Green Synthesis of Copper Sulphide Nanoparticles Using Extracts of Syzygium cumini, Azadirachta indica, and Cascabela thevetia

Nanotechnology is a burgeoning modern technology due to the remarkable properties of nanoparticles. However, the escalating use of toxic reagents during the chemical synthesis of nanoparticles has become a major concern for environmental safety and human and animal health. Regarding this problem, the notion of integrating nanotechnology with green synthesis is increasingly attracting the attention of researchers. This particular study aims at the green synthesis of copper sulphide (CuS) nanoparticles S1, S2, and S3 utilizing the leaf extracts of Azadirachta indica (neem), Syzygium cumini (jamun), and Cascabela thevetia (kaner), respectively. The prepared leaf extract of neem is rich in quercetin, whereas extracts of jamun and kaner leaves contain gallic acid, which serves as a reducing agent during the formation of nanoparticles. The prominent and sharp peaks of x-ray diffraction (XRD) patterns match well with ICDD card no. 06-0464, which confirms the hexagonal phase of covellite CuS. Scanning electron microscopy (SEM) images reveal the formation of spherical-shaped CuS nanoparticles with mild agglomeration. The presence of Cu and S as the only elements in the synthesized samples is confirmed by energy-dispersive x-ray analysis (EDX). The occurrence of various stretching and bending vibrational modes is observed via Fourier transform infrared (FTIR) spectroscopy. Furthermore, the obtained FTIR spectra of S1, S2, and S3 evince the formation of CuS nanoparticles and the presence of bioactive compounds. The UV-Vis absorption data of the prepared samples reveal that their band gap energies lie within the range of 1.5–1.7 eV. The photoluminescence (PL) spectra of S1, S2, and S3 display decreased intensity, which could be due to the reduced recombination rate of charge carriers. The CuS nanoparticles synthesized with neem leaf extract exhibit relatively smaller crystallite size, wider band gap of 1.7 eV, and a lower recombination rate of charge carriers.