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 conc entrates on the new method of destabilizing colloid hydrosols by photo n irradiation, recognizing the possibility of thereby controlling nucl eation, growth and aggregation. Several unique advantages are obtained by photon activation of colloids, such as spatial localization, wavel ength selectivity and irradiation dose control. Using PCS, the post-ir radiation particle aggregation dynamics of a-Se colloid hydrosols was monitored. The variation of the average colloid particle diameter phi( t) and the average colloid particle number m(t) vs. time shows two zon es of distinct power law behaviour. The first zone, typical for times of t less than or equal to 10(3) s shows a monotonic growth while for longer times, saturation equilibrium values of phi and m are obtained, which also exhibit a dose-memory effect.