Dimerization, J-aggregation and J-disaggregation dynamics of indocyanine green in heavy water

The dimerization constant of freshly prepared samples of indocyanine green sodium iodide in D2O is determined by an analysis of the concentration-depe ndent absorption behaviour. At high concentrations J-aggregates are formed in due time by heat treatment. The activation energy of molecule attachment to J-aggregates is determined by analysing the temperature dependence of t he rate of J-aggregate growth. The activation energy of molecule detachment from J-aggregates is deduced from measurements of the temperature-dependen t rate of J-aggregate absorption decrease after strong dilution. Compared t o indocyanine green sodium iodide in water, the dimerization constant is re duced, and the rates of J-aggregate formation at high concentration and of molecule detachment from J-aggregates at low concentration are slowed down. (C) 1998 Elsevier Science S.A. All rights reserved.