Heterostructured ZnO/ZnS core/shell nanowire arrays have been successfully fabricated to serve as photoanode for the dye-sensitized solar cells (DSSCs) by a facile two-step approach, combining hydrothermal deposition and liquid-phase chemical conversion process. The morphology evolution of the ZnS coated on the ZnO nanowires and its effect on the performance of the DSSCs were systematically investigated by varying the reaction time during the chemical conversion process. The results show that the compact ZnS shell can effectively promote the photogenerated electrons transfer from the excited dye molecules to the conduction band of the ZnO, simultaneously suppress the recombination for the injected elelctrons from the dye and the redox electrolyte. As reaction time goes by, the surface of the nanowires becomes coarse because of the newly formed ZnS nanoparticles, which will enhance the dye loading, resulting in increment of the short-circuit current density (J(SC)) . Open-circuit photovoltage decay measurements also show that the electron lifetime (τ(n)) in the ZnO/ZnS core/shell nanostructures can be significantly prolonged because of the lower surface trap density in the ZnO after ZnS coating. For the ZnO/ZnS core/shell nanostructures, the J(SC) and η can reach a maximum of 8.38 mA/cm(2) and 1.92% after 6 h conversion time, corresponding to 12- and 16-fold increments of as-synthesized ZnO, respectively.

Room-temperature (RT) gas sensors based on low-dimensional materials have rapidly received wide attention in various automation control systems and particularly in the Internet of Things (IoT) platforms due to their...

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Laser cleaning of metallic alloys for the purpose of removal of metal oxide layers is based on laser thermal ablation. In laser thermal ablation, the interaction between the laser beam and oxide layer may generate significant thermal effects to induce additional thermal oxidation or even melting a thin layer of the underlying surface. The change of surface oxide status may subsequently affect corrosion behavior of the metallic alloys. In this work, the effects of laser cleaning on corrosion behavior of hot-rolled AA5083-O aluminum alloy were investigated using electrochemical impedance spectroscopy. The results showed that the laser-cleaned surfaces exhibited higher corrosion resistance in 3.5 wt. % NaCl solution than the as-received alloy, with a significant increase in impedance and reduction in capacitance. The corrosion behavior was correlated to the change of surface oxide status measured by glow discharge optical emission spectrometry, x-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. It was concluded that the laser cleaning removed the original, less protective oxide layer consisting of a discontinuous MgO/MgAl2O4 outer layer (∼20 nm) and MgO/MgAl2O4 particles dispersed inner layer (∼300 nm) on the as-received surface but resulted in the formation of more protective oxide layer containing mainly Al2O3 and MgO, which were responsible for the improvement of the corrosion performance. The laser fluence played an important role in determining the thickness of the newly formed oxide layers that subsequently affected the corrosion performance of laser-cleaned alloy.

Reversible H2 gas sensing at room temperature has been highly desirable given the booming of the Internet of Things (IoT), zero-emission vehicles, and fuel cell technologies. Conventional metal oxide-based semiconducting gas sensors have been considered as suitable candidates given their low-cost, high sensitivity, and long stability. However, the dominant sensing mechanism is based on the chemisorption of gas molecules which requires elevated temperatures to activate the catalytic reaction of target gas molecules with chemisorbed O, leaving the drawbacks of high-power consumption and poor selectivity. In this work, we introduce an alternative candidate of cobalt oxysulfide derived from the calcination of self-assembled cobalt sulfide micro-cages. It is found that the majority of S atoms are replaced by O in cobalt oxysulfide, transforming the crystal structure to tetragonal coordination and slightly expanding the optical bandgap energy. The H2 gas sensing performances of cobalt oxysulfide are fully reversible at room temperature, demonstrating peculiar p-type gas responses with a magnitude of 15% for 1% H2 and a high degree of selectivity over CH4, NO2, and CO2. Such excellent performances are possibly ascribed to the physisorption dominating the gas–matter interaction. This work demonstrates the great potentials of transition metal oxysulfide compounds for room-temperature fully reversible gas sensing.