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<p>Electrochemical deposition methods have been developed for the fabrication of organic － inorganic nanocomposite coatings. The methods are based on electrophoretic deposition of ceramic nanoparticles and polymers.</p> <p>EPD method has been developed for the deposition of nanostructured TiO₂ films using new dispersing agents. The stabilization and charging of the nanoparticles in suspensions was achieved using these organic molecules, which belong to catecholate and salicylate families. Anodic deposition was achieved using caffeic acid, 2,3－dihydroxybenzoic acid, 2,6－dihydroxybenzoic acid and 5－sulfosalicylic acid. Cathodic deposition was performed using 2,4 dihydroxycinnamic acid, p－coumaric acid and trans cinnamic acid. The deposition yield has been studied as a function of the additive concentration and deposition time. The deposition mechanism has been investigated. The fundamental adsorption mechanism is based on the complexation of metal ions at the surfaces of oxide nanoparticles. The method enabled the co-deposition of TiO₂ and other oxides and the formation of composite films.</p> <p>Electrophoretic deposition method has been used for the deposition of TiO₂ nanoparticles modified with organic dyes. Alizarin red, alizarin yellow, pyrocatechol violet and Aurintricarboxylic acid dyes were used for the dispersion and charging of TiO₂. The microstructures of the nanocomposite coatings were studied. The deposition yield was investigated under a variety of conditions. Obtained results could pave the way for the fabrication of dye-sensitized TiO₂ films.</p> <p>EPD method has also been developed for the fabrication of (Poly[3-(3-N,N-diethylaminopropoxy)thiophene]) PDAOT－TiO₂, (polyethylenimine) PEI－TiO₂ and PEI－hydrotalcite composite films. The microstructures of the nanocomposite coatings were studied by Scanning Electron Microscopy, Thermogravimetric Analysis, which showed the co－deposition of inorganic nanoparticles and organic polymer. Electrochemical test of the composite film has been conducted. The results showed that PEI film provided corrosion protection of the stainless steel substrates.</p> / Master of Science (MSc)

Nature uses inorganic elements for biological processes based on the useful chemistry, abundance, and availability of each metal. Transition metals are critical in the biogeochemical cycling of essential elements and the bioinorganic chemistry of organisms. Hydrolysis-prone metals such as iron and titanium are abundant on Earth but are mostly insoluble in oxic aqueous environments. Nearly every organism requires iron for survival, therefore Nature evolved to stabilize iron from hydrolysis and hydrolytic precipitation through protein and small molecule mechanisms. Like iron, titanium primarily exists as insoluble mineral oxides and is second only to iron as the most abundant transition metal in the Earth’s crust. Despite the reputation as an inert and insoluble metal, titanium can be solubilized and made bioavailable through by chemical and biological weathering. Currently there is no known native role for titanium, however it is quite bioactive. As a stronger Lewis acid, titanium can compete with iron in binding to biomolecules and proteins. It is of interest to investigate the interactions between hydrolysis-prone metals and biological systems, from whole cell organisms to proteins and small molecules. The non-pathogenic bacterium Rhodococcus ruber GIN-1 was isolated for its ability to strongly adhere to titanium dioxide (TiO2) over other metal oxides, providing an opportunity to study the interactions between whole bacterial cells and metal oxides. The GIN-1 strain incorporates Ti(IV) ions into its biomass after adherence to anatase, rutile, and a mixture of the two morphologies. Six metals were quantitated in TiO2-exposed and control (unexposed) cells by inductively coupled plasma optical emission spectroscopy. The exposure to TiO2 caused a significant uptake of titanium with concomitant loss of iron, zinc, and possibly manganese. A collaborative project with the Strongin laboratory at Temple University works to develop stable, biomaterial photocatalysts for environment remediation of toxic inorganic contaminants. Ferritins are a class of proteins that mineralizes and stores iron as a non- toxic ferrihydrite nanoparticle. These proteins can be photoactivated with ultraviolet light to release iron from its core to remediate environmental contaminants. Ferritin can be sensitized with plasmonic gold nanoparticles to extend the photoactivity of the catalyst to the visible spectrum. Work in this thesis highlights the contribution to this collaboration from the Valentine laboratory, included the expression and purification of proteins in E. coli (human H-chain ferritin, human L-chain ferritin, and bacterial DNA protection from starved cells protein), mutation of proteins to improve sensitization of catalyst, and biomineralization with iron and titanium. The trafficking of hydrolysis prone metals is vital for the survival of nearly every organism. Iron transport proteins such as transferrins are studied to understand how nature utilizes a difficult essential metal across the domains of life. Most transferrins have two homologous lobes and are believed to have evolved from a gene duplication of a monolobal transferrin. The ascidian Ciona intestinalis has genes for both a bilobal and monolobal transferrin. Nicatransferrin (nicaTf), the monolobal transferrin from C. intestinalis, is a primitive protein that may provide insight on the evolution of transferrins in higher organisms. It is advantageous to use E. coli expression systems to produce recombinant proteins, however protein misfolding and aggregation can be a concern. To improve expression of nicaTf in E. coli, codon optimization and disulfide bonded protein expression were used. Finally, siderophores are small, high affinity iron-chelating molecules secreted from lower organisms that scavenge iron in iron-limiting conditions. R. ruber GIN-1 and R. ruber DSM 43338 strains both secrete siderophores in artificial seawater media. There are several siderophores identified from Rhodococcus species, however none have been reported from any R. ruber strain. A new siderophore was isolated and preliminary work has been done to purify and characterize the molecule. Understanding the siderophore- metal ion interactions may help elucidate the mechanism of how R. ruber cells obtain titanium from the metal-oxide particles. / Chemistry

The product of interaction between Al and TiO2 at elevated temperature has a wide range of applications in refractory, structural and electronics industries (refractory tiles, tank armor, fuel cells, and microelectronic devices). This research attempts to understand the extent of interaction between Al and TiO2 when the reactant surfaces are in contact at elevated temperature and normal atmospheric pressure. The interfacial region between the reactant compounds is examined using analytical techniques; and the formation of TiAl as the interfacial compound is described. The thermodynamics of the Al – Ti – O system is explained as it relates to the particular conditions for the Al – TiO2 reaction research. Thermodynamic principles have been used to demonstrate that the formation of TiAl is favored instead of other TixAly compounds for the set of conditions outlined in this thesis. A study of the mechanism of interactions in the interfacial region can help towards being able to determine the reaction kinetics that lead to the control of microstructure and thus an improvement in the material performance. An appropriate model that describes the formation of TiAl at the interface is described in this study. The formation of TiAl at the interface is a result of the reduction reaction between TiO2 and Al. The O released during the reduction of TiO2 has been investigated and demonstrated to partly remain dissolved in TiAl at the interfacial region. Some O reacts with Al as well to form crystalline Al2O3 in the interfacial layer. / Ph. D.

Titanium dioxide (TiO2) polymer nanocomposites improve barrier properties to gas and moisture and mechanical strength as well as providing active packaging functions. However, low compatibility between hydrophilic TiO2 nanoparticles and hydrophobic polymers such as polylactic acid (PLA) causes problems due to the tendency of TiO2 nanoparticles (TiO2) to agglomerate and form large clusters. A surface modification of TiO2 with long chain fatty acid may improve the compatibility between PLA and TiO2. The goal of this study was to enhance barrier properties of oxygen and water vapor, mechanical strength and add light protecting function to PLA composites by incorporation of oleic acid modified TiO2 nanoparticles (OA_TiO2). The objectives of this study were: 1) synthesize TiO2 and modify surface of TiO2 with oleic acid, 2) investigate dispersion stability of TiO2 and OA_TiO2 in hydrophobic media, 3) incorporate TiO2 and OA_TiO2 into a PLA matrix and to characterize properties of TiO2PLA (T-PLA) and OA_TiO2 PLA nanocomposite films (OT-PLA), and 4) to determine stability of green tea infusion in T-PLA and OT-PLA packaging model systems during refrigerated storage at 4 °C under florescent lightening. TiO2 was synthesized by using a sol-gel method and the surface of TiO2 was modified by oleic acid using a one-step method. T-PLA and OT-PLA were prepared by solvent casting. TiO2 and OA_TiO2 were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, thermal analysis and dynamic light scattering. The barrier properties to oxygen and water vapor, morphology, mechanical properties, thermal stability and light absorption properties of T-PLA and OT-PLA were characterized. Dispersion of TiO2 was improved in PLA matrix by the surface modification method with oleic acid. OT-PLA had more effective improvements in the barrier properties and flexibility than T-PLA and PLA, but toughness of the films based on Young's modules of OT-PLA was lower than the T-PLA and the PLA. The OT-PLA may have a potential to be used as transparent, functional and sustainable packaging films, but limited use for complete visible and UV-light protection for photosensitized foods. / Ph. D.

This study was divided into two main parts as there were two kind of films studied. The method of deposition, pulsed laser ablation, was common to both SrBi₂Ta₂O₉ and TiO₂ films. The methods of investigations were also the same. There is an important race for the development of a practical ferroelectric memory. Among ferroelectrics that have attracted attention are the novel compounds with the Aurivillius layered structure. Ferroelectric films of SrBi₂Ta₂O₉, seem to have promising properties, low fatigue and good hysteresis. In this thesis, structure and crystal vibrations in the films were investigated with Raman scattering, infrared absorption, and x-ray diffraction. Similar studies were carried out on powders and crystals of these materials also. The results obtained prove that the films have the orthorhombic SrBi₂Ta₂O₉, structure, and the Raman and IR measurements (the first reported for SBT films) are demonstrated to provide valuable tools for optimizing the deposition process. TiO₂ is another important material in the domain of thin films. This work was undertaken to study its deposition with laser ablation. The TiO₂ films deposited are very unusual; we discovered that they contain the rare brookite phase. This is the first time that brookite has been obtained in laser-ablation-deposited films. This opens up a new area in thin film development with new potential applications. The absorption edge of brookite was measured, using natural crystals. The optical bandgap was found to be lower than the bandgaps of the rutile and anatase forms of TiO₂, in contradiction of a recent theoretical calculation. / Master of Science

Within the "forbidden" range of electron energies between the valence and conduction bands of titanium dioxide, crystal lattice irregularities lead to the formation of electron trapping sites. These sites are known as shallow trap states, where "shallow" refers to the close energy proximity of those features to the bottom of the semiconductor conduction band. For wide bandgap semiconductors like titanium dioxide, shallow electron traps are the principle route for thermal excitation of electrons into the conduction band. The studies described here employ a novel infrared spectroscopic approach to determine the energy of shallow electron traps in titanium dioxide nanoparticles. Mobile electrons within the conduction band of semiconductors are known to absorb infrared radiation. As those electrons absorb the infrared photons, transitions within the continuum of the conduction band produce a broad spectral signal across the entire mid-infrared range. A Mathematical expression based upon Fermi–Dirac statistics was derived to correlate the temperature of the particles to the population of charge carriers, as measured through the infrared absorbance. The primary variable of interest in the Fermi – Dirac expression is the energy difference between the shallow trap states and the conduction band. Fitting data sets consisting of titanium dioxide nanoparticle temperatures and their associated infrared spectra, over a defined frequency range, to the Fermi–Dirac expression is used to determine the shallow electron trap state energy. / Master of Science

Biosensors are detection devices that couple biological recognition elements to physiochemical transducers to generate quantifiable signals. Immunosensors are biosensors that use antibodies as the recognition element. The highly specific nature of antibody-antigen binding is exploited to create immunosensors that are sensitive to analytes in complex mixtures and demonstrate a rapid response. Fiber optical immunosensors based on long-period gratings have limited sensitivity at the refractive index of ordinary aqueous solutions (~1.33). A composite film was designed to raise the local refractive index of the sensor, thus increasing sensitivity. Titanium dioxide deposition raised the refractive index of the sensor to ~1.42. Bovine serum albumin was immobilized onto a dextran hydrogel and attached to the LPG element via reductive amination. The thickness of the hydrogel was estimated to be 500 nm using Environmental Scanning Electron Microscopy. The affinity film was probed by an evanescent wave to detect changes in refractive index due to the binding of anti-BSA IgG. Under these conditions, the sensor yielded a signal ratio of approximately 10-4 refractive index units per nm signal. Reproducible binding was shown over multiple exposures, with no cross reactivity for non-specific antibodies and other proteins. Anti-BSA IgG (20 µg/mL) in whole serum was recycled through the fiber holder with an accompanying peak wavelength shift that averaged 2 nm on an Optical Spectrum Analyzer with a noise level of 0.1 nm. The BSA affinity film was regenerated 50 times and showed a baseline shift of -1.3 nm. / Master of Science

Three-dimensional printing is renowned for its ability to produce complex geometries. By utilizing a pressure-driven additive manufacturing (AM) process called direct ink write (DIW) with polymer composite ink, it is possible to create parts with tailored internal microstructures that enhance surface area and particle-particle adsorption kinetics for water remediation applications. However, DIW of particle-filled systems faces challenges, particularly nozzle clogging. This paper explores the relationship between dispersion of aggregate size, torsional rheology, and the capacity to print relatively highly particle-filled systems. Various characterization methods, including torsional rheology, dynamic light scattering (DLS), and field emission scanning electron microscopy (FESEM) were employed utilizing a chitosan-graphene-titanium dioxide (CS-G-TiO2) polymer composite ink composed of TiO2 nanoparticles (1 wt.% to 25 wt.%), graphene (1 wt.%), and chitosan (5 wt.% to 9 wt.%) to evaluate the effect of ultrasonication techniques (bath vs. probe) on aggregate size. Probe-sonicated dispersions showed a more narrow monodispersed and unimodal aggregate size distribution with a primary average aggregate size of 255 nm. In contrast, bath-sonicated dispersions exhibited a moderately polydispersed, trimodal distribution with modes centered at 90 nm, 295 nm, and 5.6 μm. Non-Newtonian rheological parameters such as yield stress, complex viscosity, storage, and loss moduli were higher for the probe-sonicated CS-G-TiO2 composite ink than for the bath-sonicated CS-G-TiO2 composite ink. This increase is likely attributed to enhanced particle interactions, which allow for greater CS adsorption. These findings offer valuable insights into optimizing formulations for desired rheological properties in DIW printing. The results enable the direct ink writing of intricate geometries with high surface areas and less shape distortion, providing significant insights into processing similar multi-component slurry-based composite inks for DIW. / Master of Science / Researchers are exploring new ways to remove harmful toxins from waterbodies using 3D printing technology. By employing a specialized additive manufacturing (AM) printing process called direct ink write (DIW) and a composite ink (CS-G-TiO2) composed of chitosan (CS), graphene (G), and titanium dioxide (TiO2), it is possible to create parts with a tailored internal microstructure that allows for greater surface area and enhanced particle-particle adsorption kinetics. However, challenges remain with DIW of particle-filled systems, particularly regarding nozzle clogging. This assessment focuses on how the size of aggregates in G-TiO2 dispersions affects printability and the rheological behavior of the CS-G-TiO2 composite inks. To address these issues, different ultrasonication techniques and their effects on aggregate size were investigated, as well as the shear-thinning and yield stress behavior of the inks. These findings could be further analyzed to understand the underlying mechanism in particle aggregation and optimize the formulation for desired rheological properties for direct ink write (DIW) printing.