Degree of aggregation of indocyanine green in aqueous solutions determined by Mie scattering

Abstract

Indocyanine green in water and aqueous NaCl solutions forms large J-aggregates. The degree of aggregation is estimated by Rayleigh scattering and Mie scattering analysis. The refractive index of the aggregates responsible for scattering is deduced from an aggregate absorption cross-section spectrum using the Kramers-Kronig relations. The average degree of aggregation for indocyanine green in water is found to be of the order of 10(7) while it rises to 10(9) for indocyanine green in 0.01 molar aqueous NaCl solution. (C) 1997 Elsevier Science B.V