Preparation of Au nano-particle dispersed water solution without surfactant for surface-enhanced Raman scattering platform
Gold nano-particle (AuNP) dispersed water solution was prepared directly from high-purity Au electrodes in hydrogen peroxide (H2O2) water solution by solution plasma (SP) processing. With 5 min SP treatment, about 0.01 wt% of AuNP dispersed water solution of about 50 mL was obtained. The average diameter of AuNP was estimated to be about 14 nm from transmission electron micrograph images. AuNPs kept dispersed state in water solution for 4 weeks without addition of any surfactant. The zeta potential of AuNP resulted in between −36 and −51 mV, and it was suggested the strong negative charge on the AuNP surface prevented AuNPs from binding each other. Vaporization of water by heating brought us the concentration increase of the AuNP dispersed water solution to be about 1 wt%, and this allowed us to make easily Au thin films as a plat form of surface-enhanced Raman scattering.