Insertion Of Carbon Nanotubes Research Articles

Boosting hydrogen storage performance in COF-108 by single-walled carbon nanotube insertion, boron substitution, and lithium doping at room temperature

Boosting hydrogen storage performance in COF-108 by single-walled carbon nanotube insertion, boron substitution, and lithium doping at room temperature

Effect of Positively Charged Lipids (DOTAP) on the Insertion of Carbon Nanotubes into Liposomes and the Separation Performance of Thin-Film Nanocomposite Membranes

A liposome vesicle is an ideal carrier for carbon nanotubes (CNTs) serving as the water channel that allows for the fast transport of water molecules, thus enhancing membrane permeability. However, a low quantity of CNTs inserted into the liposome vesicle is an important factor that limits the further improvement of the membrane flux. In the present study, a positively charged lipid, (2,3-dioleoyloxy-propyl)-trimethylammonium-chloride (DOTAP), was introduced to 1,2-dioleoyl-sn-glycero-3-phosphoethanolamineon (DOPE) liposome vesicles to tailor the vesicle charge so as to evaluate the effect of positively charged DOTAP on the insertion of CNTs into liposomes and the separation performance of thin-film nanocomposite (TFN) membranes. The results show that the addition of DOTAP increased the quantity of CNTs inserted into the liposome vesicles, as the shrinkage rate (k) and permeability (Pf) of the liposome vesicles presented an obvious increase with the increased content of DOTAP in the liposome vesicles. Moreover, it contributed to a 252.3% higher water flux for TFN membranes containing DOPE/DOTAP2:1-CNT liposomes (the mass ratio between DOPE and DOTAP was 2:1) than thin-film composite (TFC) membranes. More importantly, it presented a 106.7% higher water flux for TFN membranes containing DOPE/DOTAP4:1-CNT liposomes (the mass ratio between DOPE and DOTAP was 4:1), which originated from the greater number of water channels that the CNTs provided in the liposome vesicles. Overall, positively charged DOTAP effectively tailored the vesicle charge, which provided a better carrier for the insertion of a greater quantity of CNTs and contributed to the higher permeability of the TFN membranes.

Reduction of Interlayer Interaction in Multilayer Stacking Graphene with Carbon Nanotube Insertion: Insights from Experiment and Simulation

Reduction of Interlayer Interaction in Multilayer Stacking Graphene with Carbon Nanotube Insertion: Insights from Experiment and Simulation

Effects of CNT microstructural characteristics on the interfacial enhancement mechanism of carbon fiber reinforced epoxy composites via molecular dynamics simulations

Numerous studies have concentrated on improving the mechanical properties of carbon fiber reinforced polymer composite (CFRP) through the modification of carbon fiber (CF) with carbon nanotubes (CNTs). However, most of them were confined to describing experimental phenomena. In this study, molecular dynamics (MD) simulation was used to systematically reveal the effect of CNT nanostructures on the interfacial reinforcement of CF/epoxy. An all-atom modeling method was used to provide a quantitative description of the CF-CNT/polymer interface characteristic structure. Computational results indicate that nanotubes can protect the intra- and intermolecular interactions of epoxy segments from being destroyed, thereby preventing the initiation and propagation of micro-defects during interfacial deterioration. The mechanical competition between the interface and polymer bulk leads to different failure mechanisms, and the strengthened interface region has fewer atoms leaving the equilibrium state during tensile deformation. The insertion of CNTs on the fiber surface, specifically increasing their length, diameter, distribution density, or orientation, can improve interfacial tensile strength (up to +62.11 %) and delay the detachment of epoxy molecules from the CF. Additionally, MD outcomes were verified by synthesizing CNTs onto CF using an electric field-assisted flame synthesis approach, leading to improvement in IFSS (+62.67 %) and ILSS (+27.78 %).

Super aligned carbon nanotubes for interfacial modification of hole transport layer in polymer solar cells

This work presents a facile and innovative method for the insertion of super aligned carbon nanotubes (CNTs) as sheets over and within poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as an efficient hole transport layer (HTL) in the inverted type polymer solar cell. CNTs sheets drawn from the vertically grown CNTs arrays were extracted via a sharp-edge blade and were directly transferred to the surface of PEDOT:PSS followed by the deposition of thermally evaporated silver electrode. All the characteristic photovoltaic parameters of the device have been improved with the insertion of special patterened CNTs sheets as compared to the standards device (without CNTs sheets). Power conversion efficiency (PCE) improved from 2.14% to 3.69% with the increased short circuit current density from 9.12 mAcm−2 to 11.58 mAcm−2 and fill factor from 0.48 to 0.58, respectively. Scanning electron microscopy (SEM) images revealed the successful insertion of CNTs without any destructive impact on the integrity of CNTs structure. Moreover, the performance and stability of the device have also been optimized by increasing the thickness of CNTs sheets. Electrochemical impedance spectroscopy (EIS) showed the reduction in charge transfer resistance on replacement of CNTs sheets-modified PEDOT:PSS as HTL as compared to simple PEDOT:PSS, which may be attributed to the creation of ordered steps which provided cascade routes for the better charge (holes) collection. Facile modification of the anode materials with improved device performance for designing of new device architecture will help scale-up production of low-cost, stable, and efficient polymer solar cells.

Mechanism of abrasion reduction in polydisperse system with carbon nanoparticles

The research is focused on the problem of abrasive wear. The authors proposed a model based on the adsorption theory, where abrasive particles are used as transport of nanoscale additive for lubricant. Laboratory tests have been performed to determine tribotechnical, physico-chemical and rheological properties of polydisperse suspensions. It was determined that the suspensions consisting of lubricant and carbon nanotubes have high stability when pretreated by ultrasound. Rheological tests performed by rotational viscometry indicated that the insertion of carbon nanotubes slightly increases the kinematic viscosity of the lubricants. Modification of liquid lubricants with multi-walled carbon nanotubes results in wear reduction of friction surfaces by up to 10%. The combined use of an abrasive contaminant increases the efficiency of the additive by up to 35%. Carbon nanotubes provide a shielding effect and reduce the cutting effect of abrasive particles. The analysis of temperature dependences obtained in the tribological experiments allowed us to conclude that modification of lubricants with carbon nanotubes can increase thermal conductivity of compositions, which contributes to effective heat transfer from the friction zone.

Structural and viscoelastic properties of floating monolayers of a pectinolytic enzyme and their influence on the catalytic properties

HypothesisThe catalytic activity of enzymes immobilized in self-assembly systems as Langmuir-Blodgett (LB) films is influenced by molecular interactions dictated by the composition and viscoelasticity of the previous floating monolayers. We believe that the insertion of carbon nanotubes (CNT) in mixed polygalacturonase/lipid monolayers may influence intermolecular interactions and viscoelastic properties, being then possible to tune system stability and rheological properties, driving catalytic properties of the films for biosensing. ExperimentsThe physicochemical properties of the monolayers were investigated by tensiometry, surface potential, Brewster angle microscopy, infrared spectroscopy, and dilatational rheology. The monolayers were transferred to solid supports LB films and characterized by atomic force microscopy, quartz crystal microbalance, and fluorescence spectroscopy. The catalytic activity of the LB films was verified by colorimetric assay. FindingsThe enzyme-CNT-lipid film had a catalytic activity at least twice as high as the pure enzyme owing to the synergy between the components, with the lipid acting as a protector matrix for the enzyme and the CNTs acting as an energy transfer facilitator. These results point to a proof-of-concept system, through which we can propose an alternative to achieve enhanced bio-inspired films with high control of the molecular architecture by using the LB approach.

Insertion of carbon nanotubes in Langmuir-Blodgett films of stearic acid and asparaginase enhancing the catalytic performance

In this paper, carbon nanotubes (CNT) were adsorbed on stearic acid (SA) Langmuir monolayers to serve as matrices for the incorporation of asparaginase. The interaction between the components at the air-water interface was evaluated by surface pressure-area isotherms, surface potential-area isotherms, polarization-modulation reflection absorption infrared spectroscopy (PM-IRRAS), and Brewster angle microscopy (BAM). The enzyme expanded the monolayers and changed the thermodynamic and electrical properties of the SA-CNT monolayers, as detected with the isotherms. PM-IRRAS spectra showed that the enzyme keeps its secondary structure when adsorbed at the monolayers and also alters the morphology of the air-water interface, as identified with BAM. The hybrid floating films were transferred to solid supports through the Langmuir-Blodgett (LB) technique, and the cotransfer of the enzyme was confirmed with fluorescence spectroscopy. The catalytic activity of asparaginase in the LB films was studied with UV–vis spectroscopy, which showed that the presence of CNT in the enzyme-lipid LB film not only tuned the catalytic activity, but also helped conserve its enzyme activity after weeks, showing higher persisting values of activity. UV–vis spectroscopy also showed that the catalytic activity is dependent basically on the enzyme molecules present on the surface of the LB films since multilayer films did not provide a proportional increase of enzyme activity. These results are related to the synergism between the compounds on the active layer, leading to a molecular architecture that allowed the adequate molecular accommodation of the analyte with the catalytic sites of the enzyme, which also preserved the asparaginase activity. This work then demonstrates the feasibility of employing LB films composed of fatty acids, CNT, and enzymes as devices for biosensing applications.

Lipid coating and end functionalization govern the formation and stability of transmembrane carbon nanotube porins

Carbon nanotube (CNT) based transmembrane porins have attracted a lot of recent interest due to their excellent transport properties for water, ions and biomolecules. In experiments, CNTs with a length of about 10 nm can penetrate and form stable transmembrane channels across lipid membranes, while in sharp contrast, similar 10 nm long pristine CNTs were found parallelly clamped inside the hydrophobic core of a lipid bilayer in simulations. This apparent paradox has motivated the present study, where we performed all-atom molecular dynamics simulations to show that lipid molecules initially coated on the CNTs play an essential role in the formation and stabilization of the CNT porins. We demonstrate that, as a lipid coated CNT is inserted into the membrane, lipid molecules arrange themselves into a bicelle on the CNT outside the membrane, providing mechanical support to stabilize the transmembrane configuration of the CNT porin. Further analysis shows that the lipid coating density and end-functionalization strongly influence the CNT insertion into a lipid membrane. These findings shed light on the mechanism of formation and stabilization of CNT porins and provide a theoretical basis to design related transmembrane transport systems.

Nanoarchitectured Nitrogen-Doped Graphene/Carbon Nanotube as High Performance Electrodes for Solid State Supercapacitors, Capacitive Deionization, Li-Ion Battery, and Metal-Free Bifunctional Electrocatalysis

A three-dimensional nanostructured nitrogen-doped graphene/carbon nanotube composite has been synthesized via a thermal annealing process, using the high surface attachment properties of uric acid (solid nitrogen precursor) with graphene oxide and oxidized multiwalled carbon nanotube. In the synthesis procedures, the attachment of uric acid to graphene oxide surfaces and the oxidized multiwalled carbon nanotubes via hydrogen bonding and electrostatic forces in the solution leads to a lamellar nanostructure during thermal annealing by the proper insertion of carbon nanotubes in graphene layers with nitrogen doping. The resultant composite has good atomic percentage of N (11.2 at. %) and shows superior electrochemical energy storage and conversion properties compared with nitrogen-doped graphene only and physically mixed nitrogen-doped graphene and nitrogen-doped carbon nanotube samples. The composite exhibits high gravimetric and volumetric capacitance (324 F g–1 at a current density of 1 A g–1) as electrode in solid-state supercapacitors, superior capacitive deionization (440 F g–1 at a current density of 1 A g–1) in 1 M sodium chloride solution, and as high-performance anode in lithium-ion batteries (1150 mAh g–1 at 0.1 A g–1) with long-term cycling stability. In addition, the composite demonstrates efficient metal-free bifunctional electrocatalysis toward the oxygen reduction and evolution reactions, comparable with the commercial electrocatalysts.

Enhancement of thermoelectric figure of merit by the insertion of multi-walled carbon nanotubes in α-MgAgSb

Hybrid materials provide an efficient alternative route on improving the thermoelectric performance compared with doping elements. Especially, the insertion of carbon nanotubes plays an effective role in modulating the electrical transport properties and phonon scattering simultaneously. We fabricated a multi-walled carbon nanotube (MWCNTs) doped α-MgAgSb-based hybrid material and researched its thermoelectric properties in detail. The introduced MWCNTs enhanced carrier transport due to the metallic character of MWCNTs and phonon dispersion by the additional interfaces of insertions. The results showed that the electrical conductivity in α-MgAgSb/CNTs was remarkably enhanced especially at MgAg0.97Sb0.99/0.15 wt. % CNTs boosting to 1.6 times than that of CNTs-free MgAg0.97Sb0.99. In addition, the thermal conductivity(κ0.1) of MgAg0.97Sb0.99/0.1 wt. % CNTs was reduced to 0.85 κ0. As a result, the ZT value at room temperature was efficiently improved from 0.55 to 0.83, 1.5 times higher, and a high ZT value of 1.05 at 375 K was obtained. In addition, the dimensionless material factor B* increased from 0.98 to 1.49 at the doping level of 0.1 wt. % CNTs at 300 K, which revealed that MWCNTs significantly enhanced the thermoelectric performance of α-MgAgSb.

In-situ insertion of carbon nanotubes into metal-organic frameworks-derived α-Fe2O3 polyhedrons for highly sensitive electrochemical detection of nitrite

Achieving highly sensitive electrochemical detection of nitrite for the control of nitrite contamination is a constant challenge, therefore, exploring hierarchical nanostructured materials for electrochemical detection with high activity is a vital importance. In the present study, we prepared the highly ordered MOFs-derived α-Fe2O3/CNTs hybrids through in-situ insertion of carbon nanotubes into MIL-101 (Fe) and their subsequent calcination for electrochemical detection of nitrite. MOFs-derived α-Fe2O3 polyhedrons are attached on the surface of CNTs tightly, forming hierarchical hybrids with interconnected building blocks. The in-situ insertion of CNTs in the novel hybrids shortens the electron-transfer distance between the α-Fe2O3 and CNTs, which makes α-Fe2O3 become highly active for oxidation of nitrite. The prepared sensor demonstrated excellent performances of nitrite detection with the limit of detection (LOD) as low as 0.15 μM, the high sensitivity of 334 μA mM−1 cm−2 and the wide linear range from 0.5 μM to 4000 μM. What's more, the prepared sensor displayed the prominent reproducibility and superior stability with excellent anti-interference ability, and then was successfully applied for the detection of nitrite in Tap water and Pond water.

Beyond the dimensional limitation in bio-inspired composite: Insertion of carbon nanotubes induced laminated Cu composite and the simultaneously enhanced strength and toughness

Metal/reinforcement nanolayered composites can effectively balance the strength and toughness. However, the difficulty of inserting nanoscaled metal layers restricts their practical application. In this study, laminated carbon nanotubes (CNTs) reinforced Cu composites with microscaled metal layered were fabricated by a feasible method and exhibited simultaneously enhanced strength and toughness. CNTs were deposited on Cu foils by electrophoretic deposition with two-dimensional homogeneous dispersion. Insertion of CNTs induced the laminated Cu composite with repeated layer spacing of ∼20 μm through hot pressing and hot rolling. Simultaneously enhanced yield strength (183 MPa) and elongation (30.9%) were obtained with only 0.067 vol% CNTs. The strength improvement reached far beyond the mixture rule in metal matrix composites (MMCs) with homogeneous CNTs dispersion. CNTs and the induced interfaces serve as effective dislocations motion barriers and strengthen the composite. Laminated composite exhibited more stable deformation due to suppressed strain location by the layered structure. This work highlights the strengthening and toughening effects of laminated structure induced by CNTs, and provides a feasible method to build the laminated MMCs with adjustable metal layer thickness and CNTs amount, thus breaking the dimensional limit of metal layers in the design of laminated MMCs with enhanced mechanical properties.

The Effect of CNTs on Performance Improvement of rGO Supported Fe-Nx/C Electrocatalysts for the Oxygen Reduction Reaction

As a widely investigated category of non-precious metal electrocatalysts for the oxygen reduction reaction (ORR), metal-Nx-C materials are gaining increasing attention both in the rational synthesis of catalysts and in the study of structure-activity relationships. Carbon supports are important to the performance of these catalysts toward the ORR. Graphene has been used in many electrocatalysts due to its notable characteristics, such as large specific surface area, and high conductivity, but it is further limited by the tendency to agglomerate. Here, carbon nanotubes (CNTs) were employed to effectively suppress the agglomeration of graphene. The binary carbon complex was loaded with iron phthalocyanine (FePc), achieving better activity than commercialized Pt/C (30 wt%) with a positive shift of half-wave potential of 20 mV after heat-treatment at 750°C. SEM, TEM, XPS and XAS measurements revealed that the insertion of CNTs not only suppressed the stacking of graphene layers, but also enhanced the catalytic performance during the RRDE and Zn-air battery tests in alkaline electrolyte by exposing more ORR active sites in the Fe-Nx structure.

Lightning Strike Simulation in Composite Structures

Lighting strike is one of the critical threats to the safety of composite aircrafts during flight. This work reports on numerical simulation of lightning strike in composite structures. Different modelling techniques using the commercial software ABAQUS, together with damage models are studied to find the most appropriate one in comparison to experimental results. Once the numerical model is validated, the effect of insertion of carbon nanotubes (CNTs) and metallic mesh in the composite is investigated. It is concluded that inserting CNTs in the top layer of the composite can improve its lightning strike protection noticeably.

REDUCTION OF FRICTION LOSSES DUE TO THE VORTEX FLOW OF THE MAGNETIC FLUID CAUSED BY THE ADDITIVES OF CARBON NANOTUBES

Magnetic fluids are promising lubricating material, in particular, in sliding bearings. With the aid of the magnetic system the magnetic fluid is held in the gap of friction that simplifies the design of the lubrication system sufficiently. It is known that when conventional lubricants (mineral oil, water) flow, with increasing of speed of rotation of the inner cylinder the transition of laminar flow in a vortex takes place. This dramatically increases the viscous friction losses. The friction losses in a wide range of speeds and possibilities of their decrease due to the vortex flow of the magnetic fluid in the gap between the cylinders are experimentally studied. It is revealed that when the dimensionless speed – number of Taylor equal to 41.2 – is reached, the slope of the curve of friction torque sharply increases, viscous losses also increase, i. e. there is a change laminar flow to a vortex one. The average temperature in the layer of the magnetic fluid reaches 60 оC. This factor leads to increased evaporation of the carrier liquid (water, mineral oil), which reduces the service life of the lubricant i.e. the magnetic fluid. In order to reduce viscous friction when a vortex flow of magnetic fluids takes place, carbon nanotubes, which are cylinders with a diameter of 5.0 nm and a length of about 0.1 mm, are brought into the magnetic fluid. Carbon nanotubes demonstrate elasticity under transverse bending: they curve under the impact of load, and after its removal they restore their original shape. They are also able to elongate along the axis by 16 % and to return to its original position after removal of the load. The effect of reducing friction (about 30 %) with a vortex flow of magnetic fluid by the introduction of carbon nanotubes in a magnetic fluid is experimentally obtained. The likely mechanism of friction reduction is the ability of nanotubes to deform under the influence of pressure pulsations and the velocity of the swirling flow, and to absorb partially a part of their energy. As it was experimentally demonstrated, there is an optimum weight concentration of the additive of nanotubes in the magnetic fluid (~10–4) that is associated with the maximum effect of reducing friction by 30 %. Thus, the insertion of carbon nanotubes in the lubricant (magnetic fluid) makes it possible to reduce the viscous friction and, consequently, to increase the range of operating speeds, to strengthen the online lubricant site.

Molecular Dynamics Study on Lipid Wrapped Carbon Nanotube as an Artificial Membrane Channel

Carbon nanotube (CNT) is an ideal membrane channel because of its hydrophobic inner pore and prominent transport properties like typical biological channels. These CNT porins can transport water, small ions, and DNA. CNT-membrane interaction simulation shows that CNTs having a length similar to the thickness of lipid bilayer can be inserted into membrane and sustain angle almost perpendicular to membrane. Much longer ones can also be inserted into membrane but they are buried inside hydrophobic region of membrane (1). However, recent experimental research elucidated that longer CNTs wrapped by lipids can be inserted into lipid-bilayer and maintain their angle within 15 degrees (2).In this study, we performed molecular dynamics simulation for investigating interaction between lipids wrapped CNT and lipid-bilayer. Martini coarse-grained force field was used to reduce computational cost significantly. Also, wrapping process was analyzed by using the coarse-grained carbon nanotube (CG-CNT) and the 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) in various CNT length and surface adsorption density, respectively. Furthermore, we performed insertion simulation to see how these properties affect insertion process and finally compared CG-CNT's insertion angles with experimental data. As a result, CNT insertion takes longer time in general as the density of wrapped lipid increases. Also, we realized that CNT can maintain its insertion angle almost perpendicular to lipid-bilayer at a certain critical density.Finally, its insertion mechanism is fully discussed with respect to interaction energy between the wrapped CG-CNT and lipid membrane.(1) Lelimousin, M., and M. S. P. Sansom. 2013. Small 9:3639-3646.(2) Geng, J., K. Kim, J. F. et al. 2014. Nature 514:612-+.

Mixed-mode fracture of sandwich composites: Performance improvement with multiwalled carbon nanotube sonicated resin

An experimental investigation on sandwich composite materials composed of glass-fiber face sheet and polyvinyl-chloride foam core has been carried out. The research demonstrates improvement in mixed-mode delamination fracture toughness values of samples under mixed-mode bending condition. The improvement is recorded with addition of a certain percentage by weight of multiwalled carbon nanotubes in comparison to conventional samples. An easy and cost-effective methodology of multiwalled carbon nanotube insertion through sonication of epoxy resin followed by mixing with hardener and vacuum resin infusion technology for manufacturing of sandwich composites has been utilized in this study. The study also identifies the optimum weight percentage of multiwalled carbon nanotube addition in the resin system for maximum performance gain in mixed-mode fracture toughness. The results of observations in this study have been supported by field emission scanning electron microscope studies as well as high-resolution transmission electron microscope analysis.

Charge-tunable insertion process of carbon nanotubes into DNA nanotubes

Control over interactions with biomolecules holds the key of the applications of carbon nanotubes (CNTs) in biotechnology. Here we report a molecule dynamics study on the encapsulation process of different charged CNTs into DNA nanotubes. Our results demonstrated that insertion process of CNTs into DNA nanotubes are charge-tunable. The positive charged CNTs could spontaneously encapsulate and confined in the hollow of DNA nanotubes under the combination of electrostatic and vdW interaction in our ns scale simulation. The conformation of DNA nanotubes is very stable even after the insertion of CNTs. For pristine CNTs, it could not entirely encapsulated by DNA nanotubes in simulation scale in this study. The encapsulation time of pristine CNTs into DNA nanotubes was estimated about 21.9s based on the potential of mean force along the reaction coordination of encapsulation process of CNTs into DNA nanotubes. In addition, the encapsulation process was also affected by the diameter of CNTs. These findings highlight the charge-tunable self-assembly process of nanomaterials and biomolecules. Our study suggests that the encapsulated CNTs-DNA nanotubes could be used as building blocks for constructing organic–inorganic hybrid materials and has the potential applications in the field of biosensor, drug delivery system and biomaterials etc.

Variation of Concrete Strength with the Insertion of Carbon Nanotubes

Nanomaterials could change the face of modern construction because they are more resistant, more durable and have notable features. Concrete is a material widely used in construction industry worldwide. Carbon nanotube has been considered a new and outstanding material in nanoscience field with great potential application in the construction industry. The study presented in this paper, aims at assessing how carbon nanotubes can affect cement composites and so the concrete, in terms of microstructure and physical-mechanical properties. Three different ratios of carbon nanotubes have been searched: 0.20%, 0.40% and 0.60%. To evaluate the mechanical properties of the samples, destructive and non-destructive tests were carried out to obtain compressive strength, tensile strength by diametrical compression, dynamic modulus of elasticity as well as the determination of their deformation properties. This work also aims to motivate entrepreneurs and professionals in the sector of civil engineering on the advantages of the application of nanotechnology in construction, as well as providing information to the scientific and technological community in general.