Eco-Friendly Luminescent Hybrid Materials Based on EuIII and LiI Co-Doped Chitosan

Biopolymer-based materials have been of particular interest as alternatives to synthetic polymers due to their low toxicity, biodegradability and biocompatibility. Among them, chitosan is one of the most studied ones and has recently been investigated for the application as solid state polymer electrolytes. Furthermore, it can serve as a host for luminescent species such as rare earth ions, opening up the possibility of combined electro-optical functionality, of particular interest for electroluminescent devices. In this study, we perform a fundamental, initial, investigation of chitosan based luminescent materials doped with EuIII and LiI triflate salts, from the structural, photophysical and conducting points of view. Because the host presents a broad emission band in the blue to green, while EuIII emits in the red, fine-tuning of emission colour and/or generation of white light is proven possible, by proper combination of optimized composition and excitation scheme. Europium lifetimes (5D0) are in the range 270-350 µs and quantum yields are up to 2%. Although LiI does not interfere with the luminescent properties, it grants ion-conducting properties to the material suggesting that a combination of both properties could be useful in the development of electro-luminescent devices.