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

- A europium(III)-based IL was synthesized and incorporated in different quantities in a chitosan matrix.
- The chitosan-SPEs were prepared through the solvent casting method.
- The morphological, thermal, electrochemical, optical, and photophysical properties of the SPEs were evaluated.
- The SPEs exhibited quite high ionic conductivity and emitted the typical Eu3+ red luminescence.

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 ([C2mim][Eu(SCN)4]). The chitosann[C2mim][[Eu(SCN)4] membranes exhibited a semi-crystalline morphology and good thermal stability (Tonset ≈ 134 °C). The sample with the highest ionic conductivity was the chitosan4[C2mim][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 5D0 → 7D2 transition, as it is typical for Eu3+ luminescent materials. The chitosan0.5[C2mim][Eu(SCN)4] sample emitted red luminescence with a lifetime of 0.397 ms. The chitosan1[C2mim][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.

126