Chiral Carbonaceous Nanotubes Containing Twisted Carbonaceous Nanoribbons,Prepared by the Carbonization of Chiral Organic Self‐Assemblies

Single‐handed helical silica nanotubes containing chiral organic self‐assemblies were prepared by using a supramolecular templating approach. After carbonization and the removal of the silica, single‐handed helical carbonaceous nanotubes that contained twisted carbonaceous nanoribbons were obtained. It is believed that the nanotubes formed as a result of the adsorption of low‐molecular‐weight gelators. The twisted nanoribbons were formed because of the carbonization of the organic self‐assemblies. The samples were characterized by using field‐emission scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Raman spectroscopy, and circular dichroism. For the samples carbonized at 900 °C for 3.0 h, a partially graphitized structure was identified. The circular dichroism (CD) spectra indicated that the twisted nanoribbons exhibited optical activity. The CD spectrum was simulated by using time‐dependent density functional theory. The results suggested that the CD signals originated from the chiral stacking of aromatic rings.     

A Better Understanding of the Formation of Silica Nanococoons

Silica nanococoons with coiled or concentric circular pore channels in the walls attracted much attention, recently. However, the formation of them is not well illustrated. Herein, hollow silica shells with organized pore channels parallel to the shell surface were prepared through a single‐templating method using the self‐assemblies of a chiral low‐molecular‐weight amphiphile,L‐18Phe6PyBr, as templates under a dilute concentration. These nanococoons were characterized using X‐ray diffractometer and N₂ sorption. The formation of them was clearly shown in the field‐emission electron microscopy images which were taken at a low voltage. Moreover, transmission electron microscopy images taken after different reaction times indicated a cooperative self‐assemble mechanism. It was also found that the nanocoons were formed from coiled nanoribbons.     

低浓度下的仿生矿化及其在对映体拆分中的应用

以L-苯丙氨酸衍生物(L-18Phe6PyBr)的自组装体为模板, 在0.30 mmol/L的浓度下, 研究了pH值、 老化时间和四乙氧基硅烷(TEOS)浓度对二氧化硅形貌的影响. 通过扫描电子显微镜和透射电子显微镜对样品进行表征. 结果表明, 在pH=10.01的条件下可以得到左手扭转的纳米带, 而pH=7.15和12.34时, 得到直线的纳米带. 遵循动态模板的方法, 老化时间的延长有利于直线纳米带的形成. 随着TEOS和L-18Phe6PyBr的质量比由2:1增加到15:1, 扭转纳米带的宽度增加, 螺距变长. 通过煅烧除去有机模板后, 得到带状二氧化硅纳米管. 将TEOS与L-18Phe6PyBr质量比为2:1制备得到的二氧化硅作为气相色谱固定相, 涂渍到毛细管色谱柱中进行对映体拆分. 结果表明, 该气相色谱柱可以拆分1-苯基-1-丙醇、 1-(4-氯苯基)乙醇和2-甲基戊酸3种外消旋化合物, 手性超分子印迹是拆分对映体的主要作用力. 对二氧化硅低聚物与小分子凝胶的协同组装行为以及将无机材料作为手性固定相有了一个更好的认识.     

Single‐Handed Helical Carbonaceous Nanotubes: Preparation,Optical Activity,and Applications

Carbon‐based nanomaterials have been widely studied in the past decade. Three approaches have been developed for the preparation of single‐handed helical carbonaceous nanotubes. The first approach uses the carbonization of organopolymeric nanotubes, where the organic polymers are polypyrrole, 3‐aminophenol‐formaldehyde resin, and m‐diaminobenzene‐formaldehyde resin. The second approach uses the carbonization of aromatic ring‐bridged polybissilsesquioxane followed by the removal of silica. Micropores exist within the walls of the carbonaceous nanotubes. The third approach uses the carbonization of organic compounds within silica nanotubes. This hard‐templating approach drives the formation of helical carbonaceous nanotubes containing twisted carbonaceous nanoribbons. All of these helical carbonaceous nanotubes exhibit optical activity, which is believed to originate from the chiral π‐π stacking of aromatic rings. They can be used as chirality inducers, and for lithium‐ion storage.     

Bi2O2Se纳米带的气-液-固生长与高性能晶体管的构筑

Nanostructured bismuth oxyselenide (Bi₂O₂Se) semiconductor, a two-dimensional (2D) materials with high-mobility, air-stability, and tunable bandgap, has recently emerged as a candidate of channel material for future digital (electronic and optoelectronic) applications. In terms of material morphology, some basic issues will be addressed when a two-dimensional layered crystal is shaped into a one-dimensional (1D) geometry due to size effect; these include the space-confined transport in a plane, which leads to dramatic changes in electronic, optical, and thermal properties. These novel 1D nanostructures with unique properties are an optimal choice for fabricating next-generation integrated circuits and functional devices within the nanometer scale such as gate-all-around field-effect transistors, single-electron transistors, chemical sensors, and THz detectors. As one of the high-mobility 2D semiconductor, 1D high-quality Bi₂O₂Se nanoribbons could be promising for applications in high-performance transistors; however, their synthesis has not been completely developed yet. In our study, we report on the facile growth of Bi₂O₂Se nanoribbons on mica substrates via a bismuth-catalyzed vapor-liquid-solid (VLS) mechanism. The preparation of Bi₂O₂Se nanoribbons is based on a previous work that emphasized on the oxidation of Bi₂Se₃ in a chemical vapor deposition (CVD) system and the use of bismuth (Bi) particles as the precursor of Bi catalysis. The morphology, composition, and structure of the as-grown Bi₂O₂Se nanoribbons were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, transmission electron microscopy (TEM), as well as other methods. For a Bi mediated VLS growth process, the growth of Bi₂O₂Se nanoribbons can be self-assembled; further, in this process, as-grown epitaxial Bi₂O₂Se nanoribbons are free-standing with out-of-plane morphology on the mica substrate. Additionally, combining the spherical aberration corrected transmission electron microscope (ACTEM) and selected electron diffraction (SAED) methods, we discovered that the as-synthesized Bi₂O₂Se nanoribbons were single crystalline with high quality. We further investigated the controllable growth for domain size by optimizing the growth temperature of the Bi₂O₂Se nanoribbons. As-synthesized single-crystal Bi₂O₂Se nanoribbons have widths in the range of 100 nm to 20 μm and lengths in the sub-millimeter range. By employing a polymer poly(methyl methacrylate) (PMMA) assisted clean transfer method with the assistance of deionized water, the Bi₂O₂Se nanoribbons can be easily transferred onto a SiO₂/Si substrate. Fabricated into the top-gated field-effect device, the Bi₂O₂Se nanoribbon sample (transferred to the SiO₂/Si substrate) exhibited high electronic performances; these included a high electron mobility of ∼220 cm²∙V⁻¹∙s⁻¹ at room temperature, good switching behavior with on/off ratio of > 10⁶, and high on current density of ∼42 μA∙μm⁻¹ at a channel length of 10 μm. Therefore, Bi₂O₂Se nanoribbons are expected to be a promising materials for building high-performance transistors in the future.     

Control of mesoporous silica nanostructures and pore-architectures using a thickener and a gelator

A chiral cationic thickener l-ValPyBr, which was able to enhance the viscosity of water and form loosely physical gel in mixtures of water and alcohols, was synthesized. Sol-gel polymerization of TEOS was carried out in mixtures of water and alcohols under basic conditions using the self-assemblies of l-ValPyBr as template. The left-handed twisted mesoporous silica nanoribbons, which were constructed by nanotubes in monolayer, were obtained, and they tended to self-assemble into bundle structure. Stirring under the preparation process played an important role in the formation of this bundle structure. The obtained silica nanoribbons were uniform in width, thickness, and helical pitch without combining amorphous particles. The helical pitch and pore size of the mesoporous silica nanoribbons sensitively depended on the volume ratio of alcohols to water in the reaction mixtures. With increasing volume ratio of alcohols to water in the reaction mixture, the morphologies of the obtained silica changed from left-handed twisted ribbon to coiled ribbon, then to tubular structure. A compound l-ValPyPF6, structurally related to thickener l-ValPyBr, was able to form physical gel in ethanol, THF, acetonitrile, and the mixtures of ethanol and water. Left-handed multiple helical mesoporous silica nanofibers were prepared by using the self-assemblies of l-ValPyPF6 as template in mixtures of water and alcohols under basic conditions. By controlling both the volume ratio of ethanol to water and the weight ratio of l-ValPyPF6 to TEOS, two- or three-dimensional pore-architecture constructed by porous chiral nanotubes was obtained.     

Facile One‐Pot Fabrication of Hollow Porous Silica Nanoparticles

A method for the fabrication of hollow silica nanospheres, a facile one‐pot hydrothermal route, is described. Heating of an aqueous solution of water glass and D ‐glucose to 180 °C for 24 h affords—as indicated by transmission electron microscopy—a nanospherical composite consisting of a silica shell sheathing a carbonaceous core. Subsequent removal of the carbonaceous interior through oxidation in air produces hollow silica structures. Variation of the concentration of the two jointly dissolved chemicals enables a variation of the thickness of the silica shell. The hollow silica particles were characterized by means of SEM, TEM, XRD, IR spectroscopy, thermogravimetrical analysis (TGA), and sorption measurements.     

Size Controlling Preparation,Adsorption and Catalytic Properties of Silica Microspheres

The size-controlled silica microspheres were prepared by a facile method and the growth mechanism was simply studied. The as-prepared samples were characterized by scanning electron microscopy and transmission electron microscopy. The CO₂ adsorption behaviors and methane catalytic oxidation were also measured. The results show that the as-prepared silica is perfect sphere, and the particle size can be controlled by adding tartaric acid. Spherical silica and sphere/tube(rod)-shaped silica were obtained by adjusting reaction time. Silica microspheres with uniform size exhibit high capacity of CO₂ adsorption, while others with wide size-distribution exhibit excellent catalytic performance, suggesting it is an effective method by regulating size to utilize its advantages selectively. Therefore, it will be an ideal strategy to develop the efficient multifunctional materials by a facile route.     

A catalytic chemical vapor deposition synthesis of double-walled carbon nanotubes over metal catalysts supported on a mesoporous material

Double-walled carbon nanotubes (DWNTs) have been synthesized by catalytic chemical vapor deposition (CCVD) over supported metal catalysts decomposed from Fe(CH₃COO)₂ and Co(CH₃COO)₂ on mesoporous silica. Bundles of tubes with relatively high percentage of DWNTs, in areas where tubular layered structures could be clearly resolved, have been observed by transmission electron microscopy (TEM). In other areas, crystal-like alignment of very uniform DWNTs was observed for the first time, suggesting that mesoporous silica might play a templating role in guiding the initial nanotube growth. In addition, compatible with nano-electronics research, bridging of catalytic islands by DWNTs has also been demonstrated.     

Preparation of Single‐Handed Helical Carbon/Silica and Carbonaceous Nanotubes by Using 4,4′‐Biphenylene‐Bridged Polybissilsesquioxane

Single‐handed, helical, 4,4′‐biphenylene‐bridged polybissilsesquioxane nanotubes were prepared by using the self‐assemblies of a pair of chiral low‐molecular‐weight gelators as templates. Single‐handed, helical, carbon/silica nanotubes were obtained after carbonization of the self‐assemblies, and single‐handed helical carbonaceous nanotubes were then obtained by removal of silica with aqueous HF. Samples were characterized by using field‐emission SEM, TEM, X‐ray diffraction, thermogravimetric analysis, Raman spectroscopy, and circular dichroism. The polysilsesquioxane and carbonaceous structures exhibited optical activity. The walls of the carbon/silica and carbonaceous nanotubes were predominantly amorphous carbon. The surface area of the left‐handed, helical, carbonaceous nanotubes was 1439 m² g^?1, and such materials have potential applications as catalyst supports, chirality sensors, supercapacitor electrodes, and adsorbents.     

Rh-Mn-Li/SiO2催化剂上CO加氢制C2含氧化合物:载体硅烷化程度的影响

以三甲基氯硅烷为硅烷化试剂,对硅胶进行不同程度硅烷化预处理,采用浸渍法制备了其负载的Rh-Mn-Li催化剂,用于CO加氢制C₂含氧化合物的反应,并运用红外光谱、N₂吸附-脱附法、C含量测定、透射电镜、H₂程序升温还原和程序升温表面反应等手段对载体和催化剂进行了表征。结果表明,制得的不同硅烷化程度硅胶织构性质变化不大,它们负载的催化剂上Rh平均粒径均在3nm左右,硅烷化对催化剂吸附CO的形态和Rh的还原性能的影响均很小,但随着载体硅烷化程度的提高,催化剂上Rh解离CO的能力增加,因而其活性逐渐增加,且不影响C₂含氧化合物的选择性。     

A novel catalyst based on electrospun silver-doped silica fibers with ribbon morphology

Mesoporous silica nanofibers and Ag-doped composite nanoribbons were synthesized by a facile combination of an electrospinning technique and the sol–gel method. Tetraethyl orthosilicate, polyvinylpyrrolidone (PVP), triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), copolymer Pluronic P123, and silver nitrate (AgNO₃) were the components of sol for the production of Ag-doped hybrid silica ribbons. Heat removal of structure-directing agent P123 in the hybrid fibers at high temperatures resulted in a mesoporous morphology, and the degradation of PVP caused AgNO₃ to convert into silver in the form of nanoparticles. The size and content of the particles in the hybrid ribbons could be controlled by the concentration of AgNO₃ and thermal treatment conditions. Scanning electron microscopy, N₂ adsorption–desorption isotherm, transmission electron microscopy, X-ray diffraction, and UV–Vis spectroscopy were used to characterize the composite ribbons. The catalytic activity of the ribbons was evaluated by reduction of methylene blue dye and found to be better than in previous studies.     

SiO2@Fe2O3核-壳结构催化剂的制备及表征

采用优化的Stöber法制备了平均粒径为230 nm的单分散球形SiO₂颗粒,并以此为内核,通过水解沉积法制备了不同壳层厚度的核-壳结构SiO₂@Fe₂O₃催化剂。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、N₂物理吸附和X射线衍射分析(XRD)等手段对催化剂进行表征,探讨了不同制备条件对SiO₂@Fe₂O₃催化剂形貌的影响。结果表明,通过水解沉积法制备的SiO₂@Fe₂O₃催化剂具有明显的核-壳结构,并且保持了原始SiO₂核的球形形貌,Fe₂O₃纳米粒子通过-OH的氢键作用连接在SiO₂表面,形成了2~10 nm厚的Fe₂O₃均匀连续包覆层。     

Silver-coated TiO2 nanostructured anode materials for lithium ion batteries

Anatase TiO₂ nanoribbons/nanotubes (TiO₂-NRTs) have been synthesised successfully via a reflux method followed by drying in a vacuum oven, and then, silver-coated TiO₂ NRTs (Ag/TiO₂-NRTs) were prepared by coating silver particles onto the TiO₂-NRTs surface by the traditional silver mirror reaction. The physical properties of the synthesised products were examined in detail using X-ray diffraction, field emission gun scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy, respectively. The results indicated that the Ag nanoparticles were uniformly deposited on the surface of the TiO₂ nanoribbons/nanotubes. The electrochemical properties were investigated by a variety of techniques. The rate capability and cycle durability for the Ag/TiO₂-NRTs were improved compared with TiO₂-NRTs. It is speculated that the Ag-coated TiO₂ nanoribbons/nanotubes are an effective anode candidate for lithium ion batteries.     

以短链季铵盐/脂肪酸盐为模板合成超微孔二氧化硅

超微孔材料具有1~2 nm的孔径,在分离、催化应用中有望展现出择形催化的能力。 寻找经济、简便的合成超微孔材料的表面活性剂体系是一项有意义的工作。 本研究以短链季铵盐(十烷基三甲基溴化铵,记为C₁₀TAB)和不同链长脂肪酸酸盐混合胶束为模板剂,硅酸钠为硅源,成功制备出高度有序超微孔SiO₂。 通过小角X射线衍射、N₂吸附-脱附、傅里叶变换红外光谱、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等技术手段对产品的结构和性能进行了表征。 结果表明,合成体系中脂肪酸盐碳链长、加入量、晶化温度等对产物孔道有序性有很大影响。 当选择正辛酸钠(SO)为助表面活性剂,当n(C₁₀TAB):n(Na₂SiO₃):n(SO):n(H₂O)=1:1.5:0.3:800,晶化温度为80 ℃时,可以得到高度有序超微孔SiO₂。 煅烧后样品比表面积为1300 m²/g,孔体积0.49 cm³/g,孔径分布在1.90 nm。     

Preparation and characterization of a novel pyrrole-benzophenone copolymerized silica nanocomposite as a reagent in a visual immunologic-agglutination test

Biological sensing is explored through novel stable colloidal dispersions of pyrrole-benzophenone and pyrrole copolymerized silica (PPy-SiO₂-PPyBPh) nanocomposites, which allow covalent linking of biological molecules through light mediation. The mechanism of nanocomposite attachment to a model protein is studied by gold labeled cholera toxin B (CTB) to enhance the contrast in electron microscopy imaging. The biological test itself is carried out without gold labeling, i.e., using CTB only. The protein is shown to be covalently bound through the benzophenone groups. When the reactive PPy-SiO₂-PPyBPh-CTB nanocomposite is exposed to specific recognition anti-CTB immunoglobulins, a qualitative visual agglutination assay occurs spontaneously, producing as a positive test, PPy-SiO₂-PPyBPh-CTB-anti-CTB, in less than 1 h, while the control solution of the PPy-SiO₂-PPyBPh-CTB alone remained well-dispersed during the same period. These dispersions were characterized by cryogenic transmission microscopy (cryo-TEM), scanning electron microscopy (SEM), FTIR and X-ray photoelectron spectroscopy (XPS).     

负载氯的分级多孔炭制备及其脱汞性能的研究

以纳米碳酸钙为模板,水稻秸秆为碳前驱体,采用共热解法制备了负载氯的分级多孔生物质炭。在模拟烟气条件下,利用固定床实验台架研究了生物质碳材料对烟气中的单质汞（Hg⁰）的脱除性能。采用扫描电镜（SEM）、透射电镜（TEM）、N₂吸附-脱附（BET）、程序升温脱附（Hg-TPD）以及X射线光电子能谱（XPS）等方法对材料进行表征。结果表明,盐酸浸渍不仅可去除模板产物生成多孔结构,并且有效地将氯负载到材料表面。负载氯的分级多孔炭B1C1-Cl2的比表面积和总孔容分别达到398.1 m²/g和0.4923 cm³/g。在120℃,空速（GHSV）为225000 h^-1时,脱汞效率可达95%。多孔结构有利于气体扩散,高比表面积为材料提供了更多的反应位点,微孔-介孔内表面上的C-Cl共价键为脱汞的主要化学吸附活性位点。     

Density fractionated hollow silica microspheres with high-yield by non-polymeric sol–gel/emulsion route

Hollow silica microspheres were synthesized by non-polymeric sol–gel/emulsion technique using tetra ethyl orthosilicate (TEOS) as a source of silica. A sol mixture of TEOS, water, ethanol and acid was emulsified in a solution of light paraffin oil and surfactant (Span-80). Calcined spheres were density fractionated between density ranges: <1.0, 1.0–1.594, 1.594–1.74 and >1.74 g cm⁻³. The samples were characterized by optical and scanning electron microscopy with energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and laser diffraction size analyzer. Spheres of densities lower than 1.74 g cm⁻³ were found to be hollow as observed from scanning electron microscopy (SEM) images and their yield was maximized to 100% by using a specific TEOS volume ratio with respect to volumes of surfactant and oil. Decreasing the calcination temperature from 700 to 500 °C enhances the yield of hollow spheres emphasizing importance of slower diffusion kinetics at lower calcination temperature. Outer diameters of spheres were between 5 and 60 μm with mean diameter expectedly increasing with increase in TEOS sol volume and with decrease in sphere density. It is proposed that silica shells form via hydrolysis and polycondensation at oil–water/ethanol interface in the water-in-oil emulsion, which subsequently form hollow spheres on removal of water–ethanol during calcination.     

Free-standing vanadium pentoxide nanoribbon film as a high-performance cathode for rechargeable sodium batteries

Vanadium pentoxide(V_2O_5·nH_2O) nanoribbons are synthesized via a hydrothermal process. These ribbons are 20 nm thick, 200 nm to 1 μm wide and several tens of micrometers long. Free-standing binder-free films are prepared by using these nanoribbons with multi-walled carbon nanotubes(MWCNTs) and used as the cathode for rechargeable sodium batteries. The large interlayer space between the V_2O_5 bilayers can enhance the kinetics of sodium ion intercalation/deintercalation. In addition, the intertwining network of the V_2O_5·0.34 H_2O film provides efficient electron conduction pathways and shortens diffusion distances of sodium ion. The electrochemical tests prove that the freestanding V_2O_5 · 0.34 H_2O film cathode delivers high reversible specific capacities(190 mAh/g) and good cycling stabilities(170 mAh/g after 150 cycles) in the voltage range between 1.5 V and 3.5 V.