Attenuated total reflection and emission due to surface plasmon excitation of layer-by-layer ultrathin films containing azo-dye

The properties of attenuated total reflection (ATR) and emission due to surface plasmon (SP) excitation were investigated for the alternate layer-by-layer ultrathin films self-assembled on Ag thin films using polycation (poly(diallyldimethylammonium chloride), PDADMAC) and azo-dye (Direct Red 80, DR80). The emission light had peaks at the same angles as the resonant angles of the ATR curves and the shapes of the emission spectra also corresponded to those of the ATR curves, and the emission was considered to be mainly due to the SP excitation mediated by the surface roughness of Ag thin films. The structure of the PDADMAC/DR80 layer-by-layer films was found to change due to the photoisomerization of DR80 molecules by the irradiation of polarized visible light, and the surface roughness of the layer-by-layer films was also found to increase by the irradiation and hardly to change after 5-min irradiation.