Microwave-Assisted Synthesis of Colloidal Ag Nanocrystals and Colorimetric Detection of Mercury (I and II) Ions in Aqueous Solution

Monodispersed colloidal silver nanocrystals (Ag NCs) were obtained under microwave irradiation based on a simple reduction of silver nitrate in the aqueous solution of Gum Arabic, which served as both the reducing agent and stabilizing agent for Ag NCs. Introduction of Hg ^{n +} (n = 1 and 2) into a diluted aqueous solution of Ag NCs led to a concomitant colorimetric response, resulting from the formation of silver amalgam. Due to the great specific amalgamation between silver and mercury, the sensor system was highly sensitive and selective for Hg ^{n +} ions, rather than other environment relevant metal ions. The calibration curve showed that the net absorption value at 416 nm decreased in a linear correlation over the Hg ^{n +} concentration ranging from 1.0–80.0 μM with a limit of detection of 200 nM. This study provided an environmentally friendly method for the synthesis of Ag NCs with outstanding selective and sensitive detection of toxic Hg ^{n +} (n = 1 and 2) simultaneously.