Titanium dioxide colloid with a size of particles between 20 - 40 nm was prepared. Subsequently, three substances were syntetized - methylen bis(phosphonic) acid H4L1 , 4-phosphono-butyric acid H3L2 and 4-hydroxy-4,4-diphosphono-butyric acid H5L3 . Surface of the colloidal nanoparticles was modified using these substances (H4L1 , H3L2 and H5L3 ). Then stability of these systems was studied using acid-base titration and addition of calcium ions. Keywords: TiO2, nanoparticles, surface modification

Activated Carbon (AC) is an amorphous carbon-based material characterized with a large surface area (~ 1,000 m2/g) and consists primarily of graphitic (sp2 hybrid) layers. Its amphoteric chemical property results because of the chemical treatment of the surface of AC with oxidizing agents, reducing agents, and grafting agents. β-cyclodextrin (β-CD) is a very interesting carbohydrate oligomer that provides very strong binding ability for small organic guest molecules in its inner cavity (6.0 ~ 6.5 Å) by van der Waals interactions and hydrogen bond formation between the guest molecules and the host. <p>Surface modification of AC with β-CD was synthesized by chemical methods: oxidation with HNO3, reduction with LiAlH4, and grafting β-CD onto the surface of AC via organic linkers such as glutaraldehyde and 1,4-phenylene diisocyanate. This surface grafted AC with β-CD, then, was evaluated for its surface area and sorption performance by using a solution dye sorption method using dye adsorbates. <p>Surface functional groups produced from oxidation (carboxylic acid, lactone, quinine, phenol, and nitro groups), reduction (alcohol and amine groups), and grafting (imine, hemiacetal, and urethane bonds) methods including microscopy of untreated, surface modified, and grafted ACs were characterized by various surface characterization methods: Diffuse Reflectance Infra-red Fourier Transform Spectroscopy (DRIFTS), Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA), Differential thermogravimetry (DTG), Matrix Assisted Laser Desorption Ionization Time of Flight mass spectrometry (MALDI TOF MS), and Electron spin resonance (ESR) spectroscopy. A chemical method, the Boehm method, was used for identifying surface bound acidic and basic functional groups. Nitrogen porosimetry was used to analyze the surface area and pore structure characteristics of AC, surface modified ACs, and grafted ACs. <p>p-nitrophenol (PNP) and methylene blue (MB) were used as adsorbates for the dye sorption method. PNP and MB were used to measure the sorption performance of grafted ACs at equilibrium using UV-vis spectrophotometry in aqueous solution. Sorption capacity (Qe), surface area (m2/g), and binding affinity characteristics [KF (L/g), KL (g/mol), and KBET (L/g)] were determined at equilibrium conditions using fundamental sorption models such as Langmuir, Freundlich, and BET isotherms. The sorption performance of grafted ACs and granular AC were different according to the difference in surface area and pore structure characteristics of each material.

Activated Carbon (AC) is an amorphous carbon-based material characterized with a large surface area (~ 1,000 m2/g) and consists primarily of graphitic (sp2 hybrid) layers. Its amphoteric chemical property results because of the chemical treatment of the surface of AC with oxidizing agents, reducing agents, and grafting agents. β-cyclodextrin (β-CD) is a very interesting carbohydrate oligomer that provides very strong binding ability for small organic guest molecules in its inner cavity (6.0 ~ 6.5 Å) by van der Waals interactions and hydrogen bond formation between the guest molecules and the host. <p>Surface modification of AC with β-CD was synthesized by chemical methods: oxidation with HNO3, reduction with LiAlH4, and grafting β-CD onto the surface of AC via organic linkers such as glutaraldehyde and 1,4-phenylene diisocyanate. This surface grafted AC with β-CD, then, was evaluated for its surface area and sorption performance by using a solution dye sorption method using dye adsorbates. <p>Surface functional groups produced from oxidation (carboxylic acid, lactone, quinine, phenol, and nitro groups), reduction (alcohol and amine groups), and grafting (imine, hemiacetal, and urethane bonds) methods including microscopy of untreated, surface modified, and grafted ACs were characterized by various surface characterization methods: Diffuse Reflectance Infra-red Fourier Transform Spectroscopy (DRIFTS), Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA), Differential thermogravimetry (DTG), Matrix Assisted Laser Desorption Ionization Time of Flight mass spectrometry (MALDI TOF MS), and Electron spin resonance (ESR) spectroscopy. A chemical method, the Boehm method, was used for identifying surface bound acidic and basic functional groups. Nitrogen porosimetry was used to analyze the surface area and pore structure characteristics of AC, surface modified ACs, and grafted ACs. <p>p-nitrophenol (PNP) and methylene blue (MB) were used as adsorbates for the dye sorption method. PNP and MB were used to measure the sorption performance of grafted ACs at equilibrium using UV-vis spectrophotometry in aqueous solution. Sorption capacity (Qe), surface area (m2/g), and binding affinity characteristics [KF (L/g), KL (g/mol), and KBET (L/g)] were determined at equilibrium conditions using fundamental sorption models such as Langmuir, Freundlich, and BET isotherms. The sorption performance of grafted ACs and granular AC were different according to the difference in surface area and pore structure characteristics of each material.

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A variety of synthetic bone graft materials such as the polymer poly(lactic-co-glycolic acid) (PLGA) have been investigated as alternatives to current tissue based bone graft materials. In this study, efforts have been made to improve the tissue-PLGA interface by immobilizing bone morphogenetic protein-2 (BMP-2) in an oriented manner on scaffolds using covalently immobilized heparin. The results demonstrated a four-fold increase in covalently immobilized heparin compared to non-specific heparin attachment. Furthermore, the scaffolds with covalently attached heparin retained approximately three-fold more BMP-2 than did either scaffolds with no heparin attached or scaffolds with non-specific heparin attachment. The activity of scaffolds with BMP-2 immobilized in various manners was examined using an alkaline phosphatase assay on C3H10T1/2-seeded scaffolds. These results indicated approximately twice the amount of activity with scaffolds that had BMP-2 immobilized with covalently attached heparin than on scaffolds with adsorption of BMP-2 and a three-fold increase in activity when compared to scaffolds that had non-specific heparin attachment as the mechanism for BMP-2 immobilization. These results demonstrated that PLGA with covalently linked heparin has potential to immobilize BMP-2 in a specific orientation that is favorable for cell-receptor binding, leading to the more efficient use of the bone-growth factor.

Surface-induced osseointegration and antibacterial capability are very important criteria for the clinical success of titanium implants. To enhance these two criteria, an architectural hybrid system is constructed onto Ti-6Al-4V with a rough surface. First, thermal oxidation (TO), treatment with hydrogen peroxide (H2O2) and a mix of TO and H2O2 (Mixed) are used to modify the surface topography and chemistry of Ti-6Al-4V disks. Surface characterizations by the use of microscopes and spectroscopes indicate that TO can induce more favorable topography, roughness, wettability and hydroxyl group concentration on Ti-6Al-4V surfaces. Therefore, an alginate/chitosan LBL film that incorporates antibacterial nano-silver is bridged onto thermally oxidized Ti-6Al-4V alloy by mussel-inspired dopamine. The microscopies and spectrometers confirm that the hybrid system is successfully fabricated onto the Ti-6Al-4V surface while the sub-micron topography induced by TO is maintained. Bone marrow stem cell (BMSC) adhesion, proliferation and differentiation are up-regulated by the synergy of sub-micron surface produced by TO and alginate/chitosan LBL film. The incorporation of nano-silver into the hybrid system is demonstrated to inhibit the growth of Escherichia coli and Staphylococcus aureus, but not jeopardize the enhanced BMSC activities. Taken together, this thesis presents a promising strategy to fabricate novel Ti-6Al-4V implants with enhanced osseointegration and antibacterial capability.

Polymer surfaces were modified by exposure to a silent discharge plasma, by exposure to UV radiation and by chemical functionalisation. Additionally, the silent discharge treatment of alkali halide disks was investigated. Employing XPS and IR, the silent discharge treatment of poly (phenylmethylsilane) and poly (cyclohexylmethylsilane) thin films was found to result in the formation of a carbonaceous SiO(_x) layer. Oxidation occurred faster and to a larger degree in the case of the aromatic polysilane. A XPS study of the UV irradiation of poly (phenyhnethylsilane) thin films in the presence of CCI(_4) vapour revealed the formation of a chlorinated silicon species. The analysis of aged samples showed that this initially formed product was unstable in moist air. The silent discharge treatment of alkali halide disks (KCI, KBr, KI) was studied in ambient air, as well as in dried and humidified gases (artificial air. He, N(_2), O(_2)). IR and XPS were used as analytical methods, hi most cases nitrate and halogenate were formed upon treatment in air. Depending on the reaction conditions treated KI disks sometimes showed the presence of nitrite as an additional or as the main product. In oxygen atmospheres halogenate was formed as the exclusive product. Treatments in the remaining atmospheres did not lead to product formation. The presence of water vapour in the feed gas increased the amount of product. Changes in the IR spectra of the nitrate species upon storage in a desiccator and after exposure to heat were found and monitored. Pentafluoropropionic anhydride was tested for its suitability as a vapour phase labelling reagent for hydroxyl groups on polymer surfaces. Derivatised films were analysed by XPS and IR. Using Polyvinyl alcohol as a model polymer the reaction proceeded fast and quantitative. Moreover, the cross-reaction with a number of polymers containing functionalities other than hydroxyl was studied. The reaction with nylon 6,6 was investigated m detail. The vacuum photodegradation of polyethersulfone upon irradiation with the full and a selected part of a Hg (Xe) lamp spectrum was studied. The volatile products were identified with in-situ quadrupole mass spectrometry. Monitoring the intensities of some products in subsequent irradiation phases provided evidence for a crosslinking process. In samples irradiated with the complete lamp spectrum crosslinkmg occurred faster. Additionally, the XP spectra of the corresponding samples revealed a stronger modification which became most obvious in the presence of a reduced sulfur species.

This thesis details electrical and physical measurements of pulsed laser deposition-applied thin film coatings of Alumina, Ceria, and Yttria-stabilized Zirconia (YSZ) on a LiNi0.5Mn0.3Co0.2O2 (NMC) cathode in a Lithium ion battery. Typical NMC cathodes exhibit problems such as decreased rate performance and an opportunity for increased capacity exists by raising operation voltage beyond the electrolyte stability window. Very thin (~10 nm) coatings of stable oxides provide a pathway to solve both problems. As well, the electrochemical impedance spectra of the uncoated and coated cells were measured after different numbers of cycles to reveal the property variation in the cathode. Further understanding of the mechanism of rate performance enhancement and chemical protection by thin oxide coatings will continue to improve battery capability and open up new applications. Ceria-coated Li-NMC cells show the best capacity and rate performance in battery testing. Through electrochemical impedance spectroscopy (EIS), the surface film resistance was found to remain stable or even drop slightly after repeated cycling at high voltage. CeO2 is proposed as a coating for Lithium ion battery cathodes owing to its high chemical stability and the demonstrated but not yet well understood electrical conductivity. Alumina-coated cathode shows comparable performance as that of the uncoated cell in the early stage of the test, but through the course of testing the rate capability and recoverable capacity is improved. This is possibly due to Al2O3?s well-known abilities as HF scavenger and chemically inert nature. YSZ-coated cathode performs worse than the uncoated ones in terms of capacity, rate capability, and EIS-related figures of merit. The reason for the poor performance is not yet known, and repeatability tests are under way to verify performance. High voltage cycling reveals no obvious difference in irreversible loss between the coated or uncoated cells. The reason for the lack of distinction could be the relatively small percentage of surface coating compared to the thick doctor-blade processed cathode layer.

Biomaterials used in biomedical implants, diagnostic devices, and in-situ sensors, all face the issue of biofouling. Surface modification of biomaterial surfaces with antifouling polymers can prevent non-specific adsorption of proteins and other bio-foulants onto these surfaces. Although there are many antifouling polymers to chose from, getting the polymers onto different materials is challenging as the surface modification process is dependent on the substrate’s surface chemistry. This limits the kinds of materials that are able to be modified, especially in devices made with several materials that must be modified as a single unit. Therefore, the goal of this research is to develop an effective antifouling surface modification that is compatible with different types and classes of biomaterials. A three-step modification approach was taken to form dense antifouling polymer brushes. The surfaces were first activated using oxygen plasma to increase the density of surface hydroxyl groups. Next, a silane coupling agent with an Atom Transfer Radical Polymerization (ATRP) initiator was attached to the activated surfaces. Finally, an antifouling zwitterionic monomer was polymerized on the surface using an aqueous controlled living radical polymerization technique, Surface Initiated - Activators Regenerated by Electron Transfer – Atom Transfer Radical Polymerization (SI-ARGET-ATRP). Two zwitterionic antifouling polymers, poly(carboxybetaine methacrylate) (pCBMA), and poly(sulfobetaine methacrylate) (pSBMA) were investigated. Clinically- and environmentally-relevant materials were studied and include poly(dimethylsiloxane) (PDMS), poly(ether ether ketone) (PEEK), titanium, silicon, and 3D printed stainless steel. Water contact angle (WCA) analysis showed that surfaces modified with zwitterionic polymers became more hydrophilic. WCA analysis may not be suitable for evaluating non-modified 3D printed surfaces due to their poor surface finish, and this material requires further surface topography characterization. Atomic force microscopy (AFM) and ellipsometry showed that the zwitterionic polymer layers did not necessarily have to be thick to produce their hydrophilic effect. AFM also revealed that each step of the surface modification process produced different roughness effects on all of the different surfaces. The zwitterionic layer with the smoother surface tended to better resist bovine serum albumin (BSA) adsorption. Radiolabelled BSA experiments showed reduced fouling on all 2D samples but to different degrees. The pCBMA modification was not successful in preventing BSA fouling on 3D printed 316L stainless steel. Full or partial BSA fouling may be due to the hydrolytic instability of the silane coupling agent, used to form covalent bonds between the antifouling polymers and the different surfaces, although further investigation is required to validate this hypothesis. Improving the long-term stability of silanes or research with other multi-surface compatible coupling agents that have better long-term stability in aqueous solutions should be pursued. / Thesis / Master of Applied Science (MASc)

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