Monitoring of diameter of gold nanoparticles using ultraviolet-visible spectroscopy

Abstract

This research presents monitoring of average diameter and concentration of gold nanoparticles (NPs) using ultraviolet-visible (UV-Vis) spectroscopy. The reliability of the UV-Vis spectroscopy is verified by comparing it to the transmission electron microscopy (TEM) results. One of the main objectives of this study is to determine the gold nanoparticles' diameter and concentration evolution with ablation time. Also, the properties of gold NPs produced by using Pulsed Laser Ablation in Liquids (PLAL) in four different liquids were analyzed and compared. Deionized water, distilled water, ethanol mixture (70% ethanol, and 30 % deionized water), and polyvinyl alcohol (PVA) are used in the experiment as the liquid media. The laser source used is a Q-switched Nd: YAG laser with an energy of 315 mJ, a repetition rate of 1 Hz, and a wavelength of 1064 nm. The laser ablation was conducted for the duration of 60 minutes at room temperature to obtain the pure colloidal solution of gold NPs. The diameter of the gold NPs obtained from UV-Vis spectroscopy is 7.19 nm in deionized water. The diameter of gold NPs from TEM is 7.117 nm. The results between UV-Vis spectroscopy and TEM are relatively comparable. In the case of laser ablation in deionized water, the gold nanoparticle size does not change significantly with time. The average diameter over ablation time is 41.686 nm. The results also illustrate that the concentration of gold nanoparticles depends on ablation time. By increasing the ablation time, the concentration increased. The slope of concentration against ablation time is 2.11×109????-3??????/. By comparing the gold NPs concentration and average diameter, the demonstration showed that distilled water has the smallest average diameter of 38.09 ???? and the highest concentration 3.67×1011 ????-3. In contrast, ethanol mixture has the largest average diameter of 74.38 nm and the smallest concentration of 5.31×109????-3. From these results, it is confirmed that UV-Vis spectroscopy is able to monitor the size and concentration of gold NPs by using PLAL in liquids.