Corrosion processes in quantized semiconductor colloids studied by pulse radiolysis

Abstract

Electron-transfer reactions from different electron donors to PbSe colloids with diameter size less than 5 nm were studied by pulse-radiolysis techniques. Colloidal particles accept electrons from redox couples whose redox potentials are more negative than –0.8 V(vs. NHE). The optical properties of injected electrons show formation of Pb⁺ in bulk semiconductor after 1 ms and then reduction to Pb° in a second slower step ca. 10 s after electron injection. This cathodic corrosion process is also the dominant process during illumination of the colloids in the presence of hole scavengers. The photoreductive corrosion can be partially suppressed in the presence of an electron acceptor. Reduction reactions that cannot occur in bulk materials can occur in sufficiently small particles. Other quantized metal selenides show similar behaviour. The largest yield of hydrogen was produced with extremely small ZnSe colloids.