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Carbon nanotube reinforced polymer composites have been extensively researched [Shadler LS, Giannaris SC, Ajayan PM (1998) Appl Phys Lett 73:3842; Ajayan PM, Shadler LS, Giannaris C, Rubio A (2000) Adv Mater 12:750; Wagner HD, Lourie O, Feldman Y, Tenne R (1998) Appl Phys Lett 72:188; Thostenson ET, Chou T-W (2002) J Phys D: Appl Phys 35:L77] for their strength and stiffness properties. The interfaces between nanotubes and polymer matrix can play a critical role in nanocomposites for their mechanical properties, since the interfacial area is order of magnitude more than traditional composites. Unless the interface is carefully engineered, poor load transfer between individual nanotubes (in bundles) and between nanotubes and surrounding polymer chains may result in interfacial slippage [Shadler et al. (1998); Ajayan et al. (2000)] and consequently disappointing mechanical stiffness and strength. Interfacial slippage, while detrimental to high stiffness and strength, could result in very high mechanical damping, which is a hugely important attribute in many commercial applications. In this paper, we show that the mechanical damping is related to frictional energy dissipation during interfacial sliding at the extremely many nanotube-polymer interfaces, and characterize the impact of activation of the frictional sliding on damping behavior. [ABSTRACT FROM AUTHOR]

The article presents questions and answers related to carbon nanotube composites. One person asks the composition of carbon nanotubes which makes it special compared with other reinforcing fibres. Another questions the innovations which has been made to enhance the interfacial properties of nanotubes. A reader asks the applications by which nanotube composites could be used.

Due to their unique properties and potential uses in many fields, composite materials have attracted much attention and been extensively investigated. We have investigated the mechanical and dielectric properties of single-walled carbon nanotubes (SWCNTs)–reinforced poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) composite films. Composite films were prepared with SWCNTs concentrations ranging from 0.2 to 1.0% using a solution casting technique. Impedance spectroscopy was used to investigate the composite dielectric behavior, and tensile testing was performed to examine their mechanical properties. Field emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy were used for morphological analyses, and an X-ray diffractometer was used to determine the crystalline phase. The results showed that adding SWCNTs improved mechanical properties, including ultimate tensile strength (UTS) and elastic modulus (E). It also increased the dielectric constant. However, the dielectric loss also increased slightly. These enhancements can be attributed to the unique characteristics of the SWCNTs, such as their high aspect ratio and surface area. This research demonstrates the potential of PVDF-HFP/SWCNTs composites in various applications such as electronic devices, sensors, and capacitors. This study offers valuable insights for developing and designing composite films with improved properties for various applications. [ABSTRACT FROM AUTHOR]

Li-S batteries still suffer from two of the major challenges: polysulfide shuttle and low inherent conductivity of sulfur. Here, we report a facile way to develop a bifunctional separator coated with fluorinated multiwalled carbon nanotubes. Mild fluorination does not affect the inherent graphitic structure of carbon nanotubes as shown by transmission electron microscopy. Fluorinated carbon nanotubes show an improved capacity retention by trapping/repelling lithium polysulfides at the cathode, while simultaneously acting as the "second current collector". Moreover, reduced charge-transfer resistance and enhanced electrochemical performance at the cathode-separator interface result in a high gravimetric capacity of around 670 mAh g−1 at 4C. Unique chemical interactions between fluorine and carbon at the separator and the polysulfides, studied using DFT calculations, establish a new direction of utilizing highly electronegative fluorine moieties and absorption-based porous carbons for mitigation of polysulfide shuttle in Li-S batteries. [ABSTRACT FROM AUTHOR]

Efficient electrocatalysts are highly desirable for promising electrochemical reactions that are likely to mitigate the long‐standing energy and environment problems mainly resulting from human activities. However, most of them are partly composed by scarce and precious metals, thus hampering their large‐scale utilization. In this regard, developing efficient electrocatalysts with reduced noble metals loading or without noble metals is highly desirable. In the past decade, carbon nanotubes (CNTs)‐based electrocatalysts have proven to be efficient in many typical electrocatalytic reactions, and its strong structure operability and easy accessibility enable the utilization of related electrocatalysts to be sustainable. This review is aimed to summarize the research progress in CNTs‐based electrocatalysts, which are widely used in various electrochemical reactions. The major structure regulation approaches toward CNTs‐based electrocatalysts are highlighted. The primary functions of CNTs‐based electrocatalysts in electrochemical reactions are also highlighted here, together with the discussions on the support effect related to CNTs. Synchrotron‐based spectroscopies which can explore the intrinsic structure details that contribute to the performance enhancement and the electrochemical structure evolution of electrocatalysts under working conditions are also discussed. Finally, the challenges for shedding light on the very essence of the activity and the research perspectives are suggested. [ABSTRACT FROM AUTHOR]

Silicon carbide nanotube/nanowires (SiCNT/NWs) exhibit excellent mechanical properties in extreme thermal and oxidative environments. Here, we demonstrate an easily scalable process to synthesize millimeter-sized three-dimensional architectures using SiCNT/NW building blocks to create materials with excellent mechanical strength, stiffness, and resiliency with ultra-low density. The structure of these macro-materials is initially synthesized using carbon nanotubes, then utilizing the shape memory synthesis (SMS) method are converted to nano-silicon carbide. It is proposed that using this technique, any micro-structure can initially be created with nano-carbon building blocks, optimized for the necessary morphological features of a specific application. Here, the synthesis and subsequent SiCNT/NW conversion of carbon nanotube spheres and graphene foam, demonstrates the ability to use a simple, cost-effective conversion method to create a material that can mechanically perform in extreme environments. Image 1 [ABSTRACT FROM AUTHOR]

We report the observation of alternating current-to-direct current half-wave conversion in the range of 1–1000 Hz by single-wall carbon nanotube diode rectifiers, which show a high degree of rectification (∼105). The nanoscale diode rectifier demonstrates a half-wave power conversion efficiency of 20%, which is comparable to that reported for larger metal oxide semiconductor field effect transistor diode designs. [ABSTRACT FROM AUTHOR]

The interface thermal resistance (ITR) of the native interface between vertically aligned multiwalled carbon nanotube arrays and the SiO2/Si substrate was investigated. Experimental results obtained by a photothermoelectric technique are compared with theoretical predictions for the ITR across nanoconstrictions. The model considers classical constriction effects and contributions due to diffuse mismatch thermal resistance. Experimental values of the ITR are much larger than the model predictions. The observed discrepancy may be due to the imperfect mechanical contact between the tubes and substrate or additional contributions to the ITR due to the presence of a catalyst layer at the interface. [ABSTRACT FROM AUTHOR]

Graphical abstract Herein, we designed a strategy to successfully synthesize a novel bi-functional rambutan-like oxygen electrocatalysts comprising in situ -formed N-doped metal (metal: Fe, Co or Ni) encapsulated carbon nanotubes grown on hollow-mesoporous carbon sphere (denoted as Me@N-CNT/HMCS). Metal acetate can catalyze melamine to generate uniformly distributed N-CNTs nanotubes at the surface of hollow-mesoporous carbon sphere. The Me@N-CNT/HMCS oxygen electrocatalysts with very low metal content show unexpectedly high catalytic activities toward both ORR, which is superior to commercial Pt/C. Especially, the optimized performance of Fe@N-CNT/HMCS is achieved with more positive onset potential (E 0 = 1.012 V) and half-wave (E 1/2 = 0.833 V). Additionally, this result indicated that excellent performance is attributed to the synergistic effect involve chemical composition, good conductivity, high porosity and unique rambutan-like structure. Highlights • We firstly reported a simple strategy to successfully synthesize high-performance bi-functional electrocatalysts of the 1D-3D rambutan-like carbon materials. • The excellent electrocatalytic activity was assigned to the synergistic effect between N doping, metal loading and rambutan-like electrocatalyst morphology. • The theoretical calculation study suggests that metallic Fe cluster can promote the O 2 adsorption strength in such chemical environment. Abstract Electrocatalysis of oxygen reaction is a critical step in operation of fuel cells and metal-air batteries. For the practical applications, the inexpensive non-noble metals catalysts with highly activity and stable need to be explored and utilized. Herein, a strategy for the preparation of a bi-functional rambutan shaped oxygen electrocatalyst is presented. The novel electrocatalyst is formed in situ with N doped carbon nanotubes grown on metal encapsulated hollow-mesoporous carbon sphere (Me@N-CNT/HMCS). The Me@N-CNT/HMCS oxygen electrocatalysts show high catalytic activities towards ORR, comparable to commercial Pt/C catalyst. The optimized performance of Fe@N-CNT/HMCS was achieved with a positive onset potential of 1.012 V and half-wave potential of 0.833 V. It is emphasized that Me@N-CNT/HMCS shows high stability and enhanced tolerance against methanol in alkaline medium. The Fe@N-CNT/HMCS electrocatalyst possessed a high OER activity with a low overpotential of 0.35 V at 10 mA cm−2 current density. The excellent performance could be attributed to the synergistic effect involving chemical composition, high conductivity, good porosity and unique rambutan-like structure. In addition, the theoretical calculation study suggests that metallic Fe cluster can promote the O 2 adsorption strength in such chemical environment. [ABSTRACT FROM AUTHOR]

Abstract Herein, we report on a simple process, which is suitable for producing carbon nanotube micropatterns on steel alloys without the use of catalyst deposition. The method is based on a pulsed laser beam induced surface microstructuring process, followed by a thermal chemical vapor deposition growth of carbon nanotubes that emerge exclusively from the surface areas of the alloys previously exposed to the laser pulses. As concluded from X-ray diffraction, electron microscopy, Raman and X-ray photoelectron spectroscopy analyses of pristine and laser treated surfaces, the area-selective growth is caused by a formation of a thin and nanostructured metal oxide layer during the laser treatment, which is then partially reduced during the subsequent nanotube growth steps. The partially reduced oxide nanoparticles provide catalytic sites for nanotube growth and are also believed to disable diffusion of catalytic metal atoms to the subsurface regions, giving rise to stable catalyst nanoparticle formation and nanotube growth in the chemical vapor deposition step. The proposed method is fast, scalable and has potential for use in multiple applications that require close metal to nanotube contacts with arbitrary microscopic pattern definition on two and three-dimensional surfaces such as those used in electromechanical contacts, electrochemical electrodes, field emitters, and thermal interfaces. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Composite materials with carbon nanotube and graphene additives have long been considered as exciting prospects among nanotechnology applications. However, after nearly two decades of work in the area, questions remain about the practical impact of nanotube and graphene composites. This uncertainty stems from factors that include poor load transfer, interfacial engineering, dispersion, and viscosity-related issues that lead to processing challenges in such nanocomposites. Moreover, there has been little effort to identify selection rules for the use of nanotubes or graphene in composite matrices for specific applications. This review is a critical look at the status of composites for developing high-strength, low-density, high-conductivity materials with nanotubes or graphene. An outlook of the different approaches that can lead to practically useful nanotube and graphene composites is presented, pointing out the challenges and opportunities that exist in the field. [ABSTRACT FROM AUTHOR]

Abstract: Developing facile preparation routes and atomic‐level characterization methods for single‐atom catalysts is highly desirable but still challenging. Herein, a general strategy is proposed to construct transition metal single atoms within 1D and 2D carbon supports. The carbon supports, typically graphene and carbon nanotubes, are coated with various transition metal‐containing bimetal hydroxides, followed by polydopamine coating and high‐temperature pyrolysis. X‐ray absorption fine structure spectroscopy measurements and simulations efficiently indicate that single atoms (Co, Fe, or Cu) are captured within the applied carbon supports, distinctively forming exclusive molecule‐type sites. As a proof‐of‐concept application, the obtained catalysts exhibit remarkable performance for electrochemical oxygen reduction reaction, even surpassing commercial Pt/C catalyst. The developed versatile route opens up new avenues for the design of carbon‐based catalysts with definite molecular active sites. The atomic‐level structural identifications provide significant guidance for mechanistic studies toward single‐atom catalysts. [ABSTRACT FROM AUTHOR]

Owing to the weak physical interactions such as van der Waals and π-π interactions, which hold nanotubes together in carbon nanotube (CNT) bulk structures, the tubes can easily slide on each other. Creating covalent interconnection between individual carbon nanotube (CNT) structures could remarkably improve the properties of their three-dimensional (3D) bulk structures. The creation of such nanoengineered 3D solid structures with improved properties and low-density remains one of the fundamental challenges in real-world applications. Here, we report the scalable synthesis of low-density 3D macroscopic structure made of covalently interconnected nanotubes using free-radical polymerization method after functionalized CNTs with allylamine monomers. The resulted interconnected highly porous solid structure exhibits higher mechanical properties, larger surface area and greater porosity than non-crosslinked nanotube structures. To gain further insights into the deformation mechanisms of nanotubes, fully atomistic reactive molecular dynamics simulations are used. Here we demonstrate one such utility in CO 2 uptake, whose interconnected solid structure performed better than non-interconnected structures. [ABSTRACT FROM AUTHOR]

Understanding properties of individual nanostructures, such as mechanical properties and deformation mechanism, aid to control their properties for specific applications. Here we report, the mechanical properties of individual boron and nitrogen doped carbon-based nanospheres (CNS) using in-situ nano-compression testing in a scanning electron microscopy (SEM). The in-situ SEM characterizations showed classical sphere deformation during initial loading and it can be deformed till 40–50 percent. Elastic modulus of spheres is 33.3 GPa which has been determined using unloading curves. The mechanical properties of CNS structures are quite outstanding when it is compared to some other conventional nanomaterials such as polymer-based spheres and nanotube structures. [ABSTRACT FROM AUTHOR]

Here, we report similar reactions between nanotubes carrying functionalities, namely carbon nanotubes (CNTs) with the acyl chloride/hydroxyl and amine/carboxylic functionalities directly attached to their surfaces, resulting in the formation ofchemically modified graphene products. The reaction is spontaneous and is facilitated by simple grinding of the reactants. The new solid-state reactions have been confirmed using different spectroscopic and electron microscopy techniques. [ABSTRACT FROM AUTHOR]

Advanced composite materials are characterized by lightweight and unusually high stiffness, strength, modulus, etc. [1,2]. Their application field keeps on expanding as cheaper methods for synthesizing raw materials are found. Composite materials are now found in virtually all facets of applied materials [3]. Unlike a few decades ago when their application was limited to small parts; for example spoilers, failings, bonnets, etc., currently a new generation of airplane fuselage and wings are completely made of high-performance fiber reinforced composites [4–6]. The inherent high specific strength, low density, chemical and corrosion resistance [7] make them ideal for future applications. Typically, composite materials consist of a combination of two or more materials that are mixed with an aim of achieving a specific structural properties [8]. An effective composite should be able to optimize the properties of the individual components as one. [ABSTRACT FROM AUTHOR]

Here we report a unique method to locally determine the mechanical response of individual covalent junctions between carbon nanotubes (CNTs), in various configurations such as "X", "Y", and "Λ"-like. The setup is based on in situ indentation using a picoindenter integrated within a scanning electron microscope. This allows for precise mapping between junction geometry and mechanical behavior and uncovers geometry-regulated junction stiffening. Molecular dynamics simulations reveal that the dominant contribution to the nanoindentation response is due to the CNT walls stretching at the junction. Targeted synthesis of desired junction geometries can therefore provide a "structural alphabet" for construction of macroscopic CNT networks with tunable mechanical response. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanotubes (NCNTs) have been considered as a promising electrocatalyst for carbon-dioxide-reduction reactions, but two fundamental chemistry questions remain obscure: 1) What are the active centers with respect to various defect species and 2) what is the role of defect density on the selectivity of NCNTs? The aim of this work is to address these questions. The catalytic activity of NCNTs depends on the structural nature of nitrogen in CNTs and defect density. Comparing with pristine CNTs, the presence of graphitic and pyridinic nitrogen significantly decreases the overpotential (ca. −0.18 V) and increases the selectivity (ca. 80 %) towards the formation of CO. The experimental results are in congruent with DFT calculations, which show that pyridinic defects retain a lone pair of electrons that are capable of binding CO2. However, for graphitic-like nitrogen, electrons are located in the π* antibonding orbital, making them less accessible for CO2 binding. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon nanotubes (NCNTs) have been considered as a promising electrocatalyst for carbon-dioxide-reduction reactions, but two fundamental chemistry questions remain obscure: 1) What are the active centers with respect to various defect species and 2) what is the role of defect density on the selectivity of NCNTs? The aim of this work is to address these questions. The catalytic activity of NCNTs depends on the structural nature of nitrogen in CNTs and defect density. Comparing with pristine CNTs, the presence of graphitic and pyridinic nitrogen significantly decreases the overpotential (ca. −0.18 V) and increases the selectivity (ca. 80 %) towards the formation of CO. The experimental results are in congruent with DFT calculations, which show that pyridinic defects retain a lone pair of electrons that are capable of binding CO2. However, for graphitic-like nitrogen, electrons are located in the π* antibonding orbital, making them less accessible for CO2 binding. [ABSTRACT FROM AUTHOR]

Herein, we developed a strategy for fabrication of iron oxide infiltrated vertically aligned multiwalled carbon nanotubes (MWCNT forest) sandwiched with reduced graphene oxide (rGO) sheets network for high performance electromagnetic interference (EMI) shielding application which offers a new avenue in this area. Such engineered sandwiched network exhibits enhanced shielding effectiveness compared to conventional EMI shielding materials. This network of exotic carbons demonstrates the shielding effectiveness value more than 37 dB (>99.98% attenuation) in Ku-band (12.4–18 GHz), which is greater than the recommended limit (∼30 dB) for techno-commercial applications. [ABSTRACT FROM AUTHOR]

Although Li-oxygen batteries offer extremely high theoretical specific energy, their practical application still faces critical challenges. One of the main obstacles is the high charge overpotential caused by sluggish kinetics of charge transfer that is closely related to the morphology of discharge products and their distribution on the cathode. Here, a series of noble metal nanoparticles (Pd, Pt, Ru and Au) are encapsulated inside end-opened carbon nanotubes (CNTs) by wet impregnation followed by thermal annealing. The resultant cathode materials exhibit a dramatic reduction of charge overpotentials compared to their counterparts with nanoparticles supported on CNT surface. Notably, the charge overpotential can be as low as 0.3 V when CNT-encapsulated Pd nanoparticles are used on the cathode. The cathode also shows good stability during discharge-charge cycling. Density functional theory (DFT) calculations reveal that encapsulation of 'guest' noble metal nanoparticles in 'host' CNTs is able to strengthen the electron density on CNT surfaces, and to avoid the regional enrichment of electron density caused by the direct exposure of nanoparticles on CNT surface. These unique properties ensure the uniform coverage of Li2O2 nanocrystals on CNT surfaces instead of localized distribution of Li2O2 aggregation, thus providing efficient charge transfer for the decomposition of Li2O2. [ABSTRACT FROM AUTHOR]

Aligned carbon nanotube (CNT) forests filled with a dehydrated polymer electrolyte are used to fabricate flexible solid state supercapacitors (SSCs) for multifunctional structural-electronic applications. Local stiffness measurements on the composite electrodes determined through nano­indentation showed an 80% increase over the neat solid polymer electrolyte matrix. Electrochemical properties are monitored as a function of average tensile strain in the SSCs. Galvanostatic charge-discharge tests with in situ microtensile testing on SSCs are used to show a 10% increase in the specific capacitance through the elastic region of the composite. The increase in capacitance is partly attributed to the enhanced double layer interaction that results from the partial alignment of the polymer electrolyte chains at the electrode-electrolyte interface. When soaked in 1 m sulfuric acid, the specific capacitance of the CNT-polymer electrolyte reached approximately 72 F g-1 at 60 °C. [ABSTRACT FROM AUTHOR]

In the pursuit of advanced polymer composites, nanoscale fillers have long been championed as promising candidates for structural reinforcement. Despite progress, questions remain as to how these diminutive fillers influence the distribution of stresses within the matrix and, in turn, influence bulk mechanical properties. The dynamic mechanical behavior of elastomer-impregnated forests of carbon nanotubes (CNTs) has revealed distinct orientation-dependent behavior that sheds light on these complicated interactions. When compressed along the axis of the fillers, the composite will mimic open-cell foams and exhibit strain softening for increasing amplitudes due to the collective Euler buckling of the slender nanotubes. In contrast, the same material will behave similarly to the neat polymer when compressed orthogonal to the alignment direction of the nanotubes. However, in this orientation the material is incapable of achieving the same ultimate compressive strain due to the role that the embedded nanotubes play in augmenting the effective cross-link density of the polymer network. Both of these responses are recoverable, robust, and show little dependency on the diameter and wall-number of the included CNTs. Such observations give insight into the mechanics of polymer/nanoparticle interactions in nanocomposite structures under strain, and the thoughtful control of such coordinated buckling behavior opens the possibility for the development of foam-like materials with large Poisson ratios. [ABSTRACT FROM AUTHOR]

Realization of advanced bio-interactive electronic devices requires mechanically compliant sensors with the ability to detect extremely large strain. Here, we design a new multifunctional carbon nanotube (CNT) based capacitive strain sensors which can detect strains up to 300% with excellent durability even after thousands of cycles. The CNT-based strain gauge devices exhibit deterministic and linear capacitive response throughout the whole strain range with a gauge factor very close to the predicted value (strictly 1), representing the highest sensitivity value. The strain tests reveal the presented strain gauge with excellent dynamic sensing ability without overshoot or relaxation, and ultrafast response at sub-second scale. Coupling these superior sensing capabilities to the high transparency, physical robustness and flexibility, we believe the designed stretchable multifunctional CNT-based strain gauge may have various potential applications in human friendly and wearable smart electronics, subsequently demonstrated by our prototypical data glove and respiration monitor. [ABSTRACT FROM AUTHOR]

Abstract: The iodide (I−)-triiodide ( ) redox pair was used as a model system to evaluate the potential catalytic activity of various carbon nanotubes. Aqueous solutions of hydroiodic acid were irradiated with ultraviolet light in the presence of single wall, multi-wall, boron-doped and nitrogen-doped multi-wall carbon nanotubes. The nitrogen-doped multi-wall carbon nanotubes showed significant catalytic activity in the generation of hydrogen triiodide, while the other carbon nanotubes studied inhibited the generation of hydrogen triiodide. The photoconversion of hydroiodic acid to hydrogen triiodide, catalyzed by the nitrogen-doped multi-wall carbon nanotubes, was further accelerated by the presence of dissolved oxygen, offering an additional decomposition pathway for hydroiodic acid. [Copyright &y& Elsevier]

Wereport the creation of carbon nanotube films from superacids by ascalable process, where film morphology is controlled by initial fluidphases. These films were formed by dip-coating biphasic (isotropic+ liquid crystalline) carbon nanotube (CNT) chlorosulfonic acid solutions.Chlorosulfonic acid has low volatility and is therefore removed bysolvent extraction instead of conventional drying processes. At intermediateconcentrations, the solutions contain liquid crystalline domains which stretch andalign streamwise during dip-coating. These elongated domains furtheract as “nucleating sites” for large, aligned whiskerlikecrystallites during subsequent solvent extraction. The final filmscontain highly aligned CNT crystallites embedded in a mesh of randomlyoriented CNTs. [ABSTRACT FROM AUTHOR]

Here, we design and develop high-power electric double-layercapacitors(EDLCs) using carbon-based three dimensional (3-D) hybrid nanostructuredelectrodes. 3-D hybrid nanostructured electrodes consisting of verticallyaligned carbon nanotubes (CNTs) on highly porous carbon nanocups (CNCs)were synthesized by a combination of anodization and chemical vapordeposition techniques. A 3-D electrode-based supercapacitor showedenhanced areal capacitance by accommodating more charges in a givenfootprint area than that of a conventional CNC-based device. [ABSTRACT FROM AUTHOR]

Abstract: To assess the effect of carbon nanotube (CNT) grafting on interfacial stress transfer in fiber composites, CNTs were grown upon individual carbon T-300 fibers by chemical vapor deposition. Continuously-monitored single fiber composite (SFC) fragmentation tests were performed on both pristine and CNT-decorated fibers embedded in epoxy. The critical fragment length, fiber tensile strength at critical length, and interfacial shear strength were evaluated. Despite the fiber strength degradation resulting from the harsh CNT growth conditions, the CNT-modified fibers lead to a twofold increase in interfacial shear strength which correlates with the nearly threefold increase in apparent fiber diameter resulting from CNT grafting. These observations corroborate recently published studies with other CNT-grafted fibers. An analysis of the relative contributions to the interfacial strength of the fiber diameter and strength due to surface treatment is presented. It is concluded that the common view whereby an experimentally observed shorter average fragment length leads to a stronger interfacial adhesion is not necessarily correct, if the treatment has changed the fiber tensile strength or its diameter. [Copyright &y& Elsevier]

A method for the preparation of highly oxidized nitrogen-doped carbon nanotubes (N-CNTs) from KMnO4 C H2SO4 solution is described. The atomic ratio of C=O in oxidized N-CNTs is as low as 1.2. The x-ray photoelectron spectroscopy results show that about 75% of the carbon atoms are oxidized and bound to oxygen-containing functional groups. The oxidation reaction mainly occurs at the outer sidewalls, which destroys the graphene stack to an sp3-rich structure and helps to preserve the tubular structure of the inner N-CNTs. The oxidized N-CNTs show an energy gap of 2.1 eV. [ABSTRACT FROM AUTHOR]

Abstract: The strain sensing and thermal–mechanical behaviors of well dispersed multi-walled carbon nanotube/polystyrene (MWCNT/PS) composite films with different wt.% of carbon nanotubes were analyzed. The thermal–mechanical properties are studied using a dynamical mechanical analyzer and the results give their storage modulus (E′) and loss modulus (E″) as a function of temperature. We found an increase in E′ of up to 122% at 80°C for a 6wt.% MWCNT/PS composite compared to PS. The glass transition temperature increased significantly with an increase in MWCNTs concentration. The strain sensing behavior of the films is measured by applying an axial load over film which is attached to a brass specimen. The composite films exhibit excellent strain sensing behavior for different MWCNT contents. The result shows that an electromechanical response of the composite films varies linearly with applied strain even at high strains. [Copyright &y& Elsevier]

Here we report a chemical-free, simple, and novel method in which a part from a silver-based anode is controllably used in a straightforward manner to produce silver nanoparticles (Ag NPs) in order to fabricate a controlled assembly of Ag NPs and single walled carbon nanotube (SWCNT) hybrid structures. The attachment and distribution of Ag NPs along SWCNTs have been investigated and characterized by field emission scanning electron microscopy (FESEM). We have achieved the decoration of SWCNTs with different densities of Ag NPs by changing the deposition time, the applied voltage, and the location of carbon nanotubes with respect to the anode. At low voltage, single silver nanoparticle is successfully attached at the open ends of SWCNTs whereas at high voltage, intermediate and full coverage densities of Ag NPs are observed. As voltage is further increased, fractals of Ag NPs along SWCNTs are observed. In addition, a device based on a Ag NPs-SWNT hybrid structure is used for the label-free detection of ssDNA molecules immobilized on it. We believe that the proposed method can be used to decorate and/or assemble metal nanoparticles or fractal patterns along SWCNTs with different novel metals such as gold, silver, and copper and can be exploited in various sensitive applications for fundamental research and nanotechnology. [ABSTRACT FROM AUTHOR]

Abstract: A weak interaction between carbon nanotubes (CNTs) and polymers was found to reduce polymer-wrapping on CNT surface, decrease the contact resistance between CNTs, and increase the electrical conductivity of their composites. Thermodynamic properties such as surface energy of components, filler–polymer interactions, and wettability of carbon/polymer systems were analyzed. It was found that the graphitized CNTs filled polyoxymethylene (POM) system exhibits the weakest CNT–polymer interaction among all the investigated systems and a poor wettability. Consequently, the graphitized CNT/POM composites possess a high electrical conductivity and a low percolation threshold of 0.5wt.% CNT loading, which is associated with the weak CNT–polymer interaction, low contact resistance between CNTs, good connectivity of CNT networks, and high crystallinity of POM in the composites. The results obtained imply that high-performance composites with optimal CNT-network structures can be designed and fabricated by fully considering the surface properties of components and CNT–polymer interactions. [Copyright &y& Elsevier]

Nowadays gas detection in the ppm and sub-ppm domain is essential in terms of environmental protection as well as reducing sanitary risks. However, detecting systems to perform these measurements (e.g., gas chromatographs) are expensive and take up too much space, thus their use is not likely to become wide-spread. Small, cheap and easily mountable sensors, such as resistive sensors are more applicable for this purpose. But the main disadvantage of these sensors is the lack of chemical selectivity. Yet, a novel method called fluctuation-enhanced sensing (FES), which considers the sensor noise as the source of chemical information, can be used to improve selectivity. Since carbon nanotube (CNT)-based sensors are regarded as promising devices for FES measurements, we investigated whether stationary fluctuations in output signal (dc-resistance) of a CNT sensor could be used to increase chemical selectivity. In this work we prove that FES is applicable to increase selectivity of CNT sensors: air polluting gases (N2O, NH3 and H2S) and their mixtures can be distinguished. Furthermore, we also show that different concentrations of the same analyte can be differentiated and chemical selectivity can be extended into the sub-ppm region. [ABSTRACT FROM AUTHOR]

Abstract: We present a detailed investigation of the formation of stable catalyst particles on Inconel substrates, an important step in the growth mechanism of carbon nanotubes on these substrates. The chemical nature of the interaction of catalyst and substrate was investigated using XPS, high-resolution cross-sectional TEM, and EDS studies. The results indicate that Cr2O3, an electrically conductive oxide, plays an important role in stabilizing nanoclusters of Fe catalyst under typical growth conditions. The nature of growth on a number of other superalloys is also presented and is examined with respect to their chemical composition. [Copyright &y& Elsevier]

There is strong recent interest in ultrathin, flexible, safe energy storage devices to meet the various design and power needs of modern gadgets. To build such fully flexible and robust electrochemical devices, multiple components with specific electrochemical and interfacial properties need to be integrated into single units. Here we show that these basic components, the electrode, separator, and electrolyte, can all be integrated into single contiguous nanocomposite units that can serve as building blocks for a variety of thin mechanically flexible energy storage devices. Nanoporous cellulose paper embedded with aligned carbon nanotube electrode and electrolyte constitutes the basic unit. The units are used to build various flexible supercapacitor, battery, hybrid, and dual-storage battery-in-supercapacitor devices. The thin free- standing nanocomposite paper devices offer complete mechanical flexibility during operation. The supercapacitors operate with electrolytes including aqueous solvents, room temperature ionic liquids, and bioelectrolytes and over record temperature ranges. These easy-to-assemble integrated nanocomposite energy-storage systems could provide unprecedented design ingenuity for a variety of devices operating over a wide range of temperature and environmental conditions. [ABSTRACT FROM AUTHOR]

We have developed a synthetic gecko tape by transferring micropatterned carbon nanotube arrays onto flexible polymer tape based on the hierarchical structure found on the foot of a gecko lizard. The gecko tape can support a shear stress (36 N/cm²) nearly four times higher than the gecko foot and sticks to a variety of surfaces, including Teflon. Both the micrometer-size setae (replicated by nanotube bundles) and nanometer-size spatulas (individual nanotubes) are necessary to achieve macroscopic shear adhesion and to translate the weak van der Waals interactions into high shear forces. We have demonstrated for the first time a macro-scopic flexible patch that can be used repeatedly with peeling and adhesive properties better than the natural gecko foot. The carbon nanotube-based tape offers an excellent synthetic option as a dry conductive reversible adhesive in microelectronics, robotics, and space applications. [ABSTRACT FROM AUTHOR]

We show that electrostatic charging of nanotubes and the consequent repulsion can lead to reversible separation of individual single-walled carbon nanotubes in bundles. Low-energy electron beam irradiation leads to this completely reversible phenomenon. A simple semianalytical model is used to explain the observed separation mechanism. The reversibility of the separation process is attributed to discharging and thermal-fluctuation induced motion of the nanotubes in ambient air. Further, the separation impacts the electrical conductance of small nanotube bundled devices. [ABSTRACT FROM AUTHOR]

The article describes the formation of large area-aligned arrays from direct deposition of single-wall carbon nanotube inks. According to the authors, the water-based ink formulation relies on no covalent modification of the nanotubes and is one of the first to be applied to depositing conductive carbon nanotube networks. They add the one of the advantages is that over a given distance there will be less tube-tube junctions, reducing the impedance of the deposited material.

In an effort to combine group III–V semiconductors with carbon nanotubes, a simple solution-based technique for gallium functionalization of nitrogen-doped multi-wall carbon nanotubes has been developed. With an aqueous solution of a gallium salt (GaI3), it was possible to form covalent bonds between the Ga3+ ion and the nitrogen atoms of the doped carbon nanotubes to form a gallium nitride–carbon nanotube hybrid at room temperature. This functionalization was evaluated by x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy [ABSTRACT FROM AUTHOR]