A highly-sensitive electrochemical sensor for the simultaneous detection of Cd2+ and Pb2+ using liquid phase-exfoliated graphene

Abstract

It is quite important to develop sensitive and simple analytical methods for the detection of toxic heavy metal ions, such as Cd²⁺ and Pb²⁺. Herein, liquid phase-exfoliated graphene nanosheets were easily prepared through a one-step exfoliation of graphite powder in N-methyl-2-pyrrolidone. The obtained graphene suspension was directly used to modify the surface of a glassy carbon electrode (GCE), constructing a novel and highly-sensitive electrochemical sensor for Cd²⁺ and Pb²⁺. Compared with an unmodified GCE, and a reduced graphene oxide-modified GCE, the resulting liquid phase-exfoliated graphene-modified GCE significantly increased the response signals towards Cd²⁺ and Pb²⁺, showing remarkable signal amplification effects. The use of this defect-abundant, few-layered graphene sample, with small lateral flake sizes, has led to the beneficial responses observed. The influences of the supporting electrolyte, volume of the graphene suspension, deposition potential and accumulation time were examined. As a result, a sensitive, rapid and convenient electrochemical method was developed for the simultaneous detection of Cd²⁺ and Pb²⁺. The detection limits were estimated to be 1.08 μg L⁻¹ and 1.82 μg L⁻¹ for Cd²⁺ and Pb²⁺. This new sensor was used in water sample analysis, and the results were consistent with the values obtained by inductively coupled plasma-atomic emission spectroscopy.