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.     

Ga-F共掺杂ZnO导电性和透射率的第一性原理计算

采用基于密度泛函理论的第一性原理平面波超软赝势方法,对本征ZnO,Ga、F单掺ZnO和Ga-F共掺ZnO的几何结构进行优化后计算了各体系的相关性质。结果表明各掺杂体系有各自的优缺点,在制作透明导电薄膜时可根据具体要求采取不同的掺杂方案。Ga掺杂ZnO比F掺杂ZnO的晶格畸变小。相同环境下Ga原子比F原子更容易进入ZnO晶格,因此掺杂后结构更加稳定。Ga、F掺杂都改善了ZnO的导电性,掺杂ZnO的载流子浓度比本征ZnO增加了3个数量级,相同浓度的F掺杂比Ga掺杂能产生更多的载流子。Ga-F共掺杂ZnO折中了上述Ga、F单掺杂ZnO的优缺点。另外,掺杂后ZnO的吸收边蓝移,以GaF共掺杂ZnO在紫外区域的透射率最大,在280~380 nm范围内其透射率在90%以上。     

Effect of Zinc Oxide on Morphology and Mechanical Properties of Polyoxymethylene/Zinc Oxide Composites

This paper studies the effects of zinc oxide (ZnO) on morphology and mechanical properties of pure polyoxymethylene (POM) and POM/ZnO composites. POM/ZnO composites with varying concentration of ZnO were prepared by melt mixing technique in a twin screw extruder. The dispersion of ZnO particles on POM composites was studied by scanning electron microscope (SEM). It is observed that the dispersion of ZnO particles is relatively good. The mechanical properties of the composites such as tensile strength, stress at break, Young's modulus and impact strength were measured. Increasing content of ZnO up to 4.0 wt% increases the impact strength of POM. Addition of ZnO beyond 4.0 wt% decreases the impact strength. The composites containing ZnO content greater than 2.0 wt% show increased Young's Modulus. The tensile strength and stress at break decrease with increasing ZnO content. This may be due to the compatibility between ZnO and POM.     

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.     

Ga-F共掺杂ZnO导电性和透射率的第一性原理计算

用基于密度泛函理论的第一性原理平面波超软赝势方法,对本征ZnO,Ga、F单掺ZnO和Ga-F共掺ZnO的几何结构进行优化后计算了各体系的相关性质.结果表明各掺杂体系有各自的优缺点,在制作透明导电薄膜时可根据具体要求采取不同的掺杂方案.Ga掺杂ZnO比F掺杂ZnO的晶格畸变小.相同环境下Ga原子比F原子更容易进入ZnO晶格,因此掺杂后结构更加稳定.Ga、F掺杂都改善了ZnO的导电性,掺杂ZnO的载流子浓度比本征ZnO增加了3个数量级,相同浓度的F掺杂比Ga掺杂能产生更多的载流子.Ga-F共掺杂ZnO折中了上述Ga、F单掺杂ZnO的优缺点.另外,掺杂后ZnO的吸收边蓝移,以Ga-F共掺杂ZnO在紫外区域的透射率最大,在280~380 nm范围内其透射率在90%以上.     

Fabrication and evaluation of ZnO nanorods by liquid-phase deposition

The ZnO nanorod growth mechanism during liquid-phase deposition (LPD) has been investigated, with results considered in the context of phase stabilization, LPD chemical processes, and Gibbs free energy and entropy. Zinc oxide (ZnO) possesses unique optical and electronic properties, and obtaining ZnO species with high specific surface area is important in ZnO applications. Highly c-axis-oriented ZnO films are expected to be utilized in future optical and electrical devices. ZnO nanorods were synthesized using an aqueous solution deposition technique on a glass substrate with a free-standing ZnO nanoparticle layer. ZnO nanorod growth was easily controlled on the nanoscale by adjustment of the immersion time (15-210 min). X-ray diffraction, field-emission scanning electron microscopy (FE-SEM), and film thickness measurements were used to characterize the crystalline phase, orientation, morphology, microstructure, and growth mechanism of the ZnO nanorods. FE-SEM images were analyzed by image processing software, which revealed details of the of ZnO nanorod growth mechanism.     

Enhanced Thermocatalytic Activity of Porous Yellow ZnO Nanoflakes: Defect‐ and Morphology‐Induced Perspectives

Herein, we report a simple and effective strategy for the synthesis of yellow ZnO (Y‐ZnO) nanostructures with abundant oxygen vacancies on a large scale, through the sulfidation of ZnO followed by calcination. The developed strategy allows retention of the overall morphology of Y‐ZnO compared with pristine ZnO and the extent of oxygen vacancies can be tuned. The influence of oxygen deficiencies, the extent of defect sites, and the morphology of ZnO on its solution‐phase thermocatalytic activity has been evaluated in the synthesis of 5‐substituted‐1H‐tetrazoles with different nitriles and sodium azide. A reasonable enhancement in the reaction rate was achieved by using Y‐ZnO nanoflakes (Y‐ZnO NFs) as a catalyst in place of pristine ZnO NFs. The reaction was complete within 6 h at 110 °C with Y‐ZnO NFs, whereas it took 14 h at 120 °C with pristine ZnO NFs. The catalyst is easy to recycle without a significant loss in catalytic activity.     

ZIF-8衍生ZnO耦合HZSM-5一步催化合成气制烃醚燃料

通过水热溶剂法合成有机骨架结构材料ZIF-8,以其为前驱体调变焙烧温度制备ZnO纳米粒子。采用XRD、TEM、XPS、Raman等表征研究ZnO的组成结构及晶粒粒径形态变化;将ZnO与HZSM-5耦合形成双功能催化剂,考察其在合成气转化中的催化活性。结果表明,焙烧温度对ZnO的颗粒粒径结构影响较大,温度影响晶粒的形成速率,提高温度会促进ZnO的聚集; ZIF-8衍生ZnO通过调变温度影响ZnO晶粒粒径,起到改变产物分布的作用。当焙烧温度≤450℃时,以碳包覆ZnO纳米粒子结构存在,ZnO晶粒粒径小于20 nm,含碳ZnO耦合HZSM-5催化剂的产物以二甲醚为主;当温度≥500℃,以纯相ZnO存在,ZnO晶粒粒径皆大于20 nm,ZnO耦合HZSM-5催化剂的产物以烃类为主。ZnO与HZSM-5的耦合方式对双功能催化剂的产物选择性有显著影响。     

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.     

电沉积制备ZnO纳米棒修饰电极上氧化还原蛋白的电化学行为

采用恒电位阴极还原法在金电极表面一步修饰ZnO纳米棒, 制备成ZnO纳米棒修饰电极. 扫描电子显微镜(SEM)和X射线衍射(XRD)结果显示制得的ZnO为直径约100 nm的六棱柱状纤锌矿晶体纳米棒. 使用ZnO纳米棒修饰的金电极研究细胞色素c的直接电化学行为, 结果表明: ZnO纳米棒修饰的金电极能有效探测到细胞色素c的铁卟啉辅基在不同价态下的电化学行为; 细胞色素c吸附后, ZnO纳米棒修饰的金电极对过氧化氢的电流响应呈现良好的线性关系.     

Simplifying patterning process of ZnO nanowires by one step development and etching process

We present herein a simple protocol of growing a patterned ZnO nanowire by etching of ZnO seed layer in the tetramethyl ammonium hydroxide (TMAH) solution. The ZnO seed layer was fabricated by sol–gel method using zinc acetate solution and patterned by using photolithographic method. Patterned ZnO seed layer as etched in the TMAH solution, followed by growth of ZnO nanowires by hydrothermal method. Remarkable point of present ZnO seed layer patterning is that development of UV-exposed photoresist and etching of ZnO seed layer is subsequently processed in aqueous TMAH solution without interruption. The grown ZnO nanowires were analyzed using XRD patterns to exhibit high purity and degree of crystallinity, and showed very good pattern fidelity.     

Synthesis and field emission characteristics of bilayered ZnO nanorod array prepared by chemical reaction

The uniform, large-scale, and bilayered ZnO nanorod array on silicon substrate has been synthesized by a catalyst and template-free chemical reaction in a dilute solution. The effect of different precursor ZnO films on the morphology and size of the ZnO nanorod array has been investigated. Moreover, the morphology evolution of the ZnO nanorod array with the increase of reaction time indicates that the second growth is the reason for the decrease of the ZnO nanorod diameter and the formation of the bilayered ZnO nanorod array. Finally, the field emission from the ZnO nanorod array with different diameters is presented.     

Electrical,optical and photocatalytic properties of Ti-loaded ZnO/ZnO and Ti-loaded ZnO nanospheres

Ti-loaded ZnO and Ti-loaded ZnO/ZnO nanoparticles have been synthesized by sol–gel method and analyzed for photocatalyst application. The phase confirmation was analyzed by powder XRD and surface morphology with HR-SEM and EDAX spectrum. The particle size measured using HR-TEM and SAED pattern confirms the crystalline nature of Ti-loaded ZnO and Ti-loaded ZnO/ZnO nanoparticles. The optical properties were studied with UV–visible diffuse reflectance spectra. The DRS of Ti-loaded ZnO/ZnO nanoparticles are similar to those of pristine ZnO nanoparticles. The KM plots show both the synthesized Ti-loaded ZnO/ZnO and Ti-loaded ZnO exhibit in UV-A region. The electric properties are studied with impedance analyzer, and the results show the charge-transfer resistance of Ti-loaded ZnO/ZnO is larger than that of Ti-loaded ZnO nanoparticles. The photocatalytic activity was studied with methylene blue dye and phenol degradation by Ti-loaded ZnO/ZnO, Ti-loaded ZnO, TiO₂ and ZnO nanoparticles. The photocatalytic activity of Ti-loaded ZnO/ZnO nanospheres is slightly higher than that of other nanoparticles, which shows that they have excellent application as photocatalyst.     

Fabrication of hierarchical ZnO architectures and their superhydrophobic surfaces with strong adhesive force

Grid-structured ZnO microsphere arrays assembled by uniform ZnO nanorods were fabricated by noncatalytic chemical vapor deposition, taking advantage of morphologies of alumina nanowire pyramid substrates and ZnO oriented growth habits. Every ZnO microsphere (similar to the micropapilla on a lotus leaf surface) is assembled by over 200 various oriented ZnO nanorods (similar to the hairlike nanostructures on mircopapilla of a lotus leaf). This lotus-leaf-like ZnO micro-nanostructure films reveal superhydrophobicity and ultrastrong adhesive force to liquid. The realization of this hierarchical ZnO nanostructure film could be important for further understanding wettability of biological surfaces with micro-nanostructure and application in microfluidic devices.     

常温直接沉淀法制备ZnO纳米棒

在常温下, 以PEG-400(聚乙二醇400)为表面活性剂, 采用直接沉淀法合成了ZnO纳米棒. 产物用XRD, TEM, SAED和 HRTEM等进行了表征. 结果表明, 所得ZnO为一维的纳米棒, 属于六方纤维矿的单晶结构. ZnO纳米棒的直径在20~40 nm之间, 长度在300~800 nm范围. (0001)面为ZnO纳米棒的生长方向. 讨论了ZnO相的生成和ZnO纳米棒的形成机理以及PEG-400在其形成过程中的作用.     

Experimental and Theoretical Study of Enhanced Photocatalytic Activity of Mg‐Doped ZnO NPs and ZnO/rGO Nanocomposites

A systematic experimental and theoretical study of the origin of the enhanced photocatalytic performance of Mg‐doped ZnO nanoparticles (NPs) and Mg‐doped ZnO/reduced graphene oxide (rGO) nanocomposites has been performed. In addition to Mg, Cd was chosen as a doping material for the bandgap engineering of ZnO NPs, and its effects were compared with that of Mg in the photocatalytic performance of ZnO nanostructures. The experimental results revealed that Mg, as a doping material, recognizably ameliorates the photocatalytic performance of ZnO NPs and ZnO/graphene nanocomposites. Transmission electron microscopy (TEM) images showed that the Mg‐doped and Cd‐doped ZnO NPs had the same size. The optical properties of the samples indicated that Cd narrowed the bandgap, whereas Mg widened the bandgap of the ZnO NPs and the oxygen vacancy concentration was similar for both samples. Based on the experimental results, the narrowing of the bandgap, the particle size, and the oxygen vacancy did not enhance the photocatalytic performance. However, Brunauer–Emmett–Teller (BET) and Barret–Joyner–Halenda (BJH) models showed that Mg caused increased textural properties of the samples, whereas rGO played an opposite role. A theoretical study, conducted by using DFT methods, showed that the improvement in the photocatalytic performance of Mg‐doped ZnO NPs was due to a higher electron transfer from the Mg‐doped ZnO NPs to the dye molecules compared with pristine ZnO and Cd‐doped ZnO NPs. Moreover, according to the experimental results, along with Mg, graphene also played an important role in the photocatalytic performance of ZnO.     

类石墨碳修饰提高ZnO纳米棒阵列光催化活性和光稳定性的研究

半导体光催化是一种理想的太阳能化学转化绿色技术,可以实现水分解制氢和CO2光还原制备碳氢化合物燃料.氧化锌 (ZnO) 作为一种直接带隙半导体材料,一方面具有性能优异、价格低廉、易制备等优点; 另一方面因光腐蚀而不稳定,大大限制了该材料的实际应用.本文提出了一种简单易行的类石墨碳修饰方法,可以有效提高 ZnO 用于CO2光还原的光催化活性和稳定性.首先采用水热法在金属锌片基底上生长 ZnO 纳米棒阵列 (ZnO-NRA),然后通过葡萄糖水热法进行不同含量的类石墨碳 (C-x) 修饰,形成 ZnO-NRA/C-x 纳米复合结构,同步实现碳包覆和碳掺杂.X 射线衍射结果表明,ZnO 纳米棒及ZnO-NRA/C-x 纳米复合结构都具有良好的纤锌矿型 (Wurtzite) 结构; 而拉曼散射则清楚地证实了类石墨碳的存在.扫描电子显微观察显示,生长的 ZnO 纳米棒长度大约 2-5 μm,直径为 400-700 nm,沿方向[0001]生长,端部由六个规则的 (103)晶面组成,进一步直观佐证了 ZnO 的典型纤锌矿型结构特征.透射电子显微分析结果表明,ZnO-NRA/C-x 纳米复合结构中类石墨碳包覆层厚度大约为 8 nm.ZnO-NRA/C-x 纳米复合结构的 X 射线光电子谱分析结果验证了 C-C,C-O 和 C=O键的存在与碳的包覆层相对应; 而 C-O-Zn键的出现则是由于碳在 ZnO 中掺杂所引起.从紫外-可见吸收谱上可观察到ZnO 的典型吸收带边位置约为 385 nm,而碳的包覆和掺杂导致 ZnO-NRA/C-x 纳米复合结构的吸收带边发生红移,并且吸收背底明显提高.电化学阻抗谱测试结果清楚地显示,ZnO-NRA/C-x 纳米复合结构比单纯 ZnO-NRA 的电化学阻抗明显降低,说明类石墨碳包覆层大幅度提高了电导性能,从而有利于光生载流子的分离和传输.荧光分析结果也表明,与单纯的 ZnO-NRA 相比,ZnO-NRA/C-x 纳米复合结构的荧光强度大幅度下降,进一步证实了 ZnO-NRA/C-x 纳米复合结构比单纯的 ZnO-NRA更有利于光生载流子的分离和传输.光电化学测试结果表明,ZnO-NRA/C-x 纳米复合结构的瞬态光电流 4 倍于单纯的ZnO-NRA,而 CO2 光还原性能测试也得到一致的结果.长时间多循环 CO2 光还原实验证实,ZnO-NRA/C-x 纳米复合结构具有稳定的光催化活性和极好的光稳定性.综上,我们利用一种简单易行的水热法进行类石墨碳修饰,成功开发了 ZnO-NRA/C-x 纳米复合结构,该结构因其优异的光生电子和空穴的分离和迁移性能,从而具有显著提升的CO2光还原活性和光稳定性.本工作证明,类石墨碳修饰是一种可以广泛借鉴的有效提升半导体材料光催化活性和光稳定性的可行方法.     

Growth of ramification-like ZnO rods in the presence of polyaniline

To obtain new materials with synergetic or complementary behaviors, polyaniline composite filled with ZnO rods in ramification-like structure was prepared by a hydrothermal approach. Comparative experiments of ZnO preparation in the presence of some metal ions were also carried out. The results indicated that the morphology of ZnO was strongly affected by the preparation condition. The method to grow ZnO rods in the presence of polyaniline offers a simple approach to obtain polyaniline composite filled with linear ZnO structure. The results of X-ray photoelectron spectroscopy show that the strong interaction between ZnO and polyaniline possibly exists to cause the charge transfer.     

Preparation, characterization, and photocatalytic activity of polyaniline/ZnO nanocomposite

Polyaniline (PANI)/zinc oxide (ZnO) nanocomposite was synthesized by in-situ polymerization. X-ray diffraction patterns, UV?Cvisible spectroscopy, SEM, and TEM were used to characterize the composition and structure of the nanocomposite. Nanostructured PANI/ZnO composite was used as photocatalyst in the photodegradation of methylene blue dye molecules in aqueous solution. The photocatalytic activity of PANI/ZnO nanocomposite under UV and visible light irradiation was evaluated and was compared with that of ZnO nanoparticles. ZnO/PANI core?Cshell nanocomposite had greater photocatalytic activity than ZnO nanoparticles and pristine PANI under visible light irradiation. According to these results, application of PANI as a shell on the surface of ZnO nanoparticles causes the enhanced photocatalytic activity of the PANI/ZnO nanocomposite. Also UV?Cvisible spectroscopy studies showed that the absorption peak for PANI/ZnO nanocomposite has a red shift toward visible wavelengths compared with the ZnO nanoparticles and pristine PANI. The effect of different operating conditions on the photocatalytic performance of PANI/ZnO nanocomposite in the photodegradation of methylene blue dye molecules was investigated in a bath experimental setup.     

p-Type behaviour of electrodeposited ZnO:Cu films

Cu-doped ZnO (ZnO:Cu) thin films and ZnO/ZnO:Cu homojunction devices were electrodeposited on conductive glass substrates in a non-aqueous electrolyte containing Cu and Zn salts. The Cu content of the films is proportional to the Cu/Zn precursor ratio in the deposition electrolyte. ZnO:Cu was found to be of a hexagonal wurtzite structure with (002) preferred orientation. A transition from n-type to p-type was observed for ZnO:Cu films with a Cu/Zn ratio higher than 2% as inferred from the change in the direction of the photocurrent. The rectifying characteristics shown by homojunction devices further confirm the p-type conductivity of ZnO:Cu layers.