Controlling the fluorescence intensity of luminescent thin films by photoisomerization of azo dyes

Abstract Luminescent poly p-phenylene vinylene (PPV) thin films were produced by the layer-by-layer technique, using organic dyes as the counter ion. It was observed that, when dyes with azo groups are incorporated in the PPV polymeric chains, the fluorescence intensity can be substantially increased by the photo-irradiation of the film with a linearly polarized laser beam. The data show that such emission enhancement is due to the alignment of the dye molecules caused by the photo-isomerization of the azo groups. This process leads to an absorbance of the dyes that is dependent both of the photo-irradiation dose and the polarization direction of the irradiation source, which affects the fluorescence emitted by the polymer. Thus, the incorporation of azo dyes can be used to modulate the fluorescence response of polymeric thin films.