Plasmon effect on triplet-singlet energy transfer in the dye-doped Langmuir-Blodgett films

The effect of silver plasmonic nanoparticles on triplet-singlet energy transfer in the donor-acceptor pair of organic dyes was studied. Layered dye films were prepared on the surface of glass and island silver films using the Langmuir-Blodgett method. Amphiphilic analogs of Rose bengal and polymethine dye were used as donor and acceptor of energy. A polymer monolayer was deposited between monolayers of donor and acceptor molecules to exclude the competing triplet-triplet energy transfer. The spectra of delayed fluorescence and phosphorescence of donor-acceptor films and the delayed luminescence lifetime of donor in these films have been measured. It is shown that a threefold increase in the fluorescence intensity and a twofold increase in the donor phosphorescence intensity are observed on silver island films. The successful triplet-singlet energy transfer is evidenced by both the quenching of donor centers and appearance of sensitized delayed fluorescence of the acceptor with the duration close to the donor triplet lifetime. In the presence of silver nanoparticles, in addition to enhancement in the intensity of the donor emission, an increase in the efficiency of tripletsinglet energy transfer was observed. The obtained results can be used in various optical devices.