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, which 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 used photoacoustic detection. The length of the breakdown volume determined for the 2-D projection of spatially distributed plasma events generated on colloidal 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 reference particles of different diameters.