Thèses sur le sujet « Nanostructures - Organic Molecules »

The work described in this thesis concerns development, synthesis and characterisation of new molecular compounds and materials based on the carbon allotropes fullerene (C60) and graphene. A stepwise strategy to a symmetric ferrocene-linked dumbbell of fulleropyrrolidines was developed. The versatility of this approach was demonstrated in the synthesis of a non-symmetric fulleropyrrolidine-ferrocene-tryptophan triad. A new tethered bis-aldehyde, capable of regiospecific bis-pyrrolidination of a C60-fullerene in predominantly trans fashion, was designed, synthesised and reacted with glycine and C60 to yield the desired N-unfunctionalised bis(pyrrolidine)fullerene. A catenane dimer composed of two bis(pyrrolidine)fullerenes was obtained as a minor co-product. From the synthesis of the N-methyl analogue, the catenane dimer could be separated from the monomeric main product and fully characterised by NMR spectroscopy. Working towards organometallic fullerene-based molecular wires, the N-unfunctionalised bis(pyrrolidine)fullerene was coupled to an activated carboxyferrocene-fullerene fragment by amide links to yield a ferrocene-linked fullerene trimer, as indicated by mass spectrometry from reactions carried out at small scale A small library of conjugated diarylacetylene linkers, to be coupled to C60 via metal-mediated hydroarylation, was developed. Selected linker precursors were prepared and characterised, and the hydroarylation has been adapted using simple arylboronic acids. Few-layer graphene was prepared and dip-deposited from suspension onto a piezoelectric polymer substrate. Spontaneous side-selective deposition was observed and, from the perspective of non-covalent interaction, rationalised as being driven by the inbuilt polarization of the polymer. Aiming for selectively edge-oxidized graphene, a number of graphitic materials were treated with a combination of ozone and hydrogen peroxide under sonication. This mild, metal-free procedure led to edge-oxidation and exfoliation with very simple isolation of clean materials indicated by microscopy, spectroscopy, and thermogravimetric analysis.

Organic photovoltaics have attracted considerable research and commercial interest due to their lightness, mechanical flexibility and low production costs. There are two main approaches for the fabrication of organic solar cells – solution and vacuum processing. The former relies on morphology control in polymer-fullerene blends resulting from natural phase separation in these systems. The latter takes advantage of solvent-free processing allowing highly complex multi-junction architectures similar to inorganic solar cells. This work aims to combine the benefits of both by depositing conjugated polymers using vacuum thermal evaporation. By employing this unconventional approach it aims to enhance the efficiency of organic photovoltaics through increased complexity of the thin-film architecture while improving the nanoscale morphology control of the individual active layers. The thesis explores the vacuum thermal deposition of polythiophenes, mainly poly(3-hexylthiophene) (P3HT) and side-group free poly(thiophene) (PTh). A variety of chemical techniques, such as NMR, FT-IR, GPC, DSC and TGA, are used to examine the effect of heating on chemical structure of the polymers. Optimal processing parameters are identified and related to the resulting thin-film morphology and charge transport properties. Efficient photovoltaic devices based on polythiophene donors and fullerene acceptors are fabricated. Materials science techniques AFM, XRD, SEM, TEM and MicroXAM are used to characterize topography and morphology of the thin films, and UV-Vis, EQE, I-V and C-V measurements relate these to the optical and electronic properties. The results of the study show that polymer side groups have a strong influence on molecular packing and charge extraction in vacuum-deposited polymer thin films. Unlike P3HT, evaporated PTh forms highly crystalline films. This leads to enhanced charge transport properties with hole mobility two orders of magnitude higher than that in P3HT. The effect of molecular order is demonstrated on polymer/fullerene planar heterojunction solar cells. PTh-based devices have significantly better current and recombination characteristics, resulting in improved overall power conversion efficiency (PCE) by 70% as compared to P3HT. This confirms that the chemical structure of the molecule is a crucial parameter in deposition of large organic semiconductors. It is also the first-ever example of vacuum-deposited polymer photovoltaic cell. Next, vacuum co-deposited PTh:C60 bulk heterojunctions with different donor-acceptor compositions are fabricated, and the effect of post-production thermal annealing on their photovoltaic performance and morphology is studied. Co-deposition of blended mixtures leads to 60% higher photocurrents than in thickness-optimized PTh/C60 planar heterojunction counterparts. Furthermore, by annealing the devices post-situ the PCE is improved by as much as 80%, achieving performance comparable to previously reported polythiophene and oligothiophene equivalents processed in solution and vacuum, respectively. The enhanced photo-response is a result of favourable morphological development of PTh upon annealing. In contrast to standard vacuum-processed molecular blends, annealing-induced phase separation in PTh:C60 does not lead to the formation of coarse morphology but rather to an incremental improvement of the already established interpenetrated nanoscale network. The morphological response of the evaporated PTh within the blend is further verified to positively differ from that of its small-molecule counterpart sexithiophene. This illustrates the morphological advantage of polymer-fullerene combination over all other vacuum-processable material systems. In conclusion, this processing approach outlines the conceptual path towards the most beneficial combination of solution/polymer- and vacuum-based photovoltaics. It opens up a fabrication method with considerable potential to enhance the efficiency of large-scale organic solar cells production.

Thesis (Ph. D.)--University of Kentucky, 2003.
Title from document title page (viewed June 30, 2004). Document formatted into pages; contains xv, 150 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 140-148).

Cette thèse traite de l'étude du transport de charge à travers les semi-conducteurs organiques au sein de transistors à effet de champ organiques (OFET). Une grande attention a été accordée aux interfaces dans les OFET dont les propriétés ont été accordées pour moduler la réponse transistor. La stabilité de l'appareil en état de commutation et le mécanisme régissant l'injection de charges ont été étudiés systématiquement. Le transport de charge au niveau fondamental à travers les monocouches auto-assemblées comprenant une grande variété des molécules π-conjuguées a été étudié. Dans cette thèse, le processus de transport de charge et différents paramètres affectant ce phénomène sont examinées en détail par la fabrication et la caractérisation de trois terminaux basés sur des architectures OFET et deux dispositifs de jonctions terminales constituées d'une couche mono-moléculaire sur la surface de l'électrode métallique. Parmi les différents aspects relatifs à l'injection de charge dans des transistors organiques macroscopiques à couches minces, un accent particulier a été mis sur l'interface de l'engineering en réglant (i) le diélectrique / l'interface semi-conducteur, et (ii) l'électrode en métal / le semi-conducteur. Pour explorer les aspects régissant le transport de charge dans le canal de l'appareil, nous avons étudié la propriété de (iii) la mobilité intrinsèque dans la semi-conductivité des matériaux et (iv) l'utilisation de mélanges dans la couche active du dispositif. A l'échelle nanométrique, le transport de charge, grâce à une mono-couche moléculaire chimisorbé sur des électrodes métalliques, a été étudié. Pour effectuer la caractérisation électrique sur la mono couche auto-assemblée (SAM), nous avons construit un système de configuration comprenant des alliages eutectiques de gallium et d'indium liquide métallique (GainE) comme électrode.

This thesis is concerned with the influence of nanoscale boundaries and interfaces upon the electronic processes that occur within the inorganic semiconductors. Inorganic semiconductor nanowires and their blends with semiconducting polymers have been investigated using state-of-the-art ultrafast optical techniques to provide information on the sub-picosecond to nanosecond photoexcitation dynamics in these systems. Chapters 1 and 2 introduce the theory and background behind the work and present a literature review of previous work utilising nanowires in hybrid organic photovoltaic devices, revealing the performances to date. The experimental methods used during the thesis are detailed in Chapter 3. Chapter 4 describes the crucial roles of surface passivation on the ultrafast dynamics of exciton formation in gallium arsenide (GaAs) nanowires. By passivating the surface states of nanowires, exciton formation via the bimolecular conversion of electron-hole plasma can observed over few hundred picoseconds, in-contrast to the fast carrier trapping in 10 ps observed in the uncoated nanowires. Chapter 5 presents a novel method to passivate the surface-states of GaAs nanowires using semiconducting polymer. The carrier lifetime in the nanowires can be strongly enhanced when the ionization potential of the overcoated semiconducting polymer is smaller than the work function of the nanowires and the surface native oxide layers of nanowires are removed. Finally, Chapter 6 shows that the carrier cooling in the type-II wurtzite-zincblend InP nanowires is reduced by order-of magnitude during the spatial charge-transfer across the type-II heterojunction. The works decribed in this thesis reveals the crucial role of surface-states and bulk defects on the carrier dynamics of semiconductor nanowires. In-addition, a novel approach to passivate the surface defect states of nanowires using semiconducting polymers was developed.

From a chemical and structural point of view, hydroxyapatite (HA) is a strong candidate in biomedical applications owing to its similarity to the inorganic components of bones and teeth. HA nanoparticles (NPs) as colloidal suspensions are becoming a popular tool in biomedical applications such as gene/drug delivery, bio-imaging etc. Although it is widely acknowledged that ionic substitutions on bulk HA substrates have a strong impact on their biological performance, little is known of their effect on NPs with potential use in gene transfection or drug delivery. In the third chapter carbonate (CO3) and magnesium (Mg) ions, which are the major substitutions in biological apatite, have been explored in the synthesis of ion-doped HA NPs under similar reaction conditions to allow comparison of results. CO3 and Mg ion were incorporated in the crystal lattice of HA and caused various changes mainly in the morphology and solubility of the different nanoparticles. In addition, the impact of ion doping on the interaction of HA NPs with cells was also evaluated under various cell culture conditions: 1) performing the cell culture study on citrate-dispersed NPs and on agglomerated NPs, 2) adding/excluding 10 % of foetal bovine serum (FBS) in the cell culture media and 3) using different types of cells, i.e. osteosarcoma MG-63 cells versus rat mesenchymal stem cells (rMSCs). The in vitro results indicated that Mg-doped HA NPs induced a profound impact on MG63 cells and, in the absence of citrate and FBS these nanoparticles were clearly cytotoxic. However, Mg-doped HA NPs did not alter cell viability in rMSCs under the same conditions. In the fourth chapter, Sr, Zn, Si and Fe(III) ions, which are minor ionic substitutions in biological apatite, were introduced to synthesize additional ion-doped HA NPs. Physicochemical characterization demonstrated that as-synthesized NPs were phase pure and doped ions had little influence on the morphology of NPs as in all cases they kept needle-like structure. Cytotoxicity studies performed using MG63 and rMSCs cells under the conditions of serum-containing and serum-free indicated that all NPs were non-cytotoxic if FBS was present. Interestingly, Zn-doped and Fe-doped HA NPs clearly stimulated MG63 cell proliferation in the absence of FBS. In addition to exploring the effect of ion-doped HA NPs on cell behaviour, it was also the interest of this thesis to investigate calcium phosphate (CaP) mineralization in the presence of organic molecules and also doping ions. In the fifth chapter of this thesis the effect of various organic molecules on CaP precipitation is provided. As shown by transmission electron microscopic studies (TEM) neuron-like CaP structures could be created using organic molecules of diverse nature such as non-ionic surfactant (Tween 80), anionic polymers (sodium polyacrylate) and cationic polymers (polydiallyldimethylammonium chloride). TEM studies through EELS, EFTEM and SAED proved that the neuron-like structures consisting of a dense core and thin filaments surrounding it had calcium, phosphorous and oxygen evenly distributed throughout the dense core as well as the filaments, and were amorphous in nature. Additionally, the co-effect of inorganic additives (i.e. Mg and Sr) together with organic molecules on CaP was also evaluated. It was proved that the addition of small amounts of ions had diverse impact on the stability of the neuron-like structures Mg clearly disrupting them but not Sr. All the findings with organic molecules provide much inspiration not only for the synthesis of more advanced CaP materials with novel structures and useful properties, but also for a better understanding of biomineralization process in nature.
Desde el punto de vista químico y estructural la hidroxiapatita (HA) se considera un gran candidato para aplicaciones biomédicas por su similitud con la fase mineral del hueso y los dientes. Aunque el efecto del dopaje se ha investigado con detalle en la fabricación de implantes viéndose que su presencia tiene un gran impacto en el comportamiento celular, poco se sabe de su efecto en nanopartículas para su uso en terapia génica y liberación de fármacos. En concreto, el tercer capítulo se centra en el dopaje de la apatita con iones carbonato (CO3) y magnesio (Mg) por ser éstas las sustituciones más importantes en la apatita biológica. Para ello todas las reacciones de síntesis se realizan bajo las mismas condiciones con la finalidad de poder comparar resultados. Los resultados muestran que ambas sustituciones acaban incorporando los iones dentro de la estructura del cristal causando diferentes impactos principalmente a nivel de morfología y solubilidad. Con respecto al impacto del dopaje en la caracterización celular, se llevaron a cabo diferentes ensayos: 1) utilizando suspensiones dispersadas con citrato o sin él, 2) en medio de cultivo con o sin 10 % v/v de suero fetal bovino y 3) utilizando dos tipos de células diferentes, células de osteosarcoma (MG63) y células de rata mesenquimales (rMSCs). Los resultados in vitro mostraron que las nanopartículas dopadas con Mg eran claramente citotóxicas a las células MG63 en ausencia de FBS. Sin embargo, las mismas NPs no alteraron la viabilidad celular en rMSCs bajo las mismas condiciones. El capítulo cuarto se centra en la síntesis y caracterización de NPs dopadas con iones Sr, Zn, Si y Fe(III), que representan sustituciones minoritarias en la apatita biológica. Su caracterización fisicoquímica mostró que todas las NPs eran puras con morfología acicular. Los estudios de citotoxicidad con células MG63 y rMSCs, con y sin FBS, mostraron viabilidad en presencia de FBS para todas las NPs. Además, para las NPs dopadas con Zn y Fe se observó un aumento notable en la proliferación celular para las MG63 cultivadas sin FBS. Además de explorar el efecto del dopaje de iones en NP de HA, otro campo de interés en esta tesis ha sido investigar la mineralización de fosfatos de calcio (CaP) en presencia de moléculas orgánicas y de diferentes iones. A través de estudios recientes en el grupo de investigación se ha visto que es posible formar fosfatos de calcio con estructura neuronal con la ayuda de simples moléculas orgánicas. En el quinto capítulo de esta tesis se estudia el efecto de varias moléculas orgánicas en la precipitación de CaP. Estudios por microscopia electrónica de transmisión (TEM) revelaron la presencia de estas estructuras neuronales formadas con la ayuda de moléculas orgánicas de diferente naturaleza: surfactante no iónicos (Tween 80), polímeros aniónicos (poliacrilato sódico) y políremos catiónicos (cloruro de polidialildimetilamonio). Varios estudios por TEM como son EELS, EFTEM y SAED permitieron establecer que las estructuras neuronales consistían de un núcleo denso del cual se extendía una red de filamentos, que en estas estructuras el calcio, fósforo y oxígeno estaba homogéneamente distribuido y que eran de naturaleza amorfa. Además se investigó el efecto simultáneo de añadir aditivos inorgánicos (iones Mg i Sr) junto con moléculas orgánicas. Se observó que la adición de pequeñas cantidades de iones afectaba la estabilidad de las estructuras neuronales. Con Mg las estructuras no eran estables pero sí con Sr. Estos estudios pueden ser fuente no sólo de inspiración en la síntesis de estructuras más avanzadas y con propiedades notablemente diferentes, sino que además proporcionan un mejor conocimiento de los procesos de biomineralización.

Quantum mechanics has a long history of helping computer science. For a long time, it provided help only at the hardware level by giving a better understanding of the properties of matter and thus allowing the design of ever smaller and ever more efficient components. For the last few decades, much research has been dedicated to finding whether one can change computer science even more radically by using the principles of quantum mechanics at both the hardware and algorithm levels. This field of research called Quantum Information Processing (QIP) has rapidly seen interesting theoretical developments: it was in particular shown that using superposition of states leads to computers that could outperform classical ones. The experimental side of QIP however lags far behind as it requires an unprecedented amount of control and understanding of quantum systems. Much effort is spent on finding which particular systems would provide the best physical implementation of QIP concepts. Because of their nearly endless versatility and the high degree of control over their synthesis, organic materials deserve to be assessed as a possible route to quantum computers. This thesis studies the QIP potential of spin degrees of freedom in several such organic compounds. Firstly, a study on low-spin antiferromagnetic rings is presented. It is shown that in this class of molecular nanomagnets the relaxation times are much longer than previously expected and are in particular long enough for up to a few hundred quantum operations to be performed. A detailed study of the relaxation mechanisms is presented and, with it, routes to increasing the phase coherence time further by choosing the suitable temperature, isotopic and chemical substitution or solvent. A study of higher-spin systems is also presented and it is shown that the relaxation mechanisms are essentially the same as in low-spin compounds. The route to multi-qubit system is also investigated: the magnetic properties of several supermolecular assemblies, in particular dimers, are investigated. Coupling between neighbouring nanomagnets is demonstrated and experimental issues are raised concerning the study of the coherent dynamics of dimers. Finally a study of the purely organic compound phenanthrene is reported. In this molecule the magnetic moment does not result from the interactions between several transition metal ions as in molecular nanomagnets but from the photoexcitation of an otherwise diamagnetic molecule. The interest of such a system in terms of QIP is presented and relaxation times and coupling to relevant nuclei are identified.

This Ph.D. thesis describes the versatility of amine triphenolate complexes to be used either as self-assembling molecular scaffolds with applications in material sciences and molecular recognition, like titanium (IV) µ-oxo TPA complexes, or as active catalysts in homogeneous and heterogeneous catalysis, mainly vanadium (V) TPA complexes. In Chapter 1, the principles of self-assembly are listed, i.e. control on the electronic properties and size discrimination for the realization of supramolecular structures, error-checking, and efficiency, in the way of building up ordered and highly-structured entities under mild conditions. Different examples are proposed, but the analysis is mainly focused on the possibility of applying self-assembly in metal coordination chemistry in order to design highly ordered and functional systems, that may find applications in catalysis or material sciences. In this view, the coordination chemistry and the behaviour in solution of Ti(IV) TPA complexes are presented and in particular the possibility to switch between mononuclear and dinuclear µ-oxo species, depending on the steric nature of peripheral substituents, as well as the feasibility to build up highly functional Ti(IV) molecular scaffolds. A brief introduction on V(V) TPA complexes is reported as well, especially on their Lewis acid nature and structural characteristics that make them be considered as functional models of natural vanadium-dependent haloperoxidases and be used as active catalysts in oxygen transfer reactions. As the realization of new efficient and functional supramolecular systems supposes the design of the right building blocks, in Chapter 2, the modification of amine triphenolate skeleton is proposed. The functionalization strategy that has been adopted is based on a click-type oxime bond formation upon reaction of an aldehyde group, which can be effectively and selectively inserted on TPA ligands through the so-called Duff reaction, and a wide variety of alkoxyamines. In this way, the ligand skeleton has been efficiently decorated with polar and positively charged moieties, such as TEG arms and imidazolinium residues, and with pyrene groups. The functionalization has interested diverse positions of the ligand and even a double functionalization of two different positions on the same tri-phenolamine can be achieved. Chapter 3 deals with titanium (IV) amine triphenolate complexes and with the thermodynamic stability in solution of a Ti(IV) complex obtained by complexation with tris-(2-hydroxy-3-phenylbenzyl)amine. In more details, the reaction gives rise to a mononuclear complex, which upon reaction with water stereoselectively self-assembles into a highly stable, inert, dinuclear, heterochiral S6-symmetric µ-oxo TPA complex. Highly decorated Ti(IV) µ-oxo TPA complexes can be efficiently obtained by effecting the complexation reaction on functionalized ligands reported in Chapter 2, or by directly functionalizing Ti(IV) µ-oxo TPA complexes, which bear six aldehyde groups in para and/or meta positions, with the appropriate alkoxyamine. The functionalization strategy enables to construct stable and spatially ordered materials. In particular, two different Ti(IV) µ-oxo TPA complexes, bearing pyrene groups in para and meta positions, respectively, have been used as molecular receptors for fullerene. Fluorescence spectroscopies and DOSY-NMR analyses clearly indicate that pyrene groups on titanium complexes interact with fullerene through π-π interactions. Additionally, interactions between pyrene groups in para position on Ti(IV) µ-oxo TPA complex and SWCNTs (single walled carbon nanotubes) has been studied as well. Even in this case, fluorescence studies have been carried out and AFM images clearly show that CNTs are covered from Ti(IV) µ-oxo TPA complexes, highlighting the possibility to use such these systems for the design of ordered and functional supramolecular structures. Finally, in Chapter 4, the catalytic activity of V(V) TPA complexes is studied, both in sulfoxidation and aerobic oxidative C-C cleavage reactions. Firstly, the activity of an electron-poor V(V) TPA complex, bearing six chloro groups in ortho and para positions, is investigated in sulfoxidation reactions in presence of hydrogen peroxide as terminal oxidant. The reactions are performed with high yields and selectivities (catalyst loading down to 0.001% and TONs up to 89000). Both reaction rates and selectivities confirm the higher activity of the new catalyst with respect to the ones reported in literature. Moreover, modification of V(V) complexes through oxime bond formation has also led to the realization of organogelator-derived complexes, which have been found to form organogels in dioxane. Lastly, functionalization of V(V) complexes with positively charged moieties makes it possible to obtain water-soluble micelles, upon solubilisation with SDS (sodium dodecyl sulphate). The micellar like system has been tested in aerobic oxidative C-C cleavage of vicinal diols, with high selectivity and quite short reaction times. The compartmentalization of the catalytic system allowed its recycling and reuse for three times by extraction of products with organic solvents.
Questa tesi di dottorato descrive la sintesi e la funzionalizzazione di complessi amminotrifenolati di titanio (IV) e vanadio (V) per applicazioni in reazioni di riconoscimento molecolare e in catalisi. Nel Capitolo 1, sono illustrati i principi che regolano il self-assembly, quali controllo, correzione degli errori ed efficienza. E’ mostrato come questi possano essere applicati per la realizzazione di entità ordinate e strutturate in chimica di coordinazione, per la costruzione di sistemi metallo-supramolecolari, con applicazione in catalisi o scienze dei materiali. In quest’ottica, sono studiati la chimica di coordinazione e il comportamento in soluzione di complessi TPA di titanio (IV) e in particolare la capacità di fornire specie mono- o dinucleari a seconda dell’ingombro sterico dei sostituenti periferici e la possibilità di costruire scaffolds molecolari di titanio (IV) altamente funzionalizzati. Inoltre, è riportata una breve introduzione sui complessi TPA di vanadio (V), in particolar modo sulla loro proprietà di acidi di Lewis e sulle loro caratteristiche strutturali, che fanno sì che vengano considerati dei modelli funzionali delle aloperossidasi naturali vanadio-dipendenti e quindi vengano utilizzati come catalizzatori in reazioni di trasferimento di ossigeno. Nel Capitolo 2, viene proposta una strategia sintetica per modificare lo scheletro trifenolamminico. La funzionalizzazione prevede la formazione di un legame ossimico, mediante una reazione click-simile tra un’aldeide, che può essere selettivamente introdotta sul legante mediante reazione di Duff, e una varietà di alcossiammine. In questo modo, lo scheletro del legante può essere efficientemente decorato con residui polari e carichi positivamente, come residui TEG o imidazolinio, e con gruppi pirene. La funzionalizzazione può coinvolgere diverse posizioni del legante, così come una doppia derivatizzazione di posizioni differenti sulla stessa trifenolammina. Nel Capitolo 3, è presentata la possibilità di ottenere dei complessi dinucleari µ-oxo amminotrifenolati di titanio (IV) per reazione di complessazione della tri-(2-idrossi-3-fenilbenzil)ammina con Ti(Oi-Pr)4. Più in dettaglio, il complesso mononucleare, che si forma dalla reazione, in presenze di tracce d’acqua è in grado di auto-assemblarsi in maniera stereoselettiva, dando origine a un complesso dinucleare, altamente stabile, inerte, eterochirale, con simmetria S6. La funzionalizzazione del complesso può essere ottenuta efficacemente mediante una duplice via: effettuando la reazione di complessazione sui leganti funzionalizzati riportati in Capitolo 2, oppure funzionalizzando direttamente complessi TPA µ-oxo di titanio (IV), che portano sei gruppi aldeidici in para e/o meta, con un’appropriata alcossiammina. La strategia di funzionalizzazione permette di costruire dei materiali stabili e spazialmente ordinati. In particolare, due complessi µ-oxo di titanio che portano gruppi pirene rispettivamente in para e meta sono stati utilizzati come recettori molecolari per il fullerene. Spettroscopie di fluorescenza ed esperimenti DOSY-NMR indicano chiaramente che i gruppi pirene sui complessi di titanio interagiscono con il fullerene mediante interazioni π-π. Come ulteriore applicazione, sono state studiate le interazioni tra gruppi pirene dei complessi TPA µ-oxo di titanio e nanotubi di carbonio (SWCNTs). Anche in questo caso, sono stati condotti studi di fluorescenza e analisi AFM mostrano chiaramente che i nanotubi sono rivestiti dai complessi di titanio, evidenziando la possibilità di usare questi sistemi per generare strutture supramolecolari ordinate e funzionali. Infine, nel Capitolo 4, è studiata l’attività catalitica di complessi TPA d vanadio (V), sia in reazioni di solfossidazione che in reazioni di cleavage aerobico ossidativo di legami C-C. Prima di tutto, viene analizzata l’attività catalitica di un complesso di vanadio (V) elettron-povero, portante sei atomi di cloro in posizioni orto e para, in reazioni di solfossidazione in presenza di perossido d’idrogeno come ossidante terminale. Le reazioni sono condotte con alte rese e selettività, anche in presenza dello 0.001% di catalizzatore, con TON fino a 89000. Le velocità di reazione e le selettività confermano una attività maggiore del catalizzatore rispetto ai catalizzatori riportati in letteratura. In più, la modificazione di complessi TPA di vanadio (V) mediante formazione di un’ossima ha portato anche alla realizzazione di complessi funzionalizzati con catene organogelator e alla formazione di organogel in diossano. In conclusione, la funzionalizzazione di complessi TPA di vanadio (V) con residui carichi positivamente permette di ottenere micelle solubili in acqua, in seguito a solubilizzazione con SDS (sodio dodecil solfato). Il sistema micellare è stato poi testato in reazioni di cleavage aerobico ossidativo di legami C-C di dioli vicinali, con elevate selettività e tempi di reazione relativamente bassi. Il sistema catalitico può essere inoltre riciclato e riutilizzato fino a tre volte in seguito a estrazione dei prodotti con solventi organici

Organic-inorganic nanostructured composites are nowadays integrated in the field of material science and technology. They are used as advanced materials directly or as precursors to novel composites with potential applications in optics, mechanics, energy, catalysis and medicine. Many properties of these complex materials depend on conformational rearrangements in their inherently dynamic organic parts. The focus of this thesis is on the study of the molecular mobility in ordered nanostructured composites and lyotropic mesophases and also on the development of relevant solid-state NMR methodologies. In this work, a number of new experimental approaches were proposed for dipolar NMR spectroscopy for characterizing molecular dynamics with atomic-level resolution in complex solids and liquids. A new acquisition scheme for two-dimensional dipolar spectroscopy has been developed in order to expand the spectral window in the indirect dimension while using limited radio-frequency power. Selective decoupling of spin-1 nuclei for sign-sensitive determination of the heteronuclear dipolar coupling has been described. A new dipolar recoupling technique for rotating samples has been developed to achieve high dipolar resolution in a wide range of dipolar coupling strength. The experimental techniques developed herein are capable of delivering detailed model-independent information on molecular motional parameters that can be directly compared in different composites and their bulk analogs. Solid-state NMR has been applied to study the local molecular dynamics of surfactant molecules in nanostructured organic-inorganic composites of different morphologies. On the basis of the experimental profiles of local order parameters, physical motional models for the confined surfactant molecules were put forward. In layered materials, a number of motional modes of surfactant molecules were observed depending on sample composition. These modes ranged from essentially immobilized rigid states to highly flexible and anisotropically tumbling states. In ordered hexagonal silica, highly dynamic conformationally disordered chains with restricted motion of the segments close to the head group have been found. The results presented in this thesis provide a step towards the comprehensive characterization of the molecular states and understanding the great variability of the molecular assemblies in advanced nanostructured organic−inorganic composite materials.

QC 20150225

Le couplage covalent de précurseurs moléculaires spécialement conçus, assisté par une surface métallique, a récemment émergé comme nouvelle voie pour la création de nouvelles architectures moléculaires prometteuses pour l’électronique moléculaire. Les phtalocyanines et leurs dérivés ont attiré beaucoup d’intérêt à cause de leurs propriétés chimiques et optoélectroniques. Dans cette thèse la synthèse de composés de phtalocyanine est présentée. Les composés sont obtenus par une réaction en surface entre précurseurs fonctionnalisés avec quatre groupements carbonitriles et des atomes métalliques. L’étude expérimentale est faite par microscopie à effet tunnel et spectroscopie de photoémission X. Les précurseurs moléculaires de TCN-DBTTF et de PPCN ont été étudiés. Les TCN-DBTTF ont été déposés avec les atomes de Mn, Fe ou Cu sur Ag(111) et Au(111). La réaction de cyclotetramerization a été activée par recuits. Dans le cas le plus favorable (TCN-DBTTF avec Fe sur Ag(111)), la réaction peut être activée à 200°C et permet la synthèse de phtalocyanines individuelles. Un recuit à plus haute température permet de continuer la réaction en 1D (250°C) et en 2D (275°C). Des résultats similaires ont été obtenus pour le dépôt de PPCN avec Mn ou Cu sur Au(111). L’évolution des spectres des niveaux de coeur permet d’obtenir une preuve de la réaction. Les différents facteurs qui influencent la cyclotetramerisation ont été étudiés.L'étude démontre la versatilité de la méthode: la synthèse en surface permet la création de polymères 2D originaux connectés par des macrocycles de phtalocyanine susceptibles d’être étendus à un grand nombre de précurseurs et d’atomes métalliques
Surface-assisted covalent coupling of suitably designed molecular precursors on metal surfaces has recently emerged as a new route towards the design of novel molecular architectures promising for future applications. Phthalocyanines and their derivatives have been widely studied for their chemical and optoelectronic properties. In this thesis the synthesis of phthalocyanine compounds is presented. The compounds are obtained through an on-surface reaction between tetracarbonitrile-functionalized precursors and metals. The experimental investigation is carried out by means of scanning tunnelling microscopy and X-Ray photoemission spectroscopy. Two molecular precursors, TCN-DBTTF and PPCN, are studied. TCN-DBTTF molecules are deposited with metal atoms (Mn, Fe, or Cu) on Ag(111) and Au(111). Annealing is used to activate the reaction of cyclotetramerization between precursors and metals. In the most favourable case (TCN-DBTTF with Fe on Ag(111)) the reaction can be activated at 200°C and leads to the synthesis of individual phthalocyanines. Increasing the temperature allows the synthesis of polymeric lines, at 250°C, and small 2D domains, at 275°C. Similar results are obtained for PPCN deposition with Mn or Cu on Au(111). In this latter case, the evolution of core level spectra allows a chemical proof of the on-surface reaction. The factors affecting on-surface cyclotetramerization have also been studied. This study demonstrates the versatility of the method: on-surface cyclotetramerization allows creating original 2D polymers connected by phthalocyanine macrocycles, and may work with a wide range of tetracarbonitrile-functionalized precursors and metallic atoms

Orientador: Prof. Dr. Wendel Andrade Alves
Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2016.
O consumo de produtos eletrônicos pela sociedade provoca forte impacto ambiental no momento de descartar tais eletrônicos. Neste contexto, a busca por materiais ambientalmente amigáveis está alinhada às necessidades de nosso tempo. Nanoestruturas peptídicas derivadas de aminoácidos naturais possuem grande potencial para a fabricação de uma nova geração de dispositivos biodegradáveis, utilizando a rota de síntese de baixo para cima, sem a necessidade de caros processos litográficos. Neste trabalho, nanomateriais peptídicos foram utilizados tanto em sua forma pura quanto modificados com polímeros para a criação de dispositivos eletrônicos. Os efeitos da auto-organização das nanoestruturas sobre o desempenho e eficiência desses dispositivos foram investigados. Transistores orgânicos de efeito de campo (OFETs) baseados no dipeptídeo L,L-difenilalanina foram desenvolvidos pela primeira vez, tendo apresentado razões on/off e mobilidades da ordem de 103 e de 10-3 cm2 Vs-1. Esses valores são bastante promissores na busca de componentes eletrônicos que atendam às necessidades de desempenho atuais. Um diodo orgânico emissor de luz (OLED) também foi fabricado utilizando as nanoestruturas peptídicas de L,L-difenilalanina modificadas com o polímero emissor poli[2,7-(9,9-dioctilfluoreno)]. Embora o dispositivo tenha apresentado eficiência cerca seis vezes menor comparado ao sistema produzidos com o polímero puro, a introdução de peptídeos permitiu o uso de uma quantidade menor de polímero, além de exibir taxas de biodegradabilidade cerca de 85% maiores. A integração de nanoestruturas de peptídeos com dispositivos de eletrônica orgânica pode significar o início do desenvolvimento de materiais biodegradáveis para aplicação em dispositivos com alta demanda de consumo, tendo como consequência a diminuição do impacto ambiental proveniente da utilização destes dispositivos.
The consumption of electronic products in our society leads to strong environmental impact when such devices need to be discarded. In this sense, research on environmental friendly materials is aligned with the needs of our time. Peptide nanostructures derived from natural amino acids have great potential for producing a new generation of biodegradable devices using the "bottom-up" synthesis route without need for expensive lithographic processes. In this work, peptide nanomaterials were used either in pure form or modified with polymers for designing organic electronic devices and the effects of self-organization on performance and efficiency of these devices were investigated. Organic field effect transistors (OFETs) based on the dipeptide L-L-diphenylalanine were developed for the first time, exhibiting on/off and mobility values of the order of 103 and of 10-3 cm2 Vs-1. These values are very promising and meet the current performance needs in organic devices. An organic light emitting diode (OLED) was fabricated using a combination of peptide nanostructures and 9,9-dioctylfluorene emitting polymer. Although this device shows efficiency six times lower than those build up from pure polymer, they required a lower amount of polymer in the hybrid material and exhibited biodegradability rates ~ 85% higher than architectures exclusively based on pristine polymer. Integration of peptide nanostructures with organic electronic devices represent a milestone on developing biodegradable materials for use in devices with high demand in our society, resulting in reduced environmental impact.

This thesis describes studies on nanohybrid systems consisting of single-walled carbon nanotubes (SWNTs) with monolayer coatings of semiconducting polymers. Steady-state and time-resolved optical and high-resolution microscopy experiments were used to investigate the blends. These materials show promise for use in organic photovoltaics (OPVs) owing to the high carrier mobilities and large aspect ratios of SWNTs, the controllable solubilisation of tubes with various polymers and the broad light-harvesting abilities of organic polymers. Chapters 1 and 2 introduce the theory and background behind the work and present a literature review of previous work utilising carbon nanotubes in OPV devices, revealing poor performances to date. The experimental methods used during the thesis are detailed in Chapter 3 and the solution processing techniques used to prepare the polymer–nanotube blend samples are described in Chapter 4. Chapter 5 describes a study on a nanotube blend with a thiophene polymer, a system previously unsuccessfully implemented into OPV devices. Ultrafast spectroscopic measurements showed that electrons can transfer on a 400 fs time scale from the polymer to nanotubes and the conditions to allow long-lived free charges to be produced were found. The study is extended in Chapter 6 to show that nanostructures consisting of a nanotube coated in one polymer can then be coated by a second polymer and that these nano-engineered structures could be implemented into OPV devices. The use of a competition binding process to isolate purely semiconducting nanotubes dispersed with any desired polymer is then described in Chapter 7. Finally, Chapter 8 introduces systems consisting of chains of porphyrin units, nature’s light-harvesting systems, bound to nanotubes and the blends were found to exhibit the required electronic alignment for use in OPVs. The work described in this thesis provides an explanation for the poor device behaviour of nanotube–polymer blends to date and, in particular, demonstrates several nanohybrid systems that show particular promise for improved OPV applications.

During the attempts to carry out Suzuki coupling reactions, the σ-bonded Pd−Caryl benzochalcogenadiazolyl complexes trans-[ClPd(PPh3)2(C6H2BrN2E)] (E = S, Se) were isolated. The corresponding bromo derivatives were also synthesized on purpose to investigate their activity in Stille coupling reactions. A head-to-tail dimer trans- [{ClPd(PPh3)(μ-C6H2BrN2Se)}2] was synthesized from the thermolysis of trans- [ClPd(PPh3)2(C6H2BrN2Se)] in the presence of SeO2. The reduction potentials of the mononuclear and dinuclear complexes were measured by cyclic voltammetry (CV) and square wave voltammetry (SWV). 4,7-bis(2/4-pyridyl)benzochalcogenadiazole ligands were synthesized by Stille coupling reactions and the 1,5-bis(4-pyridyl)naphthalene ligand was prepared by a Suzuki coupling reaction. Reactions of the labile complex [BrRe(CO)4(NCMe)] with 4,7-bis(4- pyridyl)benzochalcogenadiazole ligands in a 2:1 ratio afforded self-assembled molecular rods [{ReBr(CO)4}2(μ-4,7-bis(4-pyridyl)benzochalcogenadiazoles)]. Palladium directed molecular squares [(enPd)(μ-4,7-bis(4-pyridyl)benzochalcogenadiazole)]4[PF6]8 were prepared by reactions of enPd(PF6)2 and 4,7-bis(4-pyridyl)benzochalco-genadiazoles in a 1:1 ratio. The optoelectronic properties of the ligands and the molecular rods were investigated by CV and SWV, and by luminescence spectroscopy. The optical properties of the square complexes were also studied by luminescence spectroscopy.
xvii, 152 leaves : ill. (some col.) ; 29 cm

This dissertation presents the investigation of magnetic exchange and anisotropy in novel metal-organic complexes containing minimum number of magnetic ions. Such complexes can serve as a model system to understand the exciting magnetic phenomena in such class of materials and also can put forward as candidates for the so called molecular nanomagnets. A direct assessment of the effective magnetic moment and the effective interaction between the metal ions in the complex can be done using magnetization measurements. Here the magnetization studies are performed as a function of temperature and field using a SQUID magnetometer. Yet another powerful tool to characterize and determine the spin levels, the ESR spectroscopic methods, has also been exploited. The study of the dynamical properties of this class of materials was relevant to understand the relaxation mechanism in the low temperatures. For this a new ac susceptometer has been built in house which was another main objective of this dissertation work. The design, fabrication, calibration and automation done on this device is presented in this thesis. The device has been tested using the known molecular magnet Mn12 acetate, and the antiferromagnet Dy2PdSi3. The present work is mainly focused on the magnetic properties of Mn, Ni and Fe based organometallic complexes. The studied Mn dimer with different acceptor and donor ligands exhibit the fine tuning of the electron density at the core of molecular complex by variation in ligands. This in turn shows that the change in peripheral ligands can control the magnetism of the molecule. The influence of the change in Ni-S-Ni bond angle in the magnetic exchange interaction is studied in a Ni(2) dimer and a Ni(2) trimer complex. The Ni dimer complex shows a ferromagnetic interaction (J = -42K) whereas trimer shows an antiferromagnetic interaction (J = 140K). Another Ni based complex bridged via phosphorous has been studied which shows the existence of glassy nature at low temperature. Also a polymeric chain compound based on Fe is studied and presented. All these phosphorous or sulphur bridged complexes are novel materials and these are the first data on these complexes.

[ES] La presente tesis doctoral titulada "New nanostructured suports with signal amplification features for the detection of molecules and biomolecules of interest" se centra en el diseño y preparación de nuevos materiales híbridos orgánicos-inorgánicos constituidos por puertas moleculares soportadas sobre alúmina mesoporosa con el objetivo de desarrollar nuevos sistemas sensores con aplicaciones potenciales en el campo de la diagnosis y del control alimentario. En el primer capítulo de la tesis se introducen los conceptos en los que están basados los estudios realizados y los materiales preparados. A continuación, en el segundo capítulo se describen los objetivos generales de la tesis que serán abordados en los siguientes apartados. En el tercer capítulo se presenta el diseño y optimización de un nanodispositivo para la detección de la bacteria Mycoplasma fermentans. En primer lugar, los poros de una placa de alúmina mesoporosa se cargan con un indicador fluorescente (rodamina B). Seguidamente, la superficie es funcionalizada con una secuencia de ADN complementaria a una región altamente conservada de la subunidad ribosomal 16S de la bacteria Mycoplasma fermentans. El impedimento estérico generado por las secuencias de ADN ancladas al exterior de los poros impide la salida del indicador encapsulado. Únicamente en presencia de DNA de la bacteria Mycoplasma fermentans, se produce la apertura de los poros permitiéndose la difusión de la carga (rodamina B) que es posteriormente medida mediante espectroscopía de fluorescencia. En el capítulo cuatro se diseña de un nanodispositivo capaz de detectar de forma rápida, sensible y selectiva la bacteria Staphylococcus aureus. Para la preparación del material sensor, un soporte de alúmina mesoporosa es, en primer lugar, cargado con el indicador fluorescente rodamina B. A continuación, los poros del soporte son tapados mediante el anclaje de un aptámero que reconoce de forma específica la bacteria. Solamente en presencia de Staphylococcus aureus se produce la liberación del indicador encapsulado, que es posteriormente medido mediante espectroscopía de fluorescencia. Además, la respuesta obtenida es específica para Staphylococcus aureus. Este sistema ha sido ensayado en muestras reales. En el sexto capítulo, diseña un nanodispositivo híbrido orgánico-inorgánico consistente en un material de alúmina mesoporosa cubierto con una secuencia de ADN específica para la detección de ADN del hongo Pneumocystis jirovecii. En este caso, el soporte de alúmina cargado con rodamina B se recubre con una secuencia de ADN específica para el reconocimiento de este hongo. En presencia del organismo, la horquilla hibrida con el ADN del hongo, lo que resulta en una conformación triplex con elevada afinidad y estabilidad que induce, al mismo tiempo, el desplazamiento de este complejo de la superficie. Como consecuencia de este reconocimiento la carga se libera y es cuantificada mediante espectroscopía de fluorescencia. El sistema ha sido satisfactoriamente validado. En el séptimo capítulo, se diseña un sistema sensor con la capacidad de detectar gluten de forma rápida y sencilla en extractos de alimentos procesados y no procesados. Para ello, un soporte de alúmina mesoporosa se carga con rodamina B y los poros se recubren con un aptámero específicamente diseñado para la detección de la proteína gliadina, que constituye el 50 % del total del clúster de elementos que forman el gluten. La elevada afinidad y especificidad entre el aptámero y la proteína en cuestión hacen que en presencia de ésta se produzca un desplazamiento de la puerta molecular que permite la difusión del colorante encapsulado que es finalmente monitorizado mediante espectroscopía de fluorescencia. Finalmente, en el capítulo octavo se discuten de forma conjunta los resultados obtenidos en los capítulos anteriores y la potencial aplicación de los sistemas desarrollados en el actual sistem
[CA] La present tesi doctoral, titulada "New nanostructured supports with signal amplification features for the detection of molecules and biomolecules of interest", es centra en el disseny i preparació de nous materials híbrids orgànics-inorgànics constituïts per portes moleculars suportades sobre alúmina mesoporosa amb l'objectiu de desenvolupar nous sistemes sensors amb potencials aplicacions en el camp de la diagnosi i del control alimentari. En el primer capítol de la tesi s'introdueixen els conceptes en què estan basats els estudis realitzats i els materials preparats. A continuació, en el segon capítol es descriuen els objectius generals de la tesi que seran abordats en els següents apartats. En el tercer capítol es presenta el disseny i optimització d'un nanodispositiu per a la detecció de la bactèria Mycoplasma fermentans. Primerament, els porus d'una placa d'alúmina mesoporosa són carregats amb un indicador fluorescent (rodamina B). Seguidament, la superfície és funcionalitzada amb una seqüència d'ADN complementaria a una regió altament conservada de la subunitat ribosomal 16S de la bactèria Mycoplasma fermentans. L'impediment estèric generat per les seqüències d'ADN ancorades a l'exterior dels porus impedeix l'alliberament de l'indicador encapsulat. Únicament en presencia d'ADN de la bactèria Mycoplasma fermentans, es produeix l'obertura dels porus permetent la difusió de la càrrega (rodamina B) que és posteriorment mesurada mitjançant fluorescència. En el capítol quatre es dissenya un nanodispositiu capaç de detectar de forma ràpida, sensible i selectiva la bactèria Staphylococcus aureus. Per a la preparació del material sensor, el suport d'alúmina mesoporosa és, primerament, carregat amb l'indicador fluorescent rodamina B. A continuació, els porus del suport són tapats mitjançant l'ancoratge d'un aptàmer que reconeix de forma específica a la bactèria. Solament en presència de Staphylococcus aureus es produeix l'alliberament de l'indicador encapsulat, que és posteriorment mesurat mitjançant espectroscòpia de fluorescència. A més a més, la resposta obtinguda és específica per Staphylococcus aureus. Aquest sistema ha sigut validat amb mostres reals de pacients. En el sisè capítol, es dissenya un nanodispositiu híbrid orgànic-inorgànic consistent en un material d'alúmina mesoporosa cobert amb una seqüència d'ADN específica per a la detecció de l'ADN del fong Pneumocystis jirovecii. En aquest cas, el suport d'alúmina carregat amb l'indicador fluorescent rodamina B és recobert amb una seqüència d'ADN específica per al reconeixement d'aquest fong. En presència de l'organisme, la forquilla hibrida amb l'ADN del fong, resultant en una conformació triplex amb elevada afinitat i estabilitat, que indueix, al mateix temps, el desplaçament d'aquest complex de la superfície. Com a conseqüència d'aquest reconeixement la càrrega és alliberada i quantificada mitjançant espectroscòpia de fluorescència. El sistema ha sigut validat com a mètode diagnòstic mitjançant l'anàlisi de mostres reals de pacients. En el seté capítol, es dissenya un sistema sensor amb la capacitat de detectar gluten de forma ràpida i senzilla en extractes d'aliments processats i no processats. Per a això, un suport d'alúmina mesoporosa es carrega amb indicador fluorescent rodamina B i posteriorment és recobert amb un aptàmer específicament dissenyat per a la detecció de la proteïna gliadina, que constitueix el 50 % del total del clúster d'elements que formen el gluten. L'elevada afinitat i especificitat entre l'aptàmer i la proteïna en qüestió fa que en presència d'aquesta es produesca un desplaçament de la porta molecular que permet la difusió de la càrrega encapsulada i que serà finalment monitoritzada mitjançant espectroscòpia de fluorescència. Finalment, en el capítol vuité es discuteixen de manera conjunta els result
[EN] The PhD thesis hereby presented and entitled "New nanostructured supports with signal amplification features for the detection of molecules and biomolecules of interest", focuses in the design and preparation of new hybrid organic-inorganic materials constituted by molecular gates supported over mesoporous alumina with the aim of developing new sensor probes of potential applications in the fields of diagnosis and food control. In the first chapter, the concepts in which studies and prepared materials are based, are introduced. Next, the second chapter describes the general objectives of this thesis, which will be approached in the following sections. In the third chapter, it is presented in detail the design and optimization process of a nanodevice applied for the detection of Mycoplasma fermentans bacterium. First of all, mesoporous alumina porous films are charged with a fluorescent indicator (rhodamine B). Then, the surface is functionalized with a DNA sequence complementary to a highly conserved region of the 16S ribosomal subunit of the bacterium Mycoplasma fermentans. Steric hindrance generated by DNA sequences on the surface inhibits the release of the encapsulated indicator. Only in the presence of bacterium Mycoplasma fermentans DNA, molecular gates open, allowing payload diffusion to the solution, which is measured by fluorescence spectroscopy. In chapter four, it is carried out the design and optimization of a nanodevice able to detect Staphylococcus aureus bacterium in a fast, sensitive and selective way. For the sensor preparation, alumina mesoporous support is, first, loaded with the rhodamine B fluorescent dye. Then, the mesoporous are blocked through the attachment of an aptamer that recognises specifically this bacterium. Exclusively in the presence of Staphylococcus aureus it is accomplished the release of the encapsulated dye, which is later monitored by fluorescence spectroscopy. The response obtained is specific for Staphylococcus aureus. This system has been validated in real samples. In the sixth chapter, it is detailed the design and optimization process of a hybrid organic-inorganic nanodevice based on a capped mesoporous alumina material for the detection of Pneumocystis jirovecii fungus DNA. In this case, the mesoporous alumina support is loaded with a fluorescent dye and decorated with a specific oligonucleotide sequence designed for the recognition of Pneumocystis fungus. In the presence of the target organism, the fork-like oligonucleotide hybridises with the DNA of the fungus, which results in the adoption of a triplex conformation with high affinity and stability that induces, at the same time, the displacement of this complex from the surface. Consequently, the payload diffused to the solution is quantified through fluorescence spectroscopy. The system has been successfully validated. In the seventh chapter, it was developed a sensor system for gluten detection, in a quick and easy way, in processed and non-processed food extracts. For this, a mesoporous alumina support is loaded with the fluorescent dye rhodamine B, and later was functionalized with an aptamer specifically designed for the detection of gliadin, a protein that constitutes 50 % of average cluster elements that forms gluten. The protein-aptamer high affinity and specificity induce the displacement of the capping aptamer and cargo delivery, which is monitored through fluorescence spectroscopy. Finally, in the eighth chapter, the results obtained in the previous chapters and the potential application of the systems developed as health and food control system are discussed.
We thank the Spanish Government projects MAT2015-64139-C4-1-R, AGL2015-70235-C2-2-R, and TEC2015-71324-R (MINECO/FEDER, UE), the Generalitat Valenciana (project PROMETEOII/2014/047), the Catalan authority (project AGAUR 2014SGR1344), and ICREA under the 2014 ICREA Academia Award for support. This study was supported by the Spanish Government projects RTI2018-100910-B-C41 and SAF2017-82251-R (MCUI/AEI/FEDER, UE), the Generalitat Valenciana (project PROMETEO/2018/024), the Universitat Politècnica de València−Instituto de Investigación Sanitaria La Fe (B02-MIRSA project), CIBER-BBN (NANOPATH and valorization project CANDI-EYE) and co-financed by the EU through the Valencian Community ERDF PO 2014-2020. This research was funded by the Spanish Government, projects RTI2018-100910-B-C41 (MCUI/AEI/FEDER, UE) and CTQ2017-84415-R
Pla Blasco, L. (2021). New nanostructured supports with signal amplification features for the detection of molecules and biomolecules of interest [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/166500
TESIS

Les cellules photovoltaïques organiques ont fait l'objet d'un intérêt croissant au cours de ces dernières décennies car elles offrent un grand potentiel pour une production d'énergie renouvelable à faible coût. Afin d'obtenir des cellules solaires organiques à haut rendement de conversion d'énergie, beaucoup de recherches se focalisent sur les matériaux ayant des capacités à absorber la lumière efficacement. Dans ce contexte, le présent travail se concentre sur la conception et le développement de nouveaux matériaux donneurs d'électrons (oligomères et polymères) comme matériaux absorbant de la lumière basée sur l'approche « Donneur-Accepteur » alternant des segments riches en électron (donneur d'électron) et des unités pauvres en électron (accepteur d'électron). Trois séries d'unités riches en électron ont été étudiées: oligothiophènes, fluorène et indacenodithiophene. L'unité fluorénone est la principale unité « accepteur d'électron » étudiée. Une comparaison directe avec le système basé sur l'unité benzothiadiazole comme accepteur d'électron est également rapportée. Trois méthodes principales de synthèse ont été utilisées: polymérisation oxydante par le chlorure de fer (III), et les couplages croisés au palladium de type Suzuki ou de Stille. Les études spectroscopique UV-Visible en absorption et en photoluminescence sur ces oligomères et polymères ont démontré la présence de complexes à transfert de charges permettant d'élargir le spectre d'absorption. Les oligomères et les polymères possèdent des faibles largeurs de bande interdite de 1,6 eV à 2 eV. Les systèmes ayant des unités fluorénones présentent des spectres d'absorption étendus allant jusqu'à 600-700 nm, tandis que les systèmes ayant des unités benzothiadiazoles présentent des spectres d'absorption allant jusqu'à 700- 800 nm. La nature des bandes de complexes à transfert de charge se révèle d'être dépendant de la force de respective des unités « donneur d'électrons » et des unités « accepteur d'électrons ». Les niveaux d'énergies HOMO et LUMO des oligomères et les polymères sont déterminés par des mesures électrochimiques. Les polymères à base de fluorène possèdent des niveaux d'énergie HOMO les plus bas. Ces polymères testés en mélange avec les fullerenes PCBM en cellules photovoltaïques ont démontré des valeurs élevées de tension en circuit ouvert (Voc) proche de 0,9 V. Tous les oligomères et les polymères ont été testés dans des dispositifs photovoltaïques et ont montré des résultats encourageants avec des rendements de conversion allant jusqu'à 2,1 %. Ce sont des premièrs résultats obtenus après seulement quelques optimisations (ratios oligomères ou polymères : fullerènes et recuit thermique). Ce travail prometteur permet ainsi d'envisager des résultats plus élevés dans le futur
Organic photovoltaic (OPV) cells have been a subject of increasing interest during the last decade as they are promising candidates for low cost renewable energy production. In order to obtain reasonably high performance organic solar cells, development of efficient light absorbing materials are of primary focus in the OPV field. In this context, the present work is focused on the design and development of new electron donor materials (oligomers and polymers) as light absorbing materials based on “Donor-Acceptor” approach alternating electron donating group and electron withdrawing group. Three main families of electron donating group are studied: oligothiophenes, fluorene and indacenodithiophene. Fluorenone unit is the principal electron withdrawing group studied and a direct comparison with the system based on benzothiadiazole unit as electron withdrawing unit is also provided. Three main synthetic methods were employed: oxidative polymerization mediated by Iron (III) chloride and Palladium cross-coupling reactions according to Suzuki coupling or Stille coupling conditions. Spectroscopic studies on absorption and photoluminescence have demonstrated the presence of characteristic charge transfer complex in all the studied D-A oligomers and polymers allowing the extension of the absorption spectrum. The D-A oligomers and polymers have shown an overall low optical band gap of 1.6-2 eV with absorption spectra up to 600 to 800 nm. The nature of the charge transfer complex transitions bands were found to be depending on the strength of the electron donating unit and the electron withdrawing unit. Furthermore molecular packing in solution and in solid state has also demonstrated to contribute to extension of absorption spectrum. The HOMO and LUMO energy levels of the oligomers and polymers were determined by electrochemical measurements. Fluorene-based polymers have shown low lying HOMO energy levels, and these polymers demonstrate high open circuit voltage (Voc) in photovoltaic cell when combined with fullerenes derivatives PCBM with Voc values close to 0.9 V. The oligomers and polymers tested in photovoltaic devices have shown promising results with the highest power conversion efficiency obtained of 2.1 % when combined with fullerenes PCBMC70. These results were obtained after only limited numbers of device optimizations such as the active materials ratios and thermal annealing. Therefore further optimization of devices may exhibit higher power conversion efficiencies

This dissertation demonstrates the application of a vapor phase method to synthesize supported and unsupported nanoparticle catalysts for CO oxidation. The method is based on the Laser Vaporization/Controlled Condensation (LVCC) technique. The first part of this dissertation presents the vapor phase synthesis and characterization of gold nanoparticles supported on a variety of oxide supports such as CeO2, TiO2, CuO and MgO.The results indicate that Au nanoparticles supported on CeO2 exhibit higher catalytic activity than Au supported on other oxides. The high activity of the Au/CeO2 catalyst is attributed to the strong interaction of Au with CeO2. The results also indicate that 5% Au loading on CeO2 has higher activity than 2% Au or 10% Au. When comparing the catalytic activity of Au/CeO2 prepared by physical (LVCC) and chemical (deposition-precipitation)methods, it was found that the catalytic activity is higher for Au/CeO2 prepared by the deposition-precipitation method.The effect of alloying Au and Cu nanoparticles on the catalytic activity for low temperature CO oxidation was also investigated. The unsupported Au-Cu alloy nanoparticle catalyst exhibits higher catalytic activity than the activities of the individualcomponents and their physical mixtures. The XRD data of Au-Cu alloy taken after the catalysis test indicates the formation of CuO within the bimetallic nanoparticles, whichimproves the catalytic activity of Au-Cu alloy nanoparticle.The second part of this dissertation investigates the gas phase reactions of Au+ and Cu+ with CO, O2 and H2O molecules using the Laser Vaporization ionization, High-Pressure Mass Spectrometry (LVI-HPMS) technique. The gas phase reactions resulting from the interactions of Au+ with CO and O2 molecules are investigated. Although multiple additions of CO and O2 molecules on Au+ have been observed at room temperature, no evidence was found of the production of CO2. This is attributed to the presence of water molecules which effectively replace the oxygen molecules on Au+ at room temperature.Finally, the role of the metal cations Au+ and Cu+ in initiating the gas phase polymerization of butadiene and isoprene vapors was investigated.

The very large number of distinct structures that are known for metal-organic frameworks (MOFs) and zeolites presents both an opportunity and a challenge for identifying materials with useful properties for targeted separations. In this thesis we propose a three-stage computational methodology for addressing this issue and comprehensively screening all available nanoporous materials. We introduce efficient pore size calculations as a way of discarding large number of materials, which are unsuitable for a specific separation. Materials identified as having desired geometric characteristics can be further analyzed for their infinite dilution adsorption and diffusion properties by calculating the Henry's constants and activation energy barriers for diffusion. This enables us to calculate membrane selectivity in an unprecedented scale and use these values to generate a small set of materials for which the membrane selectivity can be calculated in detail and at finite loading using well-established computational tools. We display the results of using these methods for >500 MOFs and >160 silica zeolites for spherical adsorbates at first and for small linear molecules such as CO₂ later on. In addition we also demonstrate the size of the group of materials this procedure can be applied to, by performing these calculations, for simple adsorbate molecules, for an existing library of >250,000 hypothetical silica zeolites. Finally, efficient methods are introduced for assessing the role of framework flexibility on molecular diffusion in MOFs that do not require defining a classical forcefield for the MOF. These methods combine ab initio MD of the MOF with classical transition state theory and molecular dynamics simulations of the diffusing molecules. The effects of flexibility are shown to be large for CH₄, but not for CO₂ and other small spherical adsorbates, in ZIF-8.

Distillation and absorption columns offer significant energy demands for future development in the petrochemical and fine chemical industries. Membranes and adsorbents are attractive alternatives to these classical separation units due to lower operating cost and easy device fabrication; however, membranes possess an upper limit in separation performance that results in a trade-off between selectivity (purity) and permeability (productivity) for the target gas product, and adsorbents require the need to be water-resistant to natural gas streams in order to withstand typical gas compositions. Composite membranes, or mixed-matrix membranes, are an appealing alternative to pure polymeric membrane materials by use of a molecular sieve “filler” phase which has higher separation performance than the pure polymer. In this thesis, the structure-property-processing relationships for a new class of molecular sieves known as zeolitic imidazolate frameworks (ZIFs) are investigated for their use as the filler phase in composite membranes or as adsorbents. These materials show robust chemical and thermal stability and are a promising class of molecular sieves for acid gas (CO₂/CH₄) separations. The synthesis of mixed-linker ZIFs is first investigated. It is shown that the organic linker composition in these materials is controllable without changing the crystal structure or significantly altering the thermal decomposition properties. There are observable changes in the adsorption properties, determined by nitrogen physisorption, that depend on the overall linker composition. The results suggest the proposed synthesis route facilitates a tunable process to control either the adsorption or diffusion properties depending on the linker composition. The structure-property-processing relationship for a specific ZIF, ZIF-8, is then investigated to determine the proper processing conditions necessary for fabricating defect-free composite membranes. The effect of ultrasonication shows an unexpected coarsening of ZIF-8 nanoparticles that grow with increased sonication time, but the structural integrity is shown to be maintained after sonication by using X-ray diffraction, Pair Distribution Function analysis, and nitrogen physisorption. The permeation properties of composite membranes revealed that intense ultrasonication is necessary to fabricate defect-free membranes for CO₂/CH₄ gas separations. Finally, the separation properties of mixed-linker ZIFs is investigated by using adsorption studies of CO₂ and CH₄ and using composite membranes with differing linker compositions. Adsorption properties of mixed-linker ZIFs reveal that these materials possess tunable surface properties, and a selectivity enhancement of six fold over ZIF-8 is observed with mixed-linker ZIFs without changing the crystal structure. Gas permeation studies of composite membranes reveal that the separation properties of mixed-linker ZIFs are different from their parent frameworks. By proper selection of mixed-linker ZIFs, there is an overall improvement of separation properties in the composite membranes when compared to ZIF-8.

Ce travail porte sur la synthèse et la caractérisation de matériaux moléculaires fonctionnels basés sur la molécule anilate et présentant des propriétés de conductivité, de magnétisme et de luminescence. Les anilates sont des dérivés de la 2,5-dihydroxy-1,4-benzoquinone substitués en positions 3 et 6 par une variété d’éléments (H, F, Cl, Br, I, CN, etc). Parmi eux, le seul composé hétérosubstitué ClCNAn2- a été choisi pour préparer une nouvelle famille de polymères de coordination bidimensionnels (PC 2D) avec des métaux de transition ou des ions lanthanides : i) un PC à valence mixte FeIIFeIII, de formule [TAG][FeIIFeIII(ClCNAn)3], contient pour la première fois le cation triaminoguanidinium dans un réseau de coordination.ii) Des PC basés sur le ligand ClCNAn2- et des ions lanthanides émettant dans le proche infrarouge (YbIII, NdIII, ErIII). Ces composés ont été exfoliés en monocouches, et des études de photoluminescence ont été menées à la fois sur les cristaux et les monocouches. iii) Une famille de PC hétéroleptiques basés sur des ions lanthanides et sur deux types de ligands pontants, le ligand ClCNAn2- et des ligands de type carboxylates (DOBDC et F4-BDC). iv) Une famille de PC basés sur des ions DyIII ont été préparés afin d’étudier leur propriétés magnétiques. v) Finalement, la capacité des ligands anilates à se combiner à des conducteurs moléculaires basés sur le BEDT-TTF a été démontrée à travers la synthèse et l’électrocristallisation de semiconducteurs organiques et de conducteurs magnétiques hybrides avec l’anion [Fe(ClCNAn)3]3-
This work reports on the design, synthesis and characterization of novel anilate-based functional molecular materials showing luminescent, magnetic and/or conducting properties. The family of anilate ligands comprises several derivatives obtained by introducing various substituents (H, F, Cl, Br, I, CN, etc.) at the 3 and 6 positions of the common 2,5-dihydroxy-1,4-benzoquinone framework. Among the anilate ligands, the only known heterosubstituted anilate with Cl/CN substituents at the 3,6 positions, ClCNAn2-, have been selected for preparing a novel family of 2D layered coordination polymers (2D CP) with both 3d metal ions and 4f lanthanide ions, through a general and straightforward synthetic strategy. i) Mixed-valence FeIIFeIII 2D CP, formulated as [TAG][FeIIFeIII(ClCNAn)3], containing, the tris(amino)-guanidinium (TAG) cation for the first time in such 2D networks has been synthesized and thoroughly characterized. ii) 2D CPs based on NIR-emitting lanthanides (YbIII, NdIII, ErIII) and the ClCNAn2- ligand, have been prepared and characterized. These layered compounds were exfoliated to nanosheets, by sonication-assisted solution synthesis. Time-resolved photoluminescence studies performed on both the bulk and nanosheets are also highlighted. iii) Novel family of heteroleptic 2D CPs based on NIR-emitting lanthanides and mixed ligands (ClCNAn2- and carboxylate ligands (DOBDC and F4-BDC)), were prepared and characterized. vi) Novel family of 2D CPs based on DyIII and ClCNAn2- were prepared in order to investigate their magnetic properties. v) Furthermore, the ability of anilate ligands to work as components of BEDT-TTF- based molecular conductors have been demonstrated through the synthesis, via electrocrystallization technique. vi) П-d hybrid multifunctional paramagnetic molecular conductors BEDT-TTF and [Fe(ClCNAn)3]3-) were also studied

One of the most challenging goals in nanoparticle research is to develop successful protocols for the large-scale, simple and possibly low-cost preparation of morphologically pure nanoparticles with enhanced properties. The work presented in this thesis was focused on the synthesis, characterisation and testing of magnetic nanoparticles and their potential applications. There are a number of magnetic nano-materials prepared for specific applications such as metal oxide nanoparticles encapsulated with various porous materials including Fe₃O₄/Fe₂O₃ coated with soft bio-organic materials such as glycol chitosan and bovine serum albumin and hard materials such as silica (SiO₂) and zinc sulphide (ZnS). The preparation of these materials was achieved principally by bottom-up methods with different approaches including micro-emulsion, precipitation, electrostatic and thermolysis processes. The thesis also presents the uses of various analytical techniques for characterising different types of nano-materials including Attenuated Total Reflection Fourier Transformer Infrared Vibrational Spectroscopy (ATR-FTIR), Ultraviolet Visible- Near Infrared (UV-Vis-NIR) Spectroscopy, Zeta Potentiometric Surface Charge Analysis, Superconducting Quantum Interference Device (SQUID) and Vibration Sample Magnetometry (VSM) for magnetic analysis and powder X-Ray Diffraction (XRD) for crystallographic pattern analysis. There are many applications of magnetic nanoparticles, including nano-carriers for biological and catalytic reagents. The magnetic nanoparticles can facilitate separation in order to isolate the carriers from solution mixtures as compared to many inefficient and expensive classic methods, which include dialysis membrane, electrophoresis, ultracentrifugation, precipitation and column separation methods. There are six key chapters in this thesis: the first chapter introduces the up-to-date literature regarding magnetic nano-materials. The uses of magnetic nano-materials in drug binding and for protein separation are discussed in the second and third chapters. The fourth chapter presents the use of magnetic nanoparticle in conjunction with a photo-catalytic porous overlayer for the photo-catalytic reduction of organic molecules. The fifth chapter describes different analytical techniques used for the characterisation of nanoparticles and the underlying principles and the experimental details are also given. The sixth chapter summarises the results and provides an overview of the work in a wider context of future applications of magnetic nanoparticles.

博士
國立交通大學
材料科學與工程學系
100
In the last 10 years, nanomaterials based on small organic molecules have attracted increasing attention. Such materials have unique optical and electronic properties, which could lead to new applications in nanoscale devices. Besides the strikingly different optoelectronic properties from those of their inorganic counterparts, organic nanomaterials also have some advantages in low-cost, low-temperature processing and mechanical flexibility, which make them complementary to the inorganic materials. The dissertation describes the impact factors on the synthesis of one-dimensional (1D) organic nanostructures with low-temperture processes in an attempt to apply in organic field emitter. All of the organic semiconductor materials investigated in this thesis, display self-assembly aligned nanostructures, in which electrons can emit from the tip of nanostructures at an applied electric field using a vaccum emission measurement system. In the first part of the dissertation, by using 1,5-diaminoanthraquinone (DAAQ) as a starting material, vertical organic nanofibers were prepared through low-temperature (42 °C) vacuum sublimation. The structural morphologies formed from the DAAQ molecules self-assembly stacking were controlled by surface properties of substrates, with vertically alighned 1D nanostructures growing preferentially on low water contact angle surfaces, such as Au, Si, and Ti. On Au and Ti substrates, the DAAQ nanofibers DAAQ-Au and DAAQ-Ti exhibited field emission characteristics, with maximum emission current densities of 0.31 and 0.65 mA/cm2, respectively, at an applied electric field of 12 V/μm. The turn-on electric fields were 8.5 V/μm for DAAQ-Au and 8.25 V/μm for DAAQ-Ti. From the slopes of Fowler-Nordheim plots, we calculated the field enhancement factor (β) of the DAAQ nanofibers on the Au and Ti substrates to be 447 and 831, respectively. In the second part of this dissertation, we devised a simple method for micropatterned growth of iron phthalocaynine (FePc) nanofiber arrays using a thermal evaporation process. By controllong the surface energy and the temperature of the substrate (Tsub), we obtain FePc films featureing a grain-like (in-plane) morphology on Si surfaces (higher surface energy) and a fiber-like (out-of-plane) morphology on Ag surfaces (lower surface energy) within a certain range of values of Tsub. These temperature-induced and well-aligned 1D FePc nanofibers exhibited FE characterisitics and follow FN behavior. Using such morphological control, we grew patterned FePc selectively on previously patterned Ag/Si substrates; moreover, the higher AR of the devices (FE-240-P; Tsub of 240 °C) exhibited better FE performance than lower AR of devices (FE-180-P; Tsub of 180 °C). In the optimal growth condition of Tsub of 240 °C, the emission current of the device improved dramatically from 0.13 mA/cm2 for the unpatterned device to 6.77 mA/cm2 for the patterned device (when biased at an applied field of 12 V/μm), while the turn-on field of the device decreased accordingly from 10.3 to 7.7 V/μm. In FE stability tests, the current densities of FE-240-P exhibited fluctuations of less than 20%, revealing its stable and superior property whin the duration of the measurement process. In the last part of this dissertation, we developed a simple and efficient approach—using graphene coatings on ITO as transparent electrodes—for inducing the growth of 29H,31H-phthalocyanine (H2Pc) nanofiber arrays through a thermal evaporation process, with potential use in organic field emitters (FEs). By controlling the surface energy and temperature of the electrodes during evaporation, H2Pc molecules readily self-assemble, forming an out-of-plane morphology on reduced graphene oxide surfaces (rGO; surface energy: ca. 50 mJ/m2). The devices fabricated on rGO/indium tin oxide (FE-rGO) exhibited not only excellent FE performance but also outstanding anti-degradation capability during stability tests. This facile approach toward rGO coatings opens a new avenue for the transformation of small organic molecules films into vertically standing nanostructures on transparent electrodes, with various organic electronics applications.

碩士
國立臺灣大學
化學研究所
104
In this thesis, we designed and synthesized three emissive fluorene derivatives, T2BUdiC12, BTDFBUdiC12 and TPDFBUdiC12, on which the self-assembling bis-urea motifs were introduced. By the use of electron microscopes (SEM and TEM) and confocal laser scanning microscope (CLSM), the molecules were found to spontaneously assemble into nano-sphere in specific solvent compositions. Furthermore, the selective distribution of bis-urea molecules on patterned substrates was investigated. We immersed patterned silicon wafer substrates into bis-urea nano-spheres solution for several minutes (or dropped-casting the solution onto slides). Under the characterization of SEM and CLSM, bis-urea molecules showed selective distribution to the hydrophobic zones on patterned silicon or slide substrates. Also, we found the tendency of bis-urea molecules to hydrophobic zones could be changed by changing solvent composition or introducing solvent annealing.

碩士
國立清華大學
材料科學工程學系
106
BiFeO3 microparticles with space group of R3c were prepared by hydrothermal process and ball-milled into nanoparticles to proceed with the synthesizing step for heterostructure. BiFeO3/TiO2 core-shell heterostructure was synthesized through a well-adapted sol-gel method. Under synergistic ultrasonification and light irradiation, polarization-enhanced BiFeO3/TiO2 core-shell structured nanocomposites almost achieved 100 % piezo/photo-catalytic degradation ratio for methyl violet dye solution of 10 ppm within 2 h. The synergy of piezo/photo-catalysis outperformed the piezocatalysis by 160 % and the photocatalysis by 220 %. Moreover, the rate constant of it is about 500 % of the piezocatalysis and photocatalysis. The enhanced polarization was realized through the polling process, which took good use of the inherent ferroelectricity. Suitable band structure from the core-shell nanocomposites with high surface area boosts the surface charge transfer and the ultrasonic vibration keeps the field from saturation. These means were employed so as to reduce the recombination probability of the induced carriers, which could subsequently react with the solution to generate powerful oxidizing radicals and further dissociate organic dyes. In the flourescence photoluminescence (FL) analysis, the signals associated to hydroxyl radicals elevate with the increase of both the amount of catalysts and catalytic times. This well corroborates the importance of the powerful oxidizing agents in the degradation process. This work reveals more efficient dye degradation, utilizing polarization enhancement and synergy of mechanical vibration and light irradiation, which provides a new strategy for high performance catalytic applications.

The primary goal of this work was the preparation of new elongated titanate nanoparticles, like nanotubes (TNT) and nanowires (TNW), with improved ability for pollutants adsorption and photo(electro)catalytic degradation. TNT and TNW were prepared using a hydrothermal approach in alkaline medium, starting from TiO2 nanoparticles and amorphous precursors, respectively. The TNT/TNW were modified by ion-exchange and doping with metals (Co, Ru, and Fe/Mn), and by sensitization with Ag nanoparticles and ethylenediamine. The catalytic ability of these new materials for the pollutants photodegradation, including phenol, caffeine, theophylline, and dyes, was also investigated. The results showed that all modified TNT/TNW demonstrated excellent photocatalytic activity for the degradation processes studied. The sensitization process can improve the light absorption on the visible range and the ability for pollutants adsorption and photocatalytic degradation, due to the change imposed on the TNT/TNW surface. The metal modification can impose a light absorption shift to the visible range and/or the introduction of intermediary levels in the forbidden band, reducing the electron-hole (e-/h+) recombination. For the ethylenediamine sensitized samples, it was demonstrated that the N-species improves the photocatalytic activity. The results revealed h+ was mainly responsible for the hydroxyl radical formation, and the production of nitrogen oxidant species was proposed. The results for sensitized samples with Ag nanoparticles, Ag-HTNW, revealed the presence of Ag+ in the interlayers and Ag nanoparticles in the HTNW surface, and the h+ action with highly oxidant species enhances the photocatalytic performance. For the cobalt modified powders, depending on the synthesis methodology and Co/Ti ratio, the dopant can replace Na+ in the interlayers and/or substitute Ti4+ in lattice positions or sit in interstitial sites. The structure and optical behavior are dependent on the metal ions either substituting Ti4+ or replacing Na+. For RuTNW sample, Run+ was detected in the crystalline structure replacing Ti4+ and in the interlayers replacing Na+, and for RuTNT it was only replacing Ti4+. The photocatalytic improvement of these materials was principally to recombination rate reduction, by metal incorporation. The utmost difference between these samples was related to the pollutants’ photodegradation mechanism and intermediates formation/degradation. In this work, the influence of slight metal contaminations on the TNW structural, optical and photocatalytic behavior was also studied. FeMnTNW were obtained due to a reactants’ vestigial contamination. The modification occurred by Ti4+/Fe3+-Mn3+ substitution and by Na+ replacement in the interlayers. The TNW/TNT immobilization in conductive films to be used in pollutants photo(electro)degradation, was also studied. Ru- and Co-modified TNW/TNT were immobilized on a conductive substrate by drop-casting method followed by 1,8- diaminocarbazole electropolymerization and were remarkably effective catalysts in pollutants photo(electro)degradation. The films’ reutilization showed that these are stable and can be used in successive degradation without performance loss.

Availability of appropriate forms of energy is one of the basic needs of the society. The demand for worldwide energy has been increasing, while the conventional energy sources have been depleting fast. As the present main sources are fossil fuels, environmental pollution and its consequences caused by emission from combustion of them has also been a social concern. Thus, exploration of alternate energy sources has become an important area of research and development. Fuel cells are considered to meet a variety of applications. A direct liquid fuel cell (DLFC), which employs a liquid consisting of small organic compound such as methanol as the fuel, is more interesting than the other kinds of fuel cells. In view of this, studies on electrooxidation of organic compounds are important. A suitable catalyst plays an important role on the kinetics of electrooxidation of these compounds. The catalyst needs to exhibit a high activity, economical and stable over a long duration of its use. The catalysts, essentially noble metal-based materials, are usually dispersed on conducting supports such as carbon powder. Conducting polymers are also important for the application of supporting catalysts in view of their high conductivity, ease of preparation and chemical stability. Poly(3,4-ethylenedioxythiophene) (PEDOT) is known to be superior to other conducting polymer such as polyaniline, in the above properties. In the studies described in this thesis, several catalysts in nanodimensions are electrochemically deposited on PEDOT, which is also prepared electrochemically on carbon paper current collectors. Electrooxidation of a few organic compounds is studied and the positive influence of PEDOT is demonstrated. The contents of the thesis are briefly given below. Chapter 1 provides introduction to electrocatalysis with a focus on factors affecting the electrocatalysis, different types of electrocatalysts and supports for catalyst and applications of PEDOT. This chapter also provides aim for various studies performed and presented in the thesis. Experimental details are reported in Chapter 2. Studies on electrooxidation of formic acid on nanoparticles of Pt electrodeposited on PEDOT/C electrode are reported in Chapter 3. The most promising electrocatalyst for formic acid oxidation is Pt. Because Pt based catalysts are expensive, achieving the highest possible catalytic activity from a minimum loading of Pt is a challenging task. Nanoparticles of Pt are electrochemically deposited on PEDOT, which is also electrochemically deposited on carbon paper substrate. A thin layer of PEDOT on carbon paper substrate facilitates the formation of uniform, well-dispersed nanoparticles of Pt, when compared with Pt deposition on a bare carbon paper substrate. TEM studies suggest that the nanoclusters of about 50 nm consist of nanoparticles of about 5 nm in diameter. Dispersion of fine Pt particles on PEDOT is expected to minimize or optimize the loading level of the catalyst. The voltammetry studies suggest that peak current for formic acid oxidation are several times greater on Pt-PEDOT/C electrode than Pt/C electrode. The catalytic activity and CO tolerance of Pt-PEDOT/C electrodes for electrooxidation of formic acid is significantly greater than that of Pt/C electrodes. Results of these studies are described in Chapter 3. Comparison studies for electrooxidation of C1, C2 and C3 alcohols on nanodendritic Pd-PEDOT/C electrode are presented in Chapter 4 and 5. Polyhydric alcohols such as glycol, glycerol have also been investigated as the fuels for DLFCs due to their high boiling points and less toxicity than methanol. The faradic efficiency of polyhydric alcohols is also higher than that of methanol. Thus, electrooxidation of polyhydric alcohols are more interesting than the monohydric alcohols. In this present study, three dimensional tree-like Pd nanodendrites are formed on PEDOT coated carbon paper electrode by a controllable one-step electrodeposition method without the use of any template or additive. A thin layer of PEDOT on the carbon paper substrate facilitates the formation of Pd nanodendrites ranging from 500 nm to 6 μm (Fig. 1). In the absence of PEDOT under-layer, Pd deposition is smooth and non-dendritic. Both Pd–PEDOT/C and Pd/C electrodes are studied for electrooxidation of C1, C2 and C3 aliphatic alcohols in an alkaline electrolyte. Owing to enhanced surface area and surface defects on dendritic Pd, the Pd–PEDOT/C electrode exhibits greater catalytic activity than the Pd/C electrode for oxidation of the three alcohols. Among them, glycerol exhibits a high rate of oxidation. Cyclic voltammetry studies suggest that peak current density increases with an increase in concentrations of alcohols and NaOH in the electrolyte. Cyclic voltammetry studies indicate that Pd–PEDOT/C electrode possesses a high electrochemical stability with greater catalytic activity than Pd/C electrode toward electrooxidation of alcohols. The amperometry and repeated cyclic voltammetry data suggest high stability of nanodendritic Pd in alkaline medium. Pd-PEDOT is expected to be an appropriate Pt-free electrocatalyst in alkaline fuel cells. Among all these alcohols, glycerol is expected to be an appropriate alcohol for application as a fuel in alkaline fuel cells at nanodendritic Pd on PEDOT surface. Fig. 1: SEM micrographs of (a) Pd-PEDOT/C and (b) Pd/C electrodes. Studies on electrooxidation of glycerol on nanoflowers of PdRu deposited on PEDOT/C electrode are reported in Chapter 6. PEDOT supported PdRu catalysts with various Pd:Ru atomic ratios are prepared by one step electrodeposition method. The catalysts are characterised by a several techniques. X-ray diffraction (XRD) studies suggest that the nanoflowers of PdRu catalyst exists on PEDOT surface in an alloy form. X-ray photoelectron spectroscopy (XPS) results indicate a slight modification in electronic structure of Pd by alloying with Ru. SEM micrograph shows the 3D nanoflowers morphology of PdRu alloy on PEDOT/C surface. Ru alloyed with Pd significantly improves the catalytic activity for glycerol oxidation in comparison to Pd-PEDOT/C electrode. However, the activity for glycerol oxidation on pure Ru-PEDOT/C is not observed. Amongst all catalysts, Pd5Ru nanoflowers on PEDOT surface exhibits highest electrocatalytic activity, real surface activity, exchange current density and stability (Fig. 2). Cyclic voltammetry and differential pulse voltammetry (DPV) are performed for analysis of glycerol. A series of voltammograms are recorded at Pd5Ru-PEDOT/C electrode in the concentration range 1-20 mM glycerol in 1 M NaOH supporting electrolyte. Cyclic voltammetry determination of glycerol provides the detection limit of 10 μM. Under optimised conditions, significantly higher sensitivity and lower detection limit were obtained by differential pulse voltammetry (DPV) method in comparison with cyclic voltammetry method. DPV data indicates that Pd5Ru on PEDOT is highly sensitive towards glycerol detection with sensitivity of 99.8 μA μM-1 cm-2 and low detection limit of 0.1μM. Thus, electrochemically deposited nanoflowers Pd5Ru on PEDOT/C are efficient catalysts for direct glycerol oxidation as well as for analysis purpose in alkaline media. The details of electrooxidation and analysis of glycerol are reported in Chapter 6. Current density / mA cm-2 5 Pf 4 (iii)Pd5Ru-PEDOT/C (ii)Pd7Ru-PEDOT/C 3 (iv)Pd4Ru-PEDOT/C (i)Pd-PEDOT/C (v)PdRu-PEDOT/C 2 Pb 1 0 (vi)Ru-PEDOT/C -1 -0.6 -0.4 -0.2 0.0 0.2 Potential / V vs SCE Fig. 2: Cyclic voltammograms of the Pd-PEDOT/C (i), Pd7Ru-PEDOT/C (ii), Pd5Ru-PEDOT/C (iii), Pd4Ru-PEDOT/C (iv), PdRu-PEDOT/C (v) and Ru-PEDOT/C (vi) electrodes in 0.1 M glycerol + 1.0 M NaOH solution at a sweep rate of 5 mV s-1. Current density is calculated on the basis of geometric area (1.4 cm2). In Chapter 7, the effect of Pd decorated Au@Ag core shell on PEDOT surface for glycerol oxidation is investigated. In this study, nanodendrites of Ag are deposited on PEDOT/C surface by potentiostatic method. The nanodendrite of Ag-PEDOT/C electrode is used as a template for the synthesis of Au@Ag core shell via galvanic displacement reaction. The galvanic displacement of Ag with Auleads to the formation of Au@Ag core shell on PEDOT surface with different morphology by controlling the reaction time. The formation of Au@Ag core shell is confirmed by XRD, SEM, EDAX, TEM, HRTEM and XPS studies. XRD study exhibits that the epitaxial growth of Au on Ag surface. EDAX and XPS studies indicate that the atomic ratio of Au to Ag in Au@Ag-PEDOT/C electrode is tuneable by controlling the reaction time. Further to improve the activity of Au@Ag core shell is decorated with Pd by potentiostatic method. Different quantity of Pd deposition is carried out at different charges to optimize the activity of catalyst and it is found that the optimum charge for deposition is 0.25 C. The Ag-PEDOT/C electrode is electrochemically inactive for glycerol oxidation reaction. However, the addition of Au to Ag facilitates the oxidation reaction of glycerol. Electrocatalytic activities of Pd decorated Au@Ag-PEDOT/C electrodes for glycerol oxidation in alkaline medium are characterized by cyclic voltammetry experiments. A high catalytic activity of Pd- (Au@Ag)-PEDOT/C(7.5 h) electrode with lower onset potential and higher current density is observed. In Chapter 8, non-enzymatic oxidation and analysis of glucose is studied on Au naoflowers surface. Glucose is abundant in nature, non-toxic, non-explosive, and non-volatile. The theoretical energy density of DGFCs is 4430 Wh kg-1, which is estimated on the basis of complete oxidation of glucose to CO2 releasing 24 e- per glucose molecule. Therefore, it is attractive and appears to fulfil most of the requirement of a fuel for low temperature fuel cells. Au is potentiostatically deposited on PEDOT as well as carbon paper electrode. A layer of PEDOT on carbon paper substrate facilitates the formation of Au nanoflowers with an enhanced electrochemical active surface area, when compared with sub-micron size Au particles deposited on bare carbon paper electrode. Cyclic voltammetry of glucose is studied by varying the concentration of glucose, NaOH and sweep rate. Cyclic voltammetric peak current density increases with increase in concentrations of glucose and NaOH in the electrolyte. 1H-NMR spectroscopy provides an evidence for oxidation of glucose to gluconic acid and formic acid. Repetitive cyclic voltammetry and amperometry studies suggest that the electrochemical stability of Au-PEDOT/C electrode is significantly higher than that of Au/C electrode. Au nanoflowers on PEDOT surface exhibit a high sensitivity value with low detection limit than that of Au/C electrode. Au-PEDOT/C electrode also exhibits a linear current response in glucose concentration ranging up to 10 μM with sensitivity of 515 μA cm-2 μM-1 (on the basis of geometric area) and a low detection limit of 0.03 μM with signal to noise ratio of 3. It is observed that uric acid and ascorbic acid do not show any significant interference effect on glucose analysis. Thus, electrochemically deposited nanostructured Au on PEDOT/C is an efficient catalyst for the direct glucose oxidation as well as for analysis purpose in alkaline media. Electroanalysis of As(III) is studied on Pd-PEDOT/C electrode in an acidic medium and the details are reported in Chapter 9. Analysis of As(III) is interesting because it is important to remove As(III) in ground water. The Pd nanodendrites are grown on a porous thin film of PEDOT by electrodeposition process. The oxidation of As(0) at low concentration is characterized by an anodic peak at 0.20 V vs. standard calomel electrode (SCE). Cyclic voltammetry studies suggest that Pd-PEDOT/C electrodes exhibit greater electrocatalytic activity towards As(III)/As(0) redox reaction than the Pd/C electrodes. Differential pulse anodic striping voltammetry (DPASV) is performed for analysis of As(III) ion at pH 1.0 (Fig. 3(a)). The PEDOT modified Pd electrode is highly sensitive toward As(III) detection with sensitivity of 1482 μA cm-2 μM-1 (Fig. 3(b)). A wide detection range up to 10 μM and low detection limit of 7 nM (0.52 ppb) are obtained with a pre-deposition time of 120 s under optimum conditions. Interference effect of Cu(II) ions are investigated and it is observed that Cu(II) ions do not interfere. It is found that PEDOT does not have any influence on analysis of As(III). 700 (a) 600 -2 cmA 500 / μ j 400 300 0.0 increasing concentration of As(III) 340 (b) 320 300 -2 280 A cm 260 μ/ 240 j 220 200 Sensitivity : 1482 μA cm-2 μM-1 180 R2= 0.9998 160 0.1 0.2 0.3 0.4 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 Potential / V vs SCE Concentration / μ M Fig. 3: (a) DPASV curves of Pd-PEDOT/C electrode in different concentration of As (III) + 1 M HCl and (b) DPASV calibration plots of Pd-PEDOT/C electrode peak current density versus arsenic concentration (pre-deposition at -0.30 V for 120 s). Current density (j) is calculated on the basis of geometric area (1.4 cm2). Details of the above studies are presented in the thesis. The work presented in the thesis is carried out by the candidate as a part of PhD training programme and most of the results have been published in the literature. A list of publications of the candidate is enclosed. It is hoped that the studies reported here will constitute contribution.

Thesis (Ph. D.)--Florida State University, 2007.
Advisor: Peng Xiong, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed 03/20/2008). Document formatted into pages; contains xix, 143 pages. Includes bibliographical references.

Hybrid quantum dot /organic semiconductor systems are of great interest in optoelectronic and photovoltaic applications, because they combine the robust and tunable optical properties of inorganic semiconductors with the processability of organic thin films. In particular, cadmium selenide (CdSe) quantum dots coordinated with oligo-(phenylene vinylene) ligands have displayed a number of hybrid optical properties that make them particularly well-suited to these applications. When probed on an individual particle level, these so-called CdSe-OPV nanostructures display a number of surprising photophysical characteristics, including strong quenching of fluorescence from coordinating ligands, enhanced emission from the CdSe quantum dot core, suppression of fluorescence intermittency, and photon antibunching, all of which make them attractive in the applications described above. By correlating fluorescence properties with atomic force microscopy, the effects of ligands on quantum dot luminescence are elucidated. In addition, recent studies on individual CdSe-OPV nanostructures have revealed a strong electronic coupling between the coordinating ligands and the nanocrystal core. These studies have shown that excitations in the organic ligands can strongly affect the electronic properties of the quantum dot, leading to linearly polarized optical transitions (both in absorption and emission) and polarization-modulated shifts in band edge emission frequency. These polarization effects suggest exciting new uses for these nanostructures in applications that demand the robust optical properties of quantum dots combined with polarization-switchable control of photon emission.

Single molecule studies on CdSe quantum dots functionalized with oligo-phenylene vinylene ligands (CdSe-OPV) provide evidence of strong electronic communication that facilitate charge and energy transport between the OPV ligands and the CdSe quantum dot core. This electronic interaction greatly modify, the photoluminescence properties of both bulk and single CdSe-OPV nanostructure thin film samples. Size-correlated wide-field fluorescence imaging show that blinking suppression in single CdSe-OPV is linked to the degree of OPV coverage (inferred from AFM height scans) on the quantum dot surface. The effect of the complex electronic environment presented by photoexcited OPV ligands on the excited state property of CdSe-OPV is measured with single photon counting and photon-pair correlation spectroscopy techniques. Time-tagged-time-resolved (TTTR) single photon counting measurements from individual CdSe-OPV nanostructures, show excited state lifetimes an order of magnitude shorter relative to conventional ZnS/CdSe quantum dots. Second-order intensity correlation measurements g(2)(τ) from individual CdSe-OPV nanostructures point to a weak multi-excitonic character with a strong wavelength dependent modulation depth. By tuning in and out of the absorption of the OPV ligands we observe changes in modulation depth from g(2) (0) ≈ 0.2 to 0.05 under 405 and 514 nm excitation respectively. Defocused images and polarization anisotropy measurements also reveal a well-defined linear dipole emission pattern in single CdSe-OPV nanostructures. These results provide new insights into to the mechanism behind the electronic interactions in composite quantum dot/conjugated organic composite systems at the single molecule level. The observed intensity flickering , blinking suppression and associated lifetime/count rate and antibunching behaviour is well explained by a Stark interaction model. Charge transfer from photo-excitation of the OPV ligands to the surface of the CdSe quantum dot core, mixes electron/holes states and lifts the degeneracy in the band edge bright exciton state, which induces a well define linear dipole behaviour in single CdSe-OPV nanostructures. The shift in the electron energies also affects Auger assisted hole trapping rates, suppress access to dark states and reduce the excited state lifetime.

碩士
中原大學
物理研究所
103
The development of renewable energy is important because current energy source, such as fossil fuel, coal and nature gas will be ultimately exhausted. Organic solar cells have many advantages, such as low cost and large-area fabrication on flexible substrate. However, the power conversion efficiency of organic solar cells is inferior to the one of inorganic solar cells. The aim of this work is to enhance the efficiency through introducing nanostructure and doping in organic solar cells. The first part of this work is to blend small molecule TES-ADT in photoactive layer, trying to increase carrier mobility, crystallinity and efficiency. According to our results, it demonstrated that, through optimizing the doping concentration of TES-ADT (5%), the carrier mobility, crystallinity and device efficiency can be increased. The efficiency can be increased from 1.38% to 2.71%. The short-circuit current density can be increased from 6.46 mA/cm2 to 9.23 mA/cm2. The second part of this work is to realize nanostructured cathode for light scattering, which can increase optical path and light absorption. Through depositing aluminum on non-close-packed polystyrene sphere array, the nanostructured cathode can be easily fabricated. According to the dark-field optical microscope image, the nanostructured cathode indeed enhanced the light scattering. The device with nanostructured cathode shows higher absorption and evviciency. The efficiency can be increased from 2.79 % to 3.35 %. The short-circuit current density can be increased from 9.47 mA/cm2 to 14.18 mA/cm2.

博士
國立臺灣大學
化學工程學研究所
104
Organic-field-effect-transistor (OFET) -type memory devices have been extensively studied due to their flexibility, scalability, and solution processability. Functional polymer containing semiconducting elements is considered as one of the most promising charge storage materials for organic field-effect transistors and organic-based memory devices, since it features a systematic route towards materials with novel architectures, functions, and physical properties. However, there is limited study on the correlations of the nanostructure and the electronic characteristic. In this thesis, we report the OFET memory devices using the dielectric layer of cross-linked core-shell block copolymers containing conjugating segments in the cores, and reveal the effect of both block composition and nanostructure on the memory characteristics. We further explored the random copolymers consisting of both pendant electron-donating and -withdrawing groups as charge storage layer in the OFET memory devices. In addition, for comparing with the synthetic polymer electrets, the solution-associated supramolecules are also applied in the OFET memory devices as charge storage dielectrics. The important discovery of this thesis was summarized in the follows. 1. Non-Volatile Field-Effect Transistor Memory Devices using Charge Storage Cross-Linked Core-Shell Nanoparticles as Polymer Electrets (Chapter 2): Solution processable cross-linked core-shell nanoparticles containing conjugated elements are firstly explored as charge storage materials for transistor-type (OFET) memories. These uniform nanoparticles containing cross-linked electron-donating or donor-acceptor cores presented efficient flash-type memory characteristics. The devices using donor-acceptor nanoparticles presented both electron- and hole-trapping abilities, along with the memory window of 38 V, the retention ability of over 10^4 s, and endurance of over 100 cycles. 2. Multilevel Non-Volatile Organic Transistor Memory Devices using Pendent Donor-Acceptor Random Copolymer Electrets (Chapter 3): Non-volatile transistor memories were fabricated using n-type semiconductor BPE-PTCDI and dielectric layer of non-conjugated random copolymers with pendant electron-donating 9-(4-vinylphenyl)carbazole (VPK) and electron-withdrawing 2-phenyl-5-(4-vinylphenyl)-1,3,4-oxadiazole (OXD) moieties. The pendent structure provided restricting regions with well-defined donor-acceptor interfaces, which is not happened in the case of PVPK/POXD polymer blend. The multilevel data storage and endurance characteristics obtained by applying different voltage pulses suggested that the devices using random copolymer P(VPKxOXDy) as electrets possessed ambipolar and controllable non-volatile flash-type memory behaviors even when the working voltage was as low as 10 V. 3. High-Performance Non-Volatile Transistor Memory Devices using Charge-Transfer Supramolecular Electrets (Chapter 4): Non-volatile OFET memory devices using charge-transfer (CT) supramolecules of poly(4-vinylpyridine) (P4VP) with two different chromophores, 3-(dicyanomethylidene)indan-1-one (1CN-IN) or 1,3-bis(dicyanomethylidene)indan (2CN-IN) were demonstrated. The intermolecular CT interaction effectively introduced the chromophores as charge trapping sites into the P4VP matrix, leading to a controllable flash-type memory behavior. The 2CN-IN with one more electron-withdrawing dicyanomethylene group, compared to 1CN-IN, provided a better electron-trapping ability and thus obtained a larger memory window. The device based on P4VP(2CN-IN)0.30 electret exhibited the largest memory window of 79 V with the excellent retention ability of up to 10^7 s and endurance of over 100 cycles. Our study demonstrated the significance of interfacial charge-transfer mechanism and molecular nanostructure on the charge transporting and memory characteristics for novel organic electronic devices.

Thesis (Ph. D.)--University of Notre Dame, 2004.
Thesis directed by Albert E. Miller for the Department of Chemical and Biomolecular Engineering. "June 2004." Includes bibliographical references (leaves 237-256).

碩士
國立交通大學
材料科學與工程學系所
102
Organic field-effect transistor (OFET) memory devices incorporating the copolymer polystyrene-block-poly(4-vinylpyridine) (PS56k-b-P4VP8k) layer, which features a thickness-dependent micellar nanostructure (P4VP-core, PS-shell), as a charge trapping layer can exhibit tunable memory windows for p-channel applications. For instance, the memory window increased substantially from 7.8 V for the device incorporating a 60 nm thick PS56k-b-P4VP8k layer to 21 V for the device incorporating a 27 nm thick layer, an increase of more than 2.5 times. Using simultaneous synchrotron grazing-incidence small-angle X-ray scattering and wide-angle X-ray scattering to probe the nanostructured micellar PS56k-b-P4VP8k layer and the pentacene layer positioned directly on the top of the copolymer layers, respectively, we were able to elucidate the structural characteristics of the bilayer and to correlate their effects with the memory performances of devices with similar architectures. For the PS56k-b-P4VP8k layers, we found that the inter-micelle distance and their lateral arrangements depended on the layer thickness: the thickness of the PS shells in the lateral direction decreased upon increasing the layer thickness, as did the memory window for the OFET device that incorporated the PS56k-b-P4VP8k layers, showing a strong dependence of the threshold voltage shifts (i.e., memory window) on the distance between the micelles. Additionally, for the molecular packing of the pentacene layer positioned on the copolymer layer, we found that the PS56k-b-P4VP8k layers affected not only the orientation of the pentacene molecules but also their grain sizes, thereby affecting the hole mobility of the memory devices. These results suggest that tuning the micellar nanostructure of the block copolymer thin film that was used as a trapping layer can be a simple and effective way for optimizing the memory window and affecting the hole mobility of OFET memory devices.

This dissertation presents the investigation of magnetic exchange and anisotropy in novel metal-organic complexes containing minimum number of magnetic ions. Such complexes can serve as a model system to understand the exciting magnetic phenomena in such class of materials and also can put forward as candidates for the so called molecular nanomagnets. A direct assessment of the effective magnetic moment and the effective interaction between the metal ions in the complex can be done using magnetization measurements. Here the magnetization studies are performed as a function of temperature and field using a SQUID magnetometer. Yet another powerful tool to characterize and determine the spin levels, the ESR spectroscopic methods, has also been exploited. The study of the dynamical properties of this class of materials was relevant to understand the relaxation mechanism in the low temperatures. For this a new ac susceptometer has been built in house which was another main objective of this dissertation work. The design, fabrication, calibration and automation done on this device is presented in this thesis. The device has been tested using the known molecular magnet Mn12 acetate, and the antiferromagnet Dy2PdSi3. The present work is mainly focused on the magnetic properties of Mn, Ni and Fe based organometallic complexes. The studied Mn dimer with different acceptor and donor ligands exhibit the fine tuning of the electron density at the core of molecular complex by variation in ligands. This in turn shows that the change in peripheral ligands can control the magnetism of the molecule. The influence of the change in Ni-S-Ni bond angle in the magnetic exchange interaction is studied in a Ni(2) dimer and a Ni(2) trimer complex. The Ni dimer complex shows a ferromagnetic interaction (J = -42K) whereas trimer shows an antiferromagnetic interaction (J = 140K). Another Ni based complex bridged via phosphorous has been studied which shows the existence of glassy nature at low temperature. Also a polymeric chain compound based on Fe is studied and presented. All these phosphorous or sulphur bridged complexes are novel materials and these are the first data on these complexes.