Irradiation Effect on the Optical Properties of Silver Nanoparticles Prepared by Pulsed-Laser Ablation in Liquid

In this work, colloidal silver nanoparticles (Ag NPs) are prepared using the pulsed-laser ablation in liquid (PLAL) technique. The study is focused on clarifying the effect of the number of laser pulses used on the optical properties of nanoparticles of high-purity silver targets immersed into 5 mL of deionized distilled water. The laser used is a Nd:YAG Q-switched laser with a fixed energy of 260 mJ, a wavelength of 532 nm, a pulse duration of 10 ns, and a frequency of 1 Hz. 100, 200, and 300 pulses are used to prepare the nanoparticles. The prepared particles are then irradiated with energy of 260 mJ and a set of 300 pulses of ultraviolet UVC rays with time intervals of 1–5-hour increments of one hour each time. The effect of UV-irradiation times on colloidal nanoparticles is studied through optical absorption and optical energy-gap analysis. The behaviour of the UV and visible absorption spectra of silver nanoparticles is also studied as functions of wavelength and number of pulses. These results show that the intensity of absorbance increases with an increase in the number of pulses, and this indicates an increase in the concentration of nanoparticles. As also noted, Ag NPs have a single sharp absorption peak between 404–407 nm for an energy of 260 mJ. Through the absorption spectrum, the optical energy gap is also calculated for Ag NPs; the calculations show an increase in the power value with increasing number of laser pulses. Optical constants are also calculated, and it is observed that their values increased with increasing number of laser pulses. On the other hand, the results of the UV–Vis absorption spectrum show a decrease in the absorption peaks as functions of the time of ultraviolet irradiation.