Synthesis and characterization of double-walled carbon nanotubes from multi-walled carbon nanotubes by hydrogen-arc discharge

Double-walled carbon nanotubes (DWNTs) were synthesized in a large scale by a hydrogen arc discharge method using graphite powders or multi-walled carbon nanotubes/carbon nanofibers (MWNTs/CNFs) as carbon feedstock. The yield of DWNTs reached about 4 g/h. We found that the DWNT product synthesized from MWNTs/CNFs has higher purity than that from graphite powders. The results from high-resolution transmission electron microscopy observations revealed that more than 80% of the carbon nanotubes were DWNTs and the rest were single-walled carbon nanotubes (SWNTs), and their outer and inner diameters ranged from 1.75 to 4.87 nm and 1.06 to 3.93 nm, respectively. It was observed that the ends of the isolated DWNTs were uncapped and it was also found that cobalt as the dominant composition of the catalyst played a vital role in the growth of DWNTs by this method. In addition, the pore structures of the DWNTs obtained were investigated by cryogenic nitrogen adsorption measurements.     

High quality double wall carbon nanotubes with a defined diameter distribution by chemical vapor deposition from alcohol

We have synthesized double wall carbon nanotubes (DWNTs) with few defects and little amorphous carbon by hot wall chemical vapor deposition (CVD) of alcohol. Catalysts for the DWNT growth were made from cobalt and molybdenum acetates. Scanning electron microscopy, transmission electron microscopy, multi frequency resonance Raman spectroscopy and optical absorption spectroscopy were used for characterization of the product with regard to DWNT yield, the nanotube diameter distribution, defect concentration and amorphous carbon content. Base pressures lower than 1 × 10⁻⁵ mbar in the CVD reactor considerably suppress defects in the DWNTs. Optimized growth conditions for DWNT formation are presented.     

Synthesis of double-walled carbon nanotubes from coal in hydrogen-free atmosphere

Double-walled carbon nanotubes (DWNTs) were synthesized from coal in large quantity by arc-discharge method in hydrogen-free atmosphere, which were systematically examined using scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The results show that the as-synthesized DWNTs have an outer diameter of 1.0–5.0 nm with an interlayer spacing in the tube walls of ca. 0.41 nm. The possible mechanism involved in the formation process of DWNTs is proposed and discussed in term of the unique chemical composition of coal and the process parameters adopted in the study.     

Promotion of the yield and graphitic nature of filamentous carbon grown from Ni/SiO2 doped with lithium bromide

The catalyzed growth of ordered filamentous carbon from a hydrogen/ethylene feedstock has been studied using Ni/SiO₂ doped with LiBr. The introduction of the alkali halide resulted in a significant increase in carbon yield while the catalytically generated carbon exhibited a higher degree of structural order. The latter has been determined from high-resolution transmission electron microscopy (HRTEM) and temperature programmed oxidation (TPO) analyses. Carbon yield and structural enhancement is linked to a restructuring of the active sites that facilitates a destructive chemisorption of ethylene and the dissolution and precipitation of carbon in an ordered fashion.     

A comparison of reinforcement efficiency of various types of carbon nanotubes in polyacrylonitrile fiber

Polyacrylonitrile (PAN)/carbon nanotubes (CNTs) composite fibers were spun from solutions in dimethyl acetamide (DMAc), using single wall (SWNTs), double wall (DWNTs), multi wall (MWNTs) carbon nanotubes, and vapor grown carbon nanofibers (VGCNFs). In each case, CNT content was 5 wt% with respect to the polymer. Structure, morphology, and properties of the composite fibers have been characterized using X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, tensile tests, dynamic mechanical tests, as well as thermal shrinkage. While all nanotubes contributed to property improvements, maximum increase in modulus (75%) and reduction in thermal shrinkage (up to 50%) was observed in the SWNT containing composites, and the maximum improvement in tensile strength (70%), strain to failure (110%), and work of rupture (230%) was observed in the MWNTs containing composites. PAN orientation is higher in the composite fiber (orientation factor up to 0.62) than in the control PAN fiber (orientation factor 0.52), and the PAN crystallite size in the composite fiber is up to 35% larger than in the control PAN (3.7 nm), while the overall PAN crystallinity diminished slightly. Nanotube orientation in the composite fibers is significantly higher (0.98 for SWNTs, 0.88 for DWNTs, and 0.91 for MWNTs and VGCNFs) than the PAN orientation (0.52-0.62). Improvement in low strain properties (modulus and shrinkage) was attributed to PAN interaction with the nanotube, while the improvement in high strain properties (tensile strength, elongation to break, and work of rupture) at least in part is attributed to the nanotube length. Property improvements have been analyzed in terms of nanotube surface area and orientation.     

Optical Properties of Composites Based on Poly(o-phenylenediamine), Poly(vinylenefluoride) and Double-Wall Carbon Nanotubes

In this work, synthesis and optical properties of a new composite based on poly(o-phenylenediamine) (POPD) fiber like structures, poly(vinylidene fluoride) (PVDF) spheres and double-walled carbon nanotubes (DWNTs) are reported. As increasing the PVDF weight in the mixture of the chemical polymerization reaction of o-phenylenediamine, the presence of the PVDF spheres onto the POPD fibers surface is highlighted by scanning electron microscopy (SEM). The down-shift of the Raman line from 1421 cm⁻¹ to 1415 cm⁻¹ proves the covalent functionalization of DWNTs with the POPD-PVDF blends. The changes in the absorbance of the IR bands peaked around 840, 881, 1240 and 1402 cm⁻¹ indicate hindrance steric effects induced of DWNTs to the POPD fiber like structures and the PVDF spheres, as a consequence of the functionalization process of carbon nanotubes with macromolecular compounds. The presence of the PVDF spheres onto the POPD fiber like structures surface induces a POPD photoluminescence (PL) quenching process. An additional PL quenching process of the POPD-PVDF blends is reported to be induced in the presence of DWNTs. The studies of anisotropic PL highlight a change of the angle of the binding of the PVDF spheres onto the POPD fiber like structures surface from 50.2° to 38° when the carbon nanotubes concentration increases in the POPD-PVDF/DWNTs composites mass up to 2 wt.%.     

卤代环戊烷合成工艺研究进展

综述了环戊醇羟基取代法、环戊烯加成法及环戊烷氢原子与卤原子交换法合成卤代环戊烷工艺路线，以环戊醇为原料合成卤代环戊烷是比较常用的合成方法。环戊烷与二卤甲烷、SbF5或三卤化铝反应也可用于卤代环戊烷的合成。两种合成工艺所需的原料或试剂昂贵，副产物较多，不适宜工业生产。环戊烯与氢卤素加成反应制备卤代环戊烷，工艺流程简单，原料经济，收率高，易实现工业化。     

Copper‐Catalyzed Coupling of (E)‐Bromostilbene with Phenols/Azole: ESI‐MS Detection of Intermediates by Using an Ionically‐Tagged Ligand

A system based on copper/1,10‐phenanthroline efficiently promotes the coupling between phenols or pyrazole with (E)‐bromostilbene. (E)‐1‐Aryloxy‐1,2‐diphenylethenes were obtained from the coupling with phenols in good to excellent yields (69–90%). The exception was the reaction involving a phenol containing an electron‐withdrawing cyano group that required a longer reaction time and gave only 49% yield. Kinetic studies indicated the participation of the vinyl halide in the rate‐determining step. Under the conditions employed, the activation of the vinyl halide via a radical pathway was discarded using a radical scavenger test. By using an ionically‐tagged 1,10‐phenanthroline derivative as the ligand, various copper‐based ions were detected through ESI(+)‐MS. These ions suggested that formation of the active species [phenCuOAr(HOAr)₂] precedes the vinyl halide activation.     

Ferrocene-filled single-walled carbon nanotubes

Ferrocene molecules are successfully introduced into the inner hollow space of Single-walled carbon nanotubes (SWNTs) to get ferrocene-filled SWNTs (Fc@SWNTs). This nanohybrid material was carefully characterized by high resolution microscopy, FTIR spectrum, and Cyclic voltammetry (CV). This new material may not only act as air stable n-type field-effect transistors based on nanotubes, but it may also be employed as building blocks for various devices based on the redox activity of ferrocene. What’s more, upon high temperature annealing, the encapsulated ferrocene molecules will decompose and change into interior tubes, forming double-walled carbon nanotubes (DWNTs). This provides convincing evidence that ferrocene molecules are inserted into the hollow cavities SWNTs. This result also presented a controllable way to synthesize DWNTs.     

Diameter-selective dispersion of double-walled carbon nanotubes by lysozyme

We have utilized lysozyme to non-covalently functionalize and disperse double-walled carbon nanotubes (DWNTs) in aqueous solution. Lysozyme preferentially binds and disperses DWNTs with larger diameters. This is a facile and effective method to fractionalize and enrich DWNTs with certain diameters.     

新型中空卤化银颗粒乳剂的制备和性能研究 Ⅳ.利用非水溶剂制备中空卤化银颗粒乳剂

有近１６０年历史的银盐卤化银乳剂制备的感光材料，到目前为止仍不失为一种优良的信息记录材料．但昂贵的白银的缺乏和消耗，使得节银和降低成本成为银盐感光材料生产中急需要解决的问题．另一方面在感光材料的制备和使用过程中，绝大部分过程（如化学增感、光谱增感、潜...     

纤维状双壁碳纳米管／聚苯胺复合材料的表面及孔结构

通过原位化学聚合过程制备了双壁碳纳米管／聚苯胺（double—walled carbon naontube／polyaniline,DwNT／PAn）复合材料。复合材料呈一维纤维状结构,聚苯胺被均匀包覆在碳管外部。根据低温氮吸附实验结果,复合材料的吸附等温线与双壁碳纳米管相似,仍为多步吸附过程,但由于聚苯胺包覆在碳纳米管外部和端口,导致其表面所含的微孔消失,小中孔含量明显降低。     

氨基膦酸树脂负载铜配合物对Ullmann反应的催化性能

研究了氨基膦酸树脂负载铜配合物(简写为APAR-Cu(Ⅱ))在卤代芳烃及杂环卤代芳烃与咪唑或苯并咪唑的Ullmann反应中的催化性能.实验结果表明,120℃时,以DMSO作为溶剂,KOH作为碱,APAR-Cu(Ⅱ)能较好地催化该偶联反应,反应收率达67％ ～95％,且可以多次重复使用.     

High-precision imaging of an encapsulated Lindqvist ion and correlation of its structure and symmetry with quantum chemical calculations

Low-voltage aberration-corrected transmission electron microscopy (AC-TEM) of discrete Lindqvist [W(6)O(19)](2-) polyoxometalate ions inserted from an ethanolic solution of [NBu(4)](2)[W(6)O(19)] into double walled carbon nanotubes (DWNTs) allows a higher precision structural study to be performed than previously reported. W atom column separations within the constituent W(6) tungsten cage can now be visualized with sufficient clarity that reliable correlation with structural predictions from density functional theory (DFT) can be achieved. Calculations performed on [W(6)O(19)](2-) anions encapsulated in carbon nanotubes show good agreement with measured separations between pairs of W(2) atom columns imaged within equatorial WO(6) polyhedral pairs and also single W atom positions located within individual axial WO(6) octahedra. Structural data from the tilted chiral encapsulating DWNT were also determined simultaneously with the anion structural measurements, allowing the influence of the conformation of the encapsulating tubule to be included in the DFT calculation and compared against that of other candidate encapsulating nanotubes. Additional DFT calculations performed using Li(+) cations as a model for the [NBu(4)](+) counterions indicate that the latter may help to induce charge transfer between the DWNT and the [W(6)O(19)](2-) ion and this may help to constrain the motion of the ion in situ.     

Multiple intra-tube junctions in the inner tube of peapod-derived double walled carbon nanotubes: theoretical study and experimental evidence

The coalescence process of fullerenes in the hollow core of single walled carbon nanotubes is systematically explored by the kinetic Monte Carlo method. Two elongation (or growth) modes via the coalescence (i) between an inner tube and fullerenes and (ii) between neighboring inner tubes are identified. It is found that the coalescence of two inner tubes mostly creates a very stable intra-tube junction which is composed of multiple pentagon-heptagon pairs. As a consequence, the study predicts that the inner tube of peapod derived double walled carbon nanotubes (DWNTs) must contain many intra-tube junctions. Careful high resolution transmission electron microscopy observation on peapod-grown DWNT sample provides experimental evidence of the presence of the junctions.     

对甲基苯基氯化镁的合成工艺改进

对甲基苯基卤化镁是合成2-氰基-4'-甲基联苯的重要原料,后者是最新一代沙坦类抗高血压药物的关键中间体。价廉的对氯甲苯原料在格氏反应中由于引发困难,影响了对甲基苯基氯化镁格氏试剂的应用。本文以镁粉、对氯甲苯为原料,在无水2-甲基四氢呋喃-四氢呋喃混合溶剂中制备格氏试剂,对影响反应的多种因素进行了研究,确定了最优工艺条件,合成收率达95.4%。与传统工艺方法相比,本文方法降低了装置无水性要求,操作简便,收率较高。该工艺为对甲基苯基卤化镁格氏试剂的生产提供了可行的技术路线,可显著降低2-氰基-4'-甲基联苯的合成成本。     

水性超薄型防火涂料的制备及其性能

以有机硅改性丙烯酸树脂为基础树脂,聚磷酸铵、季戊四醇、三聚氰胺为化学阻燃剂,可膨胀石墨为物理阻燃剂,制备了结构钢用水性超薄型防火涂料。采用高温加热、垂直燃烧法、扫描电子显微镜、热重分析、X射线衍射等研究了基础树脂与不同阻燃剂的配比对涂料防火性能的影响。结果表明:基础树脂、化学阻燃剂与物理阻燃剂的质量比为7∶11∶2时,所配制涂料的膨胀倍率达17.78倍,耐火时间为52 min且生成了高质量的炭层。该涂料刷涂方便,可明显提高结构钢到达屈服极限的时间,增加高温使用寿命。     

铒镱共掺磷酸镧纳晶的合成和近红外荧光性质

以磷酸三丁酯作为配体,使用高温溶液法合成了掺铒磷酸镧纳米晶体,高分辨电镜和XRD结果表明产物尺寸均一,直径4nm左右,具有高度的结晶性,在甲苯等有机溶剂中分散性良好.近红外发光光谱表明,产物在1535 nm处有发光峰,半高全宽为50 nm,高于目前掺铒光纤放大器(EDFA)的增益带宽.通过IR、元素分析研究发现,使用真空干燥等方法不能有效去除纳晶表面的羟基.为了进一步消除表面缺陷和猝灭基团对纳晶发光性质的影响,我们尝试在其外围生长一层LaPO_4壳做成核壳粒子以消除表面缺陷和隔离猝灭基团,结果表明,新的纳晶的发光强度得到了显著提高.     

离子液体预处理油料作物木质纤维素

选取了3种离子液体：氯化1-丁基-3-甲基咪唑([Bmim]Cl)、溴化1-丁基-3-甲基咪唑([Bmim]Br)以及氯化1-辛基-3-甲基咪唑([Omim]Cl),对油料作物木质纤维素部分：花生秸秆、花生壳以及油菜秸秆进行了预处理。对处理前后的物料进行了组分、酶解产糖以及结构分析。原料经酶解后,花生秸秆的产糖率最高(54.31%),且木质素含量最低,表明其更利于生物燃料的生产。3种离子液体中[Bmim]Cl预处理效果最好,产糖率最高可达85.43%(花生秸秆)。采用扫描电镜(SEM)和红外光谱(FT-IR)分析,花生秸秆表面最不完整,结构松散,结晶区域少。经离子液体处理后,所有物料均变得疏松多孔,表面粗糙,提高了物料的可及度。在此基础上,分析阴阳离子对于木质纤维素的溶解过程,发现氯离子和[Bmim]⁺对于纤维素的溶解影响最显著。     

Deep red emission from Cs4PbI6/CsPbI3/ZnS heterostructure for enhanced stability and photoluminescence quantum yield

Inorganic halide perovskites have been regarded as fancy materials for the lighting and bio-medicine industry due to their wondrous photo-physical features. However, the instability concerns restrict their usage to some extent. Here, we demonstrated deep red emission from Cs₄PbI₆/CsPbI₃/ZnS heterostructure by using a typical hot injection process. The as-obtained Cs₄PbI₆/CsPbI₃/ZnS heterostructure carries deep red emission at 679 nm, with remarkably high photoluminescence quantum yield greater than 90%, longer carrier lifetime, and enhanced structural stability. The improved optical features and structural stability have been accredited to the complementary passivation of the halide vacancies and uncoordinated lead species of CsPbI₃ by the 0D Cs₄PbI₆/ZnS and the formation of PbS even at a relatively low synthesizing temperature. Thus, this proposed heterostructure has the potential to be used in different displays and medical applications.