Biomass derived worm-like nitrogen-doped-carbon framework for trace determination of toxic heavy metal lead (II)

The worm-like nitrogen-doped-carbon framework (WNCF) with abundant edge-plane-like defective sites (EDSs) was synthesized by using natural wax gourd (Benincasa hispida) as the main carbon precursor and milk yielded by Chinese Holstein cattle (Holstein Friesian) as the nitrogen precursor for the first time. The Nafion-dispersed WNCF (Nafion-WNCF) was employed to design a highly sensitive electrochemical sensor for the trace determination of toxic heavy metal lead (II) (Pb²⁺) by the differential pulse anodic stripping voltammetry (DPASV). Some key experimental factors including calcination temperature of WNCF, pH value of the buffer solution, deposition potential, deposition time and the concentration of bismuth (Bi³⁺) were optimized for the stripping analysis of Pb²⁺. Under the optimum experimental condition, Nafion-WNCF modified bismuth film glassy carbon electrode (Nafion-WNCF/BFGCE) exhibits a wide linear range from 0.5 μg L^-1 to 100 μg L^-1 and a low detection limit of 0.2 μg L^-1 (S/N = 3) for detecting Pb²⁺. Especially, Nafion-WNCF/BFGCE was successfully applied to determine Pb²⁺ in tap water and lake water samples. All the results suggest that the WNCF can be considered as a green and low-cost nanomaterial for the precision detection of Pb²⁺ in real samples.