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Bone implants procedures involve millions of people every year worldwide. One of the main factors determining implant success is related to the ability of the prostheses to osseointegrate, i.e. to create a structural and functional connection with the living bone. Titanium and titanium alloys are widely used biomaterials for bone implants, due to their superior biocompatibility and corrosion resistance, suitable mechanical properties, and natural ability to osseointegrate. To further enhance the inherent tendency of this class of materials to bond with the host bone tissue, the surface of Ti-based implant is often modified to improve cell responses in terms of adhesion, proliferation and differentiation, all factors contributing to successful osseointegration. In particular, surface topography, both at the micro- and nanoscale, can enhance the implant-living bone interaction. Herein, a possible surface modification strategy aimed at the creation of a dual-scale topography on two different titanium alloys, Ti-6Al-4V and Ti-5Al-5Mo-5V-3Cr, is presented. Dual-scale topography was obtained by electrochemically anodizing samples manufactured by selective laser melting to combine their intrinsic microtopography with the nanotopography offered by titanium dioxide nanotubes (TNTs) generated by anodization. Characterization of the as-printed and as-anodized samples was performed to evaluate parameters of significance in the context of osseointegration. Concerning wettability, it was observed that surfaces with TNTs exhibited high hydrophilicity. The influence of the anodization process parameters on TNTs morphology was examined, and linear dependence of the nanotube diameter on the voltage was identified. Annealing of the as-anodized samples showed that anatase was produced, while preserving the nanotube integrity. Preliminary studies to assess the bioactive properties of the samples showed the spreading of bone-like cells on these substrates and the deposition of mineral during simulated body fluid testing. Therefore, both studies provided promising results to corroborate the hypothesis that dual-scale topography could potentially improve osseointegration. / Thesis / Master of Applied Science (MASc) / Bone implants are often made of titanium-based materials, which, despite their suitable properties, may not sufficiently bond with the living bone tissue. This can lead to implant loosening and failure. To produce customized implants, additive manufacturing, or 3D-printing, can be employed. However, these surfaces require substantial post-processing to produce features capable of promoting bone integration. In this work, a dual-scale surface topography to combine the advantages of both micro- and nanoscale roughness was created using electrochemical anodization on 3D-printed titanium alloy substrates. Preliminary physical, chemical, and biological characterizations suggest that the creation of titania nanotubes on the 3D-printed surfaces of Ti-6Al-4V and Ti-5Al-5Mo-5V-3Cr could improve their ability to bond with bone.

Anodization is a kind of method that can produce oxide layer in a large area and on flexible shaped metals. In some specific conditions, anodic oxide layers exhibit interesting nanopore/nanotube structures. In this work, focused ion beam patterning method is introduced to general anodization, aiming to make highly ordered anodic porous alumina and titania nanotubes. Focused ion beam guided porous anodic alumina is carried out by pre-designing hexagonal and square guiding patterns with different interpore distances on well electropolished Al foil before anodization. After anodization, the guiding interpore distance is found to affect the new pores' locations and shapes. Two important elements, electrical field and mechanical stress, are discussed for the development of the guiding pores and the generation of new pores. Based on the proposed pore growth mechanism, novel patterns, non-spherical pores, and large patterns across the grain boundaries are successfully produced. The research on focused ion beam guided anodic titania nanotubes begins with surface polishing. The influence of four polishing conditions, as-received, chemically polished, mechanically polished, and electropolished samples, are investigated. A polished smooth sample provides a desired surface for focused ion beam guided anodization. Hexagonal guiding patterns with different interpore distances are created on Ti surface. Ordered nanotube arrays are produced, and the structure of the anodized guiding pattern is identified. / Master of Science

This thesis identifies a facile and versatile technique for creating multi-scale porous titania with tunable meso-scale morphology. Three templating approaches were simultaneously utilized in achieving this; namely, soft-templating by template-free self-assembly of an aligned macroporous structure, freeze-casting for the preservation of particle dispersion found in suspension, and hard-templating by the use of cellulose nanocrystals (CNCs) as sacrificial material. A systematic study was conducted wherein three synthesis parameters (water content, alcohol solvent content, and drying method) were varied in the hydrolysis of titanium tetra-isopropoxide (TTIP) by the sol-gel method to determine their contribution to the formation of multi-scale porous titania exhibiting aligned macrochannels and mesoporosity. The optimal synthesis settings for producing multi-scale porous titania were identified as H2O/TTIP molar ratio of 30, without any isopropanol (acting as solvent), and freeze-drying after freezing at -40°C. Subsequently, CNCs were added in various quantities (0-50vol%) to the hydrolysis of TTIP using these optimized settings to achieve more direct and precise control of the final titania meso-structure. Morphological studies revealed that the final titania bodies maintained the formation of macrochannels 1-3 μm in diameter as a result of hydrolysis in excess water in the absence of an organic solvent and exhibited successful templating mutually affected by CNC addition and freeze-casting. Freeze-drying preserved particle dispersion in the colloid suspension, hindering agglomeration otherwise found after oven-drying and enhanced the CNCs' role of disrupting titania aggregation and increasing interconnectivity. Thus, meso-structured multi-scale porous titania was prepared by a combined templating strategy using template-free self-assembly, freeze-casting, and CNC hard-templating. / MS / Titanium dioxide (TiO₂) has been shown to exhibit desirable properties including physical and chemical stability and biocompatibility making it a material of great interest in a variety of fields including pigments and biomedicine. Furthermore, the material’s photocatalytic activity (i.e. ability to absorb light energy to generate usable charge) has led to its implementation in solar cells, in the production of hydrogen as an eco-friendly fuel, and in decontaminating water from organic pollutants. While TiO₂ has shown great promise in these applications, there remains a need to identify a simple strategy to synthesize TiO₂ with a tunable multi-scale porous structure with pores of different sizes and shapes to improve its performance. To this end, a facile and versatile procedure was used to prepare multi-scale porous TiO₂ with tunable morphology. In investigating the effect of water content, alcohol content and drying method on the final morphology, a multi-scale structure was achieved by synthesizing TiO₂ in the absence of an alcohol solvent and within a new moderate range of water content that had not been previously explored. Lacking an effective and easy strategy to further manipulate the multi-scale morphology, this self-assembly technique was modified by incorporating cellulose nanocrystals (CNCs) into the synthesis procedures to further tune the structure on the nanometric scale by altering the final porosity and surface area. The final TiO₂ samples exhibited multi-scale porous structures that could be manipulated by combining the self-assembly and CNC-templating techniques in an adaptable strategy to tailor the TiO₂ morphology for its various uses in photocatalysis and biomedicine.

Yes / A major barrier to the systematic improvement of biomimetic peptide-mediated strategies for the controlled growth of inorganic nanomaterials in environmentally benign conditions lies in the lack of clear conceptual connections between the sequence of the peptide and its surface binding affinity, with binding being facilitated by noncovalent interactions. Peptide conformation, both in the adsorbed and in the nonadsorbed state, is the key relationship that connects peptide-materials binding with peptide sequence. Here, we combine experimental peptide–titania binding characterization with state-of-the-art conformational sampling via molecular simulations to elucidate these structure/binding relationships for two very different titania-binding peptide sequences. The two sequences (Ti-1, QPYLFATDSLIK; Ti-2, GHTHYHAVRTQT) differ in their overall hydropathy, yet via quartz-crystal microbalance measurements and predictions from molecular simulations, we show these sequences both support very similar, strong titania-binding affinities. Our molecular simulations reveal that the two sequences exhibit profoundly different modes of surface binding, with Ti-1 acting as an entropically driven binder while Ti-2 behaves as an enthalpically driven binder. The integrated approach presented here provides a rational basis for peptide sequence engineering to achieve the in situ growth and organization of titania nanostructures in aqueous media and for the design of sequences suitable for a range of technological applications that involve the interface between titania and biomolecules. / AFOSR grant FA9550-12-1-0226; AFOSR for funding via FA9550-13-1-0040

Yes / We investigate how the presence of Ca2+ ions at the aqueous TiO2 interface influences the binding modes two experimentally-identified titania-binding peptides, Ti-1 and Ti-2, using replica exchange with solute tempering molecular dynamics simulations. We compare our findings with available experimental data and contrast our results with those obtained under NaCl solution conditions. We find that for Ti-1, Ca2+ ions enhances the adsorption of the negatively-charged Asp8 residue in this sequence to the negatively-charged surface, via Asp{Ca2+{TiO2 bridging. This appears to generate a non-local impact on the adsorption of Lys12 in Ti-1, which then pins the peptide to the surface via direct surface contact. For Ti-2, fewer residues were predicted to adsorb directly to the surface in CaCl2, compared with predictions made for NaCl solution, possibly due to competition between the other peptide residues and Ca2+ ions to adsorb to the surface. This reduction in direct surface contact gives rise to a more extensive solvent-mediated contact Ti-2. In general, the presence of Ca2+ ions resulted in a loss of conformational diversity of the surface-adsorbed conformational ensembles of these peptides, compared to counterpart data predicted for NaCl solution. Our findings provide initial insights into how peptide{TiO2 interactions might be tuned at the molecular level via modification of the salt composition of the liquid medium. / Air Office of Scientific Research, grant number FA9550-12-1- 0226.

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.

Novel sol-gel titania-poly(dimethylsiloxane) (TiO2-PDMS) and titania-silica-N-(triethoxysilylpropyl)-O-polyethylene oxide urethane (TiO2-SiO2-TESP-PEO) coatings were developed for capillary microextraction (CME) to perform on-line preconcentration and HPLC analysis of trace impurities in aqueous samples. Due to chemical inertness of titania, effective covalent binding of a suitable organic ligand to its surface is difficult via conventional surface modification methods. In this research, sol-gel chemistry was employed to chemically bind hydroxy-terminated poly(dimethylsiloxane) (PDMS) and N-(triethoxysilylpropyl)-O-polyethylene oxide urethane (TESP-PEO) to sol-gel titania and sol-gel titania-silica network, respectively. A method is presented describing in situ preparation of the titania-based sol-gel PDMS and TESP-PEO coatings and their immobilization on the inner surface of a fused-silica microextraction capillary. To perform on-line CME-HPLC, the sol-gel TiO2-PDMS or TiO2-SiO2-TESP-PEO capillarywas installed in the HPLC injection port as an external sampling loop, and a conventionalHPLC separation column was used for the liquid chromatographic separation. The sol-gel TiO2-PDMS-coated microextraction capillary was used for on-line CME-HPLC analysis of non-polar and moderately polar analytes, and the sol-gel coatings showed excellent pH (1-13), and solvent (acetonitrile and methanol) stabilities under elevated temperatures (150 C) over analogous non-sol-gel silica-based coatings. Extraction of highly polar analytes, especially from aqueous phases is not an easy task. However, the sol-gel TiO2-SiO2-TESP-PEO-coated capillaries showed excellent capability of extracting underivatized highly polar analytes from aqueous samples. This opens the possibility to employ sol-gel titania-based polar coatings for solvent-free extraction and trace analysis of target analytes in environmental and biomedical matrices. To our knowledge, this is the first research on the use of sol-gel titania (or titania-silica)-based organic-inorganic materials as a sorbent in capillary microextraction. The newly developed sol-gel titania (or titania-silica)-based organic-inorganic hybrid extraction media provides an effective solution to coupling CME with HPLC (CME-HPLC), and this can be expected to become a powerful analytical tool in environmental investigations, proteomic research, early disease diagnosis and biomarker research. Being a combination of a highly efficient solvent free sample preconcentration technique (CME) and a powerful separation method (HPLC), CME-HPLC poses to become a key analytical tool in solving complex chemical, environmental, and biomedical problems involving complex matrices.

A custom-built surface sol-gel pumping system was built for applying conformal sol-gel based coatings with controlled thicknesses on three-dimensional (3-D) nanostructured templates. The 3-D templates utilized in this work were derived from biological species, such as diatoms and butterfly wings, as well as a synthetic photoresist polymer (SU-8). Tin oxide coatings were applied on silica-based diatom frustules using the automated surface sol-gel pumping system. An organic dendrimer method was developed for amplifying hydroxyl groups on the silica-based frustule surfaces to enhance the surface sol-gel deposition process. Conformal tin oxide coatings with controlled thicknesses were obtained on the hydroxyl amplified frustule surfaces; however, little if any deposition was observed on the frustules that were not subjected to the hydroxyl amplification process. The automated surface sol-gel system was also utilized to apply multicomponent tin oxide-doped titania alkoxide chemistries on the wing scales of a blue Morpho butterfly. The alkoxide solutions reacted directly with the OH functionalities provided by the native chitin chemistry of the scales. The tin oxide served as a rutile nucleating agent which allowed the titania to completely crystallize in the high refractive index rutile titania phase with doping concentrations of tin oxide as low as 7 mol % after annealing at 450oC. The tin oxide-doped titania coatings were both nanocrystalline and nanothick and replicated the nanostructured scales with a high degree of precision. Undoped titania coatings applied on the scales required a heat treatment of 900oC to crystallize the coating in the rutile titania phase which led to adverse coarsening effects which destroyed the nanostructed features of the scales. Tin oxide-doped titania coatings were also deposited on 3-D SU-8 photonic crystal structures. The coating was crystallized in an acidic solution at 80oC which led to the formation of rutile titania inverse opal photonic crystal structures which maintained the overall structure and ordering of the template. Barium titanate and europium-doped barium titanate coatings were applied on diatom frustules using a conventional reflux/evaporation deposition process. The silica-based diatom frustules had to first be converted into magnesia/silicon composite replicas using a gas/solid displacement reaction to render the template chemically compatible with the barium titanate-based coating. Conformal titanate-based coatings were obtained on the magnesia frustule replicas possessing uncontrolled thicknesses and excess inorganic particles using the reflux/evaporation deposition process. The europium-doped barium titanate coated frustules exhibited bright red photoluminescent properties upon stimulation with an ultraviolet light source.

En Europe, l’utilisation en agriculture de grandes quantités d’engrais chimiques est la principale cause de contamination des eaux. Les concentrations en nitrate dans l’eau deviennent nuisibles pour les personnes lorsqu’elles dépassent certaines limites car elles sont la cause de méthémoglobinémie, de cancers et agissent comme perturbateurs endocriniens. L’hydrogénation catalytique hétérogène des nitrates est la méthode de dénitration la plus connue et la plus efficace due à la grande sélectivité pour les produits non toxiques, azote et eau. La photocatalyse hétérogène a émergé comme une voie très prometteuse de dénitration du fait de la possibilité d’utiliser la lumière solaire ce qui la rend commercialement compétitive et compatible avec la protection de l’environnement. Les procédés catalytiques conduisent fréquemment à l’obtention des sous-produits toxiques nitrite et ion ammonium, ainsi qu’à des oxydes d’azote gazeux NOx. Dans ce travail ont été utilisés des catalyseurs monométalliques supportés (Ag/P25, Pt/P25), leur mélange physique, et des catalyseurs bimétalliques supportés (Ag-Pt/P25 et Pd-Sn/P25). Le support oxyde de titane (TiO2) P25 est choisi pour développer un catalyseur performant pour la dénitration à la fois catalytique et photocatalytique permettant d’atteindre les normes requises par l’UE dans l’eau potable (50 mg/L NO3-, 0.5 mg/L NO2-, 0.3 mg/L NH4+). L’influence des teneurs en métaux (Ag: 0.5 – 4 pds.%; Pt: 2 et 4 pds.%), du précurseur Pt (H2PtCl6 (H)/K2PtCl6 (K)), de l’ordre d’imprégnation de Ag et Pt et de la morphologie des particules bimétalliques Pd-Sn (nanoparticules et nanobâtonnets) ont été étudiés. Les conditions expérimentales (présence/absence de H2 ; λ = 254 ou 365 nm; 4W; 45.4 mW/cm2) ont été également variées et les réactions effectuées dans un réacteur batch en PTFE sous atmosphère inerte et dans des conditions standard (catalyseur : 0.7 mg/L ; 100 mg/L NO3- ; 500 r.p.m). Contrairement à la plupart des études précédentes aucun «piégeur de trous» (expl. acides formique ou oxalique) n’a été utilisé dans nos conditions de réaction, Les analyses ont été effectuées par chromatographie ionique ou photométrie. Les propriétés physico-chimiques des catalyseurs ont été déterminées par DRX, Physisorption de N2, MET, DRUV-Vis, XPS, TPR et chimisorption de H2. Le support TiO2 P25 est inactif dans les deux procèdés non photocatalytique et photocatalyique. Le mélange physique Ag/P25+Pt/P25 conduit à une conversion (~ 56%) et sélectivité en N2 (~ 76%) plus élevées dans les conditions non photocatalytiques que chacun des homologues monométalliques, cependant NO2- and NH4+ sont obtenus. Les catalyseurs bimétalliques Ag-Pt(Pt-Ag)/P25 se montrent polyvalents étant actifs dans les procédés non-photocatalytiques et photocatalytiques. Les meilleurs résultats photocatalytiques ont été obtenus sous irradiation ultraviolette de 365 nm et en présence de H2 dû à la synergie entre les électrons générés par irradiation et l’hydrogène dissocié sut Pt. Le Pt imprégné en premier conduit à une conversion plus élevée en raison de l'amélioration de l'accessibilité de NO3- aux sites actifs Ag0 recouvrant partiellement Pt. Toutefois la sélectivité en NO2- est élevée du fait de la faible accessibilité de Pt. Pt imprégné en second décore les ensembles Ag et diminue de ce fait le nombre de sites actifs et la conversion. Le catalyseur bimétallique Pt(4)-Ag(2)/P25(K) conduit au meilleur compromis entre conversion (ca. 45%) et sélectivité en N2 (ca. 80%) dans les conditions photocatalytiques. Ceci est attribué au transfert électronique élevé entre Ag et Pt en forte interaction mis en évidence par XPS. Néanmoins, NO2- et NH4+ sont aussi obtenus. Des travaux sont encore nécessaires pour améliorer le rendement en N2. / In Europe, the agricultural use of nitrates in chemical fertilizers has been a main source of water contamination. High level of soluble nitrate in water becomes harmful pollutant for people when it exceeds the limit causing methemoglobinemia (blue baby syndrome), cancer or act as endocrine disruptor. Conventional catalytic nitrate reduction processes into N2 and H2O lead to some toxic products (NO2-, NH4+, and NOx gases). Alternatively, photocatalytic nitrate removal using solar irradiation and heterogeneous catalysts is a very promising and ecofriendly route, which has been scarcely performed. In this work monometallic supported catalysts (Ag/P25, Pt/P25), their physical mixture, and bimetallic supported catalysts (Ag-Pt(Pt-Ag)/P25 and Pd-Sn/P25) have been used. The support TiO2 P25 was chosen to develop both efficient non-photocatalytic and photocatalytic processes able to reach the EU legislation in drinking water (50 mg/L NO3-, 0.5 mg/L NO2-, 0.3 mg/L NH4+). Different compositions of catalyst including, various metal loadings (Ag: 0.5 – 4 wt%; Pt: 2 and 4 wt%), Pt precursor (H2PtCl6 (H)/K2PtCl6 (K)), Ag and Pt impregnation order, and morphology of Pd-Sn nanoparticles (spherical and nanorods) have been studied. Different experimental conditions (presence/absence of H2; λ = 254 or 365 nm; 4W; 45.4 mW/cm2) have been also evaluated and the experiments performed in a PTFE batch reactor under inert standard operational conditions (0.7 mg/L catalyst ; 100 mg/L NO3- ; 500 r.p.m). Contrary to most previous studies, any hole scavenger (e.g. formic or oxalic acid) was used in the reaction . Analyses were performed by ionic chromatography or photometry. Physico-chemical characterizations of the catalysts were done by XRD, N2-physisorption, TEM, DRUV-Vis, XPS, TPR and H2-Chemisorption in order to explain both the catalytic and photocatalytic performances.The support TiO2 P25 was inactive in both processes. The physical mixture Ag(2)/P25+Pt(4)/P25(H) showed better conversion (ca. 56 %) and N2 selectivity (ca. 76%) under non-photocatalytic conditions than each monometallic catalyst, however NO2- and NH4+ were obtained. Bimetallic Ag-Pt(Pt-Ag)/P25 catalysts exhibit a versatile behavior being active both in the non-photocatalytic and photocatalytic processes. The best photocatalytic conditions were interestingly obtained under the ultraviolet irradiation of 365 nm and in presence of hydrogen. Photocatalytic activity was enhanced in presence of H2 due to synergetic effect induced by light between photogenerated electrons and dissociation of hydrogen on Pt. Therefore, all bimetallic catalysts based on Ag and Pt were tested under these conditions. Pt impregnated first leads to higher conversion due to improved accessibility of NO3- to active Ag0 sites partially covering Pt than the opposite impregnation order where the Pt decorates Ag and reduces the number of active sites. However, high NO2- selectivity at the expense of N2 is obtained in the former case due to low Pt accessibility. The bimetallic catalyst Pt(4)-Ag(2)/P25(K) led to the most interesting conversion (ca. 45%) with the highest selectivity to N2 (ca. 80%) under photocatalytic conditions. This was assigned to the highest electronic transfer between Ag et Pt particles in close contact revealed by XPS. Nevertheless, NO2- and NH4+ are obtained too. Further studies must be done to enhance the catalytic and photocatalytic activity towards desired N2.