Ultrasensitive and highly reusable electrochemical sensor with ion imprinted nanobiochar

Abstract

A novel electrochemical sensor for the ultrasensitive monitoring of Pb2+ and Cd2+ was developed by fabrication of highly conductive and target selective electrode using ball milling biochar (BBC) featured with high conductivity and rich oxygenic functional groups as the conductive material, and cavities of ion-imprinted polymer as specific binding moieties. The nanosized BBC was synthesized with process of high temperature pyrolysis and rigorous ball milling. The ion imprinted BBC electrode was constructed by in situ electropolymerization of L-Cysteine and template metal ions on the BBC that was modified on glassy carbon, and subsequent removal of templates. The BBC presented great electron transfer ability, and contained increased oxygenic compounds than the mild ball milling prepared one, which attributed to formation of stable and cavity-rich imprinting polymer layer and enhancement of sensing signal. With the anodic dissolved differential pulse voltammetry, the electrode could detect extremely low levels of Pb2+ and Cd2+ with lowest detection limits of 5.86 fM and 0.883 aM, and the linear ranges were 25 fM ~ 1 µM and 0.1 fM ~ 1 µM, respectively. The electrode also presented anti-interference to other irrelevant ions and organic compounds, and could reuse at least seven times without decrease of sensing signal.