Photoelectric Cooperative Induced Wetting on Aligned‐Nanopore Arrays for Liquid Reprography

Surface wettability as a response to the cooperation of different stimuli has been intensively studied and provides more advantages than as a response to a single stimulus. Recently, we demonstrated the patterned wettability transition from the Cassie to the Wenzel state on a superhydrophobic aligned‐ZnO‐nanorod array surface via a photoelectric cooperative wetting process. However, the specific aligned‐nanorod array structure of such devices is easily damaged due to their low mechanical strength and cannot sustain multiple transfer printing. Meanwhile, the patterned wetting process is not easily controlled due to the air‐permeable structure of adjacent nanorods. As a result, in practice, it is difficult to apply liquid reprography on such a nanostructure. Here, we demonstrate photoelectric cooperative induced patterned wetting on the superhydrophobic aligned‐nanopore array surface of TiO₂‐coated nanoporous AAO film, which has a high mechanical strength and excellent controllability. Liquid reprography is achieved through the patterned wetting process on the superhydrophobic aligned‐nanopore array surface, which is a new progression in liquid reprography, and is promising for gearing up the application of photoelectric cooperative liquid reprography.     

ZnO纳米棒薄膜光学性能的系统研究

采用简化的种子层制备工艺在ITO基底上制备了ZnO种子层,并使用化学溶液沉积法制备了高度取向的ZnO纳米棒阵列。采用XRD和SEM对ZnO纳米棒的结构和形貌进行表征,并对样品的光学性能进行了测试。测试结果表明,所制备的ZnO纳米棒为c轴择优取向的六角纤锌矿结构,直径为66~122nm可控,且排列紧密,形貌规整。光学性能测试结果表明,吸收光谱在375nm附近表现出强烈的紫外吸收边是由于禁带边吸收引起的;反射光谱具有一定的周期振荡性,可用于薄膜厚度的估算;光致发光谱在378nm附近有很强的紫外发射峰;增大生长液浓度和高温退火可降低缺陷发光,改善结晶质量。     

Phototunable Underwater Oil Adhesion of Micro/Nanoscale Hierarchical‐Structured ZnO Mesh Films with Switchable Contact Mode

Controllable surface adhesion of solid substrates has aroused great interest both in air and underwater in solving many challenging interfacial science problems such as robust antifouling, oil‐repellent, and highly efficient oil/water separation materials. Recently, responsive surface adhesion, especially switchable adhesion, under external stimulus in air has been paid more and more attention in fundamental research and industrial applications. However, phototunable underwater oil adhesion is still a challenge. Here, an approach to realize phototunable underwater oil adhesion on aligned ZnO nanorod array‐coated films is reported, via a special switchable contact mode between an unstable liquid/gas/solid tri‐phase contact mode and stable liquid/liquid/solid tri‐phase contact mode. The photo‐induced wettability transition to water and air exists (or does not) in the micro/nanoscale hierarchical structure of the mesh films, playing important role in controlling the underwater oil adhesion behavior. This work is promising in the design of novel interfacial materials and functional devices for practical applications such as photo‐induced underwater oil manipulation and release, with loss‐free oil droplet transportation.     

Effect of seed layers (Al,Ti) on optical and morphology of Fe-doped ZnO thin film nanowires grown on Si substrate via electron beam evaporation

The effects of Al and Ti seed layers were studied for undoped and Fe-doped ZnO thin films deposited on n-type Si substrates by electron beam (e-beam) evaporation. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The films grown on seed layers showed wurtzite hexagonal crystal nanorod and nanowire structures. A higher angle phase shift was observed in the doped thin films compared to the pristine ZnO films. Microstructural studies confirmed the growth of nanorods and nanowires with average widths of ~32 nm and ~8–29 nm, respectively. The nanostructures were denser and more crystalline on the Al seed layer than on the Ti seed layer for the doped thin films. However, in the undoped thin films, a more crystalline nature was observed on the Ti seeded layer than the Al seeded layer.     

用纳米棒ZnO作模板生长无支撑的AlN纳米晶

用金属有机物气相外延在纳米棒ZnO模板上沉积AlN薄膜.SEM测试表明该薄膜形成了一种倾倒纳米棒的表面.而GIXRD测试进一步证实它是纤锌矿结构的AlN,晶粒尺度约为12nm,接近于ZnO纳米棒的直径(30nm).这意味着纳米棒结构的ZnO能限制AlN的横向生长.此外,高温下用H2刻蚀ZnO直接在生长中实现了外延层的剥离.最终得到了无支撑的AlN纳米晶,完整无破损的区域约为1cm×1cm.定义这个生长机制为"生长-刻蚀-合并"过程.     

Synthesis of ZnO nanostructure films by thermal evaporation approach and their application in dye-sensitized solar cells

Zinc oxide (ZnO) films were prepared successfully by simple thermal evaporation of zinc acetate dihydrate at low temperature onto FTO (fluorine-doped tin oxide) glass substrates coated with thin ZnO seed layer. The synthetic parameter such as temperature was found to determine the morphology of nanostructures. ZnO nanorod (NR) and nanoparticle (NP) films have been synthesized at 245 and 350 °C, respectively, for 6 h. The dye-sensitized solar cells (DSSCs) were fabricated using the ZnO nanostructure films as photosensitized electrodes. A maximum photoelectric conversion efficiency (PCE) of 1.56%, and short-circuit photocurrent density of 5.12 mA/cm² were achieved with the ZnO NP-based DSSC. The PCE increase was ascribed to the reduced recombination loss and prolonged electron lifetime according to electrochemical impedance spectroscopy (EIS).     

Growth of ZnO nanocrystals by pulsed laser deposition on sapphire and silicon and the infrared spectra of the nanocrystals

The ZnO nanorods that comprise highly oriented nanorod structures are grown on sapphire and silicon substrates by laser ablation. The nanostructures grown in different conditions are characterized by means of electron microscopy and Fourier infrared reflectance spectroscopy. The contributions of optical phonons and free charge carriers to the infrared spectra of the layers of ZnO nanorods are identified, and the degree of orientation of the ZnO nanorods with respect to the substrate surface is analyzed in relation to the conditions of growth. Softening of optical phonons of ZnO with decreasing the nanorod diameter is observed.

     

ZnO纳米棒阵列提高发光二极管光抽取效率的研究

为了提高大功率LED的光抽取效率,采用溶胶-凝胶法、水热生长法的两步生长工艺在大功率红光发光二极管(LEDs)表面制作ZnO纳米棒阵列结构进行研究.利用ZnO纳米棒形成的光波导,ZnO纳米棒侧面为辅助出光面,提高了LED芯片的光输出效率.测试表明,所生长的ZnO纳米棒分布密度均匀,形貌一致;与未制作ZnO纳米棒前相比较...     

用纳米棒ZnO作模板生长无支撑的AlN纳米晶

用金属有机物气相外延在纳米棒ZnO模板上沉积AlN薄膜.SEM测试表明该薄膜形成了一种倾倒纳米棒的表面.而GIXRD测试进一步证实它是纤锌矿结构的AlN,晶粒尺度约为12nm,接近于ZnO纳米棒的直径(30nm).这意味着纳米棒结构的ZnO能限制AlN的横向生长.此外,高温下用H2刻蚀ZnO直接在生长中实现了外延层的剥离.最终得到了无支撑的AlN纳米晶,完整无破损的区域约为1cm×1cm.定义这个生长机制为"生长-刻蚀-合并"过程.     

ZnO nanorod arrays as an antireflective coating for Cu(In,Ga)Se2 thin film solar cells

A ZnO nanorod antireflective coating has been prepared on Cu(In,Ga)Se₂ thin film solar cells. This coating leads to a decrease of the weighted global reflectance of the solar cells from 8.6 to 3.5%. It boosts the solar cells short‐circuit current up to 5.7% without significant effect on their open‐circuit voltage and fill factor (FF), which is comparable to a conventional optimized single layer MgF₂ antireflective coating. The ZnO nanorod antireflective coating was electrochemically prepared from an aqueous solution at 80°C. The antireflective capability of ZnO nanorod arrays (ZNAs) may be further improved by optimization of growth conditions and their geometry. Copyright © 2010 John Wiley & Sons, Ltd.     

Molecular or Nanoscale Structures? The Deciding Factor of Surface Properties on Functionalized Poly(3,4‐ethylenedioxythiophene) Nanorod Arrays

Nanostructures of poly(3,4‐ethylenedioxythiophene) (PEDOT) are assembled by using an anodic aluminum oxide template directly fabricated on gold‐coated silicon wafers. Inside these templates, PEDOT and hydroxy functionalized PEDOT form tubes. On the other hand, alkyl‐ and perfluoro‐functionalized PEDOTs assembled as nanorods. This approach allows a platform to understand the molecular and nanostructural effect on the surface wettability of these materials. In the water/air interface, the contact angle of water droplet (CA_water) for the smooth alkyl‐functionalized PEDOT films increases when alkyl chain gets longer. In contrast, the contact angle reachs saturation at 130° with alkyl chain longer than ethyl in assembled nanorod arrays. It remains the same even in the case of perfluoro‐functionalized PEDOT. Moreover, ethyl‐functionalized PEDOT (PEDOT‐C2) nanorods displays superoleophilicity and the oil deoplet cannot stay on the film in water. Based on the wettability studies, it is concluded that the nanostructures contribute predominantly for the surface wettability of these nanomaterials when the length of alkyl chain crosses certain threshold.     

Selective growth and directed integration of ZnO nanobridge devices on si substrates without a metal catalyst using a ZnO seed layer

Directed assembly and integration of ZnO nanobridges (NBs) into working devices on Si substrates was achieved. Metal catalysts were not used, and the “harvest and disperse” method of nanorod (NR) integration was avoided. High-quality ZnO NRs were grown via a vapor-solid method selectively on a patterned thin-film ZnO seed layer. ZnO NRs exhibited a single-crystalline structure with c-axis preferred orientation, were aligned roughly perpendicular to the surface, and showed a strong intrinsic near-band edge photoluminescence peak at 380 nm with no detectable visible photoluminescence. These ZnO NRs were grown to span gaps between separated electrodes, terminate on an opposing surface, and effectively form electrically accessible vertical or horizontal ZnO NB devices. Operation of the directly grown horizontal ZnO NB devices as gas and UV sensors was performed, demonstrating a significant step toward practical large-scale integration of nanodevices into Si microelectronics.     

Effects of lanthanum and sodium on the structural,optical and hydrophilic properties of sol–gel derived ZnO films: A comparative study

The technological applications of the transparent ZnO films could be broadened via incorporation of small amounts of some special elements. In this work, the optical and surface properties of the spin coated Zn_1−xM_xO films (M=Na or La and x≤0.075) grown on glass substrates, are reported. According to X-ray diffraction (XRD) results, all films consist of a single phase with a hexagonal structure and the ZnO crystallites are preferentially oriented towards (002) direction. The plane surface of the pure ZnO film turned to be wrinkle network structure after Na and La addition. The reflectance (R%) of the films decreased after Na doping and significantly increased with increasing La content. The optical band gap of pure ZnO is 3.26 eV and red-shifted after Na and La incorporation. The dependence of the refractive index and film's wettability on the structural and morphological changes are reported. The obtained results of these two systems are compared with those of similar materials and some expected applications are explored.     

Al掺杂对ZnO纳米结构阵列的影响

采用脉冲电磁场辅助水热合成法制备了高比表面积、高能面暴露的ZnO纳米片阵列,通过场发射扫描电镜(FESEM)、X线衍射(XRD)及X线光电子能谱(XPS)等手段测试纳米结构阵列的性能。结果表明,经过Al掺杂后的ZnO纳米结构由棒状转变为六边形的片状结构,当Al的摩尔分数为1%时,纳米片彼此交错,组织均匀,垂直于衬底,与传统纳米棒相比,纳米片具有更大的比表面积及更多暴露的高能晶面,并对纳米棒向纳米片的转变机理进行了详细的分析和探讨。     

Bicolor Light-Emitting Diode Based on Zinc Oxide Nanorod Arrays and Poly(2-methoxy,5-octoxy)-1,4-phenylenevinylene

The current study reports a novel inorganic/organic light-emitting diode (LED), consisting of zinc oxide (ZnO) nanorod arrays and poly(2-methoxy, 5-octoxy)-1,4-phenylenevinylene (MOPPV). ZnO nanorod arrays passivated using polyacrylamide (PAM) with 70 nm diameter were successfully prepared by a simple polymer-assisted chemical method. Enhancement of the ZnO defect emission is caused by PAM passivation, as observed in photoluminescence spectra. Infrared absorption spectra reveal that PAM is chemically or physically adsorbed on the surfaces of ZnO nanorod arrays. The electroluminescence (EL) spectrum shows bluish light at 406 nm from ZnO transition emission, and light emission with center at 600 nm from exciton emission in MOPPV. The potential EL mechanism is electron transition to zinc vacancy in PAM/ZnO nanorod arrays, and exciton radiation luminescence in MOPPV film. This novel PAM/ZnO-MOPPV device may be helpful to promote development of multicolor LEDs.     

Low‐Temperature Growth of SnO2 Nanorod Arrays and Tunable n–p–n Sensing Response of a ZnO/SnO2 Heterojunction for Exclusive Hydrogen Sensors

Uniform SnO₂ nanorod arrays have been deposited at low temperature by plasma‐enhanced chemical vapor deposition (PECVD). ZnO surface modification is used to improve the selectivity of the SnO₂ nanorod sensor to H₂ gas. The ZnO‐modified SnO₂ nanorod sensor shows a normal n‐type response to 100 ppm CO, NH₃, and CH₄ reducing gas whereas it exhibits concentration‐dependent n–p–n transitions for its sensing response to H₂ gas. This abnormal sensing behavior can be explained by the formation of n‐ZnO/p‐Zn‐O‐Sn/n‐SnO₂ heterojunction structures. The gas sensors can be used in highly selective H₂ sensing and this study also opens up a general approach for tailoring the selectivity of gas sensors by surface modification.     

ZnO/ZnS核/壳纳米结构的形态及其演变模式

用两步生长的方法在醋酸锌和六亚甲基四胺水溶液中生长ZnO纳米棒阵列,然后以ZnO纳米棒阵列为模板,在Na2S水溶液中硫化0.5～6 h形成ZnO/ZnS纳米结构.用XRD,SEM和TEM表征了ZnO/ZnS核/壳纳米结构的晶体结构、表面形貌.研究了ZnO/ZnS核/壳纳米结构的形态及其转变的模式.在硫化过程中,ZnO首先形成ZnO/ZnS核/壳纳米棒,随着硫化程度的增强,核/壳结构顶部出现空洞,空洞扩展形成管状结构,进一步硫化,管状结构坍塌.硫化形成的ZnO/ZnS结构的形态不仅依赖于初始纳米棒的直径大小和硫化时间的长短,还依赖于纳米棒的分布密度.     

Optical properties of Zn1−xMgxO nanorods using catalysis-driven molecular beam epitaxy

We report on the optical properties of (Zn,Mg)O nanorods grown by catalyst-driven molecular beam epitaxy. The process is site-specific, as single crystal (Zn,Mg)O nanorod growth is realized via nucleation on Ag films or islands that are deposited on a SiO₂-terminated Si substrate surface. Growth occurs within a flux of Zn, Mg, and O₂/O₃ mixture at substrate temperatures of 400–500 °C. With the addition of Mg, the nanorod morphology becomes more uniform relative to the pure ZnO nanomaterials synthesized under similar conditions. The (Zn,Mg)O nanorods are cylindrical, exhibiting diameters of 15–40 nm and lengths in excess of 1 μm. The (Zn,Mg)O nanorods exhibit a strong photoluminescence response, showing a slight shift to shorter wavelengths due to Mg incorporation.     

籽晶层退火温度对ZnO纳米棒形貌及发光特性的影响

以不同退火温度处理后的ZnO籽晶层为基底,采用水热法生长了ZnO纳米棒阵列。对制备得到的ZnO纳米棒阵列的形貌、结构以及发光特性进行了表征,分析了籽晶层的退火温度对ZnO纳米棒阵列的形貌及发光性质的影响,发现通过调节籽晶层的退火温度,可以控制ZnO纳米棒的大小及密度,并发现在经400℃退火后的籽晶层上生长的ZnO纳米棒阵列形貌最佳,发光性能最优。     

紫外辐射ZnO纳米棒的生长及性能

用退火法在玻璃、硅片衬底上先生长ZnO籽晶,然后在90℃下在醋酸锌和六亚甲基四胺溶液中生长了直径约为17 nm的ZnO纳米棒.采用X射线衍射仪(XRD)分析了不同衬底上生长的ZnO纳米棒的结构和择优生长取向,用扫描电子显微镜(SEM)观察了ZnO的形态,用荧光光谱仪分析了纳米棒的发光特性,讨论了籽晶、衬底类型和衬底放置方式对纳米棒的尺寸、排列趋向性和光学性能的影响.纳米棒的直径和排列依赖于衬底的初始状态,籽晶可以减小纳米棒的尺寸,增强纳米棒的排列有序性;一旦衬底上生长了籽晶,后续生长的纳米棒的尺寸、排列和性能与衬底的类型无关,纳米棒都具有强的紫光发射.但衬底的放置方式会影响其上纳米棒的形态,竖直放置的衬底易生长尺寸分布均匀的准有序排列的纳米棒.