FRACTAL AGGREGATION IN AQUEOUS-SOLUTIONS OF PORPHYRINS

We have studied the aggregation of the porphyrin s-bis(N-methylpyridin ium-4-yl)-diphenyl-porphyrine (t-H2Pagg) in aqueous solutions by means of light scattering (elastic and quasielastic) and UV-visible absorpt ion measurements. Elastic and dynamic light scattering indicate that t he aggregation produces large monodisperse clusters having a fractal s tructure driven by diffusion limited aggregation (DLA). UV-visible abs orption measurements have been applied to study the corresponding kine tics, obtaining the time dependence of the monomer concentration and o f the mean cluster size. The obtained findings are in agreement with t he picture proposed by current theoretical models and molecular dynami cs (MD) simulations on DLA. (C) 1998 Elsevier Science B.V. All rights reserved.