Picomolar Selective Electrochemical Sensing of Lead Ions by a Gold–Copper Nanocluster-Nitrogen-Doped Graphene Quantum Dot Combination

Abstract

This work explores and demonstrates the electrochemical sensing ability of a highly stable (≥1 year) bimetallic Cu–Au nanocluster, AuCuNC@N-GQD, toward Pb(II) with high selectivity. Pb(II) is one among the top 10 hazardous substances of foremost communal health concern in the list of the World Health Organization, and its prevalent usage in batteries and other industries has made the detection and one-to-one care of Pb(II) in environmental samples mandatory. The selective sensing is assigned to the selective interaction between Au(I) in AuCuNC@N-GQD and Pb(II), and the heightened sensing properties were accredited to the electron-rich N-GQD, which facilitated the electron transport and reduction of Pb(II) to Pb(0). The LOD value was the lowest reported hitherto for Pb(II) with 1 pM (4.8 × 10–15 g/L); the previously reported lowest was 90 pM. The detecting capacity of AuCuNC@N-GQD/GCE was verified in samples collected from the environment, such as seawater, groundwater, and wastewater, which are Pb(II) spiked, and was found to perform efficiently with ≤100% recovery, with a corresponding relative standard deviation of <0.5%.