A luminescent europium ionic liquid to improve the performance of chitosan polymer electrolytes

Abstract Ionically conductive and luminescent chitosan solid polymer electrolytes (SPEs) were prepared through the solvent casting method and characterized with respect to their thermal behavior, morphology, structure, ionic conductivity, optical, and photophysical properties. The characterization was performed by analysis of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), complex impedance and photoluminescence spectroscopies. The chitosan-SPEs were doped with different quantities of 1-ehtyl-3-methylimidazolium europium(III) tetrathiocyanate ([C 2 mim][Eu(SCN) 4 ]). The chitosan n [C 2 mim][[Eu(SCN) 4 ] membranes exhibited a semi-crystalline morphology and good thermal stability (T onset  ≈ 134 °C). The sample with the highest ionic conductivity was the chitosan 4 [C 2 mim][Eu(SCN) 4 ] with 1.34 × 10 −5 and 1.97 × 10 −4  S . cm −1 at 30 and 80 °C, respectively. The photoluminescence analysis showed intense red emission corresponding to the 5 D 0  →  7 D 2 transition, as it is typical for Eu 3+ luminescent materials. The chitosan 0.5 [C 2 mim][Eu(SCN) 4 ] sample emitted red luminescence with a lifetime of 0.397 ms. The chitosan 1 [C 2 mim][Eu(SCN) 4 ] exhibited the best equilibrium between the membrane’s optical and photophysical features. These results encourage future investigations of these materials for application in electroluminescent devices.