Systematic investigation on morphologies, forming mechanism, photocatalytic and photoluminescent properties of ZnO nanostructures constructed in ionic liquids

In this contribution, a series of shape-controllable ZnO nanostructures were synthesized in ionic liquids by a simpler, only one-step, low-temperature route, and characterized by XRD, XPS, TEM, HRTEM, SAED, EDXA, SEM, FTIR, surface area measurement and photoluminescence. We mainly investigate the effect of cations of ionic liquids on the shape of ZnO nanostructures and the forming mechanism of ZnO nanostructures in ionic liquids, as well as the luminescent property and photocatalytic activity for the degradation of Rhodamine B. The results show that the longer alkyl chain at position-1 of the imidazole ring of the ionic liquid will hinder the ZnO nanostructures from growing longer, and the hydrogen bonds may play a crucial role for the directional growth of the 1D nanocrystals. The photoluminescent study shows that the as-obtained ZnO nanostructures exhibit a unique green emission, indicating the existence of oxygen vacancies in the ZnO nanostructures. Importantly, the as-obtained ZnO nanostructures prepared in different ionic liquids show strong size/shape-dependent photocatalysis activity for degradation of Rhodamine B, and the well-dispersed homogeneous ZnO nanoparticles and nanowires display high photocatalytic activity. The investigation of photodegradation kinetics of Rhodamine B indicates that the photodegradation process obeys the rule of a first-order kinetic equation ln( C(0)/ C) = kt. This is the first systematic investigation on the relationship between the structure of ionic liquids and the morphology of ZnO nanostructures.     

咪唑类离子液体辅助水热法合成棒状微/纳米ZnO晶体

以醋酸锌和氢氧化钠为原料, 以水和含不同长度烷基链的咪唑类氯盐离子液体的混合物作为反应介质, 采用水热法合成出不同形貌的微/纳米ZnO晶体, 用扫描电子显微镜(SEM)和X射线衍射仪(XRD)对合成的ZnO晶体进行表征. 研究了烷基链长度、 离子液体用量、 反应时间以及反应温度对形成棒状ZnO晶体形貌的影响. 实验结果表明, 所制备的棒状ZnO晶体样品均为六方晶系结构. 在棒状ZnO晶体的制备过程中, 控制反应温度, 选择不同的离子液体及其用量十分重要.     

离子液体中不同形貌ZnO纳米材料的合成及表征

在不同的咪唑基离子液体中通过微波加热合成出了ZnO的片状聚集体、棒状聚集体和塔棒聚集体等纳/微米结构, 考察了不同合成条件对ZnO形貌的影响, XRD表明产物为六方相纤锌矿ZnO结构, SEM和TEM表明产物形貌主要分为片的聚集体和棒的聚集体, 电子衍射表明ZnO棒具有单晶结构, 片的聚集体的PL谱表明在室温下这种形貌的ZnO具有很强的绿光发射和弱紫外光发射现象.     

Novel ascorbic acid based ionic liquids for the in situ synthesis of quasi-spherical and anisotropic gold nanostructures in aqueous medium

A series of newly designed ascorbic acid based room temperature ionic liquids were successfully used to prepare quasi-spherical and anisotropic gold nanostructures in an aqueous medium at ambient temperature. The synthesis of these room temperature ionic liquids involves, first, the preparation of a 1-alkyl (such as methyl, ethyl, butyl, hexyl, octyl, and decyl) derivative of 3-methylimidazolium hydroxide followed by the neutralization of the derivatised product with ascorbic acid. These ionic liquids show significantly better thermal stability and their glass transition temperature (Tg) decreases with increasing alkyl chain length. The ascorbate counter anion of these ionic liquids acts as a reducing agent for HAuCl4 to produce metallic gold and the alkylated imidazolium counter cation acts as a capping/shape-directing agent. It has been found that the nature of the ionic liquids and the mole ratio of ionic liquid to HAuCl4 has a significant effect on the morphology of the formed gold nanostructures. If an equimolar mixture of ionic liquid and HAuCl4 is used, predominantly anisotropic gold nanostructures are formed and by varying the alkyl chain length attached to imidazolium cation of the ionic liquids, various particle morphologies can formed, such as quasispherical, raspberry-like, flakes or dendritic. A probable formation mechanism for such anisotropic gold nanostructures has been proposed, which is based on the results of some control experiments.     

Sliding droplets on superomniphobic zinc oxide nanostructures

This study reports on liquid-repellency of zinc oxide nanostructures (ZnO NS). The ZnO NS are synthesized by an easy and fast chemical bath deposition technique. Three different nanostructured surfaces consisting of nanorods, flowers, and particles are prepared, depending on the deposition time and the presence of ethanolamine in the reaction mixture. Chemical functionalization of the ZnO NS with 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFTS) in liquid (PFTS L) and vapor phase (PFTS V) or through octafluorobutane (C(4)F(8)) plasma deposition led to the formation of superomniphobic surfaces. A comprehensive characterization of the wetting properties (static contact angle and contact angle hysteresis) has been performed using liquids composed of deionized water and various concentrations of ethanol (surface tension between 35 and 72.6 mN/m). Depending on the nanostructures morphology, coating nature and liquid employed, high static apparent contact angles θ ≈ 150-160°, and low contact angle hysteresis Δθ ≈ 0° are obtained. The different ZnO NS are characterized using scanning electron microscopy (SEM) and contact angle measurements. The results reported in this work permit preparation of sliding omniphobic surfaces using a simple and low cost technique.     

Understanding the Effect Models of Ionic Liquids in the Synthesis of NH4‐Dw and γ‐AlOOH Nanostructures and Their Conversion into Porous γ‐Al2O3

Well‐dispersed ammonium aluminum carbonate hydroxide (NH₄‐Dw) and γ‐AlOOH nanostructures with controlled morphologies have been synthesized by employing an ionic‐liquid‐assisted hydrothermal process. The basic strategies that were used in this work were: 1) A controllable phase transition from NH₄‐Dw to γ‐AlOOH could be realized by increasing the reaction temperature and 2) the morphological evolution of NH₄‐Dw and γ‐AlOOH nanostructures could be influenced by the concentration of the ionic liquid. Based on these experimental results, the main objective of this work was to clarify the effect models of the ionic liquids on the synthesis of NH₄‐Dw and γ‐AlOOH nanostructures, which could be divided into cationic‐ or anionic‐dominant effect models, as determined by the different surface structures of the targets. Specifically, under the cationic‐dominant regime, the ionic liquids mainly showed dispersion effects for the NH₄‐Dw nanostructures, whereas the anionic‐dominant model could induce the self‐assembly of the γ‐AlOOH particles to form hierarchical structures. Under the guidance of the proposed models, the effect of the ionic liquids would be optimized by an appropriate choice of cations or anions, as well as by considering the different effect models with the substrate surface. We expect that such effect models between ionic liquids and the target products will be helpful for understanding and designing rational ionic liquids that contain specific functional groups, thus open up new opportunities for the synthesis of inorganic nanomaterials with new morphologies and improved properties. In addition, these as‐prepared NH₄‐Dw and γ‐AlOOH nanostructures were converted into porous γ‐Al₂O₃ nanostructures by thermal decomposition, whilst preserving the same morphology. By using HRTEM and nitrogen‐adsorption analysis, the obtained γ‐Al₂O₃ samples were found to have excellent porous properties and, hence, may have applications in catalysis and adsorption.     

Synthesis of Nanotitania on the Surface of Titanium Metal in Ionic Liquids: Role of Water Additions

The anodic oxidation of a titanium metal electrode in two ionic liquids was studied of amorphous titania nanostructures were obtained. The nanostructures are formed only in the case where a hydrophilic ionic liquid (1-butyl-3-methylimidazolium chloride) with addition of some water is used as the electrolyte. The role of water is to provide a sort of construction material (source of oxygen) for titania nanostructures. In the hydrophobic ionic liquid (1-butyl-3-methylimidazolium), the thickness of the anodic oxide increases and no nanostructures are formed.     

四针状纳米氧化锌的热力学函数

采用简单、温和的微乳液水热辅助法合成了尺寸、形貌均匀的四针状ZnO纳米结构,每个结构由四根长约250nm的纳米针组成．基于块体ZnO的热力学函数已知,依据热力学势函数法设计热化学循环,将纳米ZnO与块体ZnO的热力学函数进行了关联．并结合热动力学理论及过渡态理论,利用微量热技术获得了所制备的四针状纳米ZnO在298．15K下的标准摩尔生成焓、标准摩尔生成Gibbs自由能、标准摩尔熵值分别为（-329．37±0．43）kJmol-1,（-318．51±0．03）kJmol-1,（20．36±1．05）Jmol-1 K-1．     

Metal and Metal Oxide Nanostructures Prepared by Electrical Arc Discharge Method in Liquids

In this review, the importance of electrical arc discharge technique in liquids in synthesis of various nanostructures from carbon based materials to metal and metal oxide nanostructures with their general and specific properties, especially the photocatalytic performance of metal oxide nanostructures is studied. The effect of arc current on size distribution, morphology and physicochemical properties of metal and semiconductor nanostructures was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS) and UV–Vis spectroscopy. WO₃ Cubic nanostructures with 30 nm mean particle size were formed during the discharge process in water. Discharge between zinc electrodes in water leads to formation of rod like and semi spherical ZnO nanostructures with 15–20 nm diameter range. ZrO₂ nanoparticles were formed using zirconium electrodes in water. Photodegradation of Rhodamine B (Rh. B) shows that the as prepared nanostructures in this method have potential ability for environmental purifications. Also, using silver electrodes in water leads to formation of silver nanoparticles with 8–15 nm average particle size. Moreover, a novel method for synthesis of gold nanoparticles without using gold electrodes is presented. Finally, the future outlook of this technique in synthesis of various nanocrystalline materials is presented.     

Sb2S3 with various nanostructures: controllable synthesis, formation mechanism, and electrochemical performance toward lithium storage

The size- and shape-controlled synthesis of Sb(2)S(3) nanostructures has been successfully realized by a facile hydrothermal route. A range of dimensional nanostructures, such as one-dimensional nanorods, two-dimensional nanowire bundles, three dimensional sheaf-like superstructures, dumbbell-shaped superstructures, and urchin-like microspheres, could be obtained through introducing different organic complex reagents or ionic liquids to the reaction system. The formation mechanisms of various Sb(2)S(3) nanostructures have been rationally proposed based on the crystal structure and the nature of the complex reagents and the ionic liquid. The effects of experimental parameters on the final product are also discussed in detail. In addition, electrochemical measurements demonstrate that the as-synthesized Sb(2)S(3) nanostructures have higher initial Li intercalation capacity and excellent cyclic performances, which indicates that the as-synthesized Sb(2)S(3) nanostructures could have potential applications in commercial batteries.     

离子液体中微波合成纳米结构的Bi2S3和Bi19Br3S27

在不同咪唑基离子液体中, 利用微波辅助法快速合成了不同形貌的Bi2S3纳米粒子和Bi19Br3S27纳米棒. 利用XRD, TEM和SEM对合成产物进行了结构和形貌的表征. 实验结果表明离子液体在合成过程中对产物的相结构和形貌发挥了重要的作用. 实验中还进一步考察了不同实验条件对产物形貌的影响. 对实验的合成机理进行了初步探讨. 对不同形貌和纳米结构的Bi2S3和Bi19Br3S27进行了UV-Vis光谱分析.     

野草状纳米氧化锌的制备及标准摩尔生成焓

本文采用反相微乳液法制备了尺寸均匀的野草状ZnO纳米结构. 依据热力学势函数法获得了纳米ZnO与块体ZnO标准摩尔生成焓的关系, 并结合微量热技术求得了所制备产物的标准摩尔生成焓, 为研究其它纳米材料的标准摩尔生成焓提供了一种广泛适用的新方法.     

不同形貌ZnO纳米结构的电子显微分析

控制实验合成条件,利用溶胶-凝胶法和化学溶液生长法制备出不同形貌的ZnO纳米结构。采用X射线衍射仪(XRD)、扫描电子显微镜( SEM) 以及透射电子显微镜(TEM)等多种测试手段对ZnO纳米结构的微观形态及晶相进行了分析。结果表明:3种ZnO纳米结构形貌虽不同,但均具有Z nO六方纤锌矿晶相结构。ZnO纳米棒和花状ZnO纳米结构为单晶,生长方向均沿(0001)方向。ZnO纳米球则为多晶。     

Uniform metal (hydr)oxide particles from water/ionic liquid precursor (ILP) mixtures

We have recently shown that the hydrated ionic liquid tetrabutylammonium hydroxide (TBAH) is an efficient ionic liquid precursor (ILP) for the fabrication of ZnO/carbohydrate materials (D. Mumalo-Djokic, W. B. Stern, A. Taubert, Cryst. Growth Des. 2008, 8, 330). The current paper shows that ZnO is just one example out of the large group of technologically important metal (hydr)oxides that can be made using TBAH. Simply by using different metal acetates as precursors in TBAH, it is possible to make a wide variety of metal (hydr)oxides with well-defined size, morphology, and chemical composition. It is also possible to dope metal oxide particles or to synthesize mixed metal oxide particles, and therefore to control properties like magnetism.     

Syntheses of CuO nanostructures in ionic liquids

A simple and efficient approach is developed to fabricate single-crystalline CuO nanostructures through an ionic liquid assisted one-step low-temperature solid-state route.Both nanoparticles(5 nm in size)and nanorods(5-10 nm in diameter and 50-100 nm in length)of monoclinic CuO were obtained. These synthesized CuO nanostructures were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),selected area electron diffraction(SAED),X-ray photoelectron spectros- copy(XPS),energy dispersive spectroscopy(EDS)and nitrogen adsorption analysis.The morpholo- gies of the nanostructures can be controlled by tuning the amount of NaOH and ionic liquids.The growth mechanism of CuO nanostructures is investigated.     

利用双水相分离回收离子液体的研究进展

研究离子液体的分离与回收对于减少离子液体对环境的影响、提高离子液体的利用效率、降低离子液体的应用成本、促进离子液体的工业应用具有重要的意义.本文重点综述了利用无机盐-离子液体双水相、糖-离子液体双水相、聚合物-离子液体双水相和CO2诱导的离子液体双水相技术分离回收离子液体的研究进展,分析了影响离子液体分离回收的关键因素,评价了不同离子液体双水相体系的优缺点,展望了该领域的发展方向及面临的挑战.     

以介孔氧化硅薄膜为模板电沉积合成新型纳米结构

首次以不同孔道结构的介孔氧化硅薄膜为模板,采用电化学沉积的方法,合成了金属铜和半导体氧化锌的纳米材料,并对其结构进行了表征．以六方孔道结构的介孔氧化硅模板获得了直径为7nm的金属铜纳米线阵列;以笼状体心立方孔道结构的模板获得了具有哑铃状形貌的铜单质纳米颗粒．对于氧化锌纳米结构,电化学沉积过程使得氧化锌完全填充氧化硅模板的孔道,分别得到了具有六方和体心立方介孔结构的Zn0/SiO2纳米复合物薄膜．     

分级结构氧化锌的制备及形貌调控

以单一和混合锌盐为锌源, 氢氧化钠为沉淀剂, 丙氨酸和离子液体(IL)为表面活性剂, 通过水热法制备了不同形貌的分级结构氧化锌粉末. 通过X射线衍射仪(XRD)、 扫描电子显微镜(SEM)、 红外光谱仪(IR)和紫外-可见分光光度计(UV-Vis)对样品进行了表征, 并探讨了锌源(单锌盐、 混合双锌盐及三锌盐)、 离子液体种类及用量、 丙氨酸用量和温度等变量对产物形貌的影响, 推测了在分级结构氧化锌形成过程中阴离子对样品形貌的调控作用.     

纳米氧化锌的标准摩尔生成焓

采用微乳液-水热辅助法合成了尺寸、形貌均匀的ZnO纳米棒,其长度约400 nm,直径约50 nm。基于将纳米ZnO与块体ZnO的标准摩尔生成焓相关联,依据热力学势函数法设计热化学循环,获得了纳米ZnO与块体ZnO标准摩尔生成焓的关系。结合微量热技术求算出了下所制备的ZnO纳米棒在298.15 K下的标准摩尔生成焓为(-331.70±0.42)kJ.mol-1。     

Fine-tuning the synthesis of ZnO nanostructures by an alcohol thermal process

A simple and efficient alcohol thermal technique was applied to control the growth of the dimensions and morphology of ZnO nanostructures under mild conditions, where surfactant was not necessary. The size of ZnO nanocrystals increased with growth temperature and they transformed into nanorods with different aspect ratios through tuning the reaction time. The length of nanorods increased significantly with the reaction time, but their thickness only slightly increased. The as-prepared ZnO nanocrystals were monocrystalline and the growth orientation of ZnO nanorods was [001]. Photoluminescence measurements showed a blue shift in violet emission with a reduction in crystal size and revealed the quantum confinement effect. Electron irradiation induced structural damage was observed in the ZnO nanorods synthesized at 120 degrees C. Experimental results proved that the possible growth mechanism of ZnO nanostructures was oriented attachment.