SYNTHESIS OF CADMIUM-SULFIDE INSITU IN REVERSE MICELLES - INFLUENCE OF THE PREPARATION MODES ON SIZE, POLYDISPERSITY, AND PHOTOCHEMICAL-REACTIONS

We present results obtained by using reverse micelles of either sodium bis(2-ethylhexyl)sulfosuccinate (AOT) or mixed cadmium and sodium bis(2-ethylhexyl)sulfosuccinate (AOT/Cd(AOT)2) to form CdS semiconductor particles. The control of size, polydispersity, and the photochemical reactions are compared by using various mode of synthesis of CdS. Three different reverse micellar systems have been used: the cadmium ions are solubilized in AOT reverse micelles either in the presence or in the absence of a protecting polymer such as HMP (Cd(NO3)2/+/-HMP/AOT/isooctane/water reverse micelles} or associated with bis(2-ethylhexyl)sulfosuccinate (Cd(AOT)2/AOT/isooctane/water) reverse micelles. The size of the CdS particles is found to increase with the water content. The polydispersity strongly depends on the mode of CdS synthesis. At low water content, reverse micelles protect CdS semiconductors from photocorrosion. At higher water content, photocorrosion process depends on the x value, on the presence of HMP, and on the participation mode of cadmium ions (Cd(NO3)2 and Cd(AOT)2 in the synthesis. The photoelectron-transfer reactions from CdS particles to different dialkyl viologens have been studied. The variation in the yield strongly depends on the relative value of the cadmium over sulfide ions concentrations and on the presence of sulfide clusters bound to the CdS at interface. It is possible to gelify the reverse micellar system and form semiconductors in isotropic gel using the various systems described previously.