Two novel synthetic routes to formation of gold-magnetite nanoparticles have been designed. Treatment of preformed magnetite nanoparticles with ultrasound in aqueous media with dissolved tetrachloroauric acid resulted in the formation of gold-magnetite nanocomposite materials. The other route involved irradiation of preformed magnetite nanoparticles by UV light in aqueous media with dissolved tetrachloroauric acid. This method resulted in the formation of gold-magnetite nanocomposite materials. These materials maintained the morphology of the original magnetite particles. The morphology of the gold particles could be controlled by adjusting experimental parameters, like addition of small amounts of solvent modifiers such as methanol, diethylene glycol, and oleic acid as well as variation of the concentration of the tetrachloroauric acid solution and time of the reaction. The nanocomposite materials were magnetic and exhibited optical properties similar to gold nanoparticles. Since we were not able to directly synthesize core shell gold magnetite nanoparticles, TiO2 was used as a bridging material. TiO2 nanoparticles with embedded magnetite were suspended in aqueous HAuCl4 and irradiated with ultraviolet light to photodeposit gold. The degree of gold coating and the wavelength of absorbance could be controlled by adjusting concentration of HAuCl4. Absorbance maxima were between 540-590 nm. Particles exhibited superparamagnetic properties (blocking temperature ~170 K) whether or not coated with gold. These particles have potential applications as drug delivery agents, magnetic imaging contrast agents, and magnetically separatable photocatalysts with unique surface properties. Another goal was to synthesize and characterize indium doped magnetite nanoparticles for application as radiotracers for in vivo fate studies. The labeled particles will be useful for determination of pharmacological behavior in biological systems. Indium doped magnetite particles with varying size and surface chemistry were synthesized with wet chemical techniques. The synthesized nanoparticles were characterized in terms of the size and shape with the help of TEM, the elemental composition by ICP and EDS, the crystal structure by XRD and magnetic properties by SQUID measurements. It was found that the indium loading could be controlled even though the magnetic properties were similar to undoped magnetite.

The self-assembly of isotropic and anisotropic colloidal particles into higher-ordered structures has been of great interest recently due to the promise of creating metamaterials with novel macroscopic properties. The physicochemical properties of these metamaterials can be tailored to achieve composites with tunable functionalities. The formation of these metamaterials can be used as a pathway to emulating advanced biological systems. In particular, synthetically mimicking the surface of a moth’s eye, which consists of arrays of ellipsoidal protuberances, can be used as a strategy for fabricating antireflective coatings. To enable this technology, it is necessary to design a synthesis scheme that produces micron-sized composite particles with tunable refractive index. In the future, the resulting composite microparticles can then undergo geometric and spatial modifications to form self-assemblies that have unique macroscopic material properties. This research work delineates a strategy of developing microparticles with a hybrid configuration that constitutes an inorganic and an organic part. The inorganic part comprises ~30 nm diameter titania (TiO2) nanoparticles, which are embedded within an organic polymer particle comprised of diethyl methylene malonate polymer [p(DEMM)]. Anionic polymerization is modified to controllably incorporate TiO2 nanoparticles into the polymer matrix. A design of experiments was identified and carried out to identify the major process variables that influence the final particle size. In particular, since DEMM polymerization may be initiated entirely by the presence of hydroxyl anions, pH was found to control the final overall particle diameter between 300 nm and 1 micrometer. The overall inorganic particle loading can be readily modified and is confirmed by thermogravimetric analysis, allowing for the desired macroscopic refractive index to be controlled. Light scattering, scanning electron microscopy and zeta potential analysis reveals that the colloidal stability of the hybrid microparticles is dependent on the ligand coating the inorganic constituent. In addition, this synthetic scheme is applied to different inorganic constituents that have interesting functionalities, such as fluorescent CdTe quantum dots, in order to show the methods versatility method to produce composite particles for a wide spectrum of applications. These initial investigations provide a the synthetic groundwork to evaluating the coating properties of the microparticles and their self-assembly into novel materials in the future.

No description available.

Deux configurations différentes, à savoir en microcanal et en cuve de spectroscopie utilisant un laser UV, sont conçues pour effectuer la photodéposition de plots métalliques uniques sur du TiO2. Des nanoparticules cristallines d’anatase de formes et de tailles variées sont synthétisées à dessein et utilisées comme semi-conducteurs pour cette réaction photochimique. Quatre précurseurs de métaux avec différents états de valence (Ag (I), Au (III), Pd (II) et Pt (IV)), sont réduits de manière photochimique à la surface de TiO2. Plusieurs techniques, notamment XPS, TEM / HRTEM, spectroscopie UV-vis, sont utilisées pour caractériser l'état chimique, la distribution en taille et en nombre des points métalliques et le comportement d'absorption des nanoparticules Metal-TiO2. On obtient des nano-hétérodimères avec un plot Ag, Au, Pd et Pt par TiO2, ce qui montre que le dépôt au laser semble être beaucoup plus efficace dans ce cas que celui de la photodéposition par lampe UV habituelle, suggérant que le flux de photons compte beaucoup plus que l'énergie déposée. Les hétérodimères Ag-TiO2 sont synthétisés avec succès par les deux méthodes de dépôt au laser. Le nombre et la distribution de taille des plots d’Ag dépendent des capteurs de trous, du pH et du précurseur métallique. Un modèle de croissance prédit bien la variation de la taille de l'argent dans le processus de photodéposition. L'extension de la synthèse à d'autres précurseurs métalliques (KAuCl4, Na2PdCl4 et H2PtCl6) à l'aide des deux configurations a conduit à la formation d'hétérodimères de TiO2 à base d'or, de palladium et de platine. La loi de croissance de l'or peut aussi être raisonnablement prédite, bien qu'elle ne soit pas aussi bonne que dans le cas de l'Ag, alors que notre modèle ne fonctionne pas dans le cas de Pd et de Pt. Enfin, des nanoobjets bimétalliques à structure coeur-écorce (Au@M)-TiO2 (M = Ag, Pd, Au et Pt) ont été synthétisés avec succès par une méthode de dépôt simple par laser UV en deux étapes en configuration cuve de spectroscopie. / Two different setups, namely microchannel and cuvette setups using UV laser, are built to perform the photodeposition of a single metal dotson TiO2. Crystal anatase TiO2 nanoparticles with various shapes and sizes, are synthesized on purpose and used as semiconductors for this photochemical reaction. Four metal precursors with different valence states, i.e. Ag(I), Au (III), Pd(II) and Pt(IV) ions, are photochemically reduced on the surface of TiO2. Several techniques, including XPS, TEM/HRTEM, UV-vis spectroscopy, are performed to characterize the chemical state, size and number distribution of metal dots, and the absorption behaviours of the Metal-TiO2 nanoparticles. Nano-heterodimers with one Ag, Au, Pd and Pt per TiO2 are obtained showing that laser deposition seems to be much more efficient in this case than of the usual UV lamp photodeposition, suggesting that the flux of photons matters much more than the deposited energy. Ag-TiO2 heterodimer nanoparticles are successfully synthesized by the two laser deposition methods. The number and size distribution of Ag dots are dependent on hole scavengers, pH and metal precursor. A growth model well predicted the silver size variation in the photodeposition process. Extending the synthesis to other metal precursors (KAuCl4, Na2PdCl4 and H2PtCl6) using both setups led to the formation of gold, palladium and platinum-based heterodimers with TiO2. The growth law of gold can reasonably be predicted as well, although it is not as good as in the case of Ag, while our model did not work in the case of Pd and Pt. Finally, bimetallic core-shell structured (Au@M)-TiO2 (M=Ag, Pd, Au and Pt) nanoobjects were successfully synthesized by a simple two-step UV laser deposition method in the cuvette setup.

De nos jours, afin de réduire le frottement et l'usure dans les moteurs thermiques et par voie de conséquence les émissions polluantes ainsi que la consommation énergétique, des revêtements APS (Atmospheric Plasma Spray) sont appliqués sur les chemises des cylindres. Le MoDTC (Di-ThioCarbamate de Molybdène), est un additif organométallique largement utilisé dans la lubrification automobile pour réduire le frottement grâce à la formation sur les surfaces frottantes de feuillets de MoS2. Ce travail de thèse porte sur l’étude de la réaction tribochimique du MoDTC avec le revêtement TiO2 APS dans des conditions de lubrification mixte / limite. Des poudres de TiO2 de taille micrométrique ont été utilisées pour obtenir un revêtement APS de TiO2 de 70 µm d'épaisseur. Différents tribomètres ont été utilisés pour effectuer des essais de frottement en présence d’une huile de base contenant du MoDTC. Les résultats obtenus pour un contact acier / TiO2 APS lubrifié avec du MoDTC présente une réduction significative du frottement par rapport au contact acier / acier (contact de référence). Les analyses de surface montrent que le tribofilm formé sur le plan de TiO2 APS est composé de MoS2 et de MoO3 tandis qu’il est constitué d’oxysulfure de molybdène, de MoS2 et de MoO3 sur le plan de référence en acier. De plus, les résultats indiquent que des phases Magneli résistantes à l'usure sont formées sur la surface du plan de TiO2 réduisant ainsi l'usure du contact lorsque celui-ci est uniquement lubrifié avec l'huile de base. L'impact de divers paramètres tels que la rugosité, la température d'essai, la pression de contact, la concentration en MoDTC et le remplacement des billes en acier par des billes en céramique sur le comportement tribologique du TiO2 APS a également été étudié. Les résultats ont été comparés avec ceux obtenus dans les mêmes conditions avec un contact acier / acier de référence et révèlent que le coefficient de frottement est toujours plus faible dans le cas des contacts impliquant un revêtement de TiO2 APS. Des résultats similaires à ceux obtenus avec le TiO2 APS (en termes de comportement tribologique et de composition chimique du tribofilm) ont été obtenus avec des nanoparticules de TiO2 mélangées dans l’huile de base avec du MoDTC dans le cas d'un contact acier / acier de référence. Dans les deux cas, une décomposition complète de MoDTC conduisant à la formation de MoS2 a été observée. Un phénomène de tribocatalyse a été suggéré comme pouvant être le mécanisme responsable de la décomposition du MoDTC en présence de matériaux à base de TiO2 comme le revêtement TiO2 APS et les nanoparticules de TiO2. / Nowadays to reduce friction and wear as well as gas emission and oil consumption of the passenger car engines, Atmospheric Plasma Spray (APS) coatings are used on cylinder liner. MoDTC (Molybdenum Di-Thiocarbamate), organometallic friction modifier has been previously used to reduce friction by formation of layered molybdenum disulphide flakes. This study focuses on tribochemical interaction of MoDTC with TiO2 APS coating under mixed / boundary lubrication conditions. Fused and crushed micron sized powders were used to obtain a 70 µm thick TiO2 coating. Various tribometers were used to carry out tribotests in presence of lubricant containing MoDTC. Steel / TiO2 APS contact showed significant friction reduction than steel / reference steel contact. It was shown that the tribofilm is composed of MoS2 and MoO3 on TiO2 APS flats while it is composed of Mo-oxysulphide, MoS2 and MoO3 on reference steel flats. It was shown that wear resistant Magneli phases are formed on the surface of TiO2 APS disc, decreasing wear when the contact was lubricated only with base oil. Impact of various parameters like roughness, test temperature, contact pressure, concentration of MoDTC and change of counterpart materials from steel balls to ceramic balls, on the tribological behavior of TiO2 APS was also studied. Results obtained were compared with contacts involving reference steel and it was confirmed that friction coefficient was always lower in case of contacts involving TiO2 APS coating. Similar tribological results and chemistry were obtained for TiO2 nanoparticles blended with MoDTC in case of steel / reference steel contact. Both the cases, TiO2 APS and TiO2 nanoparticles showed complete decomposition of MoDTC to form MoS2. Tribocatalysis was suggested as the mechanism responsible for complete decomposition of MoDTC in case of TiO2 based materials like TiO2 APS coating and TiO2 nanoparticles

Les dispersions colloïdales de nanoparticules (NPs) sont très répandues dans l'industrie, et permettent d'éviter l'utilisation de NPs sèches, controversée pour des raisons de toxicité. Le contrôle des interactions entre les NPs et le milieu dispersant reste le point clé de ces systèmes. La modulation de ces interactions permet de contrôler l'état de dispersion des NPs dans les sols. De plus, les nanocomposites NPs-polymère se sont avérés prometteurs pour une large gamme d'applications, ainsi l'utilisation de sols pourrait présenter une voie avantageuse d'incorporation des NPs dans le polymère, tout en offrant la possibilité de contrôler leur état de dispersion, et in fine les propriétés du matériau, celles-ci étant liées à l'état de dispersion des NPs. L'objectif de ce travail de thèse est le développement de méthodes de modification de surface de NPs d'oxyde en dispersion colloïdale, tout en contrôlant la dispersion des NPs dans les sols et dans les nanocomposites issus de ces sols. Puis, l'évaluation de cet état de dispersion par SAXS. Deux méthodes de modification de surface ont ainsi été développées : la première implique le greffage d'acides phosphoniques sur des NPs de silice recouvertes d'alumine en dispersion dans l'eau, et la seconde met en jeu le greffage d'acides phosphoniques sur des NPs de TiO2 et leur transfert d'une phase aqueuse à une phase CHCl3. Les NPs modifiées ont été caractérisées par diverses méthodes. Leur état de dispersion a été étudié par DLS et SAS. De plus, pour les NPs de silice-amine, l'impact de la densité de greffage du C8PA sur la structure des NPs (à l'état sec) a été mis en évidence par SAXS et différents processus de relaxation ont été étudiés par BDS pour les NPs nues et modifiées. Enfin, ces NPs ont été incorporées dans un polymère de PEA par voie aqueuse via des latex et leur état de dispersion dans les composites a été mesuré par SANS. / Colloidal nanoparticles (NPs) dispersions are largely used in the industry, and avoid the use of dried NPs, which is controversial due to safety concerns. The key point in such systems remains the control of the interactions with the dispersed medium and between the NPs. Mastering these interactions allows controlling the NPs' state of dispersion. Moreover, as polymer-NPs nanocomposites have been found promising for a wide variety of applications, the use of colloidal sols could thus be an advantageous way of NPs' incorporation in the polymer, with a possible control of the NPs state of dispersion, and finally on the properties of the material, as they are linked to the NPs' dispersion. The purpose of this PhD work is to develop surface-functionalization methods of oxide NPs in colloidal sols in order to control the dispersion of NPs in the sols and in polymer nanocomposites derived from these sols, and to evaluate this dispersion using SAXS. Two surface modification methods have been developed to obtain aqueous or organic sols of functionalized NPs. The first one concerns the reaction in water of alumina-coated silica NPs with phosphonic acids (PAs), and the second one involves the simultaneous grafting and phase transfer of TiO2 NPs from an aqueous to a CHCl3 phase using PAs. The resulting NPs were characterized and their state of dispersion was monitored by DLS and SAS measurements. The impact of the C8PA grafting density on the structure of modified alumina-coated silica NPs in the dried state was evidenced by SAXS. The different relaxation processes of bare and grafted NPs were studied by BDS. These NPs were then incorporated in a PEA polymer by an aqueous latex route, and their structure in the nanocomposites was investigated by SANS.

Le développement de procédé évoluant à la pression atmosphérique représente un enjeu majeur dans le dépôt de couches minces nanocomposites. Parmi ces procédés, les Décharges à Barrières Diélectriques présentent l'avantage d'être un procédé vert sans effluent gazeux, pouvant facilement être intégrées dans une chaine de production industrielle. L'approche choisie pour la réalisation de couches minces nanocomposites repose sur l'injection sous forme d'aérosol d'une suspension colloïdale dans la DBD. Les nanoparticules semi-conductrices de TiO2 sont choisies et mise en suspension dans un alcool polymérisable tel que l'isopropanol. L’objectif de ce travail est de contrôler le transport des nanoparticules et la croissance de la matrice dans la DBD en vue de réaliser une couche mince nanocomposite.Différentes méthodes de formation de l'aérosol et de filtration sont évaluées, ainsi que différents gaz vecteur (Ar, N2). Dans tous les cas considérés, la décharge est filamentaire.L'estimation des valeurs des différentes forces s'exerçant sur une nanoparticule dans une DBD confortée par un modèle numérique à permis d'orienter les expérimentations. Il est ainsi possible, à partir des paramètres permettant de générer le plasma, d'influencer le dépôt des nanoparticules et la croissance de la matrice. Les dépôts obtenus sont analysés ex situ par microscopie électronique à balayage, spectroscopie infrarouge, Raman et à rayon X et in situ avec la diffusion laser.Dans le régime filamentaire considéré, nous montrons que le flux de gaz et la fréquence de la tension joue des rôles prépondérants sur le dépôt des couches minces nanocomposites. Cette étude a permis de mettre en évidence qu’une simple fréquence n’est pas suffisante pour déposer la couche mince nanocomposite. Cependant l’utilisation d’une double fréquence semble être la meilleure approche pour séparer le transport des nanoparticules de celui de la croissance de la matrice. / Development of an atmospheric pressure process presents a major concern in the deposition of nanocomposites thin films. Among these processes, Dielectrics Barrier Discharges takes advantages to be green processes without gas effluent, which can be easily integrate in an industrial line production. The chosen approach for the nanocomposite thin film deposition is based on the injection of an aerosol of a colloidal suspension in the DBD. Semi-conductive TiO2 nanoparticles are chosen and put in suspension in a polymerizable alcohol as isopropanol. The objective of the present work is to control the transport of the nanoparticles as well as the matrix growth in the DBD in order to realize the nanocomposites thin film Different methods of the aerosol formation and filtration are evaluated, as well as the carrier gas (Ar, N2). In each case considered, the discharge works in filamentary. Estimating values of the different forces acting on the nanoparticles in a DBD comforted by a numerical model allowed to guide the experimentations. Thanks to the parameter which generated the plasma, it is possible to influence the nanoparticles deposition and the matrix growth. Depositions are ex situ analyzed by scanning electron microscopy, Infra-red, Raman, and X-ray spectroscopy and in situ by laser scattering. In the filamentary regime considered, we show that the gas flow rate and the frequency of the voltage play a dominant role on the deposition of nanocomposites thin films. This study allowed to highlight that a simple frequency is not enough to deposit the nanocomposite thin film. However, the use of a double frequencies seems to be the best way to separate the nanoparticles transport to the surface from that of the matrix growth.

Ce mémoire vise à montrer l’intérêt de nanoparticules (NPs) de TiO2 comme plateforme pour immobiliser dans un environnement proche des complexes de coordination pouvant interagir par transfert d’électron photoinduit. Nous nous sommes intéressés à l’étude de nanomatériaux hybrides associant le complexe [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) comme photosensibilisateur aux complexes [Cr(ttpy)2]3+ ou [Mn(ttpy)(CO)3Br] (ttpy = 4'-(p-tolyl)-2,2':6',2''-terpyridine) comme accepteurs d'électrons. Pour immobiliser les différents complexes à la surface du TiO2, une fonction acide phosphonique a été introduite sur une des bipyridines du centre [Ru(bpy)3]2+ et sur la terpyridine des complexes [Cr(ttpy)2]3+. L’étude des processus de transferts de charges photo-induits sous irradiation en lumière visible sur le colloïde TiO2/RuII montre que l'état à charges séparées (e-)TiO2/ RuIII possède une longue durée de vie, ce qui rend possible l'utilisation des charges dans des réactions successives d’oxydation ou de réduction. Notamment l’irradiation du colloïde TiO2/RuII en présence de [Cr(ttpy)2]3+ et de triéthanolamine (TEOA) comme donneur d'électron sacrificiel permet la réduction à deux électrons du [Cr(ttpy)2]3+. Par la suite, le complexe [Cr(ttpy)2]3+ est immobilisé sur les NPs de TiO2/RuII pour former un assemblage RuII/TiO2/CrIII au sein duquel les processus de transfert d'électrons photo-induits sont étudiés. De manière à proposer un système pour la réduction photocatalytique du CO2, le complexe [Mn(ttpy)(CO)3Br] a été co-immobilisé avec le [Ru(bpy)3]2+ suivant une approche de chimie sur surface pour former le colloïde RuII/TiO2/MnI. Ce système présente une excellente sélectivité vis-à-vis du HCOOH comme seul produit de la photoréduction du CO2 en présence de 1-benzyl-1,4-dihydronicotinamide (BNAH) comme donneur d'électron sacrificiel. Un système hybride associant le [Ru(bpy)3]2+ portant des fonctions pyrroles et immobilisé sur TiO2 a également été synthétisé et étudié. Sous irradiation lumineuse, le transfert de charges (e-)TiO2/[Ru-pyr]3+ permet d’induire la polymérisation du pyrrole. Le nanocomposite TiO2/poly(Ru-pyr) obtenu et déposé sur une électrode génère, en présence de TEOA, un photocourant anodique stable de plus de 10 μA.cm-2. L’ensemble des résultats montre que les NPs de TiO2 peuvent être un moyen d’assembler des complexes dans un environnement proche en limitant les interactions à l’état fondamental, mais permettant des transferts d’électrons photoinduits entre eux. Suivant les potentiels redox des différents composants, les transferts d’électron ont lieu soit via la nanoparticule soit en surface de celle-ci. / This thesis aims to investigate the possibility of using TiO2 nanoparticles (NPs) as a platform to immobilize proximal coordination complexes that can interact with each other by photoinduced electron transfer. We have studied hybrid nanomaterials combining [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) as a photosensitizer and [Cr(ttpy)2]3+ or [Mn(ttpy)(CO)3Br (ttpy = 4'-(p-tolyl)-2,2':6',2''-terpyridine) as electron acceptors. To immobilize the various complexes on the surface of TiO2, a phosphonic acid functional group was introduced on one of the bipyridines of the [Ru(bpy)3]2+ center and on the terpyridines of the [Cr(ttpy)2]3+ complex. Under visible light, the TiO2/RuII colloid undergoes a photo-induced charge transfer process leading to a long-lived charge separation state (e )TiO2/RuIII, which makes it possible to be engaged in successive oxidation or reduction reactions. In particular, the visible irradiation of the TiO2/RuII colloid in the presence of [Cr(ttpy)2]3+ and triethanolamine (TEOA) as a sacrificial electron donor allows the two-electron reduction of [Cr(ttpy)2]3+. Subsequently, the [Cr(ttpy)2]3+ complex has been immobilized on the TiO2/RuII NPs to form a RuII/TiO2/CrIII assembly in which the photoinduced electron transfer processes were investigated. In order to propose a system for the photocatalytic reduction of CO2, the [Mn(ttpy)(CO)3Br] and [Ru(bpy)3]2+ complexes were co-immobilized on TiO2 NPs following a chemistry on surface approach to form a RuII/TiO2/MnI triad. Under irradiation at 470 nm, this system exhibits excellent selectivity towards HCOOH as the only product of CO2 photoreduction in DMF/TEOA solvent mixture, in the presence of 1-benzyl-1,4-dihydronicotinamide (BNAH) as a sacrificial electron donor. Another hybrid system linking a [Ru(bpy)3]2+ unit to two pyrrole functions and being immobilized on TiO2 has also been synthesized and studied. Under visible light, the transient (e-)TiO2/[Ru-pyr]3+ species induce the polymerization of pyrrole to form a TiO2/poly(Ru-pyr) nanocomposite. The nanocomposite deposited on an electrode generates, in the presence of TEOA, a stable anodic photocurrent of more than 10 μA.cm-2. All the results show that TiO2 NPs can be used to associate different complexes in a close environment by limiting the interactions in the ground state but allow photoinduced electron transfer processes between them. Depending on the redox potentials of the different components, the electron transfer takes place either through the semiconducting NPs or on the surface.

Over the past few decades, inorganic nanostructured materials have elicited a lot of interest due to their high surface-to-volume ratio and many size dependent properties which stem from their nanoscale dimensions. Owing to these distinct properties, they have found applications in widespread fields like catalysis, energy storage, electronics, and biotechnology. In the field of biotechnology, nanotubes and mesoporous materials are attractive vehicles for drug delivery because of their hollow and porous structures and facile surface functionalization. Their inner void can take up large amounts of drug as well as act as gates for the controlled release of drug. These hollow structures can also be used for confining biomolecules like proteins and peptides. The study on protein conformation in biocompatible materials is very important in materials sciences for the development of new and efficient biomaterials(sensors, drug delivery systems or planted devices). Titania(TiO2)has been widely explored for applications in photovoltaic cells, batteries, desalination, sensing, and photocatalysis, to name only a few. The work presented in this thesis focuses on titania based nanostructures for drug delivery and protein confinement. First part of the work focusses on synthesis and characterization of Fe-doped TiO2 nanotubes. Fe-doped TiO2 nanotubes were demonstrated as controlled drug delivery agents. In vitro cytotoxic effects of Fe-doped titania nanotubes were assessed by MTT assay by exposing Hela cell line to the nanotubes. Second part of the work focusses on synthesis and characterization of TiO2 nanotubes by two synthesis procedures, namely hydrothermal and sol-gel template synthesis. Myoglobin, a model globin protein was encapsulated in hydrothermally synthesized TiO 2 nanotubes(diameter 5 nm) and sol-gel template synthesized TiO2 nanotubes(diameter 200 nm). Effect of encapsulating myoglobin these nanotubes was studied. The electrochemical activity and structure of myoglobin were studied by cyclic voltammetry and circular dichroism respectively. Direct electron transfer was found to be enhanced upon confinement in 200 nm diameter nanotubes. No such enhancement was observed upon encapsulation in hydrothermally synthesized nanotubes. In addition to this, the thermal stability of myoglobin was found to be enhanced upon confinement inside 200 nm diameter TiO 2 nanotubes.

The present thesis is focused on the synthesis and environmental applications of polyaniline and its nanocomposites. It is organized in six chapters and brief discussions of the contents of the individual chapters are given below. Chapter 1 reviews two important water purification methods: adsorption and photocatalysis, which are widely discussed in literature. A general introduction to conducting polymers has been given and their photocatalytic activity has been described. Chapter 2 reports the application of polyaniline emeraldine salt for the removal of anionic dyes from aqueous solutions by adsorption. A possible mechanism for the anionic dye adsorption by PANI emeraldine salt has been proposed. The electrostatic interaction between the positively charged PANI backbone and dye anions is responsible for significant dye adsorption. The kinetic parameters for the adsorption of anionic dyes on PANI have also been determined. In Chapter 3, we investigate the adsorption and desorption of anionic dyes from aqueous solution by PANI doped with different protonic acids. PANI with three dopants, namely p-toluene sulfonic acid (PTSA), camphor sulfonic acid (CSA) and dodecyl benzene sulfonic acid (DBSA) were used to adsorb various dyes. The adsorbed dyes were desorbed from the polymer by using a basic aqueous solution. It was found that the adsorption of dye is dependent on the size and nature of the dopant acids. The influence of different dopants on the adsorption and desorption kinetic parameters was also examined. In chapter 4, the inherent property of PANI to adsorb dyes has been explored for the detection of dyes by electrochemical method. The changes in the CV of PANI film coated on Pt electrodes on addition of dye have been employed for detection of dye in aqueous solution. Furthermore, PANI coated stainless steel (SS) electrodes show a change in current intensity of Fe2+/Fe3+ redox peaks due to addition of dye in the electrolyte solution. Chapter 5 describes the synthesis and characterization of polyaniline-grafted-chitosan (CPANI) with different grafting ratios. The mechanical properties and the crystallinity of CPANI were investigated by means of nanoindentation and X-ray diffraction experiments, respectively. CPANI has been further self-assembled into multilayer thin film via versatile and simple layer-by-layer (LbL) approach. Negatively charged hyaluronic acid (HUA) was used as complementary polyelectrolyte for the self-assembly. LbL growth of the multilayer thin films has been monitored with UV-vis spectral analysis as well as by AFM. The formation of thin film has been further characterized by SEM. The pH responsive behavior of CPANI/HUA multilayer thin film has been investigated. Reusability of this thin film has been investigated by repeating the pH responsive experiments for 10 cycles. Chapter 6 is focused on the preparation of nanocomposite thin films of CPANI/PSS/TiO2 via LbL approach. LbL growth of this self-assembly was monitored by UV-vis spectral analysis and porous nature was observed from SEM images. Poly (styrene sulfonate) (PSS) was used as bridging layer between TiO2 nanoparticles and CPANI for the multilayer self-assembly. Incorporation of CPANI within this LbL self-assembly enhanced the dye degradation ability of the thin film by increasing the availability of dye molecules around the TiO2 nanoparticles. Furthermore, CPANI may act as a sensitizer to enhance the photocatalytic activity of TiO2. The effects of surface area of the multilayer thin film and amount of catalysts (TiO2 nanoparticles) incorporated in the self-assembly were described based on the kinetics of the dye degradation reactions. The same multilayer thin film can be efficiently used for dye degradation several times. The work presented in this thesis utilizes unique dye adsorption properties of PANI and its copolymers. The change in conductivity of PANI after dye adsorption and the electrochemical dye detection in aqueous medium promise the potential of PANI as a dye sensing material in waste water at very low concentration. The nanocomposites of CPANI/PSS/TiO2 present a novel material for photocatalysis.