ELECTRON-SPIN-RESONANCE STUDY OF RADICALS PRODUCED BY PHOTOIRRADIATION ON QUANTIZED AND BULK ZNS PARTICLES

Quantized ZnS particles were prepared and isolated from aqueous soluti on with a capping agent, thioglycerol. The absorption peak of the part icles was located at 259-260 nm, and the diameter was estimated to be 1.5-1.6 nm from X-ray diffractograms. Their excitation energy agrees w ell with that calculated with the finite depth potential well model. E SR spectra were measured for the quantized and bulk ZnS particles at 7 7 K under photoirradiation. For the quantized ZnS, only surface hole r adicals were observed, while several kinds of radicals consisting of t rapped electron, inner, and surface holes were observed for the bulk Z nS. A high activity of photocatalytic reactions for quantized semicond uctor particles may arise from a large number of radicals photoproduce d at the surface.