Gas sensing properties of ZnO nanorods prepared by hydrothermal method

ZnO nanorods are prepared by a hydrothermal process with cetyltrimethylammonium bromide (CTAB) and zinc powder at 182°C. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The gas sensing properties of the materials have been investigated. The results indicate that the as-prepared ZnO nanorods are uniform with diameters of 40–80 nm and lengths about 1 μm, the relatively high sensitivity and stability of these sensors made from ZnO nanorods demonstrate the potential for developing a new class of stable and very sensitive sensors.     

Humidity sensing behaviors of nanocrystalline Al-doped ZnO thin films prepared by sol–gel process

Nanocrystalline Al-doped ZnO(AZO) thin films prepared by sol–gel method were used for studying the variation of resistance with humidity. The particle size of the films exhibits nanometer order with zincite structure and the thickness of the films increases linearly with the number of coatings. The AZO film coated five times and annealed at 500 °C exhibits the highest sensitivity for the humidity, which shows three order change in the resistance during the relative humidity variation from 20 to 90%. It is considered that the high humidity sensitivity is due to proton hopping between water molecules adsorbed on the film surfaces with capillary nanopores.     

Structure and gas sensing properties of nanocrystalline Fe-doped ZnO films prepared by spin coating method

Nanocrystalline Fe-doped ZnO films were obtained by spin coating, using zinc acetate and iron acetate as starting materials and N,N-dimethylformamide as solvent. Characteristic XRD patterns indicate that the films under study are single phase with the ZnO-like wurtzite structure. There are not any secondary phases and Fe²⁺ as well as Fe³⁺ substitutes for Zn²⁺ of ZnO host. Atomic force microscopy analysis revealed that the studied films are characterized by high-density columnar structure and the incorporation of Fe atoms into the ZnO lattice modified the surface morphology. The sensitivity, at three different gases, was investigated and it was observed that acetone is the test gas that produces the most significant changes in the electrical resistance of all studied samples. Experimental results indicate that the optimum operating temperature increases for Fe-doped ZnO films by comparison with the undoped one. Also, the values of sensitivity were found to depend on the dopant concentration in ZnO films.     

Preparation and gas sensing properties of the nutlike ZnO microcrystals via a simple hydrothermal route

Large-scale uniform nutlike ZnO microcrystals are successfully synthesized via a facile hydrothermal process at low temperature (95 °C). The structure and morphology of the ZnO products are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The results reveal that the as-prepared ZnO products have average length of 2.2 µm and diameter of 1.8 µm, possessing a single crystal wurtzite structure. The possible formation mechanism of nutlike microcrystals is proposed. The samples exhibit excellent ethanol sensing properties at the operating temperature of 250 °C detecting ethanol as low as 1 ppm.     

Photoluminescence of nanocrystalline SrMgF4 prepared by a solution chemical route

SrMgF₄ was prepared by precipitation in aqueous solution. Alkaline earth metal acetates and ammonium fluoride were used as precursors. After drying and annealing the samples at different temperatures and times, single phase SrMgF₄ was obtained. By varying the annealing conditions, the mean crystallite size could be adjusted. Furthermore, the thermally treated samples displayed UV-excited intensive broad band luminescence in the visible region. The emissions colour and intensity can be adjusted by the tempering conditions. X-Ray diffraction, TEM-microscopy, fluorescence and IR-spectroscopy were used for analysis.     

A simple route to prepare nanocrystalline titanium carbonitride

Nanocrystalline titanium carbonitride, TiC_0.7N_0.3, has been synthesized directly by a simple reaction route of TiCl₄ and C₃N₃C1₃ using sodium as the reductant at 600°C. The composition of the powders has been investigated by X-ray powder diffraction. Transmission electron microscopy image reveals that the average size of the obtained particles is about 30 nm.     

热氧化法制备透明超疏水ZnO薄膜

高透明性的无机超疏水薄膜材料具有广阔的应用前景，采用磁控溅射法制备出表面具有纳米结构的金属Zn前驱体薄膜，并利用在低气压5Pa，温度350℃热氧化方法对其采取了处理，获得了接触角为151°，可见光透过率达80％以上的超疏水ZnO薄膜。SEM表明薄膜由100nm短棒状的ZnO堆积而成，通过XRD，IR的测量与分析，进一步讨论了沉积条件及热氧化处理对超疏水透明ZnO薄膜形成机理。     

水热合成法制备杯状氧化锌微晶及其光学性质研究

以Zn(CH3COO)2·2H2O为源反应物,采用水热合成反应法成功地制备了杯状的氧化锌微晶粉体材料.X射线衍射(XRD)谱的结果表明获得了典型的六方结构晶体.扫描电子显微镜(SEM)照片观测到杯状的氧化锌微晶,并且单个微晶互相结合形成对称结构.实验发现,水热时间影响着晶体的形貌,对其结构变化机制进行了探讨.同时,通过...     

Effect of aerosol carriers on ultrasonically prepared nanocrystalline ZnO powders

Nanocrystalline ZnO powders were synthesized using ultrasonic spraying and decomposition technique. The compressed air and pure oxygen were used as aerosol carriers. Effect of aerosol carriers on ultrasonically atomized nanocrystalline ZnO powders was studied. The powders were characterized using X-ray diffraction, transmission electron microscopy (TEM), electron diffraction, absorption spectroscopy and photoluminescence. The influence of air and oxygen on crystallite morphology was studied using TEM. It was confirmed from TEM analysis that the crystallites were nearly spherical in powder prepared in the presence of compressed air. In the presence of pure oxygen, the crystallites could acquire regular hexagonal shape. Complete hexagonal shapes may be due to sufficient (100%) supply of pure oxygen during the process of formation of ZnO nanocrystallite. The powder with regular shaped crystallites could be highly pure and also stoichiometric in nature. Pure oxygen could therefore be more advantageous as carrier than air for production of nanocrystalline ZnO powder. The effect of aerosol carriers (compressed air and pure oxygen) on crystallite morphology of nanocrystalline ZnO powders is reported in this article.     

简单醇热法制备ZnO纳米棒及其抗菌性能研究

通过Zn(NO3)2.6H2O和NaOH的醇溶液制备ZnO,利用XRD和TEM对产物进行表征,产物为具有较高的结晶度和纯度的ZnO纳米棒,直径约为30nm,长度约为130～500nm。取市售ZnO和产物,采用抑菌圈法对3种常见致病菌作药物敏感试验,并测定了产物对金黄色葡萄球菌的最小杀菌浓度(MBC)。结果表明,产物与市售ZnO试剂均对大肠杆菌不敏感,对金黄色葡萄球菌和白色念珠菌有不同程度的敏感,且产物比市售试剂抑菌效果更为明显,产物对金黄色葡萄球菌的最小杀菌浓度(MBC)为1.5%。     

大气开放式MOCVD方法制备ZnO薄膜的气敏特性研究

利用大气开放式MOCVD在氧化铝基片上沉积ZnO薄膜，研究了沉积工艺参数对薄膜形貌的影响，结果表明基片温度对ZnO薄膜的晶体形貌有显著的影响，在一定的条件下能够沉积出具有高比表面积花瓣片层结构的ZnO薄膜。以酒精蒸气为例，研究了ZnO薄膜对碳氢有机化合物气体的气敏特性，结果表明结晶度高且晶粒细小、比表面积高的薄膜具有较好的气敏特性。     

Growth and comparison of different morphologic ZnO nanorod arrays by a simple aqueous solution route

A simple aqueous solution route has been successfully employed to prepare large-scale arrays of ZnO nanorods on the zinc foil without the assistance of any template, oxidant or coating of metal oxide layers. It is found that the growth of ZnO nanorod arrays with different densities, diameters and morphologies is dependent on the ammonia concentration and zinc precursor. The different morphologies of the ZnO nanostructures attained with or without adding Zn²⁺-contained salt in the alkaline solution are compared in the paper. The possible growth mechanism concerning the growth of the different ZnO nanocrystal morphologies is also discussed.     

Growth of ZnO nanoparticles from nanowhisker precursor with a simple solvothermal route

Methods of preparing nanoparticles have long been a topic experiencing extensive investigation. Among those methods developed, using template or polymer and surfactant as capping reagents were often effective. However, obtaining nanoparticles in high amounts and high purity still remains an unresolved challenge. Here, a simple two-step solvothermal method without using any surfactant or coating reactant to prepare ZnO nanoparticles with high purity in large scale was developed. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the as-prepared ZnO nanoparticles, and the formation process of the nanoparticles was discussed finally.     

Shape and size control of ZnO nanostructures via a simple solution route

ZnO nanostructures with different morphologies were synthesized by condensing the Zn(OH)4(2-) precursors under hydrothermal conditions in the presence of a surfactant, cetyltrimethylammonium bromide (CTAB). Shape and size control of ZnO nanostructures was achieved by relatively simple variations of molar ratio of CTAB to Zn(OH)4(2-). With a higher molar ratio, ZnO nanotubes were obtained, whereas with a lower molar ratio, ZnO nanorods were formed; furthermore, with a moderate w value, the coexistence of ZnO nanorods and nanotubes was also observed. The photoluminescence of ZnO nanorods and nanotubes was also investigated.     

Ethanol sensing properties of porous ZnO spheres via hydrothermal route

ZnO spheres composed of porous flakes were prepared by template-free, economical hydrothermal method combined with heat treatment. The high-density pores with the size in tens of nanometers were found distributed through each piece of the flake. The sensor based on porous ZnO spheres showed improved ethanol response compared to that based on commercial ZnO powders. ZnO spheres sensor showed obvious response to 2 ppm ethanol at the operation temperature of 280 °C, with the corresponding response value of 2.8 and the response and recovery times of 10 and 15 s, respectively. The response of the sensor increased linearly with the concentration of ethanol in the range of 2–500 ppm. The good sensing performance of the ZnO sphere sensor to ethanol gas indicated that the ZnO sphere could be a promising candidate as the building block for highly sensitive and reliable gas sensor.     

Solvothermal synthesis of nanocrystalline ZnO with excellent photocatalytic performance

We reported a facile way to synthesize nanocrystalline ZnO particles with excellent photocatalytic performance. Their microstructures and optical properties were characterized by X-ray diffraction, field emission scanning electron, transmission electron microscopy, photoluminescence spectra and ultraviolet–visible (UV–Vis) spectra. Photocatalytic tests showed the as-prepared ZnO particles had a good activity for photodegradation of organic dyes under UV–Vis light irradiation, which was comparable with that of P25 TiO₂, a commercial standard photocatalyst. Furthermore, the sample could be easily sedimentary from the reaction system, which was favorable for the separation and reuse. Meanwhile, the photocatalytic performance of the samples exhibited no obvious reduction in the activity after five recycles of photodegradation, demonstrating its superior reusability. We attributed the superior performance to the efficient synergistic effect resulted from the small nano size, as well as the appropriate oxygen vacancies in the ZnO lattice. Our work might be promising for the application of ZnO-based photocatalysts due to its low cost, easy process, and good performance.     

溶剂热法制备铝掺杂纳米ZnO及其气敏性能

采用溶剂热法合成了铝掺杂的纳米ZnO气敏材料,运用XRD和BET等手段对产物进行了表征并进行了相应的气敏性能测试.结果表明,掺杂1.5%Al后的ZnO比表面最大,粒径最小;材料对乙醛、90#汽油、90#乙醇汽油、硫化氢、二氧化氮响应较高.掺杂量为1.5%Al的元件对90#汽油在浓度为50ppm时灵敏度接近120.