UV-vis Spectroscopy and Cyclic Voltammetry Investigations of Tubular J-Aggregates of Amphiphilic Cyanine Dyes

Abstract

The redox and light absorption properties of immobilized aggregates of the cyanine dye 3,3'-bis(2-sulfopropyl)-5,5',6,6'-tetrachloro-1,1'-dioctylbenzimidacarbocyanine (C8S3) on transparent, conductive indium tin oxide (ITO) electrodes have been studied directly using cyclic voltammetry (CV) in conjunction with UV-vis spectroscopy to elucidate unique mechanistic features of J-aggregate oxidation. C8S3 self-assembles in aqueous solution to form double-walled, tubular J-aggregates with ~13 nm diameter and lengths up to several hundred nanometers. Spectroelectrochemical measurements indicate that irreversible J-aggregate oxidation occurs primarily along the outer wall of the tubular structure as evidenced by the potential-induced irreversible bleaching of J-band absorption. Additionally, J-aggregate oxidation involves both electrochemical and chemical steps in which dimerization and subsequent dehydrogenation of the J-aggregate leads to the formation of a new dehydrogenated dimer oxidation product.