Formation of silver chloride nanoparticles in microemulsions by direct precipitation with the surfactant counterion

Nanoparticles of silver chloride were prepared by direct precipitation of silver ions with the surfactant counterion in the water pools of microemulsions formed by dioctyldimethylammonium chloride in an organic n-decanol/isooctane phase. This work represents a new concept to form nanoprecipitates using a single reverse micellar system. The net result is a fast reaction with less dependency on the intermicellar exchange of solubilizate. The effects of the surfactant and cosurfactant concentrations, of the mole ratio of water to surfactant, R, and of the loading of silver nitrate were evaluated. Increasing the surfactant concentration at fixed values of R and moles of silver nitrate resulted in a higher dependency on the reverse micellar exchange dynamics and increased the particle size. At high n-decanol concentration, the particle size increased due to decreasing the interaction between the nanoparticles and the stabilizing surfactant layer. Similar results were found at high values of R. Increasing the amount of silver nitrate resulted in the formation of more nuclei, and hence in the production of smaller particles. The trends in the particle size and the size distribution were followed using UV spectrophotometry and transmission electron microscope photographs.