Biogenic synthesis of copper oxide (CuO) NPs exploiting Averrhoa carambola leaf extract and its potential antibacterial activity

Abstract

Herein, we report our assiduous endeavor to meet one of the demands of 21st century, the green route of synthesis, for copper (II) oxide nanoparticles (CuO NPs) using Averrhoa carambola leaf extract for the first time. The synthesized CuO NPs was characterized by XRD, XPS, FESEM, FTIR, DLS, zeta (ζ)-potential and UV–Vis spectroscopic techniques. XRD revealed the monoclinic crystalline phase of the CuO NPs with crystallite size of 24.84 nm. XPS confirmed the surface elemental composition and Cu2+ oxidation state of CuO NPs. The formation of NPs was confirmed by the surface plasmon resonance (SPR) spectra based on the sharp absorption at 220 nm. FESEM images showed assorted shapes albeit spherical shapes were the dominant ones. The calculative particle size based on the FESEM images was 98 ± 26 nm whereas DLS analysis showed larger particle size (117 nm) because of hydro-dynamic volume. Zeta-potential of the synthesized CuO NPs was found to be −13.65 mV at neutral pH. FTIR analysis confirmed the presence of metal-oxide (Cu–O) bond. The synthesized CuO NPs were exploited as an antibacterial agent against 2 gram positive (Bacillus megaterium and Staphylococcus aureus) and 3 gram negative bacteria (Escherichia coli, Salmonella typhi and Pseudomonas aeruginosa). Salmonella typhi and Escherichia coli were found to be highly vulnerable to CuO NPs with the highest zone of inhibition of 26 mm and 24 mm respectively. Bio-resource based green synthesized CuO can be a potential candidate in the array of nanomedicine considering its fascinating activity against broad spectrum bacterial strains.