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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Cu(I) catalyzed alkyne-azide cycloaddition as a synthetic tool for the preparation of complex C60 derivatives / La cycloaddition alcyne-azoture catalysée au cuivre (I) comme outil synthétique pour l'élaboration de dérivés complexe du C60

Vartanian, Maida 05 January 2012 (has links)
La présente thèse décrit la synthèse de briques de base de fullerènes pour la préparation de dispositifs moléculaires photoactifs combinant C60 et porphyrines. La cycloaddition alcyne-azoture catalysée au cuivre (I) a été utilisée comme outil de synthèse pour la préparation des dérivés C60 complexes.L’utilité synthétique de synthons C60 a été montrée avec la préparation d’édifices moléculaires complexes présentant des propriétés spécifiques pour diverses applications. Ainsi, un système photoactif flexible combinant C60 et porphyrine a été synthétisé. Cependant la flexibilité de l’espaceur liant les sous-unités de ce composé conduit à des variations de structurales importantes et complique ainsi l’analyse des études photophysiques.Dans ce contexte, nous nous sommes proposé dans une première partie de la présente thèse de parfaitement contrôler l’orientation et la distance des différentes sous-unités au sein de systèmes C60-donneurs. Afin de répondre à ce besoin, nous avons construit une brique de base de C60 rigide ayant un groupe azoture aromatique. Ainsi, la réaction « click » avec un phénylacétylène conjugué au groupement donneur conduit à un espaceur rigide entre les deux sous-unités.La deuxième partie de ce travail a été consacrée à la synthèse d’hexa-adduits du C60 portant différents groupements fonctionnels. Une méthode de synthèse permettant de préparer des hexa-adduits du C60 fonctionnalisés a été mise au point au laboratoire.Cette stratégie a été modifiée et des composés de C60 comportant dix fonctions azotures et une fonction alcyne protégée ont été synthétisés; dans ce cas il est possible d’introduire dans un premier temps par une réaction click dix groupes fonctionnels. Et dans un second temps; après déprotection de la fonction alcyne, une seconde réaction de click permet alors de greffer un fonctionnel différent. / The present PhD thesis manuscript is focused on the use of fullerene building blocks for the preparation of photoactive molecular devices combining C60 and porphyrins. Cu(I) Catalyzed alkyne-azide cycloaddition was used as a synthetic tool for the preparation of complex C60 derivatives. Specifically, in the first part (Chapter II-B), a flexible fullerene-porphyrin triad has been developed and the photophysical studies were performed. The flexible linker between the fullerene core and the azide groups prevented any conformational control on the relative orientation and distance between the two photoactive subunits connected together. This prompted the development of an analogous building block in which the azide unit is directly connected to the bridging phenyl ring (Chapter II-C). In this way, the click reaction with porphyrin-alkyne derivatives give access to hybrid systems with a controlled relative orientation of the two moieties. This is of fundamental importance for a better understanding of the structural parameters affecting the electron and/or energy transfer kinetic in such dyads.In the second part (Chapter III), a fullerene hexaadduct scaffold is used to build up sophisticated multiporphyrin systems for various applications. The preparation of these multi-chromophoric ensembles relies on the click-click approach developed in our group.
12

Φωτοκαταλυτική συμπεριφορά των στηριζόμενων σε οξειδικούς φορείς φουλερενίων

Νταραράς, Ευάγγελος 11 November 2008 (has links)
Στην παρούσα διατριβή μελετήθηκε η ετερογενοποίηση της αντίδρασης φωτοξείδωσης του 2 μεθυλ 2 βουτενίου προς αλλυλικά υδροπεροξείδια με τη χρήση φωτοκαταλυτών που περιέχουν φουλερένιο C60 στηριγμένο σε οξειδικούς φορείς. Το φουλερένιο C60 είναι γνωστό για τη δράση του ως φωτοευαισθητοποιητής της παραγωγής οξυγόνου απλής κατάστασης (singlet oxygen) κατά την ακτινοβόληση με ορατή ακτινοβολία, το οποίο πραγματοποιεί την οξείδωση αλκενίων μέσω της αντίδρασης Schenck-Ene. Ήταν επιθυμητό να παρασκευαστούν καταλύτες στους οποίους το C60 να διαθέτει σταθερή ομοιοπολική σύνδεση με την επιφάνεια των φορέων. Αυτό πραγματοποιήθηκε μέσω της σύνθεσης ενός μονοϋποκατεστημένου μεθανοφουλερενικού παραγώγου, το οποίο συνδέθηκε με την επιφάνεια των φορέων (Grafting). Επιπλέον, τα υλικά σχεδιάστηκαν έτσι, ώστε να παρέχουν τη δυνατότητα της πλήρους και ελεγχόμενης αποκοπής κάτω από κατάλληλες συνθήκες, γεγονός που επιτρέπει τον έλεγχο της ακεραιότητας του C60 μετά από χρήση του σε αντίδραση ή μετά από θερμική ή χημική κατεργασία. Παράλληλα παρασκευάστηκαν καταλύτες με κλασικές μεθόδους σύνθεσης ετερογενών καταλυτών. Ως φορείς χρησιμοποιήθηκαν η SiO2 και η Al2O3. Τα υλικά που παρασκευάστηκαν, μελετήθηκαν ως προς τη φωτοκαταλυτική τους δράση ως προς την αντίδραση φωτοξείδωσης του 2 μεθυλ 2 βουτενίου και έγινε σύγκριση τους με βάση τον τρόπο παρασκευής και το φορέα στήριξης. Ακόμη, έγινε σύγκριση της ετερογενούς διεργασίας με την ανάλογη ομογενή. Τα υλικά εμφάνισαν στο σύνολο τους φωτοκαταλυτική δράση στην παραπάνω αντίδραση. Σε κάθε περίπτωση οι στηριγμένοι σε SiO2 καταλύτες εμφάνισαν υψηλότερη δραστικότητα από τους αντίστοιχους που παρασκευάστηκαν σε φορέα Al2O3. Ακόμη, τα υλικά που παρασκευάστηκαν με τη μέθοδο Grafting σε φορέα SiO2 παρουσίασαν την υψηλότερη δραστικότητα ανάμεσα σε όλους καταλύτες που εξετάστηκαν. Η δραστικότητά τους ήταν μάλιστα υψηλότερη και από την αντίστοιχη που παρατηρήθηκε κατά τη χρήση ισομοριακής ποσότητας C60 σε ομογενή αντίδραση αλλά μικρότερη από αυτή των γνωστών φωτοκαταλυτών Rose Bengal και TPP (5,10,15,20-τετραφαινυλο-21Η,23Η-πορφυρίνης). Τέλος, μελετήθηκε η θερμική σταθερότητα των υλικών κάτω από οξειδωτικές συνθήκες. Διαπιστώθηκε ότι η σύνδεση του C60 στην επιφάνεια των φορέων με τη μέθοδο Grafting εμφανίζει γενικά παρόμοια θερμική σταθερότητα σε σχέση με τους καταλύτες που παρασκευάστηκαν με τη μέθοδο του Υγρού Εμποτισμού. / The scope of this dissertation was the heterogenization of the photooxidation reaction of 2-methyl-2-butene towards allylic hydroperoxides with the use of fullerene C60 containing catalysts supported on oxide carriers. The reaction was known to be efficient under homogeneous conditions. The photooxidation of alkenes is conducted by singlet oxygen (1Δg) which is produced by photosensitizers. C60 is known for its photosensitizing ability to produce singlet oxygen under visible irradiation. It was a requirement that C60 would be connected through stable and covalent bonding to the catalysts surface. This became possible through the preparation of a monosubstituted methanofullerene which was subsequently attached through covalent bonding to the surface of the carriers (Grafting). Additionally, a key requirement in the materials design was to provide us with the ability of controlled -under the appropriate conditions- and quantitative detachment of the part which bears C60, and its recovery in solution. This is important because it allows us to examine possible changes in the C60 molecule after the material’s use in catalytic processes or after its thermal or chemical treatment. Employing well-known methods of heterogeneous catalysts synthesis catalysts with the corresponding % molar concentration in C60 were also prepared. The photocatalytic behavior of the prepared materials was investigated in the photooxidation reaction of 2-methyl-2-butene. The effect of carrier and preparation method was also investigated. A comparison was also made with the homogeneous case. The prepared materials were all efficient catalysts in the photooxidation reaction of 2-methyl-2-butene. In all cases, the supported on SiO2 catalysts showed higher reactivity than the corresponding ones supported on Al2O3. Moreover, the catalysts prepared with the Grafting method on SiO2 showed the highest reactivity among all the catalysts examined. The reactivity was higher than in the homogeneous case using equimolar solutions of C60 but lower to the reactivity recorded in the case of the well established photosensitizers Rose Bengal and Tetraphenylporphine (TPP). Finally, the thermal stability of the prepared materials under oxidative conditions was studied._It was realized that materials prepared through Grafting show generally similar thermal behavior with the catalysts prepared with the Incipient Wetness method.
13

Étude de l'association supramoléculaire à l'état solide des fullerènes C60 et C70 avec des dérivés triptycényles fonctionnalisés

Raymond, François 08 1900 (has links)
Le fullerène C60 est une molécule sphérique composée exclusivement d'atomes de carbone. Ce composé possède une surface aromatique convexe homogène et peut s'associer, entre autres, avec des molécules possédant des surfaces aromatiques par des interactions non-covalentes. Le triptycène est une molécule en forme de "Y" qui possède des surfaces aromatiques convexes. Cette molécule possède l'habileté de s'associer avec le C60 par des interactions de type π qui sont amplifiées par la complémentarité des surfaces concaves et convexes impliquées dans les arrangements cristallins. Nous avons synthétisé des dérivés triptycényles portant des groupements fonctionnels aux extrémités des bras de ce noyau de façon à étendre les cavités disponibles pour interagir avec le C60. En effet, nous avons découvert que les atomes de chlore, de brome et d'iode ainsi que les groupements méthyle permettent d'étendre les surfaces disponibles pour interagir avec les fullerènes C60 et C70. Nous avons étudié les associations entre les dérivés triptycényles et les fullerènes par l'analyse des structures cristallographiques résolues par diffraction des rayons-X. De plus, nous avons étudié les associations entre les molécules considérées par l'analyse des surfaces d'Hirshfeld entourant les fullerènes. Découlant de ces études, l'effet d'amplification des atomes de chlore, de brome et d'iode ainsi que les groupements méthyle a été employé pour identifier de nouveaux solvants aptes à solubiliser efficacement le C60. / The fullerene C60 is a spherical molecule made up exclusively of carbon atoms. The surface of this compound is homogenous, convex and aromatic. As a result, C60 can associate with other aromatic molecules via non-covalent π-stacking interactions to form supramolecular assemblies. The triptycene is a "Y"-shaped molecule with concave aromatic surfaces. This molecule can thereby interact with C60 and form crystals through amplified π-stacking interactions resulting from the concave/convex complementary arrangement. In the course of our work, we made a series of new triptycene derivatives with functional groups added to the periphery of the aromatic core. In particular, we found that methyl groups, as well as atoms of chlorine, bromine and iodine, can be placed on the extremities of the triptycene core to expand the concave cavities available to interact with C60 and C70. We studied the non-covalent interactions between fullerenes and triptycene derivatives using X-ray crystallography. Furthermore, Hirshfeld surfaces have been used to map the interaction patterns around fullerene surfaces. In addition, we have found that aromatic solvents that are properly functionalized with halogen atoms and methyl groups have a special ability to solubilize C60.
14

Investigating excited electronic states in fullerenes and polycyclic aromatic hydrocarbons using Femtosecond Laser Photoelectron spectrometry

Bohl, Elvira January 2016 (has links)
Fullerenes have highly excited electronic states with interesting properties for possible wide ranging applications including in electronics. These highly excited, Rydberg-like states, so-called superatom molecular orbitals (SAMOs), are diffuse low-angular momenta states with molecular orbitals centred on the hollow fullerene core. The SAMOs can be detected by femtosecond photoelectron spectroscopy (PES) and characterised by photoelectron angular distributions (PADs) combined with time-dependent density functional theory (TD-DFT) calculations. The photoelectron spectra of C60 and C70 show a peak structure below kinetic energies corresponding to the photon energy, superimposed on a thermal electron background. This peak structure was assigned to one-photon ionisation of the SAMO states based on PAD and TD-DFT. In this thesis, studies of the fullerene species C82 and Sc3N@C80 revealed PES and PAD with similar features to C60 and C70. The SAMO peaks became less prominent compared to the thermal electron background for increasing molecular size and decreasing symmetry, and were almost absent for the endohedral species. To provide more information about the influence of encapsulated atoms in the fullerene cage on the SAMO states, experiments on Li@C60 have been carried out. A lower thermal electron emission temperature and a splitting of the SAMO peaks has been observed for Li@C60 compared to C60. Nevertheless the binding energies are remarkably similar in all investigated fullerenes, which is important for any applications. Since the binding energies are about the same, but the ionisation potentials of the fullerenes are different, the excitation energy to the SAMOs scales with the ionisation energy. The reasons for the well-pronounced peak structure of the SAMO states in the PES of C60 could be explained by the similarity of the SAMOs to Rydberg states along with the higher photoionisation probabilities compared to valence states which were modelled by Benoît Mignolet and Françoise Remacle. As the SAMOs are highly excited electronic states, like Rydberg states, the potential energy surface of the neutral molecule and the ionised molecule are similar. Therefore the vibrational energy is conserved in the molecule during the photoionisation on the femtosecond time scale. The TD-DFT calculations on C60, carried out by Benoît Mignolet and Françoise Remacle, revealed the photoionisation probabilities of the SAMOs to be at least three orders of magnitude higher than for non-SAMOs for the applied experimental conditions. To test the prediction of the model, the relative photoionisation probabilities of the s-SAMO to p-SAMO and the s-SAMO to d-SAMO were obtained experimentally from the PES at various photon energies (2-3.5 eV) within this work. The analysis indicates remarkable agreement between the experiment and the theoretical values. Further quantum chemical calculations on a series of polycyclic aromatic hydrocarbons (PAHs) were carried out within this thesis, which revealed similar Rydberg-like molecular orbitals in analogy to the SAMOs in fullerenes. The first series included benzene, naphthalene, anthracene, tetracene, pentacene and hexacene. The second series consisted of phenanthrene, pyrene and coronene. Finally, the third series covered cubane, adamantane and dodecahedral C20. All modelled molecules showed diffuse, excited electronic states similar to the SAMOs. Within each series the binding energies of these states decrease with increasing molecular size as well as the ionisation energies, except for the 3rd series. A comparison between all series shows that the binding energies of the states for the 3rd series (the 3-D series) are slightly higher than for the 1st and 2nd series in relation to similar molecular size. The results of the coronene calculations are compared to experimental photoelectron spectra and are shown to be in good agreement with the experiments.
15

Secondary ion emission under keV carbon cluster bombardment

Locklear, Jay Edward 30 October 2006 (has links)
Secondary ion mass spectrometry (SIMS) is a surface analysis technique capable of providing isotopic and molecular information. SIMS uses keV projectiles to impinge upon a sample resulting in secondary ion emission from nanometric dimensions. It is well documented that secondary ion emission is enhanced using cluster projectiles compared to atomic projectiles. Previous studies of enhanced secondary ion yields with cluster projectiles have led to the present study dealing with the scope of C60 as a projectile for SIMS. The secondary ion yields (i.e., the number of secondary ions detected per projectile impact) from impacts of 10-26 keV C24H12+, C60+, gramicidin S+ and C60F40+ projectiles were examined to compare the effectiveness of the projectiles. The [M-H]- secondary ion yields from several organic samples varied inversely with the molecular weight. Multiple ion emission decreases monotonically as a function of the number of secondary ions emitted per impact and varies with impact energy such that higher energies produce more multiple ion emission. The emission of CN- from biological samples as a function of carbon-based projectile characteristics was examined to explore the possibility of using CN- as a molecular identifier. CN- emission was found to be the product of both direct and recombination/rearrangement emission. Re-emitted projectile atoms in the form F- were found under C60F40+ bombardment. Two forms of re-emitted F- were found: One form in which F atoms retained a portion of the initial kinetic energy, and a second in which the F atoms deposited most of the initial kinetic energy into the surface before being ejected. The [M-H]- secondary ion yield of gramicidin S was increased ~ 15 times by embedding the analyte in a matrix of sinapic acid. These results show the optimum carbon based projectile for a given sample is dependent upon the signal to be monitored from the surface. The results also show CN- has potential as a molecular identifier. Additionally, the detection of re-emitted F- confirms prior predictions of re-emitted projectile atoms.
16

Photo-polymerization as a tool for engineering the active material in organic field-effect transistors

Dzwilewski, Andrzej January 2009 (has links)
The emergence of organic semiconductors is exciting since it promises to open up for straightforward and low-cost fabrication of a wide range of efficient and novel electronic devices. However, in order for this promise to become reality it is critical that new and functional fabrication techniques are developed. This thesis demonstrates the conceptualization, development, realization and implementation of a particularly straightforward and scalable fabrication process: the photo-induced and resist-free imprint patterning technique.Initial experiments revealed that some members of a group of carbon-cage molecular semiconductors – termed fullerenes – can be photochemically modified into dimeric or polymeric structures during exposure to laser light, and, importantly, that the exposed fullerene material retains its good electron-transport property while its solubility in common organic solvents is drastically lowered. With this information at hand, it was possible to design and create well-defined patterns in a solution-deposited fullerene film by exposing selected film areas to laser light and then developing the entire film in a tuned developer solution. An electronically active fullerene pattern emerges at the locations defined by the incident laser beam, and the patterning technique was successfully utilized for the fabrication of arrays of efficient field-effect transistors.In a later stage, the capacity of the photo-induced and resist-free imprint technique was demonstrated to encompass the fabrication of ubiquitous and useful CMOS circuits. These are based on a combination of p-type and n-type transistors, and a blend between a p-type organic semiconductor and an n-type fullerene compound was designed so that the latter dominated. By solution-depositing the blend film on an array of transistor structures, exposing selected transistors to laser light, and then developing the entire transistor array in a developer solution, it was possible to establish a desired combination of (non-exposed) p-type transistors and (exposed) n-type transistors. We finally utilized this combination of transistors for the fabrication of a CMOS circuit in the form of well a-functional organic inverter stage.
17

Chimie du dianion C60(2-): accès à de nouveaux dérivés fonctionnels du fullerène C60. Application à la synthèse de dyades et triades, et études de leurs propriétés

Chopin, Stéphanie 24 September 2004 (has links)
De nouveaux dérivés fonctionnels du fullerène C60 ont été synthétisés à partir du dianion C602- selon la méthodologie mise au point au Laboratoire :- des dihydrofullerènes C60(CH2CO2R)2 (R = Me, Et). Des cellules photovoltaïques à base de ces dérivés et de MEH-PPV en réseaux interpénétrés montrent de bonnes performances, assez proches de celles obtenues lorsque l'accepteur est le PCBM ;- des dihydrofullerènes fonctionnels dissymétriques C60RR'. Les synthèses correspondantes reposent sur l'exploitation, jusqu'alors non réalisée dans ce but, du mécanisme réactionnel (Kadish-Fukuzumi) de la réaction entre C602- et divers dérivés halogénés ;- un fullerène diol, issu de dérivés du pentaérythritol. Les bons rendements obtenus pour cette synthèse font de ce fullerène diol un nouveau synthon de choix en chimie du fullerène C60.A partir de ce fullerène diol, de nouvelles dyades et triades ont été obtenues, l'entité électro-donneur étant le motif tétrathiafulvalène ou l'anion perchlorotriphénylméthyle. Les propriétés physico-chimiques de ces assemblages covalents donneur-accepteur ont été étudiées (spectroscopies UV-Vis, fluorescence, RPE ; électrochimie ; photophysique). / New functionalized [60]fullerene derivatives have been synthesized starting from C602- anion, following the procedure previously developed in our Laboratory :- dihydrofullerenes C60(CH2CO2R)2 (R = Me, Et). Solar cells have been built using a mixture of these compounds and MEH-PPV in interpenetrating network and they exhibit good photovoltaic characteristics, which are close to those obtained when the acceptor is PCBM ;- functionalized dissymmetric dihydrofullerenes C60RR'. The corresponding syntheses lie upon a new interpretation of the Kadish-Fukuzumi mechanism, so far unexplored in this way, associated with the reaction between C602- and various halogeno derivatives ;- a fullerene diol, issued from pentaerythritol derivatives. Thanks to good yields observed in this synthesis, this fullerene diol appears to be a new promising building block in fullerene chemistry.Starting from the latter diol, new C60-based dyads and triads have been obtained, the electron donor moiety being the tetrathiafulvalene core or the perchlorotriphenylmethyl anion. The physico-chemical properties of these donor-acceptor covalent assemblies have been studied (UV-Vis, fluorescence, ESR spectroscopic methods ; electrochemistry ; photophysics).
18

Secondary ion emission under keV carbon cluster bombardment

Locklear, Jay Edward 30 October 2006 (has links)
Secondary ion mass spectrometry (SIMS) is a surface analysis technique capable of providing isotopic and molecular information. SIMS uses keV projectiles to impinge upon a sample resulting in secondary ion emission from nanometric dimensions. It is well documented that secondary ion emission is enhanced using cluster projectiles compared to atomic projectiles. Previous studies of enhanced secondary ion yields with cluster projectiles have led to the present study dealing with the scope of C60 as a projectile for SIMS. The secondary ion yields (i.e., the number of secondary ions detected per projectile impact) from impacts of 10-26 keV C24H12+, C60+, gramicidin S+ and C60F40+ projectiles were examined to compare the effectiveness of the projectiles. The [M-H]- secondary ion yields from several organic samples varied inversely with the molecular weight. Multiple ion emission decreases monotonically as a function of the number of secondary ions emitted per impact and varies with impact energy such that higher energies produce more multiple ion emission. The emission of CN- from biological samples as a function of carbon-based projectile characteristics was examined to explore the possibility of using CN- as a molecular identifier. CN- emission was found to be the product of both direct and recombination/rearrangement emission. Re-emitted projectile atoms in the form F- were found under C60F40+ bombardment. Two forms of re-emitted F- were found: One form in which F atoms retained a portion of the initial kinetic energy, and a second in which the F atoms deposited most of the initial kinetic energy into the surface before being ejected. The [M-H]- secondary ion yield of gramicidin S was increased ~ 15 times by embedding the analyte in a matrix of sinapic acid. These results show the optimum carbon based projectile for a given sample is dependent upon the signal to be monitored from the surface. The results also show CN- has potential as a molecular identifier. Additionally, the detection of re-emitted F- confirms prior predictions of re-emitted projectile atoms.
19

Photochemistry and photobiological implications of functionlazied fullerenes in aqueous systems

Snow, Samuel D. 21 September 2015 (has links)
Fullerenes have been the focus of significant research effort and curiosity for their unique physicochemical and photochemical properties since their discovery almost 30 years ago. C60 fullerene in particular has received tremendous attention, due to its prevalence in fullerene production and chemical stability. While ambitious prospective applications for C60 have been ubiquitous, the extremely hydrophobic nature of fullerenes and consequent aggregation at the nano scale has hampered many endeavors. Researchers, therefore, have turned their attention to the functionalization of fullerenes to add hydrophilic moieties for applications in aqueous media. It is known that functionalizing the C60 cage alters its innate physicochemical and photochemical properties, but how these changes translate to the properties of C60 aggregates, often termed nC60, is not well understood. Functionalized fullerenes present an intriguing environmental dichotomy. On the one hand C60 has excellent potential as a novel singlet oxygen producing disinfection tool, and on the other the potential toxicological effects of functionalized C60 are largely unknown. With thousands of possible functionalities, a mechanistic understanding of the effects of functionalization is essential. To explore the effects of functionalization on fullerene photochemistry in relevant systems, three types of functional groups were selected and obtained each in series of mono-, bis-, and tris-functionalized forms. Two functionalities contrasted the presence or lack of a quaternary ammonium group and the third was the sterically bulkier phenyl-C61 butyic acid methylester, which is commonly used in polymer photovoltaics. The fullerenes were characterized for innate photochemical properties in organic solvents using UV/Vis, laser flash photolysis, and photochemical degradation experiments. Aqueous aggregates of each derivative were additionally characterized for their physical and chemical properties by dynamic light scattering, transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. All derivatives were photoactive when dispersed molecularly in organic solvents, but only the cationic fullerenes showed significant photoactivity as aqueous aggregates. Differences in aggregate size or crystallinity were unable to explain the differential photoactivity between derivatives, contrary to two established hypotheses. Antimicrobial properties were probed using innate toxicity tests and photoinactivation experiments. Again, only the cationic fullerenes were found to exert photochemical action towards Escherichia coli or MS2 bacteriophages. The cationic fullerenes were also innately toxic to E. coli due to the presence of quaternary ammonium moieties. In order to establish a mechanistic understanding of the photochemistry of functionalized C60 aggregates, simulations of the molecular dynamics (MD) were employed and compared with empirical evidences. Simulations provided theoretical values for C60-O2, C60-C60, and C60-H2O interactions for each derivative. Trends observed in the MD results were compared to photochemical characterizations as described above and Raman spectroscopic measurements of C60’s effect on localized water structure. High resolution transmission electron microscopy was used to provide empirical evidence of the C60-C60 interactions. Overall, fullerene aggregate photochemistry is likely driven by aggregate morphology and by intermolecular interactions between fullerenes, water, and O2.
20

Effectof Growth Time, Growth Temperature and Light  on Growth Mechanism of C60 nanorods

ABUDULIMU, ABASI January 2013 (has links)
In this thesis work C60 nanorods were produced by Liquid-Liquid Interfacial Precipitation method (LLIP) assisted with 10 s of weak sonication. Ethanol and m-dichlorobenzene were used as poor and good solvents of C60, respectively. Five different temperatures, 4, 10, 20, 30, 40 and 50                         , were chosen as growth temperatures of different samples to investigate the effect of temperature on the grown structures. Different samples were prepared in the dark and under the light with various growth time to determine the effect of light and growth time on growth of C60 nanorods. The characterization of the grown C60 nanorods were conducted by transmission electron microscopy (TEM) and x-ray diffraction (XRD). The result of characterization indicated that the sonication introduced smaller C60 nanostructures; light irradiation and temperature increase (till 40 C0) during the growth time resulted in nanorods with smaller diameter, whereas the long growth time lead to the increase of the diameter of C60 nanorods. The as-grown C60 nanorods synthesized at different conditions possess an hcp crystal structure.

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