Large scale synthesis and enhanced field emission properties from hybrid CuO/ZnO nanorod

Upper-directionally grown nanorods were synthesized on a large scale by a simple method of direct heating of Cu foil in air. Hybrid CuO/ZnO nanorods were fabricated by ZnO thin film coating using magnetron sputtering. Field emission (FE) measurements of CuO and hybrid CuO/ZnO nanorod films show that they have turn-on field of 3.81 and 3.24 V/microm and a current density of 0.39 and 1.1 microA/cm2 under an applied field of about 6.6 V/microm, respectively. By comparing X-ray photoelectron spectroscopy analysis and the FE properties of two types of samples, we concluded that the narrowing of band gap due to the change of electron binding energy of hybrid CuO/ZnO nanorods effectively improved FE.     

In Situ Synthesis of CuO and Cu Nanostructures with Promising Electrochemical and Wettability Properties

A strategy is presented for the in situ synthesis of single crystalline CuO nanorods and 3D CuO nanostructures, ultra‐long Cu nanowires and Cu nanoparticles at relatively low temperature onto various substrates (Si, SiO₂, ITO, FTO, porous nickel, carbon cotton, etc.) by one‐step thermal heating of copper foam in static air and inert gas, respectively. The density, particle sizes and morphologies of the synthesized nanostructures can be effectively controlled by simply tailoring the experimental parameters. A compressive stress based and subsequent structural rearrangements mechanism is proposed to explain the formation of the nanostructures. The as‐prepared CuO nanostructures demonstrate promising electrochemical properties as the anode materials in lithium‐ion batteries and also reversible wettability. Moreover, this strategy can be used to conveniently integrate these nanostructures with other nanostructures (ZnO nanorods, Co₃O₄ nanowires and nanowalls, TiO₂ nanotubes, and Si nanowires) to achieve various hybrid hierarchical (CuO‐ZnO, CuO‐Co₃O₄, CuO‐TiO₂, CuO‐Si) nanocomposites with promising properties. This strategy has the potential to provide the nano society with a general way to achieve a variety of nanostructures.     

Aloe vera vs. poly(ethylene)glycol-based synthesis and relative catalytic activity investigations of ZnO nanorods in thermal decomposition of potassium perchlorate

The green synthesis approach using ecofriendly biological precursors has gained world-wide popularity, reputation and recognition in the synthesis of several inorganic nanomaterials. This work demonstrates that a proper selection of biological precursor from the sustainable natural resources can effectively replace the commercial surfactant for fabrication of nanomaterials. Through this work, the green biotemplate Aloe vera plant extract has emerged as a better substitute of industrial surfactant poly(ethylene)glycol of molecular weight 8000 (PEG8000) in synthesis of ZnO nanorods using a simple sonoemulsion route. The colloidal growth of ZnO nanorods in PEG8000/Aloe vera -assisted sonoemulsion route has been elaborated in the context of relative supremacy of ultrasonic-assisted self-aggregation rate with steric-hindrance effect imposed by PEG8000/Aloe vera . The relative catalytic activity of PEG8000/Aloe vera synthesized ZnO nanorods, Co₃O₄ nanobelts and CuO nanorods in thermal decomposition of potassium perchlorate has been studied by thermo-gravimetric analysis and differential thermal analysis of pure potassium perchlorate and its mixture with nanoscale ZnO/Co3O4/CuO by 2% weight. The ZnO nanorods formulated through Aloe vera route demonstrated higher catalytic activity than that of ZnO nanorods prepared through PEG8000 route. The relative order of catalytic effect of nanoscale metal oxides in thermal decomposition of potassium perchlorate was found in descending order as CuO nanorods > Co₃O₄ nanobelts > ZnO nanorods.     

纵向多孔及实心ZnO微纳米棒的制备、表征及其光催化性能研究

以硝酸锌和六次甲基四胺为原料,水为溶剂,采用低温水热法制备出具有优异光催化性能的六方纤锌矿结构ZnO微纳米棒,并研究了合成过程中磁力搅拌及原料溶液浓度对制备产物形貌及光催化性能的影响,建立了其光催化降解甲基橙的动力学方程。结果表明,搅拌条件下制备的产物为纵向多孔的棒状ZnO,无搅拌条件下制备的产物为实心ZnO纳米棒.优选出的硝酸锌和六次甲基四胺浓度均为0.025mol/L。相比于实心ZnO纳米棒,纵向多孔的棒状ZnO具有更优异的光催化性能,在紫外光照射20min后,对甲基橙的降解率达到100%。通过动力学模型拟合发现,纵向多孔的棒状ZnO具有更大的催化速率常数(0.2942 min~(-1)),是实心ZnO纳米棒催化速率常数(0.1306min~(-1))的2.25倍。     

Green hydrothermal synthesis and optical absorption properties of ZnO2 nanocrystals and ZnO nanorods

A green hydrothermal method was proposed for the controllable synthesis of ZnO₂ nanocrystals and ZnO nanorods, using the common and cost-effective 2ZnCO₃·3Zn(OH)₂ powder and 30 mass% H₂O₂ aqueous solution as the raw materials. The characterization results from X-ray diffraction, high resolution transmission electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy indicated that the products synthesized at 100-120 °C for 6 h or at 170 °C for 0 h were cubic phase ZnO₂ nanocrystals; while those synthesized at 170 °C for 3-6 h were hexagonal phase ZnO nanorods. The UV-vis absorption spectra showed that the as-synthesized ZnO₂ nanocrystals and ZnO nanorods had optical band gaps of about 4.1 and 3.3 eV, respectively.     

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.     

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.     

Synthesis and characterization of SnS/ZnO nanocomposite by chemical method

SnS nanorods and SnS/ZnO nanocomposite have been synthesized by chemical method. Structure and phase purity of the samples were confirmed by powder X-ray diffraction. Transmission electron microscope image of SnS nanorods showed the average diameter of nanorods was about 85 nm and length was several micrometers. Transmission electron microscope image of SnS/ZnO nanocomposite showed the average particle size of ZnO nanoparticle was about 12 nm. The formation of SnS/ZnO nanocomposite was confirmed by elemental analysis using energy dispersive X-ray spectroscopy. From the microRaman spectrum of SnS/ZnO nanocomposite, it was observed that the intensity of B_2g mode of SnS nanorods decreased dramatically compared to that of pure SnS nanorods, since the surface of the SnS nanorods were coated with ZnO nanoparticles. Both direct and indirect band gap transitions were observed for SnS nanorods from the optical absorption spectrum and the optical absorption spectrum of SnS/ZnO nanocomposite showed absorption in the visible region.     

微流控技术制备ZnO纳米棒及生物荧光检测性能研究

本研究设计并制备了一种微流控芯片并在其中水热合成了氧化锌(ZnO)纳米棒。利用扫描电子显微镜(SEM)和X射线衍射(XRD)研究了合成条件对ZnO纳米棒的形貌和晶体结构的影响。结果表明, 在微流控芯片中可制备得到致密的ZnO纳米棒, 其直径和长度随加热方式和制备时间的变化而改变。对比研究不同加热方式制备的ZnO纳米棒阵列检测异硫氰酸荧光素标记的羊抗牛IgG的性能, 发现局部加热方式制备的ZnO纳米棒检测荧光素标记蛋白的性能更佳, 在10 pg/mL~1 μg/mL范围内线性良好, 相关系数为0.99209。在此基础上, 用局部加热制备的ZnO纳米棒检测人甲胎蛋白(AFP), 其最低检测限可达1 pg/mL。这些结果表明, 微通道中合成的ZnO纳米棒适用于多通道荧光检测。     

Synthesis of 1-D ZnO nanorods and polypyrrole/1-D ZnO nanocomposites for photocatalysis and gas sensor applications

1-D ZnO nanorods and PPy/1-D ZnO nanocomposites were prepared by the surfactant-assisted precipitation and in situ polymerization method, respectively. The synthesized nanorods and nanocomposites were characterized by UV–Vis spectrophotometer, Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM), which gave the evidence of 1-D ZnO nanorods, polymerization of pyrrole monomer and strong interaction between PPy and 1-D ZnO nanorods, respectively. Photocatalytic activity of 1-D ZnO nanorods was conducted by 3³ level full-factorial design to evaluate the effect of three independent process variables viz., dye concentration (crystal violet), catalyst concentration (1-D ZnO nanorods) and the reaction time on the preferred response: photodegradation efficiency (%). The PPy/1-D ZnO nanocomposites were used for the sensing of NH₃, LPG, CO₂ and H₂S gases, respectively, at room temperature. It was observed that PPy/1-D ZnO nanocomposites with different 1-D ZnO nanorod weight ratios (15 and 25%) had better selectivity and sensitivity towards NH₃ at room temperature.     

Facile template-free hydrothermal synthesis and microstrain measurement of ZnO nanorods

ZnO nanorods were synthesized at low temperature by hydrothermally heating 0·1 M solution of ZnCl₂ for 5, 10 and 15 h at a pH of 10. No template, seeded substrate, catalyst and autoclave were employed for the synthesis of ZnO nanorods. The effect of heating durations on the morphology and crystal orientation of the structure were investigated by using scanning electron microscopy and X-ray diffraction, respectively. SEM images showed that the flower-like structures were formed in 5 h hydrothermally-heated sample, whereas the hexagonal zinc oxide nanorods were perfectly fabricated with the increase in growth time. XRD patterns showed that the preferred orientation in nanorods could be controlled by hydrothermal treatment time. The crystallite size and microstrain were analysed by Williamson–Hall and Halder–Wagner methods. These results revealed the presence of defects in ZnO nanorods. However, by increasing the hydrothermal treatment time, both defects in lattice and crystallite size are decreased.     

Optical and magnetic properties of copper doped ZnO nanorods prepared by hydrothermal method

Surfactant free ZnO and Cu doped ZnO nanorods were synthesized by hydrothermal method. The formation of ZnO:Cu nanorods were confirmed by scanning electron microscopy, X-ray diffraction and Raman analysis. Diffuse reflectance spectroscopy results shows that band gap of ZnO nanorods shifts to red with increase of Cu content. The orange-red photoluminescent emission from ZnO nanorods originates from the oxygen vacancy or ZnO interstitial related defects. ZnO:Cu nanorods showed strong ferromagnetic behavior, however at higher doping percentage of Cu the ferromagnetic behavior was suppressed and paramagnetic nature was enhanced. The presence of non-polar E ₂ ^high and E ₂ ^low Raman modes in nanorods indicates that Cu doping didn’t change the wurtzite structure of ZnO.     

Preparation and ethanol sensing properties of the superstructure SnO2/ZnO composite via alcohol-assisted hydrothermal route

Self-assembled superstructure of SnO₂/ZnO composite was synthesized by using alcohol-assisted hydrothermal method gas sensing properties of the material were investigated by using a static test system. The structure and morphology of the products were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM). The diameter of the SnO₂ nanorods was about 40 nm with a length of about 300 nm, SnO₂ nanorods and ZnO nanosheets interconnect each other to form a superstructure. The gas sensing properties of superstructure SnO₂/ZnO composite with different content of ZnO were investigated. Furthermore, the superstructure SnO₂/ZnO composite sensor is characterized at different operating temperatures and its long-term stability in response to ethanol vapor is tested over a period of 3 months.     

ZnO纳米棒Al掺杂和A1,N共掺杂的制备技术与光致发光性能

采用水热法首先合成了Al掺杂ZnO(AZO)纳米棒,在此基础上通过550℃的氨气氛中退火制备了Al,N共掺杂ZnO(ANZ())纳米棒.运用X射线衍射(XRD),场发射扫描电镜(FESEM),透射电子显微镜(TEM),X射线能谱(EDS)和光致发光(PL)对样品进行了表征与分析.结果表明,制备的AZO和ANZ()纳米棒...     

High quality ZnO/CuO nanocomposites synthesized by microwave assisted reaction

Highly crystalline zinc oxide (ZnO) and ZnO/CuO nanocomposite powders have been synthesized by a facile microwave irradiation method. The resulting powders were characterized in terms of structural, optical and morphological properties by X-ray diffraction (XRD), room temperature photoluminescence (PL) spectroscopy and scanning electron microscopy (SEM), respectively. XRD patterns revealed the formation of ZnO/CuO nanocomposites with good crystalline quality. SEM images displayed the formation of hexagonal ZnO and flower shaped agglomeration of ZnO/CuO nano-flakes with uniform production. The strong UV emission peak observed at around 380 nm show enhanced intensity for ZnO/CuO nanocomposite. Compared to ZnO nanoparticles, ZnO/CuO composites exhibit good transparency with sharp absorbance edges. The simplicity of synthesis route coupled with better optical and PL emission properties propose the microwave synthesized ZnO/CuO nanocomposite powders a promising material for optoelectronic devices.     

Preparation of porous sea-urchin-like CuO/ZnO composite nanostructure consisting of numerous nanowires with improved gas-sensing performance

A sea-urchin-like CuO/ZnO porous nanostructure is obtained via a simple solution method followed by a calcination process. There are abundant pores among the resulting nanowires due to the thermal decomposition of copper–zinc hydroxide carbonate. The specific surface area of the as-prepared CuO/ZnO sample is determined as 31.3 m²·g⁻¹. The gas-sensing performance of the sea-urchin-like CuO/ZnO sensor is studied by exposure to volatile organic compound (VOC) vapors. With contrast to a pure porous sea-urchin-like ZnO sensor, the sea-urchin-like CuO/ZnO sensor shows superior gas-sensing behavior for acetone, formaldehyde, methanol, toluene, isopropanol and ethanol. It exhibits a high response of 52.6–100 ppm acetone vapor, with short response/recovery time. This superior sensing behavior is mainly ascribed to the porous nanowire-assembled structure with abundant p–n heterojunctions.     

Selective H2S detection by CuO functionalized ZnO nanotetrapods at room temperature

ZnO nanotetrapods have been synthesized by carbothermal method. The structure, phase, morphology of the synthesized sample were investigated by X-ray diffraction and X-ray photoelectron spectroscopy, Scanning electron microscopy, Transmission electron microscopy and Selected area electron diffraction. The gas-sensing characteristics of thick films of pure and CuO-functionalized ZnO Nanotetrapods have been compared. Pure ZnO nanotetrapod films were found to be sensitive to both H₂S and NO with similar sensitivities, at a temperature of 250–300 °C. It is demonstrated that functionalization of ZnO nanotetrapods with CuO, results in selectivity towards H₂S at a lower temperature of 50 °C.     

Effect of leavening agent on structural and photocatalytic properties of ZnO nanorods

In the present work, we have demonstrated a simple, facile, one-step, rapid and cost effective synthesis of ZnO nanorods through the thermal decomposition of zinc acetate and leavening agent (NaHCO₃). The silver nanoparticles (AgNPs) were deposited on the surface of ZnO nanorods by photocatalytic reduction of Ag (I) to Ag(0). As synthesized ZnO nanorods and Ag–ZnO nanocomposites were characterized by using X-ray Diffraction, field emission scanning electron microscope, high-resolution transmission electron microscope and diffuse reflectance spectroscopy. The photocatalytic activities of the ZnO nanorods and Ag–ZnO nanocomposites were evaluated for the photodegradation of Methyl Orange (MO) under UV and sunlight irradiation. The use of common leavening agent helps to prevent the aggregation of ZnO nanorods, further it hinders crystallite growth and narrowing the diameter of nanorods by the evolution of carbon dioxide during calcination. The ZnO nanorods and Ag–ZnO nanocomposite exhibited an enhanced photocatalytic activity and separation of photogenerated electron and hole pairs. Due to effect of leavening agent and AgNPs deposited on surface of ZnO nanorods finds best catalyst for the 99% degradation of MO within 30 min compared to ZnO.     

Facile preparation of Ag/ZnO nanoparticles via photoreduction

Ag/ZnO nanoparticles can be obtained via photocatalytic reduction of silver nitrate at ZnO nanorods when a solution of AgNO₃ and nanorods ZnO suspended in ethyleneglycol is exposed to daylight. The mean size of the deposited sphere like Ag particles is about 5 nm. However, some of the particles can be as large as 20 nm. The ZnO nanorods were pre-prepared by basic precipitation from zinc acetate di-hydrate in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide. They are about 50–300 nm in length and 10–50 nm in width. Transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDS), X-ray powder diffraction (XRD), UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) were used to characterize the resulting Ag/ZnO nanocomposites.     

ZnO films and nanorod/shell arrays electrodeposited on PET-ITO electrodes

In this work, ZnO films, nanorod and nanorod/shell arrays were synthesized on the surface of PET-ITO electrodes by electrochemical methods. ZnO films with high optical transmittance were prepared from a zinc nitrate solution using a pulsed current technique with a reduced pulse time (3 s). The X-ray diffraction pattern of ZnO film deposited on PET-ITO electrode showed that it has a polycrystalline structure with preferred orientations in the directions [0 0 2] and [1 0 3]. ZnO nanorods were synthesized on electrochemical seeded substrate in an aqueous solution containing zinc nitrate and hexamethylenetetramine. In order to increase the stability of PET-ITO electrode to electrochemical and chemical stresses during ZnO nanorods deposition the surface of the electrode was treated with a 17 wt% NH₄F aqueous solution. Electrochemical stability of PET-ITO electrode was evaluated in a solution containing nitrate ions and hexamethylenetetramine. ZnO nanorod/shell arrays were fabricated using eosin Y as nanostructuring agent. Photoluminescence spectra of ZnO nanorod and ZnO nanorod/shell arrays prepared on the surface of PET-ITO electrode were discussed comparatively. By employing the 1.5 μm-length ZnO nanorod/shell array covered with a Cu₂O film a photovoltaic device was fabricated on the PET-ITO substrate.