The effects of aggregation on the redox levels of cyanine dyes

摘要

The effects of aggregation on the redox thermodyanics for a series of cyanine dyes are investigated. The adsorption of the dyes on a cubic silver bromide emulsion can be controlled to selectively yield the monomer or the J-, H-, or an H-herringbone aggregate. The adsorbed monomer and aggregate dyes can be reversibly oxidized with metalcyanide redox buffere solutions. The oxidation potential of the adsorbed dye is obtained from a Nernstina plot of redox-solution potential E vs log [oxidized dye]/[dye]. The results indicate that the one-electron oxidation potential of the monomer to be lower than that of the aggregate by ca. 70 mV. The energies of the singlet excited-states of the various dye aggregates vary by 0.6eV.