Ag/ZnO纳米结构的荧光增强效应

利用化学合成方法制备了Ag纳米线和ZnO量子点。对这两种纳米结构的表面形貌、晶体结构和光学性质分别进行了研究。结果表明：Ag纳米线和ZnO量子点均为单晶结构,平均直径分别为160 nm和5 nm左右。将Ag纳米线混入ZnO量子点可以使其紫外荧光显著增强,其中位于345 nm和383 nm 的荧光分别增强30倍和12倍。这与Ag纳米线和ZnO量子点混合体系的局域表面等离子体共振耦合吸收峰位相一致,说明该体系存在两种共振耦合模式。该研究结果为将来开发ZnO基纳米发光器件提供了一条新的途径。     

ZnO纳米墙的电化学沉积法制备及紫外探测性能分析

以硝酸锌水溶液作为电沉积液,采用电化学沉积法制备了氧化锌(ZnO)纳米墙,研究了沉积电压对其表面形貌、晶体结构、拉曼光谱、光致发光谱、透过率以及紫外探测性能的影响。实验结果表明,该方法制备的ZnO纳米墙的均匀性较好,具有纤锌矿结构,沿(002)晶面择优生长,有较明显的E_2(high)模峰,在394 nm处有较强烈的紫外激发峰。紫外探测实验表明:在紫外光照射下,ZnO纳米墙的光电流迅速达到饱和,当沉积电压为1.6 V时,ZnO纳米墙的光电流值最大,对应的响应时间和恢复时间分别为1.36 s和2.23 s;当测试偏压为5 V时,光暗电流比为38.96,光电响应度为0.611 A/W。     

Pd颗粒表面修饰ZnO纳米线阵列的制备及其气敏特性

采用化学气相沉积(CVD)方法在SiO_2/Si衬底生长了ZnO纳米线阵列,纳米线长约为15μm,直径为100~500 nm。通过改变溅射沉积时间(0~150 s),在ZnO纳米线表面包覆了不同厚度的Pd薄膜。在Ar气氛中,经800℃高温退火后,制备出Pd颗粒表面修饰的ZnO纳米线阵列并对其进行了气敏测试。对于乙醇而言,所有传感器最佳工作温度均为280℃。溅射时间的增加(3~10 s)导致ZnO纳米线表面Pd纳米颗粒数量及尺寸增加,传感器响应值由2.0增至3.6。过长的溅射时间(30~150 s)将导致Pd颗粒尺寸急剧增大甚至形成连续膜,传感器响应度显著降低。所有传感器对H2均表现出相对较好的选择性,传感器具有较好的响应-恢复特性和稳定性。最后,探讨了Pd颗粒表面修饰对ZnO纳米线阵列气敏传感器气敏特性的影响机制。     

ZnO肖特基势垒紫外探测器

以p-Si(111)为衬底,用水热法首次制得六棱微管ZnO。并以此为有源区利用平面磁控溅射技术沉积得到Ag叉指状电报,从而制作了Ag／n-ZnO肖特基势垒结紫外探测器。对该紫外光探测器的暗电流和365nm波长光照下的光电流、光响应和量子效率进行了测试。测试结果表明：Ag和ZnO六棱管间已形成肖特基接触．其有效势垒高度为0．35eV。无光照时,暗电流很小,当用λ=365nm的光照射Ag/n-ZnO肖特基结时．在5．9V偏压时,光生电流分别为25．6,57．9μA。Ag／n-ZnO紫外探测器有明显的光响应特性和较高的量子效率,在366nm波长处,光响应度达到最大值0．161A／W,量子效率为54．7％。     

有机-ZnO纳米线混合光电二极管特性

采用水热法制备了1维ZnO纳米线,并通过改变ZnO纳米线的取向（横向和竖直）和不同的P型半导体材料,制备了不同的有机-ZnO纳米线混合光电二极管。通过改变光照与非光照的条件下并在光照条件下改变光电二极管与光源的距离,对所制备的光电二极管的相关特性进行研究。结果表明:采用水热技术能够制备高质量的ZnO纳米线;当光电二极管两端通正向电压时,光照时的电流大于非光照时的电流,当通反向电压时,结果则相反;同时,光电流还与光照强度有关,光照强度越大,光电流越大。     

高分子软模板法自组装生长ZnO纳米线及其光学性能

采用自组装技术,利用均聚极性高分子(聚丙烯酰胺、聚乙烯醇等)长分子链作为自组装模板在半导体硅衬底上自组装生长出ZnO纳米线。采用扫描电镜(FE-SEM)和透射电镜(HRTEM)对样品的表面形貌和结构分析表征的结果表明,ZnO纳米线直径约50~80nm、长度大于4μm,具有六方纤锌矿单晶结构,且沿c轴方向择优取向生长。采用室温下光致发光(PL)谱和紫外吸收(UV)光谱对制得的ZnO纳米线的光学性能研究表明,其PL光谱上有较强的紫外发射和较弱的蓝光发射,UV吸收光谱表明样品在紫外区有强的宽带吸收,且随着纳米线粒径的减小,吸收峰出现了蓝移现象。研究探讨了高分子诱导ZnO纳米线自组装定向生长机制、发光机理及其与工艺条件的内在联系。     

青霉胺稳定的铜/银双金属纳米簇制备及其在银离子检测中的应用EI北大核心CSCD

以青霉胺(DPA)为还原剂和稳定剂,通过一锅法一步制备了青霉胺稳定的铜/银双金属纳米簇(DPA-Cu/Ag NCs),并将其作为一种传感器用于检测水样中的银离子。该银离子传感器具有价格低廉、分析速度快速、选择性高等特点。采用透射电子显微镜(TEM)等方法表征了DPA-Cu/Ag NCs的结构及其化学组成,并通过荧光光谱和紫外-可见光谱法研究了DPA-Cu/Ag NCs的光学性质。结果表明,该DPA-Cu/Ag NCs在激发波长为300 nm时的最大发射波长为555 nm,其溶液在可见光照射下呈现乳白色,在紫外灯照射下则呈现出明亮的黄色荧光。在DPA-Cu/Ag NCs的制备条件达到最优化的情况下,可以将其作为探针,用来高选择性、高灵敏性地检测银离子。该探针检测银离子的检测限为0.3μmol/L,线性范围为0~500μmol/L。该DPA-Cu/Ag NCs探针还可应用于自然环境水样(湖水、瓶装矿泉水和实验室自来水)中银离子浓度的检测,其检测性能十分优异且具有良好的准确度和重现性,表明DPA-Cu/Ag NCs探针在环境检测方面有非常高的应用价值。     

ZnO纳米线二极管发光器件制备及特性研究

运用液相法生长成ZnO纳米线薄膜,并利用肖特基型异质结的发光原理,构造成功肖特基型ZnO纳米线二极管发光器件.在大于6V直流电压驱动下,观察到近紫外波段392nm处和可见光波段525nm的发射谱带.从单向导电特性及ZnO纳米线材料的能带结构等方面探讨了该种器件的电致发光机理. 关键词： ZnO纳米线 肖特基二极管 电致发光     

五边形截面的Ag纳米线局域表面等离子体共振模式

五边形截面的单晶Ag纳米线对ZnO量子点荧光具有增强的现象. 为解释这一现象, 利用时域有限差分法对五边形截面的Ag纳米线的局域表面等离子体共振模式进行了理论模拟. 结果表明, 五边形截面的Ag纳米线在紫外区域存在两个消光峰, 分别由Ag纳米线的横向偶极共振(340 nm)和四极共振(375 nm)引起; 这两个消光峰与ZnO量子点荧光增强峰相一致, 而且随着Ag纳米线的半径增大而红移; 消光峰对应的共振模式取决于Ag纳米线的截面形状; 根据Ag纳米线电场增强倍数与激发光波长变化关系曲线可知, 最大增强电场位于五边形截面的顶点处, 而边线处电场增强较小. 理论模拟的结果较好地解释了Ag纳米线/ZnO量子点体系的荧光增强现象, 也为Ag纳米线在提高半导体材料发光效率、生物探测等方面的应用提供有益的参考.     

片上制备横向结构ZnO纳米线阵列紫外探测器件

将纳米技术与传统的微电子工艺相结合, 片上制备了横向结构氧化锌(ZnO)纳米线阵列紫外探测器件, 纳米线由水热法直接自组织横向生长于叉指电极之间, 再除去斜向的多余纳米线, 其余工艺步骤与传统工艺相同. 分别尝试了铬(Cr)和金(Au)两种金属电极的器件结构: 由于Cr电极对其上纵向生长的纳米线有抑制作用, 导致横向生长纳米线长度可到达对侧电极, 光电响应方式为受表面氧离子吸附控制的光电导效应, 光电流大但增益低, 响应速度慢, 经二次电极加固, 纳米线根部与电极金属直接形成肖特基接触, 光电响应方式变为光伏效应, 增益和速度得到了极大改善; 由于Au电极对其上纵向生长的纳米线有催化作用, 导致溶质资源的竞争, 相同时间内横向生长的纳米线不能到达对侧, 而是交叉桥接, 但却形成了紫外光诱导的纳米线间势垒结高度调控机理, 得到的器件特性为最优, 在波长为365 nm的20 mW/cm²紫外光照下, 1 V电压时暗电流为10^-9 A, 光增益可达8×10⁵, 响应时间和恢复时间分别为1.1 s和1.3 s.     

Aligned growth of ZnO nanowires by NAPLD and their optical characterizations

Not only vertically aligned ZnO nanowires but also horizontally aligned ZnO nanowires have been successfully grown on the annealed (0 0 0 1) c-cut and (1 1 2 0) a-cut sapphire substrates, respectively using catalyst-free nanoparticle-assisted pulsed-laser ablation deposition (NAPLD). The as-synthesized ZnO nanowires exhibit an ultraviolet emission at around 390 nm and the absent green emission under room temperature. The single ZnO nanowire was collected in the electrode gap by dielectrophoresis (DEP). Under the optical pumping, the single ZnO nanowire exhibited UV emission at around 390 nm with several sharp peaks whose energy spacings are almost constant, which greatly differs from the broad UV emission of the film with many nanowires, suggesting ZnO nanowires as candidates for laser media. The single ZnO nanowire showed polarized photoluminescence (PL). The as-synthesized ZnO nanowires could find many interesting applications in short-wavelength light-emitting diode (LED), laser diode and gas sensor.     

Low-temperature growth and ethanol-sensing characteristics of quasi-one-dimensional ZnO nanostructures

ZnO nanorods, nanobelts, nanowires, and tetrapod nanowires were synthesized via thermal evaporation of Zn powder at temperatures in the range 550-600 °C under flow of Ar or Ar/O₂ as carrier gas. Uniform ZnO nanowires with diameter 15-25 nm and tetrapod nanowires with diameter 30-50 nm were obtained by strictly controlling the evaporation process. Our experimental results revealed that the concentration of O₂ in the carrier gas was a key factor to control the morphology of ZnO nanostructures. The gas sensors fabricated from quasi-one-dimensional (Q1D) ZnO nanostructures exhibited a good performance. The sensor response to 500 ppm ethanol was up to about 5.3 at the operating temperature 300 °C. Both response and recovery times were less than 20 s. The gas-sensing mechanism of the ZnO nanostructures is also discussed and their potential application is indicated accordingly.     

A rapid synthesis/growth process producing massive ZnO nanowires for humidity and gas sensing

We report a rapid and simple process to massively synthesize/grow ZnO nanowires capable of manufacturing massive humidity/gas sensors. The process utilizing a chemical solution deposition with an annealing process (heating in vacuum without gas) is capable of producing ZnO nanowires within an hour. Through depositing the ZnO nanowires on the top of a Pt-interdigitated-electrode/SiO₂/Si-Wafer, a humidity/gas-hybrid sensor is fabricated. The humidity sensitivity (i.e., ratio of the electrical resistance of the sensor at 11–95 % relative humidity level) is approximately 10⁴. The response and recovery time with the humidity changing from 11 to 95 % directly and reversely is 6 and 10 s, respectively. The gas sensitivity (i.e., ratio of electrical resistance of the sensor under the air to vaporized ethanol) is increased from 2 to 56 when the concentration of the ethanol is increased from 40 to 600 ppm. Both the response and recovery times are less than 15 s for the gas sensor. These results show the sensor utilizing the nanowires exhibits excellent humidity and gas sensing.     

退火处理对ZnO纳米线紫外探测器性能的改善

通过介电泳方法定向排列了ZnO纳米线,制作了自组装有序的纳米线紫外探测器.为了适合在金叉指电极上排列,用水热方法设计生长了超长的ZnO纳米线,并通过700℃的热退火处理,使得可利用的表面缺陷增多.通过研究器件的光致发光光谱和光响应,发现光、暗电流比和响应恢复时间有显著提高,并分析了其中可能的机理.     

Fabrication of ZnO nanowires through thermal heating of metallic Zn by solar energy

ZnO nanowires were synthesized in a short time of a few seconds through a simple thermal evaporation of Zn powder using solar energy under air atmosphere. The Zn powder was heated by focusing sunlight on the Zn powder employing a magnifying lens. This strategy heated Zn to its evaporation temperature resulting in its oxidation in air. This procedure formed ZnO nanowires of ∼10 nm diameter and ∼2 μm length. As only Zn powder without any catalysts was used as the source material, it is suggested that the growth of the nanowires occurs through a vapor-solid mechanism. The cathodoluminescence (CL) spectrum from such ZnO nanowires showed strong ultraviolet emission indicating their highly crystalline quality besides good optical properties.     

Ammonia sensing characteristics of ZnO nanowires studied by quartz crystal microbalance

The ZnO nanowires have been prepared and studied as the sensing element for the detection of ammonia. The ZnO nanowires were first synthesized by evaporating high purity zinc pellets at 900 °C and then distributed onto the electrode surfaces of quartz crystals at room temperatures. Gas sensitive properties of ZnO nanowires layer were studied in terms of the quartz crystal microbalance (QCM) at room temperature. It is found that the obtained response of the sensors varied with the thickness of the ZnO nanowires layer. ZnO nanowires showed high sensitivity to ammonia in the range of 40-1000 ppm. The response time of the sensor was as fast as ∼5 s at any concentration (40-1000 ppm) of ammonia gas. The ZnO nanowires-coated sensors have a good frequency stability and reproducibility. All results demonstrated that the ZnO nanowire was a potential gas sensing material for practical use.     

Synthesis of ZnO nanowires on aluminum flake by aqueous method

ZnO nanowires are grown on aluminum flake at low temperature by using a simple aqueous solution method. X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscope (TEM) are applied to determine the as-grown ZnO nanowires morphology and crystal structures. The results show that the ZnO nanowires have wurtzite structure, and the diameter and length of the nanowire are 30 nm and more than 1.5 μm, respectively. Photoluminescence spectroscopy (PL) and Raman spectrum reveal the nanowires have good optical properties with low tensile stress. Meanwhile, photoelectrochemical cell (PEC) study verifies that ZnO nanowires as photoanodes are relatively stable in the photo-oxidation process, which could be a promising technique for practical applications.     

锡催化剂助生长法制备孪晶ZnO纳米线及其结构表征

用SnO和Zn的均匀混合物在高温下共烧通过VLS机制制备出孪晶ZnO纳米线的均匀结构。SEM图像显示孪晶ZnO纳米线的直径在100~200nm之间,长度在几十微米到几百微米之间的范围内,有的甚至达到了毫米级,产率也非常的高。TEM图像中ZnO孪晶纳米线顶端的金属Sn颗粒表明了孪晶结构的Sn催化生长。高分辨电子图谱显示了氧化锌纳米线孪晶结构的特征。电子衍射分析发现孪晶氧化锌的晶带轴的方向是[0110],孪晶面为(1013),并且通过明场像和暗场像分析了孪晶纳米线的晶格关系,确定了孪晶纳米线的汽-液-固(VLS)生长机制。