Photochemistry and spectroscopy of colloidal As2S3

As2S3 colloids have been synthesized and characterized under various conditions. Particle sizes in the range of 150 to 50 A in diameter, depending on concentration of electrolytes, were observed in these preparations. The smaller particles show pronounced quantum size effects in spite of the conclusion that in all preparations the particles are of amorphous structure. Their absorption spectra were analyzed according to current theories for absorption spectra of noncrystalline materials. Thermal, photochemical, and radiation-induced dissolution reactions of the colloid have been studied with a particular emphasis on the reactions of oxygen species. An unusual reaction of O2/sup .-/ radicals with the colloid has been observed. This reaction leads to a chain reaction and is, at least partially, responsible for the strong effect of oxygen in inducing the dissolution. It is proposed that this reaction results from a relatively high density of intraband gap traps in the collodial material