Facile and on-line colorimetric detection of Hg2+based on localized surface plasmon resonance (LSPR) of Ag nanotriangles.

A rapid and sensitive colorimetric detection method for the determination of Hg2+ has been successfully developed in this research. Citrate-functionalized silver nanotriangles (AgTrngs) were synthesized via one-pot sodium borohydride method with the edge-length range of 30 - 40 nm. The obtained AgTrngs were fully characterized using UV-Vis spectrophotometry, transmission electron microscopy (TEM), energy dispersed spectroscopy (EDS) and X-ray diffractometer. The efficiency of the developed sensor was optimum at pH= 8 due to interfering effect of H+ ions for Hg2+ under acidic conditions. The successful detection of mercury in aqueous solutions in the concentration range of 10 nmol L-1-50 μmol L-1 indicated the applicability of the developed sensor for effective monitoring and controlling the level of Hg2+ in industrial effluents. The ability of Hg2+ ion to interact with Ag and form the Hg-Ag alloy (amalgam) over the surface of AgTrngs resulted in an obvious color change from blue to violet. UV-Vis spectrophotometry showed that the sensor has the limit of detection (LOD) value of as low as 4 nmol L-1 which was below the safety level of Hg2+ions (10 nmol L-1) in drinking water. The proposed method can be used for on-line determination of Hg2+ in the complex aqueous solutions.