A one-step colorimetric method of analysis detection of Hg2+ based on an in situ formation of Au@HgS core–shell structures

A new approach for the detection of Hg2+ is reported based on color changes from which gold nanoparticles (Au NPs) are surrounded by a layer of HgS quantum dots to form in situ Au@HgS core–shell nanostructures. The surface plasmon resonance (SPR) absorption of the gold core was changed due to a shell layer of HgS formed on the surface of the Au NPs, which brings the colour change of the aqueous solution. Therefore, Hg2+ can be recognized by visualizing the colour change of the Au@HgS core–shell nanostructures, and can be detected quantitatively by measurement of the UV-vis spectra. Some effects on the detection of Hg2+ were investigated in detail. This method was used to detect Hg2+ with excellent selectivity and high sensitivity. In our method, the lowest detected concentrations for mercury ions were 5.0 × 10−6 M observed by the naked eye and 0.486 nM as measured by UV-vis spectra. At the range from 8.0 × 10−5 to 1.0 × 10−8 M of Hg2+, this method was shown to have a good linear relationship.