Photochemistry and Radiation Chemistry of Semiconductor Colloids. 27. Preparation of Colloidal PbO2 and Various Electron-Transfer Processes

Article abstract of DOI:10.1021/j100343a015

Colloidal PbO2 (mean particle size 3.6 nm) was prepared by radiolytic oxidation of lead ions in alkaline solution, sodium hexametaphosphate acting as stabilizer.The PbO2 particles dissolved cathodically upon attack by hydroxy alkyl radicals, which is explained by electron transfer from the radicals to the colloidal particles.This transfer is accompained by a blue-shift in the absorption spectrum of PbO2 (bleaching between 300 and 600 nm) and a weak absorption at long wavelengths (600-730 nm).One colloidal particle can accept a large number of electrons to yield Pb(II) centers.Further reduction by radicals leads to Pb(0) which, however, rapidly conproportionates with Pb(IV) in the colloidal particles.Under illumination PbO2 particles are more oxidizing than in the dark.Bleaching and absorption signals were also observed in the laser flash photolysis of colloidal PbO2 solutions; the rapid decay of the signals indicated that the generated charge carriers were short-lived.