Photophysical behavior of a homologous series of amphiphilic hemicyanine dyes in thin AOT films Original Research Article

The photophysical behavior of a homologous series of amphiphilic hemicyanines, incorporated in thin films, made by dip-coating glass slides in bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT) reverse micellar solutions, has been studied by absorption spectrophotometry and computer simulation techniques. At relatively high dye concentration, a narrow band in the absorption spectrum was observed, corresponding to aggregated species. Aggregates are of the H-type, displaying a hypsochromic shift in their absorption spectra, except for the shortest chain homolog. The growth of aggregates in films has been studied in relation with the [water]/[dye] and the [surfactant]/[dye] ratios. Simulation of the aggregate formation by extended dipole interaction in spherical reverse micelles and planar bilayer structures in combination with experimental data, revealed that the films are structured in microheterogeneous assemblies analogous to the reverse micelles found in the original solutions.