New s-Block Metal Pyridinedicarboxylate Network Structures through Gas-Phase Thin-Film Synthesis

The combined atomic and molecular layer deposition (ALD/MLD) technique offers a unique way to build—both known and previously unknown—crystalline coordination polymer materials directly from gaseous precursors in a high-quality thin-film form. Here, we demonstrate the ALD/MLD of crystalline Li-, Na-, and K-based 3,5-pyridinedicarboxylate (3,5-PDC) thin films; the Li₂-3,5-PDC films are of the known Li-ULMOF-4 crystal structure whereas the other as-deposited crystalline films possess structures not previously reported. Another exciting possibility offered by ALD/MLD is the deposition of well-defined but amorphous metal–organic thin films, such as our Mg-, Ca-, Sr-, and Ba-based 3,5-PDC films, which can then be crystallized into water-containing structures through a post-deposition humidity treatment. All together, the new metal–organic structures realized in this study through ALD/MLD comprise a majority of the (anhydrous and water-containing) members of the s-block metal 3,5-pyridinedicarboxylate family.     

纳米结构ZnO在TiO_2薄膜上的电化学沉积及其表征

在三电极体系中,以硝酸锌水溶液作为电解液,采用阴极还原电沉积法成功实现了一维纳米结构ZnO阵列在TiO2纳米粒子/ITO导电玻璃薄膜基底上的沉积,并通过XRD、SEM、EDS和PL光谱等方法对样品进行了表征.重点研究了薄膜基底、电解液浓度、沉积时间、六次亚甲基四胺(HMT)的引入对ZnO沉积及其发光性质的影响.结果显示:与ITO玻璃基底相比,ZnO更易于在TiO2纳米粒子薄膜上实现电化学沉积.ZnO属于六方晶系的铅锌矿结构,并且沿着c-轴方向表现出明显的择优化生长,以形成垂直于基底的ZnO纳米棒阵列.延长沉积时间、增加电解液浓度和引入一定量的HMT等均对ZnO的生长有促进作用,进而使其纳米棒的结晶度和取向程度提高,进而解释了所得的薄膜分别约在375和520nm处表现出ZnO的强而窄的带边紫外光发射峰和弱而宽的表面态绿光发射带.     

Au/ZnO/TiO_2复合薄膜的制备及光电转换性质

以含有Au和ZnO纳米颗粒的氢氧化钛溶胶作为成膜液,通过浸渍-提拉及灼烧处理在导电玻璃表面制备Au/ZnO/TiO2复合薄膜.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)等方法对所得产物进行表征.结果表明,Au和ZnO纳米颗粒均匀地分布在多孔TiO2薄膜上,通过TiO2、ZnO和Au三组分的协同效应促进了光吸收和电荷分离,使Au/ZnO/TiO2复合薄膜具有较好的光电转换性质,可用作太阳能电池材料.     

Floating ZnO QDs-Modified TiO2/LLDPE Hybrid Polymer Film for the Effective Photodegradation of Tetracycline under Fluorescent Light Irradiation: Synthesis and Characterisation

In this work, mesoporous TiO₂-modified ZnO quantum dots (QDs) were immobilised on a linear low-density polyethylene (LLDPE) polymer using a solution casting method for the photodegradation of tetracycline (TC) antibiotics under fluorescent light irradiation. Various spectroscopic and microscopic techniques were used to investigate the physicochemical properties of the floating hybrid polymer film catalyst (8%-ZT@LLDPE). The highest removal (89.5%) of TC (40 mg/L) was achieved within 90 min at pH 9 due to enhanced water uptake by the LDDPE film and the surface roughness of the hybrid film. The formation of heterojunctions increased the separation of photogenerated electron-hole pairs. The QDs size-dependent quantum confinement effect leads to the displacement of the conduction band potential of ZnO QDs to more negative energy values than TiO₂. The displacement generates more reactive species with higher oxidation ability. The highly stable film photocatalyst can be separated easily and can be repeatedly used up to 8 cycles without significant loss in the photocatalytic ability. The scavenging test indicates that the main species responsible for the photodegradation was O₂^●−. The proposed photodegradation mechanism of TC was demonstrated in further detail based on the intermediates detected by LC-time-of-flight/mass spectrometry (LC/TOF-MS).     

Superior Photostability and Photocatalytic Activity of ZnO Nanoparticles Coated with Ultrathin TiO2 Layers through Atomic‐Layer Deposition

Atomic‐layer deposition (ALD) is a thin‐film growth technology that allows for conformal growth of thin films with atomic‐level control over their thickness. Although ALD is successful in the semiconductor manufacturing industry, its feasibility for nanoparticle coating has been less explored. Herein, the ALD coating of TiO₂ layers on ZnO nanoparticles by employing a specialized rotary reactor is demonstrated. The photocatalytic activity and photostability of ZnO nanoparticles coated with TiO₂ layers by ALD and chemical methods were examined by the photodegradation of Rhodamine B dye under UV irradiation. Even though the photocatalytic activity of the presynthesized ZnO nanoparticles is higher than that of commercial P25 TiO₂ nanoparticles, their activity tends to decline due to severe photocorrosion. The chemically synthesized TiO₂ coating layer on ZnO resulted in severely declined photoactivity despite the improved photostability. However, ultrathin and conformal ALD TiO₂ coatings (≈0.75–1.5 nm) on ZnO improved its photostability without degradation of photocatalytic activity. Surprisingly, the photostability is comparable to that of pure TiO₂, and the photocatalytic activity to that of pure ZnO.     

Enhanced Electrochemical Performance of Supercapacitors via Atomic Layer Deposition of ZnO on the Activated Carbon Electrode Material

Fabricating electrical double-layer capacitors (EDLCs) with high energy density for various applications has been of great interest in recent years. However, activated carbon (AC) electrodes are restricted to a lower operating voltage because they suffer from instability above a threshold potential window. Thus, they are limited in their energy storage. The deposition of inorganic compounds’ atomic layer deposition (ALD) aiming to enhance cycling performance of supercapacitors and battery electrodes can be applied to the AC electrode materials. Here, we report on the investigation of zinc oxide (ZnO) coating strategy in terms of different pulse times of precursors, ALD cycles, and deposition temperatures to ensure high electrical conductivity and capacitance retention without blocking the micropores of the AC electrode. Crystalline ZnO phase with its optimal forming condition is obtained preferably using a longer precursor pulse time. Supercapacitors comprising AC electrodes coated with 20 cycles of ALD ZnO at 70 °C and operated in TEABF₄/acetonitrile organic electrolyte show a specific capacitance of 23.13 F g⁻¹ at 5 mA cm⁻² and enhanced capacitance retention at 3.2 V, which well exceeds the normal working voltage of a commercial EDLC product (2.7 V). This work delivers an additional feasible approach of using ZnO ALD modification of AC materials, enhancing and promoting stable EDLC cells under high working voltages.     

Atomic and Molecular Layer Deposition as Surface Engineering Techniques for Emerging Alkali Metal Rechargeable Batteries

Alkali metals (lithium, sodium, and potassium) are promising as anodes in emerging rechargeable batteries, ascribed to their high capacity or abundance. Two commonly experienced issues, however, have hindered them from commercialization: the dendritic growth of alkali metals during plating and the formation of solid electrolyte interphase due to contact with liquid electrolytes. Many technical strategies have been developed for addressing these two issues in the past decades. Among them, atomic and molecular layer deposition (ALD and MLD) have been drawing more and more efforts, owing to a series of their unique capabilities. ALD and MLD enable a variety of inorganic, organic, and even inorganic-organic hybrid materials, featuring accurate nanoscale controllability, low process temperature, and extremely uniform and conformal coverage. Consequently, ALD and MLD have paved a novel route for tackling the issues of alkali metal anodes. In this review, we have made a thorough survey on surface coatings via ALD and MLD, and comparatively analyzed their effects on improving the safety and stability of alkali metal anodes. We expect that this article will help boost more efforts in exploring advanced surface coatings via ALD and MLD to successfully mitigate the issues of alkali metal anodes.     

Three-Dimensional Pinecone-like Binder-Free Pt–TiO2 Nanorods on Ti Mesh Structures: Synthesis,Characterization and Electroactivity towards Ethanol Oxidation

We report here the synthesis of binderless and template-less three-dimensional (3D) pinecone-shaped Pt/TiO₂/Ti mesh structure. The TiO₂ hydrothermally synthesized onto Ti mesh is composed of a mixture of flower-like nanorods and vertically aligned bar-shaped structures, whereas Pt film grown by pulsed laser deposition displays a smooth surface. XRD analyses reveal an average crystallite size of 41.4 nm and 68.5 nm of the TiO₂ nanorods and Pt, respectively. In H₂SO₄ solution, the platinum oxide formation at the Pt/TiO₂/Ti mesh electrode is 180 mV more negative than that at the Pt/Ti mesh electrode, indicating that TiO₂ provides oxygeneous species at lower potentials, which will facilitate the removal of CO-like intermediates and accelerate an ethanol oxidation reaction (EOR). Indeed, the Pt/TiO₂/Ti mesh catalyst exhibits current activity of 1.19 mA towards an EOR at a remarkably superior rate of 4.4 times that of the Pt/Ti mesh electrode (0.27 mA). Moreover, the presence of TiO₂ as a support to Pt delivers a steady-state current of 2.1 mA, with an increment in durability of 6.6 times compared to Pt/Ti mesh (0.32 mA). Pt is chosen here as a benchmark catalyst and we believe that with catalysts that perform better than Pt, such 3D pinecone structures can be useful for a variety of catalytic or photoelectrochemical reactions.     

Synthesis of ZnO and TiO2 nanoparticles

We report on the synthesis of ZnO and TiO₂ nanoparticles by solution-phase methods, with a particular focus on the influence of experimental parameters on the kinetics of nucleation and coarsening. The nucleation rate of ZnO from the reaction between ZnCl₂ and NaOH in ethanol was found to increase with increasing precursor concentration, while the coarsening rate is independent of precursor concentration up to a threshold concentration. The nucleation rate of ZnO from Zn(OOC-CH₃)₂ and NaOH in n-alkanols was found to decrease with decreasing chain length, which is explained by the increase of the dielectric constant of the solvent. Due to the larger solubility of ZnO, nucleation is significantly slower than that observed in the case of TiO₂. TiO₂ nanoparticles coarsen according to the Lifshitz-Slyozov-Wagner model for Ostwald ripening. We also show that using amorphous titania as a base material, pure anatase and brookite nanoparticles can be synthesized.     

ZnO和TiO2粒子的光催化活性及其失活与再生

 利用XRD，TEM，BET和UV－Vis等测试技术对商品的ZnO及TiO2和纳米ZnO及TiO2粒子进行了表征．无论是商品的还是纳米的，在光催化氧化降解气相n－C7H16和SO2及液相苯酚的反应中，TiO2均表现出比ZnO高的光催化活性，并从光腐蚀性和表面电荷两方面分析了其原因．在光催化氧化降解n－C7H16的反应中，ZnO粒子易失活，而TiO2粒子不易失活．但是，在光催化氧化降解SO2的反应中，ZnO和TiO2粒子均易失活．SPS和XPS测试结果表明，光催化剂表面的导电类型由反应前的n型变成了失活后的p型．这主要是由于反应产物发生吸附所致．失活后的光催化剂可以通过浸洗和干燥再生．     

Melt‐compounded nanocomposites of titanium dioxide atomic‐layer‐deposition‐coated polyamide and polystyrene powders

Polyamide and polystyrene particles were coated with titanium dioxide films by atomic layer deposition (ALD) and then melt‐compounded to form polymer nanocomposites. The rheological properties of the ALD‐created nanocomposite materials were characterized with a melt flow indexer, a melt flow spiral mould, and a rotational rheometer. The results suggest that the melt flow properties of polyamide nanocomposites were markedly better than those of pure polyamide and polystyrene nanocomposites. Such behavior was shown to originate in an uncontrollable decrease in the polyamide molecular weight, likely affected by a high thin‐film impurity content, as shown in gel permeation chromatography (GPC) and scanning electron microscope (SEM) equipped with an energy‐dispersive spectrometer. Transmission electron microscope image showed that a thin film grew on both studied polymer particles, and that subsequent melt‐compounding was successful, producing well dispersed ribbon‐like titanium dioxide with the titanium dioxide filler content ranging from 0.06 to 1.12 wt%. Even though we used nanofillers with a high aspect ratio, they had only a minor effect on the tensile and flexural properties of the polystyrene nanocomposites. The mechanical behavior of polyamide nanocomposites was more complex because of the molecular weight degradation. Our approach here to form polymeric nanocomposites is one way to tailor ceramic nanofillers and form homogenous polymer nanocomposites with minimal work‐related risks in handling powder form nanofillers. However, further research is needed to gauge the commercial potential of ALD‐created nanocomposite materials. Copyright © 2011 John Wiley & Sons, Ltd.     

用分子轨道理论研究NO气体在TiO2表面吸附

根据一氧化氮(NO)气体在二氧化钛(TiO)表面吸附和脱附的实验结果,揭示了气体脱附量的变化规律．利用MOPAC和GAUSSIAN分子轨道理论计算了在TiO2(110)表面上吸附NO分子的原子簇模型,电荷分布以及原子簇的能级,推断了NO在TiO(110)表面吸附的稳定性．     

Co掺杂对TiO2光催化剂结构与性能的影响

采用溶胶-凝胶法制备了Co掺杂的TiO2粉末, 利用透射电子显微镜、X射线光电子能谱、紫外可见光谱和X射线衍射技术对粉末进行了表征, 并利用环形光催化反应器对其光催化活性进行了测试. 结果表明, 随焙烧温度的增加, Co/TiO2粉末的晶粒尺寸逐渐增大, 升至873 K时, 钴元素以CoTiO3形式从TiO2中析出, 同时TiO2由锐钛矿型向金红石型发生转变, 相转变过程中晶格常数a和c以及晶胞体积发生收缩. 掺杂钴以后, 粉末的光谱吸收范围被拓展至可见光, 但是其光催化活性却明显降低.     

Atomic Layer Deposition of the Metal Pyrites FeS2, CoS2, and NiS2

Atomic layer deposition (ALD) of the pyrite‐type metal disulfides FeS₂, CoS₂, and NiS₂ is reported for the first time. The deposition processes use iron, cobalt, and nickel amidinate compounds as the corresponding metal precursors and the H₂S plasma as the sulfur source. All the processes are demonstrated to follow ideal self‐limiting ALD growth behavior to produce fairly pure, smooth, well‐crystallized, stoichiometric pyrite FeS₂, CoS₂, and NiS₂ films. By these processes, the FeS₂, CoS₂, and NiS₂ films can also be uniformly and conformally deposited into deep narrow trenches with aspect ratios as high as 10:1, which thereby highlights the broad and promising applicability of these ALD processes for conformal film coatings on complex high‐aspect‐ratio 3D architectures in general.     

用TiO2，ZnO及Fe2O3纳米粒子光催化氧化庚烷的反应

 制备了三种n－型半导体氧化物TiO2，ZnO和Fe2O3纳米粒子，用X射线衍射和N2吸附技术分别对它们的结构及比表面积进行了表征．考察了三种氧化物粒子对庚烷的气相光催化氧化反应的催化活性．研究表明，对于同种催化剂，随着焙烧温度的升高，催化剂的粒径增大，比表 面积减小，光催化活性下降．三种催化剂纳米粒子的光催化活性顺序为TiO2（锐钛矿）＞ZnO＞Fe2O3，金红石型TiO2粒子的催化活性低于ZnO粒子．结合能带理论探讨了三种催化剂光催化活性差异的原因．     

纳米TiO2识别色氨酸对映体的研究

以纳米TiO2为基底,L-色氨酸(L-Trp)为模板分子,采用溶胶凝胶法合成L-Trp印迹的纳米TiO2。采用扫描电镜和红外光谱对印迹纳米TiO2和非印迹纳米TiO2进行表征,表明模板分子L-Trp成功地印迹到纳米TiO2中。采用1%的氨水溶液去除印迹的纳米TiO2中的模板分子L-Trp,纳米TiO2上留下与L-Trp相匹配的空穴。采用荧光分光光度法研究了具有L-Trp铸型的纳米TiO2对L-Trp和D-色氨酸(D-Trp)的分离效果。实验表明,模板分子L-Trp与钛前驱体的最佳投料摩尔比为1∶0.2,富集溶液pH值为6.0时,印迹纳米TiO2对L-Trp具有优异的选择吸附性,其分离选择系数为2.42,可实现对色氨酸对映体的识别。     

CO2 Sorbents Based on Spherical Carbon and Photoactive Metal Oxides: Insight into Adsorption Capacity,Selectivity and Regenerability

This work aimed to obtain hybrid composites based on photoactive metal oxide and carbon having adsorption properties. The materials, composed of titanium dioxide or zinc oxide and spherical carbon, were obtained from resorcinol-formaldehyde resin, treated in a solvothermal reactor heated with microwaves and then subjected to carbonization, were received. The functional groups of pure carbon spheres (unsaturated stretching C=C, stretching C−OH and C−H bending vibrations), CS/ZnO and CS/TiO₂ samples were determined by FT-IR analysis. The characteristic bands for ZnO and TiO₂ were observed below 1000 cm⁻¹. The thermal oxidative properties are similar for TiO₂- and ZnO-modified carbon spheres. We have observed that the increased carbon sphere content in nanocomposites results in starting the decomposition process at a lower temperature, therefore, nanocomposites have a broader combustion temperature range. The effect of the oxides’ addition to carbon spheres on their adsorption properties was evaluated in detail by examining CO₂ adsorption from the gas phase. The selectivity of CO₂ over N₂ at a temperature of 25 °C and pressure of 1 bar (a novelty in testing CS-based sorbents) calculated for 3.00 CS/TiO₂ and 4.00 CS/ZnO was 15.09 and 16.95, respectively. These nanocomposites exhibit excellent cyclic stability checked over 10 consecutive adsorption–desorption cycles.     

微量铂掺杂对TiO2粉末结构和性能的影响

采用溶胶-凝胶法制备了铂掺杂的TiO2粉末, 利用透射电子显微镜、X射线光电子能谱、紫外可见光谱和X射线衍射技术对粉末的结构和光吸收性能进行了表征. 结果表明, Pt/TiO2粉末主要含有Ti, O, Pt和C元素, 其中Pt主要以0价态存在. 573～873 K焙烧的Pt/TiO2粉末中, TiO2是锐钛矿结构, 973 K焙烧时, 有6.3%的TiO2转变为金红石结构. Pt/TiO2粉末的晶粒尺寸小, 铂和锐钛矿结构TiO2粒子都是纳米颗粒. 随焙烧温度升高, 粉末中TiO2的晶粒尺寸逐渐增大, 晶格常数a和c发生各向异性的变化, 单胞体积在相变时发生收缩. 与TiO2粉末相比, Pt/TiO2粉末中两种结构TiO2的晶格常数和晶胞体积基本上都增大了, 光谱吸收范围被明显拓展至可见光, 实现了可见光催化的基础.