Preparation and Photoluminescence of ZnO Comb-Like Structure and Nanorod Arrays

A large quantity of Zinc oxide (ZnO) comb-like structure and high-density well-aligned ZnO nanorod arrays were prepared on silicon substrate via thermal evaporation process without any catalyst. The morphology, growth mechanism, and optical properties of the both structures were investigated using XRD, SEM, TEM and PL. The resulting comb-teeth, with a diameter about 20 nm, growing along the 0001 direction have a well-defined epitaxial relationship with the comb ribbon. The ZnO nanorod arrays have a diameter about 200 nm and length up to several micrometers growing approximately vertical to the Si substrate. A ZnO film was obtained before the nanorods growth. A growth model is proposed for interpreting the growth mechanism of comb-like zigzag-notch nanostructure. Room temperature photoluminescence measurements under excitation wavelength of 325 nm showed that the ZnO comb-like nanostructure has a weak UV emission at around 384 nm and a strong green emission around 491 nm, which correspond to a near band-edge transition and the singly ionized oxygen vacancy, respectively. In contrast, a strong and sharp UV peak and a weak green peak was obtained from the ZnO nanorod arrays.     

Controlled growth of well-aligned ZnO nanorod array using a novel solution method

A simple method of synthesizing nanomaterials and the ability to control the size and position of them are crucial for fabricating nanodevices. In this work, we developed a novel ammonia aqueous solution method for growing well-aligned ZnO nanorod arrays on a silicon substrate. For ZnO nanorod growth, a thin zinc metal seed layer was deposited on a silicon substrate by thermal evaporation. Uniform ZnO nanorods were grown on the zinc-coated silicon substrate in aqueous solution containing zinc nitrate and ammonia water. The growth temperature was as low as 60-90 degrees C and a 4-in. wafer size scale up was possible. The morphology of a zinc metal seed layer, pH, growth temperature, and concentration of zinc salt in aqueous solution were important parameters to determine growth characteristics such as average diameters and lengths of ZnO nanorods. We could demonstrate the discrete controlled growth of ZnO nanorods using sequential, tailored growth steps. By combining our novel solution method and general photolithography, we selectively grew ZnO nanorod arrays on a patterned silicon substrate. Our concepts on controlled ZnO nanorod growth using a simple solution method would be applicable for various nanodevice fabrications.     

Growth and Characterization of [001] ZnO Nanorod Array on ITO Substrate with Electric Field Assisted Nucleation

This paper reports direct growth of [001] ZnO nanorod arrays on ITO substrate from aqueous solution with electric field assisted nucleation, followed with thermal annealing. X-ray diffraction analyses revealed that nanorods have wurtzite crystal structure. The diameter of ZnO nanorods was 60–300 nm and the length was up to 2.5 μm depending on the growth condition. Photoluminescence spectra showed a broad emission band spreading from 500 to 870 nm, which suggests that ZnO nanorods have a high density of oxygen interstitials. Low and nonlinear electrical conductivity of ZnO nanorod array was observed, which was ascribed to non-ohmic contact between top electrode and ZnO nanorods and the low concentration of oxygen vacancies.     

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。     

水热法制备高度取向的氧化锌纳米棒阵列

氧化锌的激子结合能(60meV)及光增益系数(300cm^-1)比GaN的(25meV,100cm^-1)还高,这一特点使它成为紫外半导体激光发射材料的研究热点。最近,Yang等成功地观测到规则的ZnO纳米线阵列的激光发射现象,更加激起了人们合成一维高度有序ZnO纳米结构的热情,由于一维ZnO     

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。     

Patterned growth of ZnO nanorod arrays on a large-area stainless steel grid

Large-area ZnO nanorod arrays have been synthesized successfully on a stainless steel grid at a mild growth temperature of around 400 degrees C. The as-grown ZnO nanorods have uniform diameters of about 30-50 nm with approximately 5 nm tips. Patterned growth can be realized by engineering the shape of the grid in the growth. Photoluminescence demonstrates a sharp strong UV peak and a broad green band. The growth method provides a promising way of producing nanorod arrays with good controllability in patterns and morphologies, which will be critical in potential application such as high-efficiency filtering and catalysts.     

Influence of different substrates on ZnO nanorod arrays properties

Zinc Oxide (ZnO) nanorod arrays were grown on different substrates by hydrothermal method. The crystallinity of ZnO nanorod was regularly investigated by X-ray diffraction (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine morphology of the ZnO nanorods. The results indicate that the nanorods grow along [002] orientation. SEM and TEM images and XRD patterns show that the growth of ZnO nanorods on graphene/Quartz substrate is better than the other substrates due to the number and size of the nanorods which are highly affected through the properties of ZnO seed layers and it has lower defects than the other substrates. PL spectra ZnO would have a higher concentration of oxygen vacancy.     

籽晶层制备方式对氧化锌纳米棒阵列的影响

采用3种不同的方式制备ZnO薄膜籽晶层:旋涂、喷雾热解和脉冲激光沉积。对于每一种制备方式,其薄膜的晶体结构、形貌、表面粗糙度等性能分别用X射线衍射(XRD)、扫描电子显微镜(SEM)和原子力显微镜(AFM)进行了表征。之后,通过水热合成方法,在3种籽晶层衬底上制备得到具有不同结构和形貌特征的ZnO纳米棒阵列。结果表明,ZnO纳米棒生长和籽晶层制备方式具有极强的相关性。最后,对两者相关性的生长机理进行了解释。     

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.     

化学溶液沉积法制备单分散氧化锌纳米棒阵列

在由溶胶凝胶法制备的纳米ZnO薄膜基底上, 采用化学溶液沉积法制备了单分散、高度取向的ZnO纳米棒阵列膜. 通过控制纳米ZnO薄膜的制备工艺, 可以调节氧化锌纳米棒的直径. 利用FESEM, TEM, HRTEM, SAED和XRD表征了氧化锌纳米棒阵列的形貌和晶体结构. ZnO纳米棒的室温PL谱具有很高的紫外带边发射峰, 在可见光波段无发射峰, 表明该方法制备的ZnO纳米棒晶体结构完整, 晶体中O空位的浓度很低.     

原位生长的α-Fe2O3/ZnO异质纳米棒阵列对乙醇气体的高选择性检测

采用两步溶液法在陶瓷管上原位生长了ZnO纳米棒阵列,然后以ZnO纳米棒为载体,通过水热法在其表面负载α-Fe₂O₃纳米粒子,生成异质α-Fe₂O₃/ZnO复合纳米材料。 α-Fe₂O₃/ZnO纳米棒直径30~80 nm,长1 μm左右,交叉排列形成纳米棒阵列,α-Fe₂O₃纳米粒子粒径约10 nm,均匀分布在ZnO纳米棒表面。 将纯ZnO和α-Fe₂O₃/ZnO纳米棒阵列制成气敏元件,测试并对比了2种气敏元件的气敏性能,揭示其气敏机理。 结果表明:α-Fe₂O₃纳米粒子的复合显著提高了ZnO纳米棒阵列对乙醇气体的灵敏度和选择性,在工作温度370 ℃时,对100 μL/L乙醇气体的响应值为85.4,是同条件下ZnO器件对乙醇响应值(9.4)的9.1倍,响应时间7 s,最低检出限为0.01 μL/L。 相关研究可以应用于痕量乙醇的快速、高灵敏度和高选择性检测。     

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。     

Biofunctional ZnO nanorod arrays grown on flexible substrates

A square pattern of thioctic acid self-assembled ZnO nanorod arrays was grown on a large 4-in. thermoplastic polyurethane (TPU) flexible substrate via an in situ soluthermal process at low temperature (348 K). With the addition of dimercaptosuccinic acid (DMSA), the surface chemistry forms a disordered ZnO phase, and the morphology of the ZnO-DMSA nanorods changes with various DMSA addition times. As evidenced by the Zn2p3/2, C1s, O1s, S2p, and N-1s scans of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), DMSA and proteins were conjugated on the single crystalline ZnO nanorods. The photoluminescence (PL) spectra indicated that the optical properties of ZnO nanorod arrays were changed while the DMSA was inserted, and proteins were conjugated. Furthermore, a control test found that the ZnO nanorods show a significant improvement in sensitive characterization over the ZnO film. As another proteins (e.g., human serum albumin, HSA) were bound onto the ZnO-bovine serum albumin (BSA) nanorod arrays, an enhanced ultraviolet emission intensity was detected. On the basis of these results, one might be expected to conjugate specific biomolecules on the biofunctional ZnO nanorod arrays to detect the complementary biomolecules by PL detecting.     

Controllable synthesis of ZnO nanorod and prism arrays in a large area

ZnO nanorod and nanoprism arrays have been directly synthesized on a large-area zinc substrate via a convenient solution method. The products were characterized with XRD, SEM, HRTEM, and photoluminescence (PL) spectroscopy. The influence of the solvent and the concentration of NaOH on the size and shapes of the as-prepared ZnO samples have been studied. It was found that ZnO nanorod or nanowire arrays were fabricated in alcohol, whereas ZnO nanoprisms with pyramid tips were produced in an alcohol-water mixture. The diameters of the nanorods or nanoprisms became thicker when a higher concentration of NaOH was used. Room-temperature PL spectra of the ZnO products showed a UV emission and a broad green band. The mechanism of the nanorods and nanoprisms in two systems is briefly discussed.     

Effect of seed layer on the growth and the consequent gas sensing characteristics of ZnO nanorod arrays using aqueous chemical growth

The ZnO nanorod arrays are grown on the sol–gel-derived seed layer through aqueous chemical growth, and then assembled as gas sensors for detecting carbon monoxide (CO). It is found that the structural and photoluminescent properties of the ZnO nanorod arrays are different as they are grown on seed layers annealed at different temperature (300–700 °C), which is ascribed to distinct growth kinetics of nanorods on the annealed seed layer. Moreover, the correlation between the exposed surface area and the defect density of those ZnO nanorod arrays points out the intrinsic (interior) defects can dominate the green emission instead of surface defects in the present study. Furthermore, the quantities of chemisorbed oxygen on ZnO nanorod arrays can be estimated through XPS analysis. Consequently, the influence of intrinsic defects and chemisorbed oxygen on the electrical properties and gas sensitivities of ZnO nanorod arrays has been clearly elucidated. It is demonstrated that the more adsorbed oxygen and an appropriate amount of intrinsic defects is advantageous to obtain superior CO gas sensitivity for ZnO nanorod arrays.     

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.     

Surfactant-assisted route to synthesize well-aligned ZnO nanorod arrays on sol-gel-derived ZnO thin films

Anisotropic growth of ZnO nanorod arrays on ZnO thin films was achieved at a temperature of 90 degrees C by a surfactant-assisted soft chemical approach with control over size and orientation. ZnO thin films with c-axis preferred orientation had been achieved by the sol-gel technique. Lengths, diameters, and the degree of alignment of the ZnO nanorods were controlled by changing the experimental parameters. It was observed that the surfactant was essential to restrict the lateral growth of the nanorods, whereas the pH level of the reaction medium controlled the length of the nanorods. On the other hand, the orientation of the nanorods depended on the crystalline orientation of the film as well as the pH of the reaction medium. Room-temperature photoluminescence studies revealed that the ZnO nanorods with the best alignment exhibited the best emission property. The ZnO nanorods exhibited a strong UV emission peak at approximately 3.22 eV, ascribed to the band-edge emission. The field emission studies of the well-aligned nanorod arrays exhibited a low turn-on field of 1.7 V/microm to get an emission current density of 0.1 microA/cm(2).     

Fabrication and photoluminescent properties of heteroepitaxial ZnO/Zn0.8Mg0.2O coaxial nanorod heterostructures

ZnO/Zn0.8Mg0.2O coaxial nanorod heterostructures were prepared by employing catalyst-free metal-organic vapor-phase epitaxy, and their structural and photoluminescent (PL) properties were investigated using transmission electron microscopy (TEM) and temperature-dependent PL spectroscopy. TEM images show that ZnO/Zn0.8Mg0.2O layers were epitaxially grown on the entire surfaces of the ZnO nanorods and the ZnO nanorod diameters as a core material were as small as 9 +/- 2 nm. A dominant PL peak was observed at 3.316 eV, from room-temperature PL spectra of ZnO/Zn0.8Mg0.2O coaxial nanorod heterostructures with ZnO core diameters of 9 nm, indicating a PL blue shift of 30 meV, which resulted from a quantum confinement effect along the radial direction in ZnO nanorods. Furthermore, temperature-dependent PL properties of the coaxial nanorod heterostructures were investigated, showing much higher PL intensity for the coaxial nanorod heterostructures than that of bare ZnO nanorods at room temperature. The origin of the enhanced PL intensity and reduced thermal quenching for the coaxial nanorod heterostructures is also discussed.     

Pt纳米花/ZnO复合阵列的制备及对甲醇氧化催化的研究

利用调控ZnO纳米棒阵列的疏水、亲水性,由电化学方法制备了Pt纳米花/ZnO(PtNF/ZnO)复合阵列.该复合阵列排列规则、尺寸均一、方向一致.每一根ZnO纳米棒的顶端都覆盖着由Pt纳米颗粒构成的Pt纳米花,具有大的比表面积.与以亲水性的ZnO纳米棒制得的覆盖Pt纳米颗粒的ZnO复合阵列(PtNP/ZnO)以及单独的Pt颗粒相比,PtNF/ZnO复合阵列对甲醇氧化具有更高的电化学催化活性.