Optical and structural characteristics of La2O3-ZnO nanoparticles synthesized via the Co-precipitation technique: Potential for energy storage and biomedical applications

Abstract

This study reports the synthesis of a composite of lanthanum (La₂O₃)–zinc oxide nanoparticles (La-ZnONPs) using a simple and cost-effective co-precipitation method. The structural, morphological, compositional, and functional properties of the synthesized nanoparticles were systematically investigated. UV–visible spectroscopy revealed an excitonic absorption peak at ∼364 nm, and the optical band gap was calculated to be 2.9 ± 0.02 eV using the Kubelka–Munk method. Fourier-transform infrared (FTIR) spectroscopy indicated the vibrational modes of functional groups, with a prominent peak in the range of 3000–3600 cm⁻¹ corresponding to the O–H bond, while the absence of additional significant absorption bands confirmed the high purity of the nanoparticles. Transmission electron microscopy (TEM) revealed their morphology, and energy-dispersive X-ray spectroscopy (EDX) confirmed the elemental composition. X-ray diffraction (XRD) analysis showed a hexagonal wurtzite structure with an average crystallite size of ∼15 ± 0.01 nm. Electrochemical characterization demonstrated that La-ZnO electrodes exhibited a specific capacitance (Cp) of 0.8064 ± 0.001 F/g at a scan rate of 0.01 V/s, which decreased to 0.3758 ± 0.01 F/g at higher scan rates due to reduced interaction time between the active material and electrolyte ions. The observed pseudocapacitive behavior was attributed to oxygen vacancies and La incorporation, which enhanced the overall capacitance. The anticancer potential of La-ZnONPs was evaluated against colon cancer, MDA-MB-231 breast cancer, and HeLa cervical cancer cell lines using the MTT assay. The nanoparticles exhibited significant cytotoxicity, with cell viabilities of 28.5 ± 0.12 %, 25 ± 0.15 %, and 30.2 ± 0.14 % for colon, MDA-MB-231, and HeLa cells, respectively, demonstrating effective cytotoxicity at relatively low concentrations and highlighting their potential as anticancer agents. Unlike previous studies on La-ZnO, which primarily focused on structural and optical properties, this work demonstrates the dual functionality of La-ZnONPs by systematically assessing both their electrochemical and anticancer activities. These findings underscore their biomedical relevance and potential application in energy storage, offering a unique combination of multifunctional properties for future technological and therapeutic developments.