The role of adsorption species in the formation of Ag nanostructures by a microwave-polyol route

Abstract

The role of adsorption species in reaction solutions has been studied in microwave-polyol synthesis of silver (Ag) nanostructures. When Ag+ ions from AgNO3 were reduced in ethylene glycol by the addition of H2[PtCl6] and poly-(vinylpyrrolidone) (PVP), a mixture of one-dimensional (1-D) nanorods and nanowires and 3-D spherical, cubic, and triangular-bipyramidal nanoparticles was obtained within three minutes. It has been previously believed that PVP acts as a surfactant and its selective adsorption on {100} facets results in pentagonal 1-D nanorods or nanowires and cubic and triangular-bipyramidal nanocrystals. We found here that these Ag products could also be formed without the addition of PVP in the presence of Cl- ions, though their yields were lower than those in the presence of PVP by a factor of ˜300. These results indicate that Cl- anions can also act as adsorption species to assist the formation of these Ag nanostructures. It is concluded that the difference in the adsorption ability of different species in solution on Ag nanostructures determines final shapes, sizes, and yields of formed Ag nanostructures.