Graphene nanosheets modified with curcumin-decorated manganese dioxide for ultrasensitive potentiometric sensing of mercury(II), fluoride and cyanide.

A glassy carbon electrode (GCE) was modified by electropolymerization of curcumin on MnO2-Gr nanosheets to obtain a detection method for Hg(II) and for the anions fluoride and cyanide. The complexation by curcumin can be monitored by potentiometry. The results revealed a cathodic shift for the simultaneous detection of fluoride and cyanide and an anodic shift for the mercury(II) sensing, with peak potentials of -0.24, 0.12 and 0.82 V, respectively (vs. Ag/AgCl). The modified GCE is fairly selective, reproducible and repeatable. The detection limits are 19.2 nM for Hg(II), 17.2 nM for fluoride, and 28.3 nM for cyanide (LOD, S/N = 3). The method was successfully applied to the analysis of spiked samples of tap water, river water and petrochemical refinery wastewater. Graphical abstract Schematic of an electrochemical curcumin-MnO2-graphene nanosheet platform for the simultaneous assay of fluoride, cyanide and mercury(II) in the ppb concentration range in various natural and wastewater samples.