Luminescent Transparent Composite Films Based on Lanthanopolyoxometalates and Filmogenic Polysaccharides

A series of polysaccharide-based transparent composite films containing lanthanopolyoxometalates (LnPOMs) have been prepared by using a water-soluble cationic chitosan derivative [HTCC = N-(2-hydroxypropyl)-3-trimethylammonium chitosan chloride] and pullulan (PUL). HTCC was more suitable than pure chitosan for this purpose due to its positive charge and solubility in water over a broad range of pH values. The LnPOMs [Ln(W5O18)2]9 (Ln = Eu and Tb) were incorporated into the polysaccharides. EuPOMs encapsulated in amorphous silica shells were also incorporated into the polysaccharides to test the effect on film processing of the loading of nanoparticles instead of LnPOM anions. The incorporation of LnPOMs or LnPOM/silica core/shell nanoparticles into either HTCC or PUL polysaccharides originated clear transparent films. These composite films are transparent in daylight and exhibit visible emission under UV excitation. Photoluminescence studies (emission and excitation spectra and emission decay curves) were performed on the newly prepared films.