Wettability of porous two‐dimensional ZnO nanocrystal films

Large‐scale two‐dimensional ZnO nanocrystal films on aluminum substrate were fabricated by a one‐step hydrothermal method under mild conditions, where all the ZnO nanocrystals had a lamellar structure generally perpendicular to the substrates and formed network‐like porous configurations. The morphologies of the films were dependent on both the reaction temperature and concentration of zinc. The wettability of the ZnO films was assessed by measuring the water contact angle without any surface functionalisation. The porous structures of the as‐prepared films could effectively enhance its hydrophobicity and the water contact angle ranged from 40° to 135° depending on the surface morphology and the arrangement of ZnO planes, indicating a simple and promising route to make aluminum surface waterproof and even self‐cleaning. The hydrophobic ZnO surface could be switched to hydrophilic state by UV irradiation.     

Photocurrent detection of chemically tuned hierarchical ZnO nanostructures grown on seed layers formed by atomic layer deposition

We demonstrate the morphological control method of ZnO nanostructures by atomic layer deposition (ALD) on an Al₂O₃/ZnO seed layer surface and the application of a hierarchical ZnO nanostructure for a photodetector. Two layers of ZnO and Al₂O₃ prepared using ALD with different pH values in solution coexisted on the alloy film surface, leading to deactivation of the surface hydroxyl groups. This surface complex decreased the ZnO nucleation on the seed layer surface, and thereby effectively screened the inherent surface polarity of ZnO. As a result, a 2-D zinc hydroxyl compound nanosheet was produced. With increasing ALD cycles of ZnO in the seed layer, the nanostructure morphology changes from 2-D nanosheet to 1-D nanorod due to the recovery of the natural crystallinity and polarity of ZnO. The thin ALD ZnO seed layer conformally covers the complex nanosheet structure to produce a nanorod, then a 3-D, hierarchical ZnO nanostructure was synthesized using a combined hydrothermal and ALD method. During the deposition of the ALD ZnO seed layer, the zinc hydroxyl compound nanosheets underwent a self-annealing process at 150 °C, resulting in structural transformation to pure ZnO 3-D nanosheets without collapse of the intrinsic morphology. The investigation on band electronic properties of ZnO 2-D nanosheet and 3-D hierarchical structure revealed noticeable variations depending on the richness of Zn-OH in each morphology. The improved visible and ultraviolet photocurrent characteristics of a photodetector with the active region using 3-D hierarchical structure against those of 2-D nanosheet structure were achieved.     

CuNi纳米晶的可控合成及Pt/CuNi催化剂催化肉桂醛加氢性能

采用水热法制备了CuNi二元金属纳米晶。以水合肼为还原剂,探究水热合成温度、表面活性剂[乙二胺（EDA）、聚乙烯吡咯烷酮（PVP）、十六烷基三甲基溴化铵（CTAB）]对CuNi纳米晶形貌的影响。随水热合成温度的升高（60℃、90℃、120℃、150℃）,Cu²⁺、Ni²⁺的还原速率加快,有利于形成Cu@Ni核壳结构。以EDA为表面活性剂时,制备的CuNi二元金属纳米晶在120℃和150℃时分别呈现花状和海胆状。此外,以CuNi纳米晶为催化剂载体,采用化学置换法负载贵金属Pt合成了Pt/CuNi三元金属催化剂。X射线粉末衍射（XRD）、扫描电子显微镜（SEM）、扫描电镜X射线能谱（SEM-EDS）、X射线光电子能谱（XPS）、高角度环形暗场扫描透射（HAADF-STEM）和元素面扫（STEM-EDS）表征结果表明,Pt/CuNi催化剂纳米结构为小岛状的Pt纳米团簇负载于CuNi纳米晶。其中,Pt/CuNi-120-EDA（120为水热合成温度,EDA为制备CuNi纳米晶时添加的表面活性剂）催化剂表面具有较丰富的缺陷位和活性位点,使其在肉桂醛加氢反应中表现出最佳的催化性能（80℃下对苯丙醇的产率达100%）。     

pH dependent morphology and texture evolution of ZnO nanoparticles fabricated by microwave-assisted chemical synthesis and their photocatalytic dye degradation activities

ZnO nanostructures are well-known photocatalysts for the degradation of toxic organic dyes and their morphology, size, and other physicochemical properties play important roles in their photocatalytic performance. To study the effect of size, morphology, and synthesis conditions in photocatalytic performance, we synthesized ZnO nanoparticles of different morphologies through a simple microwave-assisted chemical process at different pH values of the reaction mixture. Different pH values of the reaction mixture produced ZnO nanoparticles of different morphologies and sizes. The nature of the pH controlling agent and final pH of the reaction mixture were seen to have considerable effects on the lattice parameters and microstrain of the ZnO nanocrystals, along with their photocatalytic performance. We observed that while the ZnO nanostructures synthesized at very high pH values of the reaction mixture have a high specific surface area, their photocatalytic activity is higher when they are synthesized at acidic pH or pH near the isoelectric point of ZnO. The results demonstrate that the photocatalytic activity of ZnO nanostructures not only depends on their size or specific surface area but also strongly depends on the concentration of catalytic sites at their surface.     

SnO2/ZnO复合中空纤维材料的制备及其光催化性能

采用天然棉花为模板制备了具有高光催化活性的SnO2/ZnO复合中空纤维光催化材料;利用X-射线衍射(XRD)、扫描电子显微镜(SEM)技术对其相结构和形貌进行了表征;以亚甲基蓝(MB)的脱色降解为模型反应,考察了Sn4+和Zn2+物质的量比为0.1∶1时煅烧温度对其催化性能的影响。实验结果表明:制备的样品为复制了棉花纤维模板形貌、具有中空结构的SnO2和ZnO半导体复合材料(SnO2/ZnO);煅烧温度对材料SnO2/ZnO的结晶度、晶粒大小﹑表面微结构和催化性能等有显著影响;650℃左右所得样品在太阳光下的催化活性最好,1 h可使MB溶液的脱色降解率达100%;该材料易于离心分离,具有良好的催化活性和重复使用性能。     

Preparation of Cu/ZnO catalyst using a polyol method for alcohol-assisted low temperature methanol synthesis from syngas

A polyol method was used to prepare Cu/ZnO catalysts for alcohol-assisted low temperature methanol synthesis from syngas. Unlike conventional low temperature methanol synthesis, ethanol was employed both as a solvent and a reaction intermediate. Catalyst characterization revealed that Cu/ZnO catalysts were successfully and efficiently prepared using the polyol method. Various preparation conditions such as PVP concentration and identity of ZnO precursor strongly influenced the catalytic activity of Cu/ZnO catalysts. Copper dispersion and catalyst morphology played key roles in determining the catalytic performance of the Cu/ZnO catalyst in alcohol-assisted low temperature methanol synthesis. A high copper dispersion and platelike Cu/ZnO structure led to high catalytic activity. Among the catalysts tested, 5_Cu/ZnO_Zn(Ac)₂ had the best catalytic performance due to its high copper dispersion.     

Effect of PVP on gas-sensing properties of ZnO micro/nanostructure materials in SDS-PVP composite

ZnO is often used as gas sensor. In order to increase the sensitivity of the sensors, many methods are used to change the gas-sensing properties. In this paper, ZnO was synthesized by hydrothermal method using Zn (NO₃)₂ as a zinc source. Sodium lauryl sulfate (SDS) and polyvinylpyrrolidone (PVP) were added into the system to control microstructure and surface morphology of ZnO nanoparticles. The SDS was kept constant, and the PVP was changed. The morphology and composite were investigated by field emission scanning electron microscopy and X-ray diffraction. The chemical valence of the elements was determined by X-ray photoelectron spectroscopy. The sensing properties were investigated at different PVP components. It is found that ZnO has a red zinc structure. When the m_SDS:m_PVP = 1:1, the sensing sensitivity is best. The mechanism of equivalent matching structure optimization performance is proposed.     

以层柱黏土为载体固定辣根过氧化物酶

引 言 辣根过氧化物酶(HRP)能在较宽的温度、pH值、污染物浓度和盐度范围内将多种芳香性化合物催化氧化为酚氧自由基,它们之间可聚合生成溶解性较差的聚合物从溶液中沉淀出来,便于采用混凝法对其进行去除[1-2].许多学者将该酶用于含酚废水处理中,取得了较好的效果.然而,传统酶催化方法中使用的大多是溶液酶,不仅不能循环使用以节省费用,而且易受废水中其他污染物的影响,稳定性差,加上酶的费用较高,因此酶法在废水处理中尚未得到有效推广应用[3].国内外学者研究发现酶固定化后稳定性大大提高,可重复或连续使用,这样不仅降低了废水处理的成本,而且还避免了蛋白质的污染等问题[4].     

Synthesis,characterization, and photocatalytic properties of ZnO nano-flower containing TiO2 NPs

In this study, TiO₂-impregnated ZnO nano-flowers were synthesized by one-pot hydrothermal process. Aqueous suspension containing ZnO precursor and commercial TiO₂ NPs (P25) is heated at 140 °C for 2 h. The morphology and structure of as-synthesized particles were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), which revealed that TiO₂ NPs were attached on the surface of ZnO flower. It was observed that the presence of TiO₂ NPs in the hydrothermal solution could sufficiently decrease the size of ZnO flower. The hybrid nanostructure, with unique morphology, obtained from this convenient method (low temperature, less time, and less number of reagents) was found to be effective photocatalyst under UV-irradiation.     

Immobilization of invertase onto crosslinked poly(p‐chloromethylstyrene) beads

Invertase was immobilized onto poly(p‐chloromethylstyrene) (PCMS) beads that were produced by a suspension polymerization with an average size of 186 μm. The beads had a nonporous but reasonably rough surface. Because of this, a reasonably large external surface area (i.e., 14.1 m²/g) could be achieved with the proposed carrier. A two‐step functionalization protocol was followed for the covalent attachment of invertase onto the bead surface. For this purpose, a polymeric ligand that carried amine groups, polyethylenimine (PEI), was covalently attached onto the bead surface by a direct chemical reaction. Next, the free amine groups of PEI were activated by glutaraldehyde. Invertase was covalently attached onto the bead surface via the direct chemical reaction between aldehyde and amine groups. The appropriate enzyme binding conditions and the batch‐reactor performance of the immobilized enzyme system were investigated. Under optimum immobilization conditions, 19 mg of invertase was immobilized onto each gram of beads with 80% retained activity after immobilization. The effects of pH and temperature on the immobilized invertase activity were determined and compared with the free enzyme. The kinetic parameters K_M and V_M were determined with the Michealis–Menten model. K_M of immobilized invertase was 1.75 folds higher than that of the free invertase. The immobilization caused a significant improvement in the thermal stability of invertase, especially in the range of 55–65°C. No significant internal diffusion limitation was detected in the immobilized enzyme system, probably due to the surface morphology of the selected carrier. This result was confirmed by the determination of the activation energies of both free and immobilized invertases. The activity half‐life of the immobilized invertase was approximately 5 times longer than that of the free enzyme. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1268–1279, 2002     

Methanol synthesis over a Zn-deposited copper model catalyst

Methanol synthesis by the hydrogenation of CO₂ over Zn-deposited polycrystalline Cu was studied using surface science techniques. The Zn sub-monolayer was oxidized by the reaction mixture during the reaction at 523 K, leading to the formation of ZnO species. The kinetic results definitely showed that the ZnO species on the Cu surface promoted the catalytic activity of methanol formation, where the activity of Cu increased by a factor of 6 at the Zn coverage of 0.17. A volcano-shaped curve was obtained for the correlation between the Zn coverage and the catalytic activity, which was very similar to the correlation curve between the oxygen coverage and the specific activity for methanol formation previously obtained for the Cu powder catalysts. The role of ZnO in Cu/ZnO based catalysts was ascribed to the stabilization of Cu⁺ species by the ZnO moieties on the Cu surface.     

Hydrothermal growth of ZnO nanostructures from nano-ZnO seeded in P(MMA-co-BA) matrix

Nano-ZnO synthesized by hydrothermal reaction were embedded in poly(methyl methacrylate-co-butyl acrylate) matrix (P(MMA-co-BA)) to produce the nano-ZnO/P(MMA-co-BA) nanocomposites via in-situ polymerization at 85 °C. The nano-ZnO/P(MMA-co-BA) nanocomposites were hydrothermal treated in the mixture solution of Zn(NO₃)₂·6H₂O and NH₄OH at 90 °C under various pH (i.e.7, 8, 9 and 10) and treatment time (i.e. 4, 6, 8, 10, 12 and 24 hrs). The nano-ZnO could act as seeding particles for hydrothermal growth of ZnO nanostructures on the surfaces of nanocomposites. The higher pH of basic solutions used in the hydrothermal treatment, the higher amount of Zn(OH)₄²⁻nuclei would be created, leading to a modification of the ZnO morphology from nano-nuclei to nanorods, nanorods bushes (flower-like nanostructure) and nanofibers with nanospine. The increase of hydrothermal treatment time resulted in the increases of amount and length of multidirectional grown ZnO nanorods. Data of the contact angle measurement exhibited the increase of hydrophobicity of the nano-ZnO/P(MMA-co-BA) nanocomposites after hydrothermal growth of ZnO nanostructures. The nanocomposites treated at pH = 10 for 24 hrs shows the highest hydrophobicity with the contact angle of 121˚. In addition, the thermal stability of the nano-ZnO/P(MMA-co-BA) could be improved by the formation of hydrothermal grown ZnO nanostructure on the nanocomposite surface.     

Experimental and theoretical study on catalytic ozonation of humic acid by ZnO catalyst

Ozonation and catalytic ozonation of humic acid (HA) in the presence of ZnO were examined in a batch scale reactor. The degradation of HA by catalytic ozonation was found to be much more effective than ozonation alone. The quantum chemistry calculations showed that the reaction of the O₃ disproportionation on the surface of ZnO corresponds to the barrierless mechanism. The activation energy of the transition state formation was ?5.25 eV. The active oxygen atom formed on the surface of ZnO was found as interacting with both water molecules and dissolved organic molecules, which might lead to further oxidizing reactions.     

Role of ZnO in Cu/ZnO/Al2O3 catalyst for hydrogenolysis of butyl butyrate

For hydrogenolysis of butyl butyrate (BB), a series of Cu/ZnO/Al₂O₃ catalysts with different metal compositions were prepared, and characterized by N₂O chemisorption for measuring Cu surface area and by chromatographic experiment for determining the heat of BB adsorption. As a result, the presence of ZnO in Cu-based catalysts was found to enhance the catalytic activity of Cu due to dual function of ZnO. The Cu surface area was linearly correlated with the butanol productivity, demonstrating that ZnO exerts the structural function in Cu/ZnO/Al₂O₃ catalysts. Additionally, the role of ZnO as a chemical contributor was revealed such that its presence leads to lower activation energy of the surface reaction, thus resulting in higher Cu catalytic activity obtained at a low temperature such as 200 °C. Consequently, optimizing the Cu/Zn ratio in Cu/ZnO/Al₂O₃ catalyst is required to tune its structural and chemical characteristics of Cu metals, and thus to obtain a higher activity on the hydrogenolysis reaction.     

Mechanochemical Treatment of Amorphous Silica Powder for Glasses Without Firing

An amorphous silica powder was subjected to mechanical and hydrothermal treatment. Silanol surface groups, which play an active role in the chemical modification of silica, were produced by these two treatments. The surface activity of raw and treated powders was measured as the amount of dissolved Si⁴⁺ ion in ammonia (NH₃) and potassium hydroxide (KOH) solutions at different concentrations. KOH solution was more effective than NH₃ solution in activating the surface of the silica powder. Nonfiring glass was successfully fabricated using mechanochemically treated silica powder. Glass properties such as morphology and transparency were analyzed using scanning electron microscope and UV–vis–NIR techniques. Possible reaction mechanisms of powder surface activation occurring during hydrothermal and condensation processes are also discussed.     

CdS quantum dots sensitized ZnO spheres via ZnS overlayer to improve efficiency for quantum dots sensitized solar cells

This paper reports the preparation of three-dimensional ZnO spheres by using a hydrothermal method and their application to quantum dots sensitized solar cells (QDSSCs). After achieving the desired thickness of sensitized CdS quantum dots (QDs) for ZnO spheres, ZnS overlayer was deposited on the surface of CdS/ZnO photo-anodes to further improve the photoelectric properties. CdS QDs and ZnS overlayer were deposited by successive ionic layer adsorption and reaction (SILAR) method. The surface morphology and crystal structure of the samples were verified by field-emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The CdS QDs sensitized solar cells were ameliorated via using ZnS as a protection-layer between quantum dots and electrolyte. As a result, the power conversion efficiency (η) has been increased from 0.60 to 1.43% after being treated by ZnS overlayer for CdS/ZnO photo-anodes.     

物理化学综合实验设计一纳米ZnO的制备、表征及光催化性能测试

分别采用水热和沉淀法制备ZnO光催化剂，利用X射线粉末衍射（XRD）和扫描电镜（SEM）对其物相和外貌进行分析观测．了解表征手段所反映的材料的物质结构信息。通过降解亚甲基蓝实验比较不同制备条件下所得ZnO的光催化性能。了解催化剂制备方法对其晶相、形貌及催化性能的影响。     

氧化锌催化丁二酸二甲酯和碳酸乙烯酯的耦合反应

研究了ZnO催化碳酸乙烯酯和丁二酸二甲酯耦合反应合成聚丁二酸乙二醇酯预聚体和碳酸二甲酯的新工艺。考察了ZnO催化剂焙烧温度对耦合反应的催化活性,优化了反应条件。并对ZnO催化剂进行XRD、BET和NH₃-TPD表征。以FTIR和¹H NMR表征聚丁二酸乙二醇酯预聚体。结果表明,在225~235℃,EC/DMSu摩尔比为2,催化剂/(EC+DMSu)摩尔比为0.005,反应时间为3 h的反应条件下,碳酸二甲酯收率为59.7%,聚丁二酸乙二醇酯预聚物的特性黏度为0.3857 dl·g^-1。通过XRD和NH₃-TPD分析,推测ZnO表面的晶体缺陷和弱酸性是影响耦合反应催化活性的原因。     

Hydroxylation mechanism of phase regulation of nanocrystal BaTiO3 synthesized by a hydrothermal method

Understanding the phase regulation mechanism of BaTiO₃ synthesized by a hydrothermal method is a complicated and challenging task. Here, we successfully prepared cubic and tetragonal BaTiO₃ single nanocrystals by changing the ratio of water and ethanol in the solvent. We confirm that the BaTiO₃ phase is mainly affected by the hydroxylation process due to the reaction with solvent. In particular, ethanol can be catalytically oxidized by titanium atoms, cause BaTiO₃ hydroxylation and promote the formation of a cubic phase. In the mixed solution of ethanol and water, the hydroxylation process is suppressed, which facilitates the formation of the tetragonal phase. The relationship framework between the solvent ratio, phase structure and hydroxyl defects of BaTiO₃ is established. Tetragonal BaTiO₃ with fewer hydroxyl defects can promote charge transfer and surface reaction after polarization, thereby enhancing their photoelectric catalytic performance. This work provides references for the controllable synthesis of ferroelectric nanocrystals by hydrothermal methods and new insight for the utilization of polarization in photoelectrocatalysis applications.     

Modified hydrothermal treatment route for high-yield preparation of nanosized ZrO2

Nanosized ZrO₂ particles are applied in high-performance thermal barrier coatings and catalyst carriers. To synthesize nanosized zirconia, precipitation from aqueous solutions followed by hydrothermal treatment is widely conducted. In this work, a modified hydrothermal treatment route is described for high-yield fabrication of well-dispersible nanosized t–ZrO₂. Zirconium oxychloride and sodium hydroxide were used as the precursor and precipitant, respectively. N, N-bis(2-hydroxyethyl) glycine (bicine) was used as surface stabilizer to inhibit the early agglomeration of nuclei, and ultrasonication was used to enhance the dispersion of ZrO₂ nanocrystals. The hydrothermal treatment was optimized for reaction temperature, time, fill fraction, and solid content. The synthesized zirconia was characterized using X-ray diffraction, dynamic light scattering, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The yield of zirconia increased to 134 g/L after hydrothermal. Tetragonal ZrO₂ obtained with hydrothermal treatment at 200 °C for 8 h at a fill fraction of 80% has a good dispersibility, with an average particle size of 20 nm and a narrow size distribution.