Single-walled Nanotubes Research Articles

Recent Advancements in Morphologies of TiO2 Nanotube Layers and Their Photocatalytic Performance

Self-organized TiO2 nanotubes arrays, formed by electrochemical anodization of Ti, have attracted tremendous scientific and technological attention, due to their remarkable properties such as the tunability of dimensions, their directionality, high surface area, low density, and ability to absorb significant amount of incident light [1,2].The most widely used electrolyte for the synthesis of TiO2 nanotube layers is based on ethylene glycol containing small amounts of water and fluoride ions. However, nanotubes prepared in these electrolytes present a double-walled structure, with the outer wall consisting of almost pure TiO2 and the inner wall consisting of TiO2 contaminated with carbon and fluoride species [3,4]. In the recent years, the selective etching of the inner nanotube wall on Ti layer enabled synthesis of single-wall nanotubes that showed a superior photo-electrochemical performance compared to their double-walled counterparts [5]. An extensive etching enabled also the synthesis of single tube powders, which could be effectively decorated with Fe3O4 nanoparticles to act as magnetically guidable photocatalyst [6,7].The presentation will focus on the influence of all these nanotube morphologies on the photocatalytic degradation in the liquid phase. In particular, we will discuss, how the annealing temperature of single nanotubes influences their photocatalytic performance [7] and how the wall thickness of the single wall nanotubes can be optimized for the best performance [8]. Experimental details and photocatalytic results will be presented and discussed.

Detection and Isolation of Isomerically Pure C120 Fullertubes

The emergence of macroscopic amounts of C60 fullerenes and carbon nanotubes in the 1990s has led to an explosion of growth in new structures of carbon nanomaterials. Over the last decades, there have been theoretical predictions of a particular “hybrid” family of mathematical structures. Fullertubes represent a new area of fundamental research in molecular carbon. They are similar to fullerenes in structure, but with increasingly long cylindrical, single-wall nanotube belts in the middle of the molecules. These nanotube belts are similar to single-layer, rolled graphene. In 2020 we published the isomeric separation and characterization of [5,5] C90-D5h fullertubes and [5,5] C100-D5d fullertubes. In this presentation, we will report and discuss the first isolation and UV-vis characterization of pristine and unfunctionalized C120 fullertubes. The separation and isolation of larger fullertubes is a two-step purification process. First, the spheroidal fullerene contaminants must be removed from the carbon soot extract to enrich the sample in fullertubes. Then in the second step, HPLC is used to achieve isomerically purified and pristine fullertubes. Efforts to characterize these newly isolated C120 fullertubes are currently underway.

Water Flow in Single-Wall Nanotubes: Oxygen Makes It Slip, Hydrogen Makes It Stick.

Experimental measurements have reported ultrafast and radius-dependent water transport in carbon nanotubes which are absent in boron nitride nanotubes. Despite considerable effort, the origin of this contrasting (and fascinating) behavior is not understood. Here, with the aid of machine learning-based molecular dynamics simulations that deliver first-principles accuracy, we investigate water transport in single-wall carbon and boron nitride nanotubes. Our simulations reveal a large, radius-dependent hydrodynamic slippage on both materials, with water experiencing indeed a ≈5 times lower friction on carbon surfaces compared to boron nitride. Analysis of the diffusion mechanisms across the two materials reveals that the fast water transport on carbon is governed by facile oxygen motion, whereas the higher friction on boron nitride arises from specific hydrogen–nitrogen interactions. This work not only delivers a clear reference of quantum mechanical accuracy for water flow in single-wall nanotubes but also provides detailed mechanistic insight into its radius and material dependence for future technological application.

Band gap regulation and a selective preparation method for single-walled silicon carbide nanotubes

By using the first-principles density functional method, the electronic properties of single-walled silicon carbide (SiC) nanotubes were systematically studied, especially the band gap turning by the chiral angle and tube diameter. We propose a new strategy for preparing SiC nanotubes, which can be used to prepare single-walled SiC nanotubes with the expected band gap, named “selective shear suture method”. This research provides a new way to synthesize high-quality materials for nano-scale semiconductors, electrical devices and non-silicon-based chips. In particular, the selective defects in the preparation of single-walled nanotubes by electron beam cutting are theoretically solved. This study also provides useful theoretical guidance for the selective preparation of various single-walled nanotubes.

Reproductive and Developmental Nanotoxicity of Carbon Nanoparticles.

The presented review aims to summarize the knowledge regarding the reproductive and developmental toxicity of different types of carbon nanoparticles, such as graphene, graphene oxide, multi- and single-walled nanotubes, fullerenes, and nanodiamonds. Carbon nanoparticles have unique chemical and physical properties that make them an excellent material that can be applied in many fields of human activity, including industry, food processing, the pharmaceutical industry, or medicine. Although it has a high degree of biocompatibility, possible toxic effects on different tissue types must also be taken into account. Carbon nanoparticles are known to be toxic to the respiratory, cardiovascular, nervous, digestive system, etc., and, according to current studies, they also have a negative effect on reproduction and offspring development.

Monte Carlo investigation of phase changes and the order of transition of Ising modeled single-walled nanotube

We present the Monte-Carlo analysis report for the magnetic response of the single-walled nanotube using the Metropolis and Wang Landau algorithms. Our nanotube architecture uses the spin half Ising model with nearest neighbors interaction. We find the phase changes from ferromagnetic/anti ferromagnetic to paramagnetic by modifying the system interaction parameters. We determine the transition temperatures for varying interaction strength in the absence of the magnetic field. We find the transition temperature changes with the external magnetic field for a fixed interaction strength. Our study confirmed that the transition from ferromagnetic/anti ferromagnetic to paramagnetic is second order.

Potential of novel self-assembled functionalized carbon nanotubes for selective tumor targeting.

Conventional cancer therapies are associated with toxicity toward healthy cells, which need to be addressed by novel therapeutic approaches. US2021/0230592 patent application discloses a carbon nanotube-based approach for tumor targeting, wherein a self-assembling single-wall nanotube complex has been developed and functionalized to deliver a molecule to a cancerous cell. The radiolabeled nanotubes exhibited markedly reduced toxicity as they did not depict any 'over toxicity' up to radioactivity value of 1350 nCi. The single-wall carbon nanotube conjugates were covalently connected to several chelators, therapeutic or diagnostic radionuclides, and showed promising results in the effective cancer management. Besides, this invention with further modifications paves an ideal pathway to researchers in effective diagnosis and treatment of cancer.

Structural and optical behavior of single-walled and multi-walled boron nitride nanotubes

Using Density Functional Theory (DFT), the structural, electrical, and optical properties of single-walled boron nitride nanotubes (SWBNNTs), double-walled boron nitride nanotubes (DWBNNTs), and multi-walled boron nitride nanotubes (MWBNNTs) was investigated. The calculated cohesive energy shows that the double-walled and multi-walled BNNTs are more stable than the single-walled BNNTs they are made up of. All of the simulated nanotubes have semiconducting behavior, according to the electronic properties. The interaction between the 2pz orbitals of the internal and external nanotubes reduces the band gaps (Eg) of the DWBNNTs and MWBNNTs. Furthermore, in the 5.8 to 6.5 eV energy range, the z component of the refractive index for SWBNNTs approaches a minimum. DWBNNTs and MWBNNTs, on the other hand, have a nz minimum in the lower energy range (=4.8–5.5 eV). SWBNNTs (4, 4) have an optical absorption similar to single-walled carbon nanotubes. SWBNNTs (4, 4) have an optical absorption similar to single-walled carbon nanotubes. Moreover, the z component of the optical absorption fell from 600,000 cm−1 for SWBNNTs (4, 4) to 30,000 cm−1 for MWBNNTs (4, 4) @ (8, 8) @ (12, 12).

Structural and electronic properties of single- and double-walled BeN4 nanotubes: First-principles calculations

The structural and electronic properties of single- and double-walled BeN4 nanotubes are studied using first-principles calculations. Two sets of single-walled BeN4 nanotubes, namely, (n,0) and (0,n) are formed by rolling up the BeN4 sheets along two different sides into a cylinder. The cohesive energies and molecular dynamics simulations confirm the thermal stability of BeN4 nanotubes. The (n,0) BeN4 nanotubes exhibit semiconducting properties with non-zero band gaps. Their band gaps are dependent on the tube size. The band gap of (0,n) BeN4 nanotubes is not considerable and these tubes behave as semimetals. The double-walled BeN4 nanotubes with interlayers larger than 3 Å are energetically favorable. These nanotubes show semiconducting and semimetallic properties depending on their chirality. The results propose BeN4 nanotubes with various electronic properties to use in future nanoelectronic devices.

Carbon Nanotubes for the Optical Far-Field Readout of Processes That Are Mediated by Plasmonic Near-Fields

As science progresses at the nanoscopic level, it becomes more and more important to comprehend the interactions taking place at the nanoscale, where optical near-fields play a key role. Their phenomenology differs significantly from the propagative light we experience at the macroscopic level. This is particularly important in applications such as surface-enhanced spectroscopies for single-molecule detection, where often the optimization of the plasmonic structures and surfaces relies on far-field characterizations. The processes dominating in the far-field picture, though, are not the same dominating in the near-field. To highlight this, we resort to very simple metallic systems: Isolated gold nanorods in solution. We show how single-walled nanotubes can be exploited to read out processes occurring at the near-field level around metallic nanoparticles and make the information accessible in the far-field region. This is implemented by monitoring the spectral profile of the enhancement of the photoluminescence and Raman signal of the nanotubes for several excitation wavelengths. Through this excitation-resolved study, we show that the far-field optical read-out detects the transversal and longitudinal dipolar plasmonic oscillations of gold nanorods, whereas the near-field read-out through the nanotubes reveals other mechanisms to dominate. The spectral position of the maximum enhancement of the optical near-field mediated signals are located elsewhere than the far-field bands. This dichotomy between near-field and far-field response should be taken into account when optimizing plasmonic nanostructures for applications such as surface-enhanced spectroscopies.

Liquid phase exfoliation of nonlayered non-van der Waals iron trifluoride (FeF3) into 2D-platelets for high-capacity lithium storing cathodes

Developing high-performance cathode materials for lithium-ion batteries is necessary to maximise both energy and power density. One promising cathode material is iron trifluoride (FeF3) having a high theoretical capacity of 712 mAh/g, although achieving this value experimentally is challenging. Our previous works has shown that achievable capacity can be maximised when active materials are in a two-dimensional (2D) form. Liquid-phase exfoliation (LPE) method seems intuitively inappropriate to produce 2D-platelets from non-layered non-Van der Waals (non-VdW) bulk materials. However, in this manuscript, we show that bulk non-layered non-VdW material, FeF3 can be converted from its 3D form to quasi-2D platelets. The XRD, TEM and elemental analysis showed the structure and stoichiometry of these platelets to be similar to that of bulk material. Interestingly, although AFM showed majority of platelets to be quasi-2D, it revealed the platelet aspect-ratio to be thickness dependent, falling from ∼12 for the thinnest platelets to ∼1 for the thickest ones. Lithium storage experiments showed that, once coated in carbon and mixed with single walled nanotubes, FeF3 platelets display good Li storage capability coupled with reasonable stability. At very low currents, this material displays an active-mass normalised capacity of ∼700 mAh/g, very close to the theoretical value. However, the capacity fell off at higher currents with detailed analysis implying FeF3 cathodes in general to display poor rate performance due to low ionic diffusivity.

Single-Walled Black Phosphorus Nanotube as a NO2 Gas Sensor

An ab initio density functional theory study on the candidacy of single-walled black phosphorus nanotubes (BPNTs) towards sensing several common toxic gas molecules (NH3, CO, NO, NO2, and SO2) was conducted. Various adsorption characteristics, including the geometry, adsorption energy, charge transfer, band structure, and curvature effect were examined. Compared with MLBP, BPNTs are found to generally exhibit similar adsorption energy towards these molecules, whereas show selectively much stronger interaction with NO2. Analysis of charge density difference and band structure also indicates the electronic properties of BPNTs are significantly altered after the adsorption of NO2: transferring an indirect band gap of ~0.3 eV for pristine (0, 9)BPNT to a metallic system. These facts collectively indicate the higher capability, sensitivity, and selectivity of BPNTs in the detection of NO2 compared to its planar counterpart. Moreover, the NO2 adsorption is found to be influenced by the curvature of BPNTs. Overall, findings from the present study indicate that BPNTs may serve as potential building blocks for high-performance gas sensors towards NO2 sensing.

Structural and electronic properties of double-walled G-C3N4 nanotubes: a density functional theory study

In the present work, we investigated the geometric, electronic, and photocatalytic properties of g-C3N4 single-walled nanotube (SWCNNTs) and g-C3N4 double-walled nanotubes (DWCNNTs). The negative strain energy indicates that the SWCNNTs have a stable structure, while the most stable combination in the DWCNNT is (6, 0)@(12, 0). The energy band gaps of (n, 0) SWCNNTs increase while that of (n, n) SWCNNTs decrease as the diameter increase. Moreover, the calculated nanotubes have the ability of photocatalytic water splitting, and the valance band maximum of nanotubes are much lower than that of the monolayer, indicating that the nanotubes have better oxidation capacity than the monolayer. On the other hand, our calculations show that DWCNNTs have type II band alignment with a band gap width significantly smaller than that of SWCNNTs. Interestingly, DWCNNT exhibited a smaller effective mass of electrons than SWCNNTs, which is beneficial to electron migration. Therefore, the construction of nanotube is an effective way to improve the photocatalytic performance of g-C3N4 monolayer materials.

The Exchange-Correlation Effects on the Electronic Bands of Hybrid Armchair Single-Walled Carbon Boron Nitride Nanostructure

This study investigates the effect of exchange-correlation on the electronic properties of hybridized hetero-structured nanomaterials, called single-walled carbon boron nitride nanotubes (SWCBNNT). A first principles (ab initio) method implemented in Quantum ESPRESSO codes, together with different parametrizations (local density approximation (LDA) formulated by Perdew Zunga (PZ) and the generalized gradient approximation (GGA) proposed by Perdew–Burke–Ernzerhof (PBE) and Perdew–Wang 91 (PW91)), were used in this study. It has been observed that the disappearance of interface states in the band gap was due to the discontinuity of the π–π bonds in some segments of SWCNT, which resulted in the asymmetric distribution in the two segments. This work has successfully created a band gap in SWCBNNT, where the PBE exchange-correlation functional provides a well-agreed band gap value of 1.8713 eV. Effects of orbitals on electronic properties have also been studied elaborately. It has been identified that the Py orbital gives the largest contribution to the electrical properties of our new hybrid SWCBNNT nanostructures. This study may open a new avenue for tailoring bandgap in the hybrid heterostructured nanomaterials towards practical applications with next-generation optoelectronic devices, especially in LED nanoscience and nanotechnology.

Carbon Nanotube/Polymer Coaxial Cables with Strong Interface for Damping Composites and Stretchable Conductors

AbstractCarbon nanotube (CNT) fibers have the potential to serve as continuous nano‐fillers for structural and functional composite materials, yet there exists the interfacial problem that has hindered the development of continuous fiber reinforced composites for a long time. Here, a method to overcome this challenge by coating a thick CNT sponge around a single‐walled nanotube (SWNT) fiber is presented, and then infiltrating polymers into the sponge to construct a SWNT@polymer coaxial cable. It has been found that the residual stress‐induced deposition of amorphous carbon as an intermediate layer between the underlying SWNT fiber and the subsequently coated multi‐walled nanotube (MWNT) sponge plays a key role in interfacial properties, and together with well‐dispersed CNT in the polymer matrix, a superior interfacial shear strength (>12 MPa), enhanced tensile strength and toughness is achieved. These coaxial cables demonstrate high mechanical damping ability and can serve as stretchable conductors maintaining high electrical conductivity during large‐strain cyclic deformation. These results indicate a promising route toward developing continuous CNT fiber‐based composites with wide applications as structural and multi‐functional composite materials.

Single-walled silicon nanotube as an exceptional candidate to eliminate SARS-CoV-2: a theoretical study

In this work, computational chemistry methods were used to study a silicon nanotube (Si192H16) as possible virucidal activity against SARS-CoV-2. This virus is responsible for the COVID-19 disease. DFT calculations showed that the structural parameters of the Si192H16 nanotube are in agreement with the theoretical/experimental parameters reported in the literature. The low energy gap value (0.29 eV) shows that this nanotube is a semiconductor and exhibits high reactivity. For nanomaterials to be used as virucides, they need to have high reactivity and high inhibition constant values. Therefore, the adsorption of 3O2 and H2O on the surface of Si192H16 (Si192H16@O2-H2O) was performed. In this process, the formation and activation energies were −51.63 and 16.62 kcal/mol, respectively. Molecular docking calculations showed that the Si192H16 and Si192H16@O2H-OH nanotubes bind favorably on the receptor-binding domain of the SARS-CoV-2 spike protein with binding energy of −11.83 (Ki = 2.13 nM) and −11.13 (Ki = 6.99 nM) kcal/mol, respectively. Overall, the results obtained herein indicate that the Si192H16 nanotube is a potential candidate to be used against COVID-19 from reactivity process and/or steric impediment in the S-protein. Communicated by Ramaswamy H. Sarma

Electronic and optical properties of ultra-small diameter armchair carbon and boron nitride nanotubes by PBE, TB-mBJ and YS-PBE0 functionals

We have investigated the electronic and optical properties of ultra-small (3,3), (4,4) and (5,5) armchair single walled nanotubes carbon (C-SWNTs) and boron nitride (BN-SWNTs) using three density functional methods of different categories, namely, PBE, TB-mBJ and hybrid functional YS-PBE0. A density functional theory (DFT) within the full-potential linearized augmented-plane wave (FP-LAPW) method, was used to study the structures, electronic and optical properties of these nanotubes. The calculation of optical properties has been performed under electric fields polarized both parallel and perpendicular with respect to the nanotube axis. The results show that the hybrid functional YS-PBE0 perform the best for calculations of band gap of BN-SWNTs (5.27–5.54 eV), while for C-SWNTs the PBE and TB-mBJ functionals obtain band gap range (0.16–0.28 eV) with smaller errors compared to experimental values and confirming the semiconducting behavior of the studied C-SWNTs. The dielectric function is anisotropic for all tubes and is larger in the parallel direction. The results show also that for C-SWNTs, the static refractive index is higher than those of BN-SWNTs and it has an inverse correlation with the C-SWNTs diameter. This proves that for optoelectronic applications, it is improve to use the BN-SWNTs doped than intrinsic.

Density functional theory method for twisted geometries with application to torsional deformations in group-IV nanotubes

We present a real-space formulation and implementation of Kohn-Sham Density Functional Theory suited to twisted geometries, and apply it to the study of torsional deformations of X (X = C, Si, Ge, Sn) nanotubes. Our formulation is based on higher order finite difference discretization in helical coordinates, uses ab initio pseudopotentials, and naturally incorporates rotational (cyclic) and screw operation (i.e., helical) symmetries. We discuss several aspects of the computational method, including the form of the governing equations, d ils of the numerical implementation, as well as its convergence, accuracy and efficiency properties.The technique presented here is particularly well suited to the first principles simulation of quasi-one-dimensional structures and their deformations, and many systems of interest can be investigated using small simulation cells containing just a few atoms. We apply the method to systematically study the properties of single-wall zigzag and armchair group-IV nanotubes in the range of (approximately) 1 to 3 nm radius, as they undergo twisting. For the range of deformations considered, the mechanical behavior of the tubes is found to be largely consistent with isotropic linear elasticity, with the torsional stiffness, ktwist, varying as the cube of the nanotube radius. Furthermore, for a given tube radius, ktwist is seen to be highest for carbon nanotubes and the lowest for those of tin, while nanotubes of silicon and germanium are found to have intermediate values of this quantity close to each other. We also describe different aspects of the variation in electronic properties of the nanotubes as they are twisted. In particular, we find that akin to the well known behavior of armchair carbon nanotubes, armchair nanotubes of silicon, germanium and tin also exhibit bandgaps that vary periodically with imposed rate of twist, and that the periodicity of the variation scales in an inverse quadratic manner with the tube radius. These examples highlight the utility of the proposed method in the accurate and efficient computational characterization of important nanomaterials from first principles.

Chemi-Inspired Silicon Allotropes-Experimentally Accessible Si9 Cages as Proposed Building Block for 1D Polymers, 2D Sheets, Single-Walled Nanotubes, and Nanoparticles.

Numerous studies on silicon allotropes with three-dimensional networks or as materials of lower dimensionality have been carried out in the past. Herein, allotropes of silicon, which are based on structures of experimentally accessible [Si9]4− clusters known as stable anionic molecular species in neat solids and in solution, are predicted. Hypothetical oxidative coupling under the formation of covalent Si–Si bonds between the clusters leads to uncharged two-, one- and zero-dimensional silicon nanomaterials not suffering from dangling bonds. A large variety of structures are derived and investigated by quantum chemical calculations. Their relative energies are in the same range as experimentally known silicene, and some structures are even energetically more favorable than silicene. Significantly smaller relative energies are reached by the insertion of linkers in form of tetrahedrally connected Si atoms. A chessboard pattern built of Si9 clusters bridged by tetrahedrally connected Si atoms represents a two-dimensional silicon species with remarkably lower relative energy in comparison with silicene. We discuss the structural and electronic properties of the predicted silicon materials and their building block nido-[Si9]4– based on density functional calculations. All considered structures are semiconductors. The band structures exclusively show bands of low dispersion, as is typical for covalent polymers.

The Edge-Hyper-Wiener Index of Zigzag Single-Walled Nanotubes

A topological index is a numerical value associated with a graph structure that has some correlation with corresponding physical property, chemical reaction or biological activity. To achieve much information and less degeneracy, many kinds of topological indices are defined on distances, degrees, countings, spectrums, etc. In this paper, we mainly study the edge-hyper-Wiener which is the distance-based index. It is the sum of the distances and the square of distances between all pairs of edges. Further, the exact expression of the edge-hyper-Wiener index of the zigzag single-walled nanotubes is given.