Preparation of aqueous CdS colloids in the presence of cadmium complexonates: Effect of complexonates on the size of CdS nanoparticles

The results of a systematic study of the preparation of CdS colloids in aqueous solutions containing different Cd2+ complexonates are presented. The effects of the ratio of the reagents and the nature and concentration of various stabilizing surfactants and Cd2+ complexonates, including those of some sulfur-containing compounds, on the size of the colloidal particles have been studied. Thermodynamic calculation of the expected equilibrium size of the colloidal particles as a function of the solvent composition, taking into account the increase in the solubility of the CdS phase as the particle size decreases, has been performed. Comparison of the calculated results with the experimental data shows that the size of colloidal particles is determined to a great extent by kinetic factors of their growth rather than by thermodynamic factors. It has been established that when the size of colloidal particles is less than a critical value, their dissolution by adding strong compexing agents to the system does not result in a change in the observed mean-volume size of the particles.