The composites of polyaniline with multiwall carbon nanotubes: Preparation,electrochemical properties,and conductivity

Composite materials based on the multiwall nanotubes (content in the material from 1 to 65 wt %) and polyaniline are prepared and characterized. The composite materials are prepared by four methods: chemical synthesis, electrochemical synthesis, mixing of dry components, and mixing of solutions with subsequent removal of solvent. The results of calculations of the specific capacity of the composite materials, as well as their conductivity, stability, and behavior under the conditions of charging-discharging point out to their applicability in devices for the energy storage. The range of critical changes in the values of specific capacity and conductivity falls into the interval of the multiwall nanotubes content in the composite from 5 to 25 wt %. The composite materials preparation methods used in this work enable one to choose an appropriate composite preparation method reasoning from the final purpose of its application (obtaining of high capacity or conductivity). The carbon nanotubes, the body of the composite, with their stable electronic conduction, can sustain the composite’s electrical conductivity at reasonable level irrespective of the properties of the second component (polyaniline) in the case in question.     

Formation of dispersed nanostructures from poly(ferrocenyldimethylsilane-b-dimethylsiloxane) nanotubes upon exposure to supercritical carbon dioxide

While incompatible block copolymers commonly assemble into several established classical or complex morphologies, highly asymmetric poly(ferrocenyldimethylsilane-b-dimethylsiloxane) (PFS-b-PDMS) diblock copolymers can also self-organize into high-aspect-ratio nanotubes with PDMS corona in the presence of PDMS-selective organic solvents. Exposure of these nanotubes on a carbon substrate to supercritical carbon dioxide (scCO2), also a PDMS-selective solvent, appears to promote partial dissolution of the copolymer molecules. At sufficiently high copolymer concentrations, the dissolved molecules subsequently re-organize within the scCO2 environment to form new copolymer nanostructures that redeposit on the substrate upon scCO2 depressurization. Transmission electron microscopy reveals that micelles form under all the conditions examined here, whereas nanotubes coalesce and vesicles develop only at relatively high temperatures. The extent to which the copolymer nanotubes dissolve and the size distribution of the replacement micelles are sensitive to exposure conditions. These results suggest that the phase behavior of PFS-b-PDMS diblock copolymers in scCO2 may be remarkably rich and easily tunable.     

Using the bending beam model to estimate the elasticity of diphenylalanine nanotubes

The core recognition motif of the amyloidogenic beta-amyloid polypeptide, diphenylalanine peptide, has previously been shown to self-assemble into discrete, well-ordered, stiff nanotubes under mild conditions. The nanotubes keep the same morphology from room temperature up to 100 degrees C. In the presented study, we applied the bending beam model to atomic force microscopy images of diphenylalanine nanotubes suspended across cavities and obtained the Young's modulus 27 +/- 4 GPa and the shear modulus 0.21 +/- 0.03 GPa. We also showed that the elasticity of these nanotubes is stable within the same temperature range and at relative humidity from 0% to 70%. This study furthers our understanding of the structure and properties of these nanotubes, which are important for their potential applications in biotechnology.     

Helical rosette nanotubes with tunable stability and hierarchy

The design of nanostructured materials with tunable dimensions and properties that maintain their structural integrity under physiological conditions is a major challenge in biomedical engineering and nanomedicine. Helical rosette nanotubes (HRN) are a new class of materials produced through a hierarchical self-assembly process of low molecular weight synthetic organic modules in water. Here, we describe a synthetic strategy to tune their stability and hierarchy by preorganization of the self-assembling units, control of net charge per unit of nanotube surface area, amphiphilicity, and number of H-bonds per self-assembling module, and through peripheral steric (de)compression. Using these criteria, HRNs with tunable stability and hierarchical architecture were produced from self-assembling modules that (a) persist as individual molecules in solution, (b) self-assemble into HRN but denature at high temperature (<85 degrees C), (c) self-assemble into HRN whose structural integrity persists even in boiling water (>95 degrees C), and (d) self-assemble into well-dispersed short nanotubes, long nanotubes, ribbons, or superhelices. Given the biocompatibility, synthetic accessibility, and chemical and physical tunability of these materials, numerous applications in biomedical engineering, materials science, and nanoscience and technology are envisioned.     

Dispersions, novel nanomaterial sensors and nanoconjugates based on carbon nanotubes

Nanomaterials are structures with dimensions characteristically much below 100 nm. The unique physical properties (e.g., conductivity, reactivity) have placed these nanomaterials in the forefront of emerging technologies. Significant enhancement of optical, mechanical, electrical, structural, and magnetic properties are commonly found through the use of novel nanomaterials. One of the most exciting classes of nanomaterials is represented by the carbon nanotubes. Carbon nanotubes, including single-wall carbon nanotubes, multi-wall carbon nanotubes, and concentric tubes have been shown to possess superior electronic, thermal, and mechanical properties to be attractive for a wide range of potential applications They sometimes bunch to form “ropes” and show great potential for use as highly sensitive electronic (bio)sensors due to the very small diameter, directly comparable to the size of single analyte molecules and that every single carbon atom is in direct contact with the environment, allowing optimal interaction with nearby molecules. Composite materials based on integration of carbon nanotubes and some other materials to possess properties of the individual components with a synergistic effect have gained growing interest. Materials for such purposes include conducting polymers, redox mediators and metal nanoparticles. These tubes provide the necessary building blocks for electronic circuits and afford new opportunities for chip miniaturization, which can dramatically improve the scaling prospects for the semiconductor technologies and the fabrication of devices, including field-effect transistors and sensors. Carbon nanotubes are one of the ideal materials for the preparation of nanoelectronic devices and nanosensors due to the unique electrical properties, outstanding electrocatalytic properties, high chemical stability and larger specific surface area of nanotubes. Carbon nanotubes are attractive material for supercapacitors due to their unique one-dimensional mesoporous structure, high specific surface area, low resistivity and good chemical stability. Nanoscaled composite materials based on carbon nanotubes have been broadly used due to their high chemical inertness, non-swelling effect, high purity and rigidity. The integration of carbon nanotubes with organics, biomaterials and metal nanoparticles has led to the development of new hybrid materials and sensors. Hybrid nanoscale materials are well established in various processes such as organic and inorganic compounds, nucleic acid detachment, protein separation, and immobilization of enzymes. Those nanostructures can be used as the building blocks for electronics and nanodevices because uniform organic and metal coatings with the small and monodisperse domain sizes are crucial to optimize nanoparticle conductivity and to detect changes in conductivity and absorption induced by analyte adsorption on these surfaces. The highly ordered assembly of zero-dimensional and one-dimensional nanoparticles is not only necessary for making functional devices, but also presents an opportunity to develop novel collective properties.     

Silicon- and carbon-based anode materials: Quantum-chemical modeling

With the aim of searching for promising anode materials for lithium-ion batteries, we performed quantum-chemical modeling of the structure, stability, and electronic properties of silicon-coated carbon nanotubes, silicon rods, and silicon carbide fibers by the density functional theory method including gradient correction and periodic boundary conditions. It has been demonstrated that nanotubes poorly hold silicon, whereas silicon firmly adheres to the SiC surface. Silicon rods are more favorable than clusters and have the stability close to that of the crystal. The band gap in the rods is close to zero. Silicon carbide can be transformed into a conductor by doping with nitrogen.     

Improved hydrothermal synthesis of MoS2 sheathed carbon nanotubes

MoS₂ sheathed carbon nanotubes have been successfully synthesized using a hydrothermal route under controlled conditions. The resultant material was studied by XRD, EDS, HRTEM, and Raman spectroscopy. Advantages of the preparation presented here compared to other methods are: a) lower reaction temperature, b) high yield of sheathed nanotubes including ends and full body, c) simple process with non-toxic materials, and d) no damage inflicted to nanotubes.     

Ionic liquids for soft functional materials with carbon nanotubes

A serendipitous finding that ionic liquids gel with carbon nanotubes has opened a new possibility of ionic liquids as modifiers for carbon nanotubes. Upon being ground into ionic liquids, carbon nanotube bundles are untangled, and the resultant fine bundles form a network structure. This is due to the possible specific interaction between the imidazolium ion component and the pi-electronic nanotube surface. The resultant gelatinous materials, consisting of highly electroconductive nanowires and fluid electrolytes, can be utilized for a wide variety of electrochemical applications, such as sensors, capacitors, and actuators. Ionic liquids allow for noncovalent and covalent modifications of carbon nanotubes and fabrication of polymer composites with enhanced physical properties. The processing of carbon nanotubes with ionic liquids is not accompanied by the disruption of the pi-conjugated nanotube structure and does not require solvents; therefore it can readily be scaled up. This article focuses on new aspects of ionic liquids for designer soft materials based on carbon nanotubes.     

Controlled assembly of carbon nanotubes by designed amphiphilic Peptide helices

Carbon nanotubes have properties potentially useful in diverse electrical and mechanical nanoscale devices and for making strong, light materials. However, carbon nanotubes are difficult to solubilize and organize into architectures necessary for many applications. In the present paper, we describe an amphiphilic alpha-helical peptide specifically designed not only to coat and solubilize carbon nanotubes, but also to control the assembly of the peptide-coated nanotubes into macromolecular structures through peptide-peptide interactions between adjacent peptide-wrapped nanotubes. The data presented herein show that the peptide folds into an amphiphilic alpha-helix in the presence of carbon nanotubes and disperses them in aqueous solution by noncovalent interactions with the nanotube surface. Electron microscopy and polarized Raman studies reveal that the peptide-coated nanotubes assemble into fibers with the nanotubes aligned along the fiber axis. Most importantly, the size and morphology of the fibers can be controlled by manipulating solution conditions that affect peptide-peptide interactions.     

Raman studies of hydrogen adsorbed on nanostructured porous materials

Raman spectroscopy was applied to study the adsorbed hydrogen phase in porous materials at room temperature and under cryogenic conditions. A comparison between the Raman spectra of H(2) molecules adsorbed on single walled carbon nanotubes and on a Cu-based metal-organic framework reveals that the interaction strength for the adsorption of molecular hydrogen is very similar in these materials. In both cases the small perturbation of the Raman spectrum of hydrogen indicates that adsorption takes place without any evident charge transfer between H(2) and the adsorbent. Additionally for single walled carbon nanotubes at least two types of adsorption sites could be identified by Raman spectroscopy.     

分子印迹SiO2纳米管膜的制备及其生化分离应用

分子印迹技术(M IT)是20世纪末出现的一种高选择性分离技术,由于M IT模仿了生物界的锁钥作用原理,使制备的材料(M IT polymer,M IP)具有极高的选择性.同时,M IP又是人工合成的高分子,具有非常好的稳定性,并且制备简单,因此在固相萃取、不对称催化和传感器等相关领域得到了广泛的应用[1～5].目前,M IT存在的主要问题是所制备的M IP对目标分子的结合量小,可接触性差,达到结合平衡的时间长,且在制备过程中所使用的印迹分子难以完全洗脱.     

Micelle-encapsulated carbon nanotubes: a route to nanotube composites

We report a general approach toward dispersing single-walled carbon nanotubes (SWNTs) in solvents and polymer materials, by encapsulating SWNTs within cross-linked micelles. Micelles made from polystyrene-block-poly(acrylic acid) (PS-b-PAA), an amphiphilic block copolymer, are first assembled around SWNTs by gradually adding H2O to a suspension of nanotubes in dimethylformamide. The hydrophilic, outer shells of these micelles are then chemically cross-linked with a difunctional linker molecule. Pure encapsulated SWNTs (e-SWNTs) can then be separated from empty cross-linked micelles by consecutive cycles of centrifugation and redispersion. Atomic force and transmission electron microscopies of the resulting nanostructures demonstrate that individual nanotubes (rather than bundles) have been completely encased in polymer shells whose thickness is slightly larger than that of empty micelles. e-SWNTs encapsulated in PS-b-PAA can be permanently redispersed in H2O, in organic solvents, and in both hydrophobic and hydrophilic polymer matrices with minimal sonication. Micelle encapsulation could improve the compositing of SWNTs in a wide variety of polymer materials for structural, electronic, and thermal applications.     

A sonochemical route to single-walled carbon nanotubes under ambient conditions

A chemical route to single-walled carbon nanotubes (SWCNTs) under ambient conditions has been developed. Silica powder was immersed in a mixture solution of ferrocene and p-xylene. After sonication at atmospheric pressure and room temperature, we obtained high-purity SWCNTs. Sonochemical effects may lead to producing high-purity SWCNTs. The process could be readily generalized to synthesize other forms of carbon-based materials, such as fullerenes, multiwalled nanotubes, carbon onions, and diamond, in liquid solution under ambient conditions.     

Unpredictable dispersion states of MWNTs in HDPE: A comparative and comprehensive study

A review of the literature indicates a wide range of dispersion states of carbon nanotubes (CNT) in high density polyethylene (HDPE), with in some cases, formation of micro-composites with bundle-like aggregation of the nanoparticles and in some others, much finer nanotube dispersion leading to higher performance (nano)composite materials. This contribution emphasizes the diversity of these results by comparing the dispersion state of different types of multiwall carbon nanotubes (MWNT) blended within several grades of HDPE via melt processing. It appears that each combination leads to a different dispersion quality. This study highlights that there is not a universal method to blend CNT and HDPE and that the dispersion state of the nanotubes is not readily predictable. Actually, inherent affinity between CNT and polyethylene proved to be rather great but melt viscosity and processing conditions represent key-parameters to be considered for allowing dissociation and dispersion of the nanoparticles within the polyolefinic matrix.     

Cu2SnSe3/CNTs Composite as a Promising Anode Material for Sodium-ion Batteries

Metal selenides as anode materials for sodium-ion batteries have attracted considerable attention owing to their high theoretical specific capacities and variable composition and structures.However,the achievement of long cycle life and superior rate performance is challenging for these selenide materials due to the volume variation upon cycling.Herein,a composite composed of a new binary-metal selenide[Cu2SnSe3(CSS)]and carbon nanotubes(CNTs)was constructed via a hydrothermal process followed by calcination at 600℃.Benefited from the unique structure of binary-metal selenide and the conductive network of CNTs,the Cu2SnSe3/carbon nanotubes(CSS/CNT)composite exhibits excellent electrochemical performance when used as an anode material for sodium-ion batteries.A reversible specific capacity of 399 mA·h/g can be maintained at a current density of 100 mA/g even after 100 cycles.This work provides a promising strategy for rational design of binary-metal selenides upon delicate crystal phase control as electrode materials.     

Conducting polypyrrole nanotubes: a review

Polypyrrole nanotubes rank among the most conducting polymer materials. The role of the templates in the formation of nanotubes is analysed and various models are discussed. Special attention has been paid to the role of methyl-orange dye in guiding one-dimensional morphology. The tuning of reaction conditions by varying temperature, acidity, or the introduction of additives, such as dyes, affects both the morphology and conductivity of polypyrrole. The increase in conductivity need not always be associated with nanotubular morphology. In addition to conductivity, also other physical properties are reviewed with the special attention paid to the characterization by UV–visible, infrared, and Raman spectroscopies. The chemical properties are demonstrated by the ability of polypyrrole to reduce noble-metal compounds, and by salt–base transition associated with the conductivity decrease. Polypyrrole nanotubes maintain the most of conductivity under physiological conditions, and they are still conducting under alkaline conditions in the contrast to globular polypyrrole. Polypyrrole nanotubes convert to nitrogen-containing carbon nanotubes at elevated temperature, thus producing useful carbonaceous materials. To improve the processing, the nanotubes have been used in composites, colloids, or hydrogels. The applications of polypyrrole nanotubes extend to adsorbents, actuators, antioxidants, biomedicine, catalysts and electrocatalysts, electrorheological suspensions, electromagnetic interference shielding, and sensors, especially to those exploiting electrical conductivity and electrochemical activity, such as electrodes in batteries and supercapacitors.     

碳纳米管/聚合物复合材料加工过程中原位取向方法与技术

碳纳米管具有优异的力学、电学等性能,但是在聚合物复合材料中的无规状态不能发挥出其自身的优异性能.本文从碳纳米管/聚合物复合材料的加工过程实现取向增强入手,结合自己的研究成果,综述了在外力、电场、磁场、液晶诱导等作用下制备取向碳纳米管/聚合物复合材料.可以看出,经过精心设计的力场、电场、磁场和液晶作用可以使碳纳米管在聚合物复合材料加工过程中取向,并进而提高了力学和电学性能,但取向程度均有待提高.     

Status of study on biological and toxicological effects of nanoscale materials

1 Introduction Undoubtedly, nanotechnology has already becomethe representative of leading new technologies in the21st century. It is expected not only to reform the tra-ditionally industrial techniques in the near future, suchas reducing the material con…     

Carbon nanotube mediated microscale membrane extraction

We demonstrate that functionalized carbon nanotubes can be readily immobilized into the pore structure of a polymeric membrane, which can dramatically improve its performance in analytical scale membrane extraction. This was accomplished by injecting an aqueous dispersion of the nanotubes through a polypropylene hollow fiber under pressure. The nanotubes were trapped and held within the pores and served as sorbents facilitating solute exchange from the donor to the acceptor phase. The effectiveness of this carbon nanotube mediated process was studied by direct solvent enrichment of nonpolar organics, and also by selective extraction of organic acids via a supported liquid membrane. In both cases, the enrichment factor measured as the ratio of concentrations in the acceptor to the donor phases could be increased by more than 200%.     

(n,m) Selectivity of single-walled carbon nanotubes by different carbon precursors on Co-Mo catalysts

Single walled carbon nanotubes (SWCNTs) were synthesized using four different carbon precursors including CO, C2H5OH, CH3OH, and C2H2 on Co-Mo catalysts. Semiconducting (n,m) abundance was evaluated by a method based on a single-particle tight-binding theoretical model taking into consideration the relative photoluminescence and absorption quantum efficiency for specific (n,m) tubes. (n,m) abundance determined in photoluminescence analysis was used to reconstruct the near-infrared Es11 absorption spectra. Carbon precursor pressure was found to be the key factor to the chirality control in this study. Narrowly (n,m) distributed SWCNTs can only be obtained under high-pressure CO or vacuumed C2H5OH and CH3OH. The majority of these nanotubes are predominately in the same higher chiral-angle region. The carbon precursor chemistry may also play an important role to obtain narrowly (n,m) distributed SWCNTs. (n,m) selectivity on Co-Mo catalysts shifts under different carbon precursors providing the route for (n,m) specific SWCNTs production.