Highly sensitive and selective ethanol sensors based on flower-like ZnO nanorods

A simple and easy hydrothermal process has been employed to synthesize flower-like ZnO products consisting of numerous orderly oriented and bundled nanorods.The structure and morphology of the novel ZnO structure are characterized in detail.The flower-like ZnO-nanorod-based gas sensors are investigated for their ethanoi-sensing properties,and the results reveal that the sensors exhibit a high response of 143.6 to 1000 ppm ethanol and good selectivity at the optimal operating temperature of 250℃.The effect of the flower-like morphology on the response of the gas sensors to ethanol is also investigated.     

利用改进的水热法调控制备垂直对准的氧化锌纳米线阵列

Well-aligned ZnO nanowires were hydrothermally synthesized based on a facile method for preparing the ZnO seed layer which was derived from the combination of a sol-gel process and the spin-coating technique. The effect of the contents of growth solution and the growth duration on the morphology of ZnO nanowires has been investigated.The results indicated that long and vertically aligned ZnO nanowires could be obtained by adjusting the contents of ammonia and polyethyleneimine(PEI) in the growth solution.Under the optimized condition,the length of ZnO nanowires increased fast and almost linearly with the growth duration.After 10 h incubation,ZnO nanowires more than 25μm in length were obtained.By combining the conventional photolithographic method with this hydrothermal approach,long and well-aligned ZnO nanowire arrays were selectively grown on the substrate.In addition,the bottom fusion at the foot of the nanowires has been obviously improved.The results demonstrated that the improved hydrothermal process is favorable to synthesize long and well-aligned ZnO nanowires,and possesses good process compatibility with the conventional photolithographic technique for preparing ZnO nanowire arrays. So it has great potential in applications such as display and field emission devices.     

Solar light assisted photocatalysis of water using a zinc oxide semiconductor

The photocatalytic decomposition of an eco-persistent AO7 dye with sunlight in an oxygenated aqueous suspension has been studied under a nano-crystalline hexagonal ZnO photocatalyst.The effect of substrate temperature on the structural,morphological and photoactive properties has been investigated.The degradation of the A07 dye is achieved using a photoelectrochemical reactor module equipped with ZnO synthesized electrodes. Kinetic parameters have been investigated in terms of a first order rate equation.The rate constant for this heterogeneous photocatalysis was evaluated as a function of the initial concentration of original species.A substantial reduction in A07 dye is achieved as analyzed from COD and TOC studies.The mechanism for the degradation could be explained on the basis of the Langmuir-Hinshelwood mechanism.     

Synthesis and characterization of ZnO-CuO nanocomposites powder by modified perfume spray pyrolysis method and its antimicrobial investigation

Pure ZnO,ZnO-CuO nanocomposites can be synthesized by using a modified perfume spray pyrolysis method (MSP).The crystallite size of the nanoparticles (NPs) has been observed by X-ray diffraction pattern and is nearly 36 nm.Morphological studies have been analyzed by using Field Emission Scanning Electron Microscopy (FESEM) and its elemental analysis was reported by Elemental X-ray Analysis (EDX);these studies confirmed that ZnO and CuO have hexagonal structure and monoclinic structure respectively.Fourier Transform Infrared (FTIR) spectra revealed that the presence of functional frequencies of ZnO and CuO were observed at 443 and 616 cm-1.The average bandgap value at 3.25 eV using UV-vis spectra for the entitled composite has described a blue shift that has been observed here.The antibacterial study against both gram positive and negative bacteria has been studied by the disc diffusion method.To the best of our knowledge,it is the first report on ZnO-CuO nanocomposite synthesized by a modified perfume spray pyrolysis method.     

氧化锌纳米线在FTO玻璃上的合成生长及其在染料敏化太阳电池中的应用

Long and well-aligned ZnO nanowires were hydrothermally synthesized on FTO glass based on a ZnO seed layer which was prepared by spin-coating and annealing techniques.The effect of the growth solution refreshment on the morphology of ZnO nanowires was investigated and the possible mechanism was discussed.After refreshing the growth solution for 5 cycles,ZnO nanowires of ~ 120 nm in diameter and ~ 20 /μm in length were obtained.The prepared ZnO nanowires were used as photoelectrodes in dye-sensitized solar cells(DSSCs),showing excellent photovoltaic performance.With the increase of growth cycles of ZnO nanowires,the photocurrent of DSSCs increased obviously due to the increased dye loading on the surface of ZnO nanowires.The results indicated that the lone and well-aligned ZnO nanowires are promising for DSSCs application.     

P-type ZnO thin films prepared by in situ oxidation of DC sputtered Zn3N2:Ga

The feasibility of a new fabrication route for N and Ga codoped p-type ZnO thin films on glass substrates, consisting of DC sputtering deposition of Zn3N2:Ga precursors followed by in situ oxidation in high purity oxygen, has been studied. The effects of oxidation temperature on the structural, optical and electrical properties of the samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical transmittance and Hall effect measurements. The results were compared to a control film without Ga. XRD analyses revealed that the Zn3N2 films entirely transformed into ZnO films after annealing Zn3N2 films in oxygen over 500 ℃ for 2 h. Hall effect measurements confirmed p-type conduction in N and Ga codoped ZnO films with a low resistivity of 19.8 Ω?cm, a high hole concentration of 4.6E18 cm3 and a Hall mobility of 0.7 cm2/(V s). These results demonstrate a promising approach to fabricate low resistivity p-type ZnO with high hole concentration.     

Effects of Annealing Temperature on Properties of ZnO Thin Films Grown by Pulsed Laser Deposition

ZnO thin films are deposited on n-Si（111） substrates by pulsed laser deposition（PLD） system. Then the samples are annealed at different temperatures in air ambient and their properties are investigated particularly as a function of annealing temperature. The microstructure, morphology and optical properties of the as-grown ZnO films are studied by X-ray diffraetion（XRD）. atomic force mieroseope（AFM）, Fourier transform infrared spectroscopy（FTIR） and photoluminescence（PL） spectra. The results show that the as- grown ZnO films have a hexagonal wurtzite structure with a preferred c-axis orientation. Moreover, the diameters of the ZnO crystallites become larger and the crystal quality of the ZnO fihns is improved with the increase of annealing temperature.     

Influence of growth time on crystalline structure,conductivity and optical properties of ZnO thin films

This paper examines the growth of ZnO thin films on glass substrate at 350℃using an ultrasonic spray technique.We have investigated the influence of growth time ranging from 1 to 4 min on structural,optical and electrical properties of ZnO thin films.The as-grown films exhibit a hexagonal structure wurtzite and are(002) oriented.The maximum value of grain size G = 63.99 nm is attained for ZnO films grown at 2 min.The average transmittance is about 80%,thus the films are transparent in the visible region.The optical gap energy is found to increase from 3.26 to 3.37 eV with growth time increased from 1 to 2 min.The minimum value of electrical resistivity of the films is 0.13Ω·cm obtained at 2 min.A systematic study on the influence of growth time on the properties of ZnO thin films deposited by ultrasonic spray at 350℃has been reported.     

Influence of growth time on crystalline structure, conductivity and optical properties of ZnO thin films

This paper examines the growth of ZnO thin films on glass substrate at 350 ℃ using an ultrasonic spray technique. We have investigated the influence of growth time ranging from 1 to 4 min on structural, optical and electrical properties of ZnO thin films. The as-grown films exhibit a hexagonal structure wurtzite and are (002) oriented. The maximum value of grain size G = 63.99 nm is attained for ZnO films grown at 2 min. The average transmittance is about 80%, thus the films are transparent in the visible region. The optical gap energy is found to increase from 3.26 to 3.37 eV with growth time increased from 1 to 2 min. The minimum value of electrical resistivity of the films is 0.13 Ω·cm obtained at 2 min. A systematic study on the influence of growth time on the properties of ZnO thin films deposited by ultrasonic spray at 350 ℃ has been reported.     

Effect of Fe-doping on the structural and optical properties of ZnO thin films prepared by spray pyrolysis

Fe-doped ZnO thin films have been prepared by spray pyrolysis on glass substrates and the influence of Fe-doping concentration on the structural and optical properties of the films has been studied.The X-ray diffraction (XRD) analysis shows that Fe doping has a significant effect on crystalline quality,grain size and strain in the thin films.The best crystalline structure is obtained for 3 at%Fe doping as observed from scanning electron microscopy (SEM) and XRD.However,lower or higher Fe-doping degrades the crystalline quality in turn.Moreover,UV spectroscopy demonstrates the influence of Fe-incorporation on visible range transmittance of ZnO where the best transmittance is obtained for 3 at%doping.The results have been illustrated simultaneously focusing previous results obtained from literature.     

一种芯片内部稳压电源的实现

介绍和分析了一种用于PWM控制器内部的稳压电路,采用双极线路结构和4μm工艺。经过PSPICE仿真,它具有0．176mV／V的稳压系数和60dB的纹波抑制比和较低温度系数。     

一年之间，物换星移

去年的这个时候,供货商们还在为生存而挣扎。如今,2009年的年报已经公布,许多供应商的年报业绩之好,就连最乐观的分析师也始料未及。这种变化的原因很简单：供应商们大幅削减成本,接下来是强劲的需求,这又导致了随后高企的设备利用率。     

Building a in a flash supercomputer

A flash mob is a group of strangers, organized over the Internet, that comes together briefly, acts out a predetermined scenario-often something as simple as clapping for 30 seconds-and then disperses. A supercomputer is a very fast and powerful computer that outperforms most mainframes, at a cost, typically, of millions of dollars. Can a flash mob build a supercomputer? It can sure try, and so it did on 3 April at the University of San Francisco's Koret athletic center. The goal was to run the Linpack benchmark, a standard method of assessing the speed of supercomputers, to achieve a speed of at least 403 gigaflops (billion floating point operations per second). This would be fast enough to earn the system a place on the list of the world's fastest 500 supercomputers. The goal was not reached. The group reached just 180 gigaflops before it was time to pack up the computers and go home. However, even though the San Francisco effort fell short of speed goal, it did ignite imaginations.     

On a wing and a prayer

Aircraft giants Boeing and Airbus are pinning their hopes on very different visions of how air travel will evolve in the coming decade.     

Converting a Display Screen into a Touchscreen

A method is presented to convert any display screen into a touchscreen by using a pair of cameras. Most state of art touchscreens make use of special touch-sensitive hardware or depend on infrared sensors in various configurations. We describe a novel computer-vision-based method that can robustly identify fingertips and detect touch with a precision of a few millimeters above the screen. In our system, the two cameras capture the display screen image simultaneously. Users can interact with a computer by the fingertip on the display screen. We have two important contributions: first, we develop a simple and robust hand detection method based on predicted images. Second, we determine whether a physical touch takes places by the homography of the two cameras. In this system, the appearance of the display screen in camera images is inherently predictable from the computer output images. Therefore, we can compute the predicted images and extract human hand precisely by simply subtracting the predicted images from captured images.     

Cooperative control of a human and a robot manipulator for positioning a cart on a frictionless plane

Robots may be expected to execute some tasks in cooperation with humans. Control systems for such robots should be appropriate to adapt to human characteristics in order to successfully accomplish the task. Pushing a cart on a frictionless plane in cooperation with a human is a basic example to such a task. To control the motion of an object from one point to another on a frictionless plane is impossible by only pushing in one direction without supporting it in the opposite direction, since as soon as the force is applied, the object will move without stopping its motion. In this paper, compliant cooperative positioning of a cart on a frictionless plane by a human and a manipulator is proposed using impedance control method with the parameters obtained from human–human cooperation.     

利用悬臂梁将均匀周期光纤光栅变为啁啾光纤光栅

利用均质、等厚及等腰梯形的悬臂梁,对刚性粘贴其表面的光纤光栅的布喇格反射中心波长在1557．68～1564．2nm范围内进行了线性调谐,同时带宽为外0.52nm的均匀周期的光纤光栅被调谐成带宽为2．52nm的啁啾光栅,且啁啾量可调。随着带宽的增加,反射谱的峰值功率呈减弱的趋势。     

量子点中极化子性质:压缩态变分法

利用单模压缩态变分法得到了在电子-体纵光学声子全耦合条件下抛物量子点极化子的基态能量及电子周围平均声子数的表达式。所采用的变分方法是基于逐次正则变换的变分方法,变换处理了包含经常被忽略的声子产生湮灭算符的双线性项。在电子-体纵光学声子全耦合条件下,讨论了受限长度与抛物量子点极化子的基态能量及电子周围平均声子数之间的依赖关系。