Preparation of Co3O4 conical nanotube and its application in calcium ion biosensor

Calcium ion (Ca 2+ ) is an important ion involved in body life activities, and its content detection in biomedical field owns great significance. In this study, we fabricated Co 3 O 4 conical nanotube on F-doped tin oxide (FTO) substrate for detecting Ca 2+ . Co 3 O 4 is fabricated through a hydrothermal method and demonstrates a regular hexagon structure, with a length of 5–10 μm and wall thickness of 30 nm. The structure and morphology of Co 3 O 4 were characterized by X-ray diffraction (XRD), scanning electron microscope, and transmission electron microscopy, respectively. In addition, then, we used electrochemical technique to characterize the Ca 2+ concentration in the simulated body fluid. The detection of Ca 2+ is originated from the electrochemical reaction of hydrogen peroxide using Co 3 O 4 as a catalyst, in which Ca 2+ plays a significant role for accelerating the decomposition of hydrogen peroxide catalytic performance. By monitoring the electron transfer signals changes during the electrochemical reaction, we can quickly quantify the Ca 2+ concentrations. It is found that this Ca 2+ sensor owns a wide detection range (0.1–1.1 mM), a low detection limit (3.767 μM), and good anti-interference ability.