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

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 107 while it rises to 109 for indocyanine green in 0.01 molar aqueous NaCl solution.