Photochemistry and radiation chemistry of semiconductor colloids: reaction of the hydrated electron with CdS and non-linear optical effects

Abstract

The reactions of e aq − (CH 3) 2COH, and Cd + with 3 nm CdS particles were investigated by pulse radiolysis. These reactions result in the injection of an excess electron onto the surface of the colloidal particles which leads to a rather drastic bleaching of the absorption of CdS at wavelengths close to the onset of absorption. The effect is explained by an increase in the energy of the excitonic state which is formed by light absorption. The bleaching (the blue-shift of the absorption threshold) was also observed when electrons were produced by illumination of the CdS particles (non-linear absorption characteristics). Two excess electrons on a CdS particle annihilate each other, the product being a Cd atom. The annihilation process occurs in the l ms time range.