Engineering highly dispersed Bi nanoparticles via COF confinement for enhanced electrochemical sensing of Cd²⁺ and Pb²⁺ in grain

The presence of Pb²⁺ and Cd²⁺ in grain can have adverse effects on human health. Consequently, there is a pressing need for electrochemical sensors for rapid and sensitive detection of Cd²⁺ and Pb²⁺. Owing to their tunable porosity and structural versatility, covalent organic frameworks (COF) are increasingly being explored for electrochemical sensing applications. Herein, an imine-linked COF confined Bi nanoparticles (NPs) was fabricated by an environmentally friendly technique and an approach of chemical reduction. The COF substrate prevents the BiNPs from aggregating, exposing more active sites. Using laser induced graphene (LIG) as a flexible substrate, a novel BiNPs/COF/LIG electrochemical sensor for Pb²⁺ and Cd²⁺ was developed. The sensor displays high conductivity, large surface area and numerous adsorption sites. A linear relationship was observed between the signal and concentrations of Pb²⁺ and Cd²⁺ from 2.5 to 800 μg/L, with detection limits as low as 0.38 and 0.25 μg/L, respectively.