Helical Carbon Nanotubes Research Articles

Research progress of fiber-shaped electrochemical energy storage devices

During the past two decades, wearable devices have been broadly used for a variety of fields such as biomedical system, communication and microelectronics. The power system such as lithium-ion batteries is essential to the operation of wearable devices, which should adapt to irregular substrates and sustain complex deformations. A promising strategy is to fabricate high-performance energy storage devices in a fiber shape, e.g., fiber lithium-ion batteries (LIBs). These fiber LIBs with diameters ranging from tens to hundreds of micrometers can be readily integrated with human body and work stably under constant body motions. They can also be woven into breathable fabrics to satisfy the needs of wearable electronics. The key challenges facing fiber LIBs include effective loading of active materials on fiber electrodes, efficient charge transfer along fiber electrodes and interface stability of fiber electrodes under operation and deformation. Fiber electrodes are thus designed with hierarchical and aligned channels to effectively load active materials, so an effective electric field can be established between the fiber cathode and anode. Aligned carbon nanotubes (CNTs) can be made with conductive additives and active materials into fiber electrodes by a continuous spinning process. Conventional metal current collectors, binders and conductive agents are not required, and active materials may reach 90% of the electrode by weight. The resulting hierarchically helical CNT fiber electrode shows high flexibility, high strength, and high electrical conductivity. The flexural rigidity is as low as 10−7 nN/m2, which is several orders of magnitude lower than those of ordinary synthetic fibers. The specific strength reaches 107 Nm/kg, which is higher than those of ordinary synthetic fibers. The conductivity reaches 104 S/cm, which can meet the needs of batteries. The aligned CNT composite fiber permits efficient electron transport, where the electrons hop among neighboring CNTs. Besides, due to the capillary force, the electrolyte can penetrate throughout the entire fiber via micrometer-sized and nanometer-sized channels, benefiting ion transport. The twisted CNT bundles firmly bind active materials and prevent their significant volume variations during charge and discharge processes. Therefore, the efficient conductive pathways can be maintained to deliver both high rate and cyclic stability. Fiber LIBs could be fabricated by assembling two fiber electrodes in parallel, twisting or coaxial structure. Gel electrolyte avoids the potential safety risks stemmed from liquid electrolytes. The continuously fiber LIBs show both high flexibility and energy storage capacity. After bending for 100000 cycles, the capacities have been well maintained, and the energy densities exceed 100 Wh/kg. Based on the similar strategy, a series of fiber energy storage devices such as supercapacitors, lithium-sulfur batteries, lithium-air batteries, zinc-ion batteries, zinc-air batteries and aluminum-air batteries, have been also produced. To summarize, fiber energy storage devices can be woven into flexible fabrics or integrated with energy harvesting devices to satisfy the next-generation electronics. Such a new strategy establishes an efficient avenue to particularly accelerate the development of wearable electronics in the future.

Molecular Dynamics Simulations of Twisting-Induced Helical Carbon Nanotube Fibers for Reinforced Nanocomposites

Carbon nanotube fibers have attracted much interest because of their outstanding multifunctional properties. In this work, double-helix carbon nanotube fibers (DHCNFs) assembled by combined self-twisting and whole-twisting processes are presented, and their mechanical properties were studied based on atomic simulation. We found that the self-twisting of carbon nanotubes (CNTs) can lead to interesting intertube entanglements, with the formation of a helical structure. In addition, the twisting process can cause a remarkable decline of the mechanical properties of CNTs owing to their hollow structure collapse, thus deteriorating the tensile mechanical performances of DHCNFs. Meanwhile, by tuning related twisting parameters, different fracture failure modes, including simultaneous and stepwise breakages, can be found. More importantly, it was revealed that, as nanoenhancements, the helical morphology of DHCNFs can effectively enhance the interlocking effect between CNTs and the matrix, thereby improving the interfacial strength and toughness of DHCNF-reinforced nanocomposites. This work systemically studied the effect of the twisting operation on the mechanical properties of DHCNFs and provided an innovative way of simultaneously enhancing the strength and toughness of CNT-based nanocomposites.

Directing helical CNT into chemically-etched micro-channels on aluminum substrate for strong adhesive bonding with carbon fiber composites

This study presents a simple technique for positioning helical carbon nanotubes (CNTs) into chemically-etched vertical micro-channels on an aluminum (Al) substrate for strong adhesive bonding with carbon fiber composites. Helical CNTs with diameter up to 100 nm and length up to 10 μm were dispersed evenly in an acetone-diluted resin pre-coating (RPC) solution consisting of 90 wt% acetone + 10 wt% resin (without hardener), then applied onto the chemically etched Al substrate with vertical micro-channels. CNTs were dragged into those vertical micro-cavities through the capillary action during the evaporation process of acetone. The shear bond strength was more than doubled by the quasi-Z-directional CNTs, confirming the critical role of CNT bridging across the interface between the epoxy adhesive and Al substrate. Scanned electron microscope (SEM) and focused ion beam (FIB) were used to reveal micro-channels on the Al substrate. RPC on the surface of carbon fiber composites is also beneficial.

Electromagnetic wave shielding/absorption performances of cementitious composites incorporating carbon nanotube metamaterial with helical chirality

Helical carbon nanotubes, a type of chiral metamaterial, were employed to investigate their effects as well as the mechanisms to electromagnetic wave shielding and absorption performances of cementitious composites over the frequency range from 2 GHz to 18 GHz. The results demonstrate that the best electromagnetic wave shielding effectiveness (SE) of cementitious composites filled with 7.5 wt.% helical carbon nanotubes is 1.39 times of that of cementitious composites without helical carbon nanotubes. The minimum reflectivity in 20 mm-thickness cementitious composites with 4.5 wt.% helical carbon nanotubes is 2.7 times of that of cementitious composites without helical carbon nanotubes. Cementitious composites with 7.5 wt.% helical carbon nanotubes have smallest matching thickness and the minimum reflectivity of −41.0 dB. By analyzing electromagnetic parameters and conductive mechanisms, it is found that helical carbon nanotubes mainly affect reflection loss ratio in electromagnetic wave shielding and the dielectric loss in electromagnetic wave absorption. Both parameters are attributed to the enhanced conductivity with the increase of helical carbon nanotubes. The percolation zone ranges from 1.5 wt.% to 7.5 wt.% for alternating current resistivity, with conductive path transferring from ion conduction to electron conduction as the content of helical carbon nanotubes increases. Additionally, incorporating helical carbon nanotubes essentially does not cause the decrease in compressive strength of cementitious composites. The results recommend that cementitious composites incorporating carbon nanotube metamaterial with helical chirality present high electromagnetic performances with satisfactory compressive strength.

A self-enhanced electrochemiluminescent ratiometric zearalenone immunoassay based on the use of helical carbon nanotubes.

A self-enhanced electrochemiluminescent ratiometric immunoassay for zearalenone is described. A system composed of N-aminobutyl-N-ethylisoluminol (ABEI) and glutathione (GSH) produces a strong electrochemiluminescence (ECL) at an applied potential of 0.8V, probably because of short electron transfer distance and reduced energy loss. The method also uses octahedral anatase mesocrystals (OAM) with a large specific surface facilitating immobilization of ABEI and GSH. Helical carbon nanotubes, possessing a large specific surface, superior mechanical stability, and excellent electrical conductivity which serve as a solid support, greatly enhanced the loading capacity for g-C3N4 nanosheets and horseradish peroxidase-labeled anti-antibody. The peroxidase accelerates the decomposition of H2O2 to produce reactive oxygen species (ROSs), amplifying the blue ECL of ABEI and the green ECL of g-C3N4. The ratiometric sandwich immunoassay (performed by the ratio of ECL intensity at - 1.3V and 0.8V) allows for sensitive and reliable determination of ZEN in awide linear range from 1.0 × 10-4ng/mL to 10ng/mL. The method was successfully applied to the analysis of corn hazelnut samples for ZEN. Graphical abstract Schematic presentation of a self-enhanced electrochemiluminescent ratiometric immunosensor based on octahedral anatase mesocrystals (OAM) supported ABEI-glutathione (GSH) and g-C3N4 functionalized helical carbon nanotubes (HCNT) for zearalenone (ZEN) determination.

Controllable Synthesis of Co@CoOx/Helical Nitrogen-Doped Carbon Nanotubes toward Oxygen Reduction Reaction as Binder-free Cathodes for Al-Air Batteries.

Efficient and stable electrocatalysts for oxygen reduction reaction and freestanding electrode structure were developed to reduce the use of polymer binders in the cathode of metal-air batteries. Considering the unique geometrical configurations of helical carbon nanotubes (CNTs) and improved properties compared with straight CNTs, we prepared high-purity Co@CoOx/helical nitrogen-doped carbon nanotubes (Co@CoOx/HNCNTs) on a carbon fiber paper by hydrothermal and single-step in situ chemical vapor deposition strategies. Under an optimized growth time (1 h), the synthesized Co@CoOx/HNCNTs provide richer edge defects and active sites and show prominent electrocatalytic performance toward oxygen reduction reaction (ORR) under alkaline media compared with Co@CoOx/HNCNTs-0.5 h and Co@CoOx/HNCNTs-2 h. The soft X-ray absorption spectroscopy technique is used to investigate the influences of different growth times on the electronic structure and local chemical configuration of Co@CoOx/HNCNTs. Furthermore, the Al-air coin cell employing Co@CoOx/HNCNTs-1 h as the binder-free cathode exhibits an open-circuit voltage of 1.48 V, a specific capacity of 367.31 mA h g-1 at the discharge current density of 1.0 mA cm-2, and a maximum power density (Pmax) of 3.86 mW cm-2, which are superior to those of Co@CoOx/HNCNTs-0.5 h and Co@CoOx/HNCNTs-2 h electrodes. This work provides valuable insights into the development of scalable binder-free cathodes, exploiting HNCNT composite materials with an outstanding electrocatalytic performance for ORR in Al-air systems.

Effects of Helical Carbon Nanotubes on Mechanical Performance of Laminated Composites and Bonded Joints

<div class="section abstract"><div class="htmlview paragraph">Most composite assemblies and structures generally fail due to weak interlaminar properties and poor performance of their bonded joints that are assembled together with an adhesive layer. Adhesive failure and cohesive failure are among the most commonly observed failure modes in composite bonded joint assemblies. These failure modes occur due to the lack of reinforcement within the adhesive layer in transverse direction. In addition, the laminated composites fail due to the same reason that is the lack of reinforcement through the thickness direction between the laminae. The overall performance of any composite structures and assemblies largely depends on the interlaminar properties and the performance of its bonded joints. Various techniques and processes were developed in recent years to improve mechanical performance of the composite structures and assemblies, one of which includes the use of nanoscale reinforcements in between the laminae and within the adhesive layer. However, most prior research has been focused on use of straight carbon nanotubes (CNTs) and other nanomaterials in particle forms. The goal of this research was to improve the properties of the adhesive film and the interfacial bonding effectiveness between the laminae. Because CNTs are inert in nature, their interaction with the resin and adhesive polymer molecules is very weak. In this research we have used CNTs with various geometrical configuration (straight and helical geometries) and various weight percentages as additional reinforcements. The objective was to investigate the effectiveness of helical geometries of the CNTs to form interlocking mechanisms with the resin and the traditional microfiber reinforcements to improve the overall performance of the composite structures and assemblies. Single lap joint test specimens and flexural test specimens were prepared based on the ASTM standard D5868-01 and ASTM standard D790 and then tested and analyzed. The experimental results showed that the samples with CNT reinforcements performed considerably better than neat epoxy samples. Among the two different CNT geometries, helical CNTs performed better than the straight CNTs.</div></div>

Novel helical carbon nanotubes-embedded reduced graphene oxide in three-dimensional architecture for high-performance flexible supercapacitors

The rapid development of flexible and portable electronics has brought great opportunities to develop flexible and lightweight energy-storage systems. Herein, a free-standing, mechanically flexible and binder-free three-dimensional (3D) sandwich-type network film electrode with reduced graphene oxide (RGO)-wrapped helical carbon nanotubes (HCNT) is designed and synthesized by a synergistic and applicable self-assembly strategy. HCNT in the composites serve as the inner skeleton, impede the stacking of RGO and enlarge the space between RGO effectively, which facilitate the creation of conductive 3D architectures and reinforce the structural stability. Moreover, the RGO coating and the voids are beneficial in improving electrochemical conductivity. As a result, the as-prepared RGO/HCNT electrodes show excellent electrochemical characteristics, yielding the specific capacitances of 336 F g−1 at a current density of 0.25 A g−1, and it offers the energy density of 7.5 Wh kg−1 with the corresponding power density of 100 W kg−1 as well as excellent cycling stability at approximately 89.5% capacitance retention exceeding 3000 cycles. The bending tests indicate that the flexible supercapacitors (SCs) can operate under different static bending angles, and the capacitance is hardly affected. The HCNT and corresponding flexible SCs are novel materials with potential applications in the next generation of wearable energy devices.

A photothermal assisted in situ signal-amplified electrochemical immunoassay based on multifunctional probe for detecting autoimmune hepatitis marker

Herein, a photothermal in-situ amplified electrochemical immunoassay based on multifunctional probe for detecting autoimmune hepatitis marker was constructed. The immunoassay followed a sandwich protocol, helical carbon nanotubes (HCNTs) and polyaniline (PANI) composite provided a desirable substrate for the immobilization of massive primary antibody (Ab1). Subsequently, the multifunctional probe, by utilizing Chitosan (CS) modified AgI nanohybrids (AgI NHs) labeled secondary antibody (Ab2), were simply designed for the first time. To be specific, AgI NHs were not only directly served as signal readout, but also as amplifier further enhanced electrochemical signal. Under the near-infrared (NIR) laser irradiation, electrochemical reaction was significantly accelerated on electrode in situ due to the extraordinary photothermal conversion capability of AgI NHs. Therefore, the evidently improved sensitivity together with enhanced signal-to-noise ratio of immunoassay was achieved in the short time by precise-controlling of NIR laser irradiation. Under the optimal conditions, the developed electrochemical immunoassay realized sensitive and specific detection of autoimmune hepatitis marker from 10−4 ng/mL to 1 ng/mL with low detection limit of 3.3 × 10-5 ng/mL. Importantly, this work provided a promising prospect for the application of photothermal effect coupled with electrochemical immunoassay and opened up a new pathway for signal amplification.

Ferroconcrete-Like Helical Carbon Nanotube/Reduced Graphene Oxide Heterostructure 3D Networks as Sulfur Hosts for High-Performance Li-S Batteries

A novel helical Carbon nanotubes (HCNT) network with a reduced graphene oxide (rGO) coating was designed and fabricated through a synergistic self-assembly and sulfuration strategy for use as an effective sulfur (S) host. A ferroconcrete frame structure with a hierarchical 3D nanostructure composed of 1D HCNT and 2D rGO nanosheets was obtained. The rGO wraps around the HCNT to form a heterostructure and provide an apparent coating that protects S. HCNT in the composite boost to create an 3D network architecture and reinforce the structural stability. Moreover, the heterostructures and rGO coatings, which are rich in wrinkles, can greatly minimize direct contact between the polysulfide and electrolyte, they also provide an abundance of active sites and boundary defects. Furthermore, the 3D interconnected structure creates effective ion diffusion channels and allows effective trapping of S and Li polysulfides. When used as a cathode, the HCNT/rGO/S cathode exhibits a high initial specific capacity of 1196 mAh g−1 at 0.1 C. The capacity decay rate of the HCNT/rGO/S is only 0.075% per cycle after cycling for 200 times at a rate of 0.1 C. This unique hybrid HCNT/rGO/S electrode design may motivate the development of other high-performance electrodes with excellent electrochemical properties.

Electrochemical Determination of Dopamine at Pre-Anodized Helical Multi-Walled Carbon Nanotubes Modified Glassy Carbon Electrode

In this article we electrochemically investigated the determination of dopamine (DA) at pre-anodized helical multi-walled carbon nanotubes (H-MWCNTs) modified glassy carbon electrode (GCE) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The pre-anodized H-MWCNTs/GCE could catalyze DA redox reaction greatly, and the oxidation current of DA from DPV measurement on pre-anodized H-MWCNTs/GCE was about 25 time bigger than on GCE. Furthermore, the pre-anodized H-MWCNTs/GCE could separate the oxidation peak potentials of DA, ascorbic acid (AA) and uric acid (UA) with well-defined peak separation as 164 mV for DA and UA, and 208 mV for DA and AA. The calibration curves of DA were obtained linearly in the range of 1 × 10−7 ∼ 2 × 10−6 M and 6 × 10−5 ∼ 2 × 10−4 M with the limit of detection (LOD, S/N = 3) and the limit of quantification (LOQ, S/N = 10) as 2.1 × 10−8 M and 7.0 × 10−8 M respectively. The sensor had been applied for DA measurement in dopamine injection samples with satisfactory results.

Label-Free Electrochemical Immunosensor Based on β-Cyclodextrin-Functionalized Helical Carbon Nanotube and Ionic Liquid Containing Ferrocene and Aldehyde Groups.

We fabricated an electrochemical immunosensor for the detection of cardiac troponin I using β-cyclodextrin-functionalized helical carbon nanotube and ionic liquid functionalized with ferrocene and aldehyde groups. β-Cyclodextrin-functionalized helical carbon nanotube was first modified on the electrode surface. Then, ferrocene- and aldehyde-functionalized ionic liquid was modified on the surface of the electrode through host–guest interaction, resulting in an interface with aldehyde groups. The aldehyde groups attached to the ionic liquid capture antibody directly, which simplifies the fabrication of immunosensor. Because of the use of ionic liquid and helical carbon nanotube, the conductivity of the sensing interface was improved. Thus, the sensitivity of the fabricated immunosensor was increased. The immunosensor for cardiac troponin I shows a linear range from 0.05 to 20 ng mL–1 with a detection limit of 0.04 ng mL–1 (S/N = 3).

Synthesis, characterization and cyclic voltammetry studies of helical carbon nanostructures produced by thermal decomposition of ethanol on Cu-foils

Cu-foils have been used intensively to fabricate graphene and other carbon nanostructures. Several routes have been implemented to improve the synthesis of such carbonaceous nanomaterials. We investigated the growth of carbon materials on Cu-foils by mapping the reactor in a chemical vapor deposition method. Several Cu-foils were pretreated by sonication to modify their surface and were placed alongside the reactor and exposed to a flow of ethanol vapor. After carbon materials deposition, the Cu-foils were analyzed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, and cyclic voltammetry (CV). It was demonstrated that the type of synthesized carbon nanostructure depends strongly on the position where the Cu-foils were placed. XRD characterizations revealed the presence of graphite materials, Cu, and CuO crystal structures. SEM characterizations revealed the presence of helical, herringbone and straight multiwalled carbon nanotubes with internal bamboo-shape morphology and formation of Cu nanoparticles. Important electrochemical properties of Cu-foils rich in helical carbon nanostructures were observed, suggesting this material can be used for redox reactions (RR) promotion. In addition, the hydrophobic properties were evaluated by contact angle measurements.

Molecular-dynamics study of the carbon nanotube mechanical metahelix

Hierarchical helical structures extensively exist in both natural and artificial systems and hold remarkable mechanical properties. Here, tensile mechanical properties of metahelix designed by twisting multiply twisted helical carbon nanotube ropes are investigated by coarse-grained molecular dynamic simulations. One-level metahelix are slightly mechanically strengthened with increasing twist angle α. However, two-level ones are more sensitive to the twist operation angles α and β, with maximum reduction in strength and Young's modulus by 64% and 87%, respectively. Three distinct failure modes are identified, although all metahelix show brittle failure under tension. For type I fracture mode, regardless the twist angle in metahelix, stress is uniformly distributed, resulting in simultaneous breakage of bonds at a cross-section. The type II and III failure modes are featured by stepwise localized failures, resulting from non-uniform stress distribution along each filament and identical cross-section of metahelix. This work provides molecular insights into optimal mechanical performance of CNT-based hierarchical helical yarns.

Wire electrochemical micromachining of Ni-based metallic glass using bipolar nanosecond pulses

The up-and-coming trend of product miniaturization alongwith application of novel materials with extreme properties has created a challenge for machining industry. Newly developed wire electrochemical micromachining (WECMM), as an important nontraditional micromachining technique, has been identified as a promising method for fabrication of microcomponents on a wide range of conductive materials. However, in many cases, the processing performance is typically limited by the properties of tool cathode and the mass transport rate in the interelectrode, which plays a crucial role in further development of this technique. Herein, the use of bipolar nanosecond pulses is innovatively proposed to help reduce the deposition of electrolysis products on the tool electrode and the underlying mechanism is systematically analyzed. Helical carbon nanotube fiber (CNF) was used as a new tool cathode in vibration-assisted WECMM to enhance the mass transport rate. The microshaping characteristics of the proposed method using bipolar nanosecond pulses were then investigated using a Ni-based metallic glass that exhibits typical passivation behavior in dilute acidic electrolytes as a representative example. Compared with traditional unipolar pulses, the use of bipolar pulses could effectively inhibit passive film growth on the machining surface of metallic glasses. In addition, no tool wear occurred for CNF that the original surface morphology became rougher only at excessive negative voltages. Finally, functional microcomponents were successfully fabricated with overall improved processing performance.

Label-Free Electrochemical Immunosensor Based on a Functionalized Ionic Liquid and Helical Carbon Nanotubes for the Determination of Cardiac Troponin I.

A label-free electrochemical immunosensor for cardiac troponin I was prepared by using a helical carbon nanotube-supported aldehyde-functionalized ionic liquid. Because of the good conductivity of ionic liquid and helical carbon nanotubes, high sensitivity of the immunosensor was obtained. Functionalized ionic liquid provided binding sites for antibody, which simplified the process of sensor construction. Cardiac troponin I was detected by this immunosensor with a linear range of 0.05–30 ng/mL and a detection limit of 0.03 ng/mL. The electrochemical immunosensor had satisfactory reproducibility, high sensitivity, and acceptable specificity.

(Invited) Synthesis of Helical-CNT and Stacked Graphene-CNF Using a Copper Foil As Catalyst in a Chemical Vapor Deposition System

Helical carbon nanotubes (H-CNT) and stacked graphene carbon nanofibers (SG-CNF) were synthesized in an aerosol assisted chemical vapor deposition system (AACVD) using a copper foil as catalyst and substrate and ethanol vaporized as precursor. The copper foils were cleaned and pre-treated with ethanol, isopropanol and acetone in sonication bath during one hour each to obtain a slight surface modification. The AACVD was carried in one tubular furnace at 980 °C where several copper foils of 0.25 mm thickness and 4 cm x 1 cm area were placed inside the reactor from the highest to the coolest temperature zone. This carbon nanostructures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, Raman spectroscopy, atomic force microscopy (AFM) and cyclic voltammetry using a Calomel electrode in a KCl 0.5 M solution as electrolyte. A variety of carbon morphologies were found passing from the growing of graphite at the highest temperature to the formation of the H-CNT and SG-CNF at the temperature dropping zone (figure 1a-1f). Migration of sharp copper nanoparticles (10 nm – 200 nm) was observed as copper nanoparticles were found at the surface covered by carbon materials, while as we go out the furnace, faceted copper nanoparticles are partially covered of graphitic materials. A diminution of the Cu(200) crystalline plane of the copper foil as the temperature decreases is visible and the formation of copper oxide at the farthest position play a significant role in the growing of the carbon nanostructures. The H-CNT are helical structures with no practically gap between each coil with a pitch of ~27 nm by a tubular structure with ~20 graphitic layer in each wall (figure 1g-1i), in the case of the SG-CNF the graphitic layers are almost perpendicular to the CNT axis similar to a stacked short graphene layers directed outwards the structure that leds to the edge formation. Raman characterization illustrates differences between the graphitic carbon structures found at early stages from those at the dropping temperature zone where at the higher temperature mainly graphite the relation of the ID/IG bands is 0.88, while for the H-CNT and SG-CNF the ID/IG relation is 1.79 indicative of high defective graphitic structure which is related with the “herringbone structure” of the SG-CNF, in the case of the coolest zone the Raman spectra is characteristic of low sp3 amorphous carbon (ID/IG of 0.67). The cyclic voltammetry results indicates that the sample with the H-CNT and SG-CNF structures becomes more capacitive in a cuasi-reversible process with practically no modification of the standard oxide-reduction potential for Cu, while for the other sections this oxide-reduction potential increases. Another aspect of the sample with the H-CNT and SG-CNF is its hydrophobic surface with a contact angle of 122 °. With this work we demonstrate that a light surface modification of the copper foil and the temperature profile inside the furnace has a high influence in the formation of the H-CNT and the SG-CNF, also the shape of the copper nanoparticle influence the type of carbon nanostructure catalyzed over the copper substrate. This material could be a good for oxide-reduction reactions. Figure 1

Narrowing Segments of Helical Carbon Nanotubes with Curved Aromatic Panels

AbstractRigid molecular cylinders with a 1 nm diameter were synthesized by assembling arylene panels with Pt‐mediated macrocylization. Chrysenylene panels that previously participated in tetrameric macrocyclization were contorted by the addition of two benzo groups on the sides to form dibenzochrysenylene, which allowed for a reduction in the numbers of participating panels to three. Consequently, narrowed cyclochrysenylene congeners were obtained. The narrowed chiral cylinders possessed width‐dependent chiroptical properties. The magnetic transition dipole moment was dictated by the radius of a ring‐current‐like circle that was formed by local electric transition dipole moments on the cylinder.

Narrowing Segments of Helical Carbon Nanotubes with Curved Aromatic Panels.

Rigid molecular cylinders with a 1 nm diameter were synthesized by assembling arylene panels with Pt-mediated macrocylization. Chrysenylene panels that previously participated in tetrameric macrocyclization were contorted by the addition of two benzo groups on the sides to form dibenzochrysenylene, which allowed for a reduction in the numbers of participating panels to three. Consequently, narrowed cyclochrysenylene congeners were obtained. The narrowed chiral cylinders possessed width-dependent chiroptical properties. The magnetic transition dipole moment was dictated by the radius of a ring-current-like circle that was formed by local electric transition dipole moments on the cylinder.

Tribological Properties of Molybdenum Disulfide and Helical Carbon Nanotube Modified Epoxy Resin.

In this study, epoxy resin (EP) composites were prepared by using molybdenum disulfide (MoS2) and helical carbon nanotubes (H-CNTs) as the antifriction and reinforcing phases, respectively. The effects of MoS2 and H-CNTs on the friction coefficient, wear amount, hardness, and elastic modulus of the composites were investigated. The tribological properties of the composites were tested using the UMT-3MT friction testing machine, non-contact three-dimensional surface profilometers, and nanoindenters. The analytical results showed that the friction coefficient of the composites initially decreased and then increased with the increase in the MoS2 content. The friction coefficient was the smallest when the MoS2 content in the EP was 6%, and the wear amount increased gradually. With the increasing content of H-CNTs, the friction coefficient of the composite material did not change significantly, although the wear amount decreased gradually. When the MoS2 and H-CNTs contents were 6% and 4%, respectively, the composite exhibited the minimum friction coefficient and a small amount of wear. Moreover, the addition of H-CNTs significantly enhanced the hardness and elastic modulus of the composites, which could be applied as materials in high-temperature and high-pressure environments where lubricants and greases do not work.