ZIF-8衍生La掺杂ZnO纳米颗粒的制备及其气敏性能

以ZIF-8及La掺杂ZIF-8为前驱体,经高温煅烧制备ZnO及La掺杂ZnO纳米颗粒.研究了La掺杂对ZnO纳米颗粒的形貌、晶体结构及气敏性能的影响.利用X射线衍射仪、扫描电子显微镜对材料的微结构进行表征,结果表明:La掺杂有利于获得更小粒径的类球形纳米结构,但La掺杂未改变ZIF-8及衍生ZnO纳米结构的晶体结构....     

One-dimensional ZnO nanostructures: fabrication, optoelectronic properties, and device applications

One-dimensional (1D) zinc oxide (ZnO) nanostructures have been extensively and intensively studied for several decades not only for their extraordinary chemical and physical properties, but also for their current and future different electronic and optoelectronic device applications. This review provides a brief overview of the progress of different synthesis methods and applications of 1D-ZnO nanostructures. Morphology of ZnO nanostructures grown by various methods and progress in the optical properties are briefly described. Using low-temperature photoluminescence (LTPL) study, detailed informations about the defect states and impurity of such nanostructures are reported. Improvement of field emission properties by modifying the edge of 1D-ZnO nanostructures is briefly discussed. Applications such as different sensors, field effect transistor, light-emitting diodes (LEDs), and photodetector are briefly reviewed. ZnO has large exciton binding energy (60 meV) and wide band gap (3.37 eV), which could lead to lasing action based on exciton recombination. As semiconductor devices are being aggressively scaled down, ZnO 1D nanostructures based resistive switching (RS) memory (resistance random access memory) is very attractive for nonvolatile memory applications. Switching properties and mechanisms of Ga-doped and undoped ZnO nanorods/NWs are briefly discussed. The present paper reviews the recent activities of the growth and applications of various 1D-ZnO nanostructures for sensor, LED, photodetector, laser, and RS memory devices.     

ZnO基纳米电子材料研究进展

纳米ZnO的许多优异性能使其成为人们研究的热点并得到广泛应用.ZnO是一种同时具有半导体和压电双重特性的材料.运用不同的工艺,目前已生长出纳米线(棒)、纳米带、纳米环、四角形纳米结构、纳米笼、纳米螺旋等多种特殊形态的纳米ZnO.由这些许多独特的形态,可以看出纳米ZnO是纳米材料家族中可以生长出的结构最多样的成员之一.这些纳米结构在光电、传导、传感以及生化等不同领域有很多潜在的新颖的应用前景.     

Effect of microwave power on the morphology and optical property of zinc oxide nano-structures prepared via a microwave-assisted aqueous solution method

The effect of the microwave power on the morphology and optical properties of zinc oxide nanostructures prepared using a microwave-assisted aqueous solution method has been investigated. The ZnO nanostructures were synthesized from zinc chloride and sodium hydroxide mixed aqueous solutions exposed for 5 min to microwave radiation at four different powers, namely 150, 450, 700 and 1000 W. The morphologies of the samples have been characterized by transmission electron microscope (TEM) and scanning electron microscope (SEM). The results showed that the power of microwave radiation influenced the shape and size of the synthesized nanostructures. It is also found that the average particle size of nanostructures decreased with decreasing microwave power. The results of X-ray diffraction (XRD) showed that all the as-prepared ZnO nanostructures are in crystalline form with high purity. The infrared (IR) spectra indicated that the as-prepared nano ZnO product can be used as infrared gas sensors such as an infrared carbon dioxide (CO₂) and/or CO sensor. Optical properties of the as-prepared ZnO nanostructures were investigated by UV–vis spectroscopy and showed that the optical properties of as-synthesized ZnO samples are sensitive to the variation of the power of microwave radiation.     

ZnO nanostructures for efficient perovskite solar cells

Controlled ZnO nanostructures were synthesized via spin-coating and in situ thermal decomposition processing using ZnO paster with/without zinc acetate as precursor. The perovskite CH₃NH₃PbI₃ solar cells (PSCs) based on these ZnO nanostructures were fabricated and their photovoltaic performances have also been investigated. Effects of zinc acetate concentration on morphologies of ZnO nanostructures and the photovoltaic properties of corresponding PSCs have been discussed. Interestingly, the morphologies of ZnO nanostructures were varied from separate nanoparticles to interconnect net-like nanostructures and the space of ZnO nanoparticles became large when the concentration of zinc acetate was increased from 0 to 0.13 M. The space and the connection degree of ZnO nanostructure obtained from 0.05 M zinc acetate are the best choice for perovskite infiltration and charge transport, which leads to corresponding cells have highest power conversion efficiencies (PCE) of 9.30 %. Post-treatment of ZnO nanostructures improved further Voc and FF, leading to PCE to 13.1 %.     

Zinc oxide nanostructures: from growth to application

Zinc oxide’s (ZnO) physical and chemical properties make it a viable and extremely attractive compound to use in a variety of nanotechnology applications. Some of these applications include biomedical, energy, sensors, and optics. As the research in ZnO nanostructures continue to grow, it has inspired a whole host of new innovative applications. Complementing its unique chemical qualities, it also has a simple crystal-growth technology and offers significantly lower fabrication costs when compared to other semiconductors used in nanotechnology. Several processes have been developed in order to synthesize high quality ZnO nanostructures—specifically in the case of nanowires. Here we offer a comprehensive review on the growth methods currently employed in research, industry, and academia to understand what protocols are available to meet specific needs in nanotechnology. Methods examined include: the vapor–liquid–solid, physical vapor deposition, chemical vapor deposition, metal–organic chemical vapor deposition, and the hydrothermal-based chemical approach. Each of these methods is discussed and their strengths and weaknesses are analyzed with objective comparison metrics. In addition, we study the current state-of-the-art applications employing ZnO nanostructures at their core. A historical perspective on the evolution of the field and the accompanying literature are also presented.     

Tunable ZnO nanostructures for ethanol sensing

In this study, ZnO nanostructures with different morphologies including nanorods, nanowires, and nanobrushes were synthesized by a simple hydrothermal process without using any structure-directing reagent. The samples were characterized by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The influence of the preparation parameters on the morphology of ZnO is discussed. Gas-sensing properties of the materials were investigated. The results reveal that all the prepared nanostructured ZnO powders show high response to ethanol, among which, the three-dimensional nanobrushes show the highest response, demonstrating excellent potentiality for ethanol sensors.     

High-yield self-assembly of flower-like ZnO nanostructures

High-yield three-dimensional (3D) flower-like nanostructures self-assembled from 1 D ZnO nanorods and nanotubes are experimentally demonstrated. The Zn and O terminated crystal planes of ZnO nanorods results in positively and negatively charged top (001) and bottom (00-1) surfaces, respectively. The nanorods self-assembled into 3D nanostructures via the electrostatic interaction between the crystal planes with opposite charges. Moreover, on the basis of the different stability of polar and nonpolar planes in wurtzite-type ZnO, the nanorods based 3D nanostructures transformed into nanotubes based ones spontaneously. This provides a new approach to prepare multi-dimensional materials without the necessity to employ any external intervention.     

Microstructure and optical properties of Ag-doped ZnO nanostructures prepared by a wet oxidation doping process

Silver-doped zinc oxide (Ag:ZnO) nanostructures were prepared by a facile and efficient wet oxidation method. This method included two steps: metallic Zn thin films mixed with Ag atoms were prepared by magnetron sputtering as the precursors, and then the precursors were oxidized in an O(2) atmosphere with water vapour present to form Ag:ZnO nanostructures. By controlling the oxidation conditions, pure ZnO and Ag:ZnO nanobelts/nanowires with a thickness of ～ 20 nm and length of up to several tens of microns were synthesized. Scanning electron microscopy, transmission electron microscopy, cathodoluminescence and low temperature photoluminescence (PL) measurements were adopted to characterize the microstructure and optical properties of the prepared samples. The results indicated that Ag doping during magnetron sputtering was a feasible method to tune the optical properties of ZnO nanostructures. For the Ag:ZnO nanostructures, the intensity of ultraviolet emission was increased up to three times compared with the pure ones. The detailed PL intensity variation with the increasing temperature is also discussed based on the ionization energy of acceptor in ZnO induced by Ag dopants.     

2D Zinc Oxide – Synthesis,Methodologies, Reaction Mechanism,and Applications

Zinc oxide (ZnO) is a thermally stable n-type semiconducting material. ZnO 2D nanosheets have mainly gained substantial attention due to their unique properties, such as direct bandgap and strong excitonic binding energy at room temperature. These are widely utilized in piezotronics, energy storage, photodetectors, light-emitting diodes, solar cells, gas sensors, and photocatalysis. Notably, the chemical properties and performances of ZnO nanosheets largely depend on the nano-structuring that can be regulated and controlled through modulating synthetic strategies. Two synthetic approaches, top–down and bottom–up, are mainly employed for preparing ZnO 2D nanomaterials. However, owing to better results in producing defect-free nanostructures, homogenous chemical composition, etc., the bottom–up approach is extensively used compared to the top–down method for preparing ZnO 2D nanosheets. This review presents a comprehensive study on designing and developing 2D ZnO nanomaterials, followed by accenting its potential applications. To begin with, various synthetic strategies and attributes of ZnO 2D nanosheets are discussed, followed by focusing on methodologies and reaction mechanisms. Then, their deliberation toward batteries, supercapacitors, electronics/optoelectronics, photocatalysis, sensing, and piezoelectronic platforms are further discussed. Finally, the challenges and future opportunities are featured based on its current development.     

One-dimensional ZnO nanostructures: Solution growth and functional properties

One-dimensional (1D) ZnO nanostructures have been studied intensively and extensively over the last decade not only for their remarkable chemical and physical properties, but also for their current and future diverse technological applications. This article gives a comprehensive overview of the progress that has been made within the context of 1D ZnO nanostructures synthesized via wet chemical methods. We will cover the synthetic methodologies and corresponding growth mechanisms, different structures, doping and alloying, position-controlled growth on substrates, and finally, their functional properties as catalysts, hydrophobic surfaces, sensors, and in nanoelectronic, optical, optoelectronic, and energy harvesting devices.      

Flexible Piezoelectric ZnO–Paper Nanocomposite Strain Sensor

The fabrication of a mechanically flexible, piezoelectric nanocomposite material for strain sensing applications is reported. Nanocomposite material consisting of zinc oxide (ZnO) nanostructures embedded in a stable matrix of paper (cellulose fibers) is prepared by a solvothermal method. The applicability of this material as a strain sensor is demonstrated by studying its real‐time current response under both static and dynamic mechanical loading. The material presented highlights a novel approach to introduce flexibility into strain sensors by embedding crystalline piezoelectric material in a flexible cellulose‐based secondary matrix.     

Effects of alkali on the morphologies and photoluminescence properties of ZnO nanostructures

ZnO nanostructures were fabricated in the ethanol solution of different alkali by a surfactant-free solvothermal method. ZnO nanoparticles, nanowires and nanorods were obtained depending on the experimental conditions. The corresponding growth mechanism follows a typical self-assembly growth process. The effects of various alkalis on the structures and morphologies of ZnO nanostructures were investigated. Moreover, the photoluminescence (PL) properties of the ZnO nanostructures were studied and exhibited some new features. It is found that the surface defects should be responsible for the green emission observed in the as-prepared ZnO nanostructures. The higher the specific surface area of ZnO nanostructures, the stronger the green emission and the weaker the ultraviolet (UV) emission are.     

Synthesis of two kinds of ZnO nanostructures by vapor phase method

Radial and quasi-aligned ZnO nanorod arrays were prepared on Si(111) substrates by a simple vapor phase method using Zn and zinc acetate dihydrate (ZA) as the source materials. X-ray diffraction, field emission scanning electron microscopy, Raman scattering and photoluminescence were used to characterize the structural and optical properties of the obtained nanostructures. The growth mechanisms of the two kinds of ZnO nanostructures were discussed based on the growth conditions. The different decomposing rate of the ZA plays an important role in the initial nucleation of ZnO nanorods.     

Ultrathin ZnO nanostructures synthesized by thermal oxidation of hexagonal Zn micro/nanostructures

Ultrathin (<5 nm) ZnO nanobelts, as well as porous nanotubes/nanosheets were successfully synthesized via a very simple process: thermal oxidation of hexagonal Zn micro/nanostructures in a tube furnace in 50 sccm N2 flow. The ZnO nanobelt clusters were largely grown from the (0001) end surface of the Zn nanoprisms at 300 degrees C. The porous nanotubes and nanosheets were formed on the downstream substrate by 370-400 degrees C thermal oxidation of Zn films in low pressure. These structures are related to the anisotropic oxidation of Zn and differences of melting point between Zn and ZnO. We propose that the ultrathin nanobelts were formed in a vapor-liquid-solid process while the ultrathin nanotubes and nanosheets were formed via a vapor-solid-resublimation process. The structure of the nanostructures was characterized by transmission electron microscopy. The ultrathin mesoporous nanotubes and nanosheets have been found to possess rich surface defects. These structures may have potential applications in gas sensors, catalysts and hydrogen storage due to their large specific surface area.     

Gas sensing applications of 1D-nanostructured zinc oxide: Insights from density functional theory calculations

Gas sensor devices have traditionally comprised thin films of metal oxides, with tin oxide, zinc oxide and indium oxide being some of the most common materials employed. With the recent discovery of novel metal oxide nanostructures, sensors comprising nano-arrays or single nanostructures have shown improved performance over the thin films. The improved response of the nanostructures to different gases has been primarily attributed to the highly single crystalline surfaces as well as large surface area of the nanostructures. In this paper the properties of clean and defected quasi one-dimensional ZnO nanostructures, including hexagonal and triangular nanowires, nanotubes and facetted nanotubes are reviewed. The adsorption of atoms and molecules on the ZnO nanostructures are also reviewed and the findings are compared to studies examining similar reactions on nanostructured metal oxide surfaces for sensing purposes. While both experimental and theoretical approaches have been employed to examine gas sensor reactions, this review focuses on studies that employ electronic structure calculations, which primarily concentrate on using density functional theory. Computational studies have been useful in elucidating the reaction mechanism, binding strength, charge transfer as well as other electronic and structural properties of the nanomaterials and the gas-sensor interaction. Despite these studies there are still significant areas of research that need to be pursued that will assist in the link between theoretical and experimental findings, as well as advancing the current chemical and physical understanding of these novel materials. A summary and outlook for future directions of this exciting area of research is also provided.     

Hydrothermal growth of symmetrical ZnO nanorod arrays on nanosheets for gas sensing applications

The hierarchical ZnO nanostructures with 2-fold symmetrical nanorod arrays on zinc aluminum carbonate (ZnAl-CO₃) nanosheets have been successfully synthesized through a two-step hydrothermal process. The primary nanosheets, which serve as the lattice-matched substrate for the self-assembly nanorod arrays at the second-step of the hydrothermal route, have been synthesized by using a template of anodic aluminum oxide (AAO). The as-prepared samples were characterized by XRD, FESEM, TEM and SAED. The nanorods have a diameter of about 100 nm and a length of about 2 μm. A growth mechanism was proposed according to the experimental results. The gas sensor fabricated from ZnO nanorod arrays showed a high sensitivity to ethanol at 230°C. In addition, the response mechanism of the sensors has also been discussed according to the transient response of the gas sensors.     

Preparation and characterization of ZnO/ZnS core/shell nanocomposites through a simple chemical method

In this paper, we reported the preparation of ZnO/ZnS core/shell nanocomposites by sulfidation of ZnO nanostructures via a simple hydrothermal method. The precursors of bare ZnO nanoparticles and ZnO nanorods were synthesized by a surfactant-assisted hydrothermal growth. The structural, morphological, and element compositional analysis of bare ZnO nanostructures and ZnO/ZnS core/shell nanocomposites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy techniques. The XRD results indicated that the phase of bare ZnO nanoparticles and ZnO nanorods was wurtzite structure, and the phase of coated ZnS nanoparticles on the surface of bare ZnO nanostructures was sphalerite structure with the size of about 8 nm. Photoluminescence measurement was carried out, and the PL spectra of ZnO/ZnS core/shell nanocomposites revealed an enhanced UV emission and a passivated orange emission compared to that of bare ZnO nanostructures. In addition, the growth mechanism of ZnO/ZnS core/shell nanostructures through hydrothermal method was preliminarily discussed.     

利用纳米ZnO粉制备厚膜气敏传感器的研究

以ZnO纳米粉(平均粒径30nm)为原料,利用水热热压方法制备了ZnO多孔纳米固体,同时用通常的水热法对ZnO纳米粉进行了预处理(预处理ZnO纳米粉)。然后,分别以ZnO多孔纳米固体和预处理ZnO纳米粉为原料,制备了厚膜气敏传感器。本征电阻的测试结果表明,这两种厚膜气敏传感器的本征电阻比用未经处理的ZnO纳米粉(以下简称“原料ZnO纳米粉”)制备的厚膜气敏传感器大大降低并很快达到稳定状态。有效地改善了器件工作的稳定性。结合对三种传感器的显微结构分析,对出现上述差异的原因进行了讨论。     

Rapid chemical synthesis and optical properties of ZnO ellipsoidal nanostructures

ZnO ellipsoidal nanostructures were rapidly synthesized using a chemical synthesis method at 90 °C without the assistance of aging procedure, calcination, sonication, microwave, laser or any organic additives. The effects of pH values and Zn²⁺ concentration on the morphologies of ZnO nanostructures were investigated. The instantaneous underdeveloped ZnO nanostructures were successfully obtained by using the electrophoretic deposition (EPD). Based on the experimental results, growth mechanism of ellipsoidal ZnO nanostructures was proposed. The ellipsoidal nanostructures are self-assembled by the oriented-attachment growth of primary nanoparticles, involving the end-to-end oriented-attachment along the major axis and the side-by-side oriented-attachment along the minor axis. Two half-ellipsoids of the ZnO nanostructures germinate in sequence. The UV–vis absorption and photoluminescence of the ellipsoidal nanostructures was also studied. This work presents a simple and ultra-fast route for large-scale fabrication of ZnO ellipsoidal nanostructures.