Size-regulated gold nanoparticles fabricated by a discharge in reverse micelle solutions

A discharge was applied to reverse micelle solutions, which provided constant volume nanoreactors, to synthesize size-regulated gold nanoparticles. The molar ratio of water to surfactant, W, was varied to regulate the nanoparticle size. A pulsed power supply was used to generate the discharge in the reverse micelle solutions. The applied voltage, pulse width, and frequency were 960 V, 2 μs, and 15 kHz, respectively. The synthesized gold nanoparticles were observed by transmission electron microscopy (TEM). Surface plasmon absorption band of the gold nanoparticles was measured by ultraviolet-visible (UV-Vis) spectroscopy. TEM images showed that the average particle size varied from 3.8 to 11 nm in diameter as W was increased. Thus, the size of gold nanoparticles can be regulated by the volume of water droplets in the reverse micelle solutions. Reduction of [AuCl₄]^- ions and formation of gold nanoparticles proceeded only inside the water droplets formed by reverse micelles. These nanoreactors regulated by reverse micelles lead to the uniform growth of gold nanoparticles.