Surface Of Nanotubes Research Articles

Pd-Ce-Ox species on MWCNTs surface: Probing the structure-activity correlation in low-temperature CO oxidation

Herein, the highly dispersed palladium and ceria species were deposted on the surface of multi-walled carbon nanotubes (MWCNTs) by co-deposition from acetone solutions. The use of MWCNTs allowed varying Pd/Ce atomic ratio in a wide range, while maintaining a high dispersion of the active components. Application of physicochemical methods revealed the formation of various palladium species. Single Pd2+ ions dispersed in CeO2 lattice were the main Pd-Ce-Ox species at low Pdat/Ceat ratio. With an increase of the Pd content in the samples the preferential formation of PdO particles in a tight contact with CeO2 nanoparticles was observed. The size of PdO and CeO2 primary particles was in a range of 1–5 nm.The Pd-Ce-Ox/MWCNTs samples showed high activity in the CO oxidation reaction already at room temperature with a temperature of 50% CO conversion below 100 °C. The Pd2+-CeO2 and PdO-CeO2 species demonstrated the comparable activity in “dry” CO oxidation. However, the presence of water vapor in the reaction mixture resulted in the immediate deactivation of Pd2+-CeO2 species, while PdO-CeO2 species retained a high activity at 20°С. The results of the work highlight the benefits of MWCNTs, Pd, and CeO2 combination for obtaining catalysts highly active in CO oxidation.

Functionalization of titania nanotubes surface with platinum(II) complexes

Functionalization of modern materials is one of the possibilities to make them better tailored for human needs. The paper describes a method of covering the titania nanotubes (TNTs) surfaces formed on Ti6Al4V (grade V) titanium alloy with four platinum(II) bimetallic complexes and cisplatin. The first step of the fabricated TNTs modification was their covering with (3-mercaptopropyl)triethoxysilane (MPTES) which plays a role of a bridge between the TNTs and platinum(II) coordination centres. The final application of platinum(II) dimethylformamide (DMF) solutions allowed to form a homogeneous layers of platinum(II) complexes bonded to the TNTs substrate by thiol sulphur atoms of MPTES without visible crystals of physically deposited complexes. The complexes were characterized with XRD, IR, Raman, 1H and 13C NMR spectroscopies, and thermal and elemental analyses. Characterization of titania substrates was done with IR, Raman, SEM, SEM/EDX, XRD, and XPS.

One Dimensional Twisted Van der Waals Structures Constructed by Self-Assembling Graphene Nanoribbons on Carbon Nanotubes.

Twisted van der Waals heterostructures were recently found to possess unique physical properties, such as superconductivity in magic angle bilayer graphene. Owing to the nonhomogeneous stacking, the energy of twisted van der Waals heterostructures are often higher than their AA or AB stacking counterpart, therefore, fabricating such structures remains a great challenge in experiments. On the other hand, one dimensional (1D) coaxial van der Waals structures has less freedom to undergo phase transition, thus offer opportunity for fabricating the 1D cousin of twisted bilayer graphene. In this work, we show by molecular dynamic simulations that graphene nanoribbons can self-assemble onto the surface of carbon nanotubes driven by van der Waals interactions. By modifying the size of the carbon nanotubes or graphene nanoribbons, the resultant configurations can be controlled. Of particular interest is the formation of twisted double walled carbon nanotubes whose chiral angle difference can be tuned, including the 1.1° magic angle. Upon the longitudinal unzipping of such structures, twisted bilayer graphene nanoribbons can be obtained. As the longitudinal unzipping of carbon nanotubes is a mature technique, we expect the strategy proposed in this study to stimulate experimental efforts and promote the fast growing research in twistronics.

Linking optical and electronic properties to photoresponse of heterojunctions based on titania nanotubes and chromium, molybdenum, and tungsten oxides

The development of photosensitization strategies for titanium dioxide is necessary for the enhancement of its optical and electronic properties towards its application potential in solar photoelectrochemistry. In this work, significant differences in the photosensitizing capability of the 6th group transition metal oxides applied on the surface of titania nanotubes are reported. For the first time, correlations between the experimentally determined Tauc coefficients, sample photoresponse, and ab-initio simulated properties of the heterojunctions are established. Experimental results show undoubtedly that the decoration of TiO2 nanotubes with chromium oxides leads to the enhanced photoresponse, which originates from the interplay of mid-gap states and both direct and indirect nature of the transitions contributing to the optical absorption. The opposite tendency and decrease of photocurrent were found for molybdenum and tungsten oxides which exhibited forbidden nature of dominating transition. Although computations report intraband states in all interfaces, experimentally only chromium oxides contribute to the photocurrent. The uniqueness of this interface lies in the highest density of states in the vicinity of the conduction band and the low energy difference between the direct and indirect transitions of the innate chromium oxide. The obtained results demonstrate that the determination of the Tauc exponent and the nature of optical transition are more reliable experimental predictors of the photoactivity enhancement in the heterojunctions than the value of the band gap.

Spatially Confined Fabrication of Polar Poly(Vinylidene Fluoride) Nanotubes.

Polar poly(vinylidene fluoride) (PVDF) nanotubes have attracted significant attention due to their excellent piezoelectric and ferroelectric properties, yet a tunable fabrication of homogeneous polar PVDF nanotubes remains a challenge. Here, a simple method is reported to fabricate polar PVDF nanotubes using anodize aluminum oxide (AAO) membranes as templates that are removed by etching in a potassium hydroxide (KOH) solution and then ageing at room temperature. PVDF nanotubes originally crystallized in the AAO membrane are pure α-crystals with very low crystallinity, yet after being released from the templates, the crystallinity of the nanotubes markedly increases with ageing at room temperature, leading to the formation of β-PVDF crystals in a very short time, with the formation of γ crystals after longer ageing times. A large amount of γ crystals formed when the released PVDF nanotubes are heated to ≈130°C. The formation of polar PVDF nanotubes released from the AAO templates treated with higher concentrations of alkaline solution results from the reaction of the surface of the PVDF nanotubes with the alkaline solution and structure reorganization under confined conditions. This large-scale preparation of β- and γ-PVDF opens a new pathway to produce polar PVDF nanomaterials.

Fabrication of an intelligent anti-corrosion silane film using a MoO42− loaded Micro/mesoporous ZIF67-MOF/multi-walled-CNT/APTES core-shell nano-container

The design of smart coatings for corrosion protection aims has become one of the most interesting hotspots for contemporary corrosion researchers. For this purpose, scientists mostly grabbed on the utilization of carriers with control-release capability, and carbonaceous materials are the most well-known celebrities among all. In this work, the multi-walled carbon nanotube (CNT) surface was decorated with ZIF67 crystals, and then MoO42− ions (Mo) were loaded into the constructed nano-carrier. Eventually, the synthesized particles' were covered by (3-Aminopropyl) triethoxysilane (APTES) amino silane for better dispersion in the silane matrix. The silanized and un-modified nano-hybrids were precisely explored by different characteristic methods to prove their successful synthesis. Also, the inductively coupled plasma (ICP) measurements demonstrated around 49 ppm, 18 ppm, and 0.02 ppm Co ions in the acidic, neutral, and alkaline conditions, respectively. The Electrochemical Impedance Spectroscopy (EIS) and polarization records in the solution phase revealed that CNT-ZIF67-Mo nano-hybrids successfully declined the corrosion rate of metal up to 91% and 84%, respectively. Thereupon, to design a self-healable anti-corrosion system, CNT-ZIF67-Mo particles at 0.15 wt% were incorporated into the silane-based hybrid coating. The EIS explorations carried out on the scratched composites proved that the total resistance was tripled and self-healing activity with a 69% index was visualized after the inclusion of APTES/CNT-ZIF67-Mo nanoparticles. Also, the EIS investigations over the intact composites declared that the silane coating resistance was increased from 23156 Ω.cm2 to 200169 Ω.cm2 and water uptake was around 73% upon the incorporation of APTES/CNT-ZIF67-Mo nanoparticles.

Theoretical study of the adsorption mechanism of ioversol contrast agent on the single-walled carbon nanotube surface

Ioversol, an organoiodine compound, has high iodine content and several hydrophilic groups. 1-N,3-N-bis(2,3-dihydroxypropyl)-5-[(2-hydroxyacetyl)-(2-hydroxyethyl)amino]-2,4,6-triiodobenzene-1,3-dicarboxamide (ioversol) and its derivatives are used in a wide variety of X-ray procedures, such as computed tomography scans, imaging of the kidneys, arteries and veins. DFT calculations at B3LYP level with LANL2DZ and DGDZVP basis sets were performed to determine electronic, structural and thermodynamic properties of the ioversol contrast agent in gas and water phases. In this study, we investigated the effect of Carbon Nanotube (CNT) and Si-doped CNT on the properties of ioversol, a contrast agent in gas phase and in water phase.

Noncovalent self-assembly of a minuscule amount of nickel porphyrin on carbon nanotube for high-performance electromagnetic wave absorbing

High-performance and lightweight carbon-based electromagnetic wave (EMW) absorbing materials are urgently required for applications in aerospace and next-generation electronics. However, it is of great importance to break through the conventional thinking of loading high-density magnetic metals to improve the EMW absorption performance of carbon-based absorbers. Herein, the 5,10,15,20-tetrakis (4-aminophenyl) porphyrin nickel (Ni-TAPP) was self-assembled on the surface of carbon nanotubes (CNTs) driven by the π-π interactions via a simple, facile, scalable preparation approach. The fabricated Ni-TAPP@CNTs nanocomposites not only effectively integrated the Ni active sites of Ni-TAPP and three-dimensional conductive networks of CNTs, but also exhibited good impedance matching and optimized dielectric loss. Benefiting from this remarkable synergy, the Ni-TAPP@CNTs presented a minimum reflection loss of −66.5 dB (1.9 mm, 10.1 GHz) at a Ni-TAPP content of merely 2.86 wt%. This work undoubtedly provides a high-efficiency strategy for the scalable fabrication of lightweight, durable EMW absorbing materials.

Tissue paper-liked conjugated microporous polymers film for bacteria inhibition

Conjugated microporous polymers (CMPs) film featuring with unique two-dimensional structure and well-developed microporosity inheriting from CMPs shows outstanding function for separation and water purification. However, it is still a great challenge to synthesize truly self-standing CMPs films or membranes with large areas and processible intensity. In this work, inspired by surface-assisted polymerization, taking 1,4-diethynylbenzene and 1,3,5-triethynylbenzene as monomer models, we fabricated three soft tissue paper-liked CMPs films with highly mechanical robustness and flexibility through Pd/Cu-catalyzed homocoupling polymerization combined with a facile template method. All the resulting CMPs films consisted of hollow nanotubes whose physical strength and continuity could be tuned by alkynyl monomers. ACMP1 derived from 1,4-diethynylbenzene showed the maximum elongation and tensile strength with a large area of ∼46 cm2. Moreover, ACMP1 was served as an efficient supporter to prepare ACMP1/silver nanoparticles composite by one-step reduction reaction. The silver nanoparticles were uniformly coated the outer surface of nanotubes and retained the original microporosity of ACMP1, endowing the composite good antibacterial activity against E. coli in water. Our work is expected to provide a platform to develop macroscale CMPs-based film with antibacterial function for water purification and environment remediation.

Oil/water separation and functionality of smart carbon nanotube–titania nanotube composite

Water treatment applications are in high demand recently. In this work, the titania nanotube (TNT) was successfully grown onto the outer surface of the carbon nanotubes (CNTs) via the hydrothermal method. The resultant prepared composite was doped with different ratios of nitrogen. The structural and morphological merits of the composites displayed the successful composition of the matrices, as well as the particle size of the composite within the nanoscale. The optical specifications of the composites demonstrate successful direct and indirect transitions with a high energy gap (> 3 eV). The testing of different oils in the water/oil separation exhibited a high rate of success to split oil and water (> 95%). In this regard, CNT-TNT 1.0 sample reflects the highest efficiency. Compared to other researchers that demonstrate the highest efficiency of their proposed structure, our membrane offers a decent separation efficiency. The proposed composite might provide a feasible and cost-effective method for water/oil separation application in the nanotechnological fields.Graphical abstract

Laminin Adsorption and Adhesion of Neurons and Glial Cells on Carbon Implanted Titania Nanotube Scaffolds for Neural Implant Applications.

Interfacing neurons persistently to conductive matter constitutes one of the key challenges when designing brain-machine interfaces such as neuroelectrodes or retinal implants. Novel materials approaches that prevent occurrence of loss of long-term adhesion, rejection reactions, and glial scarring are highly desirable. Ion doped titania nanotube scaffolds are a promising material to fulfill all these requirements while revealing sufficient electrical conductivity, and are scrutinized in the present study regarding their neuron-material interface. Adsorption of laminin, an essential extracellular matrix protein of the brain, is comprehensively analyzed. The implantation-dependent decline in laminin adsorption is revealed by employing surface characteristics such as nanotube diameter, ζ-potential, and surface free energy. Moreover, the viability of U87-MG glial cells and SH-SY5Y neurons after one and four days are investigated, as well as the material's cytotoxicity. The higher conductivity related to carbon implantation does not affect the viability of neurons, although it impedes glial cell proliferation. This gives rise to novel titania nanotube based implant materials with long-term stability, and could reduce undesirable glial scarring.

A facile approach for grafting ion imprinted polymer onto magnetic multi-walled carbon nanotubes for selective removal and preconcentration of cadmium in food and wastewater samples prior to atomic spectrometric determination

A 3D Fe3O4@MWCNT-CdIIP was synthesized by the oxidizing surface of multi-walled carbon nanotubes with carboxylic acid end groups and its subsequent termination with an ion imprinted polymer. An artificial neural network manifests better predictability than the central composite design methodology for optimising the adsorption procedure. The adsorption capacity was 109 mg g−1 (2.5 times more than non-imprinted polymer) under optimized conditions (pH; 5.6, time; 15 min, concentration; 800 μg mL−1 temperature; 25 °C), which was in accord with Toth isotherm. Fractal-like pseudo-second-order kinetics was found reasonably fast, with 66 % adsorption in 5 min. Solid phase extraction coupled Flame atomic absorption spectrometry method provides selective recognition towards Cd(II), with limit of detection; 1.13 µg/L, limit of quantification; 3.21 µg/L after preconcentration (preconcentration factor; 50) and good robustness. The developed method was applied for Cd(II) determination in food (tea, coffee, bread, tobacco, radish, spinach), water and wastewater (>99 % removal as well). Cd(II) loaded IIP was further utilized to remove anionic dyes with >95 % removal.

Effect of carbon nanotube surface treatment on the dynamic mechanical properties of a hybrid carbon/epoxy composite laminate

The objective of the current investigation is to evaluate the dynamic mechanical properties of a hybrid carbon fiber reinforced epoxy composite laminate containing CNT-rich interlayers, where the CNTs were prepared with ten different surface treatments and two different degrees of alignment. The surface treatments, including surfactants and oxidation, alter the CNT/epoxy stress transfer characteristics. Testing was done in uniaxial tension at different temperatures, loading frequencies and in dry and wet conditions. In the case of imperfectly aligned CNT yarn interlayers, the best surfactant, which was Triton X-100, increased the loss modulus by 182% over the baseline (no CNTs) and increased the storage modulus by 2.2%. Oxidation of the CNTs increased the loss modulus by 219% and the storage modulus by 2.3%, versus the baseline. Highly aligned CNT film provides higher loss modulus (+44%) and storage modulus (+8.4%) than imperfectly aligned CNT yarns, for the case of no surface treatment. Alignment of the CNTs also reduces the sensitivity of dynamic properties to temperature change and moisture content. CNT interlayers reduce the frequency dependency of the dynamic properties. Improvements in damping with surface treatments are hypothesized to be due to improved epoxy impregnation of the condensed CNTs.

Preparation of N, O co-doped carbon nanotubes and activated carbon composites with hierarchical porous structure for CO2 adsorption by coal pyrolysis

Coal pyrolysis was employed to create nitrogen–oxygen co-doped CNTs/AC composites for CO2 adsorption in this work. In comparison to previous publications on carbon nanotube surface modification and direct fabrication of CO2 adsorption materials, the approach developed in this work is simpler, more cost-effective, and has a better CO2 adsorption capability. The synthesized functional composites have high specific surface area (1003–1443 m2/g), high oxygen content (16.1 %) and nitrogen content (2.37 %).Among them, NCNTs/AC-1 exhibited a CO2 adsorption capacity of 3.77 mmol/g and a high CO2/N2 selectivity (25.05) at 298 K and 1 bar. The adsorption behavior of NCNTs/AC-1 can be well described by the Freundlich model. The linear correlation between CO2 absorption capacity, micropore volume of specific size (V < 0.7 nm and V < 0.9 nm), O content and N content was investigated. At 298 K, the contribution of O content to CO2 adsorption is comparable to or even higher than that of N content. Interestingly, micropores in the range of V < 0.9 nm have a good correlation with CO2 adsorption capacity at 273 K. This study offers new perspectives for the high added value and environmental protection of bituminous coal.

Functionalized boron–nitride nanotubes: First-principles calculations

With the use of density functional theory (DFT) calculations, we study the effect of functionalizing the surface of a boron nitride nanotube (BNNT) with hydroxyl (-OH) and carboxyl (-COOH) organic groups at the N and B sites. The results indicate that the -OH radical remains adsorbed in the B site whereas it is detached from the surface when added to the N site. Contrarily, the -COOH group remains attached for both adsorption sites. Both functionalizations induced a magnetic moment, produced spin-polarized electronic bands, created flat impurity-like bands, decreased the band gaps, and modified the electron density of the nanotubes. All of these changes can be used to control and modify the interaction of BNNTs with other molecules of interest like drugs, heavy metals, and greenhouse gasses, among other substances.

Construction of Mo-MOF-derived molybdenum dioxide on carbon nanotubes with tunable nitrogen content and particle size for oxidative desulfurization

The combination of distinctive properties of carbon nanotubes and metal oxides is expected to exploit novel catalysts offering high catalytic ability. Herein, a nano-sized MoO2 derived from molybdenum-based metal-organic framework was anchored on the surface of carbon nanotubes (CNT) with urea as a regulator. Powder X-ray diffraction analysis suggested that the nitrogen content and the MoO2 particle size of the as-prepared catalyst could be tuned by changing the urea dosage and the calcination temperature. Elemental mapping indicated the homogeneous dispersion of the nano-sized MoO2 on the surface of CNT for MoO2@CNT-U7.5 (U7.5 represents mass ratio of urea to CNT). Compared with MoO2@CNT treated in absence of urea, MoO2@CNT-U7.5 showed extremely higher catalytic performance in oxidative desulfurization of fuel. With H2O2 as an oxidant, the removal of refractory sulfur compounds including dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene can reach >99% within 40 min at the reaction temperature of 50 °C. In addition, the catalyst exhibited superior cycling stability and could be recycled for eight times with little loss of sulfur removal. The reaction mechanism was eventually proposed with the assistance of GC–MS and ESR analysis.

Efficient photocatalytic remediation of typical antibiotics in water via Mn3O4 decorated carbon nitride nanotube

Antibiotic abuse will seriously affect the ecology and environment. Photocatalytic oxidation technology based on carbon nitride (g-C3N4) has been widely adopted to treat wastewater containing antibiotics. Here, a novel composite photocatalyst MCNT was prepared by loading manganese oxide (Mn3O4) on the surface of g-C3N4 nanotubes (CNT). Three typical antibiotics, trimethoprim (TMP), norfloxacin (NOR), and tetracycline (TC) were used as model contaminants to evaluate the oxidative properties of prepared materials. Compared with bulk g-C3N4, the degradation rates of TMP, NOR, and TC catalyzed by MCNT-5 were increased by 2, 3, and 1.4 times, respectively, mainly due to 1) the larger specific surface area of the nanotube structure of CNT, which provides abundant active sites for antibiotic adsorption and catalytic oxidation, and 2) the loading of Mn3O4, which promotes the directional migration of photogenerated charges and improves the separation efficiency of photogenerated electrons and holes. The free radical capture and quenching experiments confirmed that MCNT degraded the target organic pollutants with hydroxyl radical (·OH) and singlet oxygen (1O2) as the main active oxidants. This catalyst maintained 80% photocatalytic oxidation performance after five cyclic experiments. This study provides new insights into developing efficient, stable, and environmentally-friendly photocatalysts and provides a new dimension to mitigate the antibiotic pollution problem.

In Situ Activation of Superhydrophobic Surfaces with Triple Icephobicity at Low Temperatures.

Superhydrophobic surfaces have been widely studied due to their potential applications in aerospace fields. However, superhydrophobic surfaces with excellent water-repellent, anti-icing, and icephobic performances at low temperatures have rarely been reported. Herein, superhydrophobic surfaces with heating capability were prepared by etching square micropillar arrays on the surface of multiwalled carbon nanotube (MWCNT)/poly(dimethylsiloxane) (PDMS) films. The fabricated superhydrophobic surface has triple icephobicity, which can be activated even at low temperatures. The triple icephobicity is triggered by an applied voltage to achieve excellent water-repellent and icephobic capabilities, even at -40 °C. Additionally, theoretical calculations reveal that a droplet on a superhydrophobic surface loses heat at a rate of 8.91 × 10-5 J/s, which is 2 orders of magnitude slower than a flat surface (2.15 × 10-3 J/s). Also, at -40 °C, the mechanical interlocking force formed between the superhydrophobic surface and ice can be released by the heating property of the superhydrophobic surface. This low-energy, multifunctional superhydrophobic surface opens up new possibilities for bionic smart multifunctional materials in icephobic applications.

Plasma Functionalization of Multi-Walled Carbon Nanotubes for Ammonia Gas Sensors.

The role of plasma functionalization of multi-walled carbon nanotubes (MWCNTs) for room-temperature ammonia gas sensors was investigated. Plasma functionalization of MWCNTs with maleic anhydride was carried out at various durations. The active material of the gas sensor was investigated by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. It was shown that the formation of functional groups on the surface of carbon nanotubes led to an increase in the ammonia sensor response by two to four times. The increase in functionalization duration induced the rise of O/C from 0.28 to 0.335, an increase in sensor resistance, and the distortion of the shape of the I-V curves.

Effect of Extremely Short-Sized MWCNT as Additive Material in High Surface Area Activated Carbon and Its Enhanced Electrical LIC Performance.

Extremely short-sized multi-wall carbon nanotube (CNT) and high surface area activated carbon were used to increase the electrical performance of lithium-ion capacitors (LIC). After electrodes were synthesized using extremely short-sized CNTs and high specific surface area activated carbon, their electrochemical characteristics were evaluated by XRD, SEM, TEM, cyclic voltammetry, EIS, BET, adoption isotherm, t-plot, and pore size distribution. In the process of electrode preparation using extremely short-sized CNTs and high specific surface area activated carbon, CNTs certainly caused a space-filling effect between these two materials, which had a significant effect on the evaluation of electrical characteristics. These relationships were demonstrated by the results of adsorption–desorption isotherm, pore size distribution, t-plot, and BJH plot. Particularly, in the electrochemical cyclic test, as the content of CNT increased, the current density significantly increased with the formation of a near-perfect rectangular shape. This tendency also exhibited excellent characteristics in a t-I plot, Tafel plot, and LSV plot, which clearly affected the electrochemical oxidation–reduction reaction due to the densification of filling density and space structure by adding extremely short-sized CNTs to the active material. In addition, YP80_CNT3 formed a specific resistance value in the range of 7.2 to 6.2 Ω/cm2, showing significantly reduced values compared to other samples. This research presented herein offers a promising route for the rational design of MWCNT and stable electrochemical reaction with LIC working mechanism.