Preparation of Au colloids by polyol process using NaHCO3 as a buffering agent

Au nanoparticles were synthesized by polyol process with sodium bicarbonate (NaHCO3) as a pH-buffering agent. The introduction of NaHCO3 to polyol process made it possible to lower the reaction temperature and shorten the reduction time. In this study, the effects of the NaHCO3/Au weight ratios and the PVP concentrations on the reduction rate of AuCl4− and the particle size of Au nanoparticles were investigated. The NaHCO3/Au weight ratio was varied from 0.2 to 10. The reduction rate of AuCl4− was observed by the speeds of the color changes of the mixtures. UV–vis spectra and electron microscopic images indicated that the size of Au nanoparticles was determined by the NaHCO3/Au weight ratios and the PVP concentrations.