Novel preparation of nanostructured titanium dioxide photocatalytic particles, films, membranes, and devices for environmental applications

Precise manipulation of matter at the nanoscale will enhance our potential to synthesize materials with tailor-designed properties and functionalities for their environmental applications. This dissertation explores the development of innovative nanotechnological procedures for the preparation of highly efficient visible light-activated nanostructured TiO2 photocatalytic particles, films, membranes, and devices for environmental applications.; Nanocrystalline TiO2 particles and immobilized films and membranes with mesoporous inorganic network were prepared via a sol-gel method modified with surfactants as pore-directing agents. Not only did we manipulate the physicochemical properties of TiO2 such as crystallographic structure, particle size, and defect structure but also tailor-design its structural properties such as surface area, pore volume, and pore size distribution. Asymmetric mesoporous multilayer TiO2 photocatalytic membranes exhibiting hierarchical changes in pore diameter and materials porosity were also fabricated. These TiO2 films and membranes inherently possessed multiple and simultaneous functions including photocatalytic decomposition of organic pollutants, inactivation of pathogenic microorganisms, physical separation of contaminants, and anti-biofouling action.; In addition, for the design of solar-driven treatment technologies, highly efficient visible light-activated TiO2 photocatalysts with mesoporous structure and narrowed band gap energy were synthesized by introducing nitrogen-containing surfactant as a pore templating material as well as a nitrogen dopant in the sol-gel method of TiO2. For the development of highly sensitive and stable electrochemical sensors to detect a neurotransmitter, catechol, sonogel carbon electrodes were modified with the nanostructured TiO2 acting as an adsorbent for catechol and a redox mediator for electron transfer.; We also elucidated the formation of nanocrystalline TiO2 particles at ambient synthesis conditions via sol-gel method employing water immiscible room temperature ionic liquid as reaction medium and modified with surfactant as pore template. Detail information on the preparative method, synthesis route and mechanism, crystallographic and structural properties, and photocatalytic activity of the nanocrystalline TiO2 particles with thermal stability was investigated.; From a scientific point of view, this study will provide new nanotechnological and materials chemistry procedures to synthesize highly efficient photocatalytic TiO2 particles, films, and membranes that can be used for the treatment and disinfection of water and wastewater under even visible light irradiation, and highly sensitive TiO2-based devices for the development of new type of sensors.