Effect of Laser Repetition Rate on the Physicochemical Properties and Antibacterial Activity of PVP-Stabilized CuO Nanoparticles

Abstract

Copper oxide (CuO) nanoparticles are promising antibacterial materials due to their broad spectrum antimicrobial activity and low cost. The pulsed laser ablation in liquid (PLAL) technique provides a green and contamination free means for CuO nanoparticles synthesis. The laser repetition rate is an important parameter influencing the formation and yield of nanoparticles. In this study, the effect of laser repetition rate on physicochemical properties and antibacterial activity of CuO nanoparticles stabilized with polyvinylpyrrolidone (PVP) synthesized by PLAL was studied. CuO nanoparticles were prepared by laser ablation of a copper target in 5 mM PVP solution using a Nd:YAG laser (1064 nm, 30 mJ, 7 ns) at 10, 15 and 20 Hz repetition rates. The synthesized nanoparticles were characterized by UV–Vis spectroscopy, transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Antibacterial activity was determined by disk diffusion method against Staphylococcus aureus and Escherichia coli. The UV–Vis spectra showed the characteristic absorption peaks of CuO at 288–292 nm. With the increase in repetition rate, the absorbance intensity increased from 0.886 to 1.340 indicating the enhanced nanoparticle production. TEM analysis revealed average particle sizes of 5.70, 7.00 and 8.24 nm for the nanoparticles synthesized at repetition rates of 10, 15 and 20 Hz, respectively. The formation of CuO nanoparticles has been confirmed by FTIR analysis. The results of antibacterial test showed that the inhibition zone diameter increased from 1.30 to 3.10 mm against S. aureus and from 0.90 to 2.40 mm against E. coli with the increase of repetition rate from 10 to 20 Hz. The increase in antibacterial activity was attributed to the higher nanoparticle concentration produced at higher repetition rates. The laser repetition rate is a key factor affecting the antibacterial performance, particle size and nanoparticle yield of PVP-stabilized CuO nanoparticles fabricated by PLAL. Higher repetition rates showed increased nanoparticle production and antibacterial activity suggesting that repetition rate is an effective parameter to tailor CuO nanoparticles for antimicrobial applications.

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