Microwave-assisted rapid synthesis of copper nanoparticles with exceptional stability and their multifaceted applications

Abstract

Among the several transition metals known to mankind, the synthesis of Cu has remained a major challenge owing to their instinctive oxidative power under ambient conditions. The present work introduces a microwave-assisted one-pot method of synthesis of highly stable copper nanoparticles (CuNPs) in aqueous medium using hydrazine as reducing agent and leaf extract of Psidium guajava as the stabilizer. The effects of different synthesis parameters like precursor pH, temperature, quantity of stabilizing and reducing agent, power level and time of microwave irradiation on the formation of nanoparticles have been investigated. UV–vis spectra of the colloid display Surface Plasmon Resonance bands centered around 561–572nm, characteristic of copper nanoparticles. Comparative studies of FTIR spectra of the extract and copper nanoparticles reveal the involvement of different functional groups in stabilization. TEM micrographs and XRD patterns show the formation of nearly spherical nanoparticles of size around 15nm with face centered cubic structure. The catalytic efficiency of the synthesized copper nanoparticles has been portrayed through the degradation of the organic pollutants methylene blue, methyl red, methyl orange, eosin yellow, 2-nitrophenol and 3-nitrophenol. The in vitro cytotoxic effect of CuNPs on L929 fibroblast cells has been evaluated and found to be surprisingly small. Dose dependent antibacterial activity of the synthesized CuNPs against pathogenic gram negative Escherichia coli and gram positive Staphylococcus aureus has been investigated through agar-well diffusion method. Anti-oxidant potential has been depicted through DPPH, OH− and NO radical scavenging assays. Superior enhancement of thermal conductivity observed in CuNPs-water and CuNPs-ethylene glycol nanofluids promises their unambiguous exploitation as heat transfer fluids. The present method of synthesis can be extended effectively to large scale production of air-resistant CuNPs for a broad spectrum of environmental, biological and industrial applications.