Eco-friendly luminescent hybrid materials based on EuIII and LiI co-doped chitosan

Biopolymer-based materials have been of particular interest as alternatives do 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, giving rise to materials with increased functionality, of particular interest for electrochemical devices. In this study, we investigate chitosan based luminescent materials doped wit Eu3+ and Li+ triflate salts from the structural, photophysical and conductivity points of view. Because the host presents a broad emission band in the blue to green, while Eu3+ emits in the red, fine tuning of emission colour and/or generation of white light is possible by optimizing composition and excitation scheme. Europium lifetimes (5D0) are in the range 270 – 350 µs and quantum yields are as high as 2%. Although Li+ does not interfere with the luminescent properties, it grants ion-conducting properties to the material suggesting that a combination of both properties could be further explored in multifunctional device.

We are grateful to the Fundação para a Ciência e Tecnologia and FEDER (PEst C/QUI/UI0686/2013) and program POPH/FSE, grant SFRH/BD/97232/2013 (R. Alves), for financial support of this work. The authors are also grateful to FAPESP (CEPID 2013/07793-6 and PD fellowship 2013/24727-7), and CNPQ (Universal Project 479672/2012-1) and CAPES for the financial support. M. M. Silva acknowledges CNPq (PVE grant 406617/2013-9), for the mobility grant provided by this institution. The help from Dr. Reza Dousti in measuring quantum yields is greatly appreciated.