VOLTAGE-SENSITIVE FLUORESCENCE OF AMPHIPHILIC HEMICYANINE DYES IN A BLACK LIPID-MEMBRANE OF GLYCEROL MONOOLEATE

Amphiphilic fluorescent hemicyanine dyes were adsorbed to a hemispherical bimolecular membrane of glycerol monooleate. Their excitation spectra of fluorescence were as in water, their emission spectra were as in hydrocarbon. An AC-voltage was applied across the membrane and the relative changes of the spectra of excitation and of emission were recorded. For all dyes we observed a blue-shift of excitation with positive voltage on the opposite side of staining. The effect is compared with the blue-shift expected for electrochromism. For most dyes we observed a red-shift of emission and a drop of the fluorescence intensity. These effects are compared with the red-shift and the drop of quantum yield expected for a voltage-induced solvatochromism caused by a minute displacement of the dyes in the anisotropic environment at the membrane/water interface.