Length Of Single-walled Carbon Nanotubes Research Articles

ChemInform Abstract: State of the Art of Single‐Walled Carbon Nanotube Synthesis on Surfaces

AbstractReview: 187 refs.

Uncertainty quantification for multiscale modeling of polymer nanocomposites with correlated parameters

We propose a stochastic multiscale method to quantify the correlated key-input parameters influencing the mechanical properties of polymer nanocomposites (PNCs). The variations of parameters at nano-, micro-, meso- and macro-scales are connected by a hierarchical multiscale approach. The first-order and total-effect sensitivity indices are determined first. The input parameters include the single-walled carbon nanotube (SWNT) length, the SWNT waviness, the agglomeration and volume fraction of SWNTs. Stochastic methods consistently predict that the key parameters for the Young’s modulus of the composite are the volume fraction followed by the averaged longitudinal modulus of equivalent fiber (EF), the SWNT length, and the averaged transverse modulus of the EF, respectively. The averaged longitudinal modulus of the EF is estimated to be the most important parameter with respect to the Poisson’s ratio followed by the volume fraction, the SWNT length, and the averaged transverse modulus of the EF, respectively. On the other hand, the agglomeration parameters have insignificant effect on both Young’s modulus and Poisson’s ratio compared to other parameters. The sensitivity analysis (SA) also reveals the correlation between the input parameters and its effect on the mechanical properties.

A compact analytical method for vibration analysis of single-walled carbon nanotubes with restrained boundary conditions

In the present study, free vibration of single-walled carbon nanotubes (SWCNTs) with restrained boundary conditions is studied using nonlocal elasticity theory. To give generality to the present problem, the SWCNT is assumed to be elastically restrained by means of rotational and translational springs at the ends. The lateral displacement function is considered to be in the form of a Fourier sine series. The first, second and higher order derivatives of the Fourier sine series are legitimized using Stoke's transformation. The main advantage of this transformation is its capability of dealing with various boundary conditions to determine the vibration frequencies. Numerical results are given for different nonlocality parameters, different length of SWCNTs and different boundary conditions. The present formulation can be used for the dynamic analyses of SWCNTs with generally restrained boundary conditions.

State of the art of single-walled carbon nanotube synthesis on surfaces.

Single-walled carbon nanotubes (SWNTs) directly synthesized on surfaces are promising building blocks for nanoelectronics. The structures and the arrangement of the SWNTs on surfaces determine the quality and density of the fabricated nanoelectronics, implying the importance of structure controlled growth of SWNTs on surfaces. This review summarizes the recent research status in controlling the orientation, length, density, diameter, metallicity, and chirality of SWNTs directly synthesized on surfaces by chemical vapor deposition, together with a session presenting the characterization method of the chirality of SWNTs. Finally, the remaining major challenges are discussed and future research directions are proposed.

Determination of the Length, Diameter, Molecular Mass, Density and Surfactant Adsorption of SWCNTs in Dilute Dispersion by Intrinsic Viscosity, Sedimentation, and Diffusion Measurements

A combination of intrinsic viscosity, sedimentation, and diffusion measurements is performed to characterize the structures of single-walled carbon nanotubes (SWCNTs) in dilute dispersion. It allows quantifying the bulk averaged length (L), diameter (d), molecular mass (M), and density (ρ) as well as the surfactant adsorption for SWCNTs. With this approach applied to the SWCNTs processed by sonication, a novel Mark–Houwink–Sakurada equation, [η]c = 1.17M0.33 is recovered. The less than 0.5 exponent is a result of the power-law relationship d ∝ L0.62 caused by the concurrently occurred cutting and exfoliation of SWCNT bundles in the sonication process. An in-depth analysis of the experimentally acquired d and ρ enables a quantification of sodium dodecylbenzenesulfonate (SDBS) adsorption on SWCNTs to reveal the curvature effect on the surface coverage of surfactant adsorption.

Use of gel electrophoresis and Raman spectroscopy to characterize the effect of the electronic structure of single-walled carbon nanotubes on cellular uptake.

It is well-known that the uptake of single-walled carbon nanotubes (SWNTs) by living cells depends on factors such as SWNT length and surface chemistry. Surprisingly, little is known about whether the electronic structure of a SWNT influences uptake. One reason for this has been the lack of methods to measure the uptake of SWNTs by cell populations. Previously, we developed a rapid, sensitive, and label-free sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) method for measuring the amount of SWNTs in lysates prepared from cultured cells (Wang et al. Anal. Chem.2009, 81, 294419296592). Herein, we describe the use of SDS-PAGE and microprobe Raman spectroscopy to detect and distinguish the electronic structure of SWNTs internalized by mammalian cells. Using normal rat kidney (NRK) cells and SWNTs dispersed with bovine serum albumin (BSA), we demonstrate that the method can detect both metallic and semiconducting SWNTs in lysates of cells that had internalized BSA-SWNTs and that the uptake of BSA-SWNTs by NRK cells is not influenced by SWNT electronic structure.

Energy Transfer from C-Phycocyanin to Single-Walled Carbon Nanotubes

The energy transfer from C-phycocyanin (C-PC) to single-walled carbon nanotubes (SWNTs) in SWNT/C-PC hybrids is investigated using optical absorption and fluorescence spectroscopy. A suspension-dialysis method is used to assemble the SWNTs and C-PC proteins. The proteins cover partially the SWNT length as observed on atomic force microscopy images and transmission electron microscopy micrographs. Photoluminescence measurements show a strong enhancement of emission intensity of several SWNT species, while a strong decrease of the C-PC emission occurs in the presence of SWNTs. Our data suggest that a nonradiative resonance energy transfer takes place after the excitation of the C-PC with a high efficiency.

Dynamic Mechanism of Single-Stranded DNA Encapsulated into Single-Wall Carbon Nanotubes: A Molecular Dynamics Simulation Study

Hybrids of single-walled carbon nanotubes (SWCNTs) and biological molecules have been utilized for numerous applications in sensing, imaging, and drug delivery. By molecular dynamics simulation, we investigate the encapsulation of single-strand DNA (ssDNA) containing eight adenine bases with \((17,17)\)–\((12,12)\) SWCNTs. The effects of the diameter and length of SWCNTs on the encapsulation process are explored with the calculated curves of the center-of-mass distance, the van der Waals interaction between the ssDNA and SWCNT, the root-mean-square deviation of the ssDNA, and the radius of gyration of the ssDNA. The free energy of the encapsulated ssDNA for each SWCNT is also obtained via steered molecular dynamics simulation. The most suitable SWCNT for encapsulating the ssDNA is also suggested.

Assessment of length and bundle distribution of dilute single‐walled carbon nanotubes by viscosity measurements

Rheological measurements have long been an invaluable technique in studying mechanical and structural properties of polymers. Measurements on dilute, noninteracting polymer solutions allow the determination of macromolecular structural information, such as molecular weight. This analysis has been complicated by molecular polydispersity; thus, average effects are more commonly reported. Here, we demonstrate polydispersity characterization for rod‐like polymers like single‐walled carbon nanotubes (SWCNTs). By extending the theory of the rheological behavior of rigid rods, we determine the distribution of length and bundle size in suspensions of SWCNTs by a simple rheological method. The method is based on measuring the viscosity of dilute suspended SWCNTs over a shear rate range spanning the Newtonian and shear‐thinning regimes. We show that a log‐normal distribution in length with minimal bundling accurately describes the viscosity measurements. This rapid new method yields the SWCNT length distribution while relying on bulk samples, which are less prone to artifacts. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1499–1508, 2014

Spontaneous nanoinjection with carbon nanotubes: a molecular dynamics simulation study.

Based on the interactions between the zinc finger protein (ZNF) and single-walled carbon nanotubes (SWCNTs), we design a nanodevice for injecting ZNF spontaneously. The new injection device involves four essential components: a small-diameter SWCNT as a plunger, a large-diameter SWCNT as a tube as well as the nozzle and needle, ZNF and water solution. The injection behavior is demonstrated and analyzed using molecular dynamics simulations. The effects of the diameter, chirality and length of SWCNTs on the injection behavior are analyzed with the center of mass distance, the van der Waals interaction between ZNF and SWCNTs, the root-mean-square deviation of ZNF, and the radius of gyration for ZNF.

Stress intensity factor analysis of epoxy/SWCNTs based on global-local multiscale method

Carbon nanotube (CNT) is considered as a new generation of material possessing superior mechanical, thermal, and electrical properties. In this research, a multiscale finite element analysis is proposed to study the interaction between nanotubes and matrix at the nanoscale near a crack tip. The influence of the chirality and length of single-walled CNT (SWCNTs) on the stress intensity factor of epoxy/SWCNT were studied. It was found that the chirality, length, and radius of CNT have significant effects on the stress intensity factor of nanocomposites. Multiscale simulations from macro to nano or the reverse improved specification of toughness mechanisms.

Structures of Hybrids of DNA and Carbon Nanotubes Observed by Atomic Force Microscopy in Air and in Liquids

We investigated single-walled carbon nanotubes (SWNT) and DNA-SWNT hybrids by atomic force microscopy (AFM). From the AFM observation of several different types of SWNTs and DNA-SWNT hybrids in air, we found several specific differences in morphology among the samples. First, longer SWNT molecules were observed when the SWNT was dispersed using a bath type sonicator. When a probe type sonicator was employed, much shorter SWNT molecules were observed in all of our experiments using several different SWNTs. The result suggests that effects of the type of sonicator on SWNT length were significant in contrast to that of the type of SWNTs. Second, SWNT functionalized with polyethyleneglycol (PEG SWNT), amino group (NH 2 SWNT), and carboxyl group (COOH SWNT) individually showed specific features in AFM images. Although NH 2 SWNT is typically soluble in organic solvents, uniform distribution was observed when DNA molecules were mixed with NH 2 SWNT. Finally, we observed DNASWNT hybrids by AFM in liquids for the first time. DNA-SWNT hybrids were significantly swollen in the aqueous solution even though the sample was dried once. This is helpful information for considering biological applications of the DNA-SWNT hybrids.

Activity inhibition on municipal activated sludge by single-walled carbon nanotubes

The objective of this study was to evaluate the respiratory activity inhibition of activated sludge used in a typical wastewater treatment plant by single-walled carbon nanotubes (SWCNTs) with different length and functionality. Four types of SWCNTs were evaluated: short, functionalized short, long, and functionalized long. Based on the effective concentration (EC50) values obtained, we determined that functionalized SWCNTs resulted in a higher microbial respiratory inhibition than non-functionalized nanotubes, and long SWCNTs gave a higher microbial respiratory inhibition than their short counterparts. Among the four types of SWCNTs studied, functionalized long exhibited the highest respiration inhibition. Scanning electron microscopy imaging indicates that the long SWCNTs dispersed more favorably after sonication than the short variety. The findings demonstrated that the toxicity of CNTs (exhibited by respiratory inhibition) is related to their physical properties; the length and functionality of SWCNTs affected the toxicity of SWCNTs in a mixed-cultured biologic system.

Influence of lengths of millimeter-scale single-walled carbon nanotube on electrical and mechanical properties of buckypaper

The electrical conductivity and mechanical strength of carbon nanotube (CNT) buckypaper comprised of millimeter-scale long single-walled CNT (SWCNT) was markedly improved by the use of longer SWCNTs. A series of buckypapers, fabricated from SWCNT forests of varying heights (350, 700, 1,500 μm), showed that both the electrical conductivity (19 to 45 S/cm) and tensile strength (27 to 52 MPa) doubled. These improvements were due to improved transfer of electron and load through a reduced number of junctions for longer SWCNTs. Interestingly, no effects of forest height on the thermal diffusivity of SWCNT buckypapers were observed. Further, these findings provide evidence that the actual SWCNT length in forests is similar to the height.

Dispersion of single-walled carbon nanotubes by intense turbulent shear in micro-channels

Dispersion of carbon nanotubes (CNTs) in solvents is a prerequisite for arriving at their expected performances in applications. Our objective is twofold. We first assess an intense turbulent shear (ITS) method in a micro-channel system, with a shear rate of 3×106s−1, in preparing single-walled CNT (SWCNT) dispersions in aqueous solution of sodium dodecyl benzene sulfonate, and compare it with sonication. We conclude that the ITS method is much more effective than sonication, with respect to preparation time, exfoliation of the SWCNT bundles, and the obtained SWCNT concentration in the dispersion, thus proposed in practical applications. Then, a method based on the depolarized dynamic light scattering, combined with the wide-angle (static) light scattering, has been proposed to characterize the average length and diameter of the dispersed SWCNTs. Its reliability in the estimated values of the average length and diameter of the SWCNTs has been assessed and caution has been given in its applications.

“Zero-Dimensional” Single-Walled Carbon Nanotubes

The shorter, the more dispersible: An iterative, emulsion-based shortening technique has been used to reduce the length of single-walled carbon nanotubes (SWNTs) to the same order of magnitude as their diameter (ca. 1 nm), thus achieving an effectively "zero-dimensional" structure with improved dispersibility and, after hydroxylation, long-term water solubility. Finally, zero-dimensional SWNTs were positively identified using mass spectrometry for the first time.

Ionization potentials and structural properties of finite-length single-walled carbon nanotubes: DFT study

Adiabatic and vertical ionization potentials (IPs) of single-walled carbon nanotubes (SWCNTs) as a function of length were determined by using density functional theory. The correlation between periodic oscillations of SWCNTs local aromaticity and the values of IPs was founded. In the case of short SWCNTs an appreciable gap between vertical and adiabatic IPs was observed, whereas for longer nanotubes these values are almost equal. It was also established that the HOMO electron density distribution in neutral SWCNTs affects on SWCNT lengths upon ionization.

First-passage theory of exciton population loss in single-walled carbon nanotubes reveals micron-scale intrinsic diffusion lengths

One-dimensional crystals have long range translational invariance which manifests as long exciton diffusion lengths, but such intrinsic properties are often obscured by environmental perturbations. We use a first-passage approach to model single-walled carbon nanotube (SWCNT) exciton dynamics (including exciton-exciton annihilation and end effects) and compare it to results from both continuous-wave and multipulse ultrafast excitation experiments to extract intrinsic SWCNT properties. Excitons in suspended SWCNTs experience macroscopic diffusion lengths, on the order of the SWCNT length (1.3--4.7 $\ensuremath{\mu}$m), in sharp contrast to encapsulated samples. For these pristine samples, our model reveals intrinsic lifetimes (350--750 ps), diffusion constants (130--350 cm${}^{2}$/s), and absorption cross sections (2.1--$3.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$ cm${}^{2}$/atom) among the highest previously reported.

Variable Range Hopping in Single-Wall Carbon Nanotube Thin Films: A Processing–Structure–Property Relationship Study

By varying the ultrasonication and ultracentrifugation conditions, single-walled carbon nanotube (SWCNT) dispersions with a broad range of SWCNT length and diameter (L = 342-3330 nm; d = 0.5-12 nm) were prepared and characterized by a preparative ultracentrifuge method (PUM) and dynamic light scattering (DLS) technique. The well-characterized dispersions were then fabricated into SWCNT thin films by spray coating. Combined optical, spectroscopic, and temperature-dependent electrical measurements were performed to study the effect of SWCNT structures on the charge transport behavior of SWCNT thin films. Regardless of SWCNT size in the dispersion and the thin film thickness, the three-dimensional variable range hopping (3D VRH) conduction model was found to be appropriate in explaining the temperature-dependent sheet resistance results for all SWCNT thin films prepared in this study. More importantly, with the SWCNT structural information determined by the PUM method, we were able to identify a strong correlation between the length of SWCNTs and the 3D VRH parameter T0, the Mott characteristic temperature. When the SWCNT length is less than ∼700 nm, the T0 of SWCNT thin films shows a drastic increase, but when the length is greater than ~700 nm, T0 is only weakly dependent on the SWCNT length. Under the framework of traditional VRH, we further conclude that the electron localization length of SWCNT thin films shows a similar dependence on the SWCNT length.

Temperature, defect and size effect on the elastic properties of imperfectly straight carbon nanotubes by using molecular dynamics simulation

The mechanical characteristics of single-walled carbon nanotubes (SWCNTs) with an axial curvature of single and double bents were studied in this work via molecular dynamics simulation method. SWCNTs when synthesized in laboratory conditions are seldom perfectly straight, and exhibit one or several bents along their tube axis. This feature is often not considered when investigating the mechanical properties of SWCNT using computer or theoretical simulation studies. In this work, the mechanical properties of SWCNTs with single and double bents are determined to understand its variation from the ideal ‘perfectly straight’ SWCNTs. Our results indicate that presence of bents will strongly influence on the elastic strain of the SWCNTs. The variation in the elastic properties due to bents is more sensitive to the length of SWCNT and becomes negligible at high temperatures.