Synthesis of tungsten disulfide (WS2) nanoflakes for lithium ion battery application

A novel method (a rheological phase reaction) was used to synthesize WS₂ nanoflakes by adding oxalic acid as a reducing reagent. High resolution electron microscopy observations revealed that the as-prepared WS₂ nanoflakes had started to curve and that WS₂ nanotubes were partly formed. The lithium intercalation/deintercalation behavior of as-prepared WS₂ electrode was also investigated. It was found that the WS₂ nanoflake electrode exhibited higher specific capacity with very good cycling stability compared to WS₂ nanotube or nanoparticle electrodes. The reasons for the improved electrochemical performance of the nanoflake electrodes are also discussed.     

Selective hydrothermal synthesis of BiOBr microflowers and Bi2O3 shuttles with concave surfaces

Through controlling the amount of NaOH added, BiOBr and Bi₂O₃ with different shapes were hydrothermally synthesized in the reaction system of Bi(NO₃)₃-hexadecyl trimethyl ammonium bromide (CTAB)-NaOH. As 8 mmol of NaOH was added, BiOBr microflowers constructed of nanoflakes were synthesized. The thickness of these single-crystal nanoflakes was about 20 nm. In the similar condition, when the amount of NaOH added was 28 mmol, Bi₂O₃ shuttles with concave surfaces were obtained. The length of these shuttles was 100 μm and the diameter at the middle of these shuttles was 50 μm. The photocatalytic activity of as-prepared BiOBr microflowers was evaluated by the degradation of methyl orange (MO) under visible-light irradiation (λ>420 nm), which was up to 96% within 90 min.     

Direct synthesis of porous/hollow magnesium carbonate hydroxide spindly nanorods and their application in water treatment

Spindly Mg₅(CO₃)₄(OH)₂·4H₂O nanorods with porous and hollow nanostructures were synthesized in a water-in-oil reverse microemulsion system of cetyltrimethylammonium bromide (CTAB)/water/cyclohexane/n-pentanol. These nanorods were characterized by a number of physical techniques, including powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Comparison experiments showed that fundamental experimental parameters, such as the molar ratio of H₂O to CTAB and the concentration of reactants, were important in the morphological control of Mg₅(CO₃)₄(OH)₂·4H₂O nanostructures. The potential applications of the as-synthesized Mg₅(CO₃)₄(OH)₂·4H₂O nanorods in water treatment were also investigated.     

Single crystal WO3 nanoflakes as quartz crystal microbalance sensing layer for ultrafast detection of trace sarin simulant

Tungsten oxide (WO₃) nanoflakes were synthesized, and characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Thermogravimetry and X-ray photoelectron spectroscopy demonstrate the existence of strongly bound surface water molecules on the surface of tungsten oxide nanoflakes. WO₃ nanoflake functionalized quartz crystal microbalance sensors were fabricated, and firstly used for detection of trace sarin simulant, dimethyl methylphosphonate (DMMP). The sensors have better reproducibility and stability as well as much shorter response (30 s) and recovery time (73 s) than those functionalized by conventional hydrogen-bond acidic branched copolymers. The strongly bound surface water molecules on the surface of WO₃ nanoflakes are believed to play a key role in achieving such excellent DMMP sensing characteristics.     

Photocatalytic TiO2/glass nanoflake array films

A new approach for the fabrication of oriented TiO2/glass nanoflake arrays has been developed. The ceramic nanoflake array was formed on a glass substrate via a simple, low temperature, and one-step hydrothermally induced phase separation approach without using any templates or additives. The factors affecting the formation of ceramic nanoflakes were examined by various characterization techniques. The results showed that the leaching of the soluble phase from the glass surface through hydrothermal processes resulted in oriented uniform ceramic nanoflake arrays. Electron microscope observations revealed that the nanoflakes formed a continuous porous three-dimensional-network array with a large surface-to-volume ratio. In addition, an anatase TiO2 film was successfully coated onto the nanoflake array by the sol-gel method. The TiO2/glass nanoflake array exhibited high activity for the photocatalytic degradation of acetone and for photoinduced hydrophilic conversion. Such enhancements were attributed to the beneficial effects of the new continuous porous three-dimensional-interconnected nanoflake network and its surface geometrical nanostructure. The present approach provides a convenient route to modify a photocatalytic coating with a porous nano-architectured substrate. This opens extensive new opportunities in the design of semiconductor/ceramic nanostructural array thin films with unusual properties for future optical and electronic applications.     

花状结构Bi2WO6多孔微球: 组装及光催化性能

利用表面活性剂十六烷基三甲基溴化铵(CTAB)、十二烷基苯磺酸钠(SDBS)作为结构导向剂,在水热条件下合成了由纳米片组装而成的Bi2WO6花状多孔微球的新颖结构。探讨了反应时间、表面活性剂种类等因素对产物形貌、结构和性能的影响。在氙灯照射下,发现使用CTAB所得到的Bi2WO6比添加SDBS所得到的样品具有更高的催化罗丹明B降解的活性,原因是前者具有较大的比表面积和吸收阈值。同时提出了晶体可能的生长机理为各向异性生长特性和自组装-Ostwald熟化过程的结合。     

Alumina nanoflake‐coated graphene nanohybrid as a novel flame retardant filler for polypropylene

γ‐Al₂O₃ nanoflakes are decorated on the surface of graphene nanosheets by hydrothermal method. The chemical structures, composition, and morphology of the graphene nanohybrid are characterized. Alumina nanoflake‐coated graphene nanohybrid is incorporated into polypropylene (PP) matrix by master batch‐based melt mixing method. The effects of alumina‐graphene nanohybrid on the thermal stability and combustion behavior of PP are investigated. More char residue is left for PP composite containing alumina‐graphene nanohybrid. Peak heat release rate of pure PP is greatly decreased by this nanohybrid, corresponding to 30.6% reduction. Fire safety of PP is considerably enhanced. Flame retardant mechanisms are concluded based on the combustion results and char analysis. The barrier effect of graphene and catalytic charring actions of γ‐Al₂O₃ nanoflakes make the contribution to the enhanced flame retardant properties.     

Synthesis of Two‐Dimensional Transition‐Metal Phosphates with Highly Ordered Mesoporous Structures for Lithium‐Ion Battery Applications

Materials with ordered mesoporous structures have shown great potential in a wide range of applications. In particular, the combination of mesoporosity, low dimensionality, and well‐defined morphology in nanostructures may exhibit even more attractive features. However, the synthesis of such structures is still challenging in polar solvents. Herein, we report the preparation of ultrathin two‐dimensional (2D) nanoflakes of transition‐metal phosphates, including FePO₄, Mn₃(PO₄)₂, and Co₃(PO₄)₂, with highly ordered mesoporous structures in a nonpolar solvent. The as‐obtained nanoflakes with thicknesses of about 3.7 nm are constructed from a single layer of parallel‐packed pore channels. These uniquely ordered mesoporous 2D nanostructures may originate from the 2D assembly of cylindrical micelles formed by the amphiphilic precursors in the nonpolar solvent. The 2D mesoporous FePO₄ nanoflakes were used as the cathode for a lithium‐ion battery, which exhibits excellent stability and high rate capabilities.     

Simple synthesis of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoflakes using a low temperature sol–gel method suitable for photodegradation of dyes

In this work we describe and discuss the synthesis, and characterization of Co₃O₄ nanoflakes prepared by citric acid based sol–gel method using cobalt nitrate precursor. The average crystalline size of Co₃O₄ was estimated from the X-ray diffraction peaks of powders using Scherrer’s formula. The size of the particles deduced from TEM agrees with XRD based values. The FTIR confirms formation of Co₃O₄. The SEM micrographs show the nanoflake morphology. Here we report the lowest temperature sol–gel method of preparation of Co₃O₄ nanoflakes and its photocatalytic study for the degradation of dye pollutant methylorange.     

片状MoS2/MoS1.5Se0.5纳米复合材料的制备及其摩擦学性能研究

将钼粉与升华硫和硒粉的混合粉末按一定化学计量比混合,通过固相反应法成功制备出了均匀的片状纳米颗粒。分别使用X射线粉末衍射仪(XRD)、扫描电子显微镜(SEM)以及透射电子显微镜(TEM)对该纳米粉体进行结构表征和分析,发现该粉体为MoS2/MoS1.5Se0.5混合晶相,晶粒尺寸在300~600 nm,厚度约为5 nm的片状结构。将该MoS2/MoS1.5Se0.5纳米片作为润滑油添加剂添加到基础油中,使用UMT-2型摩擦磨损试验机对其摩擦学性能进行测试,并对摩擦机理进行了解释,结果表明MoS2/MoS1.5Se0.5纳米片作为润滑油添加剂具有良好的减摩抗磨性能。     

Preparation and self-assembly of copper nanoparticles via discharge of copper rod electrodes in a surfactant solution: a combination of physical and chemical processes

Cu nanoparticles with a mean diameter of 10-15 nm were prepared and self-assembled via discharge of bulk copper rods in a cetyltrimethylammonium bromide (CTAB)/ascorbic acid solution. Ascorbic acid was used as a protective agent to prevent the nascent Cu nanoparticles from oxidation in the solution; otherwise spindle-like Cu₂O/CuO structures, with a lateral dimension of 30-50 nm and length of up to 100 nm, were formed in pure deionized water. The surfactant CTAB had a critical influence on self-assembly of spherical Cu nanostructures (with diameter of 700 nm-1 μm). Such a low-temperature and non-vacuum method, exhibiting the characters of both physical and chemical processes, provides a versatile choice for economical preparation and assembly of various metal nanostructures.     

Synthesis of MnV2O6 nanoflakes via simple hydrothermal process

A single phase of monoclinic MnV₂O₆ nanoflakes was prepared by a hydrothermal process at 180°C for 18 h, using Mn (CH₃COO)₂·4H₂O and NH₄VO₃ as starting materials and using acetic acid to adjust the pH value of the reaction solution. The as-prepared samples were characterized by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). X-ray photoelectron spectrum (XPS) measurements further confirm the component of MnV₂O₆. Results indicated that the products consisted of a large quantity of compact accumulated nanoflakes, with average width of 0.85 μm, thickness of 100 nm and lengths up to 1.7 μm. __________ Translated from Journal of Inorganic Materials, 2007, 22(6): 1139–1141 [译自: 无机材料学报]     

2 D Manganese Vanadate Nanoflakes as High‐Performance Anode for Lithium‐Ion Batteries

Nanometer‐sized flakes of MnV₂O₆ were synthesized by a hydrothermal method. No surfactant, expensive metal salt, or alkali reagent was used. These MnV₂O₆ nanoflakes present a high discharge capacity of 768 mA h g^?1 at 200 mA g^?1, good rate capacity, and excellent cycling stability. Further investigation demonstrates that the nanoflake structure and the specific crystal structure make the prepared MnV₂O₆ a suitable material for lithium‐ion batteries.     

Synthesis of hydrophobic zinc borate nanoflakes and its effect on flame retardant properties of polyethylene

Zinc borate (2ZnO·3B₂O₃·3.5H₂O) has relatively high dehydration on-set temperature which property permits processing in a wide range of polymer system. But zinc borate particles are hardly dispersed in a polymer matrix so that they prevent their using in industry. To address this problem, we synthesized hydrophobic zinc borate (2ZnO·3B₂O₃·3.5H₂O) nanoflakes by employing solid-liquid reaction of zinc oxide (ZnO) and boric acid (H₃BO₃) in the presence of oleic acid. This method does not bring pollution. By conducting morphological and microscopic analyses, we found that this compound displayed nanoflake morphology with particle size of around 100-200 nm, thickness less than 100 nm and there were uniform mesopores with the diameter about 10 nm within the particles. Furthermore, our products had an effect on flame retardant of polyethylene, especially when the zinc borate was modified by oleic acid.     

Influence of surfactants on the morphologies of CaCO3 by carbonation route with compressed CO2

Three surfactants, sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and polyoxyethylene-80-sorbitan monooleate (Tween 80), were used to control the growth of CaCO₃ crystals by carbonation route using Ca(OH)₂ and compressed CO₂. The obtained CaCO₃ particles were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The effects of surfactants on the morphology of the particles were studied. It was demonstrated that Tween 80 and SDS have obvious effect on the morphology of CaCO₃ particles, while CTAB does not affect morphology considerably. The possible mechanism has been discussed on the basis of the binding of the surfactants to the certain face of the crystals.     

Bi2S3量子点敏化TiO2纳米阵列结构的制备及光电性能

利用水热法制备一维TiO₂纳米棒阵列,并采用化学浴沉积法(CBD)结合自组装技术在TiO₂纳米棒上敏化Bi₂S₃量子点,形成TiO₂/Bi₂S₃复合纳米棒阵列。系统研究了复合结构的表面形貌、晶体结构、光学及光电性能。结果表明:在修饰有三氨丙基三乙氧基硅烷自组装单分子膜(APTS-SAMs)的TiO₂纳米棒表面形成一层致密的Bi₂S₃量子点敏化层,这一技术的关键是含-NH₂末端的APTS-SAMs可有效促进Bi₂S₃的异相成核作用;Bi₂S₃的沉积时间对复合结构的光吸收及光电响应性能有决定性的影响,薄膜的光电流随着沉积时间呈先增加后减小的趋势,在沉积时间为20min时,光电流密度最大。这是因为随着沉积时间的增加,TiO₂纳米棒表面Bi₂S₃量子点密度增大,光吸收增加;而当沉积时间进一步延长时,Bi₂S₃在TiO₂纳米棒表面的大量负载而形成堆积和团聚,导致表面缺陷增多,光生电子复合几率增大,从而使光电流密度减小。     

Bi2S3量子点敏化TiO2纳米阵列结构的制备及光电性能研究

利用水热法制备一维TiO₂纳米棒阵列,并采用化学浴沉积法(CBD)结合自组装技术在TiO₂纳米棒上敏化Bi₂S₃量子点,形成TiO₂/Bi₂S₃复合纳米棒阵列.系统研究了复合结构的表面形貌、晶体结构、光学及光电性能.结果表明:在修饰有三氨丙基三乙氧基硅烷自组装单分子膜(APTS-SAMs)的TiO₂纳米棒表面形成一层致密的Bi₂S₃量子点敏化层,这一技术的关键是含-NH₂末端的APTS-SAMs可有效促进Bi₂S₃的异相成核作用;Bi₂S₃的沉积时间对复合结构的光吸收及光电响应性能有决定性的影响,薄膜的光电流随着沉积时间呈先增加后减小的趋势,在沉积时间为20 min时,光电流密度最大.这是因为随着沉积时间的增加,TiO₂纳米棒表面Bi₂S₃量子点密度增大,光吸收增加;而当沉积时间进一步延长时,Bi₂S₃在TiO₂纳米棒表面的大量负载而形成堆积和团聚,导致表面缺陷增多,光生电子复合几率增大,从而使光电流密度减小.     

Simple Hydrothermal Synthesis of Nickel Hydroxide Flower-Like Nanostructures

α-Ni(OH)₂ flower-like nanostructures were successfully synthesized through one-step hydrothermal method with nickel acetate tetrahydrate, ethylene-1,2-diamine (en), hexamethylenetetramine (HMT) and cetyltrimethylammonium bromide (CTAB) as morphology-directing agents. Optimum conditions to obtain high yield and pure phase α-Ni(OH)₂ were identified by varying experimental parameters such as: en, HMT and CTAB concentration and reaction temperature. The products were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared and thermogravimetric analysis. These results indicated that the α-nickel hydroxide contains water molecules and anions. The hierarchical NiO nanostructures were obtained by the as-synthesized α-Ni(OH)₂ nanostructures annealed at 300 °C for 4 h.     

Magnetic properties of Fe2P-type Tb6FeTe2, Tb6CoTe2, Tb6NiTe2 and Er6FeTe2 compounds

The magnetic ordering of the Fe₂P-type Tb₆FeTe₂, Tb₆CoTe₂ Tb₆NiTe₂ and Er₆FeTe₂ phases (space group P6¯2m) has been investigated through magnetization measurement and neutron powder diffraction. Tb₆FeTe₂, Tb₆CoTe₂ and Tb₆NiTe₂ demonstrate high-temperature ferromagnetic and low-temperature spin reorientation transitions, whereas Er₆FeTe₂ shows antiferromagnetic transition, only.The Tb₆FeTe₂ and Tb₆NiTe₂ phases show same high-temperature collinear ferromagnetic structure, whereas Tb₆FeTe₂ is the commensurate non-collinear ferromagnet and Tb₆NiTe₂ is the canted ferromagnetic cone with K₁=[0, 0, ±3/10] and K₂=[±2/9, ±2/9, 0] wave vectors at 2 K. The magnetic structure of Er₆FeTe₂ is a flat spiral with K₁=[0, 0, ±1/10] at 2 K. The magnetic entropy change for Tb₆NiTe₂ is ΔS_m=−4.86 J/kg K at 229 K for the field change Δμ₀H=0-5 T.In addition, novel Fe₂P-type Gd₆FeTe₂, Zr₆FeTe₂, Hf₆FeTe₂, Dy₆NiTe₂, Zr₆NiTe₂ and Hf₆NiTe₂ phases have been obtained.     

表面活性剂对染料敏化太阳能电池光电性能的提高

在硝酸/醋酸(HNO₃/HAc)的水溶液中分别加入十二烷基苯磺酸钠(DBS)、十六烷基三甲基溴化铵(CTAB)、吐温20等不同类型的表面活性剂来水解钛酸四正丁酯制得前驱体溶液,通过水热法制备纳晶TiO₂,并组装成染料敏化太阳能电池(DSSC)。通过XRD、SEM和UV-Vis对纳晶TiO₂薄膜进行表征,并对DSSC进行光电流-光电压(I-V)曲线的测试,研究了不同类型的表面活性剂和不同浓度的CTAB对DSSC光电性能的影响。结果表明：加入阳离子表面活性剂CTAB时提高了DSSC的光电性能,而加入阴离子表面活性剂DBS和非离子表面活性剂吐温20时,DSSC的光电性能反而降低。随着CTAB浓度的增加,电池的光电性能先提高后下降,当c_CTAB=0.08 mol·L^-1时,DSSC的光电转化效率最高为5.76%,比不添加表面活性剂制备的纳晶TiO₂所组装的DSSC的光电转化效率提高了约18%。