Synthesis of anisotropic gold nanoparticles in a water-soluble polymer

Anisotropic gold nanoparticles have been synthesized by a UV irradiation technique through the interaction of HAuCl4 and a stabilizing agent, poly (vinyl pyrrolidone) (PVP). The effect of irradiation time on the size and shape of gold nanoparticles was investigated by UV-visible spectroscopy and Transmission Electron Microscopy (TEM). The absorption spectra of all samples show a broad band with the characteristic surface plasmon resonance (SPR) peak visible at around 530 nm. The presence of an additional low intensity absorption peak at a longer wavelength suggests the presence of non-spherical nanoparticles. The TEM measurements show evidence of particle shapes such as spheres, hexagons, decahedrons and truncated triangles as the reaction proceeded from 5 min to 24 h. The variation in particle shape is probably due to the effect of the reduced gold to PVP ratio as the reaction proceeds. (C) 2008 Elsevier B.V. All rights reserved.