Electrochemical and photoluminescence properties of Ce3+ doped copper aluminate nanoparticles

Abstract

In this communication, for the first of its kind, CuAl2O4 doped with Ce³⁺ (1-9 mol %) are syn- thesized by solution combustion method using Aloe Vera gel as a reducing agent. The as-formed sample was calcined at 500° C for 3 hours, followed by characterization. The addition of dopants to the copper aluminate matrix didn't alter the crystal structure of the host matrix. Bragg reflec- tions confirm the formation of the cubic phase and also absence of other impurities. The surface morphology consists of nanorods arranged one above the other. The estimated crystallite size was found to decrease from 12 to 9 nm whereas, the direct energy band gap increases from 2.84 to 3.02 eV with an increase in dopant concentration. Under λex = 305 nm excitation, photoluminescence (PL) emission spectra have a high intense peak at 553 nm along with a less intense peak at 472 nm. The peak at 553 nm can be attributed to the existence of oxygen vacancies which arise due to the transition of an electron from the ²D_3/2 → ²F_7/2 of Ce³⁺, however, the peak observed at 472 nm results from the transition of ionized oxygen vacancies (VO) to the valence band caused by the ²D_3/2 → ²F_5/2 transition. The CIE coordinates lie well within the green region with 5758 K aver- age CCT. Further, Cyclic voltammetry analysis was conducted to investigate oxidation and redox peaks, while electrochemical impedance spectroscopy provided insights into ion transport kinetics. Specific capacitance values ranging from 29 to 59 F/g were obtained for CuAl₂O₄:Ce(1-9 mol %) NPs. These findings suggest potential applications for the synthesized material in areas such as display technology as a green nano phosphor and energy storage materials.