Room temperature solution synthesis of monodispersed single-crystalline ZnO nanorods and derived hierarchical nanostructures

In this work, we report a room temperature wet-chemical approach to synthesize highly regulated, monodispersed ZnO nanorods and derived hierarchical nanostructures. In particular, ZnO has been prepared into single-crystalline conical or prismatic nanorods, and various hierarchical structures such as hexagonally branched, reversed umbrella-type, and cactus-like ZnO nanostructures comprising individual c-oriented nanorods. Depending on the synthetic conditions used, the diameter of nanorods can be controlled with a size down to 10-30 nm, while the aspect ratio can be controlled up to 50-100. Various preparative parameters, such as initial reactant concentrations, solvents, ligands, surfactants, precursor salts, and reaction time, have been systematically examined. Due to slow reactions at room temperature, excellent crystallinity and high morphological yield (100% in most cases) have been achieved via tuning the synthetic parameters. Our photoluminescence and UV measurements also confirm the attained crystal perfection and size uniformity.     

钼酸镍铵的环保合成及其对二苯并噻吩的加氢脱硫反应性能

日益苛刻的环保法规对柴油中的硫含量提出了更高的要求,而非负载型加氢脱硫催化剂具有较高的催化反应活性,其研发及应用不仅具有理论研究价值,同时还具有较高的社会经济性.非负载型加氢脱硫催化剂中的典型代表即为Nebula催化剂,该催化剂可以在不更改原有装置的前提下,使得原始设计生产硫含量为500 μg/g的装置得以生产硫含量不高于10 μg/g的超低硫柴油.已有的文献报道中,非负载型加氢脱硫催化剂前驱体主要是通过水热反应法及化学沉淀法制备而成.这两种方法以水为溶剂,溶剂水的量远远高于反应原料的添加量,因此,这两种方法不仅产生大量含有重金属离子的污水,同时能量及沉淀剂的消耗较高,最终导致产品的收率较低,原子经济性较差.为了更加环保、可持续地生产非负载型加氢脱硫催化剂前驱体,本文报道了一种以加水辅助研磨、固相反应法合成非负载型加氢脱硫催化剂前驱体钼酸镍铵((NH4)HNi2(OH)2(MoO4)2),并且揭示了其形成机理.相较于传统的水热反应法和化学沉淀法,我们提出的固相反应法使合成过程明显简化,主要步骤包括原料的物理混合、添加少量水进行研磨及加热.通过X射线衍射、红外光谱及拉曼光谱研究了钼酸镍铵的形成机理.结果表明,在钼酸镍铵的形成过程中,钼酸铵分子中的一个Mo原子被Ni原子取代形成了一种介稳态中间物种((NH4)4(NiH6Mo6O24)· 5H2O),而在120℃下处理不仅可以移除加入的少量水,而且促进了钼酸镍铵的形成.揭示钼酸镍铵的形成机理对于后续的研究具有重要的意义,因为可以更有针对性的调节、优化制备方法或者引入其它溶剂,从而制备具有某些特定性质的钼酸镍铵类物质.通过这种固相反应法制备的钼酸镍铵,具有与化学沉淀法制备的样品几乎相同的物理化学性质,包括物相、热稳定性能、孔结构性质等.不添加任何组分,将钼酸镍铵前驱体直接压片,并在固定床高压微型反应装置中进行原位硫化,制备了硫化态非负载型加氢脱硫催化剂.以二苯并噻吩为模型化合物,考察了通过化学沉淀法和固相反应法制备的两种钼酸镍铵前驱体的加氢脱硫反应活性.虽然这两种制备方法有所区别,但是硫化态非负载型加氢脱硫催化剂中活性组分二硫化钼(MoS2)纳米颗粒具有相似的堆积层数和片层长度,同时对二苯并噻吩的转化频率(TOF)相近,分别为28×10-4s(固相反应法)和26×10-4 s(化学沉淀法).因此,与传统的水热反应法或化学沉淀法相比,该法具有简化合成过程、降低水及能源的消耗及提高产品的收率等明显的优势.对于大规模地合成钼酸镍铵并用于工业加氢脱硫反应装置中具有重要的意义.与此同时,这种少量水辅助研磨固相反应法可以扩展到钼酸镍铵同晶物质的合成,例如钼酸钴(锌、铜)铵.     

Room temperature synthesis of HgTe nanocrystals

We report a new method to synthesize monodisperse zinc blende HgTe nanocrystals at room temperature in noncoordinating solvent-octadecene. Thiol was needed to control the reaction at a suitable nucleation and growth speed. In the early stage of the reaction, HgTe nanocrystals formed aggregates, and then the aggregates were dispersed and individual dot-shaped nanocrystals were formed with stronger photoluminescence emitting. UV-vis, photoluminescence, and TEM have been used to study the properties of as-prepared HgTe nanocrystals.     

Room temperature synthesis of upconversion fluorescent nanocrystals

Synthesis of nanocrystals that exhibit strong upconversion (UC) luminescence upon infrared excitation has been challenging due to the stringent control needed over experimental variables. Herein, we report a method to synthesize nanocrystals demonstrating high UC at room temperature in aqueous solution on graphene.     

Room temperature synthesis of surface-functionalised boron nanoparticles

Capped boron nanoparticles have been synthesized at room temperature by a simple route that does not involve the use of flammable boranes.     

Spectrophotometric determination of phenylhydrazine with ammonium molybdate

Summary The determination of phenyl hydrazine is done by reaction with ammonium molybdate; the pink colour procedud is extracted inton-butanol. 100–1300g of phenyl hydrazine can be determined at 510 nm. The effect of time, temperature, ammonium molybdate concentration and interferences has been studied.

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Zusammenfassung Die Bestimmung von Phenylhydrazin erfolgt auf der Grundlage seiner Reaktion mit Ammoniummolybdat. Die rosa Färbung wird mitn-Butanol extrahiert. 0,1–1,3 mg Phenylhydrazin können bei 510 nm gemessen werden. Der Einfluß der Reaktionszeit, der Temperatur, der Reagenskonzentration sowie auftretende Störungen wurden untersucht.

     

三草酸合铁(Ⅲ)酸钾的室温固相合成与晶体结构表征

以草酸钾和氯化铁为原料,通过室温固固反应合成了三草酸合铁(Ⅲ)酸钾配合物,用ICP、元素分析、X-射线单晶衍射、X-射线粉末衍射、红外光谱及热分析等方法对其组成和结构进行了表征.实验结果表明:三草酸合铁(Ⅲ)酸钾K3[Fe(C2O4)3]·3H2O的晶体结构属于单斜晶系,P2(1)/n空间群,晶胞参数a=0.774 52(4) nm,b=1.990 39(10) nm,c=1.034 31(5) nm,β=107.704(2)°,Z=4,Dc=2.148 g/cm~3.草酸根中的O原子与Fe原子形成了配位数为6的变形八面体配合物,在N2气氛中的热分解过程分4步,最后的残余物为FeO和K_2CO_3.     

Room temperature synthesis of Ti-SBA-15 from silatrane and titanium-glycolate and its catalytic performance towards styrene epoxidation

A novel room temperature sol–gel synthesis of Ti-SBA-15 is described using moisture stable silatrane and titanium glycolate precursors, and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer (EO₂₀PO₇₀EO₂₀) as the structure directing agent. Catalyst performance was optimized by systematically investigating the influence of acidity, reaction time and temperature, and titanium loading. Small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) showed well-ordered 2D mesoporous hexagonal structures, while N₂ adsorption/desorption measurements yielded high surface areas (up to 670 m²/g), with large pore diameters (5.79 nm) and volumes (0.83 cm³/g). Diffuse reflectance UV–visible spectroscopy (DRUV) was found that tetravalent titanium as Ti⁴⁺O₄ tetrahedra were incorporated in the framework through displacement of Si⁴⁺O₄ after calcination (550°C/6 h) to loadings of 7 mol% Ti without perturbation of the ordered mesoporous structure, or decoration by extra-framework anatase containing Ti⁴⁺O₆ octahedra. The catalytic activity and selectivity of styrene epoxidation using hydrogen peroxide (H₂O₂) showed that the conversion of styrene increases significantly at higher titanium contents. The only products of this reaction were styrene oxide and benzaldehyde, with selectivity of 34.2 and 65.8%, respectively, at a styrene conversion of 25.8% over the 7 mol% Ti-SBA-15 catalyst. Beyond this titanium loading, anatase is deposited on the framework and catalytic activity degrades. The performance of the new catalyst is also shown to be superior to conventional materials produced by incipient wetness impregnation where Ti resides on the surface of SBA-15, giving a styrene conversion of 11.9% under identical reaction conditions.     

Room temperature ionic liquids based on small aliphatic ammonium cations and asymmetric amide anions

The asymmetric amide anion (CF3SO2-N(-)-COCF3) has excellent abilities to lower both the melting points and viscosities of room temperature ionic liquids (RTILs) combining with small aliphatic ammonium cations that have not yet been reported to form RTILs.     

钼酸铵分光光度法测定绿茶中的茶多酚

采用钼酸铵分光光度法测定茶叶中的茶多酚含量。它是基于茶多酚在酸性条件下能与钼酸铵反应生成黄色钼酸酯,此物质在341nm处有最大吸收,用分光光度法测其吸光度,从而间接测定茶多酚含量。方法的线性范围为4×10-6～36×10-5g mL,ε=2.1×105L mol·cm,RSD=1 3%(茶多酚含量8×10-6g mL,n=11)。测定结果与标准法基本一致。     

Room temperature facile synthesis of quinoxalines catalyzed by amidosulfonic acid

Amidosulfonic acid NH₂–SO₃H catalyzed direct condensations of o‐phenylenediamines with α‐diketones at room temperature in organic solvents to afford quinoxalines in excellent yields. The amidosulfonic acid as a solid acid catalyst in this preparation was efficient and recoverable.     

Room temperature solution synthesis of alkyl-capped tetrahedral shaped silicon nanocrystals

We report the room temperature solution synthesis of alkyl protected silicon nanocrystals. The nanocrystals are of unusually uniform tetrahedral morphology and of a limited size distribution. The nanocrystals were characterized by transmission and scanning electron microscopy as well as atomic force microscopy.     

Use of ammonium molybdate in the colorimetric assay of cephalosporins

A colorimetric method for the determination of five cephalosporins (cefoxitin sodium, cefotaxime sodium, cephapirin sodium, cephalothin sodium and cephaloridine), based on the blue colour formed by reaction of the cephalosporins with ammonium molybdate, is described. The effects of reagent concentration and reaction conditions are discussed. The proposed method has been applied to the analysis of cephalosporin injections, the results of which are in good agreement with those obtained by the official method of the British Pharmacopoeia.     

Controllable synthesis and visible-light-responsive photocatalytic activity of Bi2WO6 fluffy microsphere with hierarchical architecture

Bismuth tungstate (Bi(2)WO(6)) has attracted great research interest as an important visible-light-responsive photocatalyst. In this paper, we report a facile hydrothermal route for the shape-controlled synthesis of micro/nanostructured Bi(2)WO(6), without adding surfactants or templates. The results show that various morphologies of Bi(2)WO(6) including coralloid spherical particles, packed nanosheets, fluffy microspheres, and plates can be obtained by adjusting the pH values of the precursors. The as-prepared porous fluffy microspheres with a hierarchical architecture synthesized at pH 8 exhibit the highest photocatalytic activity for the degradation of Rhodamine (RhB) under visible light irradiation. The photodegradation efficiency reaches as high as 99% within 20 min irradiation. This enhanced photocatalytic activity can be attributed to the unique porous structure and high BET surface area of fluffy microspheres with hierarchical architecture.     

Finetuning hierarchical energy material microstructure via high temperature material synthesis route

Hierarchical energy materials such as graphite are a backbone of various scientifically and commercially important emerging technologies including high-energy density energy storage systems with fast charging capability, multifunctional catalyst systems, selective membrane separation systems, and next-generation nuclear material systems. Consequently, it is extremely crucial to develop an efficient and cost-effective route of bulk hierarchical material synthesis (e.g., carbonaceous materials with a well-controlled fraction of the graphitic content) to cater the extraordinary operational and energy material requirements in a very complex coupled thermophysicochemical environment. Here we present a fabrication of Polyacrylonitrile (PAN) derived carbon films and fibers (~with linear dimension ~100 nm) via electrospinning and spin coating methods ensued by a heat-treatment in the range of 1000–3000 °C under inert atmospheric conditions. Intriguingly, we observed at least a two orders of magnitude enhancement (~134%) in length of graphitic plane accompanied by 36% more graphitization when the carbonization temperature increased from 1000 °C to 3000 °C. Such significant enhancements were attributed to the differences in the fundamental nanomorphology of initial carbonaceous materials and their subsequent kinetic evolution as it was more favorable for underlying graphene layers in films to stack and bond to the adjacent ones without strong rotations as compared to fibers, which were further evident from fewer voids and cracks in the films. The covalent cross-links, substrate effect and physical entanglements of carbon domains in PAN-derived carbon films contributed to a higher graphitic length owing to more shear stress between the graphene layers, compared to fibers and undergoes an enormous transformation from turbostratic structures to ordered state along with nitrogen removing over high temperature heating. This morphology dependent graphitization was also investigated from computational approach and concluded in the similar thoughts. The outcomes from this systematic study can be beneficial to the carbon research community focusing in the morphology dependent applications, for instance catalysis, energy storage, sensors etc.     

Corrosion inhibition of ammonium molybdate for AA6061 alloy in NaCl solution and its synergistic effect with calcium gluconate

The corrosion inhibition of ammonium heltamolybdate (AH) and calcium gluconate (CG) for AA6061 alloy in 3% NaCl solution was investigated by the electrochemical measurements. It indicates that AH inhibits the corrosion of AA6061 alloy and acts as an anodic inhibitor. Maximum inhibition efficiency reaches 74.3% at the concentration of 1 × 10^?4 mol.l^?1 AH. The results of the electrochemical studies reveal AH is physically adsorbed on the AA6061 alloy surface and the adsorption follows Langmuir isotherm. The combination of AH and CG enhances the inhibition efficiency to 95.9%. The enhanced inhibition is attributed to the promotion of AH adsorption by CG. The mixture of AH and CG is a mixed‐type inhibitor and renders the corrosion potential to more positive values. Copyright © 2011 John Wiley & Sons, Ltd.     

Room temperature synthesis of coinage metal (Ag, Cu) chalcogenides

Coinage metal chalcogenides in their nanoregime have been synthesized in aqueous medium at room temperature by mixing the nanoparticles of silver or copper with selenium nanoparticles which are authenticated by UV-vis, XRD and TEM analyses.     

Room temperature synthesis of glycerol carbonate catalyzed by N-heterocyclic carbenes

N-Heterocyclic carbenes were used as efficient organocatalysts for the synthesis of glycerol carbonate from glycerol and dimethyl carbonate. The reaction takes place in a liquid mixture of reactants without solvent at room temperature. It provides glycerol carbonate in high yield using 2.6–4 mol % of catalyst in a reaction period of 20–30 min.