Trace-Level Detection of Pb(II) and Cd(II) Aided by MoS₂ Nanoflowers and Graphene Nanosheet Combination

Abstract

Pb(II) and Cd(II) are featured in the World Health Organization’s (WHO) top 10 list of chemicals of primary public health concern, and their wide use in industries and the acute and chronic effects on humans and the environment make the detection and determination of the ions in environmental and drinking water samples indispensable. This work reports a detailed study on a partially reduced graphene oxide-nano molybdenum disulfide-modified glassy carbon electrode (prGO-MoS2/GCE), which exhibited the simultaneous and selective electrochemical detection of Pb(II) and Cd(II) in drinking water with a 200- and 100-fold increase in the current response, respectively, compared to that on the unmodified GCE. prGO-MoS2 showed almost nil current response for other metal ions such as Hg(II), Ag(I), Fe(II), Co(II), Ni(II), Zn(II), Sn(II), Cu(II), and Cr(VI), evident to the good selectivity toward Pb(II) and Cd(II). The lowest limit of detection (LOD) values were ∼0.0002 and 0.1 ppt, which are very well below the ≤10 and 5 ppb specified as safe for Pb(II) and Cd(II), respectively. The exemplary sensing behavior of prGO-MoS2/GCE toward Pb(II) and Cd(II) shall be assigned to the structure of prGO-MoS2 and the bonding of MoS2 to prGO, thus promoting the electrochemistry mechanism in addition to the affinity.