NIRT: Semiconductor Metal Oxide Nanoparticles for Visible Light Photocatalysis

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This proposal describes a systematic study of the synthesis, characterization, and application of TiO2 nanoparticles as photocatalyst. The potential of the nanoparticles to absorb in the visible range by tailoring the surface, structural and compositional properties will be studied. Specifically, the multifold objectives of this proposal include the utilization of a unique physical vapor deposition process to obtain TiO2 nanoparticles with particle sizes ranging between 1 and 20 nm, and to reproducibly dope the nanoparticles with various dopants. These nanoparticles will be characterized for structural, chemical and optoelectronic properties. Of particular interest is the characterization of the valence band and conduction band structure by XPS, UPS, and EXAFS. We will also utilize first-principles calculations to acquire an atomistic understanding of nanoparticle properties. The theoretical models will be used to develop an understanding of the chemical and photochemical properties of pure and modified TiO2 nanoparticles. Modification involves the selective decoration of nanoparticle surfaces with noble metal particles including Ag, Au, Pt, etc. Titanium dioxide (TiO2) is used as a photocatalyst for environmental cleanup. Upon absorption of light, it helps break down toxic chemicals in air and in water. TiO2, however absorbs only UV light. It would be more useful if its absorption of the visible light can be enhanced since most of the sunlight is in the visible range. This proposal describes a systematic methodology to increase visible range absorption by changing the particle size, composition and surface chemistry.This proposal was submitted in response to the solicitation "Nanoscale Science and Engineering" (NSF 01-157). The award is jointly supported through two directorates at NSF: (i) Mathematical and Physical Sciences (Division of Materials Research in the Ceramics program) and (ii) Engineering (Division of Chemical & Transport Systems).