Facile Synthesis and Characterization of Silver Nanoparticles Based Sensors for Colorimetric Detection of Mercury Ions

Metals contamination is one the severe form of water pollutions. Mercury contamination is most hazardous among them and poses great threat to environment. It is need of hour to develop analytical methods for detection of even trace levels of mercury concentration in water sources. Highly sensitive and discriminatory colorimetric sensing platforms for Hg2+ ions are recorded for this purpose. Herein, we report the fabrication of functionalized silver nanoparticles (AgNPs) with protocatechuic acid (PCA). UV-Vis spectrophotometry confirmed the development of PCA-AgNPs. Transmission electron microscopy (TEM) was used to observe the shape and size distribution of PCA mediated AgNPs. The average diameter size was observed to be 11 nm and almost spherical in shape. Powder X-Ray diffractometry proved face centered cubic crystal of Ag. These PCA-AgNPs have been used for metal sensing. When Hg2+ solution was mixed with PCA-AgNPs solution, there was an apparent color transition from light brown to almost colorless. UV-Vis spectrophotometric measurements have confirmed this color transition. At 395 nm there was substantial decrease in the absorption band and new peak emerged at 550 nm. PCA-AgNPs exhibited reasonable sensitivity for Hg2+ in the concentration range of 1×10-7 to 5×10-5 M. This sensor was also tested in presence of many other metals to check the competing effect of other metals, but it showed no color change thus suggesting high sensitivity for mercury ions. This method also showed satisfactory percentage recoveries with different water samples.