Preparation and characterization of ZnO porous plates

This article presents two main steps to prepare zinc oxide porous plates. Firstly, the precursor zinc hydroxide chloride hydrate (Zn₅(OH)₈Cl₂·H₂O) was synthesized by ZnCl₂ and ethylenediamine ((CH₂NH₂)₂). Secondly, the precursor was put into a furnace and annealed at 500 °C. And then the zinc oxide porous plates were successfully obtained. The crystal structures and the microstructures of the precursor and the final product were analyzed and compared by XRD, SEM and TEM. The specific surface area and gas adsorption isotherm of the final product were tested by Brunauer-Emmett-Teller equipment.     

Preparation and gas-sensing property of ZnO nanorod-bundle thin films

ZnO nanorod-bundle thin films have been synthesized by a simple self-assembly method with the aid of F₁₂₇ (EO₁₀₆-PO₇₀-EO₁₀₆) triblock copolymer. Their morphologies and crystal structures were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM). SEM results showed that films were composed of a lot of bundles, which comprised nanorods with the diameter of about 10 nm. The possible formation mechanism of ZnO nanorod-bundle structures is proposed. Gas-sensing property of thin films, to alcohol, was also detected. It was also found that the sensitivity, to 100 ppm alcohol, of ZnO nanorod-bundle thin films was higher than that of ZnO nanoparticle thin films. The results showed that the triblock copolymer, served as the surfactants, could effectively control the morphologies and the aspect ratio of nano-ZnO, and then improve its gas-sensing property.     

Synthesis and characterization of ZnO nanoparticles prepared in gelatin media

Zinc oxide nanoparticles (ZnO-NPs) were synthesized via the sol-gel method in gelatin media. Long-chain gelatin compounds were utilized to terminate the growth of ZnO-NPs and to stabilize them. The ZnO-NPs were characterized by a number of techniques, such as X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), and high-magnification transmission electron microscopy (TEM). The ZnO-NPs calcined at different temperatures exhibited a hexagonal (wurtzite) structure with sizes from 30 to 60 nm. The influence of the calcination temperature on the morphology of ZnO-NPs was also investigated. The results showed that gelatin is an interesting material that can be used as a stabilizer in the sol-gel technique for preparing small ZnO-NPs.     

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 nanowires on a patterned Au substrate

ZnO nanowires were site-selectively deposited on the catalytic gold-patterned substrates using a vapor transport process at low temperature. We observed that Au-Zn phase played an important role in initiating the ZnO nucleation, which was identified from the TEM observation of the interface between the substrate and ZnO nanowires. And then further growth of the nanowires on the ZnO surface was driven by the reaction of the Zn vapor and O₂ gas in vapor-solid growth mode. Finally, it was concluded that the site-specific deposition of ZnO nanowires was ascribed to the vapor-liquid-solid mechanism of Au, Zn vapor, and Au-Zn phases at the initial stage of ZnO nucleation.     

Synthesis, characterization and optical properties of star-like ZnO nanostructures

Star-like ZnO nanostructures were synthesized in bulk quantity by thermal evaporation method. The morphologies and structure of ZnO nanostructures were investigated by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results demonstrated that the as-synthesized products consisted of star-like ZnO nanostructure with hexagonal wurtzite phase. The legs of the star-like nanostructures were preferentially grown up along the [0001] direction. A vapor-solid (VS) growth mechanism was proposed to explain the formation of the star-like structures. Photoluminescence spectrum exhibited a narrow ultraviolet emission at around 380 nm and a broad green emission around 491 nm. Raman spectrum of the ZnO nanostructures was also discussed.     

Preparation and characterization of sol-gel Li and Al codoped ZnO thin films

Li and Al codoped ZnO (LAZO) thin films have been prepared by a sol-gel method and their structural and optical properties have been investigated. The prepared LAZO films had an average transmittance of over 85% in the visible range. The UV absorption edge was red-shifted with Li-doping, whereas it was blue-shifted with Al-doping. A broad yellowish-white emission was observed from the LAZO films annealed above 600 °C. The visible emission was enhanced with increasing annealing temperature and dopant concentration.     

N-doped ZnO nano-arrays: A facile synthesis route, characterization and photoluminescence

Field emission scanning electron microscopy (SEM) investigation reveals that array-orderly novel nanostructures, which are nanorods with many nanoparticles on the surfaces, have been synthesized at low temperature (162 °C) via a one-step in-situ process in solution. High resolution transmission electron microscope (HRTEM) and energy-dispersive X-ray spectroscopy (EDS), coupled with X-ray powder diffraction (XRD) patterns and X-ray photoelectron spectra (XPS), reveal that the as-obtained products possess crystalline structure of N-doped ZnO. The room temperature photoluminescence (PL) spectrum has also been examined to explore the optical property. The present synthesis method possesses several advantages, which would be significant to be studied deeper in the future. It is also envisioned that this method could provide a new approach to synthesize ZnO:N and other ZnO-based adulterants at low temperature.     

Synthesis of size-tunable ZnO nanorod arrays from NH3·H2O/ZnNO3 solutions

Well-aligned crystalline ZnO nanorod arrays were fabricated via an aqueous solution route with zinc nitrate and ammonia as precursors. Dip-coating was firstly utilized to form a ZnO film on ITO substrate as a seed layer for subsequent growth of ZnO nanorods. The effects of NH₃·H₂O/ZnNO₃ molar ratio, ZnNO₃ concentration, growth temperature and time on nanorod morphology were respectively investigated. It was found that the size of nanorod is mainly determined by the molar ratio and concentration. XRD demonstrates that ZnO nanorods are wurtzite crystal structures preferentially orienting in the direction of the c-axis. SEM confirms that ZnO nanorods grew up perpendicular to the substrate. The diameter and length were tunable in a broad range from 80 nm to 500 nm and 250 nm up to 8 μm, respectively. The aspect ratio changed from 3 to 17 mainly dependent on composition of the aqueous solution.     

A ZnO nanorod based layered ZnO/64° YX LiNbO3 SAW hydrogen gas sensor

A zinc oxide (ZnO) nanorod based surface acoustic wave (SAW) sensor has been developed and investigated towards hydrogen (H₂) gas. The ZnO nanorods were deposited onto a layered ZnO/64° YX LiNbO₃ substrate using a liquid solution method. Micro-characterization results revealed that the diameters of ZnO nanorods are around 100 and 40 nm on LiNbO₃ and Au (metallization for electrodes), respectively. The sensor was exposed to different concentrations of H₂ in synthetic air at operating temperatures between 200 °C and 300 °C. The study showed that the sensor responded with highest frequency shift at 265 °C. At this temperature, stable baseline and fast response and recovery were observed.     

Synthesis of ultrafine lanthanum ferrite (LaFeO3) fibers via electrospinning

Ultrafine one-dimensional LaFeO₃ nanofibers were synthesized by electrospinning utilizing sol-gel precursors. The surface morphology, microstructure and crystal structure were investigated by scanning electron microscopy, X-ray diffraction and transmission electron microscopy. The nanofibers with smaller diameter were continuous and uniformly distributed. Typical fiber diameter was between 180 nm and 220 nm and the average diameter was 200 nm. The fibers consisted of many single-crystal LaFeO₃ grains and the grain size was about 20-50 nm. The relationship between the diameter of as-synthesized fibers and the PVP concentration of the precursor was investigated. The experimental results indicated that the PVP concentration had a great impact on the fiber size and 5.89 wt.% PVP concentration in sol-gel precursors was advantageous to the formation of more uniform electrospun composite fibers with smaller diameter.     

氧化锌晶须的制备及生长机理研究

系统地介绍了氧化锌晶须的不同形态和制备方法(氧化法、液相法、微波辐射法、离子交换树脂法),阐述了氧化法制备氧化锌晶须的生长机理及应用前景.     

Electrochemical deposition and superhydrophobic behavior of ZnO nanorod arrays

Vertically aligned ZnO nanorod arrays with different heights are grown on the ZnO seeded indium tin oxide substrate by cathodic electrochemical deposition from zinc nitrate at two temperatures of 60 °C and 80 °C. As-grown ZnO nanorods exhibit wurzite crystal structure and their heights can be well controlled by different deposition times. The fluorination coating tends to induce a superhydrophobicity of ZnO nanorods, i.e., the maximal value of contact angle: 166.9°. The super water repellency can be attributed to the fact that an air layer is confined in the nanorod arrays, and thus leads to water droplets sitting on the ZnO surfaces, referring as Cassie state. Interestingly, their water contact angles are found to vary with the heights of ZnO nanorods, ranged from 99.8 to 746 nm. The superhydrophobicity of ZnO surfaces can be well predicted by a proposed model that is capable of determining the wetted fraction of ZnO pillars. This satisfactory result would shed one light on how the variation of rod height would induce the superhydrophobic behavior of ZnO nanorod arrays.     

Template-free hydrothermal synthesis of PbS nanorod by the oriented attachment mechanism

In this work, PbS nanocubes and nanorods were fabricated via a facile hydrothermal method without using any template and surfactant. The structure and morphology of as-prepared PbS nanocrystals were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). It was found that the anisotropic structure of PbS nanorods were composed of numerous assembled nanocubes, which had an uniform morphology with the mean diameters of about 100-200 nm and lengths of 0.5-7 μm. Furthermore, a possible growth mechanism was proposed to explain the formation of the nanorods on the basis of the time-dependent experimental results.     

纳米ZnO/聚苯胺复合材料的制备与表征

通过溶胶 凝胶法和O/W型乳液聚合法制备了经过十二烷基苯磺酸钠 (SDBS)修饰的纳米ZnO粉体和纳米ZnO/聚苯胺 (PAn)的复合材料 ,并进行了形貌、结构和性质的表征与分析。结果表明 ,纳米氧化锌晶形为六方晶系球形结构 ,粒径平均为 2 5nm。而纳米ZnO/PAn的复合材料也呈现出特殊的红外吸收特性 ,在 170 0cm- 1～ 330 0cm- 1出现 1个较强的吸收峰 ,同时因纳米ZnO的加入而使聚苯胺各特征峰振动强度均增强 ,所以可得出 ,纳米ZnO的掺杂对聚苯胺的红外光谱的影响较大     

Growth of ZnO nanowires on nonwoven polyethylene fibers

Abstract

We report the growth of ZnO nanowires on nonwoven polyethylene fibers using a simple hydrothermal method at a temperature below the boiling point of water. The ZnO nanowires were grown from seed ZnO nanoparticles affixed onto the fibers. The seed ZnO nanoparticles, with diameters of about 6–7 nm, were synthesized in isopropanol by reducing zinc acetate hydrate with sodium hydroxide. The growth process was carried out in a sealed chemical bath containing an equimolar solution of zinc nitrate hexahydrate and hexamethylene tetramine at a temperature of 95 °C over a period of up to 20 h. The thickness and length of the nanowires can be controlled by using different concentrations of the starting reactants and growth durations. A 0.5 mM chemical bath yielded nanowires with an average diameter of around 50 nm, while a 25 mM bath resulted in wires with a thickness of up to about 1 μm. The length of the wires depends both on the concentration of the precursor solution as well as the growth duration, and in 20 h, nanowires as long as 10 μm can be grown. The nonwoven mesh of polyethylene fibers covered with ZnO nanowires can be used for novel applications such as water treatment by degrading pollutants by photocatalysis. Photocatalysis tests carried out on standard test contaminants revealed that the polyethylene fibers with ZnO nanowires grown on them could accelerate the photocatalytic degradation process by a factor of 3.     

Growth and characterizations of ZnO nanorod/film structures on copper coated Si substrates

ZnO deposits were obtained on electroless copper coated Si substrates using a conventional RF magnetron sputter deposition technique at room temperature. The deposition pressure was varied from 6.67 Pa to 0.667 Pa. The RF powers were from 100 to 200 W and the electrode distance was fixed at 5 cm. The ZnO deposition time was varied from 1 to 30 min. The deposits consist of ZnO nanorods and a ZnO film, with the roots of the nanorods embedded in the film. The growth of the nanorods far exceeds the growth of the film in the beginning of the deposition process. The nanorod lengthening rate then slows down and becomes lower than the film growth rate. Effects of sputter deposition parameters on the growth of ZnO nanorods/film structures were also investigated.     

溶胶凝胶法制备Cu掺杂ZnO纳米薄膜及其表征

采用溶胶-凝胶法制备了不同Cu掺杂浓度的ZnO薄膜,并通过X射线衍射仪、扫描电子显微镜、紫外可见分光光度计和伏安特性测试等研究了Cu掺杂量对薄膜微观结构、表面形貌及光电特性的影响。结果表明:所得Cu掺杂ZnO薄膜为六角纤锌矿多晶结构,有CuO杂质相生成。随Cu掺杂量的增加,薄膜晶粒长大,且样品粒度均匀,平均粒径约53 nm。Cu掺杂ZnO薄膜具有良好的透光性,在可见光范围内的平均透射率超过80%,最大可达90%以上。Cu掺杂浓度为0.001%时,所得ZnO薄膜的导电性明显优于其他掺杂条件下的样品。     

Synthesis and characterization of ordered mesoporous silica by using polystyrene microemulsion as templates

A simple room temperature synthesis of pure mesoporous silica by using a homemade and functional template: polystyrene microemulsion is reported. The process consists of HCl-catalysed sol-gel reactions of tetraethyl orthosilicate (TEOS) in polystyrene microemulsion, followed by removal of the template via solvent extraction or calcining. X-ray diffraction, Transmission Electron Microscope and N₂ adsorption-desorption isotherms are then used to characterize the mesostructure. The results indicate that the synthesized mesoporous silica has a large BET surface area with more than 900 m²/g, large pore volume with more than 0.8 cm³/g and ordered mesopore-structure. This provides a possible way to control the meso-structure and pore size of mesoporous materials via potential functional templates.     

Synthesis and characterization of NiAl2O4 nanoparticles obtained through gelatin

Nanoparticles of NiAl₂O₄ were synthesized by heating (500-1000 °C) the dried resin resultant of a mixture in aqueous solution of gelatin, NiCl₂·6H₂O and AlCl₃·6H₂O. The particle size and microstrain were calculated from the line broadening of X-ray powder diffraction peaks through the Rietveld method refinement: these are 3.9-16 nm and − 0.743-0.139%, respectively. The NiAl₂O₄ nanoparticles were characterized by X-ray powder diffraction (XRPD), thermo gravimetric analysis (TG), BET and TEM techniques.