Aggregation Dependent Absorption Reduction of Indocyanine Green

Abstract

Indocyanine green in water and in aqueous NaCl solutions forms large J-aggregate globules. With rising aggregate size the apparent absorption cross section per molecule decreases because of specific surface reduction of the aggregates. A theoretical description of the absorption behavior is given for dense spheres, loosely packed spheres (globules), straight chains, and coiled chains. The volume fill factor of the globules is determined from the absorption reduction measurements using the degree of aggregation from Mie scattering experiments described elsewhere.