A highly sensitive electrochemical sensor for the detection of lead(ii) ions utilizing rice-shaped bimetallic MOFs incorporated reduced graphene oxide

Abstract

The detection of lead ions (Pb²⁺) in water is of critical importance due to the harmful effects of lead on human health and the environment. Traditional detection methods often require high user expertise, expensive equipment, and complex analytical procedures. Electrochemical sensors have emerged as effective alternatives due to their portability and affordability. In this study, a novel electrochemical sensor was developed for the sensitive and selective detection of Pb²⁺ based on glassy carbon electrodes (GCE) modified with bimetallic metal–organic frameworks (MOFs) and reduced graphene oxide (rGO). The bimetallic MOFs were successfully synthesized via a hydrothermal method, combining two metal centers Fe and Mg linked to a 1,4-benzene dicarboxylate ligand (FeMg-BDC). The synthesized FeMg-BDC has higher conductivity and surface area than monometallic Fe-BDC or Mg-BDC MOFs. Thanks to the synergistic effects between FeMg-BDC and rGO, the rGO/FeMg-BDC electrode has a larger electrochemically active surface area and faster electron transfer rate than the bare GCE. This enhancement facilitated the accumulation of lead onto the electrode surface, thereby improving the sensitivity of Pb²⁺ ion detection. Using the square wave anodic stripping voltammetry method, the sensor based on rGO/FeMg-BDC electrode exhibited two linear ranges: 0.01 to 0.5 μg L⁻¹ and 0.5 to 50.0 μg L⁻¹, with a low limit of detection (LOD) of 9 ng L⁻¹. Furthermore, the external rGO thin film protects the FeMg-BDC material on the electrode surface, ensuring high durability and repeatability of the sensor. The developed sensor was successfully applied to accurately determine lead ion concentrations in various real water samples.