UVC Irradiation Effect on Gold Nanoparticles Prepared by Pulsed Laser Ablation and their Biological Activity

Pulsed laser ablation in liquid technique was used to produce nanostructure materials from a gold metal plate immersed in double distilled water at different energies (200 and 400 mJ) and different numbers of pulses (100, 200, 300, 400 and 500) using a Q-switched Nd:YAG laser. Moreover, the prepared gold nanoparticles (AuNPs) were tested and characterized using different examined techniques. The optical, morphological and structural properties of AuNPs were characterized by an UV-visible spectrometer, transmission electron microscope (TEM), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction. It was found that by increasing in the number of laser pulses before irradiation, the UV-visible spectroscopy revealed a decrease in the surface plasmon resonance (SPR) peak position and an increase in the optical band gap of AuNPs. TEM and FE-SEM images showed spherical-like shapes with average diameters ranging from 34 to 44 nm. AuNP face centered cubic crystallinity was evident from XRD. Moreover, antibacterial tests with AuNPs on Staphylococcus aureus and Escherichia coli showed a mid-level inhibition. In addition, the AuNP absorbance intensity and SPR peak at 522–525 nm increased after the UVC irradiation, while the optical band gap of the samples slightly decreased. The AuNP UVC-irradiation exhibited a significant inhibitory effect against Gram(+ve) and Gram(–ve) bacteria.