In this work, the modification of conducting substrates with thin (nanometer thick) aryl films via reaction with aryldiazonium salts was investigated. Two methods were used: modification by electro-reduction of the aryldiazonium salts and modification by spontaneous reaction of aryldiazonium the salts with the surface at open circuit potential. The majority of the studies were undertaken using p-nitrobenenze diazonium salt, which gives electro-active nitrophenyl (NP) films at the surface that can be detected and characterized by cyclic voltammetry. Films prepared spontaneously on carbon and gold electrodes at open circuit potential were characterized by electrochemistry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. At both carbon and gold, spontaneous modification proceeds via electron transfer from the surface to the diazonium salt.Furthermore, on both types of surface, spontaneously prepared NP films were found to be loosely packed multilayers of less than 5 nm in thickness. The spontaneous reaction was utilized for the patterning of carbon, gold, silicon and copper surfaces by microcontact printing (μCP) with diazonium salts. The presence of spontaneously formed films upon printing was confirmed by cyclic voltammetry and AFM. The films were demonstrated to be useful for the tethering of further molecules to the surface. Patterns prepared by μCP were imaged using scanning electron microscopy (SEM) and condensation figures. The preparation of two-component systems, with different chemical functionalities attached to different, well-defined, regions of the surface, was demonstrated. The optimization of the long term activity of glucose oxidase hydrogels by covalent attachment of the hydrogels to modified carbon electrodes was investigated. Covalent attachment was demonstrated, but the resulting electrode-hydrogel surfaces did not show long-term activities superior to those for physisorbed hydrogels. It is suggested that the limiting factor for long-term hydrogel activity is not adhesion of the hydrogel to the surface, but degradation of enzymatic activity by H2O2.

This thesis described the modification of glassy carbon (GC) electrodes with aminophenyl (AP) films via in situ reduction of aminobenzene diazonium ions. The characterisation of the AP modified GC was conducted electrochemically by oxidation of the AP functionalities in acidic aqueous conditions. Ferricyanide and ruthenium hexamine redox probes were also used to investigate the blocking properties of the AP films. Before electrochemical oxidation of the AP functionalities, AP films were shown to have a nett positive charge at pH 7. After electrochemical oxidation in protic conditions, the film was either neutral or negatively charged. The preparation of diazonium cation terminated surface, which is termed 'sticky surface', by reaction of the AP modified electrodes with NaNO₂ in acidic condition, was investigated and the sticky surface was electrochemically characterised. More than one species was formed in the reaction of the AP film with NaNO₂. The reactions of sticky surface with aniline, citrate- and thiol-capped gold nanoparticles (Au-nps) were also studied. Spontaneous reaction of sticky surface with thiol-capped Au-nps had been achieved, and suggested that the reaction leads to the formation of Au–C bonds, via the loss of nitrogen. However, for the reaction of the sticky surface with citrate-capped Au-nps, it was unclear whether covalent bonding had been achieved. The reason for this was due to the possibility of an electrostatic interaction between the negatively charged citrate-capped Au-nps and the positively charged sticky surface. The stability of the sticky surface in acidic aqueous conditions was studied electrochemically and by reaction with thiol-capped Au-nps. It was found that the diazonium cations on the sticky surface are not stable over one hour in aqueous acidic conditions, or even in low temperature. The electro-catalytic activity of the thiol-capped Au-nps attached to the GC electrode via sticky surface towards the oxidation of ascorbic acid was briefly examined, and the surface was found to catalyse the oxidation reaction.

Chapter 1 provides an overview of the current literature regarding molecular level modification of conducting surfaces. The modification of carbon surfaces are discussed, with particular attention being given to the use of aryldiazonium salt compounds. Patterning of molecular layers using aryldiazonium salts and arylazides is detailed. The objectives of the project are outlined. Chapter 2 contains the general experimental methods, instrumentation, chemicals, and materials used throughout this thesis. Chapter 3 details the development of two technical methods: a heat treatment method for regenerating diazonium-modified or deactivated pyrolysed photoresist film electrodes, and a method for preparing evaporated carbon film electrodes. Although regeneration of the evaporated carbon surfaces was unsuccessful, the surfaces exhibited good electrochemical properties and are useful substrates for studying diazonium-derived films. Chapter 4 reports the covalent modification of carbon, gold, and indium tin oxide surfaces with thin porphyrin films via the electrochemical reduction of porphyrin aryldiazonium salts. Surface characterisation studies revealed that the films are stably-attached and exhibit well-defined redox and optical properties. Chapter 5 describes the preparation and patterning of organic films on carbon and silicon surfaces using arylazides combined with photolithography. Strategies were investigated to generate continuous mixed films and surfaces presenting patterns of one or two components. For all grafted surfaces, the reactivity of tether species was confirmed by coupling electroactive targets or gold nanoparticles to the tethers, followed by electrochemical analysis or surface microscopy. Chapter 6 details the modification of carbon surfaces with diazonium-derived films via aryltriazenes. Also described in this chapter is the development of microfluidics, for use with aryltriazene and aryldiazonium salt solutions, for generating parallel surface patterns. Chapter 7 concludes and answers to the challenges reported in this study. Future directions are briefly discussed.

Biodegradable polymer materials, specifically poly(lactic-co-glycolide) (PLGA) can be used as bone replacements for bone regeneration. Scaffolds can be prepared to be porous to induce bone growth into a scaffold so that it is replaced with natural tissue as the polymer degrades. However, simply using PLGA will result in formation of scar tissue rather than regeneration of natural bone. Therefore focus has turned to attaching growth factors to the PLGA molecules to elicit a specific cellular response when the implant is placed in the body. Site-directed immobilization utilizes specific groups on both the biomaterial and biomolecule so that growth factors can be oriented in a specific manner for increased cellular response. In this research, exposed carboxyl groups on a non end-capped PLGA were modified with bishydrazide spacer molecules of varying length for the eventual attachment of a biomolecule via carbodiimide chemistry. The number of hydrazide groups attached to the surface could be controlled to investigate the effects of the spacer length on protein immobilization. Both vascular endothelial growth factor (VEGF) and parathyroid hormone (PTH) were used in these studies. These two molecules have different target cells and actions, although both can play a role in bone formation. Both molecules have carbohydrate residues that were oxidized with periodate to form aldehyde moieties that were able to react with the hydrazide spacers to form a stable bond between the spacer and protein. The use of a spacer enhanced the binding accessibility of the protein as compared to randomly adsorbed protein. The shortest and longest of the spacers resulted in the highest amount of protein, with corresponding results for antibody binding. The modification of PLGA functional groups with a spacer molecule indicates that this material could be used for site-directed immobilization for any application, simply by tailoring the reaction between the biomaterial and biomolecule.

This thesis focuses on the use of surface modifiers as tools for probing and/or controlling interfaces. Surface modification of transparent conducting oxides (TCOs) with organic and organometallic modifiers can be used as a tool for mediating interfacial energetics as well as probing the kinetics of charge-transfer at the metal oxide/organic interface. The synthetic tunability of these modifiers allows us to design molecules based on various parameters, which include the nature of the binding, spacer, and terminal groups. Based on this framework, several modifiers were synthesized and used to investigate surface energy tuning as well as charge injection kinetics as a function of molecular structure. More specifically, we use XPS/UPS to examine the evolution of the chemical structure and frontier orbital levels of the TCO/organic interface as a function of the chosen surface modifier. In addition, we investigate the impact that various molecular binding groups have on mediating the kinetics of charge-transfer. In the last section of this body of work we examine the development of dielectric nanocomposite films for capacitor applications. More specifically, we examine the use of phosphonic acid modifiers to functionalize barium titanate nanoparticles in order to provide miscibility with a suitable polymer host. The effect of various modifiers on the dielectric properties not nanocomposite thin films was examined.

ABSTRACT SYNTHESIS AND CHARACTERIZATION OF SURFACE SULFONATED POLYPROPYLENE FILMS Ecevit, Safiye Tuba M.S., The Department of Polymer Science and Technology Supervisor: Leyla Aras, Prof. Dr. Co- Supervisor: Teoman Tin&ccedil / er, Prof. Dr. March 2004, 44 pages The basic reseach on the surface sulfonation of the polypropylene is very important due to the surface design for higher functionalization. For this purpose, liquid-phase sulfonation of the polypropylene surfaces at various temperatures for different time periods were performed by concentrated sulphuric acid. The physical and chemical changes formed by the effect of the sulfonation on the polypropylene surfaces were determined by contact angle measurement, mechanical analysis, UV-Vis spectrometer, differential scanning calorimeter (DSC) and scanning electron microscopy (SEM). The surface polarity and wetting properties of the samples were evaluated by contact angle measurement. It is seen that, sulfonation at low temperatures and short time periods improve these two properties of the polypropylene surfaces. Sulfonation at high temperatures and long time periods however, cause the partial breakdown of the polymer by degradation. Noticeable color change due to the degradation and carbonization of the polypropylene films sulfonated at high temperature and long time were supported by the UV-Vis spectra of the samples. Mechanical properties of sulfonated PP films were investigated. Consequently, after the sulfonation process the mechanical properties of the PP films showed a general trend of decrease with sulfonation time for a given temperature and a very fast decrease at high temperature of sulfonation. Thermal characteristics were found by differential scanning calorimeter (DSC). Thermal analysis revealed that sulfonated PP film samples displayed an additional endothermic peak. The physical effects of the sulfonation were examined by scanning electron microscopy (SEM) which showed a hexagonal hole formations due to the bursting of the air bubbles within the PP films by the effect sulfonation. The lamelae formations were also seen around these holes.

Polymeric surface modification has become an important technique over the last few decades in many areas, including medicine. It provides improved surface properties for specific applications without altering the bulk of the material. Graft copolymerisation is one technique which allows an existing polymer to covalently immobilise different monomers with or without new functional groups. Some polymeric implants are used as hard tissue substitutes for bone. However, the surface of the implant is often deficient in binding with hard tissue. Since phosphates are one of the building blocks of hydroxyapatite [Ca10(PO4)6(OH)2] or HAP, which is the main inorganic composition of bone, phosphate groups may be utilised on the surface of polymeric implants. This has the possible effect of directing bone formation at the material/tissue interface. The radiation-induced grafting of MOEP (methacryloyloxyethyl phosphate) onto ePTFE (expanded PTFE) has been carried out by a simultaneous irradiation technique in the presence of solvents. Two solvents and one mixed solvent system (in this study: methanol, MEK and a mixture of methanol, water and DCM) were used to dilute MOEP under various monomer concentrations and experiments were carried out using two different dose rates. The modified surfaces were characterised using the weight increase, XPS, FTIR-ATR, SEM, and contact angle measurement. The degree of grafting was found to be proportional to the monomer concentration but did not depend on the dose rates used. However, the grafting yield was strongly dependent upon the type of solvent used. The grafting decreased in the order: mixed solvent system » MEK > methanol. In addition, different morphologies of grafting were observed from SEM images depending on the solvent used. The samples prepared in methanol had a smooth morphology, whereas the samples obtained in MEK with a monomer concentration of greater than or equal to 10% w/v and with a mixed solvent system, had globular morphologies. A combination of in vitro tests onto three types of grafted membranes was performed (in this study: simulated body fluid (SBF), protein and cell attachment tests). Structure, composition and morphology of the calcium phosphate growth on the samples after 7 days of immersion in SBF were studied by SEM/EDX and FTIR-ATR. It was found that the growth of CaP onto the sample with low surface grafting (24%) and with a smooth morphology, was carbonated HAP. With the samples with higher grafting and globular morphologies, the inorganic minerals formed were less and had not HAP stoichiometric composition but were presumably Brushite and Octacalcium phosphate (OCP). The amount of protein adhesion in BSA solution (with 24 hours of immersion) and serum solution (with 1 hour of immersion) were determined gravimetrically and by XPS. In addition, the protein layer was investigated using FTIR-ATR. It was found that protein adsorption was highest on the surface with high grafting (100%) possibly due to the electrostatic interaction. Human osteoblast-like cell attachment and cell morphology (both after 3 hours) were examined by cellular protein synthesis assays and SEM. Cell attachment and morphology were also better on the samples with high grafting yield compared to that of low grafting, which follows the results of protein adsorption. The different in vitro tests do not agree, however, in all cases better bioactivity was found for grafted samples than that for untreated samples. This research emphasises the importance of using a series of in vitro tests to evaluate the bioactivity of materials. Although it is not clear as to what the optimum grafting conditions are at this stage, grafting of phosphate-containing monomer onto ePTFE has significantly improved the bioactivity in vitro.

This thesis investigates the application of plasma immersion ion implantation (PIII) to polymers. PIII requires that a high negative potential be applied to the surface of the material while it is immersed in a plasma. This presents a problem for insulating materials such as polymers, since the implanting ions carry charge to the surface, resulting in a charge accumulation that effectively neutralises the applied potential. This causes the plasma sheath at the surface to collapse a short time after the potential is applied. Measurements of the sheath dynamics, including the collapsing sheath, are performed using an electric probe. The results are compared to theoretical models of the plasma sheath based on the Child-Langmuir law for high voltage sheaths. The theoretical model predicts well the sheath dynamics for conductive substrates. For insulating substrates the model can account for the experimental observations if the secondary electron coefficient is modified, justified on the basis of the poly-energetic nature of the implanting ions. If a conductive film is applied to the insulator surface the problem of charge accumulation can be avoided without compromising the effectiveness of PIII. The requirement for the film is that it be conductive, yet transparent to the incident ions. Experimental results are presented which confirm the effectiveness of the method. Theoretical estimates of the surface potential show that a film of the order of 5nm thickness can effectively circumvent the charge accumulation problem. Efforts to produce and characterise such a film form the final two chapters of this thesis. The optimal thickness is determined to be near the percolation threshold, where a marked increase in conductivity occurs. Spectroscopic ellipsometry is shown to be an excellent method to determine the film thickness and percolation threshold non-invasively. Throughout this work cathodic vacuum arcs are used to deposit thin films and as a source of metal plasmas. The design and construction of a pulsed cathodic vacuum arc forms a significant part of this thesis. Investigations of the cathode spots and power supply requirements are presented.

BACKGROUND: Implant therapy has been the gold standard in the past decade when it comes to replacing partially or complete edentulous oral cavities. Patients favor this line of treatment since it does mimic their natural teeth in esthetic, function and phonetics. Unfortunately, some initially integrated implants end up diagnosed with peri-implantitis, which threatens the longevity of those implants in their respective alveolar bone. Several methods have been discussed aiming to either salvage the diseased implant or prolong the life of it in patients’ oral cavities. In this protocol we studied the efficacy of one of the suggested protocols that has been used frequently in periodontal practices aiming to decontaminate the surface of previously diseased implants. MATERIALS AND METHODS: This study looked at the efficacy through two analyses, a descriptive and a quantitative. In the descriptive, several peri-implantitis diagnosed implants were collected and distributed over 4 groups: Test, Negative Control, Positive control and compared to pristine implants. Osteoprogenitor cells were prepared in-vitro and seeded over these implants after applying the protocol on Test group only. The quantitative analysis used the EDX analysis to study the percentages of Titanium and Oxygen on contaminated implants before and after applying the protocol on. Deposits removal was tested as well to ensure efficacy of decontamination protocol. RESULTS: Descriptive analysis showed that osteoprogenitor cells had higher attachment and proliferation on implants that followed the decontamination protocol vs. other groups. Quantitative analysis showed statistically significant higher titanium percentages after decontamination. Oxygen levels were higher as well but not statistically significant. Deposits were statistically significant in removal after decontamination protocol. CONCLUSION: Decontamination of previously diseased implants following the mentioned protocol has efficiently increased the chances of re-establishment of osseointegration in previously contaminated implants.

Submitted by Charles Jourdan Alberti (charles.alberti@gmail.com) on 2018-08-23T18:57:45Z No. of bitstreams: 1 dissertacao-charles-corrigida.pdf: 2978175 bytes, checksum: bee02fe73d0c98fc3a8035c5f68d9e02 (MD5) / Approved for entry into archive by Silvana Alvarez null (silvana@ict.unesp.br) on 2018-09-03T14:51:27Z (GMT) No. of bitstreams: 1 alberti_cj_me_sjc.pdf: 2978175 bytes, checksum: bee02fe73d0c98fc3a8035c5f68d9e02 (MD5) / Made available in DSpace on 2018-09-03T14:51:27Z (GMT). No. of bitstreams: 1 alberti_cj_me_sjc.pdf: 2978175 bytes, checksum: bee02fe73d0c98fc3a8035c5f68d9e02 (MD5) Previous issue date: 2018-07-03 / A modificação da superfície dos implantes é alvo de inúmeros estudos com o intuito de desenvolver alterações microestruturais no titânio e suas ligas que possam acelerar o processo de osseointegração. O futuro da implantodontia está atualmente vinculado a estas futuras descobertas. O titânio e suas ligas são amplamente utilizadas em aplicações biomédicas devido às suas propriedades de biocompatibilidade e mecânicas. Assim, o objetivo deste trabalho é avaliar o efeito nas propriedades físico-químicas de superfície da liga de Ti6Al4V após o ataque com solução piranha nas temperaturas de 25 °C, 40 °C e 60 °C num tempo constante de 30 min. Para caracterização da superfície foram utilizadas as técnicas de microscopia eletrônica de varredura com espectroscopia de energia dispersiva de raios X, perfilometria óptica, difração de raios X e molhabilidade. Além disso foram realizados ensaios de corrosão por polarização potenciodinâmica e espectroscopia de impedância eletroquímica. Os resultados demonstraram que é possível alterar a textura, a rugosidade da superfície e a resistência à corrosão da liga com a variação da temperatura de ataque químico. O tratamento de superfície proposto não alterou a molhabilidade, que se manteve hidrofílica, nem a química da superfície, que se manteve formada principalmente por TiO2 amorfo. A rugosidade e a área da superfície aumentaram exponencialmente com o aumento da temperatura, que pode estar relacionado com o aumento da cinética de reação. Pôde-se obter uma textura tridimensional do tipo esponja com formação de nano e micropits, de acordo com a temperatura de tratamento. Houve um aumento da resistência à corrosão com o aumento da temperatura de tratamento, que pode estar associado com o aumento da espessura do óxido formado. Considerando que tais propriedades são resultados indiretos de potencial sucesso na osseointegração de um implante dentário, o tratamento de superfície da liga de Ti6Al4V com o uso de solução piranha com o controle da temperatura de ataque é um método atrativo e com grande potencial para ser comercialmente aplicado pela indústria de produção de implantes dentários. / The surface’s modification of the implants is the subject of numerous studies with the intention of developing microstructural changes in titanium and its alloys that can accelerate the osseointegration process. The future of implantology is currently linked to these future discoveries. Titanium and its alloys are widely used in biomedical applications because of their biocompatibility and mechanical properties. Thus, the objective of this work is to evaluate the effect on the surface physicochemical properties of the Ti6Al4V alloy after the piranha solution attack at temperatures of 25 °C, 40 °C and 60 °C at a constant time of 30 min. To characterize the surface were used the techniques of scanning electron microscopy with dispersive energy X-ray spectroscopy, optical profilometry, X-ray diffraction and wettability. In addition, corrosion tests were carried out by potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that it is possible to change the texture, surface roughness and corrosion resistance of the alloy with the variation of the etching temperature. The proposed surface treatment did not alter the wettability, which remained hydrophilic, nor the surface chemistry, which remained mainly amorphous TiO2. Roughness and surface area increased exponentially with increasing temperature, which may be related to the increase in reaction kinetics. It was possible to obtain a sponge-like threedimensional texture with formation of nano and micropits, according to the treatment temperature. There was an increase in corrosion resistance with increasing treatment temperature, which may be associated with the increased thickness of the oxide formed. Considering that such properties are indirect results of potential success in the osseointegration of a dental implant, the surface treatment of the Ti6Al4V alloy with the use of piranha solution with the control of the attack temperature is an attractive method and with great potential to be commercially applied by the dental implant production industry.