A novel tantalum pentoxide nanoparticle-electrochemically reduced graphene oxide nanocomposite-modified glassy carbon electrode (Ta₂O₅-ErGO/GCE) was developed for the detection of oxytetracycline in milk. The composition, structure and morphology of GO, Ta₂O₅, and Ta₂O₅-ErGO were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Oxytetracycline electrochemical behavior on the bare GCE, GO/GCE, ErGO/GCE, and Ta₂O₅-ErGO/GCE was studied by cyclic voltammetry. The voltammetric conditions (including scan rate, pH, deposition potential, and deposition time) were systematically optimized. With the spacious electrochemical active area, the Ta₂O₅-ErGO/GCE showed a great magnification of the oxidation signal of oxytetracycline, while that of the other electrodes (GCE, GO/GCE, ErGO/GCE) could not reach the same level. Under the optimum conditions, the currents were proportional to the oxytetracycline concentration in the range from 0.2 to 10 μM, and a low detection limit of 0.095 μM (S/N = 3) was detectable. Moreover, the proposed Ta₂O₅-ErGO/GCE performed practically with satisfactory results. The preparation of Ta₂O₅-ErGO/GCE in the current work provides a minor outlook of detecting trace oxytetracycline in milk.

In this paper, the preparation, characterization, and electrochemical application of Cu₂O nanoparticles and an electrochemical reduced graphene oxide nanohybrid modified glassy carbon electrode (denoted as Cu₂O NPs‒ERGO/GCE) are described. This modified electrode was used as an electrochemical sensor for the catalytic oxidation of rhodamine B (RhB), and it exhibited an excellent electrochemical performance for RhB. The oxidation potential of RhB was decreased greatly, and the sensitivity to detect RhB was improved significantly. Under optimum conditions, a linear dynamic range of 0.01–20.0 μM and a low detection limit of 0.006 μM were obtained with the Cu₂O NPs‒ERGO/GCE by using second‒order derivative linear sweep voltammetry. In addition, the selectivity of the prepared modified electrode was analyzed for the determination of RhB. The practical application of this sensor was investigated for the determination of RhB in food samples, and satisfactory results were obtained.