Conventional enzyme-based glucose sensors have good selectivity and sensing performance, but the disadvantages of the enzyme itself (enzyme activity is susceptible to pH and temperature) lead to a limited number of uses and result in high costs. Therefore, photoelectrochemical enzyme-free glucose sensors have attracted research interest in recent years. In this work, the TiO2/CuO heterojunction was constructed and photoelectrochemical enzyme-free glucose sensing was realized. The sensing sensitivity of the TiO2/CuO heterojunction photoelectrode prepared by magnetron sputtering and thermal annealing process was 864 μAμM-1 cm-2 in the range of 1–9 mM with a detection limit of 58.6 μM at 0.2 V, exhibiting satisfactory stability as well as interference resistance. This better sensing performance mainly comes from: 1) the absorption of photogenerated carriers generated from sunlight by TiO2 films, which participate in glucose redox; 2) the conversion of the metal valence state (Cu2+/Cu3+) of the P-type semiconductor CuO under alkaline conditions can promote glucose redox; 3) the heterojunction formed by CuO and TiO2 reducing the compounding of photogenerated carriers thus improving the photoelectric conversion efficiency. The heterojunction formed by CuO and TiO2 greatly facilitates the surface carrier transfer of glucose oxidation reaction. This work provides a new way for enzyme-free glucose sensing and promotes the development of glucose detection technology.
Photoelectrochemical (PEC) sensors have the advantages of high sensitivity, low background noise, and fast response time, and are suitable for environmental monitoring, biomedical, and chemical industries. In this work, a photocathode whose photoresponses weaken with increasing concentration of the substance is proposed and used for Cr(VI) sensing, and a wide concentration range (0.04−16 µM) for Cr(VI) can be detected by just using one NiO film, with a sensing sensitivity of 0.69 lgC µAµM-1 cm-2 (where C is the concentration) and a low detection limit of 0.01 µM. The successful detection of Cr(VI) was achieved through the signal-weakening photoelectrochemical responses, as evidenced by the decrease in the photocathode signal with increasing Cr(VI) concentration. This can be attributed to the steric hindrance effect caused by the in-situ formation of Cr(OH)3 precipitates. Our proposed scheme can be successfully used for the monitoring of Cr(VI) in drinking water, as the world health organization requirement of 0.96 µM is included in the linear detection range.
Constructing novel hybrid nanostructure has become an effective strategy to enhance the performance of photoelectrochemical (PEC) biosensors. However, most of the H2O2-sensing photoelectrodes require enzyme modification, which limits the working environment and sensing performance. Herein, the burr-like CuO nanostructures are modified on the entire surfaces of the ordered Si nanowires (SiNWs) by using a combination of magnetron sputtering and hydrothermal growth. The optimized CuO@SiNWs heterojunction with a core-shell structure enables enzyme-free PEC detection of H2O2, achieving a sensitivity of 227.76 μAmM-1cm-2 in the concentration range of 0–588 mM and a detection limit of 7.14 μM (Signal/Noise=3). The excellent sensing performance of the CuO@SiNWs is attributed to the large specific surface area provided by SiNWs and the CuO possess desired H2O2-catalytic activity while providing a great number of active sites. In addition, the CuO@SiNWs demonstrates satisfactory optical absorption. This work demonstrates that enzyme-free and highly sensitive H2O2 detection can be achieved by hybrid nanostructure, providing an alternative route to H2O2 sensing.
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