Using the photo-enhanced barrier effect on electrochemical response for highly sensitive detection of melamine

Three-dimensional CeO2 Nanosheets/CuO nanoflowers p-n heterostructure supported on carbon cloth as electrochemical sensor for sensitive nitrite detection

BACKGROUND

Nitrite is widely used as a food additive, and it is of great significance to realize accurate detection of nitrite for food safety. Electrochemical technique is characterized by simple operation and portability, which enables rapid and accurate detection. The key factors affecting the nitrite detection performance are the electrocatalytic activity and interfacial electron transfer efficiency of the electrode. The electrochemical oxidation of nitrite typically requires high potentials, posing challenges for detection. Therefore, we need to develop a high-performance sensitive electrode to fulfill the need for efficient detection of nitrite. (89) RESULTS: We designed a novel CeO2 nanosheets/CuO nanoflowers p-n heterostructure supported on carbon cloth, which was used to construct an electrochemical sensor for nitrite. The p-CuO NFs/n-CeO2 NSs heterojunction produced charge transfer effects and strong electronic interactions, which contributed to the increase in oxygen vacancies and enhanced the electrocatalytic activity. During electrochemical oxidation of nitrite, the p-n heterojunction achieved more efficient carrier separation, increasing the number of free electrons in the conduction band and facilitating charge transport. The electrode combines CuO nanoflowers with labyrinthine CeO2 nanosheets, significantly enhancing the electrochemically active surface area and availability of active sites, improving electron conduction efficiency and mass transfer efficiency. The CeO2 NSs/CuO NFs/CC showed significantly enhanced current response for the oxidation of nitrite, such as the sensitivity of 11610 μA mM-1cm-2, the linear determination range of 0.1-4000 μM, the LOD of 0.037 μM (S/N = 3). (143) SIGNIFICANCE: This work combines binary metal oxide p-n heterojunction with three-dimensional morphology optimization to design sensitive electrode with enhanced nitrite sensing performance, reduced oxidation potential and improved sensitivity. And the prepared electrode can rapidly and accurately detect nitrite residues in food samples. This work provides a high-performance nitrite electrochemical sensing platform with great practical applications. (54).

Non-enzymatic electrochemical detection of melamine in dairy products by using CuO decorated carbon nanotubes nanocomposites

Melamine, a typical nitrogen enriched organic compound exhibiting great potential in the industrial sector, is exploited as an adulterant to inflate protein levels in dairy products, can pose serious threats to humans and therefore necessitates its swift detection and precise quantification at its first exposure. In this investigation, sensitive and reliable sensor probes were fabricated using CuO nanoparticles and its nanocomposites (NCs) with carbon nanotubes (CNTs), carbon black (CB), and graphene oxide (GO) to promptly quantify melamine in dairy products. The optical, morphological, and structural characteristics of the CuO-CNT NCs were achieved using diverse instrumental techniques including UV-visible spectroscopy, transmission electron microscopy, X- ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy and etc. The fabrication of glassy carbon electrodes (GCE) was accomplished by coating CuO-CNT NCs through a binder (5 % nafion). These sensor probes demonstrated outstanding electrochemical sensor performance with CuO-CNT NCs/Nafion/GCE sensor probe in terms of very low limit of detection (0.27 nM), good linearity range (0.05-0.5 nM), and relatively high sensitivity (93.924 µA µM-1 m-2) for melamine under optimized experimental conditions. Furthermore, the performance of CuO-CNT NCs/Nafion/GCE coated sensor probes was practically validated for the selective melamine detection in the real sample analysis of commercially available milk brands, which revealed significant figures of merit in a very short response time of 10 s. From the results, it was concluded that the current study might be helpful in the development of an efficient commercial sensor based on ultra-sensitive transition metal oxides in the field of health care monitoring, food stuffs in a broader scale as well as food applications.

Using Multistage Energy Barrier of Heterojunctions in Improving Cr(VI) Detection

Detecting heavy metals in seawater is challenging due to the high salinity and complex composition, which cause strong interference. To address this issue, we propose using a multistage energy barrier as an electrochemical driver to generate electrochemical responses that can resist interference. The Ni-based heterojunction foams with different types of barriers were fabricated to detect Cr(VI), and the effects of the energy barriers on the electrochemical response were studied. The single-stage barrier can effectively drive the electrochemical response, and the multistage barrier is even more powerful in improving sensing performance. A prototype Ni/NiO/CeO2/Au/PANI foam with multistage barriers achieved a high sensitivity and recovery rate (93.63-104.79%) in detecting seawater while resisting interference. The use of multistage barriers as a driver to resist electrochemical interference is a promising approach.