RESUMEN
Anthracene tetracene-doped crystals (TA) dispersed in a thin polymer film matrix have been reported as efficient down converting systems based on Förster Resonance Energy Transfer (FRET) which occurs efficiently from donor (anthracene) to acceptor (tetracene) molecules. In this work, we demonstrate that the efficiency of this system can be further improved by a metal-enhanced FRET, which is obtained by incorporating metal nanoparticles into the polymer matrix. We report on the preparation and optical responses of polymeric transparent thin films where dodecanethiol-capped silver or gold nanoparticles are dispersed with TA in a polymethylmethacrylate (PMMA) matrix. A maximum of 11-fold and 6.5-fold enhancement was achieved with silver and gold nanoparticles, respectively. Efficiency is discussed in terms of film morphology and plasmon resonance induced effects.
RESUMEN
We analyze the infrared and Raman spectra (both experimentally and with the aid of quantum chemical calculations) of a series of polyenals which provide us with the fortunate case of a set of polyene chains with one of the end groups consisting of a C=O group which not only does take part in the conjugation but also pulls electrons from the chain making the whole system highly polar, thus affecting the vibrational transition moments. In the following we show, for the first time, that it is possible to derive experimental phonon dispersion curves and these prove to be different for each chain length. We support our experimental findings with Density Functional Theory quantum chemical calculations which reproduce with sufficient accuracy the IR and Raman spectral pattern and at the same time help in disentangling the assignment of the fine structure observed in the experimental spectra.