Facile synthesis and size control of Ag nanoparticles by a photochemical reduction at room temperature

Facile synthesis and size control of Ag nanoparticles by a photochemical reduction was demonstrated. UVvisible spectra and photographs of the synthesized solutions with and without sodium citrate at different UV exposure times showed that sodium citrate played a crucial role for the growth of Ag nanoparticles. According to UV exposure of the Ag colloidal solutions with 0.250mM sodium citrate for 0, 7, 15, 30, and 60min, the average particle sizes were 0, 2.45, 5.58, 7.03, and 11.08 nm, respectively. Ag nanoparticles exhibited great increase in sizes, from 5.71 to 36.43nm after UV exposure for 60min, as the sodium citrate concentration increased from 0.125 to 0.500mM. The photochemical reduction is hypothesized to decompose of citrate ions and result from photoelectron transfer from the neutral Ag atoms to the Ag+ ions to form Ag nanoparticles. These results suggest that the photochemical reduction method can provide Ag nanoparticles in the presence of sodium citrate at room temperature without using a reducing agent.