Academic literature on the topic 'Nanohorns de carbono'

The first in silico modeling of the Pd–H-single-walled carbon nanohorn nanocomposites shows that apex angle of horn-shaped tips of single-walled carbon nanohorns controls the morphology and reactivity of confined Pd clusters.

By far the most important members of carbon-based materials family, are graphene, Carbon Nanotube (CNT) and Carbon Nanohorn (CNH). Thanks to their outstanding features and effective applications, have been broadly researched in recent times. Numerous ways have been proposed to synthesize graphene, CNT and CNH. This paper presents an overview of approaches to graphene, CNT and CNH synthesis, properties and applications. Most of the ways to create graphene is related to Hummer's method. Thanks to the exclusive electrical and thermal properties of graphene, it has been applied to build batteries, gas and vapor sensors, and elimination of numerous pollutants from water. Also, this review involves the conventional definition of the carbon nanotubes growth mechanism. Undoubtedly, an expert interpretation of nanotube growth at the atomic scale is one of the major challenges to improve nanotubes bulk synthesis procedure. In fact, a controlled growth may lead to get the ideal form of nanotube. Moreover, carbon nanohorn is a new member of single-graphene tubules family with a diameter of 3-6 nm and a length 35-45 nm. According to the latest reports, a new fluid including carbon nanohorns and ethylene glycol can be used for solar energy applications. Carbon nanohorns have an important role in increasing sunlight absorption as for the pure base fluid. Nanohorn spectral characteristics are far more interesting than those of amorphous carbon for the exclusive application. They can be used in important industries such as gas sensors, drug delivery, detecting some food borne contaminants.

Lithium–sulfur batteries are considered one of the most appealing technologies for next-generation energy−storage devices. However, the main issues impeding market breakthrough are the insulating property of sulfur and the lithium−polysulfide shuttle effect, which cause premature cell failure. To face this challenge, we employed an easy and sustainable evaporation method enabling the encapsulation of elemental sulfur within carbon nanohorns as hosting material. This synthesis process resulted in a morphology capable of ameliorating the shuttle effect and improving the electrode conductivity. The electrochemical characterization of the sulfur–carbon nanohorns active material revealed a remarkable cycle life of 800 cycles with a stable capacity of 520 mA h/g for the first 400 cycles at C/4, while reaching a value around 300 mAh/g at the 750th cycle. These results suggest sulfur–carbon nanohorn active material as a potential candidate for next−generation battery technology.

In the past few decades, nanostructured carbons (NCs) have been investigated for their interesting properties, which are attractive for a wide range of applications in electronic devices, energy systems, sensors, and support materials. One approach to improving the properties of NCs is to dope them with various heteroatoms. This work describes the synthesis and study of sulfur-added carbon nanohorns (S-CNH). Synthesis of S-CNH was carried out by modified chemical vapor deposition (m-CVD) using toluene and thiophene as carbon and sulfur sources, respectively. Some parameters such as the temperature of synthesis and carrier gas flow rates were modified to determine their effect on the properties of S-CNH. High-resolution scanning and transmission electron microscopy analysis showed the presence of hollow horn-type carbon nanostructures with lengths between 1 to 3 µm and, diameters that are in the range of 50 to 200 nm. Two types of carbon layers were observed, with rough outer layers and smooth inner layers. The surface textural properties are attributed to the defects induced by the sulfur intercalated into the lattice or bonded with the carbon. The XRD patterns and X-ray microanalysis studies show that iron serves as the seed for carbon nanohorn growth and iron sulfide is formed during synthesis.

Carbon nanotube is a special case of carbon nanohorns or carbon nanocones with zero apex angle. Research into carbon nanohorns started almost at the same time as the discovery of nanotubes in 1991. Most researchers focused on the investigation of nanotubes, and the exploration of nanohorns attracted little attention. To model the carbon nanohorns, we make use of a more reliable second-generation reactive empirical bond-order potential by Brenner and coworkers. We investigate the elastic moduli and conclude that these nanohorns are equally strong and require in-depth investigation. The values of Young's and Shear moduli decrease with apex angle.

Nowadays, the use of lasers has become commonplace in everyday life, and laser protection has become an important field of scientific investigation, as well as a security issue. In this context, optical limiters are receiving increasing attention. This work focuses on the identification of the significant parameters affecting optical limiting properties of aqueous suspensions of pristine single-wall carbon nanohorns. The study is carried out on the spectral range, spanning from ultraviolet to near-infrared (355, 532 and 1064 nm). Optical nonlinear properties are systematically investigated as a function of nanohorn morphology, concentration, dimensions of aggregates, sample preparation procedure, nanostructure oxidation and the presence and concentration of surfactants to identify the role of each parameter in the nonlinear optical behavior of colloids. The size and morphology of individual nanoparticles were identified to primarily determine optical limiting. A cluster size effect was also demonstrated, showing more effective optical limiting in larger aggregates. Most importantly, we describe an original approach to identify the dominant nonlinear mechanism. This method requires simple transmittance measurements and a fitting procedure. In our suspensions, nonlinearity was identified to be of electronic origin at a 532 nm wavelength, while at 355 nm, it was found in the generation of bubbles.

In this study, dahlia-type carbon nanohorns (CNH) have been deposited onto a stainless steel substrate by using electrophoretic deposition. Secondly, the lubrication properties of the carbon nanohorn coating have been researched by tribometry and compared to an uncoated reference. Wear track analysis has been conducted to identify the underlying tribo-mechanisms. Additionally, Raman spectroscopy was employed to study the structural changes of the CNH during dispersion and tribological testing. Furthermore, energy dispersive X-ray spectroscopy (EDX) was used in order to investigate the chemical composition of the wear tracks’ surface. This work has shown that CNH coatings have the ability to maintain effective solid lubrication on a polished stainless steel surface. A temporary friction reduction of 83% was achieved compared to the uncoated reference. Moreover, the lubricity was active for significant periods of time due to the formation of a Mg(OH)2 layer which provides a certain degree of substrate adhesion as it holds the CNH in the wear track. Once this holding layer wanes, the CNH are gradually removed from wear track resulting in an increase of the coefficient of friction. The complete removal of CNH from the wear track as well as considerable oxide formation was confirmed by EDX. Moreover, the amount of defects in the CNHs’ structure increases by being exposed to tribological strain. Adhesion has been identified as the dominant wear mechanism.

2013/2014
La nanotecnologia è chiamata a rivoluzionare molti settori della nostra vita. Tra tutti i campi in cui è convolta, la ricerca delle energie rinnovabili, la possibilità di ottenere acqua pulita in tutte le parti del mondo, il miglioramento della salute e l’aumento dell’aspettativa di vita e lo sviluppo di sistemi informatici, sono gli obiettivi che si distinguono. Le nanostrutture di carbonio sono materiali promettenti che possono aiutare a raggiungere questi obiettivi: includono fullereni, grafene, nanotubi e nanohorns di carbonio. Tutti hanno proprietà interessanti e offrono nuovi vantaggi per le applicazioni in chimica dei materiali e nella medicina. Il nostro gruppo di ricerca ha sviluppato interessanti metodi per modificare queste nanostrutture per poterli applicare nei campi sopra menzionate. In questo contesto, lo scopo generale di questa tesi è il disegno di sistemi multifunzionali basati su nanostrutture di carbonio destinati ai sensori e alle applicazioni biologiche. Nel capitolo 1, viene fatta una breve panoramica dei nanotubi e i nanohorns di carbonio, spiegando la loro struttura, le loro proprietà e le loro applicazioni. Inoltre, vengono descritte le diverse strategie per la loro funzionalizzazione. Il riconoscimento molecolare gioca un ruolo importante in molti sistemi biologici. In flavoproteine, l'interazione specifica tra il cofattore flavina e l’apoenzima determina la reattività della proteina. Di conseguenza, la modulazione dell'ambiente delle flavine può essere utilizzata come strumento per determinare il loro comportamento e anche per comprendere i processi molecolari negli enzimi. Con questi obiettivi in mente, nel capitolo 2 è descritta la sintesi di differenti derivati basati sul sistema nanotubi di carbonio-triazina per l’uso come ricevitori di riboflavina. In primo luogo, la sintesi e la caratterizzazione di diverse 1,3,5-triazine sono riportate. In una seconda fase, viene descritta la funzionalizzazione di nanotubi di carbonio a parete singola e a parete multipla con le differenti triazine e anche con catene di p-tolil, impiegando le radiazioni microonde. Dopo, si riporta la caratterizzazione completa di questi derivati con varie tecniche. L’auto-assemblaggio degli ibridi è stato analizzato con microscopia elettronica a trasmissione, osservando come i funzionalizzati con 1,3,5-triazine formano buone dispersioni in acqua, mentre loro si auto-assemblano in solventi non polari a causa del riconoscimento di legami d’idrogeno complementari. Tuttavia, derivati funzionalizzati con p-tolil formano migliori dispersioni in solventi organici ed invece si auto-assemblano in acqua. Viene poi studiata la capacità dei nanotubi di carbonio funzionalizzati a parete multipla di riconoscere la riboflavina con la spettroscopia di fluorescenza e ultravioletta visibile, analizzando la grandezza delle interazioni non-covalenti. Si vede come la funzionalizzazione covalente dei nanotubi di carbonio diminuisce la loro capacità di formare interazioni  mentre le interazioni di legame d’idrogeno giocano un ruolo fondamentale nel processo di riconoscimento tra i membri del sistema. Inoltre, si è demostrata l’influenza dei tipi di triazine nel comportamento della riboflavina. In questo modo, è dimostrata la modulazione del riconoscimento molecolare della riboflavina attraverso i diversi nanotubi. Così, recettori artificiali in processi di catalisi possono essere specificamente disegnati per ottenere il controllo delle interazioni tra i nanotubi di carbonio funzionalizzati e la riboflavina, modificando il suo comportamento. Inoltre, le dimensioni e le eccellenti proprietà di nanotubi permettono di utilizzarli come strumento nella progettazione di sensori per la rivelazione di singole molecole. Nel capitolo 3 si riporta la modifica di nanohorn di carbonio per l'impiego come farmaci selettivi nella terapia del cancro è rapportata. Prima, si mostra la sintesi e la caratterizzazione di diversi ibridi di nanohorn: Antibody-CNH, Drug-CNH, Antibody-Drug-CNH e Double Functionalized-CNH. In particolare vengono usati cisplatino, come profarmaco, ed un anticorpo specifico per le cellule che mostrano l’antigene PSMA (Prostate-specific membrane antigen). Di seguito, vengono presentati diversi esperimenti biologici sviluppati in collaborazione con il professor Marco Colombatti dell’Università degli Studi di Verona (Italia). L’ibrido Antibody-Drug-CNH possiede una migliore capacità di uccidere selettivamente le cellule che presentano l'antigene PSMA, rispetto ad altri derivati di nanohorns. Il nuovo sistema progettato offre un grande potenziale dato dalla possibilità di modificare il tipo e il grado di funzionalizzazione. Questo permette di variare la quantità di farmaco o di anticorpo nelle nanostrutture con lo scopo di migliorare l’efficienza dei nuovi derivati. Inoltre, questo metodo può incorporare altri farmaci o anticorpi al sistema, aprendo la porta al trattamento di altre malattie. Il capitolo 4 descrive l'applicazione di diverse nanostrutture di carbonio nella terapia genica. Prima, si mostra la funzionalizzazione di nanohorns di carbonio con gruppi amminici, impiegando diversi metodi che utilizzano le radiazioni a microonde (cicloaddizione 1,3-dipolare e addizione radicalica). In seguito, viene presentato il lavoro svolto in "the Nanomedicine Lab" (Università di Manchester), sotto la supervisione del Prof. Kostas Kostarelos. L'efficacia dei nanohorns di carbonio funzionalizzati per formare complessi con siRNA è comparata con quella dei nanotubi di carbonio forniti dal gruppo del professor Kostarelos. Si è visto come i nanohorn di carbonio formino complessi con siRNA a differenza dei nanotubi. I complessi siRNA/nanohorn si caratterizzano utilizzando varie tecniche e viene analizzata la loro capacità di rilasciare il siRNA. Sebbene nanohorn di carbonio funzionalizzati con l’addizione radicalica mostrano una forte interazione con il materiale genetico, i derivati funzionalizzati con la cicloaddizione 1,3-dipolare lo rilasciano più facilmente. I risultati suggeriscono che, per conseguire il miglior carrier, la complessazione totale del siRNA con le nanostrutture dovrebbe essere evitato. Tuttavia, gli ibridi devono essere analizzati in vitro per garantire la migliore scelta. Questo studio contribuisce alla comprensione dell’uso di nanohorn di carbonio come vettori per terapia genica; ma, un maggior numero di derivati deve essere analizzato per un confronto completo con i nanotubi di carbonio.
La nanotecnología se presenta como una nueva ciencia que podrá revolucionar multiples aspectos de nuestras vidas. Entre los numerosos campos en los que la nanotecnología está centrada, la búsqueda de energías renovables, la posibilidad de obtener agua limpia en cualquier parte del mundo, la mejora de la salud y la longevidad de las personas así como el avance de los sistemas informáticos, son los objetivos que más destacan. Las nanoestructuras de carbon son nanomateriales prometedores que pueden ayudar a lograr esas metas. Estos materiales incluyen fullerenos, grafeno, nanohorns y nanotubos de carbono, entre otros. Todos ellos presentan propiedades interesantes y ofrecen nuevas ventajas para aplicaciones en química de materiales y medicina. Nuestro grupo de investigación ha desarrollado metodologías interesantes para la modificación de esas nanoestructuras con el objeto de que puedan ser útiles en las aplicaciones citadas anteriormente. En ese contexto, el objetivo general de esta tesis es el diseño de sistemas multifuncionales basados en nanoestructuras de carbono para ser usados en sensores y en aplicaciones biológicas. En el capítulo 1 se detallan la estructura y las propiedades de los nanohorns y los nanotubos de carbono junto a sus aplicaciones. Además, se muestra un resumen de las diferentes metodologías usadas para su funcionalización. El reconocimiento molecular juega un papel importante en numerosos sistemas biológicos. En flavoproteinas, la interacción específica entre el cofactor flavina y la apoenzima determina la reactividad total de la proteina. De este modo, la modulación del entorno de la flavina puede usarse como herramienta para determinar su comportamiento y, además, para entender los procesos moleculares en las enzimas. Con esos objetivos en mente, en el capítulo 2 se describe la síntesis de diferentes derivados basados en el sistema nanotubo de carbono-triazina para usarlos como receptores múltiples de riboflavina. En primer lugar, se sintentizan y caracterizan distintas 1,3,5-triazinas. En un segundo paso, se funcionalizan nanotubos de carbono tanto de pared simple como de pared multiple con las diferentes triazinas así como con cadenas de p-tolilo usando radiación microondas, y esos derivados se caracterizan completamente mediante diversas técnicas. El autoensamblaje de los híbridos se analiza mediante microscopía de transmisión electrónica observando como los derivados de 1,3,5-triazinas forman buenas dispersiones en agua y se autoensamblan en disolventes no polares debido al reconocimiento mediante enlaces de hidrógeno complementarios. Sin embargo, los derivados de p-tolilo forman mejores dispersiones en disolventes orgánicos y se agregan en agua. Finalmente, la habilidad de los nanotubos de carbono de pared múltiple funcionalizados para reconocer la riboflavina se estudia mediante fluorescencia y espectrocopía ultravioleta visible, analizando el alcance de las interacciones no covalentes. La funcionalización covalente de nanotubos de carbono disminuye su habilidad para formar interacciones  mientras que las interacciones mediante enlaces de hidrógeno juegan un papel fundamental en el proceso de reconocimiento entre los componentes del sistema. También se estudia la infuencia de las diferentes triazinas en el comportamiento de los complejos. De esta manera, se demuestra la modulación del reconocimiento de la riboflavina por medio de los diversos híbridos de nanotubos de carbono. Así, los receptores artificiales en procesos de catálisis pueden ser específicamente diseñados para lograr control de la interacción entre los nanotubos de carbono funcionalizados y la riboflavina, modificando así su comportamiento. En el capítulo 3 se describe la modificación de nanohorns de carbon para ser usados como fármacos selectivos en la terapia contra el cancer. En primer lugar se muestra la síntesis y caracterización de diferentes híbridos de nanohorns: Antibody-CNH, Drug-CNH, Antibody-Drug-CNH and Double Functionalized-CNH. En particular se usan cisplatino en forma de prodroga y un anticuerpo específico (D2B) para células de próstata que muestran el antígeno PSMA. Finalmente se presentan diferentes experimentos biológicos desarrollados en colaboración con el profesor Marco Colombatti, de la Universidad de Verona (Italia). Se demuestra la mejor habilidad del híbrido Antibody-Drug-CNH para matar selectivamente células que muestran el antígeno PSMA en comparación con los otros derivados de nanohorns. El nuevo sistema diseñado ofrece gran potencial debido la la posibilidad de modificar tanto el tipo como el grado de funcionalización. Esto permite variar la cantidad de fármaco o anticuerpo en la nanoestructura con el objetivo de conseguir una mejor eficacia del derivado. Además, con este método se pueden incorporar otros fármacos o anticuerpos al sistema, lo que abre la puerta al tratamiento de otras enfermedades. El capítulo 4 describe la aplicación de distintas nanoestructuras de carbono en terapia génica. Primero se muestra la funcionalización de nanohorns de carbono con grupos amino mediante diferentes metodologías usando radiación microondas (cicloadición 1,3-dipolar y adición radicálica). Después, se presenta el trabajo desarrollado en “the Nanomedicine Lab” (Universidad de Manchester) bajo la supervision del profesor Kostas Kostarelos. Se compara la eficacia de los nanohorns de carbono funcionalizados para formar complejos con siRNA con la de una serie de nanotubos de carbono aportados por el grupo del profesor Kostarelos. En nuestros experimentos, los nanohorns de carbon forman complejos mejor que los nanotubos. Los complejos siRNA/nanohorns se caracterizan mediante diversas técnicas y se analiza su capacidad de liberar el siRNA. Aunque los nanohorns de carbono funcionalizados mediante adición radicálica muestran una interacción más fuerte con el material genético, los derivados funcionalizados mediante cicloadición 1,3-dipolar lo liberan de manera más fácil. Los resultados sugieren que la complejación total entre el siRNA y la nanoestructura debe ser evitada para lograr más fácilmente el posterior desplazamiento de este dentro de la célula. Sin embargo, para garantizar la elección del híbrido más eficaz, los complejos deben ser analizados in vitro. Por tanto, este estudio contribuye al entendimiento de los nanohorns de carbono como vectores en terapia génica. No obstante, un mayor número de derivados deben ser analizados para lograr una comparación completa con los nanotubos de carbono.
Nanotechnology is claimed to revolutionize every aspect of our life. Among the large number of fields in which nanotechnology is involved; finding renewable clean energy, obtaining clean water for all, improving health and longevity and enhancing computing power are the most noteworthy. Carbon nanostructures are promising nanomaterials that can help to achieve these objectives. Fullerenes, graphene, nanohorns and nanotubes are including within these materials. All of them exhibit interesting properties and offer new opportunities for applications in material chemistry and medicine. Our research group has developed interesting methodologies for modifying these nanostructures in order to be used in the aforementioned applications. In this context, the objective of this thesis is the design of multifunctional systems based on carbon nanomaterials to be applied in sensors and in biological applications. Chapter 1 explains the structure, properties and applications of carbon nanohorns and carbon nanotubes, together with their applications. In addition, it provides an overview of the different methodologies to functionalize them. Molecular recognition plays an important role in numerous biological systems. In flavoproteins, the specific interaction between the flavin cofactor and the apoenzyme determines the reactivity of the entire protein. Therefore, the modulation of the environment of flavins can be used as a tool to set their behaviour and to understand the molecular processes in enzymes. With these aims, chapter 2 describes the synthesis of different carbon nanotubes-triazine derivatives to be used as multi-receptors of riboflavin. Firstly, different triazines are synthesized and characterized. In a second step, both single-walled and multi-walled carbon nanotubes are functionalized with different 1,3,5-triazine and p-tolyl chains using radical addition under microwave irradiation and these derivatives are characterized by different techniques. The self-assembly of these hybrids is analysed by transmission electron microscopy, observing how the 1,3,5-triazines derivatives form good dispersions in water and self-assemble in non-polar solvents due to the DAD-ADA hydrogen bonding recognition, while the p-tolyl derivatives show better dispersability in organic solvents and aggregate in polar solvents. Finally, the ability of the functionalized multi-walled carbon nanotubes to recognize riboflavin is studied by fluorescence and UV spectroscopy, analysing the scope of the different non-covalent interactions. It is shown that the functionalization of nanotubes by covalent approach decreases the ability of them to form  stacking and also that the hydrogen bond interactions play an important role in the recognition processes between the components. The influence of the different triazines in the complexes is also shown. Thus, the modulation of the molecular recognition of riboflavin by the diverse nanotubes hybrids is demonstrated. Therefore, our study clarifies the understanding of non-covalent interactions in biological systems. In this way, artificial receptors in catalystic processes could be designed through a specific control of the interaction between functionalized carbon nanotubes and riboflavin. Additionally, the size and the excellent properties of carbon nanotubes will permit to use them as the building blocks in the design of sensors for single-molecule detection. In chapter 3, the modification of carbon nanohorns to be applied as new selective drugs in cancer therapy is shown. Firstly, the synthesis and characterization of different conjugates by the functionalization of carbon nanohorns with orthogonal chains is reported: Antibody-CNH, Drug-CNH, Antibody-Drug-CNH and Double Functionalized-CNH. In particular, cisplatin in a prodrug form and a specific D2B antibody for PSMA+ prostate cancer cells are attached. In collaboration with the group of Professor Marco Colombatti, different biological experiments are reported. The better ability of Antibody-Drug-CNH to selectively kill PSMA+ cancer cells in comparison with the other synthesized CNHs hybrids is demonstrated. This new system offers great potentiality due to the possibility of modifying the type and degree of functionalization. This allows the variation of the quantity of drug or antibody attached to the nanostructure in order to play with the killing efficacy. Similarly, the method is useful to attach different drugs or antibodies opening the way to the treatment of other diseases. Chapter 4 describes the application of different carbon nanostructures in gene delivery. Firstly, the functionalization of carbon nanohorns with amino moieties by different methodologies (1,3-dipolar cycloaddition and radical addition) under microwave irradiation and their characterization is shown. Then, the work developed at the Nanomedicine Lab (University of Manchester) under the supervision of Professor Kostas Kostarelos is reported. The efficacy of the functionalized carbon nanohorns to form complexes with siRNA is compared with the one of functionalized carbon nanotubes provides by Prof. Kostarelos’s group. In our experiments, carbon nanohorns form complexes better than nanotubes. The nanohors complexes are characterized by different techniques and their capability to release siRNA is analysed. Although the carbon nanohorns functionalized by radical addition showed the strongest complexation of siRNA, the derivatives functionalized by 1,3-dipolar cycloaddition showed its easiest release. The results suggest that, in order to obtain the best candidate, a complete complexation of siRNA with the carrier should be avoided. However, the analysis of the cellular uptake should be evaluated in the future to assess the greatest candidate. These outcomes contribute to the understanding of the role of carbon nanohorns as gene delivery vectors. Nevertheless, additional derivatives should be tested for a fully comparison with carbon nanotubes.
XXVII Ciclo
1986

2006/2007
“Funzionalizzazione ed applicazione di carbon nanohorns e di carbon onions” Dalla scoperta della microscopia a scansione a sonda (SPM) nel 1980 a quella del fullerene, molti sono stati i premi Nobel nel campo delle Nanotecnologie. Diverse compagnie, attualmente, hanno investito fondi in questo settore. Ma cosa sono le Nanotecnologie? La parola e’utilizzata per descrivere diversi tipi di ricerca dove le dimensioni caratteristiche sono dell’ordine dei nanometri. I principali approcci impiegati nell’assemblaggio del materiale sono: “top-down” (dal più grande al più piccolo) e “bottom-up” (dal più piccolo al più grande). Il primo consiste nel ridurre le dimensioni della struttura fino alla nanoscala. Il secondo, proposto per la prima volta nel 1959 da Richard Feyman nel congresso dell’American Physical Society, consiste nel partire da strutture nanometriche per realizzare dei sistemi più grandi attraverso assembly o selfassembly. Attualmente, i principali strumenti, per caratterizzare e manipolare nano strutture, sono SEM (Microscopia a Scansione Elettronica) TEM (Microscopia a Trasmissione Elettronica), AFM (Atomic Force Microscopy) e STM (Microscopia a corrente di Tunnelling). Nanotubi, fullerene e recentemente carbon nanohorns (CNHs) e carbon onions (multishell fullerene, CNOs) sono considerati buoni candidati per applicazioni in differenti settori delle nanotecnologie. CNOs e CNHs sono due nuove forme allotropiche di carbonio, scoperte rispettivamente da Ugarte nel 1992 e da Iijima nel 1999, che hanno attratto l’attenzione di molti ricercatori. Negli ultimi tre anni, diversi studi sono stati riportati sui CNHs mentre i CNOs sono ancora largamente inesplorati. I pristine carbon nanohorns (p-CNHs) e CNOs (p-CNOs) non sono solubili nei comuni solventi organici ma, per studiare le loro potenziali applicazioni nel campo delle scienze dei materiali, è necessario migliorarne la solubilità. Il primo aspetto, preso in considerazione in questa tesi di dottorato, riguarda la funzionalizzazione e la caratterizzazione dei CNHs. A tale proposito, è stato sintetizzato un amminoacido impiegato nella reazione di ciclo addizione 1,3-dipolare. Reazioni di amidazione e di addizione nucleofila, inoltre, hanno portato alla sintesi dei due primi sistemi in cui CNHs fungono da elettron accettori e la porfirina da elettron donatori al fine di studiare il trasferimento elettronico tra la porfirina ed CNHs. Successivamente, sia i CNOs di 5 nm (N-CNOs) che di 20 nm di diametro (A-CNOs) sono stati presi in considerazione e paragonati. Dato che gli N-CNOs risultano più reattivi, sono stati utilizzati nella sintesi di nuovi sistemi in cui CNOs fungono da elettron accettori ed il ferrocene da elettron attrattore. Per la prima volta, sono state eseguite delle misure di fotofisica e di elettrochimica del derivato ottenuto. La tesi è divisa in 4 capitoli. Il primo riguarda una descrizione panoramica delle diverse forme allotropiche del carbonio, in paricolare nanotubi e fullereni. Tecniche come arco elettrico, ablazione con laser di grafite e la deposizione mediante vapore chimico sono descritte brevemente. Quindi tre diversi approcci per funzionalizzare le nanoparticelle di carbonio sono riportati in dettaglio. Nel secondo capitolo sono stati introdotti i CNHs, le loro proprietà ed applicazioni ed un confronto tra i nanotubi e CNHs. Infine tre differenti studi sono stati affrontati: · Funzonalizzazione mediante cicloaddizione 1,3-dipolare per migliorare la solubilità dei CNHs; · Funzionalizzazione dei CNHs attraverso addizione nucleofila e reazione con la porfirina; · Funzionalizzazione dei CNHs mediante amidazione e reazione con la porfirina. Il trasferimento elettronico tra porfirina e CNHs è stato discusso. Nel terzo capitolo sono stati introdotti e confrontate le proprietà dei diversi tipi di CNOs. Successivamente e’ stato descritto uno studio relativo alla: · Funzionalizzazione mediante cicloaddizione 1,3 dipolare e reazione con l’acido carbossilico del ferrocene. L’nterazione elettronica tra il ferrocene ed i CNOs è stata studiata. Tutti i dettagli sperimentali sono descritti nel quarto capitolo.
“Functionalization and application of carbon nanohorns and carbon onions” Since the discovery of scanning probe microscope (SPM) in 1980 to that of fullerene, several Nobel Prizes have been awarded in Nanotechnology. Many companies are also currently working in this field such as IBM and Samsung. Government and corporations worldwide have invested over $ 4 billion into nanotechnology in the last year alone. What is exactly Nanotechnology? The word “Nanotechnology” is used to describe different types of research where the characteristic dimensions are in a nanometer range. Two main approaches are used to assemble materials at the nanoscale: “top-down” (from larger to smaller) and “bottom-up” (from smaller to larger). The first one consists in reducing the dimension of the structures until nano levels. The second one was proposed for the first time in 1959 by Richard Feyman in the annual congress of American Physical Society. It consists in using nanometric structure, such as a molecule, and to create a mechanism larger through a process of assembly or self-assembly. To characterize and manipulate nanostructures, sophisticated techniques are required. Presently the main instruments are SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), AFM (Atomic Force Microscopy), STM (Scanning Tunnelling Microscopy). Carbon nanoparticles such as carbon nanotubes (CNTs), fullerenes and recently carbon nanohorns and carbon onions, are considered good candidates in different nanotechnological applications. Carbon onions (multishell fullerene, CNOs) and carbon nanohorns (CNHs) are new allotropes of carbon. Discovered respectively by Ugarte in 1992 and by Iijima in 1999, these carbon nanoparticles start to attract the attention of many researchers. In the last three years, several studies have been reported about CNHs while CNOs are still largely unexplored. Pristine carbon nanohorns (p-CNHs) and CNOs are not soluble in common solvents. In order to study their potential applications in the field of material science, improving their solubility was necessary. First I focused my attention on the functionalization and characterization of CNHs. An aminoacid was synthesized and used in 1,3-dipolar cycloaddition reaction. This functionalization leads to an increase of the solubility of CNHs in various organic solvents. Using other reactions, such as amidation or nucleophilic additions, two assemblies, in which CNHs are electron acceptors and porphyrins the electron donors, were synthesized and the electron transfer between the porphyrins and the CNH core was studied. Then, CNOs either of 5 nm or 20 nm of diameter were synthesized, respectively by annealing of nanodiamonds and by arc discharge. These two samples of CNOs present different properties and reactivity. As CNOs produced by annealing of nanodiamonds are more reactive, they were used to synthesize a new assembly, in which CNOs are the electron acceptors and ferrocene the electron donors. For the first time, electrochemical and photophysical measurements of CNOs were performed. The thesis is divided in four chapters. The first one provides an overview of carbon allotropes, in particular CNTs and fullerenes. Different techniques as arc discharge, laser ablation and chemical vapour deposition are briefly described. Finally three general approaches to functionalize carbon nanoparticles are reported in detail. In the second chapter CNHs are introduced. The properties and the applications are shown. A comparison between CNTs and CNHs is also given. Then three different studies are presented: · Functionalization by 1,3-dipolar cycloaddition to improve the solubility of CNHs; · Functionalization by nucleophilic addition and coupling with porphyrin; · Functionalization by amidation and coupling with porphyrin. The electron transfer between the porphyrin and CNH core is discussed. In the third chapter CNOs are introduced. Two different type of CNOs are described and compared in order to choose the more reactive nanoparticles. Then a study is reported: · Functionalization by 1,3 dipolar cycloaddition and coupling with ferrocene carboxylic acid. The interaction between the ferrocene moiety and the CNOs is discussed. All the experimental details are given in the fourth chapter.
XX Ciclo
1976

We have measured adsorption isotherms at ten different temperatures from 90.432 K to 163.812 K for CF4 on a sample of chemically-opened carbon nanohorns. The interior of the individual nanohorns is accessible to sorbates in these chemically opened nanohorns. Two substeps are visible in the adsorption data, one corresponding to groups of stronger binding sites (lower pressure substep) and another corresponding to weaker binding sites (higher pressure substep). The stronger binding sites are interstitial pores and intra nanohorns pores and the weaker binding sites are outer surfaces and interior sites away from the tips. We have found that the isosteric heat is a decreasing function of coverage. Results for the effective specific surface area (≈969 m^2/gm), kinetics of adsorption, and the isosteric heat of adsorption as a function of sorbate loading will be presented. Comparison to absorption results for other sorbates on open carbon nanohorns will be discussed.

La caractérisation et modélisation de « nanohorns » monofeuillets (SWNH) et de forêts de nanotubes par microscopie analytique sont présentées ainsi que leurs applications pour le traitement du cancer. Dans une première partie, nous introduirons les méthodes de microscopie et de spectroscopie utilisées dans nos expériences. Nous étudierons ensuite le processus de croissance de forêts de nanotubes de carbone monofeuillets (dans le contexte d’une collaboration avec l'AIST au Japon). Les SWNH, leur structure, propriétés de remplissage et de fonctionnarisation seront analysés et une nouvelle méthode sera présentée pour l'étude de la porosité de matériaux inorganique en EELS. Des calculs ab-initio seront aussi utilisés pour étudier l'effet des défauts dans les parois des SWNH sur les phénomènes d'oxydation et de remplissage des SWNH. Finalement, nous étudierons les possibles applications de SWNH dans le domaine pharmaceutique, et en particulier pour les traitements cancéreux
In this manuscript, we will expose the characterization and modelling of Single Wall Nanohorns (SWNH) and Nanotube Forests by analytical microscopy and the functionalization of SWNH for drug delivery applications. Firstly, we will introduce the microscopy and spectroscopy methods used for our experiments. We will then study the growth process of Single Wall Carbon Nanotubes (SWCNT) forests (within the framework of a collaboration with AIST, Japan). SWCH, their structure, modifications and filling properties will be analysed in details. An original method will be presented to study the porosity of inorganic material with EELS. Ab initio calculation will also be used to explore the effect of the defects present in the SWNH wall on the oxidation and filling process. We will study the potentialities of Single Wall Carbon nanohorns as Drug Delivery Systems and particularly as anticancer drug carriers

Adsorption isotherms can be used to determine surface area of a substrate and the heat released when adsorption occurs. Our measurements are done determining the equilibrium pressures corresponding to a given amount of gas adsorbed on a substrate at constant temperature. The adsorption studies were done on aggregates of open dahlia-like carbon nanohorns. The nanohorns were oxidized for 9 hours at 550 °C to open them up and render their interior space accessible for adsorption. Volumetric adsorption measurements of Ne were performed at twelve different temperatures between 19 K and 48 K. The isotherms showed two substeps. The first substep corresponds to adsorption on the high energy binding sites in the interior of the nanohorns, near the tip. The second substep corresponds to low energy binding sites both on the outside of the nanotubes and inside the nanotube away from the tip. The isosteric heat measurements obtained from the isotherm data also shows these two distinct substeps. The effective surface area of the open nanotubes was determined from the isotherms using the point-B method. The isosteric heat and surface area data for neon on open nanohorns were compared to two similar experiments of neon adsorbed on aggregates of closed nanohorns.

Cancer therapies are often limited by bulk and cellular barriers to transport. Nanoparticle or chemotherapeutic compound intracellular transport has implications in understanding therapeutic effect and toxicity. The scope of this thesis was to study the intracellular transport of carbon nanohorns and to improve the efficacy of various chemotherapeutic agents through increased intracellular transport. In the first study, fluorescent probes (quantum dots) were conjugated to carbon nanohorns to facilitate the optical visualization of the nanohorns. These hybrid particles were characterized with transmission electron microscopy, electron dispersive spectroscopy and UV-VIS/FL spectroscopy. Their cellular uptake kinetics, uptake efficiencies, and intracellular distribution were determined in three malignant cell lines (breast – MDA-MB-231, bladder – AY-27, and brain – U87-MG) using flow cytometry and confocal microscopy. Intracellular distribution did not vary greatly between cell lines; however, the uptake kinetics and efficiencies were highly dependent on cell morphology. In the second study, the efficacy of various chemotherapeutic agents (i.e., doxorubicin, cisplatin, and carboplatin) was evaluated in AY-27 rat bladder transitional cell carcinoma cells. In the future, severe hyperthermia and chemothermotherapy (chemotherapy + hyperthermia) will also be evaluated. Doxorubicin and cisplatin compounds were more toxic compared to carboplatin. Hyperthermia has previously shown to increase the cellular uptake of chemotherapeutic agents; therefore, chemothermotherapy is expected to have synergistic effects on cell death. This work can then be translated to carbon nanohorn-based laser heating to generate thermal energy in a local region for delivery of high concentrations of chemotherapeutic agents. Although these two concepts are small pieces of the overall scope of nanoparticle-based therapies, they are fundamental to the advancement of such therapies.
Master of Science

Les nanotubes de carbone ou le graphène sont des formes allotropiques du carbone prometteuses pour un large domaine d'applications, mais des modifications de leur surface carbonée sont nécessaires pour leur manipulation et mise en forme. La fonctionnalisation covalente est un des moyens utilisés avec succès dans ce cadre, même si les modifications induites ne sont pas contrôlables. Les travaux réalisés au cours de cette thèse concernent l'utilisation de la réduction chimique des nanotubes et autres nanoformes de carbone, nanocornes, graphène ou nanodisques, pour d'une part obtenir des solutions stables et concentrées dans une gamme de solvants dépendant du type de nanoforme et d'autre part fonctionnaliser de manière covalente les différents types de surface carbonée de ces objets. Dans le cas des nanotubes, des molécules acceptrices ou donneuses d'électrons ont ainsi été greffées permettant la formation d'ensembles donneur-accepteur. D'autre part, le nombre de fonctions chimique greffées a pu être contrôlé, préservant ainsi les propriétés électroniques des nanotubes.

Carbon nanoparticles have the potential to significantly impact the medical field over the next decade. Currently, carbon nanoparticles are being studied for a myriad of applications, including drug delivery, selective laser therapy, imaging, and biosensing. The most common type of carbon particles being investigated are carbon nanotubes (CNTs). CNTs are attractive materials for medical applications because of their physical properties and the ease with which they can be surface modified; however, there is a great deal of controversy over their possible toxicity. A more novel type of CNT that was discovered in 1999 by Iijima et al. is the carbon nanohorn [1]. Individual single-walled nanohorns (SWNHs) are single graphene sheets that roll into a conical open ended structure. The open ends of these cones are then attracted to one another through van der Waals interactions and form a flower-like final structure [2]. SWNHs are more favorable for medical applications because they are produced without the use of metal catalysts abating the concern of toxicity associated with CNTs.

Laser therapies based on photochemical or photothermal mechanisms can provide a minimally invasive and potentially more effective treatment alternative to conventional surgical resection procedures by delivering prescribed optical/thermal doses to a targeted tissue volume with minimal damage to intervening and surrounding tissues. However laser therapy effectiveness is limited due to nonspecific excitation/heating of target tissue which often results in healthy tissue injury. Nanostructures targeted to tumor cells and utilized in combination with laser excitation can enhance treatment effectiveness by increasing thermal deposition and generating toxic photo-chemical mediators in the form of reactive oxygen species for targeted cell destruction.

Nanomaterials have been investigated for biomedical applications due to their unique properties. Their shape, size, surface, and material can be altered specifically for the type of application. Carbon nanomaterials (CNMs) have been effectively utilized as photoabsorbers to enhance laser-based therapies [1] and can be easily loaded with drugs or targeting moieties [2, 3]. The strong carbon bonds in this material provide a chemical and mechanical inertness that can serve as a barrier to protect chemotherapeutic agents from degrading quickly as they are transported to the site of interest [2].

Laser based photothermal therapy is a minimally invasive technique that relies on the absorption of energy by an irradiated tissue sample and results in the deposition of heat to destroy cancerous cells. The inclusion of nanoparticles that act as intense infrared absorbers allows for higher selectivity and additional absorption of laser energy into heat in the desired material. One promising carbonaceous nanoparticle is single walled carbon nanohorns (SWNHs) which have been demonstrated to be effective photoabsorbers [1].

Cancer remains one of the most deadly diseases today. Laser-induced photothermal therapy can provide a minimally invasive treatment alternative to surgical resection. The selectivity and effectiveness of laser therapy can be greatly enhanced when photoabsorbing nanoparticles such as nanoshells, single walled carbon nanotubes, multi-walled carbon nanotubes, or single wall carbon nanohorns (SWNHs) are introduced into the tissue. Prior studies have effectively used SWNHs combined with near infrared (NIR) laser light to target and destroy microbes [1]. We have previously reported increased tumor cell destruction when SWNHs were used in combination with laser therapy. The present work provides more extensive characterization of cell viability in response to laser therapy alone or in combination with SWNHs. Furthermore, the spatiotemporal temperature and cell viability in vitro in response to combinatorial SWNH-mediated laser therapies is determined using infrared thermometry and a novel viability algorithm, respectively. These new measurements will be critical for planning SWNH-mediated laser treatments where knowledge of the geometric distribution of temperature and cell death are critical to achieving the goal of selectively eliminating a tumor with specific spatial margins with minimal damage to surrounding healthy tissue.

Cancer is one of the most deadly diseases and leading cause of death. Laser based photothermal therapy can provide a minimally invasive alternative to surgical resection. The selectivity and effectiveness of laser therapy can be greatly enhanced when photoabsorbing nanoparticles such as nanoshells, single walled carbon nanotubes, multi-walled carbon nanotubes, or single wall carbon nanohorns (SWNHs) are introduced into the tissue[1]. Quantitative methods for measuring tumor response to nanoparticle enhanced laser therapies are critical for determining appropriate laser parameters and nanoparticle properties needed to achieve maximum therapeutic benefit. We have previously reported a new method for measuring two dimensional (2D) spatial viability distributions in cell monolayers in response to laser irradiation and nanoparticles. This method has been refined to allow determination of cell viability in three dimensions (3D) within a more physiologically representative tumor volume. This refined method was used to determine the viability of breast cancer cells suspended within sodium alginate tissue phantoms following treatment with SWNHs and external laser irradiation. The tumor treatment volume was accurately quantified in response to varying laser treatment parameters and nanoparticle concentrations. Spatial cellular viability was also measured in ex vivo pig bladders in response to SWNHs and laser irradiation to provide a more anatomically relevant environment. These new measurement methods enable quantification of spatial viability and therapeutic effectiveness, using 3D tumor environments which are more representative than cell monolayers.