Sub-ppt level voltammetric sensor for Hg2+ detection based on nafion stabilized l-cysteine-capped Au@Ag core-shell nanoparticles

Bimetallic nanoparticles (BMNPs) have received considerable attention due to their distinctive properties when compared to the corresponding monometallic NPs and their bulk counterpart. In this report, the formation of gold@silver core-shell nanoparticles (Au@AgCSNPs) was achieved via a one-pot synthetic approach after mixing 1:1 M solutions of Au and Ag ions. L-cysteine was used as reducing as well as capping agent for preparing Au@AgCSNPs. Ultraviolet-visible (UV-Vis) spectroscopy was employed for surface plasmon study while Fourier-transform infrared (FTIR) spectroscopy gave insights for interaction of NPs with specific functionality of the capping material. Surface morphology of the fabricated Au@AgCSNPs, probed by atomic force microscopy (AFM), indicated an average height of nanoparticles around 43 ± 3 nm and their crystallinity were confirmed via powder X-ray diffraction (PXRD) study. Significantly, the as synthesized Au@AgCSBMNPs were fabricated onto the conductive surface of glassy carbon electrode (GCE), stabilized with nafion, and then utilized as an extremely sensitive/greatly selective sensor for voltammetric detection of Hg2+. The developed sensor responded linearly to Hg2+ between 0.001 and 19 ppb with limit of detection (LOD) as low as 0.0001 ppb (0.1 ppt). Finally, the sensor was effectively applied for Hg2+ detection in different groundwater samples and is workable at concentrations undetectable by several sensing tools. [Figure not available: see fulltext.]