Aggregation kinetics of photo-excited colloid solutions observed by dynamic photon correlation spectroscopy (PCS)

Factors such as temperature, chemical activity, ionic strength and pH changes are known to affect colloid stability. This investigation concentrates on the new method of destabilizing colloid hydrosols by photon irradiation, recognizing the possibility of thereby controlling nucleation, growth and aggregation. Several unique advantages are obtained by photon activation of colloids, such as spatial localization, wavelength selectivity and irradiation dose control. Using PCS, the post-irradiation particle aggregation dynamics of a-Se colloid hydrosols was monitored. The variation of the average colloid particle diameter (t) and the average colloid particle number m(t) vs. time shows two zones of distinct power law behaviour. The first zone, typical for times of t ≤ 103 s shows a monotonic growth while for longer times, saturation equilibrium values of φ and m are obtained, which also exhibit a dose-memory effect.