Laser induced photoacoustic spectroscopy applied to a study on colloid formation processes

Laser induced photoacoustic spectroscopy (LPAS) was applied to determination of the concentration and size of colloid particles in aqueous solutions. The intensity of photoacoustic signals for mono-dispersed polystyrene particles in different sizes was linearly increased with an increase of the polystyrene concentration, while the proportionality was dependent on the particle size. Furthermore, dynamic measurements of colloid-particle growing of gold sols produced by the reaction of aurate ions (AuCl4-) with sodium citrate was made by means of LPAS. The intensity of photoacoustic signals for polystyrene and gold particles was successfully calculated as a product of the number of particles and the absorption cross section per particle based on the Mie's light scattering theory. With this technique, the coagulation of Tc(IV) colloids was observed successfully. (orig.)