Silver nanoparticles were produced by laser ablation of a metal silver plate in an aqueous solution of sodium dodecyl sulfate, C 12 H 25 OSO 3 Na. The absorption spectrum of the silver nanoparticles is found to be essentially the same as that of silver nanoparticles chemically prepared in a solution. The size distribution of the nanoparticles measured by an electron microscope shifts to a smaller size with increase in the concentration of sodium dodecyl sulfate and with a decrease in the irradiation laser power. These findings are explained by a scheme that the nanoparticles are formed via rapid formation of an embryonic silver particle and a consecutive slow particle growth in competition with termination of the growth due to SDS coating on the particle.

Gold nanoparticles were produced by laser ablation of a gold metal plate in an aqueous solution of sodium dodecyl sulfate. The absorption spectrum of the gold nanoparticles was essentially same as that of gold nanoparticles chemically prepared in a solution. The size distribution of the nanoparticles thus produced was measured by an electron microscope and was found to shift to a smaller size with an increase in surfactant concentration. This behavior is explained in terms of the dynamic formation model. Dependence of the nanoparticle abundance on surfactant concentration in the solution shows that stable gold nanoparticles tend to be formed as the surfactant concentration exceeds 10 -5 M. The gold nanoparticles having diameters larger than 5 nm were pulverized into those having diameters of 1-5 nm by a 532-nm laser.

Silver nanoparticles were produced by laser ablation of a metal silver plate in aqueous solutions of surfactants, C n H2 n +1SO4Na (n = 8, 10, 12, 16). The nanoparticles thus produced were characterized by electron microscopy and UV−visible absorption spectroscopy. The abundances of the nanoparticles before and after centrifugation were measured as a function of the surfactant concentration. The concentration dependence of the abundance implies that the surfactant coverage and the charge state on the nanoparticle surface are closely related to the stability of the nanoparticles in the solutions. The nanoparticles tend to be aggregated when the coverage is less than unity, while they are very stable when the surface is covered with a double layer of the surfactant molecules.