Green synthesis of calcium oxide nanoparticles using Ocimum sanctum leaf extracts: photocatalytic and electrochemical sensor applications

The current work describes the environmentally friendly green method for fabricating CaO nanoparticles (NPs) using 'tulasi' (Ocimum sanctum) plant leaf extract as a unique fuel. The obtained CaO NPs have been characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), TEM/HRTEM (Transmission Electron Microscopy), UV-Vis spectroscope, Selected Area Electron Diffraction (SAED), and Energy Dispersive Spectroscopy (EDAX) techniques. The PXRD studies revealed the average crystallite size of 38 nm for CaO NPs and this value is in compliance with the TEM results. DRS studies revealed the energy gap of CaO as 3.20 eV. The plant-mediated CaO NPs showed good photocatalytic activities for the photodegradation of Fast Orange (FO) and Fast Blue (FB) dyes under the UV light irradiation, demonstrating high efficiency within 120 min of light irradiation. Under UV light, the CaO exhibited impressive photodegradation performance of 95.5% and 83.5% in 120 min against the FO and FB dyes. The electrochemical characteristics of CaO were studied using a carbon paste electrode in a 0.1 M NaOH solution. The green CaO NPs exhibited superior sensitivity in cyclic voltammetry tests at different scan rates when lead and lithium were utilized as analytes. The phase angle of CaO was determined to be - 47 degrees, which is close to the behavior of an ideal capacitor (- 90 degrees). Consequently, CaO holds potential for applications in electrochemical sensor technology.