Growth of silver iodide particles investigated by light scattering

Abstract

The kinetics of growth and aggregation of polydispersed colloidal silver iodide particles was followed by static and dynamic light scattering. From the diffusion coefficients the hydrodynamic diameters and particle-size distribution were determined. Polydispersity of silver iodide colloids was confirmed by dynamic light scattering, showing bimodal and trimodal particle-size distributions. A model for the formation of the solid phase from homogeneous solution was established, considering these processes as consecutive ones. Since the particle sizes are kinetics-dependent, they were normalized under the conditions of chosen concentration of colloid and time passed from its preparation. The normalization of spatial and temporal extents showed that the particle sizes estimated by the normalized conditions within a great range of the concentration gradient and the related time of measurement, showed the same values within the precision limits; the average hydrodynamic diameter of aggregates amounted to 68.3 ± 8.0 nm. Using such treatment the low polydispersity of samples was found. Normalizing the size of polydispersed colloidal aggregates enables the polydispersed colloid to be treated as the monodispersed one under the condition defined. Furthermore, such an approach showed that colloidal aggregation can be kinetically treated as a development of a fractalized process, i.e., the process that refers to the stepwise aggregation which can be considered kinetically self-similar.