Production of ultrafine gold and silver particles by means of a gas-evaporation and solvent-trap technique.

Gold and silver colloids were produced in ethanol by a gas evaporation technique combined with a solution-trap method. Both the clusters in the solution and those collected before entering the solution were examined by transmission electron microscopy. The size of colloids in ethanol was 30~100angstroms for Au and 50~ 200angstroms for Ag. In contrast, the clusters collected before the solution trap has a dimension of 10 to 60angstroms, which is smaller than those trapped in ethanol. This size increase was brought about by coalescence growth in the solution, which took place when the solution temperature was raised from dry-ice/acetone to room temperature.