Highly active catalyst using zeolitic imidazolate framework derived nano-polyhedron for the electro-oxidation of l-cysteine and amperometric sensing

Herein, N-doped porous carbon nano-polyhedron embedded with Co3O4 (Co3O4-NPCN) was reported for the electro-catalytic oxidation and amperometric detection of l-cysteine. Co3O4-NPCN was synthesized by the two-step redox calcination of zeolitic imidazolate framework (ZIF). Surface morphology characterization revealed that Co3O4-NPCN displayed a uniform size and rhombic dodecahedral shape. Structure and composition analysis found that Co3O4-NPCN was a N-doped carbon polyhedral matrix with hollow and porous structure, and Co3O4 nano-spheres were evenly distributed into the polyhedral matrix. Due to the hollow and porous structure, N-doped carbon matrix and embedded Co3O4 nano-spheres, Co3O4-NPCN performed a remarkable electro-catalysis towards the oxidation of l-cysteine at a very low potential of 0.10 V. A diffusion-controlled l-cysteine oxidation process was observed at Co3O4-NPCN prepared electrode. Accordingly, amperometric method was established for l-cysteine detection with a very fast current response in 2 s, wide linear range of 0.05 μM- 5.2 mM and low detection limit of 6.9 nM. Besides, notable selectivity, repeatability, reproducibility and long-term stability were also achieved. Moreover, Co3O4-NPCN sensor was successfully applied to the l-cysteine detection in human serum samples indicating the practical application of the as-developed sensor.