Metal Colloids Produced by Means of Gas Evaporation Technique. V. Colloidal Dispersion of Au Fine Particles to Hexane, Poor Dispersion Medium for Metal Sol

Abstract

Abstract Metal fine particles are not dispersed at all in pure solvents with a low dielectric constant, such as hexane. The gas flow-cold trap method combined with surfactants was found to be effective in stabilizing ultrafine metal particles in solvents with a low dielectric constant. Ultrafine gold particles can be stably dispersed in hexane in a colloidal state by this method. It was found that the stabilizability of the colloid depends on the ionic types of the surfactant. Thus, a cationic surfactant such as dimethyldioctadecylammonium chloride (DOAC) shows good dispersibility, whereas an anionic surfactant such as 1,2-bis(2-ethylhexyloxycarbonyl)ethanesulfonate (AOT) dose not. The optical spectra of colloid solutions suggest a difference in the local colloidal state between two types of surfactants. Colloidal solutions of a gold fine particle/DOAC/hexane system are so stable against heating or drying that the solvents are easily substituted.