sectores antes mencionados. El capítulo 6 presentan los resultados del análisis de descomposición estructural. Este análisis tuvo como objetivo identificar el nivel de influencia que tuvieron las fluctuaciones en la demanda final y los cambios tecnológicos en la variación de la producción final de cada uno de los ochenta sectores estudiados, tanto en México como en Puebla, comparando el año 2008 con el 2013. En el capítulo 7 se ofrece la prospectiva del metabolismo comunitario, usando la metodología de contabilidad de flujos de materiales, con la cual se han obtenido indicadores intensivos y extensivos del uso de materiales por parte de la economía mexicana y poblana durante el 2004 hasta el 2017. Dichos indicadores permiten determinar los perfiles metabólicos de la economía de México (país) y de Puebla (estado).
Power generation is the main anthropogenic cause of greenhouse gas (GHG) emissions around the world, which mostly continues to depend on fossil fuels. In 2018 coal-fired electricity generation accounted for 30% of global CO2 emissions (IEA, 2019). This situation is not different in the case of Mexico and its states, since the generation of energy, mainly electric, is the primary cause of greenhouse gas emissions. In this context, it is inexorable to quantify and understand the carbon footprint caused by electric usage from both the national and regional levels (states, municipalities, or cities). The importance of quantifying the carbon footprint at a regional level lies in the need for states, municipalities, and cities to add up to the national emissions accounting to comply with the national goals and international commitments acquired by Mexico through the Paris Agreement. The relevance of analyzing the carbon footprint’s composition lies in understanding the origin of emissions to seek mitigating actions tailored for each region and each of its economic sectors. In response to these two needs, this thesis uses the economic life cycle analysis to quantify the electrical carbon footprint of eighty sectors of the regional economy of the state of Puebla, Mexico. However, not only the accounting of the carbon footprint is relevant when trying to understand the environmental impacts caused by the economic activities of a country or region. It is also essential to quantify and understand the flow of materials and indicators derived from such quantification since intensive and extensive material flow indicators can serve both as a measure for the pressure exerted by the economy on the environment when exploiting natural resources, as well as a potential source of air, water, and soil contaminants. This doctoral thesis is structured around three core chapters; 5, 6, and 7. In each of these chapters, the results obtained from the quantitative analysis derived from the application of three methodologies are discussed and presented: i) economic life cycle analysis with input-output tables, ii) structural decomposition analysis with input-output tables, and iii) material flow accounting and analysis; all of these applied to the case study of the state of Puebla in Mexico. Chapters 5 and 6 are developed around the analysis of the carbon footprint caused by electricity usage in the eighty industrial and commercial sectors of the Mexican economy, reported in the input-output table extracted from the EORA database for the year 2013. For chapter 5, it was calculated the needed electric usage for satisfying the intermediate and final demand of the Mexican economy; the carbon footprint for each of the eighty sectors mentioned above was calculated, by using the national electric emission factor. Chapter 6 presents the results of the structural decomposition analysis. The purpose of this analysis was to identify the level of influence that fluctuations in final demand and technological changes had in the variation of final production in each of the eighty studied sectors, in Mexico and Puebla, comparing the years 2008 and 2013. Productive links were also estimated for each of the sectors. Chapter 7 offers a prospect of community metabolism by using the material flow accounting methodology, through which intensive and extensive indicators of the use of materials by Mexico’s and Puebla’s economies have been obtained from 2004 to 2017. These indicators allow determining the metabolic profiles of Mexico’s (country) and Puebla’s (state) economies.
Universitat Autònoma de Barcelona. Programa de Doctorat en Ciència i Tecnologia Ambientals

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Marszewska, Jowita E. "Development of microporosity in carbons for carbon dioxide adsorption." Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1492043634249216.

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Silva, Orlando Paulino da. "O seqüestro de carbono e as substâncias húmicas na área de influência da BR-163 - Cuiabá-Santarém." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18139/tde-05052009-142442/.

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Compreender os ciclos de nutrientes e a dinâmica da matéria orgânica no ecossistema da Amazônia é essencial para o domínio do manejo eficiente da floresta e do solo. O desaparecimento de florestas tropicais, acompanhada de acelerados processos de perda de solo e de matéria orgânica, pelo desmatamento, queimadas e avanço da fronteira agrícola despertam preocupações. As características das substâncias húmicas remetem aos processos de gênese da matéria orgânica, à capacidade de sustentabilidade para os usos múltiplos em cultivos e aparece como indicador da qualidade do solo. O objetivo deste trabalho foi relacionar as características das substâncias húmicas do solo com o seqüestro de carbono em sítios de floresta em clímax, em área moderadamente e intensamente antropizada, ambientes de influência da Rodovia BR-163 - Cuiabá-Santarém, região que experimenta um incremento das ações antrópicas em função do anúncio da pavimentação desta rodovia. Foram determinadas as características das substâncias húmicas pelas técnicas de espectroscopia no infravermelho com transformada de Fourier (FTIR), análise elementar, espectroscopia de fluorescência de luz no UV/Visível, espectroscopia de absorção de luz no UV/Visível, espectroscopia de ressonância magnética nuclear (RMN) e espectroscopia de ressonância paramagnética eletrônica nuclear (EPR). Os resultados de infravermelho das substâncias húmicas do solo do sítio de floresta em clímax, indicam alta complexidade no arranjo conformacional, denotando-se a presença de elevada humificação do material orgânico, o que é corroborado pelos resultados de fluorescência, onde as características das substâncias húmicas deste ambiente apresentaram maior policondensação e grau de humificação. Utilizando-se a espectroscopia de absorção de luz no UV/Visível, constatou-se que a razão E4/E6 é de 2,27 para solo do ambiente de floresta em clímax. Esse é o menor valor das três frações, o que demonstra que as substâncias húmicas deste sítio estão em estágio elevado de policondensação e apresentam maior quantidade de estruturas aromáticas. Os resultados de RMN indicam que a maior percentagem de carbono aromático está exatamente nas substâncias húmicas do solo do sítio de floresta em clímax. Os resultados de EPR demonstram também que as substâncias húmicas dos solos dos sítios em clímax apresentam maiores números de radicais livres do tipo semiquinona (7,52) dos três ambientes estudados. As substâncias húmicas provenientes dos solos dos sítios com intensa atividade antrópica indicam a presença de menor grau de humificação, pelo número de radicais livres do tipo semiquinona (4,68), menor valor dos três ambientes estudados. Desta forma, as características das substâncias húmicas do solo de ambientes em clímax, pela elevada aromaticidade, policondensação e grau de humificação, proporcionam aumento da biodiversidade, incremento da produtividade, melhoria da estrutura deste solo, contribuindo junto à formação de fração húmica não lábil, bem como maior estabilidade dos complexos organominerais, condições favoráveis para o seqüestro de carbono e mitigação do aumento do efeito estufa.
Understanding the cycles of nutrients and organic matter dynamics in Amazons ecosystem is essential for the domain of efficient management of the forest and soil. The disappearance of tropical forests, accompanied by processes of accelerated loss of soil and organic matter, for the deforestation, forest fires and advancement of agricultural frontier arouse concerns. The characteristics of humic substances refer processes of genesis organic matter, capacity of sustainability for multiple uses in cultures appears as indicator the quality of the organic matter. The objective of this work was to relate the characteristics of humics substances in the soil, with the carbon sequestration in sites of forest in climax, in moderately and intensely area in humans use, environments in Influence of highway BR-163 - Cuiaba-Santarem, a region experiencing an increase in action of the human being according to the announcement of paving the road. There were certain characteristics of humic substances by the Fourier transform infrared (FTIR) spectroscopy, elemental analysis, ultraviolet-visible fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and electronic paramagnetic resonance (EPR) spectroscopy. The results of infrared of humic substances in soil site of a climax forest, show high complexity in conformal arrangement, showing up the presence of high humification of organic material, which is corroborated by the results of fluorescence, where the characteristics of humic substances this environment polycondensation and had greater degree of humification. Using ultraviolet-visible absorption spectroscopy, it was found that the reason E4/E6 is 2.27 for the environment of forest in climax. This is the lowest of the three fractions, which shows that the humic substances from this site are in high stage of polycondensation and the greatest amount of aromatic structures. The results of NMR indicate that the highest percentage of carbon aromatic is exactly humic substances in soil from site of forest in climax. The results of EPR also demonstrate that the soil humic substances in climax\'s sites show the highest numbers of free radicals semiquinonas type (7.52) in the three kinds of environments studied. The humic substances from the soil of sites with intense human activity indicate the lesser presence of degree humification, for the number of free radicals semiquinona\'s type (4.68), lower value of the three environments studied. Thus, the characteristics of humic substances in soil from environments in the climax for the high aromaticity, polycondensation and degree of humification, provide an increase of biodiversity, increasing productivity, improving the structure of the soil, contributing next to the formation of humic fraction not labile, greater stability of organic minerals complexes, favourable conditions for carbon sequestration and mitigation of increased greenhouse effect.

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Charron, Morgan. "Modélisation basée images du comportement thermomécanique de composite C/C." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0670/document.

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Les composites C/C sont principalement utilisés dans les applications à très haute température et notamment dans le domaine du spatial. Savoir concevoir ces matériaux est essentiel pour améliorer leurs performances et diminuer les coûts de production. Ce mémoire présente le développement d’un modèle multiéchelle basé images du comportement thermomécanique d’un composite C/C à renfort 3Daiguilleté. L’utilisation de méthodes classiques ne permet pas de décrire correctement cette architecture très complexe. La méthode CEPI (Computing Effective Properties using Images) présentée s’appuie d’une part sur les propriétés des constituants, dont certaines ont été caractérisées au laboratoire, etd’autre part sur l’architecture de ces matériaux, qui a été obtenue à partir d’une image tomographique.Les propriétés mesurées des constituants ont été directement utilisées dans un modèle microscopique de fil idéal, le modèle macroscopique étant lui directement basé sur l’image de tomographie. Les paramètres des calculs aux différentes échelles ont ensuite été étudiés et discutés pour en déterminer l’influence et permettre de valider certaines hypothèses. La comparaison des résultats numériques et expérimentaux a enfin permis de valider la méthode CEPI sur le comportement mécanique linéaire et de mettre en avant les principaux axes d’améliorations pour le comportement en dilatation des ces composites
C/C composites are used in very high temperature applications, especially in space activities. The ability to design these materials is essential in order to enhance their performances and lower their production costs. This work introduces an images-based multiscale modeling of the thermomechanical behavior of a C/C needled composites. Standard methods cannot describe this very complex architecture.The CEPI model (Computing Effective Properties using Images) is based on one hand on the components properties, some of them having been characterized in the laboratory, and on the other hand on the architecture of the material which is directly obtained using tomography images. The components properties were used on a microscopic model of an idealistic yarn, while the macroscopic model was based on the CT scan data itself. The influence of the internal parameters of the method was studied and discussed, and allowed validating some hypotheses. Finally, the comparison between the numerical and experimental results validates the CEPI model on the linear mechanical behavior and stressed the key axes of improvement for the thermal expansion behavior of these composites

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Rawlins, Charles Henry. "Geological sequestration of carbon dioxide by hydrous carbonate formation in steelmaking slag." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Rawlins_09007dcc804d4f95.pdf.

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Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 18, 2008) Includes bibliographical references.

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Nickerl, Georg. "Synthese metallorganischer Gerüstverbindungen und poröser Polymere für den Einsatz in der Katalyse, Sensorik und Stofftrennung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-151847.

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Poröse Materialien zeichnen sich durch hohe spezifische Oberflächen bzw. hohe spezifische Porenvolumina aus. Dies macht sie zu geeigneten Kandidaten für die Gasspeicherung, Stofftrennung und die heterogene Katalyse, die Hauptanwendungsgebiete poröser Materialien. Um poröse Materialien hinsichtlich der eben genannten Anwendungsfelder zu optimieren ist es von entscheidender Bedeutung, sie hinsichtlich ihrer jeweiligen Anwendung maßzuschneidern. Eine Klasse hochporöser Materialien, bei der das Maßschneidern der Poren möglich ist, ist die der metallorganischen Gerüstverbindungen [engl. Metal-Organic Frameworks (MOFs)]. MOFs zeichnen sich durch einen modularen Aufbau aus, der ein systematisches Design der Poren erlaubt. Auch poröse Polymere können durch Funktionalisierung der entsprechenden Monomere hinsichtlich verschiedener Anwendungsgebiete gezielt synthetisiert werden. Ein Ziel dieser Arbeit war die Integration des Metalls Rhodium als knotenbildendes Element in ein MOF. Dazu wurde Rhodium(II)-acetat, welches bereits das Schaufelradmotiv enthält, mit den trifunktionellen Carbonsäuren Trimesinsäure und 4,4´,4´´ Benzen-1,3,5-triyl-tribenzoesäure zu den MOFs DUT 82 und DUT 83 umgesetzt. Das Schaufelradmotiv als sekundäre Baueinheit in DUT-82 konnte durch röntgenabsorptionspektroskopische Untersuchungen nachgewiesen werden. Nach überkritischem Trocknen gefolgt von thermischer Aktivierung zeigten DUT-82 und DUT-83 eine permanente Porosität mit spezifischen BET-Oberflächen von bis zu 1150 m2g-1. Weiterhin konnte für DUT-82 eine sehr hohe Affinität zu Kohlenmonoxid, die selten für MOFs beobachtet wird, nachgewiesen werden. Berechnungen der Adsorptionsenthalpie ergaben bei niedrigen Beladungen einen Wert von ungefähr 50 kJmol-1, was für eine Chemisorption von Kohlenmonoxid an DUT-82 bei niedrigen Drücken spricht. Weiterhin zeigten katalytische Untersuchungen, dass sich DUT-82 als heterogener Hydrierkatalysator eignet. In einer Modellreaktion konnte Styrol erfolgreich zu Ethylbenzen umgesetzt werden. In einem weiteren Teil der Arbeit sollte ein MOF synthetisiert werden, das Stabilität und eine hohe Kapazität für Schwefelwasserstoff miteinander vereint. Eine Klasse bereits bekannter MOFs mit hoher Stabilität basiert auf dem [Zr6O4(OH)4]12+-Cluster. Durch Kombination des [Zr6O4(OH)4]12+-Clusters mit Bipyridindicarboxylat konnte das MOF UiO-67(bipy) hergestellt werden, welches isostrukturell zu UiO 67 ist. Untersuchungen an UiO 67(bipy) zeigten, dass das unbeladene Netzwerk keinen Schwefelwasserstoff adsorbiert. Die Bipyridinfunktionalität wurde anschließend für die permanente Integration weiterer Metallzentren (Metall = Cu, Ni, Co) genutzt. Dazu wurde UiO-67(bipy) zu wässrigen oder ethanolischen Metallsalzlösungen gegeben und es kam zur Adsorption der Metallsalze aus der Flüssigphase. Durch die postsynthetische Integration der Metallsalze konnte die Adsorptionskapazität der resultierenden Metallsalz@UiO-67(bipy)-Materialien für Schwefelwasserstoff bis auf 8 Gew.% gesteigert werden. Neben Adsorption und Katalyse ist die Sensorik ein weiteres Anwendungsfeld von MOFs. Eine organische Einheit, die sich als sensitive Komponente für eine Integration in ein MOF anbietet, ist Dihydro-1,2,4,5-tetrazin, das zu 1,2,4,5-Tetrazin oxidiert werden kann. Das bemerkenswerte Merkmal dieser Reaktion ist der radikale Farbwechsel von Gelb nach Pink. Nach erfolgreicher Synthese der Dihydro-1,2,4,5-tetrazindicarbonsäure sollte sie durch Kombination mit dem [Zr6O4(OH)4]12+-Cluster zu einem UiO-66 analogen Netzwerk in ein stabiles Netzwerk integriert werden. Da die direkte Syntheseroute eines UiO-66 analogen Netzwerks nicht zum Erfolg führte, wurde die mildere Variante des Linkeraustauschs gewählt. Über diese Route konnte das Dihydro-1,2,4,5-tetrazindicarboxylat erfolgreich partiell in das UiO-66 Netzwerk integriert werden. Anschließende Untersuchungen zeigten, dass die in das Netzwerk eingebaute Dihydro-1,2,4,5-tetrazin-Einheit sowohl in der Flüssig- als auch in der Gasphase erfolgreich oxidiert werden kann, was durch UV/vis-Messungen belegt werden konnte. Eine weitere Klasse poröser Materialien, die hervorragende chemische Stabilität aufweist, ist die der konjugierten Triazin-Netzwerke. Sie entstehen durch Cyclotrimerisierung multifunktioneller Nitrile. Durch geschickte Wahl der Monomere ist eine Funktionalisierung der Triazin-Netzwerke möglich. Um ein chirales Triazin-Netzwerk zu synthetisieren, wurde Spirobiindan erfolgreich mit Nitrilgruppen funktionalisiert. Die Umsetzung des Monomers in einer Zinkchlorid-Schmelze führte zu porösen Polymeren mit spezifischen BET-Oberflächen von bis zu 1180 m2g 1. Dabei konnte die Porengrößenverteilung des Triazin-Netzwerkes durch Variation des Verhältnisses von Zinkchlorid zu Monomer gezielt eingestellt werden. Die Polymersynthese erfolgte mit einer racemischen Mischung des Monomers und führte somit zu einem achiralen Polymer. Erste Untersuchungen zeigten, dass eine Trennung des racemisch vorliegenden Monomers mittels Hochleistungsflüssigchromatographie möglich ist. Die Imidazoliumgruppe ist eine weitere Baueinheit, die in Triazin-Polymere integriert werden sollte, da sie leicht in ein N-Heterocyclisches Carben überführt werden kann. N-Neterocyclische Carbene können direkt als Katalysator bzw. als Ligand für eine Vielzahl von Metallen zur Generierung eines Katalysators genutzt werden. Über mehrstufige Synthesen konnten zwei nitrilfunktionalisierte Imidazoliumsalze hergestellt werden. Die anschließende Cyclotrimerisierung führte zu porösen Polymeren mit spezifischen BET-Oberflächen von bis zu 680 m2g-1. Erste katalytische Untersuchungen zum Einsatz dieser Triazin-Netzwerke in Umpolungsreaktionen von Zimtaldehyd mit 2,2,2 Trifluoracetophenon zeigten jedoch lediglich einen geringen Umsatz zum gewünschten Produkt.

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Martí, Roura Mireia. "Dinàmica del carboni i el nitrogen en brolles i prats secs mediterranis després del foc." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/128924.

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Les zones forestals han augmentat a la regió mediterrània al llarg de les últimes dues dècades degut a l’abandonament de l’agricultura. Això, juntament amb l’augment de períodes d’intensa sequera degut a l’efecte del canvi climàtic, ha fet augmentar la freqüència i la intensitat dels focs forestals. Els focs forestals tenen un efecte directe sobre la biogeoquímica dels sòls modificant-ne la qualitat i la quantitat de la matèria orgànica i d’altres macroelements com el nitrogen, imprescindible per la regeneració de la comunitat vegetal. Malgrat la major part de la biomassa vegetal es crema durant un incendi, una part important de matèria orgànica pot ser dipositada de nou al sòl en forma de residus parcialment cremats formant estructures molt recalcitrants. D’altra banda, el nitrogen mineral alliberat després del foc, pot quedar retingut físicament, mitjançant l’associació amb partícules fines del sòl (llims i argiles) o químicament, a partir de la inclusió a la matèria orgànica recalcitrant del sòl, evitant-ne així el seu rentat i, per tant, la pèrdua de l’ecosistema. Per tal d’entendre millor els canvis en la matèria orgànica del sòl i la dinàmica del N mineral alliberat després del foc, es van seleccionar tres comunitats vegetals diferents (prat de llistó, prat de llistó amb argelaga i brolla de romaní) amb diferències en quant a la proporció de plantes herbàcies i llenyoses i amb la presència o absència d’argelaga (planta fixadora de nitrogen atmosfèric). En aquestes comunitats s’hi van realitzar una sèrie de cremes experimentals i, posteriorment, les cendres van ser marcades amb un isòtop estable del nitrogen (15N). Es van realitzar mostrejos posteriors durant 12 anys per tal d’observar els efectes del foc a llarg termini. Amb els sòls obtinguts es va realitzar: (1) un estudi de la dinàmica del carboni a llarg termini mitjançant una sèrie de simulacions utilitzant el model Roth C, (2) un seguiment del traçador 15N al sòl i a la vegetació al llarg del temps i a diferents profunditats, (3) un estudi de la protecció física i química a la que és sotmesa el N mineral alliberat (marcat amb 15N) mitjançant un fraccionament físic granulomètric i una hidròlisi àcida posterior per observar el grau de recalcitrància d’aquest N incorporat i, finalment, (4) un estudi de la matèria orgànica pirogènica formada per compostos refractaris considerats inerts i de la incorporació del N mineral alliberat després del foc a aquesta matèria orgànica. La baixa intensitat dels focs forestals que van afectar les brolles i prats secs va provocar que els canvis quantitatius en el C orgànic i en el N total del sòl no fossin gaire destacats després del foc i que la recuperació davant d’aquests canvis fos molt ràpida. A més l’estudi a llarg termini va incloure un període prolongat de sequera que va provocar l’augment d’aports de matèria orgànica al sòl. Per altra banda, una bona part del marcatge amb 15N aplicat pel seguiment del N mineral alliberat just després del foc, al cap de 12 anys, encara estava retingut al sòl a les comunitats vegetals sense plantes lleguminoses. En canvi, la presència de lleguminoses va afavorir les pèrdues de 15N des del primer any després del foc i també durant el període de sequera. Després del foc es va observar un augment de N a les fraccions granulomètriques intermèdies com a conseqüència de l’entrada de material cremat particulat mentre que el N mineral alliberat després del foc es va incorporar principalment a la fracció més grollera i a la fracció més fina del sòl. El N mineral incorporat a les fraccions fines va associar-se a la matèria orgànica més làbil tot i la protecció física que presenten aquestes partícules. Part del N mineral alliberat després del foc va ser ràpidament incorporat a les estructures més refractàries de la matèria orgànica del sòl, però amb variacions al llarg del temps, qüestionant així la permanència al sòl d’aquest tipus de compostos orgànics.
Forestation has increased in the Mediterranean basin over the last two decades, due to the abandonment of formerly agriculturally used areas. This trend and the occurrence of intense drought periods have led to an increase in the frequency and intensity of wildfires. Fires have a direct effect on soil biogeochemistry, promoting changes on quantity and quality of organic matter and other macroelements such as nitrogen. Although most of a plant biomass is burned during a forest fire, some of it can be accumulated in the soil in recalcitrant form. Mineral nitrogen delivered after fire can be physically retained in soil by association with fine particles (silts and clays) or chemically retained with recalcitrant organic matter. In order to better understand changes in soil organic matter and mineral nitrogen, three different plant communities were selected: grassland (Brachypodium retusum), mixed shrubgrassland (B. retusum and Genista scorpius ) and shrubland (Rosmarinus officinalis). We set experimental fires and then monitored the fate of a 15N-tracer applied to the mineral nitrogen pool over 12 years. Thus, we studied: (1) carbon dynamics in a long term by Roth C simulations, (2) the fate of 15N in plants and soil at different depths, (3) physical and chemical protection of mineral nitrogen by soil size fractionation and acid hydrolysis and, finally (4) pyrogenic organic matter and the incorporation of mineral nitrogen delivered after fire into recalcitrant organic matter. Due to the low intensity of the experimental fires, small changes in organic carbon and total nitrogen content were detected and recuperation from these changes was fast. Moreover, the long-term study included a long drought period which promoted increases in organic matter inputs to soil. On the other hand, a large amount of 15N applied just after fire was still retained in soils after 12 years, but only in plant communities without legumes. In mixed shrubgrassland the presence of legumes (G. scorpius) promoted 15N loss from the first year after fire and also during the drought period. Fire had a shredding effect on organic matter and mineral nitrogen distributed to fine particles associated to the labile organic matter. Part of the mineral nitrogen delivered after fire was incorporated into refractory particles, but the temporal variation of this newly incorporated nitrogen questioned the stability of those highly resistant compounds in soil.

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Vilamajó, Llobera Eloi 1988. "CSEM monitoring at the Hontomín CO2 storage site: modeling, experimental design and baseline results." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400761.

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This thesis is devoted to the development of a land-based controlled-source electromagnetics (CSEM) experimental methodology to be applied to the monitoring of CO2 storage at the Technological Development Plant (TDP) of Hontomín (Burgos, Spain). The main objectives of the thesis are 1) the evaluation of the feasibility of performing a CSEM monitoring at Hontomín, 2) the design of the CSEM monitoring experiment, and 3) the acquisition of the baseline (pre-injection) data set and the processing of the data obtaining the geoelectrical response of the structure. A modeling experiment has been performed simulating the resistivity changes in the reservoir caused by the storage and evaluating the ability of the method to detect them. The study analyzes the capabilities of different experimental configurations (source/receiver location and relative orientation, emission frequencies...) in order to decide the appropriate configuration in views of the real experiment. The study considered the simulation of an experimental configuration in two different moments of the storage process (pre- and post-injection). It compares the synthetic results obtained in each case and seeks the differences to infer the presence of CO2. A wide range of scenarios of increasing complexity were simulated, from 1D models with an infinite CO2 plume to models with a 3D plume in a medium that contains the casings of the injection and monitoring wells and considers the noise conditions at the Hontomín TDP. The CO2 effect on the synthetic data was analyzed with two different approaches: quantifying the signal caused by the CO2 on the data, TLS (time-lapse signal), and comparing it with the noise conditions in the study area, D (detectability). A borehole-to-surface configuration is sensitive to the presence of CO2, to its saturation and to the relative position source/plume. Furthermore, it was observed that the steel casings installed in the injection and monitoring wells affect the EM propagation from the transmitter to the surface. The study concluded that the CSEM monitoring is suitable at Hontomín given that measurable changes will occur between time- lapsed data sets. Considering the results obtained in the modeling study, the CSEM monitoring experiment was designed. The baseline acquisition was carried out between April 21st and 26th 2014. A borehole-to-surface configuration was used with three different transmitter dipoles: 1) vertical dipole in the injection well HI (dVED-1), 2) vertical dipole in the monitoring well HA dVED- 2), and 3) horizontal dipole using one electrode in each well (dHED). Receivers were distributed at the surface in two different patterns: cross-shape and circular-shape. During each emission, 86 surface dipoles were measuring the electric field. Data processing focused on the obtaining of the geoelectrical response of the subsurface for each source/receiver configuration and for each processed frequency. To this goal, time series were divided into segments and, for each one, the transfer function between source transmission and receiver electric field were calculated. Experimental data were analyzed in terms of experimental uncertainty (error associated to each measurement) and experimental repeatability. Experimental results allowed to characterize the geoelectrical response of the Hontomín structure (including steel casings). Baseline data quality is high: experimental errors are lower than 1% in amplitude and 1º in phase for most of the data points. Repeatability is high (differences lower than 1% in most of the cases). The casing influence over the experimental data was investigated. We tested the hypothesis that a current was induced along the casing of the injection well. To reproduce the experimental behavior of the data, a number of scenarios have been simulated. For low frequencies, the hypothesis can explain the experimental data. Considering the high data quality obtained and the results of the modeling study, we consider that the CSEM experiment will be able to detect the CO2-caused resistivity changes in the reservoir after the post-injection repetition of the experiment.
Aquesta tesi se centra en el desenvolupament del mètode electromagnètic de font controlada (CSEM) aplicat al monitoratge de l’emmagatzematge geològic de diòxid de carboni (CO2) a la Planta de Demostració Tecnològica (PDT) d’Hontomín (Burgos). El control del comportament del CO2 es basa en la detecció dels canvis de resistivitat que tenen lloc al reservori un cop el CO2 desplaça la salmorra. La tesi engloba el progrés de l’experiment de monitoratge CSEM des dels seus inicis fins a l’actualitat. En primer lloc, s’avalua la viabilitat del monitoratge mitjançant el mètode CSEM a partir d’un estudi de modelització numèrica i s’analitzen les bondats de diferents configuracions experimentals. L’estudi consisteix en la simulació d’una configuració experimental en dos estadis del procés d’emmagatzematge (pre-injecció i post-injecció) i en la comparació dels resultats sintètics amb l’objectiu de relacionar les diferències amb la presència del CO2. Inclou la simulació d’un ampli rang d’escenaris de complexitat creixent. Es proposen dues aproximacions diferents per poder quantificar el senyal causat pel CO2 i comparar-lo amb les condicions de soroll reals a Hontomín. En segon lloc, es descriu el disseny del dispositiu de control de l’evolució temporal de la ploma de CO2 aplicat a la PDT d’Hontomín i la realització de la campanya pre-injecció. El processat de les dades experimentals ha consistit en el càlcul de la resposta geoelèctrica de la formació geològica, incloent les carcasses metàl·liques dels pous d’injecció i monitoratge. Les dades experimentals s’analitzen en funció del seu error experimental i de la seva repetibilitat. La qualitat de les dades experimentals pre-injecció és alta respecte als dos punts de vista: els errors experimentals són inferiors a l’1% en l’amplitud i a 1º en la fase per la majoria de les dades i les diferències en la repetibilitat són inferiors a l’1% en la majoria dels casos. Finalment, s’estudia la influència de les carcasses sobre les dades experimentals. S’investiga si la inducció d’un corrent al llarg de la carcassa del pou d’injecció pot explicar el seu comportament. A partir de la simulació de diferents escenaris, s’ha comprovat que la hipòtesi és capaç de reproduir el comportament qualitatiu de les dades a freqüències baixes.

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Martínez, Rodríguez Luis. "Molecule and catalyst design for recognition and activation of small molecules." Doctoral thesis, Universitat Rovira i Virgili, 2016. http://hdl.handle.net/10803/398693.

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Dörling, Bernhard. "Conjugated materials for thermoelectrics and photovoltaics." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/405360.

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Esta tesis explora cómo las interacciones entre materiales orgánicos pueden ser aprovechadas para obtener funcionalidad adicional de una manera sencilla, sin necesidad de procesamiento complejo. Los resultados obtenidos tienen aplicaciones en el campo de la fotovoltaica y termoeléctrica orgánica. El trabajo se centra en materiales tales como polímeros conjugados y nanotubos de carbono, y procesos de deposición desde disolución simples, como el recubrimiento por cuchilla. La primera parte presenta resultados sobre la caracterización elipsométrica de las propiedades ópticas de los polímeros conjugados y sus mezclas con fullerenos o dopantes. La elipsometría espectroscópica de ángulo variable se utilizó no sólo para caracterizar las constantes ópticas de nuevos polímeros altamente absorbentes, sino también para investigar el efecto de los aditivos disolventes sobre el grado de segregación vertical de fase en mezclas de polímero:fullereno. La segunda parte detalla el trabajo sobre nanocompuestos de polímeros conjugados y nanotubos de carbono, una prometedora clase de materiales termoeléctricos orgánicos. Debido a que los polímeros conjugados permiten desenredar los manojos de nanotubos de carbono de manera eficiente, estos nanocompuestos se pueden preparar fácilmente. Presentan tanto una buena conductividad eléctrica como una baja conductividad térmica, que son requisitos necesarios para un buen rendimiento termoeléctrico. De particular interés son los compuestos de tipo n que contienen nanotubos de carbono dopados con nitrógeno, así como métodos de procesamiento que permiten cambiar el tipo de portador mayoritario. La tercera parte se centra en técnicas sencillas de fabricación de dispositivos fotovoltaicos orgánicos, con el objetivo particular de obtener capas orientadas de polímeros conjugados. Esto se logró controlando localmente la evaporación del disolvente para influir en la cristalización epitaxial direccional de polímeros conjugados en un aditivo disolvente cristalino. El método desarrollado permite preparar dos tipos distintos de películas. Si la nucleación del aditivo se limita a la línea de contacto unidimensional durante el recubrimiento con cuchilla, se obtienen entonces películas uniaxialmente orientadas con una morfología fibrilar. Al limitar la nucleación a un punto, se puede crecer una superestructura cristalina circular conocida como esferulita en cualquier lugar deseado de la película. Los dispositivos fotovoltaicos orgánicos que se prepararon a partir de estas películas orientadas tienen aplicaciones como detectores del estado de polarización de la luz.
This thesis explores ways of how interactions between organic materials can be exploited to obtain additional functionality in a simple manner, without the need for complex processing. The obtained results have applications in the field of organic photovoltaics and thermoelectrics. The work focuses on materials such as conjugated polymers and carbon nanotubes, and simple solution-based deposition processes such as blade coating. The first part presents results on the ellipsometric characterization of the optical properties of conjugated polymers and their blends with fullerenes or dopants. Variable angle spectroscopic ellipsometry was used not only to characterize the optical constants of new, highly absorbing polymers, but also to investigate the effect of solvent additives on the degree of vertical phase segregation in polymer:fullerene blends. The second part details the work on nanocomposites of conjugated polymers and carbon nanotubes, a promising class of organic thermoelectric materials. Because conjugated polymers allow for efficient debundling of carbon nanotubes, these nanocomposites can be prepared readily. They exhibit both a good electrical conductivity and a low thermal conductivity, which are necessary requisites for good thermoelectric performance. Of particular interest are n-type composites containing nitrogen-doped carbon nanotubes, as well as processing methods that allow to change the majority carrier type. The third part focuses on simple fabrication techniques for organic photovoltaic devices, with the particular objective of obtaining oriented layers of conjugated polymers. This was achieved by locally controlling solvent evaporation to influence the directional epitaxial crystallization of conjugated polymers on a crystalline solvent additive. The developed method allows to prepare two distinct types of films. If the nucleation of the additive is confined to the one-dimensional contact line during blade-coating, then uniaxially oriented films with a fibrillar morphology are obtained. By confining the nucleation to a point, a circular crystalline superstructure known as a spherulite can be grown at any desired location in the film. The organic photovoltaic devices that were prepared from these oriented films have applications as detectors of the polarization state of light.

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Muscelli, Wesley Cardoso. "Preparação e caracterização de materiais de carbono via termopolimerização de pré-polímero fenol-formaldeído." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-14092017-164746/.

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O presente trabalho relata a investigação de uma rota reprodutível de obtenção de materiais de carbono a partir do tratamento térmico de pré-polímero fenol formaldeído (resina fenólica) levando em consideração características morfológicas e estruturais.O controle da composição de resina bem como o estabelecimento cuidadoso da rampa de aquecimento foram fatores decisisvos para a obtenção de materiais análogos ao carbono vítreo de maneira reprodutível. Os materiais obtidos apresentaram reduzida presença de poros e condutividade térmica apreciável uma vez que foram testados como eletrodos de trabalho em ensaios eletroquímicos . A análise estrutural e morfológica dos compostos sintetizados demonstrou a presença de estrutura semelhante ao carbono vítreo relatado na literatura com presença de poucos poros superficiais da ordem de micrômetros até nanômetros. Já em relação aos materias de carbono porosos, buscou-se obter compostos com arranjo ordenado de mesoporos. Resultados preliminares demonstraram que os materiais apresentaram poros micrométricos superficiais organizados.
The present work reports on the investigation of reproducible route to synthesize carbon materials from phenolic resin take into account the structural and morphological features. The control or the resin composotion and the careful establinshing of the ramp heating were decisive for achievement the materials analogous to the glassy carbon (vitreous carbon) in a reproducicle way. The materials obtained materials revealed the glassy carbon structure with the presence of the superficial pores in the range of micrometers to nanometrers. In relation to the carbon materilas, they organized arrangement of the porous in the micrometric scale.

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Zhang, Tengyan. "Preparation and characterization of carbon molecular sieves and activated carbons /." Search for this dissertation online, 2004. http://wwwlib.umi.com/cr/ksu/main.

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Lin, Youqin. "Deposition of a carbon or polypyrrole nano-layer on carbon nanotubes-alumina hybrids and its impact on their mechanical and physical properties." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2012. http://www.theses.fr/2012ECAP0004.

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La croissance de nanotubes de carbone (NTC) sur particules micrometriques d'alumine (Al2O3) permet d'obtenir une dispersion uniforme des NTC dans des matrices sans enchevêtrement de NTC. Ce type de structure hybride NTC-Al2O3 fournit également une solution prometteuse au problème de sécurité de NTC car ils intègrent NTC avec des particules micrométriques, étendant la dimension des NTC à partir de nano-échelle au micro-échelle. Cependant, l'adhérence entre les NTC et les Al2O3 particules ne permet pas de fixer efficacement les NTC. Par ailleurs, une autre préoccupation essentielle de NTC est de savoir comment créer une forte adhésion interfaciale entre les NTC et les matrices polymères pour obtenir de bonnes propriétés mécaniques et de ne pas diminuer la conductivité électrique de NTC. Motivé par ces considérations, cette thèse vise à proposer plusieurs techniques concernant le dépôt d'une nano-couche conductrice sur la surface des structures hybrides NTC-Al2O3. De plus, les impacts de la nano-couche déposée sur la fixation des NTC à la surface d’Al2O3, sur la conductivité électrique des hybrides NTC-Al2O3, et sur l'adhésion interfaciale des systèmes NTC-Al2O3/epoxy composites sont étudiés en détail
Growth of carbon nanotubes (CNTs) on micro-sized alumina (Al2O3) particles helps to achieve a uniform dispersion of CNTs in matrices without CNT entanglement. This kind of CNT-Al2O3 hybrids also provides a promising solution to the CNT safety problem since they integrate CNTs with micrometric particles, extending dimension of CNT fillers from nano-scale to micro-scale. However, the adhesion between the CNTs and the Al2O3 particles doesn’t sufficiently enable to fix the CNTs firmly and stably. Besides, another crucial concern of CNTs is how to create a strong interfacial adhesion between CNTs and polymer matrices for good mechanical properties and meanwhile not to degrade CNTs’ electrical conductivity. Motivated by these considerations, this PhD thesis aims to establishing several techniques for deposition of an electrically conductive nano-layer on the surface of CNT-Al2O3 hybrids. And the impacts of the deposited nano-layer on the fixing the CNTs on the Al2O3 surface, on bulk electrical conductivity of the CNT-Al2O3 hybrids, and on the interfacial adhesion of CNT-Al2O3/epoxy composite systems are investigated in detail

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46

Blasco, Gómez Ramiro. "Steering CO2 bio-electrocycling into valuable compounds through inline monitoring of key operational parameters." Doctoral thesis, Universitat de Girona, 2020. http://hdl.handle.net/10803/670848.

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Microbial Electrochemical Technologies (METs) are a promising alternative for capturing and in-situ reducing CO2 through the use of renewable electricity. Microorganisms grown in autotrophic conditions use CO2 as an electron acceptor and an electrode provides them electrons in the form of electricity. In this process, known as microbial electrosynthesis (MES), different compounds are produced depending on the metabolic possibilities of the microorganisms present in the system. The potential of this technology is high: a culture enriched with selected electroactive microorganisms is able to effectively transform CO2 into high value-added compounds. This Doctoral Thesis investigated reliable operational procedures for the monitoring of the performances of METs to produce suitable substrates for economically viable downstream applications. The cathodes of two different designs of bioelectrochemical systems (BESs) were inoculated with an enriched culture of a carboxydotrophic strain and were operated until stable conversion of CO2 into acetate, ethanol and small amounts of butyrate.
Les tecnologies microbianes electroquímiques (METs) són una alternativa prometedora per capturar i reduir in situ el CO2 a través de l’ús d’electricitat renovable. Microorganismes cultivats en condicions autotròfiques usen CO2 com a acceptor d’electrons i un elèctrode aporta electrons en forma d’electricitat. En aquest procés, conegut com a electrosíntesi microbiana (MES), es produeixen diferents compostos en funció de les possibilitats metabòliques dels microorganismes presents al sistema. El potencial d’aquesta via és alt: un cultiu enriquit de microorganismes electroactius seleccionats pot fer possible la transformació del CO2 en compostos d’alt valor afegit. En aquesta tesi s'han estudiat diferents paràmetres d'operació que a través d'un monitoratge exhaustiu durant la transformació de l'CO2 mitjançant reactors MET. Es van utilitzar dos dissenys de reactor diferents (tubular i pla) de sistemes bioelectroquímics (BES; sigles en anglès) que van ser inoculats amb un cultiu enriquit amb una soca carboxidotrófica electroactiva i es van operar fins aconseguir l’electro-conversió estable de el CO2 en acetat, etanol i petites quantitats de butirat.

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47

Ferrufino, Gretta Larisa Aurora Arce [UNESP]. "Uma modelagem de sequestro e armazenamento de dióxido de carbono atmosférico." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/99319.

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Made available in DSpace on 2014-06-11T19:30:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-12-08Bitstream added on 2014-06-13T18:40:02Z : No. of bitstreams: 1 arceferrufino_gla_me_guara.pdf: 1056072 bytes, checksum: 1cac7a1cd9ce6c0468bceb4898770311 (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O dióxido de carbono (CO2) é um importante gás de efeito estufa. No entanto, um aumento gradual ameaça substancialmente o clima. Um dos principais desafios do planejamento ambiental é identificar um modelo que vincule todos os fatores do ciclo de carbono, ou seja, oceano – ecossistema terrestre – emissão antropogênica – atmosfera. Princípios básicos de Termodinâmica podem ser aplicados em uma modelagem estatística com bases em séries históricas para obter concentrações de CO2 na atmosfera, possibilitando a construção de cenários para uma melhor tomada de decisões. Por este motivo, foi desenvolvido no trabalho um modelo que interliga todos os fatores do ciclo de carbono, focalizando em quatro zonas térmicas ou climáticas (Boreal, Temperada, Tropical, Polar), para cálculos de armazenamento de CO2 atmosférico. Os resultados mostram que no ano 2100 se atingirá uma concentração de CO2 quatro vezes maior do que antes do período pré-industrial. A zona temperada emite quase a metade de dióxido de carbono à atmosfera na atualidade; para o ano 2100, essa emissão aumentará a quinze vezes mais que a zona tropical. A China será responsável em uma proporção de vinte quatro a onze com relação aos Estados Unidos. A estabilização das concentrações de CO2 na atmosfera será obtida quando as emissões de dióxido de carbono antropogênico tiverem uma diminuição de mais do que trinta e quatro por cento para o ano 2100 na zona temperada.
Carbon dioxide (CO2) is the most important greenhouse gas. A gradual increase on its atmospheric concentration threatens significantly the climate. One of the main challenges of environment planning is to identify a model that connects all factors that determine the carbon cycle, that is, ocean – terrestrial ecosystem – anthropogenic emissions – atmosphere. Basic thermodynamic principles can be applied in a statistical modeling with historic time series to obtain atmospheric CO2 concentration, creating the possibility of construction of scenarios that will help decision making. A model that links all carbon cycle factors was developed in this dissertation work, focusing in four thermal of climatic zones (Boreal, Temperate, Tropical, and Polar) for calculations of atmospheric CO2 storage. Results show that in 2100, the atmospheric CO2 concentration will reach a value four times higher than that of the pre-industrial period. The temperate zone already emits almost half of the carbon dioxide to the atmosphere; by 2100, this emission will increase 15 times more than that corresponding to the tropical zone. China will be responsible for emissions in a proportion of 24 to 11 in comparison to that of the United States. Stabilization of CO2 concentrations in the atmosphere will be obtained when the anthropogenic carbon dioxide emissions attain a decrease of at least 34% in 2100 in the temperate zone.

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48

Maestro, Luis Fernando. "Aperfeiçoamentos na obtenção de nanotubos de carbono com paredes simples (NTCPS) e possíveis aplicações na estocagem de energia." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277457.

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Orientador: Carlos Alberto Luengo
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Desde a sua descoberta em 1991, os Nanotubos de Carbono (NTC) têm atraído muito a atenção da comunidade científica, devido as suas propriedades. Neste trabalho é apresentada uma breve revisão das pesquisas em NTC e algumas definições básicas relevantes para a sua estrutura e propriedades. Em vista da utilização deste material em uma futura aplicação e devido ao interesse do grupo na área de energia, é apresentado o estado da arte do armazenamento de Hidrogênio e, em particular, no armazenamento em sólidos de grande área superficial, classe a qual os NTC pertencem. Apresentam-se as modificações realizadas em um Reator de Arco Elétrico (Forar II) para se realizar a Síntese de NTC, são relatadas as experiências e a caracterização das amostras obtidas utilizando-se Microscopia Eletrônica de Varredura e Espectroscopia Raman.
Abstract: Since their discovery in 1991 Carbon Nanotubes (CNT) have received increasing attention by the scientific community due to their properties. Here is presented a brief review of ongoing CNT research, and basic definitions useful to understand their structure and significant properties. Because of future applications in the energy area, are presented developments in Hydrogen storage, more specifically its adsorption in solids with large internal surface areas, a characteristic of CNT materials. Modifications of the existing FORAR II to obtain CNT by the electric arc method are presented, and a description of the routines employed to obtain CNT. The characterization of catalysts and CNT by Scanning Electron Microscopy and Raman Spectroscopy are presented and discussed.
Mestrado
Física da Matéria Condensada
Mestre em Física

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49

Ferrufino, Gretta Larisa Aurora Arce. "Uma modelagem de sequestro e armazenamento de dióxido de carbono atmosférico /." Guaratinguetá : [s.n.], 2009. http://hdl.handle.net/11449/99319.

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Resumo: O dióxido de carbono (CO2) é um importante gás de efeito estufa. No entanto, um aumento gradual ameaça substancialmente o clima. Um dos principais desafios do planejamento ambiental é identificar um modelo que vincule todos os fatores do ciclo de carbono, ou seja, oceano - ecossistema terrestre - emissão antropogênica - atmosfera. Princípios básicos de Termodinâmica podem ser aplicados em uma modelagem estatística com bases em séries históricas para obter concentrações de CO2 na atmosfera, possibilitando a construção de cenários para uma melhor tomada de decisões. Por este motivo, foi desenvolvido no trabalho um modelo que interliga todos os fatores do ciclo de carbono, focalizando em quatro zonas térmicas ou climáticas (Boreal, Temperada, Tropical, Polar), para cálculos de armazenamento de CO2 atmosférico. Os resultados mostram que no ano 2100 se atingirá uma concentração de CO2 quatro vezes maior do que antes do período pré-industrial. A zona temperada emite quase a metade de dióxido de carbono à atmosfera na atualidade; para o ano 2100, essa emissão aumentará a quinze vezes mais que a zona tropical. A China será responsável em uma proporção de vinte quatro a onze com relação aos Estados Unidos. A estabilização das concentrações de CO2 na atmosfera será obtida quando as emissões de dióxido de carbono antropogênico tiverem uma diminuição de mais do que trinta e quatro por cento para o ano 2100 na zona temperada.
Abstract: Carbon dioxide (CO2) is the most important greenhouse gas. A gradual increase on its atmospheric concentration threatens significantly the climate. One of the main challenges of environment planning is to identify a model that connects all factors that determine the carbon cycle, that is, ocean - terrestrial ecosystem - anthropogenic emissions - atmosphere. Basic thermodynamic principles can be applied in a statistical modeling with historic time series to obtain atmospheric CO2 concentration, creating the possibility of construction of scenarios that will help decision making. A model that links all carbon cycle factors was developed in this dissertation work, focusing in four thermal of climatic zones (Boreal, Temperate, Tropical, and Polar) for calculations of atmospheric CO2 storage. Results show that in 2100, the atmospheric CO2 concentration will reach a value four times higher than that of the pre-industrial period. The temperate zone already emits almost half of the carbon dioxide to the atmosphere; by 2100, this emission will increase 15 times more than that corresponding to the tropical zone. China will be responsible for emissions in a proportion of 24 to 11 in comparison to that of the United States. Stabilization of CO2 concentrations in the atmosphere will be obtained when the anthropogenic carbon dioxide emissions attain a decrease of at least 34% in 2100 in the temperate zone.
Orientador: João Andrade de Carvalho Junior
Coorientador: Luiz Fernando Costa Nascimento
Banca: José Antonio Perrella Balestieri
Banca: Maria Paulete Pereira Martins Jorge
Mestre

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50

Winkler, Andrea [Verfasser]. "Untersuchungen zu neutralen N-heterocyclischen Carben-Boranen und anionischen N-heterocyclischen Carbenen / Andrea Winkler." München : Verlag Dr. Hut, 2016. http://d-nb.info/1113335882/34.

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Dissertations / Theses on the topic 'Carbeni'

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