Kinetics of homogeneous nucleation of monodispersed spherical sulfur and anatase particles in water-acid systems

Homogeneous nucleation and growth of monodispersed spherulites of sulphur and hydrated titanium dioxide of anatase modification were studied by a new coherent optical method for measurement of the relative scattering coefficient based on alternative use of laser radiation of various wavelengths. A combination of the Mie theory and the method of relative scattering coefficient allows us to simultaneously obtain numerical data on the induction period t * and the time dependencies for both the diameter d(t) and the number N(t) of supercritical nuclei of the new phase at various temperatures and concentrations. This procedure allows us to reliably establish the dependencies d(t) and N(t) beginning with d ≃ 30 nm and to study the kinetics of different phenomena in colloidal systems before the beginning of particle precipitation. Under the assumption that the number of nuclei in the Na 2 S 2 O 3 + HCI + H 2 O system did not vary during their growth from the critical value d * to d ≃ 30 nm, we could estimate both the upper and lower limits for d * . The monodispersed spherulites of hydrated titanium dioxide of anatase modification were prepared by hydrolysis of titanyl sulfate in sulfuric acid solutions, and the dependence of induction period on supersaturation was studied for this process. The critical size and the surface energy of nuclei as well as the d(t) and N(t) dependencies for colloidal spherulites of TiO 2 .nH 2 O were determined.