Label-Free Electrochemiluminescent (ECL) Determination of Mercury (II) Based upon the Cation Exchange Reaction with Cadmium Sulfide Nanowires.

An electrochemiluminescence (ECL) sensor for mercury (II) was developed based on the cation exchange reaction between Hg2þ and CdS due to the large difference in the sedimentation equilibrium constant. To fabricate the sensor, CdS nanowires (CdS NWs) serving as the emitter were introduced upon a glass carbon electrode (GCE). Gold nanoparticles (Au NPs) with excellent electrical conductivity were introduced on the surface of CdS NWs/GCE to enhance the sensor performance. In the presence of Hg2þ, the electrochemiluminescence of the sensor decreased. The electrochemiluminescence intensity was negatively correlated with the concentration of Hg2þ. The excellent performance of Au NPs:CdS NWs/GCE, combined with the difference in the CdS and HgS sedimentation equilibrium constants, endows the sensor with good selectivity and sensitivity for the analyte. A long linear range from 6.7x10-15 M to 1.0x10-8 M was obtained for Hg2þ with a detection limit of 5.0x10-15 M. The applicability of the method was validated by the analysis of water and lake water. [ABSTRACT FROM AUTHOR]