Green Synthesis of Copper Nanoparticles Using Citrullus colocynthis Peel Extract and Antibacterial Activity for Biomedical Applications

Abstract

A novel and green method was developed to synthesise copper nanoparticles (CuNPs) using Citrullus colocynthis peel extract as a sustainable source. The study is the first to utilise this extract for the environmentally safe and economically efficient synthesis of CuNPs. The impact of experimental parameters, including the copper sulfate concentration, extract volume, reaction time, and temperature, on the synthetic procedure was thoroughly investigated. The as-prepared CuNPs were characterised using HRTEM, FESEM, XRD, EDX, UV–vis spectrophotometry, and FTIR spectroscopy. The CuNPs exhibited a spherical morphology with an average particle size of 9 nm, and the calculated d-spacing values were measured at 0.257 nm. Furthermore, the XRD analysis revealed characteristic diffraction peaks at 2 θ angles of 44.56°, 56.1°, and 71.4°. The UV–Vis absorption spectra of the CuNPs displayed a surface plasmon resonance (SPR) peak at 335 nm, corresponding to an energy band gap of 3.47 eV. Further, the FTIR spectra confirmed the interaction between copper and the biomolecules present in the extract, providing evidence of the significant role played by organic compounds in the capping process. The as-prepared CuNPs exhibited strong antibacterial activity against both gram-negative ( P. aeruginosa and E. coli ) and gram-positive ( S. aureus and S. epidermidis ) bacteria.