Colorimetric Detection of Cr3+ in Aqueous Solution Based on Cofunctionalized Silver Nanoparticles Modified with 4-Nitrobenzenethiol and 4-Mercaptobenzoic Acid

A new method has been proposed to realize the visual detection of Cr3+ using 4-nitrobenzenethiol (4-NBT) and 4-mercaptobenzoic acid (4-MBA) modified silver nanoparticles (AgNPs). The presence of Cr3+ induces the aggregation of AgNPs through cooperative metal-ligand interaction, resulting in a color change from bright yellow to purple. Consequently, Cr3+ could be monitored by colorimetric response of AgNPs by a UV-Vis spectrophotometer or even naked eyes. We firstly used ethylene diamine tetraacetic acid (EDTA) as a masking agent to selectively detect Cr3+, and other metal ions have little influence on the Cr3+-AgNPs system. The cofunctionalized AgNPs exhibited a highly sensitive detection limit of Cr3+, which is as low as 5 x 10(-9) mol L-1, and the absorbance ratio (A(600nm)/A(387nm)) is linear with the concentration of Cr3+ ranging from 5 x 10(-9) mol L-1 to 2 x 10(-6) mol L-1 with a coefficient of 0.993. Particularly, the sensor has been further evaluated to monitor the concentration of Cr3+ in drinking water, the recovery was in good agreement with those obtained by ICP-MS, indicating that this proposed method is successfully applied in real samples.