RESUMEN
This study focused on enhancing the sensitivity and selectivity to detect melamine by utilizing a photoelectrochemical method. This was achieved by combining a melamine-imprinted polymer with a CuO/g-C3N4 nanocomposite, which was synthesized through chemical precipitation and calcination. The resulting nanocomposite exhibits improved carrier mobility and photoelectrochemical properties. A molecularly imprinted receptor for selective detection was created through bulk polymerization with methacrylic acid and a melamine template. The characterization of the nanocomposite was performed using X-ray photoelectron spectroscopy for the chemical oxidation state, X-ray diffraction patterns for the crystalline structure, and ultraviolet/visible/near-infrared spectroscopy for optical properties. The CuO/g-C3N4 nanocomposite exhibits photoactivity under visible light. The modified electrode, incorporating the CuO/g-C3N4 nanocomposite and melamine-imprinted polymer, demonstrates a linear detection range of 2.5 to 50 nM, a sensitivity of 4.172 nA/nM for melamine, and a low detection limit of 0.42 nM. It shows good reproducibility and high selectivity to melamine, proving effective against interferences and real samples, showcasing the benefits of the molecularly imprinted polymer.
RESUMEN
Melamine contamination in food and beverages affects short- and long-term health. In this work, enhanced sensitivity and selectivity in photoelectrochemical determination for melamine detection was achieved using copper(ii) oxide (CuO) combined with a molecularly imprinted polymer (MIP). A CuO nanomaterial was used to achieve MIP surface modification via co-precipitation synthesis. An MIP film was deposited by polymerizing the methacrylic acid monomer and a melamine template. The properties of the CuO nanomaterials, such as the surface morphology, chemical oxidation state, and crystalline structure, were characterized using field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction patterns (XRD), respectively. The diffuse reflection spectroscopy technique was applied to evaluate the optical properties of the CuO nanoparticles. The results indicated that the synthesized CuO nanomaterials had a monoclinic structure with an optical bandgap of 1.49 eV, which corresponds to absorbance in the visible light region. CPE electrodes with surface-modified CuO/MIP were measured using the photoelectrochemical techniques of cyclic voltammetry, differential pulse voltammetry (DPV), and amperometry. The modified CuO/MIP electrode for melamine detection in 7.4 pH PBS buffer solution exhibited a high sensitivity of 0.332 nA nM-1, with a linear range of 5.0-75.0 nM and a limit of detection of 2.45 nM. Moreover, real samples of various kinds of milk were applied to evaluate the sensing response of the prepared CuO/MIP electrode. The modified CuO/MIP electrodes could be reused seven times with good reproducibility and high selectivity for melamine detection.
