Co₃O₄ nanoparticles (NPs) with an average diameter of about 20 nm were synthesized by using MOFs as a template. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the as-prepared Co₃O₄ NPs. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were used to confirm the structure of the Co₃O₄ NPs. Then the Co₃O₄ NPs were modified on a glassy carbon electrode (GCE) to obtain a non-enzymatic glucose and H₂O₂ sensor. The NPs show electrocatalytic activity toward oxidation of glucose and H₂O₂ in alkaline medium. For glucose detection, the developed sensor shows a short response time (less than 6 s), a high sensitivity of 520.7 μA mM⁻¹ cm⁻², a detection limit of 0.13 μM (S/N = 3), and good selectivity. The high concentration of NaCl does not poison the electrode. Its application for the detection of glucose in a human blood serum sample shows good agreement with the results obtained from the hospital. Furthermore, the proposed sensor was used for the detection of H₂O₂. The results indicate that the detection limit and sensitivity for H₂O₂ are 0.81 μM and 107.4 μA mM⁻¹ cm⁻², respectively. Determination of H₂O₂ concentration in a disinfectant sample by the proposed biosensor also showed satisfactory result. The high sensitivity and low detection limit can be attributed to the excellent electrocatalytic performance of the as-prepared Co₃O₄ NPs. These results demonstrate that the as-prepared Co₃O₄ NPs have great potential applications in the development of sensors for enzyme-free detection of glucose and H₂O₂.

A novel graphene–Au nanoparticles (AuNPs) composite film modified glassy carbon electrode (GCE) was proposed for selective detection of dopamine (DA). The resulting electrode was characterized using transmission electron microscopy, cyclic voltammetry and differential pulse voltammetry. Compared to bare and graphene modified electrodes, this nanocomposite modified electrode not only significantly improved the electrochemical peak potential difference between DA and ascorbic acid (AA), but also noticeably enhanced the current response. The constructed DA sensor showed a wide linear range (5–1000 μM) and a low detection limit (1.86 μM). The graphene–AuNPs composite, which was obtained by assembling AuNPs onto the graphene surface, could provide a promising platform to develop excellent electrochemical sensors for detecting DA.