Green engineered zinc chromite doped with Sm3+ nanoparticles: Structural, photoluminescence and supercapacitor properties

This groundbreaking research successfully synthesized Samarium-doped ZnCr₂O₄ nanoparticles (NPs) using the solution combustion method. Aloe vera gel extract is used as a reducing agent. As-formed samples are subjected to calcination at 500 °C for 3 h. X-ray diffraction analysis unambiguously proved pure cubic spinel structure. Notably, increasing the dopant concentration led to a drop in crystallite size from 13.89 ± 1.3 to 11.58 ± 1.1 nm. TEM image shows the existence of agglomerated irregularly shaped NPs and the evaluated crystallite size matches with Scherrer’s method. SEM images clearly indicates the formation of smaller, longer length nanorods and irregular size and shaped NPs with an increase in dopant quantity. The energy band gap ($E_g$) reduced from 2.91 to 2.87 eV. Photoluminescence (PL) measurements under a 293 nm excitation wavelength revealed a pronounced emission peak at 592 nm. The concentration quenching was observed at a 5 mol% doping concentration. The CIE and CCT coordinates unequivocally verified the orange red emission which can be attributed to ⁴G${}_{5/2}\to$ ⁶H${}_{7/2}$ transition of Sm${}^{3+}$ within the host lattice, providing a warmer appearance advisable for indoor lighting applications. Electrochemical analyses, including cyclic voltammetry, were performed to elucidate redox reactions, electrode kinetics, and electrochemical behavior. Ion transport kinetics were precisely determined through Electrochemical Impedance Spectroscopy, while supercapacitance values were assessed via Galvanostatic Charge–Discharge studies. Impressively, the supercapacitance values ranged from 89.35 and 130.92 F/g, highlighting their remarkable sensitiveness to dopant quantity. Thus, the NPs produced in this pioneering study holds promising applications in the realm of energy storage materials and in display technology.