Effect of ultraviolet irradiation on the optical properties and biological activity of silver nanoparticles prepared by pulsed laser ablation

Silver nanoparticles (AgNPs) are vital components in nanoscience and nanotechnology, principally in nano-antibiotics and nanomedicine. This work investigates the role of ultraviolet ray irradiation on the optical properties of AgNPs prepared by the pulsed laser ablation in liquid (PLAL) technique. In this framework, Q-switched Nd:YAG laser was utilized with different laser energies (200 and 400) mJ at different numbers of pulses (100, 200, 300, 400, and 500) to generate Ag nanoparticles. UV–visible spectrometer, transmission electron microscope (TEM), and field emission scanning electron microscopy (FE-SEM) measurements were all used to characterize the samples. The UV–visible spectroscopy showed a decrease in the surface plasmon resonance (SPR) peak position and an increase in the optical band gap of AgNPs with the increase in the number of laser pulses before irradiation with UVC. TEM and FE-SEM images revealed spherical-like shapes with an average diameter range of 33–51 nm. Beyond this, antibacterial tests of both Staphylococcus aureus and Escherichia coli by AgNPs showed a slight inhibition. After UVC-irradiation times, the absorbance intensity of AgNPs and the SPR peak (411–413) nm increased; the optical band gap, however, decreased. The results of our study showed a significant inhibitory effect against both Gram (+ve) and Gram (-ve) bacteria when AgNPs were irradiated by UVC.