加热覆盖有ZnCl2溶液的锌片制备ZnO亚微米棒阵列

将表面覆盖有ZnCl2溶液的锌片加热到400 ℃反应1 h, 在锌片上生长出了ZnO亚微米棒阵列. 采用扫描电镜、透射电子显微镜和X射线衍射仪对所制备的产物进行了表征和分析. 结果表明产物为六方相纤锌矿单晶结构的ZnO亚微米棒, 其直径和长度分别为300～650 nm和6 μm, 提出了ZnO亚微米棒可能的生长机理. 在波长为300 nm光的激发下, 发现了ZnO亚微米棒阵列具有发光峰位于395 nm强的紫外光发光和位于490 nm弱的蓝绿光发光, 这两种发光分别起源于ZnO宽带隙带边发射和ZnO中相应的缺陷结构.     

Optimization of processing parameters on the controlled growth of ZnO nanorod arrays for the performance improvement of solid-state dye-sensitized solar cells

High-transparency and high quality ZnO nanorod arrays were grown on the ITO substrates by a two-step chemical bath deposition (CBD) method. The effects of processing parameters including reaction temperature (25-95 °C) and solution concentration (0.01-0.1 M) on the crystal growth, alignment, optical and electrical properties were systematically investigated. It has been found that these process parameters are critical for the growth, orientation and aspect ratio of the nanorod arrays, showing different structural and optical properties. Experimental results reveal that the hexagonal ZnO nanorod arrays prepared under reaction temperature of 95 °C and solution concentration of 0.03 M possess highest aspect ratio of ∼21, and show the well-aligned orientation and optimum optical properties. Moreover the ZnO nanorod arrays based heterojunction electrodes and the solid-state dye-sensitized solar cells (SS-DSSCs) were fabricated with an improved optoelectrical performance.     

Direct growth of comet-like superstructures of Au-ZnO submicron rod arrays by solvothermal soft chemistry process

The synthesis, characterization and proposed growth process of a new kind of comet-like Au-ZnO superstructures are described here. This Au-ZnO superstructure was directly created by a simple and mild solvothermal reaction, dissolving the reactants of zinc acetate dihydrate and hydrogen tetrachloroaurate tetrahydrate (HAuCl₄·4H₂O) in ethylenediamine and taking advantage of the lattice matching growth between definitized ZnO plane and Au plane and the natural growth habit of the ZnO rods along [001] direction in solutions. For a typical comet-like Au-ZnO superstructure, its comet head consists of one hemispherical end of a central thick ZnO rod and an outer Au-ZnO thin layer, and its comet tail consists of radially standing ZnO submicron rod arrays growing on the Au-ZnO thin layer. These ZnO rods have diameters in range of 0.2-0.5 μm, an average aspect ratio of about 10, and lengths of up to about 4 μm. The morphology, size and structure of the ZnO superstructures are dependent on the concentration of reactants and the reaction time. The HAuCl₄·4H₂O plays a key role for the solvothermal growth of the comet-like superstructure, and only are ZnO fibers obtained in absence of the HAuCl₄·4H₂O. The UV-vis absorption spectrum shows two absorptions at 365-390 nm and 480-600 nm, respectively attributing to the characteristic of the ZnO wide-band semiconductor material and the surface plasmon resonance of the Au particles.     

Hydrothermal growth of well-aligned ZnO nanorod arrays: Dependence of morphology and alignment ordering upon preparing conditions

Well-aligned ZnO nanorod arrays were prepared on substrates by hydrothermal growth under different conditions. The effect of preparing conditions on the deposition of ZnO nanorods was systematically studied by scanning electron microscopy, X-ray diffraction and photoluminescence spectroscopy. It is demonstrated that the growth conditions such as pre-treatment of the substrates, growth temperature, deposition time and the concentration of the precursors have great influence on the morphology and the alignment ordering of ZnO nanorod arrays. Pre-treatment of substrates, including dispersion of ZnO nanoparticles and subsequent annealing, not only plays a main role in governing the rod diameter, but also greatly improves the rod orientation. Although the rod diameter and its distribution are mainly determined by pre-coated ZnO nanoparticles, they can also be monitored to some extent by changing the concentration of the precursors. The growth temperature has a little influence on the orientation of nanorods but it has great impact on their aspect ratio and the photoluminescent property. Kinetic studies show that the growth of ZnO nanorods contains two distinct step: a fast steps within the first hour, in which the nanorods tend to be short and wide, and a slow step, in which long rods with high aspect ratio are obtained.     

Well Oriented ZnO Nanorods Array: Negative Resistance and Optical Switching

Well‐oriented ZnO nanorods (NRs) arrays were grown on Si, alumina, quartz, and FTO substrates through a ZnO seed layer followed by low temperature wet chemical process. The influence of sputtered ZnO seed layer thickness (100, 50, 32, and 16 nm), annealing temperature and CuO_x coverage on the characteristics of ZnO NRs were investigated in this study. The crystalline structural, chemical, morphological, optical, and electrical properties of ZnO NRs arrays were studied by X‐ray diffraction (XRD), field emission‐ scanning electron microscopy equipped by energy dispersive X‐ray spectroscopy (FE‐SEM/EDX), Raman scattering, UV/Vis ‐ near IR absorption spectroscopy and current‐voltage characteristic. XRD and Raman spectra measurement revealed that the synthesize ZnO displayed hexagonal wurtzite structure. The individual rod diameter, density, and orientation can be controlled by varying the seed layer thickness. The mean diameter and maximum length of ZnO NRs are around 55–66 nm and 282 nm, respectively. ZnO NRs/ ZnO thin film structure shows optical switching and negative differential resistance behavior as applicable to ON/OFF gate and memory devices.     

Synthesis of nano/micro zinc oxide rods and arrays by thermal evaporation approach on cylindrical shape substrate

Nano and micro ZnO rods and arrays have been synthesized by a simple thermal evaporation approach on a cylindrical shape substrate. Most of the synthesized ZnO products are single crystalline with a hexagonal structure and grow along the [0001] direction. Individual protrusive ZnO rods and well-aligned arrays are two typical products in our work. The individual protrusive ZnO rods have diameters of 25 nm approximately 2.1 microm and lengths from several hundred nanometers to 40 microm, while in the well-aligned arrays, the diameter and length of each ZnO rod range from 60 nm to 1.2 microm and from 4 microm to 6 microm, respectively. The heating temperature and deposition position are two key points to control the diameters of the rods. The growth mechanism is discussed and proposed. The perfect crystalline ZnO rods with different scales from nanometer to micrometer are good models for the investigation of the size effect of physical and chemical properties of one-dimensional material.     

The effect of hydrothermal growth temperature on preparation and photoelectrochemical performance of ZnO nanorod array films

Highly oriented ZnO nanorod arrays with controlled diameter and length, narrow size distribution and high orientation consistency have been successfully prepared on ITO substrates at different growth temperatures by using a simple hydrothermal method. XRD results indicate that the nanorods are high-quality single crystals growing along [001] direction with a high consistent orientation perpendicular to the substrate. SEM images show that the nanorods have average diameters of about 30-70 nm by changing growth temperature. The thin films consisting of ZnO nanorods with controlled orientation onto ITO substrates allow a more efficient transport and collection of photogenerated electrons through a designed path. For a sandwich-type cell, the relatively high overall solar energy conversion efficiency reaches about 2.4% when the growth temperature is at 95 °C.     

Effects of substrates and seed layers on solution growing ZnO nanorods

Oriented ZnO nanorods were fabricated in a two-step approach, including the synthesis of seed layer on different substrates and the growth of ZnO nanorods in aqueous solutions of zinc nitrate and hexamethylenetetramine at low temperature. The effects of seed layer synthesized by different methods, sol–gel method and electrochemical deposition method, on the orientation and morphologies of ZnO nanorods were compared in detail. The optimal parameters for the growth of highly oriented ZnO nanorod arrays were found and the forming mechanism was also disclosed. Furthermore, as an application of the ZnO nanorod film, dye-sensitized solar cells based on it were successfully fabricated. The cell performances of ZnO nanorods grown on ED-ZnO seed layer deposited at −700 mV were higher than those with SG-ZnO seed layer due to good nanostructure.     

Controllable synthesis and optical properties of novel ZnO cone arrays via vapor transport at low temperature

Novel ZnO cone arrays with controllable morphologies have been synthesized on silicon (100) substrates by thermal evaporation of metal Zn powder at a low temperature of 570 degrees C without a metal catalyst. Clear structure evolutions were observed using scanning electron microscopy: well-aligned ZnO nanocones, double-cones with growing head cones attached by stem cones, and cones with straight hexagonal pillar were obtained as the distance between the source and the substrates was increased. X-ray diffraction shows that all cone arrays grow along the c-axis. Raman and photoluminescence spectra reveal that the optical properties of the buffer layer between the ZnO cone arrays and the silicon substrates are better than those of the ZnO cone arrays due to high concentration of Zn in the heads of the ZnO cone arrays and higher growth temperature of the buffer layer. The growth of ZnO arrays reveals that the cone arrays are synthesized through a self-catalyzed vapor-liquid-solid (VLS) process.     

Aqueous solution fabrication of large-scale arrayed obelisk-like zinc oxide nanorods with high efficiency

Two-dimensional (2D) arrays of obelisk-like zinc oxide nanorods were successfully synthesized with high efficiency on quartz and glass substrate on a large scale through a simple aqueous solution deposition method with zinc nitrate, ammonia, and ammonium chloride as the precursors. Characterized by XRD, EDS, TEM and SEM, the as-grown zinc oxide rods had a single crystalline obelisk-like hexagonal wurtzite structure with diameters of about 300-400 nm and length up to 5 μm. Both XRD and SEM studies revealed the orientation of ZnO rods, and the orientation of ZnO rods can be controlled easily by temperature, pH of the reaction system and the concentration of reactants.     

ZnO纳米棒阵列在TiO2介孔薄膜上的生长及其表征

通过低温水热法成功地将ZnO纳米棒阵列定向生长在了介孔锐钛矿TiO2纳米晶薄膜上,并主要利用X射线衍射、场发射扫描电子显微镜和光致发光光谱等对其进行了表征。所制备的纳米棒具有六边形的端面,纳米棒的尺寸及端面边长分布范围窄,并且沿c轴方向(002)表现出了明显的择优化生长。此外,相比于玻璃基底或TiO2纳米颗粒薄膜,生长在介孔TiO2薄膜上的ZnO纳米棒阵列表现出了较好的取向生长,表明基底的表面结构和组成对ZnO纳米棒阵列的生长有显著的影响。根据基底有序的多孔结构,讨论了纳米棒阵列可能的生长机理。所得到的ZnO纳米棒阵列在室温下分别表现出了以370 nm为中心的强近紫外光和以530 nm为中心的弱绿光两条荧光谱带。     

Low-temperature growth of ZnO nanorods by chemical bath deposition

Aligned ZnO nanorod arrays were synthesized using a chemical bath deposition method at normal atmospheric pressure without any metal catalyst. A simple two-step process was developed for growing ZnO nanorods on a PET substrate at 90-95 degrees C. The ZnO seed precursor was prepared by a sol-gel reaction. ZnO nanorod arrays were fabricated on ZnO-seed-coated substrate. The ZnO seeds were indispensable for the aligned growth of ZnO nanorods. The ZnO nanorods had a length of 400-500 nm and a diameter of 25-50 nm. HR-TEM and XRD analysis confirmed that the ZnO nanorod is a single crystal with a wurtzite structure and its growth direction is [0001] (the c-axis). Photoluminescence measurements of ZnO nanorods revealed an intense ultraviolet peak at 378.3 nm (3.27 eV) at room temperature.     

Earth‐Abundant Oxygen Evolution Catalysts Coupled onto ZnO Nanowire Arrays for Efficient Photoelectrochemical Water Cleavage

ZnO has long been considered as a model UV‐driven photoanode for photoelectrochemical water splitting, but its performance has been limited by fast charge‐carrier recombination, extremely poor stability in aqueous solution, and slow kinetics of water oxidation. These issues were addressed by applying a strategy of optimization and passivation of hydrothermally grown 1D ZnO nanowire arrays. The length and diameter of bare ZnO nanowires were optimized by varying the growth time and precursor concentration to achieve optimal photoelectrochemical performance. The addition of earth‐abundant cobalt phosphate (Co‐Pi) and nickel borate (Ni‐B) oxygen evolution catalysts onto ZnO nanowires resulted in substantial cathodic shifts in onset potential to as low as about 0.3 V versus the reversible hydrogen electrode (RHE) for Ni‐B/ZnO, for which a maximum photocurrent density of 1.1 mA cm^?2 at 0.9 V (vs. RHE) with applied bias photon‐to‐current efficiency of 0.4 % and an unprecedented near‐unity incident photon‐to‐current efficiency at 370 nm. In addition the potential required for saturated photocurrent was dramatically reduced from 1.6 to 0.9 V versus RHE. Furthermore, the stability of these ZnO nanowires was significantly enhanced by using Ni‐B compared to Co‐Pi due to its superior chemical robustness, and it thus has additional functionality as a stable protecting layer on the ZnO surface. These remarkable enhancements in both photocatalytic activity and stability directly address the current severe limitations in the use of ZnO‐based photoelectrodes for water‐splitting applications, and can be applied to other photoanodes for efficient solar‐driven fuel synthesis.     

氧化锌纳米棒微结构光电极的制备

通过两步法,即首先热分解醋酸锌制备氧化锌晶种层,在晶种的诱导下,再采用低温水热法在氟掺杂的SnO₂导电玻璃(fluorine-doped tin oxide, FTO)基底导电面上成功制备出高取向性的氧化锌纳米棒阵列光电极。系统研究了前驱液浓度、溶液pH值、反应时间等实验条件对光电极微结构的影响。实验结果表明在一定变化范围内,随着前驱液浓度和溶液pH值的增大,纳米棒的直径增大;随着反应时间的延长,纳米棒的长度增长。将氧化锌纳米棒阵列薄膜制作成染料敏化太阳电池(dye-sensitized solar cell, DSSC)的光电极,并对电池的I-V特性进行了表征。     

电沉积种子层化学控制生长氧化锌纳米棒和纳米管

采用水溶液法在电沉积的ZnO种子层上制备了高度取向的ZnO纳米棒阵列,并通过碱溶液化学腐蚀法获得了ZnO纳米管。对ZnO纳米棒和纳米管的溶液生长和腐蚀过程进行了分析。结果表明,种子层的结构和性能对ZnO纳米棒有着重要的影响,在-700 mV电位下沉积的种子层薄膜均匀性好,生长的纳米棒密度大、与基底垂直性好;碱溶液对纳米棒的腐蚀具有选择性,通过控制腐蚀液的浓度和时间,可获得中空的ZnO纳米管。     

ZnO纳米棒阵列的同步法制备及其PL性能研究

在较低温度下，采用化学法在Zn片和玻璃片上同步制备了ZnO纳米棒阵列。利用XRD、FESEM和HRTEM对样品进行了表征，并且通过光致发光谱研究了阵列的光致发光(PL)性能。结果表明，ZnO纳米棒阵列较为致密、取向性较好。纳米棒为六方纤锌矿相，沿c轴生长，平均直径约为60 nm。同步法制备的2种ZnO纳米棒阵列均具有较好的紫外和橙红色发光性能，但发光特性却存在一定差异，这可能主要是由于2种阵列中纳米棒的缺陷含量不同所致。     

Triple assembly of ZnO, large-scale hollow spherical shells with flower-like species consisting of rods grown on the outer surfaces of shells

Novel large-scale hollow ZnO spherical shells were synthesized by ionic liquids assisted hydrothermal oxidization of pure zinc powder without any catalyst at a relatively low temperature of 160 °C. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) patterns show that the shells are composed of ZnO and the structure of the shells is very unique. Textured flower-like ZnO consisting of ZnO rods is grown on the outer surfaces of shells forming a triple assembly. Room-temperature photoluminescence spectra of the oxidized material show a sharp peak at 379 nm and a wider broad peak centered at 498 nm. The possible growth mechanism of the triple assembly of ZnO is discussed in detail.     

A Room-Temperature and Microwave Synthesis of M-Doped ZnO (M=Co,Cr, Fe,Mn &; Ni)

A room temperature and microwave method for the preparation M-Doped ZnO, where M=Co, Cr, Fe, Mn & Ni, is described. X-ray diffraction of the synthesized samples shows a single phase ZnO structure without any indication of the dopant. Magnetic studies of the as prepared samples show it to be paramagnetic. However, hydrogenation of particular samples at 573 K for 6 h resulted in transforming the samples to a room temperature ferromagnet.     

氨水溶液制备ZnO纳米晶阵列的研究

以氨水和硝酸锌为前躯体，采用低温水溶液法在涂敷ZnO晶种层的玻璃衬底上外延生长了ZnO纳米棒晶阵列。应用SEM、TEM、SAED和XRD表征了ZnO纳米晶的形貌和结构。讨论了该组成体系水溶液法纳米棒外延生长的机理及其对棒晶形貌的影响。通过对水溶液pH值的原位二次调整，制备出了ZnO纳米管和表面绒毛状的棒晶阵列，基于生长机理探讨了它们的形成原因，为实现不同形貌ZnO纳米晶阵列的优化控制提供了可能的技术途径。结果表明，不同形貌的ZnO均属沿c轴择优取向的六方纤锌矿结构。     

Reactive adsorption of thiophene on Ni/ZnO adsorbent：Effect of ZnO textural structure on the desulfurization activity

To better understand the nature of reactive adsorption of thiophene on Ni/ZnO adsorbent, the effect of ZnO textural structure on the desulfurization activity was investigated. ZnO materials were synthesized by low-temperature solid-state reaction and the corresponding Ni/ZnO adsorbents were prepared by incipient impregnation method. The analysis results showed that the crystalline sizes of ZnO as-synthesized as well as the BET surface areas varied obviously with the calcination temperature. The activity evaluations indicated that the Ni/ZnO adsorbents prepared with ZnO possessed a favorable textural structure as active component exhibited good activity of removing thiophene. The evolutions of the main crystalline phases of Ni/ZnO adsorbents before and after reaction confirmed that ZnO played a crucial role in taking up S element and converting it into ZnS in the reactive adsorption process. It was concluded that ZnO with larger surface area and smaller crystal particles resulted in better desulfurization activity, which may be the main reason for the different activities of the Ni/ZnO adsorbents prepared with ZnO calcined at different temperatures.