Fabrication of high-intensity electron transfer electrochemiluminescence interface for Hg2+ detection by using reduced graphene oxide-Au nanoparticles nanocomposites and CdS quantum dots

A novel electrochemiluminescence (ECL) biosensing interface for Hg2+ analysis was constructed based on the enhanced ECL signal from CdS quantum dots by reduced graphene oxide-Au nanoparticles (RGO-AuNPs) nanocomposites. RGO-AuNPs were prepared by the heat-treatment of graphene oxide and HAuCl4 solution under alkaline environment. The prepared RGO-AuNPs composites were dispersed in N,N-dimethylformamide and dropped onto the surface of glassy carbon electrode (GCE). Double-stranded DNA modified with amino at one end was then immobilized on the RGO-AuNPs/GCE surface in the presence of 1-pyrenebutyric acid N-hydroxysuccinimide linker, following which the avidin-modified CdS quantum dots were linked to double-stranded DNA labeled with biotin at another end through the formation of biotin-avidin complex. The excellent electrical conductivity of RGO-AuNPs nanocomposites and the high charge transfer efficiencies of the double-stranded DNA with T-Hg2+-T complex, which produced high-intensity electron transfer interface and improved the sensitivity of the biosensor. After Hg2+ was added into the detection solution, the increased ECL signals showed good correlation with Hg2+ concentration. The linear range of the sensor was 5.0 × 10−13-1.0 × 10−9 M with a detection limit of 2.0 × 10−13 M. This ECL biosensor showed satisfactory results when used for detecting Hg2+ in real lake water.