室温固相法合成ZnO纳米棒及其光学特性

在氯化钠存在下,以硫酸锌和氢氧化钠为原料,采用一步室温固相法制备了纳米氧化锌.XRD、TEM分析结果表明:所得纳米氧化锌为棒状,直径约10nm左右,长度约100～160nm.利用紫外-可见分光光度计测试了光吸收性能,发现ZnO纳米棒对200～380nm波长范围的光有很强吸收性,在可见光范围内,也有较强的吸收.ZnO纳米棒在550nm左右具有较弱的荧光发光峰且ZnO纳米棒较普通氧化锌发光峰波长发生了明显的红移.     

A comparative study on the NO2 gas sensing properties of ZnO thin films, nanowires and nanorods

ZnO thin films were fabricated using the spin coating method, ZnO nanowires by cathodically induced sol-gel deposition by the means of an anodic aluminum oxide (AAO) template, and ZnO nanorods with the hydrothermal technique. For thin film preparation, a clear, homogeneous and stable ZnO solution was prepared by the sol-gel method using zinc acetate (ZnAc) precursor which was then coated on a glass substrate with a spin coater. Vertically aligned ZnO nanowires which were approximately 65 nm in diameter and 10 μm in length were grown in an AAO template by applying a cathodic voltage in aqueous zinc nitrate solution at room temperature. For fabrication of the ZnO nanorods, the sol-gel ZnO solution was coated on glass substrate by spin coating as a seed layer. Then ZnO nanorods were grown in zinc nitrate and hexamthylenetetramine aqueous solution. The ZnO nanorods are approximately 30 nm in diameter and 500 nm in length. The ZnO thin film, ZnO nanowires and nanorods were characterized by X-ray diffraction (XRD) analysis and scanning electron microscope (SEM). The NO₂ gas sensing properties of ZnO thin films, nanowires and nanorods were investigated in a dark chamber at 200 °C in the concentration range of 100 ppb-10 ppm. It was found that the response times of both ZnO thin films and ZnO nanorods were approximately 30 s, and the sensor response was depended on shape and size of ZnO nanostructures and electrode configurations.     

Catalytic effects of ZnO nanorods grown by sonochemical decomposition of zinc acetate dihydrate

In this study, we prepared ZnO nanorods by a sonochemical method using a zinc acetate dihydrate as a new precursor. Well-aligned high-quality ZnO nanorods were synthesized on FTO glass by the sonochemical decomposition of zinc acetate dihydrate using a ZnO thin-film as the catalytic layer. The ZnO thin-films were deposited on the FTO glass by a sputtering method. To investigate their catalytic effects on the ZnO nanorods, catalytic ZnO thin-films of 20 nm, 40 nm, and 60 nm thickness were prepared by adjusting the sputtering time. The ZnO nanorods grown on catalytic layers with different thicknesses were characterized by SEM, XRD, and PL. The ZnO nanorods grown on the catalytic layer of 40 nm thickness show the best crystal and spatial orientation and as a result display the best optical properties. It was found that a catalytic ZnO thin-film of 40 nm in thickness yields well-aligned high-quality ZnO nanorods, due to its small surface roughness and structural strain.     

海胆形氧化锌纳米结构的制备与光催化性能

以Zn(AC)2.2H2O为原料,NH3.H2O为络合剂,在NaBH4辅助下140℃水热反应2 h制备出ZnO纳米棒自组装的海胆形结构。采用X射线衍射仪、扫描电镜和透射电镜对产物进行表征。结果表明,海胆形ZnO结构的直径约为3～17μm,它是由直径约为100 nm,长度约为500 nm～3μm范围的ZnO纳米棒自组装而成。提出了ZnO纳米棒自组装海胆形结构的可能生长机理。NaBH4与溶液中的少量H+结合生成H2气泡,ZnO纳米晶吸附在H2的气液界面形成了纳米颗粒自组装的微球,随着反应时间的延长,组装成微球的ZnO纳米颗粒沿[0001]方向取向生长成ZnO纳米棒,最终形成ZnO纳米棒自组装的海胆形颗粒。室温下以海胆形ZnO纳米结构和ZnO纳米棒为光催化剂,以偶氮染料甲基橙作为光催化研究对象,紫外光照70 min,对甲基橙的降解率分别为97%和67%。     

Effect of reaction conditions on the morphology and optical properties of ZnO nanocrystals

We report a simple hydrothermal method at low temperature for synthesis of zinc oxide (ZnO) nanorods followed by ultrasonication. The samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), UV–Vis absorption spectrophotometer and photoluminescence (PL) spectroscopy. The XRD results shows the prepared ZnO nanocrystals are in wurtzite structure. TEM results indicate the growth of ZnO nanorods with increasing reaction stirring time and morphology also get affected after ultrasonication. PL studies also reveal the presence of defects considered as the main reason for the green emission in PL with increasing reaction time and blue shift in UV emission corresponds to reduction of tensile strain.     

Comparison between synthesis techniques to obtain ZnO nanorods and its effect on dye sensitized solar cells

This paper reports additive-free, reproducible, low-temperature solution-based process for the preparation of crystalline ZnO nanorods by homogeneous precipitation from zinc acetate. Also, ZnO nanorod structured dye sensitized solar cells using ruthenium dye (Z907) have been fabricated and characterized. The formation and growth of zinc oxide nanorods are successfully achieved. We analyzed three different synthesis method using solution phase, autoclave and microwave. The calcination effects on the morphology of ZnO nanorods are also investigated. Analysis of ZnO nanorods shows that calcination at lower temperature is resulted in a nanorod growth. Additive-free, well-aligned ZnO nanorods are obtained with the length of 330–558 nm and diameters of 14–36 nm. The XRD, SEM, and PL spectra have been provided for the characterization of ZnO nanorods. Microwave-assisted ZnO nanostructured dye sensitized solar cell devices yielded a short-circuit photocurrent density of 6.60 mA/cm², an open-circuit voltage of 600 mV, and a fill factor of 0.59, corresponding to an overall conversion efficiency of 2.35% under standard AM 1.5 sun light.     

Low-temperature synthesis of ZnO nanorods using organic-inorganic composite as a seed layer

Well-aligned zinc oxide (ZnO) nanorods were synthesized using a low-temperature hydrothermal method employing a zinc/sodium dodecyl sulfate (Zn/SDS) composite as a seed layer. The results of X-ray diffraction measurements indicate that the Zn/SDS composite has a lamellar structure with an interlayer distance of 3.12 nm, which is shorter than that of the lamellar structure of SDS (3.82 nm) due to ion exchange between Zn and Na. The results of X-ray absorption fine structure analyses suggest that ZnO crystals start to grow after an induction period of 20-30 min. The length of nanorods and the aspect ratio of ZnO nanorods could be controlled by altering the molarity of ammonium and zinc nitrate in the growth solutions.     

A simple microwave-assisted decomposing route for synthesis of ZnO nanorods in the presence of PEG400

In the paper, a simple microwave-assisted decomposing reaction in the presence of PEG400 has been successfully developed to synthesize ZnO nanorods with 10-25 nm of diameter and 60-200 nm of length. The product was analyzed and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and HRTEM. Ultraviolet-visible (UV-vis) absorption peak of ZnO nanorods shows a distinct blue shift from that of the bulk and the Photoluminescence (PL) spectrum exhibits a strong near-band-edge emission at 385 nm. Further experiments have also been designed, and the results show that microwave radiation and surfactant PEG400 all played an important role on the formation of ZnO nanorods.     

Synthesis,microstructure and photoluminescence of well-aligned ZnO nanorods on Si substrate

Well-aligned zinc oxide (ZnO) nanorods were densely grown on Si substrate using ZnO thin-film seed layer without any catalysts and/ or additives by a simple solid–vapour phase thermal sublimation technique. The growth mechanism can be interpreted as self-catalyst of zinc particles based on vapour–solid (VS) mechanism. High-resolution transmission electron microscopy (HRTEM) image and selected area electron diffraction (SAED) pattern confirmed that the single-crystalline growth of the nanorods were preferentially along c-axis of hexagonal crystal system. High-crystal quality ZnO nanorods with strong near band edge emission centred at 380 nm can be achieved on Si substrate by the introduction of sufficient oxygen during the nanorod growth processing.     

A facile low-cost synthesis of ZnO nanorods via a solid-state reaction at low temperature

ZnO nanorods have been prepared via a solid-state reaction between anhydrous zinc sulfate and sodium hydroxide in the absence of surfactant and template at relatively low temperature. The products were characterized by XRD, XPS and TEM. The influence of Zn²⁺/OH⁻ ratio on the size and morphology of the as-prepared ZnO samples has been studied, and the experimental results showed that when Zn²⁺/OH⁻ ratio was 1:4, good rod-like morphology with the diameter of 30–50 nm and length of ca. 600 nm can be obtained. Finally, the mechanism for the ZnO nanorods developed in the reaction system has been explained.     

氧化锌纳米棒微球的水热制备及其气敏性质研究

以Zn粉为原料,采用水热法制备了由氧化锌纳米棒自组装而成的氧化锌纳米棒微球和氧化锌亚微米棒,对氧化锌纳米棒微球进行了镍掺杂,用x射线衍射仪和扫描电镜对产物的结构和微观形貌进行了表征,探讨了反应机理,并测试了其气敏性质.研究发现,氧化锌纳米棒微球具有良好的气敏性质,对酒精和汽油具有较高的灵敏度,镍的掺杂明显提高了氧化锌纳米棒微球在酒精和汽油之间的选择性.     

反应时间对球状及棒状ZnO纳米晶的影响

本实验采用溶液法合成球状及棒状ZnO纳米晶。X射线衍射分析(XRD)显示合成的纳米晶为六方纤锌矿结构ZnO。紫外可见光(UV-vis)光谱和透射电镜(TEM)图表明通过改变反应时间可以控制ZnO纳米棒的长度。随着反应时间从90min延长到360min,纳米棒的长度可以从25nm长大到60nm。同时,纳米晶的室温光致发光谱(PL)具有强烈的近带边发射,在LED和LD等光电器件上有一定的应用前景。     

Sonochemical method for the preparation of ZnO nanorods and trigonal-shaped ultrafine particles

ZnO nanorods and trigonal-shaped ZnO ultrafine particles were synthesized by sonochemical method through the decomposition of zinc acetate dihydrate in paraffin oil. ZnO nanorods and trigonal-shaped ZnO ultrafine particles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), and UV–visible spectrophotometer. One strong UV emission peak at 390 nm was observed.     

Sensitization of ZnO nanorods with CdSe quantum dots

We have optimized the low-temperature growth of aligned arrays of zinc oxide nanorods of controlled length and diameter on conductive substrates. Varying the solution concentration and growth time, we were able to tune the nanorod diameter and length in the ranges 40–600 nm and 0.5–15 μm, respectively. The grown zinc oxide nanorods were photosensitized with CdSe quantum dots (QDs) in an oleic shell, which was replaced by pyridine. We studied the optical and transport properties of the ZnO nanorod arrays, with and without CdSe QDs on their surface. The current-voltage characteristics of the ZnO nanorod arrays with CdSe QDs are significantly influenced by illumination with light at a wavelength under the absorption band of the QDs, which points to effective interaction between the QDs and ZnO matrix.     

Synthesis of Sn-doped ZnO nanorods and their photocatalytic properties

Sn-doped ZnO nanorods were fabricated by a hydrothermal route, and characterized by X-ray diffraction, field emission scanning electron microscope, UV-vis spectroscopy, Raman spectra, solid-state nuclear magnetic resonance (NMR) spectra, and room temperature photoluminescence spectroscopy. Solid-state NMR result confirms that Sn⁴⁺ was successfully incorporated into the crystal lattice of ZnO. Room temperature photoluminescence showed that all the as-synthesized products exhibited a weak UV emission (380 nm) and a strong visible emission (540 nm), but the intensities of the latter emission increased with increase in Sn concentration. The improvement of visible emission at 540 nm in the Sn-doped ZnO samples was suggested to be a result of the lattice defects increased by doping of Sn in zinc oxide. In addition, the photocatalytic studies indicated that Sn-doped ZnO nanorods are a kind of promising photocatalyst in remediation of water polluted by some chemically stable azo dyes.     

Reactions of sulphur mustard on impregnated carbons

Activated carbon of surface area 1100 m2/gm is impregnated with 4% sodium hydroxide plus 3% Cr(VI) as CrO3 with and without 5% ethylene diamine (EDA), 4% magnesium nitrate and 5% ruthenium chloride by using their aqueous solutions. These carbons are characterized for surface area analysis by BET conventional method and exposed to the vapours of sulphur mustard (HD) at room temperature (30 degrees C). After 24 h, the reaction products are extracted in dichloromethane and analyzed using gas chromatography and mass spectrometry (GC-MS). Hemisulphur mustard, thiodiglycol, 1,4-oxathiane are observed to be the products of reaction between sulphur mustard and NaOH/CrO3/C system, whereas on NaOH/CrO3/EDA/C system HD reacted to give 1,4-thiazane. On Mg(NO3)2/C system it gave hemisulphur mustard and thiodiglycol. On RuCl3/C system it degraded to divinyl sulphone. Residual sulphur mustard is observed along with reaction products in all systems studied. Reaction mechanisms are also proposed for these interesting surface reactions. Above-mentioned carbons can be used in filtration systems for protection against hazardous gases such as sulphur mustard.     

CO2-mediated synthesis of ZnO nanorods and their application in sensing ethanol vapor

High-purity ZnO nanorods have been synthesized via a two-step route using zinc acetate as a precursor without any surfactant and additive. In this method, ZnCO3 fibers were first formed in the CO2-ethanol solution, which directed the formation of ZnO nanorods by subsequent treatment in KOH aqueous solution. The as-prepared nanorods were fully characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and Fourier transform Infrared spectroscopy. It was found that the as-obtained ZnO nanorods were single crystals with uniform diameter around 150 nm and length of 4 microm. The nanorod crystals were prismatic with hexagonal cross sections, consistent with the wurtzite lattice structure. Moreover, the sensing properties of the as-prepared ZnO nanorods were also investigated. It was demonstrated that they exhibited good performance for detecting ethanol vapor even at 380 and 250 degrees C.     

Synthesis, microstructure and photoluminescence of well-aligned ZnO nanorods on Si substrate

Well-aligned zinc oxide (ZnO) nanorods were densely grown on Si substrate using ZnO thin-film seed layer without any catalysts and/or additives by a simple solid–vapour phase thermal sublimation technique. The growth mechanism can be interpreted as self-catalyst of zinc particles based on vapour–solid (VS) mechanism. High-resolution transmission electron microscopy (HRTEM) image and selected area electron diffraction (SAED) pattern confirmed that the single-crystalline growth of the nanorods were preferentially along c-axis of hexagonal crystal system. High-crystal quality ZnO nanorods with strong near band edge emission centred at 380 nm can be achieved on Si substrate by the introduction of sufficient oxygen during the nanorod growth processing.     

Synthesis of nanometal oxides and nanometals using hot-wire and thermal CVD

We report the synthesis of nano-oxides of molybdenum, tungsten, and zinc. Molybdenum oxide (MoO₃) and tungsten oxide (WO_x) were produced by hot-wire CVD with molybdenum and tungsten filaments, respectively while zinc oxide (ZnO) was produced by thermal CVD. When high purity molybdenum wire was oxidized at ambient system atmosphere, nanorods and nanostraws of MoO₃ with length ranging from ∼ 20-80 nm and diameters ranging from ∼ 5-15 nm were produced. Also, the oxidation of the tungsten filament led to the deposition of tungsten oxide nanorods (10-25 nm diameter and 75-90 nm long) and nanospheres with diameters of ∼ 60 nm. Each oxide was reduced to its metallic form by annealing in a hydrogen environment to produce metallic nanoparticles. Nanorods and nanoribbons of ZnO with diameters ranging from 20-65 nm and lengths up to 2 μm were also produced.     

Ultraviolet sensing properties of polyvinyl alcohol-coated aluminium-doped zinc oxide nanorods

Undoped and aluminium (Al)-doped zinc oxide (ZnO) nanorods have been synthesized by electrochemical route. The synthesized materials have been characterized by X-ray diffraction, UV–visible spectrometer and scanning electron microscope. The Al-doped ZnO nanorods have been coated with polyvinyl alcohol. Current–voltage characteristics have been investigated in dark and under UV-light illumination. Aluminium doping in ZnO increase its electrical conductivity and further polyvinyl alcohol coating on Al-doped ZnO increase UV sensitivity of the material. Response and recovery time of Al-doped ZnO and PVA-coated Al-doped ZnO nanorods have been recorded. PVA-coated Al-doped ZnO nanorods shows very fast response and recovery time of 10 s in comparison to uncoated ZnO (20 min) nanorods.