Versatile one-pot synthesis of confeito-like Au nanoparticles and their surface-enhanced Raman scattering effect

A simple and versatile synthesis method for confeito-like Au nanoparticles was developed. Tetrachloroaurate was reduced by hydrogen peroxide in aqueous alkaline solutions in the presence of protecting agents. The reaction was accomplished within several hours at ambient temperature, and the Au nanoparticles obtained had confeito-like structures; however, their morphologies were slightly different from each other depending on the protecting agents (polyvinylpyrrolidone, pluronic surfactant, sodium dodecyl sulfate, citric acid, and hexadecyltrimethylammonium bromide) used. These nanoparticles had diameters ranging from tens to hundreds of nanometers, and they displayed red-shifted and broadened plasmon absorption bands as compered to spherical Au nanoparticles. The Au nanoparticles were accumulated on anodized alumina filters, and the surface-enhanced Raman scattering spectra of Rhodamine 6G were measured using excitation light with a wavelength of 785 nm. The enhancing effect was stronger for confeito-like structures than for polyhedral Au nanoparticles, and its order is almost the same as that of the plasmon absorption band.