SYNTHESIS OF COPPER NANOSIZE PARTICLES IN ANIONIC REVERSE MICELLES - EFFECT OF THE ADDITION OF A CATIONIC SURFACTANT ON THE SIZE OF THE CRYSTALLITES

The size of copper nanoparticles in reverse micelles can be controlled by varying the water content of anionic reverse micelles (AOT = sodiu m bis(2-ethylhexyl)sulfosuccinate). In the presence of cetyltrimethyla mmonium chloride (CTAC), depending on the concentration, the size of t he particles is strongly affected. At a low CTAC concentration ([CTAC] = 4 x 10(-4) M), an unexpectedly large increase in the size is observ ed. At the other extreme, a decrease in the size is observed at higher CTAC concentration ([CTAC] = 6.4 x 10(-3) M). The increase in the siz e at low CTAC concentration could be explained in terms of the formati on of superaggregates containing most of the cationic surfactant. At h igher CTAC concentrations, a random distribution of the positively cha rged surfactant takes place and the decrease in the size could be due to a decrease in the intermicellar attraction. Furthermore, the yield of particles drastically increases which is attributed to a change in the redox potential.