Obtaining electrostatically bound CdS - SiO₂ aggregates from electrophoretic concentrates of CdS nanoparticles

Nonaqueous electrophoresis reveals that the electrokinetic potential of CdS nanoparticles increases slightly (85 - 120 mV) along with the concentration (0-5 × 10^-3 M) of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in n-decane, while negatively charged SiO₂ particles acquire positive charge (switching from -75 up to +135 mV). The energies of interparticle interactions in CdS - CdS and CdS - SiO₂ systems are calculated from these parameters and the literature values of the Hamaker constants according to the Deryaguin - Landau - Verwey - Overbeek (DLVO) theory. It is concluded that the presence of a minimum (2.5 k_BT) on the potential dependences of the CdS-SiO₂ system indicates the formation of CdS-SiO₂ aggregates electrostatically bound by heterocoagulation at low concentrations of AOT. The luminescent properties of the obtained ultrafine CdS-SiO₂ powders depend on the CdS content.