Bluish-green luminescence and electrochemical properties of cerium-doped zinc chromite nanoparticles for display and energy storage applications

Cerium-doped zinc chromite (ZnCr<inf>2</inf>O<inf>4</inf>:Ce) nanoparticles were synthesized using the Solution Combustion Method (SCM), employing Aloe vera gel extract as a green fuel. Post-synthesis calcination at 500 °C for 3 h enhanced crystallinity. X-ray diffraction confirmed the formation of a single-phase cubic spinel structure (space group Fd-3m), with crystallite size decreasing from 15.56 to 12.06 nm at 9 mol% Ce3+, as determined by Scherrer’s formula. Transmission Electron Microscopy corroborated these results, revealing well-dispersed nanoparticles and nanorods. UV–Vis spectroscopy indicated a band gap reduction from 2.98 to 2.94 eV with increasing Ce3+ content, attributed to dopant-induced localized states. Photoluminescence under 238 nm excitation showed a strong emission at 490 nm and weaker emissions at 726 and 736 nm. Emission intensity peaked at 7 mol% Ce3+ before decreasing at 9 mol%, confirming concentration quenching. CIE chromaticity coordinates and correlated color temperature (CCT) analysis verified bluish-green (aqua) emission, suitable for indoor lighting. Electrochemical characterization demonstrated promising energy storage behavior. Cyclic voltammetry showed clear redox peaks, and EIS revealed low charge–transfer resistance, indicating efficient ion transport. Galvanostatic charge–discharge measurements yielded specific capacitance values ranging from 84.29 F/g (undoped) to a maximum of 123.41 F/g at 5 mol% Ce3+, with a decline at higher doping levels due to structural distortion. Overall, the Ce3+-doped ZnCr<inf>2</inf>O<inf>4</inf> nanoparticles exhibit tunable optical and electrochemical properties, making them strong candidates for multifunctional applications in energy storage systems and optoelectronic devices.