Chiral Nanotubes Research Articles

Stacking Fault Nucleation in Films of Vertically Oriented Multiwall Carbon Nanotubes by Pyrolysis of Ferrocene and Dimethyl Ferrocene at a Low Vapor Flow Rate

Recent observations of superconductivity in low-dimensional systems composed of twisted, untwisted, or rhombohedral graphene have attracted significant attention. One-dimensional moiré superlattices and flat bands have interestingly been identified in collapsed chiral carbon nanotubes (CNTs), opening up new avenues for the tunability of the electronic properties in these systems. The nucleation of hexagonal moiré superlattices and other types of stacking faults has also been demonstrated in partially collapsed and uncollapsed carbon nano-onions (CNOs). Here, we report a novel investigation on the dynamics of stacking fault nucleation within the multilayered lattices of micrometer-scale vertically oriented films of multiwall CNTs (MWCNTs), resulting from the pyrolysis of molecular precursors consisting of ferrocene or dimethyl ferrocene, at low vapor flow rates of ~5–20 mL/min. Interestingly, local nucleation of moiré-like superlattices (as stacking faults) was found when employing dimethyl ferrocene as the pyrolysis precursor. The morphological and structural properties of these systems were investigated with the aid of scanning and transmission electron microscopies, namely SEM, TEM, and HRTEM, as well as X-ray diffraction (XRD) and Raman point/mapping spectroscopy. Deconvolution analyses of the Raman spectra also demonstrated a local surface oxidation, possibly occurring on defect-rich interfaces, frequently identified within or in proximity of bamboo-like graphitic caps. By employing high-temperature Raman spectroscopy, we demonstrate a post-growth re-graphitization, which may also be visualized as an alternative way of depleting the oxygen content within the MWCNTs’ interfaces through recrystallization.

First-principles study of aromatic amino acid encapsulation in single-walled BN and AlN nanotubes

Aromatic molecules exhibit strong non-covalent interactions with nanotubes, influencing their encapsulation properties. This study uses DFT calculations to explore the encapsulation of aromatic amino acids within zigzag (ZZ), chiral (R/S), and armchair (AC) single-walled aluminum nitride nanotubes (AlNNTs) and boron nitride nanotubes (BNNTs). The results reveal that zigzag AlNNTs exhibit the highest encapsulation affinity compared to other chiralities, while chiral BNNTs show enhanced encapsulation. Encapsulation energy decreases with increasing nanotube radius, indicating reduced affinity. Overall, the studied BNNTs demonstrate stronger encapsulation energy compared to AlNNTs. The bandgap energy of the encapsulated structures varies significantly with nanotube diameter and chirality. The physisorption process plays a major role in encapsulation, affecting the geometric and electronic properties of the nanotubes and enhancing the stability and efficacy of the encapsulated amino acids. These findings highlight the potential of these nanostructures for advanced applications, including targeted drug delivery and molecular sensing.

MODELING OF THE GEOMETRY AND ELECTRONIC BANDGAP STRUCTURE OF CHIRAL SINGLE WALLED CARBON NANOTUBES

Carbon Nanotubes (CNTs) are one-dimensional nanostructured materials that will play a key role in future electronics. All properties of the carbon nanotubes are determined by its electronic structure. The main focus of this study has been to investigate the basic electronic bandgap structure of the chiral single walled carbon nanotubes (SWCNTs). A simple algorithm is presented in order to model the geometry of the chiral single-walled CNTs with any desired structure. The electronic bandgap structure of the chiral single-walled carbon nanotubes has been studied by employing an extended tight binding model (TBM). The changes in the energy band gap due to the chirality effect in case of metallic (6, 3) SWCNT and in the semiconducting (12, 7) SWCNT are discussed here. The value of the SWCNTs diameter is calculated also. The computed results indicates that the bandgap depends inversely on the diameter of the tube. The present results were found to be in consistent with those reported in the literature and indicated the correctness of the process of simulation technique process.

Large Superconducting Diode Effect in Chiral Carbon Nanotubes

Superconducting electronics are ubiquitous in devices ranging from single-photon detectors to quantum bits. One of the most common superconducting circuit elements is a Josephson junction (JJ)—a junction of two superconductors coupled through either a small normal metal or an insulator. Recently, non-reciprocal switching currents in JJs based on traditional superconductors have been reported, demonstrating a robust diode effect. This so-called Josephson diode effects (JDEs) has since attracted interest to shed light on material and device properties, but also to enable new applications. In this talk, we will present theoretical results on the JDE in chiral carbon nanotubes (CNTs). We find that these CNT-JJs can exhibit large diode efficiencies when an external magnetic field is applied along the nanotube. Additionally, our numerical simulations show that the polarity of the diode can be tuned by electrostatically gating the CNT-JJ. We will discuss the microscopic details that give rise to large diode efficiencies and gate-tunability in chiral CNT-JJs.This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award DE-SC0022245. The work at Sandia is supported by a LDRD project. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

2 + 2] Cycloaddition Produces Divalent Organic Color-Centers with Reduced Heterogeneity in Single-Walled Carbon Nanotubes.

Organic color centers (OCCs), generated by the covalent functionalization of single-walled carbon nanotubes, have been exploited for chemical sensing, bioimaging, and quantum technologies. However, monovalent OCCs can assume at least 6 different bonding configurations on the sp2 carbon lattice of a chiral nanotube, resulting in heterogeneous OCC photoluminescence emissions. Herein, we show that a heat-activated [2 + 2] cycloaddition reaction enables the synthesis of divalent OCCs with a reduced number of atomic bonding configurations. The chemistry occurs by simply mixing enophile molecules (e.g., methylmaleimide, maleic anhydride, and 4-cyclopentene-1,3-dione) with an ethylene glycol suspension of SWCNTs at elevated temperature (70-140 °C). Unlike monovalent OCC chemistries, we observe just three OCC emission peaks that can be assigned to the three possible bonding configurations of the divalent OCCs based on density functional theory calculations. Notably, these OCC photoluminescence peaks can be controlled by temperature to decrease the emission heterogeneity even further. This divalent chemistry provides a scalable way to synthesize OCCs with tightly controlled emissions for emerging applications.

Diverse Chiral Nanotubes Assembled from Identical DNA Strands.

DNA nanotubes with controllable geometries hold a wide range of interdisciplinary applications. When preparing DNA nanotubes of varying widths or distinct chirality, existing methods require repeatedly designing and synthesizing specific DNA sequences, which can be costly and laborious. Here, we proposed an intercalator-assisted DNA tile assembly method which enables the production of DNA nanotubes of diverse widths and chirality using identical DNA strands. Through adjusting the concentration of intercalators during assembly, the twisting direction and extent of DNA tiles could be modulated, leading to the formation of DNA nanotubes featuring controllable widths and chirality. Moreover, through introducing additional intercalators and secondary annealing, right-handed nanotubes could be reconfigured into distinct left-handed nanotubes. We expect that this method could be universally applied to modulating the self-assembly pathways of various DNA tiles and other chiral materials, advancing the landscape of DNA tile assembly.

Unraveling planar chirality in pillar[5]arenes

Pillar[5]arenes have attracted considerable interests in the areas of supramolecular chemistry, material science and stereochemistry. However, they likely encounter a challenge in obtaining stable enantiomers due to the presence of rotational single bonds in the cavity structure, instead leading to a high predisposition to racemization. This review summarizes approaches that have been developed to address this issue by effectively constraining their free rotation, including the introduction of bulky substituents and formation of mechanical interlock structures. The controllable flipping behavior of chiral bismacrocycles with pillar[5]arenes as the core is reviewed under the stimulation of external environment. Moreover, we will discuss the application areas that rely on the planar chirality of pillar[5]arene, such as circularly polarized luminescence, molecular recognition, and chiral organic nanotubes.

Impact of Atomic Vacancy Defects on Vibrational Characteristics of Chiral MWCNT for Viruses/Bacteria

In this study the authors investigated the vibrations performance of chiral multi-walled carbon nanotubes (MWCNTs). They examined chiral MWCNTs with attached bacteria positioned at both the tip and middle sections of the nanotubes. The main goal of this research was to create a sensor with the ability to detect and distinguish bacteria or viruses that could potentially adhere to the surfaces of chiral MWCNTs. The authors considered two boundary conditions, fixed-fixed and fixed -free for the chiral MWCNT. They utilized a molecular structural mechanics approach. In this approach the vibrational responses of chiral MWCNT-based nano-biosensors with different diameters of the chiral MWCNTs were examined. The study’s objective was to fill research gaps by introducing an innovative approach for detecting defects in chiral MWCNTs through vibrational analysis. They simulated 432 MWCNT samples to investigate the vibrational performance of defective chiral MWCNTs. The results suggested that the first mode of the vibrational frequency of the chiral MWCNT is particularly significant for sensing applications. It was observed that as the percentage of vacancy defects increased, the natural frequency decreased for both boundary conditions.

Pressure-induced structural modifications of imogolite nanotubes and of their methylated analogues

Structural modifications of single-walled aluminosilicate clay nanotubes have been studied under hydrostatic pressure by in situ synchrotron X-ray scattering. Imogolite nanotubes (INT) of nominal composition (OH)3Al2O3SiOH, and methyl-modified imogolite nanotubes (m-INT), (OH)3Al2O3SiCH3, have hydrophilic and hydrophobic internal cavities, respectively. Nanotube chiralities also differ, with zigzag (INT) and armchair (m-INT) chirality. In this work, pressure-induced changes in nanotube morphology and atomic structure are studied as a function of chirality, affinity of the inner cavity, and the pressure-transmitting medium used. Radial deformation and collapse of nanotubes are evidenced below 3 GPa, followed by the formation of a lamellar phase at higher pressures. In the case of INT, the collapse pressure value depends on the pressure transmitting medium chosen. Axial compressibility is measured, and a pseudo Young's modulus Y is determined to be equal to ∼265 GPa for INT and below 80 GPa for m-INT, underpinning the role of nanotube chirality in mechanical properties.

Photoinduced Dynamics of a Single-Walled Carbon Nanotube with a sp3 Defect: The Importance of Excitonic Effects.

Herein, we employed linear-response time-dependent functional theory nonadiabatic dynamic simulations to explore the photoinduced exciton dynamics of a chiral single-walled carbon nanotube CNT(6,5) covalently doped with a 4-nitrobenzyl group (CNT65-NO2). The results indicate that the introduction of a sp3 defect leads to the splitting of the degenerate VBM/VBM-1 and CBM/CBM+1 states. Both the VBM upshift and the CBM downshift are responsible for the experimentally observed redshifted E11* trapping state. The simulations reveal that the photoinduced exciton relaxation dynamics completes within 500 fs, which is consistent with the experimental work. On the other hand, we also conducted the nonadiabatic carrier (electron and hole) dynamic simulations, which completely ignore the excitonic effects. The comparison demonstrates that excitonic effects are indispensable. Deep analyses show that such effects induce several dark states, which play an important role in regulating the photoinduced dynamics of CNT65-NO2. The present work demonstrates the importance of including excitonic effects in simulating photoinduced processes of carbon nanotubes. In addition, it not only rationalizes previous experiments but also provides valuable insights that will help in the future rational design of novel covalently doped carbon nanotubes with superior photoluminescent properties.

Dichroism of plasmonic chiral nanoalloys by rational design.

Time-dependent density functional theory (TDDFT) simulations are conducted on a series of chiral gold/silver alloy nanowires to explore whether silver doping can produce an enhancement of circular dichroism at the plasmon resonance in these systems, and to identify the quantum-mechanical origin of the observed effects. We find a strong plasmonic dichroism when one or two helixes of gold atoms are substituted by silver in a linear chiral nanotube, whose pure gold counterpart does not display any plasmonic dichroism, and we rationalize this finding in terms of "decoupling" the destructive interference of excitations in the pure gold nanotube via alloying. However, further attempts to increase the plasmonic dichroism by considering multi-shell gold nanowires in which one entire shell is doped with silver did not produce the desired effect, but rather a decrease in circular dichroism. We show that this latter result is due to a more severe destructive interference in the dipole excitation contributions, and suggest that further amplification should be possible in principle by properly tuning simultaneously the nanowire structure and chemical ordering.

Exploring the potential of inherent chiral single-walled carbon nanotubes in enantioselective electrochemical sensing: A novel microsensor for discriminating DOPA enantiomers

A range of electrochemical sensors capable of enantiomer discrimination have been developed, but the creation of their electrochemical interfaces remains complex. This often entails combining externally introduced chiral centers with conductive materials. This study marks a significant departure from this approach by exploiting the inherent chirality of single-walled carbon nanotubes (SWCNTs) for enantiomer discrimination. We have crafted a miniaturized, enantioselective electrochemical microsensor by seamlessly integrating high-purity SWCNTs, possessing inherent chirality, with an ultra-sensitive carbon fiber microelectrode. Using differential pulse voltammetry, we observed a notable difference in peak current, highlighting the sensor's precise ability to distinguish between enantiomers of 3,4-dihydroxyphenylalanine (DOPA). Furthermore, we investigated the intricacies of the interplay between enantioselective interfaces and the molecules under discrimination, offering deeper insights into the mechanisms governing this phenomenon. This study provides substantial momentum into the realm of enantioselective electrochemical sensing and sheds light on the unique attributes of inherently chiral carbon nanotubes in such applications. This paves the way for a new breed of chiral sensors that are simpler, more efficient, and cost-effective.

DFT modeling of new composite based on PANI/PVK functionalized With single-walled carbon nanotubes for optoelectronic applications

We present a comparative experimental and theoretical study of the vibrational, optical, and electronic properties of polyaniline at both emeraladine leuco-emeraldine forms and PVK. Our objective is first to select the appropriate form of PANI to be linked with PVK to form a hybrid polymer matrix. Then, on the basis of quantum chemical calculations, we present a theoretical study of a hybrid composite PANI/PVK functionalized with lower radius (5, 5) chiral single-walled carbon nanotubes (SWCNTs). The relationship structure-properties of the resulting nano-composite are proved based on the conformational and optical study made from Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) using B3LYP method with 6-31-G(d) basis set. First, it has been demonstrated that the resulting interaction between PANI and PVK leads to more advantageous properties, such as good optical absorption compatibility with the solar emission spectrum. It has also been found that after the incorporation of SWCNTs into the matrix of PANI/PVK hybrid polymer, a good organization of SWCNTs via π-staking interaction is imposed by polyaniline sequences. However, PVK moieties are grafted on the sidewalls of SWCNTs. Finally, the electronic structure of the resulting hybrid nano-composite PANI/PVK/SWCNTs was carried out with the use of different electrodes on both sides.

Deep-Ultraviolet and Helicity-Dependent Raman Spectroscopy for Carbon Nanotubes and 2D Materials.

Recent progress of Raman spectroscopy on carbon nanotubes and 2D materials is reviewed as a topical review. The Raman tensor with complex values is related to the chiral 1D/2D materials without mirror symmetry for the mirror in the propagating direction of light, such as chiral carbon nanotube and black phosphorus. The phenomenon of complex Raman tensor is observed by the asymmetric polar plot of helicity-dependent Raman spectroscopy using incident circularly-polarized lights. First-principles calculations of resonant Raman spectra directly give the complex Raman tensor that explains helicity-dependent Raman spectra and laser-energy-dependent relative intensities of Raman spectra. In deep-ultraviolet (DUV) Raman spectroscopy with 266 nm laser, since the energy of the photon is large compared with the energy gap, the first-order and double resonant Raman processes occur in general k points in the Brillouin zone. First-principles calculation is necessary to understand the DUV Raman spectra and the origin of double-resonance Raman spectra. Asymmetric line shapes appear for the G band of graphene for 266 nm laser and in-plane Raman mode of WS2 for 532 nm laser, while these spectra show symmetric line shapes for other laser excitation. The interference effect on the asymmetric line shape is discussed by fitting the spectra to the Breit-Wigner-Fano lineshapes.

Nanocomposite Material Based on Polyvinyl Alcohol Modified with Carbon Nanotubes: Mechanism of Formation and Electronic Energy Structure

The physical chemistry of surface phenomena in polymers is an important issue when studying the interaction of polymers with solid surfaces. This is due to the fact that most of the modern polymer materials are heterogeneous systems with highly developed phase separation surfaces. An example of such materials can be reinforced plastic, filled thermoplastics, reinforced rubber, paint coatings, etc. Polymer adsorption at the boundary of the phase separation process in solids plays an important role in the reinforcing effect of fillers, adhesion, gluing and obtaining composite materials with high strength properties. Compositions based on polyvinyl alcohol (PVA) modified with carbon nanotubes (CNTs) can be used as an interesting and informative system for studying the structure and properties of polymer nanocomposites, especially in a highly oriented state. PVA has one of the simplest chemical structure among the polymers, containing a functional (hydroxyl) group capable of participating in interphase interactions. In turn, carbon nanotubes with unique strength properties are currently products of industrial production, which makes it possible to control and modify their properties. To prove the possibility of creating new composite materials with improved strength characteristics, the mechanisms of interaction between PVA and CNTs are studied by modeling the adsorption processes of a polymer fragment on the outer surface of single-layer carbon nanotubes of different chirality, performed within the framework of the modern DFT calculation method. The main adsorption characteristics of the process and the features of the electron energy structure of the resulting composite systems are determined.

Effects of Topological Parameters on Thermal Properties of Carbon Nanotubes via Molecular Dynamics Simulation

Due to their unique properties, carbon nanotubes (CNTs) are finding a growing number of applications across multiple industrial sectors. These properties of CNTs are subject to influence by numerous factors, including the specific chiral structure, length, type of CNTs used, diameter, and temperature. In this topic, the effects of chirality, diameter, and length of single-walled carbon nanotubes (SWNTs) on the thermal properties were studied using the reverse non-equilibrium molecular dynamics (RNEMD) method and the Tersoff interatomic potential of carbon–carbon based on the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). For the shorter SWNTs, the effect of chirality on the thermal conductivity is more obvious than for longer SWNTs. Thermal conductivity increases with increasing chiral angle, and armchair SWNTs have higher thermal conductivity than that of zigzag SWNTs. As the tube length becomes longer, the thermal conductivity increases while the effect of chirality on the thermal conductivity decreases. Furthermore, for SWNTs with longer lengths, the thermal conductivity of zigzag SWNTs is higher than that of the armchair SWNTs. Thermal resistance at the nanotube–nanotube interfaces, particularly the effect of CNT overlap length on thermal resistance, was studied. The simulation results were compared with and in agreement with the experimental and simulation results from the literature. The presented approach could be applied to investigate the properties of other advanced materials.

Infrared Light-Emitting Diodes Based on Chirality-Sorted Carbon Nanotube Films.

An important goal in carbon nanotube optoelectronics is to achieve a high-performance near-infrared light source. But there are still many challenges such as the purity of single-walled carbon nanotube (SWCNT) chirality, nonradiative defects, thin-film quality, and device structure design. Here, we realize infrared light-emitting diodes (LEDs) based on chirality-sorted (10, 5) SWCNT network films, which operate at a low bias voltage and emit at a telecom O band of 1290 nm. Asymmetric palladium (Pd) and hafnium (Hf) contacts are used as electrodes for hole and electron injection, respectively. However, the large Schottky barrier at the interface of the SWCNTs and the Hf electrode, primarily resulting from the polymer wrapped on the nanotube surface during the sorting process, leads to inefficient electron injection and thus a low electroluminescence efficiency. We find that the efficiency of electron injection can be improved by the local doping of the nanotubes with dielectric layers of YOX-HfO2, which reduces the Schottky barrier at the SWCNT/Hf interface. Accordingly, the (10, 5) SWCNT film-based LED achieves an external quantum efficiency of larger than 0.05% without any optical coupling structure. With further improvement, we expect that such an infrared light source will have great application potential in the carbon nanotube monolithic optoelectronic integrated system and on-chip optical interconnection, especially in the field of short-distance optical fiber communications and data center.

The effects of physical morphologies and strain rate on piezoelectric potential of boron nitride nanotubes: a molecular dynamics simulation

The growing demand for self-powered systems and the slow progress in energy storage devices have led to the emergence of piezoelectric materials as a promising solution for energy harvesting. This study aims to investigate the effects of chirality, length, and strain rate on the piezoelectric potential of boron nitride nanotubes (BNNTs) through molecular dynamics simulation. Accurate data and guidance are provided to explain the piezoelectricity of chiral nanotubes, as the piezoelectric potentials of these nanotubes have previously remained unclear. The present study focuses on calculating the effect of these parameters based on the atomic model. The observed results stem from the frequencies and internal deformations, as the axial frequencies and deformations exhibit more substantial modifications compared to transverse directions. The piezoelectricity was found to depend on chirality, with the order of BNNT piezoelectricity sufficiency being in the sequence of zigzag > chirality > armchair configurations. The length of the BNNTs was also found to influence piezoelectricity, while the strain rate had no effect. The results also indicate that BNNTs can generate power in the milliwatts range, which is adequate for low-power electronic devices and Internet of Things applications. This research provides valuable insights into the piezoelectricity of chiral nanotubes and offers guidance for designing efficient energy harvesting devices.

Pathway‐Dependent Self‐Assembly for Control over Helical Nanostructures and Topochemical Photopolymerization

AbstractPathway‐dependent self‐assembly, in which a single building block forms two or more types of self‐assembled nanostructures, is an important topic due to its mimic to the complexity in biology and manipulation of diverse supramolecular materials. Here, we report a pathway‐dependent self‐assembly using chiral glutamide derivatives (L or D‐PAG), which form chiral nanotwist and nanotube through a cooperative slow cooling and an isodesmic fast cooling process, respectively. Furthermore, pathway‐dependent self‐assembly can be harnessed to control over the supramolecular co‐assembly of PAG with a luminophore β‐DCS or a photopolymerizable PCDA. Fast cooling leads to the co‐assembled PAG/β‐DCS nanotube exhibiting green circularly polarized luminescence (CPL), while slow cooling to nanofiber with blue CPL. Additionally, fast cooling process promotes the photopolymerization of PCDA into a red chiral polymer, whereas slow cooling inhibits the polymerization. This work not only demonstrates the pathway‐dependent control over structural characteristics but also highlights the diverse functions emerged from the different assemblies.

Pathway-Dependent Self-Assembly for Control over Helical Nanostructures and Topochemical Photopolymerization.

Pathway-dependent self-assembly, in which a single building block forms two or more types of self-assembled nanostructures, is an important topic due to its mimic to the complexity in biology and manipulation of diverse supramolecular materials. Here, we report a pathway-dependent self-assembly using chiral glutamide derivatives (L or D-PAG), which form chiral nanotwist and nanotube through a cooperative slow cooling and an isodesmic fast cooling process, respectively. Furthermore, pathway-dependent self-assembly can be harnessed to control over the supramolecular co-assembly of PAG with a luminophore β-DCS or a photopolymerizable PCDA. Fast cooling leads to the co-assembled PAG/β-DCS nanotube exhibiting green circularly polarized luminescence (CPL), while slow cooling to nanofiber with blue CPL. Additionally, fast cooling process promotes the photopolymerization of PCDA into a red chiral polymer, whereas slow cooling inhibits the polymerization. This work not only demonstrates the pathway-dependent control over structural characteristics but also highlights the diverse functions emerged from the different assemblies.