INTERLAYER ENERGY-TRANSFER BETWEEN CHROMOPHORIC CARBAZOLE AND OXACYANINE IN LANGMUIR-BLODGETT-FILMS - SITE SELECTIVITY OF TRAPPING

Interlayer excitation energy transfer from chromophoric carbazole to oxacyanine has been examined in Langmuir-Blodgett (LB) films by means of fluorescence spectroscopy. Picosecond time-resolved fluorescence spectra in these LB films show that the fluorescence spectra of oxacyanine, following energy transfer from carbazole, is almost the same in the time regions 0-1 ns and 0-2 ns, respectively, at concentrations of 30 mol.% and 10 mol.% of oxacyanine mixed with a mixture of arachidic acid and methyl arachidate. However, the spectra of oxacyanine obtained by direct photo-excitation change markedly in times of less than 100 ps at both concentrations. As a result, steady state fluorescence spectra of oxacyanine in LB films, following interlayer energy transfer from carbazole, are different from the spectra obtained by direct excitation. These results indicate that the excitation energy transfer from carbazole to oxacyanine shows a site selectivity and that the excitation energy can be confined by a selective site for a much longer time than expected for direct excitation, by utilizing interlayer energy transfer.