Synthesis and Characterization of Sensitizers for Surface Derivatization ofNanocrystalline Photocatalyst Film Devices

摘要

The work performed over the period from Sept. 1996-Oct. 1997 under the originalgrant no. DAJA 45-90-C-0007 from the European Research Office of the US. Army was in line with the principal objectives of the proposed investigations, i.e. the synthesis of ligands, the complexation of the ligands to appropriate metal ions, the application of the metal complexes to nanocrystalline semiconductor surfaces, the examination of the properties of such films and the use of nanocrystalline semiconductor films to accomplish the catalytic and photocatalytic decomposition of toxic chemicals, in particular warfare agents or simulants. The first line of interest was to develop efficient charge transfer sensitizers for nanocrystalline anatase films in order to render the photocatalytic action efficient in daylight. To this end, compounds containing transition metal ions complexed by ligands containing anchoring groups as well as bystander molecules were synthesized. Specifically, the synthesis of the dithiol derivative of pyrazine and the tetrathiooxalate anion were undertaken, as well as of a new ruthenium charger transfer sensitizer having a high oxidation potential (Eo=1.7V vs. NHE). Sensitization of nano-crystalline TiO2 films employing this complex was investigated and exhibited interesting wavelength dependent quantum yields for electron injection; a phenomena attributed to electron injection from vibrationally unrelaxed ( << hot >> ) sensitizer states.