Ultraviolet (UV) photodetectors (PDs) are characterized by wide wavelength selectivity and strong anti-interference capability. The focus of research is not only limited to the adjustment of the structure composition, but it also delves deeper into its working mechanism and performance optimization. In this study, a heterojunction self-powered photodetector with a unique honeycomb structure was successfully constructed by combining the advantages of two semiconductor materials, zinc oxide (ZnO) and nickel oxide (NiO), using magnetron sputtering and hydrothermal synthesis. The detector has high responsivity, high detectivity and favorable spectral selectivity under UV irradiation. The nearly 10-fold increase in responsivity and detectivity of the detector with the introduction of the honeycomb structure under zero-bias conditions is attributed to the macroporous structure of the ZnO honeycomb nano-mesh, which increases the surface active sites and facilitates the enhancement of light trapping. This study provides significant value to the field of UV detection by improving detector performance through structural optimization.

The slight but cumulative influence of impurity gases in air poses a great threat to the long-term stability of room-temperature gas sensors. Room-temperature hydrogen-sensitive Pt–SnO₂ composite nanoceramics of 5 wt% Pt were prepared through pressing and sintering. The response of a sample was over 10,000 after being exposed to 500 ppm H₂S–20% O₂–N₂ at room temperature, and the room-temperature hydrogen sensing capacity was seriously degraded even for samples that had aged dozens of days since H₂S exposure. Mild heat treatments such as 160 °C for 10 min were found able to fully activate those H₂S-exposed samples. As the peak of S 2p electron was clearly detected in H₂S-exposed samples, it was proposed that for room-temperature hydrogen-sensitive Pt–SnO₂ composite nanoceramics, H₂S exposure induced degradation results from the poisoning of Pt by H₂S deposited on it, which can be removed through a mild heat treatment. Periodic mild heat treatment should be a convenient and effective measure for room-temperature metal oxide gas sensors to achieve long-term stability through preventing the accumulation of impurity gases in air deposited on them.

Soluble noble metal salts are widely used for loading noble metals as nano-catalysts in many applications. In this paper, Pt-SnO₂ composite nanoceramics were prepared from SnO₂ nanoparticles and H₂PtCl₆ using two Pt loading methods separately: for the solution reduction method, a H₂PtCl₆ solution was added to a suspension of SnO₂ and zinc powder to form Pt on SnO₂ nanoparticles, and for the impregnation method, Pt was formed from H₂PtCl₆ in the course of sintering. Although a series of samples prepared using both Pt loading methods showed a solid response to H₂ at room temperature, the ones prepared using the solution reduction method exhibited much better room-temperature hydrogen-sensing characteristics. For two samples of 0.5 wt% Pt and sintered at 825 °C, the response value for the sample prepared using the solution reduction method was 9700 to 1% H₂–20% O₂-N₂, which was much larger than the value of 145 for the sample prepared using the impregnation method. Samples prepared using the two Pt loading methods have similar microstructures characterized via XRD, FESEM, EDS, TEM, and HRTEM. However, the residual chlorine content in those using the impregnation method was higher than those using the solution reduction method according to the analysis. It is proposed that the striking difference in room-temperature hydrogen sensing characteristics among samples prepared using these two different Pt loading methods separately resulted from their different chlorine removal processes. This study demonstrates the importance of a proper method for loading noble metals from their soluble salts as nano-catalysts in many applications.

Soluble noble metal salts are widely used for loading noble metals as nano-catalysts in many applications. In this paper, Pt-SnO2 composite nanoceramics were prepared from SnO2 nanoparticles and H2PtCl6 using two Pt-loading methods separately: For the solution reduction method, the H2PtCl6 solution was added to a suspension of SnO2 and zinc powder to form Pt on SnO2 nanoparticles; and for the impregnation method, Pt was formed from H2PtCl6 in the course of sintering. Although a series of samples prepared using both Pt loading methods showed a strong response to H2 at room temperature, the ones prepared using the solution reduction method exhibited much better room temperature hydrogen sensing characteristics. For two samples of 0.5 wt% Pt and sintered at 825°C, the response value for the sample prepared using the solution reduction method was 5300 to 1% H2-20% O2-N2, which was much larger than that of 150 for the sample prepared using the impregnation method. Samples prepared using the two Pt loading methods have similar microstructures as characterized by XRD, FESEM, EDS, TEM, and HRTEM. However, the residual chlorine content in those using the impregnation method was found to be higher than that using the solution reduction method through analysis. It is proposed that the striking difference in the room temperature hydrogen sensing characteristics among samples prepared using these two different Pt loading methods separately resulted from their different chlorine removal process. This study demonstrates the importance of a proper method in loading noble metals from their soluble salts as nano-catalysts in many applications.