Electrical investigation and ultraviolet detection of ZnO nanorods encapsulated with ZnO and Fe-doped ZnO layer

Encapsulated ZnO nanorod arrays were fabricated using a two-step method; hydrothermal followed by dip-coating. Intensity of X-ray diffraction peaks of ZnO nanorod films increased by encapsulation with ZnO and Fe doped ZnO layer. Encapsulation process increased diameter of the rods in a range of 20–40 nm. The optical studies indicated that the band-gap decreased with increment of the nanorod diameter, and increased with Fe doping in the ZnO layer. The electrical resistance of the samples demonstrated a remarkable reduction due to encapsulation, especially in the sample encapsulated with Fe doped-ZnO layer. The photoresponse behavior of ZnO nanorod films was investigated under different powers of ultraviolet illumination. The photoresponsivity was improved for encapsulated nanorods as compared to bare nanorods.     

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.     

金属有机化学气相沉积法制备ZnO和ZnO∶Ni薄膜及其特性分析

采用金属有机化学气相沉积法制备了ZnO和ZnO∶Ni薄膜,并对它们的结构、光学和电学特性进行了对比研究.通过扫描电子显微镜( SEM)和X射线衍射(XRD)对薄膜的表面形貌和晶体结构进行了分析,结果表明,Ni元素的掺杂虽然降低了薄膜的晶体质量,但并未改变ZnO的纤锌矿结构.通过紫外-可见分光光度计对薄膜的光学特性进行了...     

合成ZnO纳米阵列及刺突状CuO/ZnO异质结

采用低温水热法在掺氟SnO₂ (FTO)导电玻璃表面制备ZnO纳米阵列, 研究了前驱体溶液浓度摩尔配比对ZnO纳米阵列形貌、光学性能及其生长机理的影响. 研究发现, 随着前驱体溶液浓度摩尔配比的增加, ZnO纳米阵列形貌及光学性能也随之变化. ZnO纳米阵列高度逐渐降低, ZnO纳米阵列直径和光学带隙值大体上出现先增大后降低的趋势. 而当前驱体溶液(Zn(NO₃)₂:环六亚甲基四胺(HMT, C₆H₁₂N₄))浓度摩尔配比为5:5时, 其光学禁带值(3.2 eV)接近于理论值. 结果显示制备ZnO纳米阵列的最优浓度摩尔配比为5:5. 随后选用最优浓度摩尔配比下制备的ZnO纳米阵列为基底, 通过一种两步溶液法成功在其表面制备刺突状CuO/ZnO异质结.从场发射扫描电镜(FE-SEM)结果中可以清楚看见, 大量的CuO纳米粒子沉积在ZnO纳米阵列表面形成刺突状异质结结构.研究发现该CuO/ZnO纳米异质结相对于纯ZnO纳米阵列在紫外光下光催化性能明显增加. 最后, 讨论了CuO/ZnO纳米异质结光催化机理.     

纳米氧化锌及负载沸石的抗菌性能研究

霉变是引起饲料变质的主要因素.目前已知污染饲料的产毒霉菌约100多种,可产生200多种霉菌毒素,其中,黄曲霉菌产生的有毒代谢物黄曲霉毒素（AFT）已成为世界很多地区的主要问题.实践证明,最有效的办法之一是在饲料中添加防霉物质即防霉剂.丙酸盐对于霉菌、酵母菌及细菌具有广泛的抗菌作用,尤其是对黄曲霉等抑制作用比山梨酸钾和苯甲酸钠盐都要强得多,生产成本又较低.因此,早在五、六十年代就已被大多数发达国家作为最重要、最广泛的食品防腐剂使用.但是丙酸受热损失大,不适合制粒,挥发快,防霉持续期比较短,易受钙盐中和而造成活力损失.丙酸腐蚀性强,有刺激性气味,也影响饲料适口性,而且饲料需要在一定的酸性条件下才能发挥防霉的功效[1].由此可见,丙酸类防霉剂有着很多的缺陷,亟待更替.     

Tunable photoluminescent and cathodoluminescent properties of ZnO and ZnO:Zn phosphors

ZnO and ZnO:Zn powder phosphors were prepared by the polyol-method followed by annealing in air and reducing gas, respectively. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectra (XPS), electron paramagnetic resonance (EPR), and photoluminescence (PL) and cathodoluminescence (CL) spectra, respectively. The results indicate that all samples are in agreement with the hexagonal structure of the ZnO phase and the particle sizes are in the range of 1-2 microm. The PL and CL spectra of ZnO powders annealed at 950 degrees C in air consist of a weak ultraviolet emission band (approximately 390 nm) and a broad emission band centered at about 527 nm, exhibiting yellow emission color to the naked eyes. When the sample was reduced at the temperatures from 500 to 1050 degrees C, the yellow emission decreased gradually and disappeared completely at 800 degrees C, whereas the ultraviolet emission band became the strongest. Above this temperature, the green emission ( approximately 500 nm) appeared and increased with increasing of reducing temperatures. According to the EPR results and spectral analysis, the yellow and green emissions may arise from the transitions of photogenerated electron close to the conduction band to the deeply trapped hole in the single negatively charged interstitial oxygen ion (Oi(-)) and the single ionized oxygen vacancy (V.O) centers, respectively.     

Development and characterization of ZnO, Au/ZnO and Pd/ZnO thin films through their adsorptive and catalytic properties

In this paper, we report (a) the development of ZnO thin films prepared by pulsed laser deposition and partially covered with nano-particles Pd or Au and (b) their physicochemical study, in order to investigate their catalytic and/or adsorptive properties. It is the first time where two different and popular methods, namely pulsed laser deposition and reversed flow-inverse gas chromatography, are combined. The inverse gas chromatographic technique with the corresponding time-resolved analysis is used for the first time in order to characterise compounds in the nano-scale domain. We focus on the determination of physicochemical quantities mainly concerning the adsorption in thin films, with (Pd/ZnO) or without (Au/ZnO) catalytic behaviour. Thus, entropy and other important physicochemical quantities are calculated which reveal the mechanism of adsorption as well as of isomerization-hydrogenation of 1-butene and contribute to the study of heterogeneity of thin film surfaces. The programs used have been written in Fortran. An important achievement is also the determination of the standard deviations of the kinetic constants.     

Study on the Mixed ZnO Clusters and Ring-Like ZnO Ions

The pure Zn_m (m?=?2–10), mixed Zn_mO_m (m?=?1–10), Zn_mO_10??m (m?=?1–9) clusters and the univalent and divalent ring-like Zn_mO_m (m?=?2–10) cluster ions are systematically investigated by using Amsterdam density functional (ADF) program with Triple-zeta with two polarization functions basis set in conjunction with self-consistent field. Our calculated results show that the Zn₄ and Zn₇ clusters are the magic clusters. The structures of the Zn_mO_m (m?=?1–10) clusters evolve from two-dimension to three-dimension after m?=?8. For the Zn_mO_10??m (m?=?1–9) clusters, the Zn-rich structures evolve gradually from three-dimension to plane with an increase in the O ratios. The Zn₅O₅ cluster with equal ratio has a two dimensional structure. In the O-rich clusters, the O dimers can be easily detached from them. The O and Zn atoms partly adopt sp² and sp hybridization, respectively, in the ring-like Zn_mO_m (m?=?2–10) clusters and their ions. Gain and loss charge would affect the degree of hybridization and change their geometries. Their structural changes can be explained by valence bond theory.     

Morphology-controlled large-scale synthesis of ZnO nanocrystals from bulk ZnO

Gram-scale, teardrop-like, monodisperse ZnO nanocrystals with a well-resolved absorption onset and a strong sharp UV emission were prepared by thermal decomposition of ZnO-oleic acid complexes in hexadecylamine.     

Pd/ZnO和Ag/ZnO复合纳米粒子的SPS和XPS研究

用焙烧前驱物碱式碳酸锌的方法制备了ZnO纳米粒子，采用光还原沉积贵金属的方法分别得到了质量分数为0.5％的Pd/ZnO和Ag/ZnO复合纳米粒子，并利用XRD、TEM、XPS和SPS等测试技术对样品进行表征.初步探讨了贵金属在ZnO纳米粒子表面形成原子簇的原因及沉积贵金属对ZnO纳米粒子表面光电压信号的影响.以光催化氧化气相正庚烷为模型反应，考察了沉积贵金属对ZnO纳米粒子光催化活性的影响，并探讨了光催化活性有所提高的内在原因.结果表明， ZnO纳米粒子沉积贵金属后，其表面光电压信号明显下降，而光催化活性却大大地提高，这说明可以通过表面光电压谱的测试来初步的评估纳米粒子的光催化活性，即粒子的表面光电压信号越弱，其光催化活性越高.     

Optical properties of ZnO and ZnO:In nanorods assembled by sol-gel method

Self-assembled zinc oxide (ZnO) and indium-doping zinc oxide (ZnO:In) nanorod thin films were synthesized on quartz substrates without catalyst in aqueous solution by sol-gel method. The samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), Raman-scattering spectroscopy, room-temperature photoluminescence (PL) spectra, and temperature-dependent PL spectra measurements. XRD and Raman spectra illustrated that there were no single In2O3 phase in ZnO lattice after indium doping. The PL spectra of ZnO showed a strong UV emission band located at 394 nm and a very weak visible emission associated with deep-level defects. Indium incorporation induced the shift of optical band gap, quenching of the near-band-edge photoluminescence and enhanced LO mode multiphonon resonant Raman scattering in ZnO crystals at different temperatures. Abnormal temperature dependence of UV emission integrated intensity of ZnO and ZnO:In samples is observed. The local state emission peak of ZnO:In samples at 3.37 eV is observed in low-temperature PL spectra. The near-band-edge emission peak at room temperature was a mixture of excitons and impurity-related transitions for both of two samples.     

Micropencils and microhexagonal cones of ZnO

Shape selective synthesis of ZnO micropencils and microhexagonal cones has been demonstrated using a controlled method of modified vapor deposition. A plausible growth mechanism based on the results of scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetry, and differential thermal analysis is proposed. Our results suggest that growth of micropencil takes place as per the vapor-liquid-solid progression while the microhexagonal cones grow in two steps following a vapor-solid/vapor-liquid-solid mechanism. Moreover, the geometry, the location of substrate and temperature are found to have key roles in governing the morphology. XPS studies clearly demonstrate the presence of Si species as SiO and SiO2, which act as catalysts enabling nucleating sites for ZnO microstructural growth.     

氧化锌纳米棒的制备和生长机理研究

ZnO nanorods are prepared by different assistants (cetyltrimethylammonium bromide，trisodium citrate and ethylene diamine anhydrous) favored hydrothermal synthesis with Zn(OH)₂ colloid as the precursor. The samples are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that the as-synthesized ZnO nanorods are of uniform size with 25 nm in diameter and 200～300 nm in length. The effects of the different assistants to the morphology, size and mechanism of nano-ZnO are discussed.     

哑铃状氧化锌的合成与表征

采用超声波辅助回流法制备了高纯度且尺寸一致的哑铃状氧化锌。用扫描电镜、透射电镜和X射线粉末衍射分析了氧化锌的形貌和结构，用紫外-可见吸收光谱和荧光光谱测定其光学性质，并初步探讨了哑铃状氧化锌的形成机理。结果表明，超声波处理、溶液的碱度和乙二胺对哑铃状形貌的形成起了重要作用，研究发现该哑铃状氧化锌具有独特的光学性质。     

Secondary nucleation and growth of ZnO

Recently we discovered that under certain conditions new crystal growth (branch) can be induced on specific crystalline planes of the same material. This is a new phenomenon and is in sharp contrast to typical nucleation and growth in which a crystal will simply grow larger in preferred directions depending on the surface energy of the specific crystalline planes. Based on our observation, we developed a sequential nucleation and growth technique offering the power to assemble complex hierarchical crystals step-by-step. However, the key questions of when and how the secondary nucleation takes place have not been answered. Here we systematically study secondary ZnO crystal growth using organic diamine additives with a range of chain lengths and concentration. We found that ZnO branches form for a narrow diamine concentration range with a critical lower and upper critical nucleation concentration limit, which increases by about a factor of 5 for each additional carbon in the diaminoalkane chain. Our results suggest that the narrow window for secondary growth is dictated by the solubility of the ZnO crystals, where the low critical nucleation concentration is determined by slight etching of the surface to produce new nucleation sites, and the upper critical concentration is determined by the supersaturation concentration. Kinetic measurements show that the induction time and growth rate increase with increasing diamine concentration and follow classical nucleation and growth theory. Observations of branch morphological evolution reveal the mechanisms guiding the tunable crystal size and morphology.     

活性ZnO的制备及其表征

用传统沉淀法以超声波振荡方式制备出粒径约为32．Onm的六方晶型ZnO超细粉。其结构经IR和X-射线衍射表征,并测定了其粒径、比表面积和电学性质。     

Synthesis and Characterization of ZnO Nanowires

Zinc oxide is a wide bandgap (3.37 eV) semiconductor with a hexagonal wurtzite crystal structure. ZnO prepared in nanowire form may be used as a nanosized ultraviolet light-emitting source. In this study, ZnO nanowires were prepared by vapor-phase transport of Zn vapor onto gold-coated silicon substrates in a tube furnace heated to 900 ?C. Gold serves as a catalyst to capture Zn vapor during nanowire growth. Size control of ZnO nanowires has been achieved by varying the gold film thickness…     

Synthesis and characterization of ZnO and ZnO:Ga films and their application in dye-sensitized solar cells

Highly crystalline ZnO and Ga-modified zinc oxide (ZnO:Ga) nanoparticles containing 1, 3 and 5 atom% of Ga3+ were prepared by precipitation method at low temperature. The films were characterized by XRD, BET, XPS and SEM. No evidence of zinc gallate formation (ZnGa2O4), even in the samples containing 5 atom% of gallium, was detected by XRD. XPS data revealed that Ga is present into the ZnO matrix as Ga3+, according to the characteristic binding energies. The particle size decreased as the gallium level was increased as observed by SEM, which might be related to a faster hydrolysis reaction rate. The smaller particle size provided films with higher porosity and surface area, enabling a higher dye loading. When these films were applied to dye-sensitized solar cells (DSSCs) as photoelectrodes, the device based on ZnO:Ga 5 atom% presented an overall conversion efficiency of 6% (at 10 mW cm(-2)), a three-fold increase compared to the ZnO-based DSSCs under the same conditions. To our knowledge, this is one of the highest efficiencies reported so far for ZnO-based DSSCs. Transient absorption (TAS) study of the photoinduced dynamics of dye-sensitized ZnO:Ga films showed that the higher the gallium content, the higher the amount of dye cation formed, while no significant change on the recombination dynamics was observed. The study indicates that Ga-modification of nanocrystalline ZnO leads to an improvement of photocurrent and overall efficiency in the corresponding device.     

Pd/ZnO和Ag/ZnO复合纳米粒子的制备、表征及光催化活性

 用焙烧前驱物碱式碳酸锌的方法制备了ZnO纳米粒子，采用光还原沉积贵金属的方法制备了Pd／ZnO和Ag／ZnO复合纳米粒子，并利用ICP，XRD，TEM和XPS等测试技术对样品进行了表征，初步探讨了贵金属在ZnO纳米粒子表面形成原子簇的原因．以光催化氧化气相正庚烷为模型反应，考察了样品的光催化活性以及贵金属沉积量对催化剂活性的影响．结果表明：沉积适量的贵金属，ZnO纳米粒子光催化剂的活性大幅度提高．同时，深入探讨了表面沉积贵金属的ZnO纳米粒子光催化剂活性有所提高的内在原因．     

Zn基片上ZnO及ZnS/ZnO复合纳米阵列的液相合成及发光性质

采用温和的溶液路线在Zn基片上合成了单晶态的ZnO纳米棒阵列、 纳米片阵列和ZnS/ZnO复合双层纳米棒阵列. 使用X射线粉末衍射仪、 扫描电子显微镜、 高分辨透射电子显微镜、 X射线光电子能谱仪等对产物的组成、 结构及形貌进行了表征. 讨论了表面活性剂在液相合成中对产物形貌的调控作用. 通过室温发射光谱的测定, 研究了所得纳米阵列材料的发光性质.