A novel label-free method for determination of inorganic mercury in environmental aqueous media using BSA-modified silver nanoparticles

A selective colorimetric sensor was developed for rapid and fast determination of highly toxic Hg²⁺ according to decolorization of unmodified silver nanoparticles (AgNPs). A simple strategy was used for providing water-soluble AgNPs. Bovine serum albumin (BSA) and sodium borohydride were used as stabilizing and reducing agents, respectively. AgNPs, prepared by BSA, were stable for 2 months. The freshly prepared bio-stabilized AgNPs were brownish yellow in color owing to the severe surface plasmon resonance (SPR) peak at 420 nm. The yellow AgNPs solution became colorless in the presence of Hg²⁺, as well as a gradual blue shift, and decrease in the intensity of absorption peak was observed with increasing the concentrations of mercury, because of aggregation of the nanoparticles. The calibration curve was linear from 5 to 80 µM (r = 0.994). The detection limit was 2.7 µM. Selective determination of mercury (II) ions was performed in the presence of other ions. To investigate the practical applications of BSA/AgNPs in real samples, mercury determination was performed in a groundwater sample and good recoveries (>94.0 %) were obtained.