Properties Of Single-walled Carbon Nanotubes Research Articles

(Invited) Nanocarbons for Multimodal Imaging, and Combination Multidrug/Gene Delivery

Carbon nanomaterials including single-walled carbon nanotubes (SWCNTs) and graphene derivatives serve as a basis of multiple molecular imaging and biological sensing device applications. However, those applications are still mainly centered on a single analyte sensing or the delivery of one particular therapeutic. Structure-dependent band gap configuration of SWCNTs was shown and that of graphene derivatives provides a promise of multiwavelength imaging in near-infrared or visible spectral regions. We utilize these structural characteristics of nanocarbons to provide multidrug delivery and/or multicolor imaging for complex medical conditions requiring combination therapies such as nonalcoholic steatohepatitis (NASH). It is so far, a non-curable condition present in 6-8% of adults in the US. The progression of NASH is mediated mainly via fibrosis and inflammation interlinked through the production of cytokines. The treatment of this complex condition requires targeting of several factors at once. We utilize (6,5) and (7,5) SWCNT samples chirality-separated by aqueous two-phase extraction for the delivery and drug-specific in-vitro imaging of drug and gene therapeutics targeting inflammation and fibrosis. These active agents, each bound non-covalently to SWCNT sample enriched in a specific chirality and purified from the sorting surfactants, are delivered to HepG2 cells and imaged via characteristic SWCNT emission in the near-IR. Hyperspectral microscopy imaging at select wavelengths corresponding to resonant transitions of (6,5) and (7,5) SWCNTs allows to preferentially track the presence of SWCNTs bound to each specific therapeutic. Furthermore, therapeutic effects of each formulation are assessed separately via protein and cytotoxicity assays allowing to utilize remarkable properties of SWCNTs for multimodal imaging and multidrug/gene delivery for NASH therapeutics. In addition to selective imaging by different SWCNT chiralities we explore multiwavelength biological imaging from the same nanomaterial produced through synthetic modification of nanoscale graphene derivatives and yielding dual-color green/near-IR emission. These fully biocompatible nanocarbons provide efficient internalization and in-vitro imaging in green (530 nm) with higher quantum yields and in near-IR (850 nm) water window region with decreased biological autofluorescence more optimal for ex-vivo and some in-vivo studies. Such new nanocarbon materials build a basis of multipurpose in-vitro/in-vivo multifunctional imaging/delivery agents.

(Invited) Endohedral Filling Effects for Single-Wall Carbon Nanotubes As a Function of Filler Molecule and Nanotube Size

Single-wall carbon nanotubes (SWCNTs) with open ends can be readily filled with a wide variety of organic molecules through simple liquid exposure. Ingestion of such molecules affects the extrinsic environment experienced by the SWCNT, and holds promise for controlled modulation of intrinsic SWCNT properties. To date optical linewidth narrowing, transition energy shifts and fluorescence enhancement as well as density modulation have been demonstrated. However, the dependencies of the properties on the filler molecule properties is observed to be non-uniform across filler and SWCNT (n,m) combinations. Of particular note is the combination of filler molecules and SWCNT structures of similar size, for which sieving and non-bulk arrangements of the filler molecules can be anticipated. Results in the small-diameter (n,m) SWCNT limit will be presented isolating the effects of filler insertion on the nanotube properties as a function of diameter, and implications for filling-based nanotube property manipulation.

Coherent anti-Stokes Raman scattering as an effective tool for visualization of single-wall carbon nanotubes.

Strong vibrational coherent anti-Stokes Raman scattering (CARS) signal was observed in single-wall carbon nanotubes (SWCNTs) having three different average diameters (about 0.8 nm, 1.1 nm and 1.3 nm) under optical excitation close to electronic resonance energies of nanotubes. By varying the excitation power from 1 up to 200 µW an optimal regime for non-destructive investigation of nonlinear properties of SWCNTs was determined. The possibility to detect a strong coherent nonlinear signal from small SWCNT-bundles together with CARS advantages over Raman scattering, such as high imaging rate, open new opportunities for fast three-dimensional visualisation of SWCNTs in a polymer matrix.

Free vibration of rotating pretwisted CNTs-reinforced shallow shells in thermal environment

ABSTRACTIn this paper, finite element method is employed to study the free vibration response of the rotating pretwisted carbon nanotube-reinforced composite cylindrical shell in thermal environment. The shells are reinforced by single walled carbon nanotubes (SWCNTs) and the material properties of SWCNTs are considered to be temperature dependent. The dynamic equilibrium equation is derived from Lagrange's equation for moderate rotational speeds for which the Coriolis effect is neglected. Parametric study is performed to investigate the effects of pretwist angles, temperature rise, rotational speed, and volume fraction of CNTs. In addition to this, the representative mode shapes are also presented.

Plasma enhanced chemical vapour deposition growth and physical properties of single-walled carbon nanotubes

Present work focuses on the growth of single-walled carbon nanotubes (SWCNTs) using nickel as a catalyst onto the silicon substrate through plasma enhanced chemical vapour deposition (PECVD) method. As synthesised SWCNTs have been characterized by employing various analytical techniques like XRD, SEM, HR-TEM/EDS and UV-visible absorption spectroscopy. The HRTEM micrographs revealed that the SWCNTs were mostly entangled bundles with diameters of about 2 nm. The optical absorption data were used to estimate energy bandgap of the SWCNTs and found to be 2.67 eV. The photocatalytic performance of the nanotubes was examined by the deterioration of an organic dye methylene blue (MB) under visible light irradiation. The observed results exhibit excellent photocatalytic activity of the nanotubes that may be due to the large surface defects, surface area and small energy bandgap characteristics of the nanotubes.

Excitons in Single-Walled Carbon Nanotubes and Their Dynamics.

Understanding exciton dynamics in single-walled carbon nanotubes (SWCNTs) is essential to unlocking the many potential applications of these materials. This review summarizes recent progress in understanding exciton photophysics and, in particular, exciton dynamics in SWCNTs. We outline the basic physical and electronic properties of SWCNTs, as well as bright and dark transitions within the framework of a strongly bound one-dimensional excitonic model. We discuss the many facets of ultrafast carrier dynamics in SWCNTs, including both single-exciton states (bright and dark) and multiple-exciton states. Photophysical properties that directly relate to excitons and their dynamics, including exciton diffusion lengths, chemical and structural defects, environmental effects, and photoluminescence photon statistics as observed through photon antibunching measurements, are also discussed. Finally, we identify a few key areas for advancing further research in the field of SWCNT excitons and photonics.

Carbon-Nanotube-Based Thermoelectric Materials and Devices.

Conversion of waste heat to voltage has the potential to significantly reduce the carbon footprint of a number of critical energy sectors, such as the transportation and electricity-generation sectors, and manufacturing processes. Thermal energy is also an abundant low-flux source that can be harnessed to power portable/wearable electronic devices and critical components in remote off-grid locations. As such, a number of different inorganic and organic materials are being explored for their potential in thermoelectric-energy-harvesting devices. Carbon-based thermoelectric materials are particularly attractive due to their use of nontoxic, abundant source-materials, their amenability to high-throughput solution-phase fabrication routes, and the high specific energy (i.e., W g-1 ) enabled by their low mass. Single-walled carbon nanotubes (SWCNTs) represent a unique 1D carbon allotrope with structural, electrical, and thermal properties that enable efficient thermoelectric-energy conversion. Here, the progress made toward understanding the fundamental thermoelectric properties of SWCNTs, nanotube-based composites, and thermoelectric devices prepared from these materials is reviewed in detail. This progress illuminates the tremendous potential that carbon-nanotube-based materials and composites have for producing high-performance next-generation devices for thermoelectric-energy harvesting.

Optically controlled dielectric properties of single-walled carbon nanotubes for terahertz wave applications.

Materials with tunable dielectric properties are valuable for a wide range of electronic devices, but are often lossy at terahertz frequencies. Here we experimentally report the tuning of the dielectric properties of single-walled carbon nanotubes under light illumination. The effect is demonstrated by measurements of impedance variations at low frequency as well as complex dielectric constant variations in the wide frequency range of 0.1-1 THz by time domain spectroscopy. We show that the dielectric constant is significantly modified for varying light intensities. The effect is also practically applied to phase shifters based on dielectric rod waveguides, loaded with carbon nanotube layers. The carbon nanotubes are used as tunable impedance surface controlled by light illumination, in the frequency range of 75-500 GHz. These results suggest that the effect of dielectric constant tuning with light, accompanied by low transmission losses of the carbon nanotube layer in such an ultra-wide band, may open up new directions for the design and fabrication of novel Terahertz and optoelectronic devices.

Влияние вакансионных дефектов на структурные свойства одностенных углеродных нанотрубок

Влияние вакансионных дефектов на структурные свойства одностенных углеродных нанотрубок

Control of near infrared photoluminescence properties of single-walled carbon nanotubes by functionalization with dendrons.

Single-walled carbon nanotubes (SWNTs) were functionalized by reacting them with sodium naphthalenide and dendrons to control their photoemission in the near-IR region. The functionalized SWNTs were characterized by absorption, Raman, and photoluminescence (PL) spectroscopy. The degree of functionalization of the SWNTs decreased with the increasing bulkiness of the dendrons used. After functionalization, new red-shifted PL peaks could be observed at ∼1110 and ∼1210 nm where the intensities were drastically enhanced by the thermal treatment. The relative peak intensity of to that of increased with the increasing bulkiness of the dendrons. Density functional theory (DFT) calculations of the functionalized SWNTs with dendrons suggest that the adducts with less bulky hydroalkylated substitution are stable in Clar structures and the addition positions predominantly determine the PL peak positions.

Studying The Influence of Various Geometrical Parameters of Single-Walled Carbon Nano-Tubes of ‎Armchair Chirality Type on Its Mechanical Behavior

In the present work, the profound information on the mechanical properties of carbon nano-tubes (CNTs) were presented as an application of nano-technology in nano-materials are being most powerful in the current world. This would focuses/emphasis for designing and optimizing the CNTs based materials. Computational modeling technique was applied and developed to examine the mechanical characteristics for single-walled carbon nano-tube (SWCNT) of armchair chirality type. The atomistic based finite element method (FEM) was used to investigate the influence of various geometrical properties (diameter, wall thickness, and height-to-diameter ratio) of SWCNT armchair of chirality type on Poisson’s ratio and Young’s modulus values. Atomistic based finite element modeling was successfully developed and explored the mechanical behaviour of SWCNT exactly. The results were shown that the investigated geometrical parameters had much influenced on the mechanical properties of SWCNTs.

Investigation of Physicochemical and Electrochemical Properties of Single-Walled Carbon Nanotubes Modified with Nitrogen

Composites of the type “nitrogen-containing carbon coating – single-walled carbon nanotubes” were obtained by the treatment of single-walled carbon nanotubes (SWCNT) in a gaseous 40%NH3-1%C2H2-C2H4 mixture at temperatures 600–750 °C. Single-walled carbon nanotubes etched in aqua regia (SWCNTet) and doped with nitrogen (N-SWCNT) were studied by XPS, electron microscopy and IR spectroscopy. Various oxygen-containing functional groups were found to reside on the surface of initial SWCNTet. Upon treatment of SWCNTet in 40%NH3-1%С2Н2-C2H4, polymerization and condensation of hydrocarbons resulted in the formation of a thin nitrogen-containing carbon coating. Specific capacitance per a weight of initial and nitrogen-doped carbon nanotubes in an aqueous electrolyte with 1 M H2SO4 was measured. Specific capacitance of carbon electrodes was found to change symbately with the content of nitrogen-containing functional groups on the SWCNT surface.

Synthesis of high growth rate SWCNTs and their magnetite cobalt sulfide nanohybrid as super-adsorbent for mercury removal

Water assisted synthesis of high quality and high yield single walled carbon nanotubes (SWCNTs) was performed over Co–Mo/MgO catalyst by chemical vapor deposition (CVD) method. The effect of varying the water amount on the yield and quality of SWCNTs was studied. The as-synthesized SWCMTs were employed for mercury adsorption from aqueous solution. Also, in order to improve the adsorption process, the two magnetite SWCNTs (MSWCNTs) and magnetite SWCNTs–CoS (MSWCNTs–CoS) nanohybrids were prepared. The XRD, TGA, FE-SEM, TEM, Raman, VSM and EDX analysis were carried out to study the effects of water vapor on quality, growth rate and yield of SWCNTs as well as to verify the nanohybrids structures. It was found that with increasing the water/methane up to 8% volume ratio, the quality and yield of nanotubes were reached to their maximum levels. However, more increasing the water vapor up to 20% caused dramatic decreases in the yield and quality. Mercury adsorption properties of SWCNTs, MSWCNTs and MSWCNTs-CoS were studied with the aid of response surface methodology (RSM). Kinetic, isotherm and thermodynamic studies revealed that MSWCNTs–CoS had a very high efficiency for mercury adsorption with a very much low equilibrium time (7min) indicating its super-adsorbent property.

Optothermally Reversible Carbon Nanotube-DNA Supramolecular Hybrid Hydrogels.

Supramolecular hydrogels (SMHs) are three-dimensional constructs wherein the majority of the volume is occupied by water. Since the bonding forces between the components of SMHs are noncovalent, SMH properties are often tunable, stimuli-responsive, and reversible, which enables applications including triggered drug release, sensing, and tissue engineering. Meanwhile, single-walled carbon nanotubes (SWCNTs) possess superlative electrical and thermal conductivities, high mechanical strength, and strong optical absorption at near-infrared wavelengths that have the potential to add unique functionality to SMHs. However, SWCNT-based SMHs have thus far not realized the potential of the optical properties of SWCNTs to enable reversible response to near-infrared irradiation. Here, we present a novel SMH architecture comprised solely of DNA and SWCNTs, wherein noncovalent interactions provide structural integrity without compromising the intrinsic properties of SWCNTs. The mechanical properties of these SMHs are readily tuned by varying the relative concentrations of DNA and SWCNTs, which varies the cross-linking density as shown by molecular dynamics simulations. Moreover, the SMH gelation transition is fully reversible and can be triggered by a change in temperature or near-infrared irradiation. This work explores a new regime for SMHs with potential utility for a range of applications including sensors, actuators, responsive substrates, and 3D printing.

Numerical analysis of the thermal and thermodynamic performance of a parabolic trough solar collector using SWCNTs-Therminol®VP-1 nanofluid

Abstract In this paper, energetic and exergetic performances of a parabolic trough solar collector using single-walled carbon nanotubes (SWCNTs)-Therminol® VP-1 nanofluid were numerically investigated and presented. The main objective of this investigation was to determine the influence of high thermal conductivity SWCNTs suspended in the widely used heat transfer fluid, Therminol®VP-1 on the performance indicators of the parabolic trough solar collector. A parabolic trough system with a high concentration ratio of 113 was analyzed in this study. The thermo-physical properties of SWCNTs were taken as functions of nanotube length, nanotube diameter, and temperature, while the properties of Therminol®VP-1 were considered to be temperature dependent. The study involved determination of the actual heat flux profile through Monte Carlo ray tracing and the subsequent coupling of this heat flux profile to a computational fluid dynamics tool using user defined functions. The computational fluid dynamics tool was finite volume based, and the realizable k-e model together with enhanced wall treatment were used for turbulence modeling. The entropy generation rates were obtained directly from the local velocity and temperature fields of the computed domain and later used in the exergy analysis. Results showed that although the heat transfer performance significantly improved with the use of SWCNTs, the increase in the thermal efficiency was not substantial. For the considered range of parameters, while the heat transfer performance increased up to 234%, the thermal efficiency increased around 4.4% as the volume fraction increased from 0 to 2.5%. The corresponding reduction in the entropy generation was about 70%.

Graphene as a functional layer for semiconducting carbon nanotube transistor sensors

Single-walled carbon nanotubes (SWCNTs) hold vast potential for future electronic devices due to their outstanding properties, however covalent functionalization often destroys the intrinsic properties of SWCNTs, thus limiting their full potential. Here, we demonstrate the fabrication of a functionalized graphene/semiconducting SWCNT (T@fG) heterostructured thin film transistor as a chemical sensor. In this structural configuration, graphene acts as an atom-thick, impermeable layer that can be covalently functionalized via facile diazonium chemistry to afford a high density of surface functional groups while protecting the underlying SWCNT network from chemical modification, even during a covalent chemical reaction. As a result, the highly functionalized carbon-based hybrid structure exhibits excellent transistor properties with a carrier mobility and ON/OFF ratio as high as 64 cm2/Vs and 5400, respectively. To demonstrate its use in potential applications, T@fG thin films were fabricated as aqueous ammonium sensors exhibiting a detection limit of 0.25 μM in a millimolar ionic strength solution, which is comparable with state-of-the-art aqueous ammonium nanosensors.

Spectroscopic investigation confirms retaining the pristine nature of single-walled carbon nanotubes on dissolution in aniline

Carbon nanotubes in all forms are very much insoluble in both organic and inorganic solvents due to its high agglomeration and entangled morphology. General methods for dissolution of single-walled carbon nanotubes (SWNTs) are mostly associated with complexation or polymerization or addition of macromolecules which change the physical or chemical properties of SWNTs and the pristine nature of SWNTs is lost. Dissolution of SWNTs in a solvent like aniline is practiced here which is a very simple reaction method. Here aniline is capable to form a SWNT-aniline charge transfer complex without attachment of macromolecules or polymer which is also soluble in other organic solvents. Solvation of SWNTs by this method is also capable of maintaining the similarity between the structure of SWNTs before and after the dissolution, which means that the pristine nature of SWNTs is preserved. Formation of charge transfer complex in this reaction has been proven by UV-Vis/NIR absorption and photoluminescence spectroscopy. Raman spectroscopy and electron microscopy (FESEM and TEM) are the evidences for protection of the pristine nature of SWNTs even after high-temperature complexation reaction with aniline and also after solubilization in organic solvents.

Contribution of arabinogalactan protein to the stabilization of single-walled carbon nanotubes in aqueous solution of gum arabic

Nowadays, the application of gum arabic has been extended from food industry as a food gum to broad fields including pharmaceutical, personal care and nanomaterials as a versatile agent providing specific physicochemical properties and functional attributes. Despite of its excellent properties, the complex nature of multicomponent of gum arabic may act as an obstacle to understand profoundly its functionality and relevant mechanism in applications. In this study the effect of arabinogalactan protein (AGP), one of the main components in gum arabic, on the stabilization of single-walled carbon nanotubes (SWNTs) in aqueous gum arabic solution has been clarified. By using gel permeation chromatography coupled with multi-angle laser light scattering system (GPC-MALLS), fluorescence spectroscopy, circular dichroism, surface tension measurement and thermogravimetric analysis as well as atomic force microscope and transmission electron microscopy observation, it is found that the adsorption of AGP on the surface of SWNTs contributes to the stability of nanotubes in water by steric hindrance. The AGP physically modified SWNTs also shows improved biocompatibility. The use of AGP for stabilization of SWNTs dispersions may offer advantages of maintaining the initial properties of SWNTs, and providing biocompatibility and highly adhesive interfaces between individual carbon nanotubes and a biopolymeric matrix that are essential for tissue engineering and medical devices.

Structure and electronic properties of deformed single-walled carbon nanotubes: quantum calculations

The electronic properties of single-walled carbon nanotubes (SWCNTs) can be modified by deforming their structure under high pressure. The aim of this study was to use quantum calculations to investigate one such property, the energy band gap, in relation to molecular structures of armchair and zigzag SWCNTs of various sizes and shapes deformed by applied forces. To model the increase in pressure, the degree of flatness (η) of the SWCNTs was adjusted as the primary parameter. The calculations gave accurate C-C bond lengths of the SWCNTs in their distorted states; these distortions significantly affected the electronic properties, especially the energy band gap of the SWCNTs. These results may contribute to a more refined design of new nano-electronic devices.

Suspended individual SWCNT characterization via bottom gate FET configuration

AbstractThe microwave transmission properties of suspended, quasi‐metallic individual single‐walled carbon nanotubes (SWCNTs) with a bottom gate field‐effect transistor (FET) configuration have been investigated up to 10 GHz by standard two‐port S‐parameter measurements under different gate bias voltages. A tapered coplanar waveguide (CPW) transmission‐line test fixture is designed to overcome the parasitic and mismatch issues. An open‐through de‐embedding algorithm has been applied to extract the intrinsic properties of SWCNTs. And an equivalent circuit model has been proposed to fit the extracted measurement data as a function of the bottom gate bias voltage, facilitating the applications of CNTs into high‐frequency nanocircuits. Moreover, the properties of our transistor device are found to change after a period of time.