Dp. Colombo et al., FEMTOSECOND STUDY OF THE INTENSITY DEPENDENCE OF ELECTRON-HOLE DYNAMICS IN TIO2 NANOCLUSTERS, Chemical physics letters, 232(3), 1995, pp. 207-214
The dynamics of charge carrier trapping and recombination as a functio
n of pump fluence of 20 angstrom diameter TiO2 particles in aqueous so
lutions is measured. Trapping of photogenerated conduction band electr
ons occurs in less than 500 fs. The subsequent fluence-dependent decay
of trapped electrons has both a fast and a slow component. The early
time recombination results are interpreted by second-order kinetics. A
global fit to the data predicts a bulk second-order recombination rat
e constant of (1.8 +/- 0.7) x 10(-10) cm3 s-1 for trapped electrons wi
th holes. The signal at long times is attributed to electrons ejected
from the nanocluster and/or deeply trapped electrons produced via thir
d-order kinetics, consistent with an Auger process.