Determination of Hg(II) in water samples using silver nanoparticles functionalized with mercaptoethane sulfonate by a portable nanodrop spectrophotometry system

The most significant negative impact of environmental mercury pollution occurs in aquatic ecosystems, where mercury accumulates in organisms over time, reaching increasingly higher concentrations. The neurotoxic effects of mercury accumulation in the human body have been well documented in poisoning incidents worldwide. Consequently, the development of rapid and straightforward techniques for mercury detection in water is essential. In this study, we present a spectrophotometric method for the determination of Hg²⁺ in water, based on its interaction with silver nanoparticles functionalized with sodium 2-mercaptoethanesulfonate (Ag@MESNA). These nanoparticles possess free electrons in their conduction band, resulting in a strong interaction with incident radiation at 392 nm. Upon contact with Hg²⁺, a complex is formed with the mercaptoethanesulfonate ligand, leading to a decrease in the absorbance signal of the functionalized nanoparticles. This decrease is proportional to the mercury concentration in the sample. Measurements were performed using a nanodrop spectrophotometer, which requires only a few microliters of sample. The proposed method is simple, rapid, and portable, enabling in-situ quantification of ionic mercury in water. Moreover, it has been successfully applied to real water samples from various sources.