Controllable synthesis of three-dimensional nitrogen-doped hierarchical porous carbon and its application in the detection of lead

In this study, gelatin-based microcapsules were first proposed as a carbon source for the synthesis of nitrogen-doped hierarchical porous carbon (N-HPC) via a facile one-pot high-temperature treatment. The morphologies of the microcapsules could be well controlled by adjusting the synthesis parameters; this ensured the repeatability of the calcined products. The as-prepared N-HPC possesses a favorable three-dimensional network structure and hierarchical porous structure. As a promising modified electrode, N-HPC displayed remarkably improved stability and sensitivity for lead ion (Pb2+) detection. Moreover, two factors are responsible for the good analytical performance: (i) the morphologies of the microcapsules are controllable and reproducible; this improves the detection stability; and (ii) the nitrogen atoms in the shells of the microcapsules can efficiently interact with Pb2+; this enhances the detection sensitivity. The influences of various experimental parameters, including the pH value of the supporting electrolyte, deposition potential and deposition time, on the stripping signal of Pb2+ were investigated. The method displayed a wide linear range of the Pb2+ concentration from 7 nM to 7000 nM with the detection limit of 1.44 nM under the optimized conditions. The modified electrode possessed high selectivity, which might be due to the high binding affinity of the NH2− groups to Pb2+. The developed method has been successfully applied to the detection of Pb2+ in actual water samples; this demonstrates that the N-HPC-based electrochemical sensors have prospective applications in the environmental monitoring of Pb2+.