Time-resolved photoredox reactions of colloidal CdS

Abstract

Microsecond flash photolysis leads to a hypsochromic shift in the band edge of colloidal CdS. The recovery of the absorption spectrum does not obey simple first- or second-order kinetic but results from a distribution of first-order rate constants, which in turn arise from a distribution of particle sizes. Good agreement is obtained between the kinetic data and the distribution of particle radii calculated from dynamic laser light-scattering measurements. The transient is assigned to electrons trapped on the particles and it can be used to follow directly the rate of interfacial electron transfer from CdS to methyl viologen and O₂ when cysteine is present.