Photoluminescence in non-conjugated polyelectrolyte films containing 7-hydroxy-flavylium cation
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Chitosan–carboxymethylcellulose/flavylium salt (Ch–CMC/FS) films were obtained at different flavylium salt (FS) concentrations under acidic conditions in order to maintain de benzopyrylium form of the flavylium organic cation. Films were characterized by Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, UV–Vis diffuse reflectance (DRUV) and emission spectroscopy. Thermal properties were also recorded by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. FTIR and Raman spectra showed shifting of the carbonyl vibrations after addition of flavylium salt compound. Thermal stability prevailed even after addition of FS as was determined by TGA and DSC analysis. Ch–CMC/FS showed strong absorption in the visible part of the electromagnetic spectrum centred around λ = 450 nm. Luminescence profile after excitation at λ = 450 nm showed an emission centred around λ = 507 nm. FS appears to be chemically stabilized by the interaction with polyelectrolyte chains.
KeywordsFlavylium salt Chitosan Carboxymethylcellulose Polyelectrolyte Fluorescence
GZG thanks to Consejo Nacional de Ciencia y Tecnología (CONACyT) for support (CB-2013-01-222847 and INFRA-2015-01-251400). ASEM thanks CONACyT for a postdoctoral scholarship. DEV acknowledges the support given by PRODEP (OF-178204) and CONACyT (Grant No. 207363). Thanks to Raúl Orozco-Mena from Universidad Nacional Autónoma de Chihuahua for the recording of Raman spectroscopy.
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