IN-SITU MEASUREMENTS OF ION-EXCHANGE PROCESSES IN SINGLE POLYMER PARTICLES - LASER TRAPPING MICROSPECTROSCOPY AND CONFOCAL FLUORESCENCE MICROSPECTROSCOPY

Ion-exchange processes of a cationic dye (Rhodamine B; RhB) were studi ed for individual polymer particles (diameter of 16-20 mu m) by laser trapping microspectroscopy and confocal fluorescence laser microspectr oscopy, The absorbance of RhB at 565 nm adsorbed on a cation-exchange particle increased linearly with the concentration of RhB in the aqueo us phase, while it was independent of the particle diameter, Fluoresce nce intensity profile measurements of RhB along the particle diameter by confocal fluorescence microspectroscopy directly proved that ion ex change took place in the surface layer (similar to 2-mu m thickness) o f the particle in the initial stage (1 h), Diffusion of RhB in the par ticle was very slow, and ion exchange proceeded gradually to the inner volume in the order of days, The ion-exchange processes were analyzed on the basis of simulation of the time course of the concentration pr ofile of RhB in the particle, and the diffusion coefficient of RhB was determined to be (2-4) x 10(-11) cm(2) . s(-1).