Excitation energy transfer efficiency of dipole-dipole interaction in a dye pair in polymer medium

Excitation energy transfer efficiency (eta) of dipole-dipole interaction has been studied in the dye pair 3,3'-dimethyloxacarbocyanine iodide (DMOCI) (donor) to o-(6-diethylamino-3-diethylimino-3H-xanthen-9-yl) benzoic acid (Rhodamine B, RB) (acceptor) in polyvinyl alcohol (PVA) thin films by steady-state and ps time-resolved fluorescence spectroscopy. In the presence of the acceptor the fluorescence intensity of the donor decreases, while that of the acceptor increases as a function of the added acceptor concentration. Time-resolved study of the donor at various acceptor concentrations suggest that the non-radiative energy transfer mechanism as proposed by Forster is responsible for the observed behaviour along with some modifications at very low acceptor concentrations. Modified eta values have been simulated and compared with those obtained experimentally. It is found that the value of eta increases with acceptor concentration.