Soft template-assisted synthesis of polyvinylpyrrolidone−functionalized nano-scale ZnO particles

ZnO was successfully prepared by the conventional synthetic route. Polyvinylpyrrolidone was used as soft-template to synthesize ZnO with controllable size and shape. It was found that ZnO was synthesized with average crystal size of 49 nm, as reported by an X-ray diffraction experiment. Scanning electron microscopy and transmission electron microscopy confirmed the hexagonal shape of the as-synthesized ZnO. The thus prepared ZnO colloidal particles exhibited numerous opportunities for numerous applications.     

一种纳米氧化锌复合生物基水性聚氨酯的合成和性能研究

以自制的生物基水性聚氨酯(APU)及纳米氧化锌(ZnO)为原料制备了APU/ZnO复合材料,并通过红外光谱(FT-IR)、热重(TG)、紫外(UV)、透射电镜(TEM)和扫描电镜(SEM)等手段对复合材料的性能进行了表征。TEM和SEM照片显示,制得的新型纳米ZnO的尺寸为200 nm左右,可较均匀地分散在APU体系中。TG测试结果表明添加了少量纳米ZnO的复合材料的耐热性有了明显提高。同时测试结果表明,少量纳米ZnO粒子的加入对APU有很好的增强和增韧效果,且具有一定的抗菌性和抗紫外性能。     

Synthesis of ZnO nanoparticles on a clay mineral surface in dimethyl sulfoxide medium

Nanocrystalline ZnO particles have been prepared with different methods using zinc cyclohexanebutyrate as precursor in dimethyl sulfoxide (DMSO) medium via alkaline hydrolysis. A series of preparations were carried out in the presence of layered silicates (kaolinite and montmorillonite). It was revealed by different measurement techniques that the presence of the clay minerals has a stabilization influence on the size of the ZnO nanocrystals. UV-vis absorption spectra show a blue shift when the nanoparticles are prepared in the presence of the clay minerals. The average particle diameters calculated from the Brus equation ranged from 2.6 to 13.0 nm. The UV-vis spectra of the synthesized nanoparticles did not show any red shift after 2-3 days, demonstrating that stable ZnO nanocrystals are present in the dispersions. The presence of the ZnO nanoparticles was also proven by fluorescence measurements. A number of the nanoparticles are incorporated into the interlamellar space of the clays, and an intercalated structure is formed as proven by X-ray diffraction (XRD) measurements. The size of the nanoparticles in the interlamellar space is in the range of 1-2 nm according to the XRD patterns. Transmission electron microscopy and high-resolution transmission electron microscopy investigations were applied to determine directly the particle size and the size distribution of the nanoparticles.     

Optical and Structural Studies of Chemically Synthesized ZnO Nanocrystals

ZnO nanocrystals were synthesized by adopting quenching method with Poly-vinyl alcohol as the matrix. X-ray diffraction, UV-vis spectroscopy, Photoluminescence, scanning electron microscopy, energy dispersive x-ray spectroscopy and transmission electron microscopy has been used to study the prepared samples. The size of the nanocrystals is in the range of 6.9 nm to 12.5 nm. We have successfully varied the size of the nanocrystals by varying the weight ratio of poly-vinyl alcohol and ZnO. The conductivity of the samples has been tested in atmospheric pressure as well as in vacuum.     

MOF-derived hollow NiO–ZnO composite micropolyhedra and their application in catalytic thermal decomposition of ammonium perchlorate

Ni(II)-doped Zn-based coordination polymer particles (Ni(II)-doped Zn-CPPs) with controllable shape and size were successfully synthesized by solvothermal method, which further transformed to porous ZnO–NiO composite micropolyhedra without significant alterations in shape by calcination in air. Those products were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), infrared spectroscopy (IR) and gas adsorption measurements. The catalytic activity of ZnO–NiO composites for the thermal decomposition of ammonium perchlorate (AP) was investigated. The result shows that all ZnO–NiO composites efficiently catalyzed the thermal decomposition of AP, and NiO–ZnO composite hollow octahedrons have the highest catalytic efficiency compared with that of most materials reported to now, indicating that porous ZnO–NiO composite micropolyhedra could be a promising candidate material for application in AP-based propellant.     

Preparation and Gas Sensing Performance of Hierarchical Porous ZnO-based Materials with Sunflower Rods as a Biological Template

A graded porous structure SnO2/ZnO composite was prepared with sunflower rods as a biological template. The prepared samples were subjected to phase analysis by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffractiometry(XRD) and X-ray photoelectron spectroscopy(XPS).ZnO sample was a pure phase of hexagonal wurtzite, and the template had been completely removed. The surface of the sample presented a honeycomb-like structure of a sunflower rod template, which was formed by interconnecting the porous channels, and had a smaller average size and exhibited n-n heterojunction at tlie n-type ZnO interface. Compared with that of pure ZnO, the response of the hierarchical porous structure SnO2/ZnO composite to 100 mg/L w-butanol reached a maximiuTi of 40.61 at 240℃, about 2.7 times higher than that of pure ZnO. Its response time and recovery time are 6 and 3 s, respectively, which are also better than those of pure ZnO. SnO2/ZnO composite exhibits good gas selectivity, which is related to the improvement of the structure and the forming of n-n heterojunctions of the material.     

Spherical Zinc Oxide Nano Particles from Zinc Acetate in the Precipitation Method

The liquid precipitation method using zinc acetate dihydrate was applied for the synthesis of uniform and spherical ZnO nanoparticles. The ultrafine zinc oxid was prepared in a water‐ethanol mixture solution. The solution containing zinc cation was soluble in water. The surface‐active agent triethanolamine (TEA) was soluble in ethanol. Then alkali precipitated by adding n‐propylamine. The spherical zinc oxide particle morphology was found to be highly dependent on the zinc salt concentration, ethanol‐water ratio, and the surface‐active agent additive. The process can produce white ZnO powder of 50–90 nm in size. The morphology of zinc oxide showed a powder shape by transmission electron microscopy (TEM), the crystallization phase structure of zinc oxide by X‐ray diffraction (XRD), and the zinc oxide remaining by using an organic analysis by infrared spectroscopy (IR).     

高度c轴取向的ZnO膜的低温水热法制备

在预先镀有ZnO纳米层的(0001)蓝宝石衬底上利用低温水热法制备出ZnO薄膜。SEM和XRD显示此ZnO膜是由六棱柱状阵列构成的，基于蓝宝石衬底生长，具有高度的c轴择优取向，且(0004)摇摆曲线的FWHM达到1.8°。并发现了在水热溶液中加入一定量六次甲基四胺可以调节六棱柱状ZnO尺寸比例。     

电沉积制备ZnO纳米棒修饰电极上氧化还原蛋白的电化学行为

采用恒电位阴极还原法在金电极表面一步修饰ZnO纳米棒, 制备成ZnO纳米棒修饰电极. 扫描电子显微镜(SEM)和X射线衍射(XRD)结果显示制得的ZnO为直径约100 nm的六棱柱状纤锌矿晶体纳米棒. 使用ZnO纳米棒修饰的金电极研究细胞色素c的直接电化学行为, 结果表明: ZnO纳米棒修饰的金电极能有效探测到细胞色素c的铁卟啉辅基在不同价态下的电化学行为; 细胞色素c吸附后, ZnO纳米棒修饰的金电极对过氧化氢的电流响应呈现良好的线性关系.     

A simple solvothermal route towards the morphological control of ZnO and tuning of its optical and photocatalytic properties

ZnO nanoparticles with different morphologies were solvothermally synthesized by controlling the alkali (sodium hydroxide) concentration in an isopropanol solution. The products were characterized by means of powder X-ray diffraction, UV-visible absorption spectra, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. The morphologies of the formed ZnO nanocrystals were dependent on the concentration of the alkali, and with increases of sodium hydroxide concentration, the ZnO nanocrystals evolved from rod to hexagonal bipyramid, and then to a flower-like nanostructure. The flower-like nanostructure resulted from the etching of the hexagonal bipyramid by the excess alkali. The photoluminescence and photocatalytic properties of the prepared ZnO were investigated. The difference of green emission among the ZnO nanocrystals indicated that a higher sodium hydroxide concentration led to a higher level of defects. The size, the surface structure and defects in the ZnO nanocrystals affected its photo-degradation characteristics.     

基底对电沉积制备ZnO纳米棒阵列的影响

采用恒电位电沉积方法, 在未经修饰的ITO导电玻璃基底上通过控制实验条件制备出不同形貌的纳米ZnO结构, 而在经过ZnO纳米粒子膜修饰后的ITO导电玻璃基底上, 制备出透明、高取向、粒径小于30 nm的ZnO纳米棒阵列. 用扫描电子显微镜(SEM)、X射线衍射(XRD)以及透射光谱对制备出的ZnO纳米棒阵列的结构、形貌和透明性进行了表征. 测试结果表明, ZnO纳米棒阵列的平均直径为21 nm, 粒径分布窄, 约18～25 nm, 择优生长取向为[001]方向, 垂直于基底生长. 当入射光波长大于400 nm时, ZnO纳米棒阵列的透光率大于95%.     

Preparation and UV-light Absorption Property of Oleic Acid Surface Modified ZnO Nanoparticles

Syntheses of zince oxide(ZnO) nanoparticles by direct precipitation and surface modification with oleic acid were reported. ZnO nanoparticles were characterized via X-ray diffractometry(XRD), transmission electron microscopy(TEM), infrared spectroscopy(IR) and UV-Vis spectroscopy. The prepared ZnO nanoparticles were nearly spherical and highly crystalline with an average size of 29 nm. In addition, high UV-light absorption properties of oleic acid surface modified ZnO nanoparticles were successfully obtaine...     

ZnO自组装薄膜的可控生长及其光催化性能

通过改变工艺参数, 制得了粒径可控的ZnO自组装薄膜. 该薄膜在可见光区域出现了光子带隙. 以染料甲基橙的光催化降解为模型评价了ZnO自组装薄膜的光催化活性. 利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征了ZnO的晶体结构和微观形貌. 实验结果表明, ZnO自组装薄膜在太阳光照射下表现出良好的光催化性能, 其光催化活性随着ZnO颗粒粒径的减小而提高. ZnO自组装薄膜光催化降解甲基橙的反应符合一级反应动力学规律.     

Straight and thin ZnO nanorods: hectogram-scale synthesis at low temperature and cathodoluminescence

A novel seed-assisted chemical reaction at 95 degrees C has been employed to synthesize uniform, straight, thin, and single-crystalline ZnO nanorods on a hectogram scale. The molar ratio of ZnO seed and zinc source plays a critical role in the preparation of thin ZnO nanorods. At a low molar ratio of ZnO seed and zinc source, javelin-like ZnO nanorods consisting of thin ZnO nanorods with a diameter of 100 nm and thick ZnO nanorods with a diameter of 200 nm have been obtained. In contrast, straight ZnO nanorods with a diameter of about 20 nm have been prepared. Dispersants such as poly(vinyl alcohol) act spatial obstructors to control the length of ZnO nanorods. The morphology, structure, and optical property of the ZnO nanostructures prepared under different conditions have been characterized by transmission electron microscopy, field emission scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and cathodoluminescence. The formation mechanisms for the synthesized nanostructures with different morphologies have been phenomenologically presented.     

Standard molar enthalpy of formation of the ZnO nanosheets

ZnO nanosheets were prepared by a facile microemulsion-mediated hydrothermal route, and were characterized by X-ray powder diffraction, field-emission scanning electron microscopy, and transmission electron microscopy. As nano ZnO and bulk ZnO possess the same reaction essence, the relationship between standard molar enthalpies of formation of nano ZnO and bulk ZnO was built by designing a novel thermochemical cycle. Combined with microcalorimetry, standard molar enthalpy of formation of the as-prepared ZnO nanosheets at 298.15?K was successfully acquired as (?333.50?±?0.29) kJ?mol^?1. It is an effective strategy for standard molar enthalpies of formation of nano materials through building the relationship with its corresponding bulk material.     

Molecular dynamics simulations of inverse sodium dodecyl sulfate (SDS) micelles in a mixed toluene/pentanol solvent in the absence and presence of poly(diallyldimethylammonium chloride) (PDADMAC)

Well-aligned ZnO nanorods (NRs) were grown on indium-tin-oxide (ITO) slide by the hydrothermal method and used as templates for preparing ZnO/Au composite nanoarrays. The optical and morphological properties of ZnO/Au composites under various HAuCl(4) concentrations were explored via UV-vis absorption spectroscopy, photoluminescence (PL) and scanning electron microscopy (SEM). The density and size of gold nanoparticles (Au NPs) on ZnO NRs can be controlled by adjusting the concentration of HAuCl(4). The optimal ZnO/Au composites display complete photocatalytic degradation of methyl blue (MB) within 60 min, which is superior to that with pure ZnO NRs prepared by the same method. The reason of better photocatalytic performance is that Au NPs act as electron traps and it prevents the rapid recombination of electrons and holes, resulting in the improvement of photocatalytic efficiency. The photocatalytic performance of ZnO/Au composites is mainly controlled by the density of Au NPs formed on ZnO NRs. The application in rapid photodegradation of MB shows the potential of ZnO/Au composite as a convenient catalyst for the environmental purification of organic pollutants.     

Hybrid zinc oxide conjugated polymer bulk heterojunction solar cells

Bulk heterojunction photovoltaic devices based on blends of a conjugated polymer poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) as electron donor and crystalline ZnO nanoparticles (nc-ZnO) as electron acceptor have been studied. Composite nc-ZnO:MDMO-PPV films were cast from a common solvent mixture. Time-resolved pump-probe spectroscopy revealed that a photoinduced electron transfer from MDMO-PPV to nc-ZnO occurs in these blends on a sub-picosecond time scale and produces a long-lived (milliseconds) charge-separated state. The photovoltaic effect in devices, made by sandwiching the active nc-ZnO:MDMO-PPV layer between charge-selective electrodes, has been studied as a function of the ZnO concentration and the thickness of the layer. We also investigated changing the degree and type of mixing of the two components through the use of a surfactant for ZnO and by altering the size and shape of the nc-ZnO particles. Optimized devices have an estimated AM1.5 performance of 1.6% with incident photon to current conversion efficiencies up to 50%. Photoluminescence spectroscopy, atomic force microscopy, and transmission electron microscopy have been used to gain insight in the morphology of these blends.     

ZnO twin-cones: synthesis, photoluminescence, and catalytic decomposition of ammonium perchlorate

ZnO twin-cones, a new member to the ZnO family, were prepared directly by a solvothermal method using a mixed solution of zinc nitrate and ethanol. The reaction and growth mechanisms of ZnO twin-cones were investigated by X-ray diffraction, UV-visible spectra, infrared and ion trap mass spectra, and transmission electron microscopy. All as-prepared ZnO cones consisted of tiny single crystals with lengths of several micrometers. With prolonging of the reaction time from 1.5 h to 7 days, the twin-cone shape did not change at all, while the lattice parameters increased slightly and the emission peak of photoluminescence shifted from the green region to the near orange region. ZnO twin-cones are also explored as an additive to promote the thermal decomposition of ammonium perchlorate. The variations of photoluminescence spectra and catalytic roles in ammonium perchlorate decomposition were discussed in terms of the defect structure of ZnO twin-cones.     

水热法生长方式对ZnO纳米棒阵列结构和性能的影响

本文系统地比较了三种方式制备的ZnO纳米棒阵列的结构和性能的异同.根据水热法生长液中碱来源的不同,ZnO纳米棒阵列的生长方式分为三种:N方式(氨水)、H方式(六次甲基四胺)和NH方式(两次N方式和一次H方式).通过扫描电子显微镜,对这三种方式生长的ZnO纳米棒阵列形貌进行了表征.此外,利用X射线衍射仪、透射电子显微镜和激光拉曼光谱对ZnO的结晶性能进行比较.结果表明,ZnO纳米棒阵列的取向性N≈NH>H,ZnO的晶体质量H>NH>N.NH方式综合N方式和H方式的优势,得到了取向性和晶体质量优良的ZnO纳米棒阵列.这将为在进一步应用中有效地选择ZnO纳米棒阵列的制备方式提供重要信息.     

Boehmite sol properties and preparation of two-layer alumina membrane by a sol-gel process

A two layer ultrafiltration alumina membrane was prepared by a sol-gel process using boehmite sol as precursor. The sol was prepared by hydrolysation of aluminium tri-sec-butoxide. Sol properties, such as viscosity as a function of concentration and acidity, were investigated by using capillary viscometry, transmission electron microscopy and laser scattering photometry etc. The viscosity increased with an increase in concentration and a decrease in pH, while the particle shape and size of the sol were mainly determined by pH. The membrane prepared by a dipping procedure was characterized by both scanning electron microscopy and transmission electron microscopy. The results showed that the membrane thickness and surface morphology were affected by the dipping time, the viscosity and the temperature.