We report the structure, optical, and gas-sensing properties of ZnO nanorods with different diameters. Vertically well-aligned homogeneous nanorods were grown along the c-axis orientation. The shift of Raman scattering E 2 (high) mode and photoluminescence (PL) spectra were used to study the dependences of nanorod diameters on the stress and oxygen vacancy. Gas sensors were prepared and tested for the detection of C 2 H 5 OH and H 2 S (100 ppm) in air. It was found that the thin nanorods have a significantly better sensing performance than the thick nanorods. We provide a possible explanation from the aspect of the sensing mechanism of the surface reaction process.

In this letter, we present a gas sensor using a single ZnO nanowire as a sensing unit. This ZnO nanowire-based sensor has quick and high sensitive response to H2S in air at room temperature. It has also been found that the gas sensitivity of the ZnO nanowires could be modulated and enhanced by He+ implantation at an appropriate dose. A possible explanation is given based on the modulation model of the depletion layer.

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A stabilized diesel-methanol blend was realized and a study on the performance and emissions of the diesel-methanol blend was carried out in a compression ignition engine. The study showed that the engine thermal efficiency increases and the diesel equivalent b.s.f.c. decreases with increase in the oxygen mass fraction (or methanol mass fraction) of the diesel-methanol blends due to an increased fraction of premixed combustion phase, oxygen enrichment and improvement in the diffusive combustion phase. Further increase in the fuel delivery advance angle will achieve a better engine thermal efficiency when the diesel engine is operated using the diesel-methanol fuel blends. A marked reduction in the exhaust CO and smoke can be achieved when operating with the diesel-methanol blend. There is not a large variation in the exhaust hydrocarbon with the addition of methanol in diesel fuel. NOx increases with increase in the mass of methanol added; methanol addition to diesel fuel was found to have a strong influence on the NOx concentration at high engine loads rather than at low engine loads, and a flat NOx-smoke trade-offcurve exists when operating with the diesel-methanol fuel blends.

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Metal−organic frameworks (MOF) or their derivatives have attracted much attention in recent years due to exciting properties such as high specific surface area, adjustable pore size, and easy functionalization, which makes them have unique advantages in the fields of catalysis, energy storage, optoelectronics, and so on. However, the study of them in the fields of nonlinear optics and ultrafast photonics is still in its early stage. Here, by annealing the MOF template, porous MOF-derived CuO octahedra are prepared and applied to the above fields. Experiments show that CuO octahedra possess an excellent nonlinear optical absorption capacity in the near-infrared band. When it is used as a saturable absorber (SA) to the fiber lasers, high order harmonic soliton molecules with a repetition frequency up to 238 MHz can be obtained that make sense for optical frequency combs and optical communication. Besides, the dynamic evolution of the harmonic soliton molecule is explored. This work pioneers the application of MOF-derived metal oxide polyhedra as SAs in fiber lasers and expands the application fields of MOF-based materials. Moreover, this kind of emerging microstructured polyhedral SA, prepared by the new method, provides researchers with a new choice beyond quantum dots, nanoparticles, and 2D nanosheets/nanofilms.

A low-cost and catalyst-free two-step approach has been developed to produce ZnO nanotubes (ZNTs) by simple thermal oxidation of Zn nanowires under 20 Pa at a low temperature of 400 °C. The growth mechanism of ZNTs is discussed in detail. The formation of these tubular structures is closely linked to the oxidation pressure and temperature, which involves a process consisting of the deposition of Zn nanowires, cracking of the Zn nanowires and sublimation of the Zn cores, and subsequent oxidation to ZNTs. The optical properties were studied by using Raman and photoluminescence spectra, where a strong green emission related to the single ionized oxygen vacancy appears. The photocatalytic activity measurement indicates an enhanced photocatalytic activity of the prepared ZNTs due to their high surface-to-volume ratios and abundant oxygen vacancies near the surfaces of the ZNTs. This type of high surface area structural ZNTs could find promising potential for optoelectronic and environmental applications.

To avoid carcinogenicity, formaldehyde gas, currently being only detected at higher operating temperatures, should be selectively detected in time with ppb concentration sensitivity in a room-temperature indoor environment. This is achieved in this work through introducing oxygen vacancies and Pt clusters on the surface of In2O3 to reduce the optimal operating temperature from 120 to 40 °C. Previous studies have shown that only water participates in the competitive adsorption on the sensor surface. Here, we experimentally confirm that the adsorbed water on the fabricated sensor surface is consumed via a chemical reaction due to the strong interaction between the oxygen vacancies and Pt clusters. Therefore, the long-term stability of formaldehyde gas detection is improved. The results of theoretical calculations in this work reveal that the excellent formaldehyde gas detection of Pt/In2O3–x originates from the electron enrichment due to the surface oxygen vacancies and the molecular adsorption and activation ability of Pt clusters on the surface. The developed Pt/In2O3–x sensor has potential use in the ultraefficient, low-temperature, highly sensitive, and stable detection of indoor formaldehyde at an operating temperature as low as room temperature.