Effect of nanoscale dielectric environments on concentration quenching

We have studied the dependence of concentration quenching of luminescence (donor-acceptor energy transfer) on the thickness d of dye-doped polymeric films (HITC:PMMA) and found its strong inhibition at small values of d. This phenomenon is tentatively explained by a limited number of acceptors, which donors' excitation can reach in thin samples, if the film's thickness is comparable to the diffusion length of the energy transfer. The latter mechanism, along with effective reduction of the dye concentration, is responsible for an inhibition of the concentration quenching of dye molecules impregnating porous alumina membranes. The elongation of emission kinetics in thick (>3 mu m) HITC:PMMA films is cautiously attributed to the samples' crystallinity.