Alpha-CuV2O6 nanowires: hydrothermal synthesis and primary lithium battery application

We report on the synthesis, characterization, and electrochemical lithium intercalation of alpha-CuV2O6 nanowires, mesowires, and microrods that were prepared through a facile hydrothermal route. The diameters of the as-synthesized alpha-CuV2O6 nanowires, mesowires, and microrods were about 100 nm, 400 nm, and 1 microm, respectively. It was found that by simply controlling the hydrothermal reaction parameters, such as the reagent concentration and the dwell time, the transformation of microrods to nanowires was readily achieved via a "ripening-splitting" mechanism. Electrochemical measurements revealed that the as-prepared alpha-CuV2O6 nanowires and mesowires displayed high discharge capacities (447-514 mAh/g at 20 mA/g and 37 degrees C) and excellent high-rate capability. In particular, the alpha-CuV2O6 nanowires showed capacities much higher than those of alpha-CuV2O6 mesowires, microrods, and bulk particles. The mechanisms for the electrochemical lithium intercalation into the alpha-CuV2O6 nanowires were also discussed. From the Arrhenius plot of lithium intercalation into alpha-CuV2O6 nanowires, the activation energies were calculated to be 39.3 kJ/mol at 2.8 V (low lithium uptake) and 35.7 kJ/mol at 2.3 V (high lithium uptake). This result indicates that the alpha-CuV2O6 nanowires are promising cathode candidates for primary lithium batteries used in long-term implantable cardioverter defibrillators (ICD).     

Length-controlled synthesis of oriented single-crystal rutile TiO2 nanowire arrays

A free-standing, large area, oriented single-crystal rutile TiO(2) nanowire arrays with a controlled length in the range of 10-80 μm are prepared via a facile one-step synthesis. The growth process is studied systematically in an appropriate amount of H(2)O(2) and HCl solution under hydrothermal conditions. The length of the nanowires can be easily tuned by varying the experimental parameters, including reaction temperature and reaction time. High-resolution transmission electron microscopy demonstrated that the nanowires have single-crystal structure. Furthermore, the photoluminescence characteristics and photocatalytic properties of oriented single-crystal rutile TiO(2) nanowires was discussed in this paper, respectively. It is found that the increased reaction temperature is helpful to photocatalytic reactivity and photoluminescence properties.     

Synthesis, characterization, and electrochemical properties of Ag2V4O11 and AgVO3 1-D nano/microstructures

We report on the synthesis, characterization, and electrochemical properties of Ag(2)V(4)O(11) nanowires, alpha-AgVO(3) microrods, and beta-AgVO(3) nanowires that were synthesized through a simple and facile low-temperature hydrothermal approach without any template or catalyst. It was found that by simply controlling the hydrothermal reaction parameters such as pH and dwell time, the transformation of alpha-AgVO(3) microrods to beta-AgVO(3) nanowires were readily achieved through a "ripening-splitting model" mechanism. Electrochemical measurements revealed that the as-prepared Ag(2)V(4)O(11) nanowires, alpha-AgVO(3) microrods, and beta-AgVO(3) nanowires exhibited high discharge capacities and excellent high-rate dischargeability. In particular, the beta-AgVO(3) nanowires have much higher capacity above 3 V than that of alpha-AgVO(3) microrods, Ag(2)V(4)O(11) nanowires, and commercial Ag(2)V(4)O(11) bulk. The mechanisms for electrochemical lithium intercalation of the AgVO(3) nanostructures were also discussed. It is anticipated that the novel Ag(2)V(4)O(11) and AgVO(3) one-dimensional nano/microstructures are promising cathode candidates in the application of primary lithium ion batteries for implantable cardioverter defibrillators (ICDs).     

Reaction pathways of the Simmons-Smith reaction

The cyclopropanation reaction of an alkene with a metal carbenoid has been studied by means of the B3LYP hybrid density functional method. The cyclopropanation of ethylene with a lithium carbenoid or a zinc carbenoid [Simmons-Smith (SS) reagent] goes through two competing pathways, methylene transfer and carbometalation. Both processes are fast for the lithium carbenoid, while, for the zinc carbenoid, only the former is fast enough to be experimentally feasible. The reaction of an SS reagent (ClZnCH(2)Cl) with ethylene and an allyl alcohol in the presence of ZnCl(2) was also studied. The allyl alcohol reaction was modeled with an SS reagent/alkoxide complex (ClCH(2)ZnOCH(2)CH=CH(2)) formed from the SS reagent and allyl alcohol. Two modes of acceleration were found. The first involves the well-accepted mechanism of 1,2-chlorine migration, and the second involves a five-centered bond alternation. The latter was found to be more facile than the former and to operate equally well both with ethylene and with aggregates of SS reagent/alkoxide complexes. Calculations on the SS reaction with 2-cyclohexen-1-ol offer a reasonable model for the hydroxy-directed diastereoselective SS reaction, which has been used for a long time in organic synthesis.     

聚苯胺纳米线/SnO2复合光催化材料的光化学制备与性能

将具有确定形态的聚苯胺(PANI)纳米线作为复合单元, 直接分散在SnSO₄和H₂SO₄的混合溶液中, 通 过紫外光照射获得PANI纳米线/SnO₂纳米颗粒复合材料. 对复合材料的形态和成分进行了分析, 发现二者 相互交织在一起且部分颗粒直接生长在纳米线上. 以罗丹明B溶液为目标降解污染物研究了复合材料在低 功率紫外灯下的光催化活性. 结果表明, PANI纳米线可以明显增强SnO₂的光催化活性, 且增强效果与光照 复合时间呈规律性变化, 在最优复合时间下复合材料的光催化活性是纯SnO₂的近3倍. 通过对能级结构与光催化反应过程的测试分析, 认为Z型异质结的形成促进了光生电子-空穴的分离, 进而增强了材料的光催化活性.     

用模板法制备TiO2纳米线阵列膜及光催化性能的研究

用溶胶-凝胶技术在多孔阳极氧化铝模板的有序微孔内制备了高度取向的TiO2纳米线阵列膜光催化剂.用XRD,AFM和SEM等手段对样品进行了表征.结果表明,TiO2纳米线阵列膜晶型为锐钛矿,从AFM图像中可以看出TiO2纳米线线径分布均匀一致,取向性极好,直径与AAO模板的孔径大小一致.以其对吖啶橙的降解效果作为评价光催化活性的标准,与相同条件下制备的TiO2/玻璃膜相比,TiO2纳米线阵列膜具有很好的催化活性.     

Plasmon-enhanced photocatalytic properties of cu(2)o nanowire-au nanoparticle assemblies

Cu(2)O-Au nanocomposites (NCs) with tunable coverage of Au were prepared by a facile method of mixing gold nanoparticles (Au NPs) with copper(I) oxide nanowires (Cu(2)O NWs) in various ratios. These Cu(2)O-Au NCs display tunable optical properties, and their photocatalytic properties were dependent on the coverage density of Au NPs. The photocatalytic activity of Cu(2)O-Au NCs was examined by photodegradation of methylene blue. The presence of Au NPs enhanced the photodegradation efficiency of Cu(2)O NCs. The photocatalytic efficiency of Cu(2)O-Au NCs initially increased with the increasing coverage density of Au NPs and then decreased as the surface of Cu(2)O became densely covered by Au NPs. The enhanced photocatalytic efficiency was ascribed to enhanced light absorption (by the surface plasmon resonance) and the electron sink effect of the Au NPs.     

Bi3.25La0.75Ti3O12纳米线的可见光催化性能

研究了用一步水热法制备的掺镧钛酸铋(Bi_3.25La_0.75Ti₃O₁₂, BLT)纳米线的光学和可见光催化性能, 并对其晶体结构和微观结构用X射线衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段进行了表征. 结果表明, 制备的纳米线为纯相的Bi_3.25La_0.75Ti₃O₁₂, 平均直径约为25 nm. 室温光致发光谱(PL)显示BLT纳米线在433和565 nm附近有较强的发射峰, 分别对应激子发射和表面缺陷发光. 紫外-可见漫反射光谱(UV-Vis DRS)表明BLT样品的带隙能约为2.07 eV. 利用可见光(λ>420 nm)照射下的甲基橙降解实验评价了BLT样品的光催化性能. 结果表明, BLT的光催化活性比商用TiO₂催化剂P25、掺氮TiO₂和纯相钛酸铋(Bi₄Ti₃O₁₂, BIT)高得多. BLT光催化剂具有更高催化活性的原因是La³⁺离子掺杂拓展了BIT对可见光的吸收范围, 同时抑制了BIT的光生电子-空穴的复合.     

Mesoporous nickel oxide nanowires: hydrothermal synthesis, characterisation and applications for lithium-ion batteries and supercapacitors with superior performance

Mesoporous nickel oxide nanowires were synthesized by a hydrothermal reaction and subsequent annealing at 400?°C. The porous one-dimensional nanostructures were analysed by field-emission SEM, high-resolution TEM and N(2) adsorption/desorption isotherm measurements. When applied as the anode material in lithium-ion batteries, the as-prepared mesoporous nickel oxide nanowires demonstrated outstanding electrochemical performance with high lithium storage capacity, satisfactory cyclability and an excellent rate capacity. They also exhibited a high specific capacitance of 348?F?g(-1) as electrodes in supercapacitors.     

Constructing Co3O4 Nanowires on Carbon Fiber Film as a Lithiophilic Host for Stable Lithium Metal Anodes

Lithium metal has been considered as the most promising anode electrode for substantially improving the energy density of next‐generation energy storage devices. However, uncontrollable lithium dendrite growth, an unstable solid electrolyte interface (SEI), and infinite volume variation severely shortens its service lifespan and causes safety hazards, thus hindering the practical application of lithium metal electrodes. Here, carbon fiber film (CFF) modified by lithiophilic Co₃O₄ nanowires (denoted as Co₃O₄ Nws) was proposed as a matrix for prestoring lithium metal through a thermal infusion method. The homogeneous needle‐like Co₃O₄ nanowires can effectively promote molten lithium to infiltrate into the CFF skeleton. The post‐formed Co?Li₂O nanowires produced by the reaction of Co₃O₄ Nws and molten lithium can homogeneously distribute lithium ions flux and efficaciously increase the adsorption energy with lithium ions proved by density functional theory (DFT) calculation, boosting a uniform lithium deposition without dendrite growth. Therefore, the obtained composite anode (denoted as CFF/Co?Li₂O@Li) exhibits superior electrochemical performance with high stripping/plating capacities of 3 mAh cm^?2 and 5 mAh cm^?2 over long‐term cycles in symmetrical batteries. Moreover, in comparison with bare lithium anode, superior Coulombic efficiencies coupled with copper collector and full battery behaviors paired with LiFePO₄ cathode are achieved when CFF/Co?Li₂O@Li composite anode was employed.     

Degradation of rhodamine B photocatalyzed by Eu-doped CdS nanowires illuminated by visible radiation

CdS nanowires doped with different contents of Eu dopant were synthesized by solvothermal method. XRD, SEM, TEM and Raman analyses certified that the as-synthesized samples were hexagonal CdS uniform nanowires. The pure CdS nanowires were 1–3 ?μm long and 80 ?nm diameter with the 1st and 2nd order longitudinal phonon modes at 298 and 594 ?cm^?1. The 3% Eu-doped CdS wires were 800 ?nm–2.5 ?μm long and 75 ?nm diameter with the 1st and 2nd order longitudinal phonon modes at 296 and 593 ?cm^?1. CdS nanowires grew along the [001] direction due to the surface energy effect. The photocatalytic properties of CdS and Eu-doped CdS nanowires were investigated for the degradation of rhodamine B (RhB) illuminated by visible radiation. In this research, Eu dopant played the role in promoting the photocatalytic kinetics because Eu³⁺ ions act as an electron acceptor to promote charge separation and photocatalytic activity. Both ^●OH and ^●O₂^? were the main active radicals used to transform RhB molecules into CO₂, H₂O and other intermediates.     

Synthesis and Photocatalytic Activity of One-dimensional ZnO-Zn2SnO4 Mixed Oxide Nanowires

Mixed oxide photocatalysts, ZnO-Zn2SnO4 (ZnO-ZTO) nanowires with different sizes were prepared by a simple thermal evaporation method. The ZnO-ZTO nanowires were characterized with a scanning electron microscope, X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive spectrometer, and X-ray photoelectron spectrThe photocatalytic activity of the ZnO-ZTO mixed nanowires were studied by observing the photodegradation behaviors of methyl orange aqueous solution. The results suggest that the ZnO-ZTO mixed oxide nanowires have a higher photocatalytic activity than pure ZnO and Zn2SnO4 nanowires. The photocatalyst concentration in the solution distinctly affects the degradation rate, and our results show that higher photodegradation efficiency can be achieved with a smaller amount of ZnO-ZTO nanowire catalyst, as compared to the pure ZnO and ZTO nanowires. Moreover, the photocatalytic activity can also be enhanced by reducing the average diameter of the nanowires. The activity of pure ZnO and ZTO nanowires are also enhanced by physically mixing them. These results can be explained by the synergism between the two semiconductors.     

Mesoporous Nickel Oxide Nanowires: Hydrothermal Synthesis,Characterisation and Applications for Lithium‐Ion Batteries and Supercapacitors with Superior Performance

Mesoporous nickel oxide nanowires were synthesized by a hydrothermal reaction and subsequent annealing at 400 °C. The porous one‐dimensional nanostructures were analysed by field‐emission SEM, high‐resolution TEM and N₂ adsorption/desorption isotherm measurements. When applied as the anode material in lithium‐ion batteries, the as‐prepared mesoporous nickel oxide nanowires demonstrated outstanding electrochemical performance with high lithium storage capacity, satisfactory cyclability and an excellent rate capacity. They also exhibited a high specific capacitance of 348 F g^?1 as electrodes in supercapacitors.     

V2O5·xH2O-BiVO4纳米复合材料的可控合成和可见光响应的光催化性质

以单斜相V2O5·xH2O纳米线为前驱物,在温和条件下合成出V2O5·xH2O-BiVO4复合光催化剂.为理解产物的物相含量、形貌和光催化性质随合成时间延长而变化的情况,利用X射线衍射仪、场发射扫描电子显微镜、紫外-可见漫反射光谱仪以及光催化性质测试实验对三个典型的V2O5·xH2O-BiVO4样品(分别在反应6、12和24 h获得)进行了研究.分析结果表明:V2O5·xH2O-BiVO4纳米复合材料由V2O5·xH2O纳米线和BiVO4纳米晶组成,并且随合成反应时间的延长,产物中V2O5·xH2O纳米线的含量逐渐减少而BiVO4纳米晶的含量逐渐增加.光催化性质测试结果表明:V2O5·xH2O-BiVO4复合光催化剂在可见光(λ>400 nm)辐射下降解亚甲基蓝时表现出了提高的光催化效率,其中在反应12 h获得的V2O5·xH2O-BiVO4样品体现出最好的光催化活性,这可能是由于其适当的组分含量和特殊的微结构有利于半导体激发和染料激发两种光催化机理的协同作用.     

Synthesis of immobilized TiO2 nanowires by anodic oxidation and their gas phase photocatalytic properties

In this paper, anodic oxidation method was successfully employed to the direct growth of immobilized TiO₂ nanowires on titanium foil in ethylene glycol electrolyte solution contained HF and water. The morphologies of the TiO₂ nanowires could be tuned by changing the content of HF and water. The structures, morphologies and optical properties of TiO₂ nanowires were characterized by SEM, XRD, UV–vis and PL. It was found that the nanowires originally grew from the splitting of TiO₂ nanotubes. The gas phase photocatalytic activities were investigated by photodegradation of gaseous toluene under UV irradiation, and irregular TiO₂ nanowires showed the best photocatalytic ability.     

Growth of well-aligned gamma-MnO2 monocrystalline nanowires through a coordination-polymer-precursor route

A new coordination-polymer-precursor route has been developed to synthesize nanowires under hydrothermal conditions. In the present work, well-aligned gamma-MnO(2) nanowires, growing along the [0 0 2] axis, have successfully been prepared by selecting an appropriate coordination polymer [[Mn(SO(4))(4,4'-bpy)(H(2)O)(2)](n)] as precursor. In comparison with the experimental results from other coordination-polymer precursors, it is found that only [[Mn(SO(4))(4,4'-bpy)(H(2)O)(2)](n)] is appropriate for the formation of gamma-MnO(2) crystal lattices during the process of oxidization. The IR absorption spectra of as-obtained precipitates at different reaction intervals minutely describe the reaction process, due to the different coordination abilities of ligands in the coordination polymer. More evidence about the mechanism will be further explored in the future study. Further observations show the ordered alignment of nanowires' tops and such well-aligned nanowires provide more possible applications in lithium batteries.     

曙红-碳纳米管-CuO/CoO体系的光催化还原水制氢性能

构建了曙红-碳纳米管-CuO/CoO光催化体系(Eosin Y-MWNTs-CuO/CoO),并利用三乙醇胺作为牺牲剂考察了其可见光催化还原水制氢性能。结果表明,Eosin Y-MWNTs-CuO/CoO是一个高效的可见光催化剂,其光催化还原水析氢的速率可达403.1μmol.g-1.h-1。同时,还研究了溶液pH值、CuO/CoO负载量等因素对光催化体系活性的影响,并对Eosin Y-MWNTs-CuO/CoO的光催化机制进行了初步探讨。     

Titania nanowires as substrates for sensing and photocatalysis of common textile industry effluents

Sensing and photocatalysis of textile industry effluents such as dyes using mesoporous anatase titania nanowires are discussed here. Spectroscopic investigations show that the titania nanowires preferentially sense cationic (e.g. Methylene Blue, Rhodamine B) over anionic (e.g. Orange G, Remazol Brilliant Blue R) dyes. The adsorbed dye concentration on titania nanowires increased with increase in nanowire dimensions and dye solution pH. Electrochemical sensing directly corroborated spectroscopic findings. Electrochemical detection sensitivity for Methylene Blue increased by more than two times in magnitude with tripling of nanowire average length. Photodegradation of Methylene Blue using titania nanowires is also more efficient than the commercial P25-TiO₂ nanopowders. Keeping illumination protocol and observation times constant, the Methylene Blue concentration in solution decreased by only 50% in case of P25-TiO₂ nanoparticles compared to a 100% decrease for titania nanowires. Photodegradation was also found to be function of exposure times and dye solution pH. Excellent sensing ability and photocatalytic activity of the titania nanowires is attributed to increased effective reaction area of the controlled nanostructured morphology.     

MM3 force field prediction of the enantioselective preference in the asymmetric synthesis of a chiral 2-cyclohexen-1-ol using a chiral lithium amide reagent

Enantioselective preference in the asymmetric synthesis where cyclohexene oxide is transformed enantioselectively to chiral (S)- or (R)-2-cyclohexen-1-ol by the reaction with the appropriate chiral lithium amide reagent has been evaluated theoretically using the MM3 force field. The plausible possible structures for each precursor (reaction intermediate complex) leading to a (S)- or (R)-2-cyclohexen-1-ol have been optimized with the extended MM3 force field applicable to the lithium amide functional group, and the populations of their (S)- or (R)-reaction intermediate complexes at an ambient temperature (298 K) were calculated. The initial structure for evaluating the reaction intermediates of this asymmetric synthesis was constructed on the basis of the optimized ab initio transition state structure (MP2/6-31+G^∗) comprising lithium amide LiNH₂ and propene oxide. To the thus obtained transition state structure composed of LiNH₂ and propene oxide, the other remaining Cartesian coordinates for the actual reaction intermediates composed of the chiral lithium amides and cyclohexene oxide were added to make the reaction intermediate structure. The conformational search for the reaction intermediate has been carried out by using the Stochastic search Algorithm, and the optimized geometries and their conformational energies (steric energies) have been calculated by the MM3 force field. The populations calculated from the conformational energies of the reaction intermediate leading to the (S)- or (R)-2-cyclohexen-1-ol were shown to be linearly well correlated with the experimentally reported enantiomer excess (% ee) values. The critical factors to control the enantioselectivity were investigated on the basis of the optimized structures of the reaction intermediate complexes. The MM3 force field approach was shown to be applicable to the theoretical evaluation of the enantioselectivity and be useful for designing a new functional chiral lithium amide reagent for the asymmetric synthesis.     

Co doped ZnO nanowires as visible light photocatalysts

High aspect ratio cobalt doped ZnO nanowires showing strong photocatalytic activity and moderate ferromagnetic behaviour were successfully synthesized using a solvothermal method and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), vibrating sample magnetometry (VSM) and UV–visible absorption spectroscopy. The photocatalytic activities evaluated for visible light driven degradation of an aqueous methylene orange (MO) solution were higher than for Co doped ZnO nanoparticles at the same doping level and synthesized by the same synthesis route. The rate constant for MO visible light photocatalytic degradation was 1.9·10⁻³ min⁻¹ in case of nanoparticles and 4.2·10⁻³ min⁻¹ in case of nanowires. We observe strongly enhanced visible light photocatalytic activity for moderate Co doping levels, with an optimum at a composition of Zn_0.95Co_0.05O. The enhanced photocatalytic activities of Co doped ZnO nanowires were attributed to the combined effects of enhanced visible light absorption at the Co sites in ZnO nanowires, and improved separation efficiency of photogenerated charge carriers at optimal Co doping.