As-synthesized Nanotubes Research Articles

Li1.4Al0.4Ge0.1Ti1.5(PO4)3: A stable solid electrolyte for Li-CO2 batteries

In this study, a solid electrolyte, Li1.4Al0.4Ge0.1Ti1.5(PO4)3 (LAGTP), with a sodium superionic conductor-type crystal structure, was prepared using a facile solution-based method. LAGTP exhibited exceptional ionic conductivity (1.05 × 10−3 S cm−1) and a low activation energy (0.237 eV). The LAGTP pellet was employed as a solid-state electrolyte in a Li-CO2 battery, showcasing charge-discharge characteristics via a reversible electrochemical reaction (4Li+ + 3CO2 ↔ 2Li2CO3 + C). As-synthesized multi-walled carbon nanotubes, drop-cast on carbon cloth, were used as the cathode. The battery underwent 60 cycles with a cut-off capacity of 1000 mAh g−1 at various current densities, and a full-depth charge and discharge test was conducted at 100 mA g−1. During the charge/discharge process, the particle size of the dead lithium increased on the cathode surface, leading to the blockage of active sites for conversion. Post-cycling analyses were performed to elucidate the cathode degradation mechanism. The incorporation of LAGTP significantly enhanced battery cycle life and safety, making it a suitable candidate for use in next-generation, high-performance Li-CO2 batteries.

Towards the synthesis of semiconducting single-walled carbon nanotubes by floating-catalyst chemical vapor deposition: Challenges of reproducibility

High-purity semiconducting single-walled carbon nanotubes (s-SWCNTs) are of paramount significance for the fabrication of high-performance electronics. Here, we present continuous production of high-purity, long, and isolated s-SWCNTs by gas-phase synthesis, retaining the pristine morphologies of as-synthesized nanotubes. The s-SWCNTs were synthesized at ca. 920 °C using ethanol and methanol as carbon source and growth enhancer, respectively in N2 and H2. The purity of as-produced s-SWCNTs with a mean length of 15.2 μm can reach 98% as determined by optical absorption spectroscopy. We observed that the overpressure in the reactor and methanol are the principal causes of the enrichment of s-SWCNTs. Specifically, the s-SWCNTs were found to be more negatively charged, and oxygen-contained species play critical roles in the s-SWCNT synthesis. Through the demonstration of field-effect transistors, the s-SWCNTs exhibit a high mean charge carrier mobility of 453.3 cm2 V−1 s−1 which is 2.27 times higher than that of the transistors fabricated with high-quality dispersion-processed SWCNTs. Additionally, we discuss the challenges of synthesis repeatability and recommend a few tips to improve reproducibility. Our study represents an important step towards the scalable production of clean, long, and isolated s-SWCNTs with high purity and narrow bandgap distribution.

Highly efficient as-synthesized and oxidized multi-walled carbon nanotubes for copper(II) and zinc(II) ion adsorption in a batch and fixed-bed process

In this work, the optimization of temperature, argon gas flow rate, acetylene gas flow rate and time effect on the yield of as-synthesized multi-wall carbon nanotubes (AS-MWCNTs) using a novel iron-nickel/biochar catalyst was investigated. Subsequently, the AS-MWCNTs were functionalized to obtain oxidized multi-wall carbon nanotubes (OX-MWCNTs). The nanoadsorbents were applied for Cu(II) and Zn(II) ions adsorption from wastewater in a batch and fixed-bed process. Remarkably, the results revealed optimum AS-MWCNTs yield (280%) at the following experimental conditions; temperature (725 °C), argon gas flow rate (250 mL/min), acetylene gas flow rate (180 mL/min) and time (75 min). OX-MWCNTs demonstrated higher surface area of 1210 m 2/g compared to AS-MWCNTs (1140 m 2/g). The optimum removal of Cu(II) and Zn(II) ions were obtained at pH (6), contact time (30 min), adsorbent dosage (20 mg/L), initial metal concentration (Cu(II) (75 mg/L) and Zn(II) (80 mg/L)) and temperature (45 oC). Maximum adsorption capacities for Cu(II) and Zn(II) ions removal by AS-MWCNTs were obtained as 364.66 and 347.01 mg/g, while OX-MWCNTs produced higher maximum adsorption capacities of 416.47 and 411.88 mg/g. The experimental data were better fitted by Langmuir isotherm and pseudo-second order kinetics, while thermodynamic investigation revealed a favorable and spontaneous chemisorption controlled adsorption of metal ions. Furthermore, the breakthrough curves of Cu(II) and Zn(II) ions was suitably modelled by Thomas kinetic model. Accordingly, AS-MWCNTs and OX-MWCNTs indicate a promising choice to eliminate Cu(II) and Zn(II) ions in wastewater due to its stability, high efficiency, environmental friendliness and excellent recyclability capacity.

Synthesis of highly porous g-C3N4 nanotubes for efficient photocatalytic degradation of sulfamethoxazole

Pyrolysis of supramolecular assembly precursor is a promising method to prepare graphite carbon nitride (g-C3N4), and the topological structure of the precursor assemblies largely determine the morphology and photoelectric properties of g-C3N4. In this paper, uniformly and highly porous g-C3N4 nanotubes were synthesized under the assistance of 1,5-naphthalene disulfonic acid (NA) through the melamine (MA)-cyanuric acid (CA) precursor self-assembly strategy. The as-synthesized g-C3N4 nanotubes in the presence of 75 mg/L NA (MNCA-75) exhibited the highest BET surface area (SBET) of 100.40 m2/g, and the smallest band gap (Eg) of 2.31 eV. 10 mg/L of sulfamethoxazole (SMX) was completely degraded within 120 min with the MNCA-75, and the degradation reaction conformed to pseudo-first-order kinetics. This paper reported a facile but effective method to prepare highly porous g-C3N4 nanotubes with large surface area and excellent photocatalytic performance.

Morphological Evolvement of Carbon Nanotubes Synthesized by Using Conducting Polymer Nanofibers

Carbon nanotubes were synthesized by using a nanostructured conducting polymer—the polypyrrole nanofiber via microwave radiation. The radiation time was set to be 30, 60, and 90 seconds, respectively. The morphological evolvements of the as-synthesized carbon nanotubes with increased radiation time (e.g., shape, diameter, wall structure, and catalyst size) were carefully investigated, and the possible growth mode was discussed in detail. It was found that the growth mode of the carbon nanotubes synthesized from the conducting polymer substrate under microwave radiation was complex and cannot be simply interpreted by either a “tip” or “base” growth model. A new growth mode of the “liquifying cascade growth” was observed for the as-synthesized carbon nanotubes, as their growth was directed by a series of liquified iron nanoparticles with sequentially decreasing sizes, similar to the cascade of liquid droplets. And it could provide useful insights for the morphological and structural designs of the carbon nanotubes prepared by related microwave-based methods.

Hierarchical Tubular-Structured MoSe2 Nanosheets/N-Doped Carbon Nanocomposite with Enhanced Sodium Storage Properties.

Intimately coupled carbon/molybdenum-based hierarchical nanostructures are promising anodes for high-performance sodium-ion batteries owing to the combined effects of the two components and their robust structural stability. Mo-polydopamine (PDA) complexes are appealing precursors for the preparation of various Mo-based nanostructures containing N-doped carbon (NC). A facile method for the fabrication of hierarchical tubular nanocomposites with intimately coupled MoSe2 and NC nanosheets has been developed, which involves the preparation of Mo-PDA hybrid nanotubes through a chemical route followed by two heat treatments. The strong coupling between Mo anions and the catechol groups in dopamine not only restricts the crystallite size but also inhibits agglomeration during selenization, resulting in few-layered MoSe2 nanosheets embedded in hierarchical NC substrates. The as-synthesized nanotube composites are constructed by assembling primary MoSe2 /NC nanosheets. This unique structure not only increases the number of active sites but also shortens the diffusion length of ions and enhances the electronic conductivity of electrode materials. The as-synthesized hierarchical MoSe2 /NC nanotubes deliver a high capacity of 429 mAh g-1 at 1 A g-1 after the 150th cycle when used as anodes in sodium-ion batteries. Furthermore, at a high current density of 10 A g-1 , a high discharge capacity of 236 mAh g-1 is achieved.

Influence of electrolytic parameters in the formation of TiO2 nanotubes over Ti6Al4V

Metallic biomaterials are widely used in the orthopaedic research field for bone fixation, prosthetic device as well as in dental applications. Titanium-based alloys are considered a suitable candidate for implant-based applications because of its specific material property. Among various materials explored, Ti6Al4V is a promising material which has been widely used for implant applications. Surface property of these alloys plays a major role in most of the applications. In this regard, modification of the surface by nanodesigning has been utilized to improve the surface properties of the titanium and its alloys for biomedical application. However, certain parameters are needed to control the surface morphology of the alloy. Thus, in order to get titania (TiO2) nanotubes arrays over the Ti6Al4V alloy different electrolytes has been used. In the present study, Ethylene glycol (EG) and Ethylene glycol and Distilled water (EGDW) with ammonium fluoride salt were used as electrolytes. Voltage was kept constant in both the electrolytes. Moreover, diameter of the formed nanotubes was found to be changed when anodization was done in two different electrolytes. Inner and outer diameter of the as-synthesized nanotubes when anodization carried out in ethylene glycol was found to be 43.3571 nm and 93.6288 nm respectively. Whereas inner and outer diameter of as developed nanotubes when anodizing was carried out in Ethylene glycol and Distilled water (EGDW) was found to be 33.8484 nm and 89.9901 nm respectively. Moreover, as-synthesized anodized samples were heat-treated at 450 °C for 3 h. The prepared samples were characterized by scanning electron microscopy and XRD to study the phase change and the tube diameter in the developed nanostructure.

Production of carbon nanotube yarns via floating catalyst chemical vapor deposition: Effect of synthesis temperature on electrical conductivity

Effect of synthesis temperature on the structure, morphology and crystallinity of as-synthesized CNT yarns via direct spinning was studied using Raman spectroscopy, x-ray powder diffraction (XRD) and thermogravimetric analysis (TGA). Effects of synthesis temperature on purity, morphology and thermal stability were related to the conductivity of the CNT yarns. It was observed that increase in synthesis temperature increased the sp2 content of the as-synthesized carbon nanotubes yarns as indicated by the decrease in ID/IG ratio and increase in oxidation temperature. Current-Voltage (I-V) relationship for the CNT yarns synthesized at 1000 °C indicates an increase in resistivity with increased applied voltage, indicating promising potential of the produced yarns as filaments for incandescent bulbs.

Characterization of micelle-templated silica nanotubes and nanotube bundles using tilt-series transmission electron microscopy

Pluronic-surfactant-templated silica and organosilica nanotubes, silica nanotube bundles and silicas with small ordered domains of cylindrical mesopores were characterized by using tilt-series transmission electron microscopy (TEM). In as-synthesized nanotube samples, three-dimensional (3-D) arrangements of long nanotubes, likely involving local cross-linking of nanotube pairs, were uncovered. As-synthesized silica nanotubes tended to be unstable during TEM observation, which appeared to stem from stretching and breaking of nanotubes whose parts belonged to two different nanotube aggregates, the latter undergoing shrinkage under TEM conditions. However, silica nanotubes hydrothermally treated at a sufficiently high temperature and methylene-bridged organosilica nanotubes did not undergo this kind of changes to any appreciable extent. Despite the observed instability of as-synthesized nanotubes, the calcined sample exhibited narrow pore size distribution, suggesting that if a similar degradation occurs during drying and calcination, it may merely fragment the nanotubes. Nanotube bundles were observed to exhibit 3-D structures with often curved bundle segments locally meeting one another and potentially forming loops. A junction within a seemingly continuous nanotube bundle was observed, where ends of two groups of nanotubes met. This feature is likely to have its counterparts in particles of materials with much larger ordered domain sizes. The imaging of a large-pore silica with 2-D hexagonal domains of small size revealed the presence of an impurity consisting of spheres encircled by nanotubes. These results demonstrate that the tilt-series TEM imaging is a powerful method for characterization of not only complicated 3-D morphologies of surfactant-templated materials, but also their softness and possible degradation modes.

Large-scale self-template synthesis of NiCo2O4 nanotubes derived from alginate for high-rate lithium storage properties stimulated by capacitive effects

Searching high-rate and long-life electrode material of transition metal oxides is still considered a prospective choice to boost powerful electrochemical energy conversion and storage application. Herein, NiCo2O4 nanotubes have been fabricated in large quantities by a facile self-template formation strategy using alginate. Such an interesting nanostructure owns optimal voids inside the stable shells, which can facilitate the fast ion diffusion and efficiently buffer the huge volume changes when used as an anode material for lithium ion batteries. As a result, the as-synthesized NiCo2O4 nanotubes electrode delivers admirable electrochemical properties with high reversible capacity (1162 mAh g−1 in the initial cycle at 0.2 A g−1), excellent cycling stability (949 mAh g−1 after 800 cycles at 1 A g−1) and especially remarkable rate capability (684 mAh g−1 even at 8 A g−1). The present work may demonstrate great potential in the large-scale preparation of the NiCo2O4 nanotubes for advanced lithium storage.

Solvothermal synthesis of porous SnS2 nanotubes with higher adsorption and photocatalytic activity

This letter reports for the first time on the photocatalysis of SnS2 nanotubes, with the goal of maximizing the potential of SnS2 for photocatalytic applications. SnS2 nanotubes were synthesized by a solvothermal method with the assistance of cobalt-nitrilotriacetic acid complex nanorods as the sacrificial template. The X-ray diffraction, Raman and X-ray photoelectron spectroscopy analyses indicated the formation of pure hexagonal phase SnS2. Scanning electron microscope and transmission electron microscope images revealed that the as-synthesized SnS2 comprised porous nanotubes, which were assembled from intertwined, 5 nm-thick nanosheets. Nitrogen adsorption-desorption isotherms disclosed that the as-synthesized SnS2 nanotubes had a much big specific surface area (232.8 m2/g). Photocatalytic experiments showed that the as-synthesized SnS2 nanotubes not only far surpassed SnS2 nanoflowers, nanoflakes and nanoparticles in the adsorption and visible-light-driven photocatalytic reduction of aqueous Cr(VI), but also had good recyclability. This study tells that the photocatalytic activity of SnS2 can be enhanced by the preparation of porous nanotubular microstructre.

Multifunctional self-healing polymeric nanocomposite coatings for corrosion inhibition of steel

The present work focuses on the self-healing and corrosion behavior of novel epoxy based coatings containing epoxy monomer (EM) and dodecylamine (DDA) as self-healing and corrosion inhibitor, respectively. The coating self-healing ability and the corrosion inhibition effect have been combined, together, in one single coated layer providing autonomous corrosion protection. Towards this goal, the as-synthesized titania nanotubes (TNTs), with an average size of 20 nm were impregnated with DDA and EM and were thoroughly dispersed into the epoxy used as the matrix and applied on steel. Fourier-transform infrared spectroscopy (FTIR) analysis confirms the presence of DDA loaded nanotubes and the loading of inhibitor was estimated by thermogravimetric analysis. Additionally, the amount of the released corrosion inhibitor was identified by gas chromatography–mass spectrometry (GC–MS). The scanning electron microscopy (SEM), analysis shows the polymer healing of the prepared coatings when damaged. The electrochemical studies indicate that the corrosion rate of the steel samples coated with the epoxy modified with the healing additives decreases after 5 days of immersion in saline water.

(Keynote) Facile Sorting of Single Walled Carbon Nanotubes According to Their Electronic Types

Single walled carbon nanotubes have interesting electronic properties such as superior semiconducting properties. However, before they can be applied in real electronic transistors, the as-synthesized carbon nanotubes need to be puriifed of the contaminating metallic carbon nanotubes which short circuit the the semi-conducting ones. We had developed various techniques to purify and sort SWNTs according to their electronic types including the use of polymers, and also the application of redox reactions which can directly probe the band gap of metallic nanotubes facilely. This talk shall describe the latest scaleable technique that we have developed that to achieve ultra-high pure semiconducting SWNTs.

Synthesis of FeP nanotube arrays as negative electrode for solid-state asymmetric supercapacitor

Recently, metal phosphides have attracted considerable attention as promising electrode materials for supercapacitors. In this work, FeP nanotube arrays have been successfully synthesized on carbon cloth using ZnO nanorod arrays as the sacrificial templets, via a phosphidation process. The dimensions of the FeP nanotubes are characterized using SEM and TEM showing the diameter to be approximately 200 nm and with a wall thickness of 50–100 nm. The tubular structure of FeP nanotubes provides a facile ion pathway and reduced inner inactive material, thus they are favorable for supercapacitor applications. As a result, the as-synthesized FeP nanotube arrays deliver an improved specific capacitance of 149.11 F g−1 and a high areal capacitance of 300.1 mF cm−2 at a current density of 1 mA cm−2. Furthermore, an MnO2//FeP solid-state asymmetric supercapacitor was fabricated with a high areal capacitance of 142 mF cm−2, which indicates the great potential of FeP nanotube arrays to be a high-performing negative electrode material for supercapacitors.

Hierarchical B-doped carbon nanotube with enhanced electrochemical lithium storage

Rechargeable lithium ion batteries have spurred intense research to resolve the ever-increasing energy and environmental issues due to their efficient high energy density. Herein we demonstrate a simple pyrolysis route to fabricate novel hierarchical B-doped tubular carbon nanostructures. The unique tubular nanostructures along with B-doped effect could represent a high activity for surface-dependent electrochemical reaction processes. Experimental results reveal that the as-synthesized B-doped carbon nanotube show excellent electrochemical performances for lithium storage application. The B-doped carbon nanotube could deliver a high initial discharge capacity (2862.8 mAh g−1) with Coulombic efficiency of 43.91% at 100 mA g−1 current density. Even at a higher current density of 500 mA g−1, the B-doped carbon nanotube could exhibit an enhanced initial discharge capacity of 1800.9 mAh g−1, and the reversible lithium storage capacity still retains at 851.3 mAh g−1 over 100 cycles, suggesting a good cycling stability. The excellent electrochemical properties of the as-synthesized B-doped carbon nanotube could be ascribed to the unique tubular architecture, which could offer large active surface with more lithium-insertion channels and significantly reduce lithium ion diffusion distance. The cost-efficient synthesis and excellent lithium storage properties make the B-doped carbon nanotube as a promising anode material for high-performance lithium ion batteries.

In Ukrainian

The catalytic system “carbon nanotubes/peroxide molecule” in aqueous/non-aqueous media was investigated for determining of the main factors that influence on catalyst’s effectiveness. The catalytic activity of as-synthesized multi-walled carbon nanotubes, and their modified forms (oxidized and nitrogen doped) were investigated in the decomposition of hydrogen, benzoyl (BP) and lauroyl (LP) peroxides at room temperature by measuring the volume of released gases. Ethyl acetate and tetrachloromethane were used for BP and LP decomposition respectively. Among factors that determined the catalytic performance of investigated samples their structural-sorption properties, surface chemistry and diffusion limitation have been considered. It was established that CNT show moderate activity in aqueous medium because of internal diffusion limitation. As a consequence, their performance is determined by the textural characteristic of carbon matrices. Based on the calculated diffusion coefficients it was concluded that catalysis by CNT in non-aqueous area is carried out in the kinetic region on their accessible surface. Such catalytically active surface has a lot of N-containing functional groups as well as basic O-containing ones, therefore it shows better activity towards organic peroxides. Moreover, CNT’s surface is more hydrophobic that is promoting the reaction proceeding in non-aqueous media. The decomposition rate of steric BP is lower compared to the long chain of LP. Based on this finding, it could be predicted that mesoporous CNT with high content basic functionalities and good surface accessibility should be the excellent catalyst for diacyl peroxides decomposition in organic solvents.

Facile active control of a pulsed erbium-doped fiber laser using modulation depth tunable carbon nanotubes

Short pulsed fiber lasers have been widely made using single-walled carbon nanotubes as a saturable absorber (SA). However, most of the currently used devices can only operate in one determined operation state with an unchangeable modulation SA depth in the cavity, which significantly limits their application in photonic devices. In this paper, well-aligned carbon nanotube arrays are synthesized using zeolite AlPO4-5 as a template, which features anisotropic optical absorption. The linear optical absorption of the as-synthesized carbon nanotube arrays can easily be tuned by adjusting a polarization controller, thus providing a tunable modulation depth for the carbon nanotube SA. By exploiting this SA in an erbium-doped fiber laser cavity, both Q-switched and mode-locked pulsed lasers are achieved by simply adjusting a polarization controller under a fixed pump power of 330 mW. In addition, the repetition rate of the Q-switching and pulse duration of the mode-locking can be tuned according to the variation of modulation depth. Moreover, soliton molecules can be obtained when the modulation depth of the SA is 4.5%.

Synthesis of boron nitride nanotubes by combining citrate-nitrate combustion reaction and catalytic chemical vapor deposition

High-quality boron nitride nanotubes were successfully synthesized via a novel two-step method, including citrate-nitrate combustion reaction and catalytic chemical vapor deposition. The composition, bonding features and microstructures of as-synthesized sample were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, Raman microscopy, X-ray photoelectron spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, transmission electron microscopy and selected area electron diffraction techniques. The results show that the as-synthesized boron nitride nanotubes with smooth surface are relatively pure. The diameter ranges between 20 and 80 nm, while the length is about dozens of micrometers. During the synthesis process of boron nitride nanotubes, citric acid chelates the cobalt ions and reacts with nitrate to form the cobalt oxide, depositing on the surface of boron powder homogeneously. The catalyst content and annealing temperature have a significant impact on the composition and microstructures of the final products. Based on the experimental results and thermodynamic analysis, the possible chemical reactions are listed, and vapor-liquid-solid mechanism is proposed to be dominant for the formation of boron nitride nanotubes.

A novel approach for synthesis of MoS2 nanotubes assisted with HNTs

One-dimensional MoS2 nanotubes were synthesized by using halloysite nanotubes (HNTs) as template and the thermolytical approach. The structure and morphology of MoS2 nanotubes were determined by a series of characterizations. The as-synthesized MoS2 nanotubes presented a hollow nanotubular structure with the pore diameter of 2.52 nm and the specific surface area of 89.34 m2/g. The formation mechanism of MoS2 nanotubes was proposed.

Hydrothermally synthesized highly dispersed Na2Ti3O7 nanotubes and their photocatalytic degradation and H2 evolution activity under UV and simulated solar light irradiation

Photocatalytic water splitting technologies are currently being considered for alternative energy sources. However, the strong demand for a high H2 production rate will present conflicting requirements of excellent photoactivity and low-cost photocatalysts. The first alternative may be abundant nanostructured titanate-related materials as a photocatalyst. Here, we report highly dispersed Na2Ti3O7 nanotubes synthesized via a facile hydrothermal route for photocatalytic degradation of Rhodamine B (RhB) and the water splitting under UV-visible light irradiation. Compared with commercial TiO2, the nanostructured Na2Ti3O7 demonstrated excellent photodegradation and water splitting performance, thus addressing the need for low-cost photocatalysts. The as-synthesized Na2Ti3O7 nanotubes exhibited desirable photodegradation, and rate of H2 production was 1,755 μmol·g−1·h−1 and 1,130 μmol·g−1·h−1 under UV and simulated solar light irradiation, respectively; the resulting as-synthesized Na2Ti3O7 nanotubes are active in UV light than that of visible light response.