Silver can dissolve from the uncovered parts of the nanoparticles under the visible light irradiation and form extremely small spherical silver clusters. The latter can be further converted into nano-scale plate-like silver powders (PSP) in the presence of polyvinylpyrrolidone (PVP). The wavelength and intensity of visible light, the irradiation time and the weight ratio of protecting polymer to reducing agent have a significant effect on the formation and shape of PSP. The conversion process was monitored by ultraviolet-visible spectroscopy (UV-Vis). The product was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray powder diffractometer (XRD). (C) 2004 Kluwer Academic Publishers.