ZnO自组装薄膜的可控生长及其光催化性能

通过改变工艺参数, 制得了粒径可控的ZnO自组装薄膜. 该薄膜在可见光区域出现了光子带隙. 以染料甲基橙的光催化降解为模型评价了ZnO自组装薄膜的光催化活性. 利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征了ZnO的晶体结构和微观形貌. 实验结果表明, ZnO自组装薄膜在太阳光照射下表现出良好的光催化性能, 其光催化活性随着ZnO颗粒粒径的减小而提高. ZnO自组装薄膜光催化降解甲基橙的反应符合一级反应动力学规律.     

低共熔溶剂辅助水热法合成分层球状微/纳米ZnO晶体及其光催化性能

使用尿素-氯化胆碱低共熔溶剂(UCC-DES),采用水热合成和反溶剂(乙醇)法,以化工材质ZnO粉末为原料制备了分层的球状微/纳米ZnO晶体.分析了反应时间、反溶剂的种类和含量对ZnO晶体形貌的影响以及ZnO晶体析出的原因.并将制备的分层球状ZnO微/纳米晶体应用于光催化降解甲基橙.结果表明,制备的ZnO晶体对甲基橙有良好的光催化降解性能.     

Fe-Ni 共掺杂 ZnO 的制备及其光催化降解甲基橙活性

 采用溶液法制备了 Fe-Ni 共掺杂 ZnO 光催化剂, 并运用 X 射线衍射、扫描电镜和原子发射光谱等对催化剂进行了表征. 以甲基橙 (MO) 为模型污染物, 评价了样品的光催化活性, 考察了甲基橙初始浓度及其 pH 值, 以及催化剂用量等对光催化反应性能的影响. 结果表明, Fe-Ni 共掺杂降低了 ZnO 的结晶度, 并促进了晶粒的长大. 光催化降解反应表明, Fe-Ni 共掺杂显著提高了 ZnO 光催化降解甲基橙的活性, 当催化剂用量为 0.6 g/L, 经 120 min 紫外光照射时, 可使甲基橙溶液 (10 mg/L) 降解率达到 93.5%. 关键词：铁; 镍; 共掺杂; 氧化锌; 光催化; 甲基橙; 降解     

ZnO/Ag微米球的合成与光催化性能

用微波辅助多元醇法对预先制备的ZnO微米球进行修饰,合成了载银氧化锌微米球（ZnO/Ag）. 利用X射线衍射仪、场发射扫描电子显微镜、透射电子显微镜、X射线光电子能谱仪、紫外-可见双光束分光光度计和光致发光光谱仪等对样品的结构、形貌和光学性能进行了表征. 在紫外光照射下,通过亚甲基蓝的降解反应研究了样品的光催化活性. 结果表明,所制备的ZnO/Ag微米球是由面心立方的Ag纳米颗粒附着在纤锌矿结构的ZnO球表面形成;与ZnO相比,ZnO/Ag的紫外-可见光吸收光谱发生明显红移,在紫外和可见光范围均有较强的吸收;随着Ag含量的增加,ZnO/Ag荧光光谱强度先减弱后增强;与ZnO相比,ZnO/Ag的光催化活性明显提高,AgNO₃ 浓度为0.05 mol/L时制得的ZnO/Ag光催化活性最高.     

ZnO纳米管的光学性质及其对甲基橙降解的光催化活性

以十二烷基硫酸钠为模板剂采用水热法合成了ZnO纳米管,以尿素和ZnSO4为原料制备了ZnO纳米颗粒,并应用透射电镜、x射线衍射、光致发射光谱、拉曼光谱、比表面积测定、傅里叶红外光谱和紫外-可见漫反射光谱等技术对样品进行了表征.结果表明,ZnO纳米管的比表面积较大,在λ≈650nm的可见光波段ZnO纳米管开始出现吸收峰,而ZnO纳米颗粒在可见光波段几乎没有吸收.ZnO纳米管和纳米颗粒在紫外光照射下均对甲基橙有降解作用,其中ZnO纳米管的光催化活性较高.随着催化剂用量的增加和光照时间的延长,甲基橙降解率逐渐提高;甲基橙浓度的增大使甲基橙降解率降低.     

电场对TiO2纳米膜光催化性能的影响

 以泡沫镍为基材,采用溶胶-凝胶法制备了TiO2纳米膜光催化剂. 在自制外加电场光催化反应装置中,对催化剂施加一定的偏电压,研究了甲基橙溶液的光电催化降解反应,考察了偏压极性、阳极偏压和甲基橙初始溶液浓度等对降解效率的影响,并比较了光电催化与光催化、光解对甲基橙溶液降解的差异. 结果表明,外加阳极偏压形成的电场可以较大幅度提高甲基橙溶液的降解效率. 从半导体和量子力学理论出发探讨了电场促进光催化反应的作用机理.     

纳米SnO2／ZnO复合氧化物的制备及制备条件对光催化性能的影响

以SnCl4·5H2O、ZnSO4·7H2O、NH3·H2O为原料,采用共沉淀法制备出纳米SnO2/ZnO复合光催化剂,以降解甲基橙为模型反应,考察了不同条件制备的复合氧化物的光催化活性,并用TEM、XRD测试手段对其进行了表征。结果表明,ZnO复合SnO2后,光催化活性明显提高,但是焙烧温度超过900℃后,其光催化活性又大大降低。     

Cu2+/TiO2对甲基橙的光催化降解机理

以自制的掺铜离子的混晶型二氧化钛为光催化剂,考察了甲基橙光催化降解过程中pH值和光源的影响,提出了两种不同的光催化降解机理:在高压汞灯照射下,TiO2的价带电子被激发到导带,光生电子和空穴主要通过Cu2+ 的短路循环而复合,光催化剂的活性降低;在太阳光照射下,甲基橙发生自身光敏化氧化反应,受激电子从单线态或三线态的甲基橙分子跃迁到TiO2的导带,Cu2+起到电荷传递中继站的作用,加速了注入电子向H2O2的转移,从而促进了甲基橙的光催化降解。     

微波助离子液体中Y掺杂TiO_2光催化剂制备及微波强化光催化活性

在微波助离子液体介质中制备稀土元素Y掺杂改性TiO_2光催化剂,以提高催化剂的光催化降解活性,用XRD、SEM和BET等测试手段对催化剂结构进行表征;以甲基橙溶液和苯酚溶液为模拟污染物,分别在紫外光照(UV)和微波辐射-紫外光照(MW-UV)条件下考察TiO_2-Y催化剂的光催化活性;以对苯二甲酸作为荧光探针利用荧光技术检测TiO_2-Y催化剂表面所产生的羟基自由基,并对光催化降解反应进行动力学分析,探索了光催化降解反应机理.实验结果表明,通过优化反应条件后制得的TiO_2-Y催化剂具有较高光催化活性和热稳定性,在UV和UV-MW条件下降解甲基橙和苯酚溶液1.5h后,甲基橙降解率分别为98.3%和99.5%,苯酚降解率分别为97.5%和98.2%.荧光光谱分析表明,TiO_2-Y在MW-UV条件下产生的羟基自由基比UV条件下要多,因而微波辐照具有强化TiO_2-Y降解模拟污染物的作用;反应动力学数据分析表明,TiO_2-Y光催化降解甲基橙溶液反应呈现一级反应动力学规律,其表观速率常数K最大值为0.051 9min-1.     

ZnS微米花的水热合成及光催化性质研究

本文采用简便的水热法一步合成ZnS微米花,通过X射线衍射仪、扫描电子显微镜等表征手段研究了合成产物的形貌及微观结构,并考察了合成产物的光催化性质。合成产物的光催化测试结果表明,在紫外光辐照下,产物对亚甲基蓝、甲基橙和曙红都有很好的降解效果。为了测试产物循环利用的光催化能力,对其进行了5次降解实验,结果显示产物依然保持良好的光催化活性。     

Synthesis and Photocatalytic Properties of Coupled Nanocrystalline ZnO/ZnS in Nation Membrane

T The coupled nanocrystalline ZnO/ZnS was fabricated and immobilized in Nafion membrane by using sodium sulfide (Na_2S) as the single anion precursor. The molar ratio of ZnO to ZnS can be controlled by simply adjusting the reaction time. The as-prepared ZnO/ZnS-Nafion samples were characterized by various methods, including optical absorption, X-ray diffraction and high-resolution transmission electron microscopy. These coupled ZnO/ZnS nanocrystals embedded in Nafion membrane displayed excellent photocatalytic activities for their efficient charge separation properties. A mechanism of ZnO/ZnS nanoparticle fabrication in Nation was deduced from the solubility difference, and the photocatalytic mechanism of coupled ZnO/ZnS was discussed as well.     

ZnO修饰提升花状BiOBr的可见光催化降解罗丹明B性能

以Bi(NO₃)₃·5H₂O、Zn(CH₃COO)₂·2H₂O和NaBr为前驱体,采用简单溶剂热法制备BiOBr/ZnO三维花状微纳米复合材料。采用X射线衍射、扫描电子显微镜、X射线光子能谱、N₂吸附-脱附、光致发光和电子顺磁共振等分析技术对其理化性质进行了表征。通过可见光催化降解罗丹明B(RhB)的实验测试了复合材料的光催化性能。结果表明ZnO含量为5%的BiOBr/ZnO光催化活性最优,RhB降解率在50 min后达到98.3%,其降解速率常数是纯ZnO和BiOBr的6.3倍和3.4倍,并且具有较高的稳定性。复合材料光催化性能增强的可能原因为ZnO的引入增强了可见光的吸收和光生载流子的电荷分离效率。     

Biomineralization‐Inspired Preparation of Zinc Hydroxide Carbonate/Polymer Hybrids and Their Conversion into Zinc Oxide Thin‐Film Photocatalysts

The development of ZnO thin films has been achieved through the conversion of zinc hydroxide carbonate thin‐film crystals. Crystallization of this compound is induced by a biomineralization‐inspired method with polymer‐stabilized amorphous precursors. The crystals grow radially on polymer matrices, leading to the formation of zinc hydroxide carbonate/polymer thin‐film hybrids that fully cover the substrate. These hybrids are converted into ZnO and retain their thin‐film morphologies. The resultant ZnO thin films exhibit a preferential crystallographic orientation that is attributed to the alignment of zinc hydroxide carbonate crystals before conversion. In addition, a photocatalytic function of the ZnO thin films has been demonstrated by analyzing the oxidation reaction of 2‐propanol. The biomineralization‐inspired approach reported herein is a promising way to develop ZnO materials with controlled morphologies and structures for photocatalytic applications.     

Structural,optical, electrical,and photocatalytic properties of manganese doped zinc oxide nanocrystals

Manganese-doped and undoped ZnO nanocrystals were synthesized via wet-chemical methods. The structure, physico-chemical, electrical and optical properties of the as-prepared products were characterized by using the X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PLS) and electrochemical impedance spectroscopy (EIS) techniques. The photocatalytic activity of Mn-doped ZnO nanocrystal (mixed phases) has been examined under the visible-irradiation by using photocatalytic oxidation of rhodamine B (RhB) dye as a model reaction, and compared with that of known system such as pure ZnO nanocrystal (single-phase). The results showed that Mn doped ZnO nanocrystals bleaches RhB much faster than undoped ZnO upon its exposure to the visible light. The enhancement of the photocatalytic activity was discussed as an effect due to the Mn doping in the Mn-doped ZnO semiconductors, which shifts the optical absorption edge to the visible region and alters the electron-hole pair separation conditions. These factors are responsible for the higher photocatalytic performance of Mn/ZnO composites.     

Photocatalytic activity and related surface properties of transparent ZnO films prepared by a low-temperature aqueous route

Transparent ZnO were prepared using solutions with various trisodium citrate concentrations by a spin-spray method at 90°C. The morphological and structural characteristics, as well as photocatalytic activity of the resulting ZnO films were examined with respect to the added trisodium citrate concentration. Photocatalytic activities of the ZnO films were evaluated from photodecomposition of methylene blue (MB) in aqueous solution. With increasing citrate concentrations, the ZnO films came to have higher transmittances in visible region but lower MB decomposition rate. Both high transmittance and high photocatalytic activity were achieved in the ZnO film prepared in the citrate concentration of 0.5 mm. The possible mechanism for the difference in photocatalytic activity by the samples prepared with the various concentrations of citrate was discussed from the viewpoint of film texture, crystal orientation and surface chemical state.     

Molecular dynamics simulations of inverse sodium dodecyl sulfate (SDS) micelles in a mixed toluene/pentanol solvent in the absence and presence of poly(diallyldimethylammonium chloride) (PDADMAC)

Well-aligned ZnO nanorods (NRs) were grown on indium-tin-oxide (ITO) slide by the hydrothermal method and used as templates for preparing ZnO/Au composite nanoarrays. The optical and morphological properties of ZnO/Au composites under various HAuCl(4) concentrations were explored via UV-vis absorption spectroscopy, photoluminescence (PL) and scanning electron microscopy (SEM). The density and size of gold nanoparticles (Au NPs) on ZnO NRs can be controlled by adjusting the concentration of HAuCl(4). The optimal ZnO/Au composites display complete photocatalytic degradation of methyl blue (MB) within 60 min, which is superior to that with pure ZnO NRs prepared by the same method. The reason of better photocatalytic performance is that Au NPs act as electron traps and it prevents the rapid recombination of electrons and holes, resulting in the improvement of photocatalytic efficiency. The photocatalytic performance of ZnO/Au composites is mainly controlled by the density of Au NPs formed on ZnO NRs. The application in rapid photodegradation of MB shows the potential of ZnO/Au composite as a convenient catalyst for the environmental purification of organic pollutants.     

Preparation, characterization and photocatalytic performance of Mo-doped ZnO photocatalysts

A series of Mo-doped ZnO photocatalysts with different Mo-dopant concentrations have been prepared by a grinding-calcination method.The structure of these photocatalysts was characterized by a variety of methods,including N 2 physical adsorption,X-ray diffraction(XRD),scanning electron microscopy(SEM),Fourier transform infrared(FT-IR) spectroscopy,photoluminescence(PL) emission spectroscopy,and UV-vis diffuse reflectance spectroscopy(DRS).It was found that Mo 6+ could enter into the crystal lattice of ZnO due to the radius of Mo 6+(0.065 nm) being smaller than that of Zn 2+(0.083 nm).XRD results indicated that Mo 6+ suppressed the growth of ZnO crystals.The FT-IR spectroscopy results showed that the ZnO with 2 wt.% Mo-doping has a higher level of surface hydroxyl groups than pure ZnO.PL spectroscopy indicated that ZnO with 2 wt.% Mo-doping also exhibited the largest reduction in the intensity of the emission peak at 390 nm caused by the recombination of photogenerated hole-electron pairs.The activities of the Mo-doped ZnO photocatalysts were investigated in the photocatalytic degradation of acid orange II under UV light(λ = 365 nm) irradiation.It was found that ZnO with 2 wt.% Mo-doping showed much higher photocatalytic activity and stability than pure ZnO.The high photocatalytic performance of the Mo-doped ZnO can be attributed to a great improvement in the surface properties of ZnO,higher crystallinity and lower recombination rate of photogenerated hole-electron(e-/h+) pairs.Moreover,the undoped Mo species may exist in the form of MoO3 and form MoO3 /ZnO heterojunctions which further favors the separation of e-/h+ pairs.     

Enhanced Raman scattering and photocatalytic activity of Ag/ZnO heterojunction nanocrystals

In this work, we study the enhancement of Raman signals and photocatalytic activity of Ag/ZnO heterojunctions with an Ag content of 1 at.%, which were synthesized by photochemical deposition of Ag nanoparticles onto pre-synthesized ZnO nanorods. A strong interaction between Ag and ZnO nanocrystals were evidenced by XPS and UV-vis spectroscopy. The binding energy of Ag nanoparticles shifts toward lower energy compared to that of pure Ag nanoparticles, revealing that electrons transfer from Ag to the ZnO nanocrystals. The red shift of the plasmon absorption peak of Ag nanoparticles in Ag/ZnO heterojunctions further confirms the strong interaction between the two components. This strong interaction, arising from the coupling between Ag and ZnO nanocrystals, is responsible for the enhancement of Raman signals and photocatalytic activity of the Ag/ZnO heterojunctions.