Effect of metal–dielectric substrates on chemiluminescence kinetics

Abstract

We studied chemiluminescence of rhodamine 6G (R6G) dye in a series of R6G:DNPO:PMMA films deposited onto a variety of metallic, metal–dielectric, and dielectric substrates. We found that chemiluminescence kinetics on top of Ag and Au films covered by an insulating MgF2 layer had longer decay times than those on top of purely dielectric substrates, MgF2 films on glass. We infer that Ag- and Au-based substrates with an insulating MgF2 layer on top affected the reaction rates by influencing polarization energies of reactants and surrounding molecular dipoles. At the same time, the chemiluminescence kinetics on top of Ag and Au surfaces (without an insulating MgF2 spacer) were substantially shorter than those on top of dielectric substrates, probably because of conventional chemical catalysis. The peak emission intensities on top of metallic substrates (with and without the MgF2 layer on top) were lower than those on top of purely dielectric substrates, likely due to inhibition of the energy transfer to acceptors (R6G dye molecules) known in the vicinity of metals. The further reduction of chemiluminescence intensity on top of lamellar metal–dielectric stacks could be due to preferential emission of light inside the volume of the metamaterial rather than outside.