Green synthesis, characterization and antibacterial activity of copper nanoparticles

Nanoparticles are synthesized by chemical and physical processes. These methods are suffering from problems like dangerous reaction condition, expensive reagent, longer time, difficultly process to isolate nanoparticles. Green synthetic methods using plant extracts have been produced metal nanoparticles without the use of physical/chemical processes [1,2]. In this work, copper nanoparticles (Cu NPs) were prepared with green synthetic methods using aqueous extract of galls of Quercus infectoria (Q. infectoria) as reducing and capping agent. Fourier transform infrared (FT-IR), ultraviolet-visible (UV–Vis) spectrophotometry, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Transmission Electron Microscope (TEM) and spectrum X-ray diffraction (XRD) were used to characterize the samples. The results from the characterization techniques proved the formation copper nanoparticles by this novel reduction method. Highly stable Cu NPs have spherical morphology with average size about 20 nm in diameter. Antibacterial activity of the Q. infectoria galls extract and copper nanoparticles was evaluated against two Gram-positive bacteria (Bacillus cereus, Staphylococcus aureus) and four Gram-negative bacteria (Escherichia coli, Klebsiella pneumonia, Acinetobacter baumannii and Pseudomonas aeruginosa). The galls of Quercus infectoria extract and Cu NPs showed excellent antibacterial activity toward six types of bacteria. The result proved that galls extract as compared to the conventional physical and chemical processes is a very good eco-friendly and nontoxic source for the synthesis of Cu NPs.