Preparation of colloidal silver nanoparticles using benzoin as a photoinitiator

Sensitized photoreduction of Ag+ ions and subsequent formation of colloidal Ag nanoparticles occur when near-UV light is irradiated onto the ethanol solution of a mixture of benzoin (BN), AgClO4 and poly(vinylpyrrolidone). Transient species generated by α-cleavage of BN; α-hydroxybenzyl radical (α-HBR) and benzoyl radical (BR), are detected by means of nanosecond laser flash photolysis. It has been found that an apparent decay time of the absorption band of α-HBR is decreased with increasing AgClO4 concentration. In combination with comparative laser flash photolysis studies on benzaldehyde and benzyl in solutions, it has been suggested that α-HBR is capable of reducing Ag+ ions but BR is not.