Sensitive electrochemical platform for trace determination of Pb²⁺ based on multilayer Bi-MOFs/reduced graphene oxide...

A multilayer Bi-BTC/reduced graphene oxide (Bi-BTC/rGO) (BTC, 1,3,5-benzenetricarboxylic acid) film electrode was adopted to construct a highly sensitive Pb²⁺ electrochemical sensor. The multilayer Bi-BTC/rGO films were prepared via alternate cast of Bi-BTC and graphene oxide (GO) on a glassy carbon electrode, followed by electro-reduction of the GO components. Bi-BTC has porous broom-like structure and its organic ligand has abundant functional groups, which are favorable for Pb²⁺ adsorption and preconcentration. The introduction of rGO layer improves the conductivity of the MOFs material. Moreover, the multilayer composite structure greatly increased the exposure of active sites and the surface area of reactive contact, finally realizing the highly sensitive detection of Pb²⁺. Pb²⁺ was determined by differential pulse anodic stripping voltammetry and the response current was recorded at - 0.62 V. The [Bi-BTC/rGO]₂ electrode provides a wide linear response ranging from 0.062 to 20.72 μg/L and a low limit of detection (LOD) of 0.021 μg/L (S/N = 3) for Pb²⁺, which is lower than the guideline value proposed by the World Health Organization. The method has been applied to determine Pb²⁺ in industrial wastewater with recoveries of 99.2-104% and RSDs of 3.4-4.0% (n = 3). Graphical abstract Graphical abstract Schematic representation of an electrochemical sensor for the detection of Pb²⁺ was designed based on long broom-like structure bismuth(II) metallic organic framework/reduced graphene oxide ([Bi-BTC /rGO]₂).