Ultrasensitive and highly reusable electrochemical sensor with ion imprinted nanobiochar

A novel electrochemical sensor for the ultrasensitive monitoring of Pb 2+ and Cd 2+ 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 Pb 2+ and Cd 2+ 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. • Highly conductive nanosize BBC with rich oxygenic functional group and large pore was prepared. • Ion imprinted BBC electrode can specifically bind target metal ions with enhanced response signal. • The electrode featured of rich cavities could detect extremely low leveled target with wide linear range. • It was highly selective and could reuse over seven times without signal decrease.