Technetium(VII) sulfide colloid growing observed by laser-induced photoacoustic spectroscopy

Particle growing processes were investigated for technetium(VII) sulfide (Tc2S7) colloids produced in a mixture of Na2S and TcO4- solutions by laser-induced photoacoustic spectroscopy (LPAS). Analysis of the LPAS signal intensities indicated that the particle size increased in the solution with an increase of standing time, while the number of particles remained constant. It was revealed that the size of colloid particles increased by deposition of Tc2S7 on the particle surfaces, not by coagulation of colloid particles. The formation mechanism and growing process of the colloids are discussed based on the LaMer model, which deals with nucleation processes.