Photochemistry and picosecond absorption spectra of aqueous suspensions of a polycrystalline titanium dioxide optically transparent in the visible spectrum

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 1993-10, Vol.75 (1), p.67-75
• Main Authors: Lepore, Giuseppe P., Langford, Cooper H., Víchová, Jana, Vlček, Antonín
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics)
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/1010-6030(93)80161-2

Optically transparent suspensions of (Degussa P25) titanium dioxide which mimic well the photochemical and photophysical properties of the bulk material were prepared by sequential centrifugation. Quantum yields of photocatalyzed oxidation of I − and of propanal were measured under monochromatic 313 nm irradiation and found to be very similar to those estimated for concentrated P25 slurries but higher than those measured in colloidal TiO 2 solutions. A unit limiting quantum yield for propanal photooxidation suggests very efficient utilization of photogenerated holes. Time-resolved absorption spectra were measured in the 50 ps-10 ns time interval following excitation by a 30 ps, 355 nm laser pulse and found to be definitely different from picosecond spectra observed earlier for TiO 2 colloids. It is proposed that the observed transient signal may arise from a photogenerated hole that undergoes thermalization and surface-trapping with a lifetime of approximately 1 ns.