Nanotube Lattice Research Articles

Bimetallic Ni‐Co Supported on Nitrogen‐Doped Carbon Nanotubes For Prox Reaction

AbstractHydrogen is a key component for a successful energy transition on a large scale since it boasts remarkable energy efficiency. Currently, H2 is mainly obtained through steam reforming of natural gas or hydrocarbons and low‐carbon alcohols but contains approximately 2 % CO, a contaminant detrimental to H2 fuel cells. Herein, an N‐doped carbon nanotube was prepared via the soft nitriding method to support nickel and cobalt for the PROX‐CO as the main reaction for hydrogen purification. The most efficient condition was achieved when the reaction temperature reached 250 °C and the Ni and Co loading rate was 7.5 %. In this situation, the CO2 selectivity reached almost 33 %, and CO conversion was 61 %. Regarding CO conversion among bimetallic catalysts at 250 °C a minimal variation occurred and the catalyst 10Ni/N‐CNTs slightly outperformed (64.4 %). The effect of N‐doping on the carbon nanotube's structure was also revealed. Nitrogen atoms incorporated into the lattice of carbon nanotubes impart an electron‐donor character. Consequently, Co oxide reduction to the metallic phase occurred at significantly lower temperatures compared to other supports such as SiO2, Al2O3, and graphene. For the bimetallic catalysts, the strong metal‐support interaction facilitated obtaining different oxide and metallic phases at milder temperatures.

Evidence of the Electrochemical Ca2+ Intercalation in Anatase Nanotubes

AbstractHere, we demonstrate the electrochemical intercalation of Ca2+ ions within the lattice of anatase nanotubes (a‐NTs) synthesized by hydrothermal treatment of TiO2/NaOH precursors followed by Na+/H+ ion exchange and H2O‐loss at high temperature in air. Scanning electron microscopy, X‐ray diffraction, and Raman spectroscopy confirm the formation of nanosized anatase, whereas transmission electron microscopy highlights the formation of nanotubular morphologies with an average diameter of 10 nm. TiO2 electrodes are able to deliver reversible specific capacities in aprotic batteries vs. calcium metal or in hybrid configurations vs. capacitive activated carbon using aprotic electrolytes (i. e., Ca(BH4)2 in tetrahydrofuran or Ca(TFSI)2 in dimethoxyethane, respectively). The electrochemical intercalation of Ca2+ ions into the anatase lattice is confirmed by X‐ray absorption spectroscopy in close comparison with Na+ and Li+ intercalations. Ca2+ incorporation leads to the partial amorphization of the TiO2 lattice despite the limited Ca/Ti ratio (i. e., 0.09) obtained in discharge. The analysis of the extended X‐ray absorption fine structure region allows the determination of the local structure of the incorporated Ca2+ ions and confirms that a disordered environment is obtained after the electrochemical reaction.

Extremal topological indices of some nanostructures

In this work, general formulas of degree-based and neighborhood degree sum-based topological indices for a 2D lattice of H-Naphtalenic nanotubes and pent-heptagonal nanosheets are determined. As an example, six neighborhood degree sum-based topological indices are computed using the obtained formula. Furthermore, the extremal cases of these nanostructures with a fixed number of blocks are characterized for a given degree-based or neighborhood degree sum-based topological index. Also a visual comparison of these indices is shown. Additionally, it is demonstrated how beneficial the indices are for representing structure-property relationships.

The Effect of Exchange Interaction on Phase Transition Behavior of Magnetic Nanotubes

In this paper, the phase diagram of the Blume-Capel model under exchange interaction between lattice points in different positions in magnetic nanotube lattice is studied with effective field theory. The research shows that the interaction between nearest neighbors and the lattice field strength strongly influences the system’s three critical points and phase transition temperature. Under certain conditions, there are three critical points in the system. That is, the relationship between the crucial points is linear from the second-order phase transition to the first-order phase transition. First-order phase transition replaces second-order phase transition in the system’s phase transition. The findings demonstrate that exchange interaction significantly affects the system’s phase transition, and they offer a theoretical framework for both industrial production and experimental study.

Identical and nonidentical superlattice on the surface of nanotubes: Specific heat and magnetization

The thermodynamic and magnetic properties of electrons in superlattices on the surface of a nanotube in a longitudinal magnetic field are investigated. It is shown that the specific heat of nondegenerate electron gas in superlattice on the surface of a nanotube oscillates with the change in the magnetic flux. With the increase in effective mass, the magnetization in identical and nonidentical superlattices on the surface of a nanotube are close to each other. Magnetization has a “saw-tooth” form as a function of a magnetic field. For the lattice of nanotubes with two different radii, ordinary compensation points, at which the magnetization vanishes at fixed values of the magnetic field strength, are found.

Quantum Coupling of Two Atomic Defects in a Carbon Nanotube Semiconductor.

Chemical defects can create organic color centers in the graphitic lattice of single-walled carbon nanotubes. However, the underlying physics remains somewhat of a mystery. Here we show that two sp3 atomic defects can interact with each other in a way reminiscent of atoms bonding to form molecules. Each defect creates an atom-like mid-gap state within the band gap of the nanotube semiconductor. Two such defects, when brought close to each other, interact to form a split pair of orbitals akin to two hydrogen atoms covalently bonding to form a H2 molecule. This unexpected finding may help in understanding the nature of atomic defects in solids and provide a fresh perspective to the engineering of these color centers.

Compensation points in the lattice of semiconductor nanotubes

In the present work, we investigated the thermodynamic properties of the lattice formed by noninteracting nanotubes using a single-walled nanotube model in a longitudinal magnetic field. We show that the specific heat of nondegenerate electron gas in semiconductor nanotubes changes from kB/2 to kB as temperature increases. Magnetization has a “saw-tooth” form as a function of the magnetic field. For the lattice of nanotubes with two different radii, we found ordinary compensation points, points at which the magnetization vanishes at fixed values of the magnetic field strength.

Heat capacity and magnetization of identical and non-identical semiconductor nanotubes

In the present work, we investigated the thermodynamic properties of the lattice formed by non-interacting nanotubes using a single-walled nanotube model in a longitudinal magnetic field. Using the energy spectrum, we derived the exact analytic expression for the single-particle partition function and used it to determine the magnetic moment and specific heat. Magnetization has a “saw-tooth” form as a function of the magnetic field. For the lattice of nanotubes with two different radii, we found ordinary compensation points, points at which the magnetization vanishes at fixed values of the magnetic field strength.

DNA-guided lattice remodeling of carbon nanotubes.

Covalent modification of carbon nanotubes is a promising strategy for engineering their electronic structures. However, keeping modification sites in registration with a nanotube lattice is challenging. We report a solution using DNA-directed, guanine (G)-specific cross-linking chemistry. Through DNA screening we identify a sequence, C3GC7GC3, whose reaction with an (8,3) enantiomer yields minimum disorder-induced Raman mode intensities and photoluminescence Stokes shift, suggesting ordered defect array formation. Single-particle cryo-electron microscopy shows that the C3GC7GC3 functionalized (8,3) has an ordered helical structure with a 6.5 angstroms periodicity. Reaction mechanism analysis suggests that the helical periodicity arises from an array of G-modified carbon-carbon bonds separated by a fixed distance along an armchair helical line. Our findings may be used to remodel nanotube lattices for novel electronic properties.

Quantum Defects: What Pairs with the Aryl Group When Bonding to the sp2 Carbon Lattice of Single-Wall Carbon Nanotubes?

Aryl diazonium reactions are widely used to covalently modify graphitic electrodes and low-dimensional carbon materials, including the recent creation of organic color centers (OCCs) on single-wall carbon nanotube semiconductors. However, due to the experimental difficulties in resolving small functional groups over extensive carbon lattices, a basic question until now remains unanswered: what group, if any, is pairing with the aryl sp3 defect when breaking a C═C bond on the sp2 carbon lattice? Here, we show that water plays an unexpected role in completing the diazonium reaction with carbon nanotubes involving chlorosulfonic acid, acting as a nucleophilic agent that contributes -OH as the pairing group. By simply replacing water with other nucleophilic solvents, we find it is possible to create OCCs that feature an entirely new series of pairing groups, including -OCH3, -OC2H5, -OC3H7, -i-OC3H7, and -NH2, which allows us to systematically tailor the defect pairs and the optical properties of the resulting color centers. Enabled by these pairing groups, we further achieved the synthesis of OCCs with sterically bulky pairs that exhibit high purity defect photoluminescence effectively covering both the second near-infrared window and the telecom wavelengths. Our studies further suggest that these diazonium reactions proceed through the formation of carbocations in chlorosulfonic acid, rather than a radical mechanism that typically occurs in aqueous solutions. These findings uncover the unknown half of the sp3 defect pairs and provide a synthetic approach to control these defect color centers for quantum information, imaging, and sensing.

Synthesis of Fe-doped TiO2 nanotubes by hydrothermal method for photodegradation of methylene blue from aqueous solutions

Fe-doped TiO2 nanotubes were prepared by hydrothermal method using ferric nitrate and commercial TiO2 powder. The obtained materials were characterized by means of XRD, TEM, BET, FT-IR and UV-Vis-DRS. The photocatalytic activity was evaluated based on photodegradation of methylene blue under visible light irradiation. The results show that Fe3+ ions might incorporate into the lattice of TiO2 nanotubes. Fe-doped TiO2 materials showed narrower band gap energies, higher specific surface areas, more hydroxyl groups on the surface and significantly improved photocatalytic activity. The optimum Fe doping at the molar ratios of Fe/Ti = 0.5% showed the highest photocatalytic activity and was 3.08 times higher than that of undoped TiO2. The kinetic studies showed the decomposition of MB followed pseudo first-order kinetics with the rate constant were determined kapp = 5.64×10-2 min−1.

Synergistic effect of bi-phased and self-doped Ti+3 on anodic TiO2 nanotubes photoelectrode for photoelectrochemical sensing

Inclusive detection of organic compounds in aqueous solutions is a promising yet challenging approach for photoelectrochemical (PEC) sensors. In this work, the combined factors of crystalline phase change and Ti3+ self-doping were introduced to some fabricated anodic TiO2 nanotubes (ATNTs) to improve their efficacy as potential PEC sensors. Several TiO2 electrodes were effectively fabricated according to the variation of the factors as mentioned above via dual-step anodization process of a Ti foil, followed by high-temperature annealing under a hydrogen reduction atmosphere. As evidenced by XPS and wettability tests, oxygen vacancies were created in the crystalline lattice of TiO2 nanotubes as shallow donors’ levels which boosted the electronic conductivity of ATNTs. This enhancement in the electronic conductivity was endorsed and assessed by photoelectrochemical (PEC) properties performance testing. The PEC performance results indicated that bi-phased (anatase and rutile) Ti3+-ATNTs photo-electrode annealed at 600 °C under hydrogen reduction synergistically prompted the photoelectrochemical activity. In addition, their corresponding photocurrent was 2-fold greater than that of the other fabricated ATNTs photo-electrodes. Most prominently, the bi-phased Ti3+- ATNTs photo-electrode degraded more minor concentrations of organic solutions with a broader linear detection range. This recommends that the bi-phase Ti3+- ATNTs photo-electrode may serve as a robust sensor for the PEC identification of selective organic solutions under solar light irradiation. These designed PEC sensors have demonstrated their promising feasibility and selectivity for glucose, KHP, succinic acid, and malonic acid; hence this suggests their bright future in detecting biomedical samples for clinical diagnosis.

HCT116 Cells Cytotoxic Response to Multifuctionalized 5- Fluorouracil MWCNTs Conjugates In Colorectal Cancer

Nanomaterials are the foundations of Nanotechnology, which are measured in nanoscales, Carbon nanotubes are one of the interesting nanomaterials, studied for over 25 years because of their superlative properties such as high surface area, electrical and thermal conductivity, high biocompatibility, flexibility, resistance to corrosion and nanosize. According to research, carbon nanotubes are applied in sensing, water treatment, and drug delivery, mainly used to deliver the anticancer drugs. In our work, functionalization of multi walled carbon nanotubes done by covalent and non-covalent functionation methods, covalent functionalization showed better dispersing efficiency in aqueous medium and compatible with biological systems with damaging the crystal lattice of carbon nanotubes. Non covalent functionalization helps to derivatized with active compounds, surface adsorption or attachment of various molecules or antibodies, which subsequently helps in targeting the site and to produce therapeutic effects. Different formulations prepared by functionalized MWCNTs and multiple functionalization of MWCNTs done by binding the drug and antibodies to prepare functionalized MWCNTs 5-Fluorouracil complexes. The Cytotoxicity assay was carried out for the obtained new targeting formulations to analyze the effect of all the formulations on HCT116 cell line. The percentage death was determined based on the viability of the cells in the appropriate vehicle controls. In this study, we report the successful functionalization, binding of 5 Fluorouracil, antibodies to MWCNTs, and cells viability of all prepared formulations for the development of novel carbon based anticancer drug delivery system. Functionalized MWCNTs-5-Fluorouracil antibodies composite at concentration above 2.5 µg/mL exhibited ≥ 50% cytotoxicity post normalization with compound control to negate precipitation observed with the compound. All the formulations showed the precipitations indicating antitumor activity and biocompatibility.

Identification of vacancy defects in carbon nanotubes using vibration analysis and machine learning

Point vacancies are the most common defects in a carbon nanotube (CNT) lattice. However, there is no standard technique to identify these defects. Moreover, the effect of such vacancies on the vibrational properties of CNTs is unknown. Therefore, this paper presents the first-ever technique for identification of vacancy defects in single-walled carbon nanotubes (SWCNT) using their vibrational analyses and machine learning. 240 SWCNT samples were modelled using molecular-structural-mechanics-approach and their modes obtained using finite element analyses. Then, an analytical expression for fundamental vibration frequency of a vacancy defective SWCNT was derived using log-linear multiple regression. This frequency is found to decrease with: (i) increase in the magnitude of point vacancies; (ii) decrease in diameter; and (iii) increase in length. A polynomial support vector machine (SVM) was developed that successfully classifies pristine and vacancy defective SWCNT samples at test accuracy greater than 90%. The proposed technique for identification of point vacancies combines the developed SVM classification with inverse estimation using the derived expression. This technique will be useful for the most crucial characterization of SWCNTs, i.e., characterizing pristine and vacancy defective samples. The derived expression will be useful in predicting vibration response of vacancy defective SWCNTs, and deciding their applications.

Development of In Vivo Nanosensors Using Organic Color Centers

Covalent bonding of organic functional groups to the sp2 carbon lattice of single-walled carbon nanotubes produces tunable sp3 quantum defects that fluoresce brightly in the second near-infrared region (NIR-II, 1000-1700 nm). Such synthetic defects, also known as organic color centers (OCCs), provide a molecular focal point that sensitively and selectively responds to the local dielectric environments. To take advantage of these unique electronic and optical properties of OCCs for biomedical applications, we discuss a new method that controls the biological interactions/biocompatibility of OCC-based nanosensors via their supramolecular interactions with polymers and other excipients. The resulting nanosensor sensitively detects local intracellular environments in live cells and in vivo. We assess the utility of the nanosensor for cancer research.

Synthesis of Zigzag Carbon Nanobelts through Scholl Reactions

AbstractZigzag carbon nanobelts are a long‐sought‐after target for organic synthesis. Herein we report new strategies for designing and synthesizing unprecedented zigzag carbon nanobelts, which present a wave‐like arrangement of hexagons in the unrolled lattice of (n,0) single wall carbon nanotubes (n=16 or 24). The precursors of these zigzag carbon nanobelts are hybrid cyclic arylene oligomers consisting ofmeta‐phenylene and 2,6‐naphthalenylene as well aspara‐phenylene units. The Scholl reactions of these cyclic arylene oligomers form multiple carbon‐carbon bonds selectively at the α‐positions of naphthalene units resulting in the corresponding zigzag carbon nanobelts. As monitored with fluorescence spectroscopy, one of these nanobelts binds C60with an association constant as high as (6.6±1.1)×106 M−1in the solution in toluene. Computational studies combining linear regression analysis and hypothetical homodesmotic reactions reveal that these zigzag nanobelts have strain in the range of 67.5 to 69.6 kcal mol−1, and the ladderization step through Scholl reactions is accompanied by increase of strain as large as 69.6 kcal mol−1. The successful synthesis of these nanobelts demonstrates the powerfulness and efficiency of Scholl reactions in synthesizing strained polycyclic aromatics.

Synthesis of Zigzag Carbon Nanobelts through Scholl Reactions

Zigzag carbon nanobelts are a long-sought-after target for organic synthesis. Herein we report new strategies for designing and synthesizing unprecedented zigzag carbon nanobelts, which present a wave-like arrangement of hexagons in the unrolled lattice of (n,0) single wall carbon nanotubes (n=16 or 24). The precursors of these zigzag carbon nanobelts are hybrid cyclic arylene oligomers consisting of meta-phenylene and 2,6-naphthalenylene as well as para-phenylene units. The Scholl reactions of these cyclic arylene oligomers form multiple carbon-carbon bonds selectively at the α-positions of naphthalene units resulting in the corresponding zigzag carbon nanobelts. As monitored with fluorescence spectroscopy, one of these nanobelts binds C60 with an association constant as high as (6.6±1.1)×106 M-1 in the solution in toluene. Computational studies combining linear regression analysis and hypothetical homodesmotic reactions reveal that these zigzag nanobelts have strain in the range of 67.5 to 69.6 kcal mol-1 , and the ladderization step through Scholl reactions is accompanied by increase of strain as large as 69.6 kcal mol-1 . The successful synthesis of these nanobelts demonstrates the powerfulness and efficiency of Scholl reactions in synthesizing strained polycyclic aromatics.

Preparation, characterization, and viscosity studding the single-walled carbon nanotube nanofluids

Absract This work aims to study experimentally the rheology and viscosity of nanofluids based on ethylene glycol, water, and isopropyl alcohol containing single-walled carbon particles (SWCNT). The weight concentration of SWCNTs varied from 0.05 to 1%, the temperature varied within the range from 10 to 50 °C. Sodium dodecylbenzene sulfonate, polyvinylpyrrolidone, and sodium dodecyl sulfate were used as dispersants. All the studied nanofluids were characterized by non-Newtonian rheology, if only the concentration of SWCNTs was not too low. The nanofluids were either pseudoplastic or viscoplastic fluids. With the increasing concentration of SWCNTs, the fluid index decreased, while the consistency factor increased. Moreover, as the CNT concentration increased, pseudoplastic fluids could become viscoplastic. In the general case, the rheology of nanofluids also changed with increasing temperature. An important fact is that the viscosity of the studied nanofluids depends actually on the effective size of the SWCNTs. The greater their effective size, the greater the viscosity. Indirectly, the answer to the question about the reason for this behavior is given by studying the microrheology of these nanofluids. They demonstrate viscoelastic properties of the nanofluids. This behavior is associated with the formation of a solid spatial lattice of nanotubes in the bulk of nanofluid.

On Ve-Degree and Ev-Degree Based Topological Properties of H-Naphtalenic Nanotube

Scientists are inventing new materials, for example, a carbon nanotube-based composite created by NASA that bends when a voltage is connected. A carbon nanotube-based material belong to a significant and an extensively investigated compounds in chemical science. It has been derived through engineering mechanism at the molecular scale. The most important of these new materials are carbon nanotubes. They have remarkable electronic properties and many other unique characteristics. Carbon nanosheets are 2-dimensional lattices of carbon nanotubes. To compute and study topological indices of nanostructures is a respected problem in nanotechnology. Topological indices are vital devices for investigating chemical compounds to comprehend the fundamental topology of chemical structures. Ev-degree and ve-degree based topological indices are two novel degrees based indices as of late defined in graph theory. Ev-degree and ve-degree based topological indices have been defined as corresponding to their relating partners. In this paper, we have computed topological indices based on ev-degree and ve-degree for the nanosheet T 3[p,q] of H-Naphtalenic nanotube whose cylindrical layer has joinery of C 4, C 6 and C 8 appear alternatively following a trivalent adornment.

Nitrogen in carbon nanotubes

Nitrogen is an important impurity for doping carbon nanotubes (CNTs). It increases the conductivity of nanotubes, which is an important feature for field-effect transistors, emission and other nanoelectronic devices based on CNTs. In this work, we carried out a complex study of the behavior of nitrogen in nanotubes, its effect on their morphology, X-ray photoelectron spectroscopy (XPS) and Raman scattering spectra. The aim of the article is to determine the binding energies of various types of nitrogen distribution in the graphene lattice of carbon nanotubes. The goal was achieved by comparing the XPS spectra, differential gravimetric analysis, and quantum chemical calculations. It was found that a graphite-like state has the highest binding energy, which is energetically favorable during doping and creates donor centers for carbon nanotubes. Therefore, doping with nitrogen increases the conductivity of the nanotubes in most cases.