Nano-titania materials with special structure can possess a series of unique physical and chemical properties, such as large specific surface area, high uniformity, strong adsorptive capacity, and excellent biocompatibility, etc. They have been applied in a variety of research fields including biosensors, hydrogen sensor, highly efficient photocatalysis, fuel cells, and so on. Therefore, studies on TiO2nanomaterials and their nano-composites are of great significance as new functional materials. Moreover, in recent years, chemiresistor sensors as new kinds of micro-sensors have been widely applied for the qualitative and quantitative monitoring of volatile organic compounds on a variety of media such as air, soil and water.In the present thesis, the core researches focus on the preparation of TiO2nanotubes (NTs) and their nano-composites for developing hydrogen peroxide and glucose biosensors. Moreover, carbon black (CB)-polymer composites were utilized as sensing films to be modified on the interdigital electrodes, resulting in a new chemiresistor sensor for detection of organic gases. All of the studies are detailed as below:(1) Investigations on the self-organized growth of TiO2NTs arrays by anodic oxidization. The formation mechanism of a thin film of self organized TiO2NTs arrays was investigated in detail. TiO2NT arrays were prepared by anodic oxidization of a pure titanium sheet in electrolyte solutions containing potassium fluoride and sulfate through near-real time monitoring the anode mass, the current density, and the surface topography during the anodization. Energy dispersive x-ray spectrometry was used to monitor the surface composition change during the anodization. The titanium surface was first electrochemically oxidized to form a layer of dense oxide, under which NTs were originated. With the protection of the oxide layer, long NTs could be formed in the electrolyte solutions with relatively high pH values. The surface composition analysis indicates that the NTs were not totally oxidized to TiO2crystals. However, no other elements but Ti and O were found in the oxide film. This work reveals a way to fabricate long NTs with defined sizes.(2) Preparation of TiO2/CNT/Pt/GOx nano-composites for the development of hydrogen peroxide and glucose biosensors. Herein, highly ordered anodic titania nanotube arrays were first used as the substrate for the chemical vapor deposition (CVD) growth of carbon nanotubes (CNTs). Pt nanoparticles, with approximately3nm in diameter, were uniformly electrodeposited on the titania-supported carbon nanotubes (TiO2/CNT) so synthesized, constructing a novel TiO2/CNT/Pt electrode. It was found that the as-prepared sensor could show remarkably improved catalytic activities for the oxidation of hydrogen peroxide. Moreover, a new glucose biosensor was fabricated by modifying TiO2/CNT/Pt electrode with glucose oxidase (GOx). The results indicate that the GOx sensor could present a high sensitivity of0.2μA mM-1to glucose in the range of0.006mM tol.5mM, with a response time of less than3s and a detection limit of5.7μM at3signal/noise ratio.(3) Fabrication of a chemiresistor sensor for the analysis of volatile organic compounds (VOCs)). The chemiresistor sensor was fabricated by using carbon black (CB)-polymer composites as the sensing films which were modified on the interdigital electrodes. The main principle for the analysis of VOCs is assumed that the CB-polymer film coated on the interdigital electrodes can swell upon absorbing VOCs, resulting in an increase in the space among CB particles, and consequently an increase in electrochemical resistance. Meanwhile, the absorption of VOCs can lead to the changes in the dielectric properties of the film, which can also bring consequently the changes in the resistance and capacitance. The effects of some vital parameters like polymer film thickness, CB content, and tested frequency on the resistance and capacitance in response to VOCs were investigated. Also, the response mechanism of the VOC chemiresistor sensor to the resistance and capacitance was further discussed. |