Determination of colloid size by 2-D optical detection of laser induced plasma

A new method is presented for the size determination of aquatic colloids, w hich is based on the selective plasma generation (breakdown) on individual particles by a focused laser pulse. For this purpose. the breakdown events of particles are monitored by 2-D optical detection instead of commonly use d photoacoustic detection. The length of the breakdown volume determined fo r the 2-D projection of spatially distributed plasma events generated on co lloidal particles is proportional to the particle size. Based on this fact, an average diameter of a given colloidal dispersion can be determined. The method is calibrated by well-characterised hard-sphere polystyrene referen ce particles of different diameters. (C) 2001 Elsevier Science B.V. All rig hts reserved.