Diameter Of Single-walled Carbon Nanotubes Research Articles

Performance and stability analysis of monolayer single‐walled carbon nanotube interconnects

SummaryIn this paper, the monolayer single‐walled carbon nanotube (SWCNT) interconnects are modeled and investigated comprehensively. On the basis of the ratio of the resistance–capacitance values between Cu and SWCNT interconnects, it is demonstrated that the monolayer SWCNT interconnect can provide comparable and even better performance than Cu wire at the 19 nm technology node and beyond. Furthermore, the relative stability analysis is carried out for the monolayer SWCNT interconnects by investigating the relative position of the Nyquist diagram with respect to the critical point (−1, 0). It is shown that the relative stability can be improved by increasing the length and decreasing the SWCNT diameter. Meanwhile, the relative stability also can be improved with the technology advancement. Finally, the crosstalk effects are studied on the basis of the tri‐interconnect architecture. As the monolayer SWCNT interconnects possess much smaller capacitance, the signal integrity can be improved, with the peak noise voltage suppressed greatly. Copyright © 2014 John Wiley & Sons, Ltd.

Molecular dynamics simulation of an argon cluster filled inside carbon nanotubes

The effects of the diameters of single-walled carbon nanotubes (SWCNTs) (7.83 Å to 27.40 Å) and temperature (20 K–45 K) on the equilibrium structure of an argon cluster are systematically studied by molecular dynamics simulation with consideration of the SWCNTs to be fixed. Since the diameters of SWCNTs with different chiralities increase when temperature is fixed at 20 K, the equilibrium structures of the argon cluster transform from monoatomic chains to helical and then to multishell coaxial cylinders. Chirality has almost no noticeable influence on these cylindrosymmetric structures. The effects of temperature and a non-equilibrium sudden heating process on the structures of argon clusters in SWCNTs are also studied by molecular dynamics simulation.

Electrical transport properties of small diameter single-walled carbon nanotubes aligned on ST-cut quartz substrates.

A method is introduced to isolate and measure the electrical transport properties of individual single-walled carbon nanotubes (SWNTs) aligned on an ST-cut quartz, from room temperature down to 2 K. The diameter and chirality of the measured SWNTs are accurately defined from Raman spectroscopy and atomic force microscopy (AFM). A significant up-shift in the G-band of the resonance Raman spectra of the SWNTs is observed, which increases with increasing SWNTs diameter, and indicates a strong interaction with the quartz substrate. A semiconducting SWNT, with diameter 0.84 nm, shows Tomonaga-Luttinger liquid and Coulomb blockade behaviors at low temperatures. Another semiconducting SWNT, with a thinner diameter of 0.68 nm, exhibits a transition from the semiconducting state to an insulating state at low temperatures. These results elucidate some of the electrical properties of SWNTs in this unique configuration and help pave the way towards prospective device applications.

Effects of chirality and diameter of single-walled carbon nanotubes on their structural stability and solubility parameters

The chirality and diameter are found to simultaneously affect the solubility of SWCNTs. The solubility parameter of armchair SWCNTs is greater than that of zigzag SWCNTs, for a given diameter and length, except for very small diameters. The lower structural stability of the armchair SWCNTs leads to smaller molar volumes. Thus, the chirality of SWCNTs alters the structural stability and consequently the solubility parameter of the SWCNTs.

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.

Conjugated polymer-assisted dispersion of single-wall carbon nanotubes: the power of polymer wrapping.

The future application of single-walled carbon nanotubes (SWNTs) in electronic (nano)devices is closely coupled to the availability of pure, semiconducting SWNTs and preferably, their defined positioning on suited substrates. Commercial carbon nanotube raw mixtures contain metallic as well as semiconducting tubes of different diameter and chirality. Although many techniques such as density gradient ultracentrifugation, dielectrophoresis, and dispersion by surfactants or polar biopolymers have been developed, so-called conjugated polymer wrapping is one of the most promising and powerful purification and discrimination strategies. The procedure involves debundling and dispersion of SWNTs by wrapping semiflexible conjugated polymers, such as poly(9,9-dialkylfluorene)s (PFx) or regioregular poly(3-alkylthiophene)s (P3AT), around the SWNTs, and is accompanied by SWNT discrimination by diameter and chirality. Thereby, the π-conjugated backbone of the conjugated polymers interacts with the two-dimensional, graphene-like π-electron surface of the nanotubes and the solubilizing alkyl side chains of optimal length support debundling and dispersion in organic solvents. Careful structural design of the conjugated polymers allows for a selective and preferential dispersion of both small and large diameter SWNTs or SWNTs of specific chirality. As an example, with polyfluorenes as dispersing agents, it was shown that alkyl chain length of eight carbons are favored for the dispersion of SWNTs with diameters of 0.8-1.2 nm and longer alkyls with 12-15 carbons can efficiently interact with nanotubes of increased diameter up to 1.5 nm. Polar side chains at the PF backbone produce dispersions with increased SWNT concentration but, unfortunately, cause reduction in selectivity. The selectivity of the dispersion process can be monitored by a combination of absorption, photoluminescence, and photoluminescence excitation spectroscopy, allowing identification of nanotubes with specific coordinates [(n,m) indices]. The polymer wrapping strategy enables the generation of SWNT dispersions containing exclusively semiconducting nanotubes. Toward the applications in electronic devices, until now most applied approach is a direct processing of such SWNT dispersions into the active layer of network-type thin film field effect transistors. However, to achieve promising transistor performance (high mobility and on-off ratio) careful removal of the wrapping polymer chains seems crucial, for example, by washing or ultracentrifugation. More defined positioning of the SWNTs can be accomplished in directed self-assembly procedures. One possible strategy uses diblock copolymers containing a conjugated polymer block as dispersing moiety and a second block for directed self-assembly, for example, a DNA block for specific interaction with complementary DNA strands. Another strategy utilizes reactive side chains for controlled anchoring onto patterned surfaces (e.g., by interaction of thiol-terminated alkyl side chains with gold surfaces). A further promising application of purified SWNT dispersions is the field of organic (all-carbon) or hybrid solar cell devices.

The dependence of SO3 dissociation on the diameter of single-wall carbon nanotubes based on first-principles calculations

The dissociation of SO3 molecules on the walls of armchair (m, m) (m=3, 5) and zigzag (n, 0) (n=5–10) single-wall carbon nanotubes (SWCNTs) was investigated using first-principles calculations. The calculated reaction enthalpies and energy barriers show a nearly linear decrease with decreasing tube diameter. Our results indicate that the dissociation of SO3 on the walls of SWCNTs is strongly dependent on the tube diameter for the selective etching of SWCNTs with small diameters (d<1nm) by gaseous SO3. Our study sheds light on effective separation of SWCNTs for their practical application in many fields.

Influence of electric fields on the structure and structure transition of water confined in a carbon nanotube

Our previous work demonstrated that liquid water can freeze continuously into either pentagonal or helical solid-like ice nanotubes in a single-walled carbon nanotube (SWCNT) with a tube diameter of 1.2 nm, depending on the strengths of an external electric (E) field applied along the tube axis. In this study, the structure and the structure transition behavior of water confined in a wider SWCNT (diameter = 1.31 nm) under the influence of E-fields are investigated by molecular dynamics simulations using the TIP4P model for water at atmospheric pressure. We find that confined water can freeze into three different polygonal (including hexagonal, heptagonal, and mixed hexagonal-heptagonal) ice nanotubes through a first-order phase transition at lower E (&amp;lt;0.75 V/nm), while form a helical ice nanotube encapsulating a helical water nanoline through a continuous phase transition at higher E (1.0 &amp;lt; E &amp;lt; 2.0 V/nm), different from the phase transition behavior of water in a SWCNT with a diameter = 1.2 nm. The populations of the three different polygonal ice nanotubes are modulated by both temperature and electric field. In addition, an E-induced discontinuous solid-solid phase transition between polygonal and helical ice nanotubes is observed at low temperature (T &amp;lt; 230 K) with a significant electric hysteresis loop of 1.0 V/nm. Finally, we present a rich phase diagram of confined water as a function of temperature and electric field, in which the boundaries of the first-order phase transition at lower E and the continuous phase transition at higher E are connected by a connecting line which corresponds to the hysteresis region.

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.

Diameter distribution control of single-walled carbon nanotubes by etching ferritin nanoparticles

We focused on controlling the diameter of single-walled carbon nanotubes (SWNTs) by controlling the ferritin catalyst diameter using reactive ion etching (RIE). The average diameter of ferritin decreased by about 26.5% upon RIE treatment, which resulted in the decrease of the mean diameter of the SWNTs by about 34% with a small diameter distribution. This was demonstrated by both atomic force microscopic and Raman spectroscopic measurements. We found that the current on/off ratio of the SWNT thin film transistors was significantly improved after the catalyst treatment. It was estimated that the purity of the semiconducting SWNT also increased from 58.8 to 92.4%.

Diporphyrin and Dipyrene Nanocalipers for Discrimination of Diameter and Metallicity in Single-Walled Carbon Nanotubes

We have been developing host-guest methodology for separation of single-walled carbon nanotubes (SWNTs) according to the handedness and diameter with gable-type chiral diporphyrins, designated as diporphyrin nanotweezers, consisting of two porphyrins and rigid spacer in between [1-4]. In this paper, we will talk about next generation of the host molecules focusing on larger diameter of SWNTs, named “nanocalipers” (Figure 1) [5,6].X. Peng, N. Komatsu,* S. Bhattacharya, T. Shimawaki, S. Aonuma, T. Kimura, A. Osuka, "Optically Active Single-Walled Carbon Nanotubes", Nature Nanotechnology, 2 (6), 361-365 (2007)G. Liu, F. Wang, X. Peng, A. F. M. M. Rahman, A. K. Bauri, and N. Komatsu, "Separation of Left- and Right-Handed Structures of Single-Walled Carbon Nanotubes through Molecular Recognition" Handbook of Biomedical Applications of Carbon Nanomaterials; K. M. Kadish and F. D'souza, Eds.; World Scientific: vol. 3, pp. 203-232 (2012).A. F. M. M. Rahman, F. Wang, K. Matsuda, T. Kimura, and N. Komatsu,* "Diameter-based separation of single-walled carbon nanotubes through selective extraction with dipyrene nanotweezers" Chem. Sci., 2 (5), 862-867 (2011) [highlighted at the inside front cover].F. Wang, K. Matsuda, A. F. M. M. Rahman, X. Peng, T. Kimura, and N. Komatsu,* "Simultaneous Discrimination of Handedness and Diameter of Single-Walled Carbon Nanotubes (SWNTs) with Chiral Diporphyrin Nanotweezers Leading to Enrichment of Single Enantiomer of (6,5)-SWNTs", J. Am. Chem. Soc., 132 (31), 10876-10881 (2010).G. Liu, A. F. M. M. Rahman, S. Chaunchaiyakul, T. Kimura, Y. Kuwahara, N. Komatsu,* "Bis(tert-butylpyrene) Nanotweezers and Nanocalipers: Enhanced Extraction and Recognition Abilities for Single-Walled Carbon Nanotubes", Chem. Eur. J., published online (DOI: 10.1002/chem.201302799).G. Liu, F. Wang, S. Chunchaiyakul, Y. Saito, A. K. Bauri, T. Kimura, Y. Kuwahara, N. Komatsu,* "Simultaneous Discrimination of Diameter, Handedness, and Metallicity of Single-Walled Carbon Nanotubes with Chiral Diporphyrin Nanocalipers", J. Am. Chem. Soc., 135 (12), 4805-4814 (2013) [highlighted in Chemical & Engineering News, 91 (12), p. 34, March 25, 2013].

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.

A theoretical and experimental exploration of the mechanism of microwave assisted 1,3-dipolar cycloaddition of pyridinium ylides to single walled carbon nanotubes

Cycloaddition reactions have widely been used for surface functionalization of single walled carbon nanotubes (SWNTs). Here, 1,3-dipolar cycloaddition (1,3-DC) of two new pyridinium ylides, generated in-situ via the addition of triethylamine (NEt3) to the Kröhnke salts N-(4-methyl sodium benzene sulfonate)-pyridinium bromide and N-(4-nitrobenzyl)-pyridinium bromide, to SWNTs under microwave conditions are assessed both theoretically using PM3 (RHF) type calculations and experimentally. Evidence of covalent surface modification is provided by FTIR, UV–vis–NIR and resonance Raman spectroscopy. Solubility of the modified SWNTs increases when compared to as-received SWNTs. Quantification of surface groups is performed via TGA-MS and XPS. 1,3-DC of pyridinium ylides with smaller HOMO–LUMO energy gap is found to be more selective to large diameter SWNTs. Theoretically predicted smaller energy gaps between HOMOylides and LUMO(8,8) SWNT suggest that the charges are probably transferred from pyridinium ylides to SWNTs indicating HOMOylide–LUMO(8,8) SWNT controlled 1,3-DC. Regioselectivity of second ylide addition as addendum to ylide–SWNT adduct is also discussed.

Elastic properties of single-walled carbon nanotube clusters: Dependence on hydrostatic pressure

Carbon nanotube (CNT) clusters have different properties from free-stand CNTs. This paper aims to investigate the effect of hydrostatic pressure on the elastic properties of single-walled carbon nanotube (SWCNT) clusters composed of armchair SWCNTs of diameters below 2nm. A simple representative volume element in a periodic cell was constructed. Molecular mechanics (MM) was used to optimize the geometry and to evaluate the elastic properties in different pressure states. The results showed that the collapse pressure of SWCNT clusters varies exponentially with increasing the SWCNT diameter, that all elastic properties increase with the hydrostatic pressure rise, except the transverse Young’s modulus, and that the external pressure has the most impact on the out-of-plan shear modulus.

Diameter control of single-walled carbon nanotube forests from 1.3–3.0 nm by arc plasma deposition

We present a method to both precisely and continuously control the average diameter of single-walled carbon nanotubes in a forest ranging from 1.3 to 3.0 nm with ~1 Å resolution. The diameter control of the forest was achieved through tuning of the catalyst state (size, density, and composition) using arc plasma deposition of nanoparticles. This 1.7 nm control range and 1 Å precision exceed the highest reports to date.

The synthesis of single-walled carbon nanotubes with narrow diameter distribution using polymerized hemoglobin

Single-walled carbon nanotubes (SWCNTs) with a narrow diameter distribution were synthesized by using polymerized hemoglobin (PolyHb). PolyHb containing 11 Hb molecules (11-PolyHb) was separated from a mixture of PolyHb with various degrees of polymerization by using size-exclusion chromatography (SEC). After the deposition and oxidation of 11-PolyHb, we obtained iron oxide nanoparticles with an average diameter of 1.30±0.36nm. SWCNT were grown from these nanoparticles with a narrow diameter distribution, 1.08±0.26nm. This technique has the potential to synthesize SWCNT with an identical diameter, and to control the diameter of SWCNT at atomic resolution through improvements to the SEC processing.

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.

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We demonstrated size control of Au nanoparticles by heat treatment and their use as a catalyst for single-walled carbon nanotube (SWNTs) growth with narrow size distribution. We used uniformly sized Au nanoparticles from commercial Au colloid, and intentionally decreased their size through heat treatment at 800 oC under atmospheric Ar ambient. ST-cut quartz wafers were used as growth substrates to achieve parallel alignment of the SWNTs and to investigate the size relationship between Au nanoparticles and SWNTs. After the SWNTs were grown via chemical vapor deposition using methane gas, it was found that a high degree of horizontal alignment can be obtained when the particle density is low enough to produce individual SWNTs. The diameter of the Au nanoparticles gradually decreased from 3.8 to 2.9 nm, and the mean diameter of the SWNTs also changed from 1.6 to 1.2 nm for without and 60 min heat treatment, respectively. Raman results reconfirmed that the prolonged heat treatment of nanoparticles yields thinner tubes with narrower size distribution. This work demonstrated that heat treatment can be a straightforward and reliable method to control the size of catalytic nanoparticles and SWNT diameter.

Fluctuation theory of single-walled carbon nanotube formation

In the framework of classical fluctuation theory an analytical formula is derived for the reversible work of formation of just detached carbon cap on the surface of catalyst nanoparticle (NP). This cap is considered as single walled carbon nanotube (SWCNT) formation center. The work of cap formation depends on the source carbon chemical potential μC. Using the derived formula for this work an expression for the rate of SWCNT formation is determined. From this expression the SWCNT diameter distributions can be obtained. The obtained distributions have sharp maxima. It is found that the modal SWCNT diameter d(m) increases weakly with μC being in the narrow window of 1.0 < d(m) < 1.8 nm when changing the source carbon chemical potential in a wide range. The determined diameter distributions proved to be in a good agreement with the typical values of the SWCNT diameters as experimentally measured in the chemical vapor deposition process. The increase of d(m) is accompanied by the increase of the distribution width Δd. The selectivity d(m)/Δd is a function of μC, the higher values of μC the worse selectivity is observed. Although the value of the SWCNT formation rate I cannot be calculated precisely the relationship between I and the system parameters, such as the NP radius R(S), can be obtained. This relationship is derived for the solid-liquid-solid system. To determine the function I(R(S)) for nanotubes of a certain diameter d, formulas for catalyst∕amorphous carbon mutual solubilities as functions of NP radius are derived in the framework of the rigorous Gibbs theory of interface. Using the derived formulas an expression giving the dependence I(R(S)) is obtained. The expression predicts an increase of I with the radius R(S). The estimations carried out for the metal/carbon interface surface tension of 1000 mN/m show that the SWCNT formation rate increases by a few orders of magnitude with the radius increase from 1 to 10 nm.

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.