Synthesis and Characterization of Gold Nanoparticles and Study of Their Interaction with Hydroxyl Radicals

Abstract

Nanoparticles have been extensively employed in different fields such as medicine, optics, physics, biology and chemistry, due to its optical, thermal, magnetic and reactivity properties can be controlled by changing the size of these particles without to vary the composition of the material. At present, they have made significant progress to synthesize high-quality nanostructures, mainly metal nanoparticles and semiconductor nanocrystals. Gold nanoparticles (AuNPs) are of great interest because their chemical properties, i. e. molecular recognition, reactivity, biological properties i. e. DNA-AuNPs assemblies and physical properties, i. e. optical properties and electrochemical properties. This work deals with the interaction of gold nanoparticles (AuNPs) with hydroxyl radicals. The results obtained in this research constitutes a first theoretical and experimental approach for to evaluate AuNPs as a sensor to free radicals. In a first stage, the synthesis of gold nanoparticles was performed in aqueous media by reaction with tetrachloroauric acid (HAuCl4) and sodium citrate as reducing agent in a reflux system. The synthesis process was analyzed by using a factorial design experiment which considered different concentrations of reducing agent, temperature and stirring rate. In this analysis, the reducing agent concentration and temperature are significant variables and have a positive influence on AuNPs size, i. e. an increase of these produce an increase in the nanoparticle size. Later, AuNPs were characterized by UV-Vis spectroscopy where the corresponding absorption spectrums were obtained. In addition, AuNPs were immobilized on a silicon surface by means of a electrostatic irreversible deposition. A potential difference of 40 V was applied at different times between the p-type silicon and a graphite electrode immersed in the colloidal media containing the AuNPs. Afterwards, the modified silicon surface was analyzed by Atomic Force Microscopy (AFM) where size and AuNPs distribution were analyzed . Finally, the AuNPs were exposed to hydroxyl radicals coming from a Fenton reaction. During the interaction, the intensity and wavelenght of the absorption maximum was monitored as function of time. Additionally, the morphological change after interaction was analyzed. The results obtained in this conditions show slight changes in the AuNPs properties. However, this study can be extended to other radicals which can present a stronger interaction with these nanoparticles. Figure 1