Imidazoline derivative templated synthesis of broccoli-like Bi2S3 and its electrocatalysis towards the direct electrochemistry of hemoglobin

A broccoli-like bismuth sulfide (bBi 2 S 3 ) was synthesized via a solvothermal method using a self-made imidazoline derivative of 2-undecyl-1-dithioureido-ethyl-imidazoline as the soft template. The morphology and chemical constitution of the product were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Electrochemical characterization experiments show that the bBi 2 S 3 has the higher specific surface area and standard heterogeneous electron transfer rate constant than the rod-like Bi 2 S 3 (rBi 2 S 3 ). Hemoglobin (Hb) was then chosen as a protein model to investigate the electrocatalytic property of the synthesized bBi 2 S 3 . The results show that Hb entrapped in the composite film of chitosan and bBi 2 S 3 displays an excellent direct electrochemistry , and retains its biocatalytic activity toward the electro-reduction of hydrogen peroxide. The current response in the amperometry shows a linear response to H 2 O 2 concentrations in the range from 0.4 to 4.8   µM with high sensitivity (444   µA   mM −1 ) and low detection limit (0.096   µM). The Michaelis–Menten constant ( K M app ) of the fabricated bioelectrode for H 2 O 2 was determined as low as 1   µM. These results demonstrate that the synthesized bBi 2 S 3 offers a new path for the immobilization of redox-active protein and the construction of the third-generation biosensors.