Multi-walled Tubes Research Articles

High Strength Multifunctional Multiwalled Hydrogel Tubes: Ion-Triggered Shape Memory, Antibacterial, and Anti-inflammatory Efficacies.

In this study, ion-responsive hydrogen bonding strengthened hydrogels (termed as PVV) were synthesized by one-pot copolymerization of 2-vinyl-4,6-diamino-1,3,5-triazine (VDT), 1-vinylimidazole (VI), and polyethylene glycol diacrylate. The diaminotriazine-diaminotriazine (DAT-DAT) H-bonding interaction and copolymerization of VI contributed to a notable increase in comprehensive performances including tensile/compressive strength, elasticity, modulus, and fracture energy. In addition, introducing mM levels of zinc ions could further increase the mechanical properties of PVV hydrogels and fix a variety of temporary shapes due to the strong coordination of zinc with imidazole. The release of zinc ions from the hydrogel contributed to an antibacterial effect, without compromising the shape memory effect. Remarkably, a multiwalled hydrogel tube (MWHT) fixed with Zn(2+) demonstrated much higher flexural strengths and a more sustainable release of zinc ions than the solid hydrogel cylinder (SHC). A Zn(2+)-fixed MWHT was implanted subcutaneously in rats, and it was found that the Zn(2+)-fixed MWHT exhibited anti-inflammatory and wound healing efficacies. The reported high strength hydrogel with integrated functions holds potential as a tissue engineering scaffold.

Deformation, energy absorption and crushing behavior of single-, double- and multi-wall foam filled square and circular tubes

Deformation and energy absorption studies with single, double and multi-wall square and circular tube structure with and without aluminum foam core are carried out for assessing its effectiveness in crashworthiness under the identical test conditions. Modeling and numerical simulation of aluminum foam filled square tubes under axial impact loading is presented. The foam-filled thin-walled square tubes are modeled as shell wherein, foam core is modeled by incorporating visco-elastic plastic foam model in Altair® RADIOSSTM. It is observed that the multi-wall tube structure with foam core alters the deformation modes considerably and results in substantial increase in energy absorption capacity in comparison with the single and multi-wall tube without foam core. Moreover, the multi-wall tube foam filled structure shows mixed deformation modes due to the significant effect of stress wave propagation. This study will help automotive industry to design superior crashworthy components with multi-tube foam filled structures and will reduce the experimental trials by conducting the numerical simulations.

Enhancement in Electrical Conductance of Pt Decorated Multiwalled Carbon Tubes Using Electron Beam-Induced Deposition Technique

We propose a direct-write approach to decorate the hanging multiwalled carbon tubes (MWCNTs), at the selected sites with platinum (Pt) metal, using electron beam-induced deposition (EBID) technique. As prepared nanostructure is investigated by scanning electron microscopy (SEM), confirming the deposition of Pt nanoclusters on tube surface. The conductance of the individual tube enhances significantly due to Pt deposition at desired locations on the tubes. The value of conductance (in terms of quanta) of the same tube is increased from 3.2 G0 to 11.7 G0 at zero bias after Pt deposition. This enhancement in conductance is explained in terms of change in density of states (DOS) at the Fermi level which results in charge transfer between tubes and nanoclusters. This approach can be used for the applications of tubes in nano-devices which is dependent on the distribution of metal nanostructures, nano gas sensors, and in the interconnections.

<i>In Situ</i> Synthesis of Copper Phthalocyanine Modified Multiwalled Carbon Tube and its Electrocatalytic Application towards the Oxidation of Nitrite

We have synthesized metal phthalocyanine modified multiwalled carbon nanotube by a solid-phase synthesis method by heating a reaction mixture of phthalic anhydride, ammonium molybdate and MWCNT in a required molar ratio using muffle furnace. The metal phthalocyanine modified MWCNT samples collected and then washed extensively with various solvents to removal all impurities and unreacted starting materials. The resulting nanocomposite was characterized by IR, UV-Visible spectroscopy, Scanning Electron Microscopy, X-ray diffraction and Raman spectroscopy. The nanostructure of the CuPc/MWCNT assembly exhibits a homogeneous nanocomposite. The electrocatalytic study of the CuPc/MWCNT assembly towards the oxidation of nitrite was investigated. An enhanced oxidation peak current was noted with lowering oxidation over potential ranges. The proposed method can be applied for the amperometry detection of nitrite present in food samples.

High oxygen reduction activity of few-walled carbon nanotubes with low nitrogen content

Nitrogen-containing few-walled carbon nanotubes (N-FWCNTs) with very low nitrogen content (0.56at.%) were obtained by a process involving the coating of acid functionalized FWCNTs with polyaniline (PANI) followed by pyrolysis at high temperatures. The resulting N-FWCNTs exhibited a remarkable electrocatalytic activity for the oxygen reduction reaction (ORR), despite significantly lower nitrogen content than previously reported in literature. The N-FWCNTs performed on par or better than Pt-C in the cathode of an alkaline direct methanol fuel cell, corroborating the ORR activity observed in the electrochemical cell and exhibiting a higher methanol tolerance. Interestingly, N-FWCNTs showed a high activity for the hydrogen evolution reaction and for the hydrogen peroxide decomposition, suggesting that the active sites involved in ORR can simultaneously catalyze other reactions. This unprecedentedly high activity for such a low N-content can be explained by the exceptional accessibility for the catalytic sites located in open and porous N-doped layer surrounding the FWCNT core, along with the minimization of inactive inner volume and mass compared to larger nitrogen doped multiwalled tubes.

Fast synthesis of multilayer carbon nanotubes from camphor oil as an energy storage material.

Among the wide range of renewable energy sources, the ever-increasing demand for electricity storage represents an emerging challenge. Utilizing carbon nanotubes (CNTs) for energy storage is closely being scrutinized due to the promising performance on top of their extraordinary features. In this work, well-aligned multilayer carbon nanotubes were successfully synthesized on a porous silicon (PSi) substrate in a fast process using renewable natural essential oil via chemical vapor deposition (CVD). Considering the influx of vaporized multilayer vertical carbon nanotubes (MVCNTs) to the PSi, the diameter distribution increased as the flow rate decreased in the reactor. Raman spectroscopy results indicated that the crystalline quality of the carbon nanotubes structure exhibits no major variation despite changes in the flow rate. Fourier transform infrared (FT-IR) spectra confirmed the hexagonal structure of the carbon nanotubes because of the presence of a peak corresponding to the carbon double bond. Field emission scanning electron microscopy (FESEM) images showed multilayer nanotubes, each with different diameters with long and straight multiwall tubes. Moreover, the temperature programmed desorption (TPD) method has been used to analyze the hydrogen storage properties of MVCNTs, which indicates that hydrogen adsorption sites exist on the synthesized multilayer CNTs.

Abstract B063: Tumor targeting and diagnostic applications of glycosylated nanotubes

Abstract The goal of this research is to develop a new agent based on multiwalled carbon nanotubes (MWCNT) for the diagnosis and monitoring of advanced breast cancer. MWCNT consist of sheets of graphene carbon rolled into multiwalled tubes and possess many properties that make them extremely useful in biomedical applications, including targeted molecular imaging. Foremost is their ability to deliver large numbers of imaging agents per each targeted molecular recognition event, which can improve the sensitivity of imaging; secondly, they can deliver several different types of imaging agents (such as magnetic resonance imaging or photoacoustic agents) to perform multimodality imaging; thirdly, they can be used for therapeutic applications including chemotherapeutic drug or gene delivery, and as mediators for photothermal cancer therapy. As early and accurate diagnosis is still the most effective approach to treating cancer, improvements in the use of imaging technology to detect and monitor cancer will have a dramatic effect on human health. Breast cancer cells have alterations in the normal metabolism of the sugar, glucose, and exhibit increased glucose uptake and decreased glucose clearance. The hypothesis to be tested is that MWCNTs targeted to glucose transporters will be taken up by cancer cells with high efficiency, and that such MWCNT can be engineered to be effective cancer diagnostic agents. To this end, we have chemically engineered MWCNTs to display deoxyglucose on their surface, which rendered them water soluble, and targets them to cancer cells. It is anticipated that this agent will serve as the basis for a multimodal platform for future combined cancer therapy and diagnostic applications. We now report on our initial findings with this agent, and describe: 1) a new, glycosylated MWCNT which can be traced by radiolabelling; 2) data on clinically-relevant issues relating to blood compatibility, and preclinical data on toxicity (clot formation), biodistribution, blood, urinary, and fecal clearance of intravenously injected glycosylated MWCNT, all of which will be essential for any future translational applications; 3) a new nanomedical platform technology, developed specifically to target and diagnose invasive breast cancer, but with broad applicability to many types of cancer. Citation Format: Ravi N. Singh. Tumor targeting and diagnostic applications of glycosylated nanotubes. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr B063.

Exciton Description of Chlorosome to Baseplate Excitation Energy Transfer in Filamentous Anoxygenic Phototrophs and Green Sulfur Bacteria

A description of intra-chlorosome and from chlorosome to baseplate excitation energy transfer in green sulfur bacteria and in filamentous anoxygenic phototrophs is presented. Various shapes and sizes, single and multiwalled tubes, cylindrical spirals and lamellae of the antenna elements mimicking pigment organization in chlorosomes were generated by using molecular mechanics calculations, and the absorption, LD, and CD spectra of these were predicted by using exciton theory. Calculated absorption and LD spectra were similar for all modeled antenna structures; on the contrary, CD spectra turned out to be sensitive to the size and pigment orientations in the antenna. It was observed that, bringing two tubular antennae at close enough interaction distance, the exciton density of the lowest energy state became localized on pigments facing each other in the antenna dimer. Calculations predicted for stacked tubular antenna elements extremely fast, faster than 500 fs, intra-chlorosome energy transfer toward the baseplates in the direction perpendicular to the chlorosome long axis. Downhill excitation energy transfer according to our model is driven by interactions of the antennae with their immediate surroundings. Energy transfer from the chlorosome to the baseplate, consisting of 2D lattices of monomeric and dimeric bacteriochlorophyll a molecules, was predicted to occur in 5-15 ps, in agreement with experimental findings. Advancement of excitation through a double tube antenna stack, a model for antenna element organization in chlorosomes of green sulfur bacteria, to a monomeric baseplate was visualized in space and in time.

Geomimetic catalysis: From volcanic stones to ultra-selective Fe–Mo/Al2O3–TiO2 catalysts for few-walled carbon nanotube production

Volcanic stones from the Greek island of Santorini have been used as natural catalysts for the growth of multiwalled carbon nanotubes by chemical vapor deposition. In a unique geomimetic experiment, we show that a synthetic catalyst mimicking the natural rock can lead to highly selective production of thin multiwalled tubes.

Preconcentration of benzene and phenolic compounds in water sample by adsorption on Carbon nanotubes coated fiber

A simple method has been developed for the preconcentration of benzene and phenolic compounds (BPC) by the adsorption of its carbon nanotubes (CNTs). The preconcentration of benzene and phenolic compounds (BPC) are ubiquitous pollutants, and many of them are carcinogenic or mutagenic. Carbon nanotubes (CNTs) are a kind of novel and interesting carbon material which can be used for separation and purification. In this investigation, commercial solid-phase microextraction (SPME) fibers (PDMS) were coated with single-wall nano tubes (SWNTs) and multi-wall nano tubes (MWNTs) to study the adsorption and extraction ability of hydrophobic BPC. While MWNTs adsorbed more hydrophobic BPC than SWNTs, the fibers coated with CNTs had advantages over traditional SPME fibers in selectivity and sensitivity. They could be used to separate hydrophobic BPC. The results show that the selectivity, sensitivity and reproducibility of this method are good for real sample analysis. Key words: Carbon nanotubes (CNTs), Solid-phase microextraction (SPME), preconcentration of benzene and phenolic compounds (BPC).

Palladium–nickel nanoparticles loaded on multi-walled carbon nanotubes modified with β-cyclodextrin for electrooxidation of alcohols

β-Cyclodextrin (β-CD) was grafted to the surface of multi-walled carbon tubes (MWCNTs) immobilized on Ti plates to obtain the β-CD-MWCNT/Ti electrode by using the self-assembly method. Binary Pd–Ni nanoparticles were then electrodeposited on the β-CD-MWCNT/Ti to synthesize the PdNi/β-CD-MWCN/Ti electrode. As a comparison, PdNi/MWCNT/Ti and PdNi/Ti electrodes were also prepared under the same condition. SEM images show that compared to the PdNi/MWCNT/Ti and PdNi/Ti, the binary PdNi nanoparticles on the β-CD-MWCNT/Ti are more highly dispersed with smaller sizes of 90–130nm. Electrocatalytic activity of the as-synthesized electrodes towards electrooxidation of ethanol, propanol and butanol in alkaline media was investigated. Results show that the PdNi/β-CD-MWCNT/Ti electrode exhibits very high electroactivity for the alcohol oxidations and presents much enhanced performance compared with other two electrodes. Among the three alcohols, ethanol displays the greatest activity with the highest oxidation current density while butanol shows the lowest oxidation current density.

Morphology of hydrothermally synthesized ZnO nanoparticles tethered to carbon nanotubes affects electrocatalytic activity for H2O2 detection

We describe the synthesis of zinc oxide (ZnO) nanoparticles and demonstrate their attachment to multiwalled carbon tubes, resulting in a composite with a unique synergistic effect. Morphology and size of ZnO nanostructures were controlled using hydrothermal synthesis, varying the hydrothermal treatment temperature, prior to attachment to carboxylic acid functionalized multi-walled carbon nanotubes for sensing applications. A strong dependence of electrocatalytic activity on nanosized ZnO shape was shown. High activity for H2O2 reduction was achieved when nanocomposite precursors with a roughly semi-spherical morphology (no needle-like particles present) formed at 90°C. A 2.4-fold increase in cyclic voltammetry current accompanied by decrease in overpotential from the composites made from the nanosized, needle-like-free ZnO shapes was observed as compared to those composites produced from needle-like shaped ZnO. Electrocatalytic activity varied with pH, maximizing at pH 7.4. A stable, linear response for H2O2 concentrations was observed in the 1–20mM concentration range.

Electrospinning of multilevel structured functional micro-/nanofibers and their applications

Electrospinning is a straightforward and versatile way to fabricate multilevel structured ultrafine fibers down to the micro-/nanometer scale. In this review, recent achievements in electrospun fibers with multilevel surfaces and inner structures are presented. The multilevel surface structures include branched structures, porous structures, necklace structures and non-cylinder deformed structures. The multilevel inner structures are classified as peapod structures, multiwalled tube structures, wire-in-tube structures and multichannel structures. Furthermore, the outstanding properties of multilevel structured fibrous materials are discussed and highlighted. These electrospun multilevel structured materials have wide applications in sensing, filtration and adsorption, catalysis, energy storage, bio-field, and many other fields.

Photoresponse from noble metal nanoparticles-multi walled carbon nanotube composites

In this Letter, we investigated the photo-response of multi wall carbon nanotube-based composites obtained from in situ thermal evaporation of noble metals (Au, Ag, and Cu) on the nanotube films. The metal deposition process produced discrete nanoparticles on the nanotube outer walls. The nanoparticle-carbon nanotube films were characterized by photo-electrochemical measurements in a standard three electrode cell. The photocurrent from the decorated carbon nanotubes remarkably increased with respect to that of bare multiwall tubes. With the aid of first-principle calculations, these results are discussed in terms of metal nanoparticle–nanotube interactions and electronic charge transfer at the interface.

Effects of a transverse electric field on the electronic properties of single- and multi-wall BN nanotubes

In this work, we apply first-principles calculations, based on the density functional theory, to investigate the effect of a transverse electric field on the properties of single, double and triple-walled boron nitride nanotubes. The obtained results indicate that significant reduction on the formation and gap energies are observed for single-wall tubes with diameter greater than 10Å. Such modifications arise from the Stark effect which is related to the polarization of the atomic orbitals. Nevertheless, for multi-walled tubes, a more selective mechanism takes place. Only the (5,0)@(13,0) double walled tube show significant gap narrowing. For the other structures it is speculated that the polarization associated to the internal tube compensate the polarization associated to the external one, neutralizing the effects of the applied electric field.

An experimental investigation on heat transfer characteristics of multi-walled CNT-heat transfer oil nanofluid flow inside flattened tubes under uniform wall temperature condition

An experimental investigation on heat transfer characteristics of MWCNT-heat transfer oil nanofluid flow inside horizontal flattened tubes has been carried out under uniform wall temperature condition. Nanoparticle weight fractions were 0%, 0.1%, 0.2%, and 0.4%. The copper tubes of 14.5mm I.D. were flattened and used as the test section of oblong shape with inside heights of 13.4mm, 11.7mm, 10.6mm, and 8.6mm. The nanofluid flowing inside the tube was heated inside a steam chamber to keep the temperature of the tube wall constant. The required data were acquired for laminar hydrodynamically fully developed regime. The effects of different parameters such as volumetric flow rate, nanoparticle weight fraction, and hydraulic diameter on the heat transfer behavior of the tested systems have been investigated experimentally. For a given flattened tube at a constant nanoparticle weight fraction, increasing volumetric flow rate results in heat transfer enhancement. In addition, as the tube profile becomes more flattened and the hydraulic diameter decreases, the heat transfer coefficient goes up at constant volumetric flow rate. Utilizing nanofluids instead of the base fluid, the heat transfer rate enhances remarkably. The higher the nanoparticles weight fraction, the more the rate of heat transfer enhancement. Finally, the results show that the amount of increase in heat transfer coefficient caused by employing nanofluid instead of the base fluid is comparable to what caused by flattening the tube.

First-principles studies on stabilities and electronic properties of AlN nanostructures

Under the generalized gradient approximation (GGA), the stabilities and electronic properties of semiconductor AlN nanostructures have been investigated by using the first-principles projector-augmented wave (PAW) potential within the density function theory (DFT) framework. The single-walled faceted AlNNTs present an obvious structural modification. The larger the diameter, the more stable the nanowire, and the wires without internal surfaces are more stable than the multiwalled tubes or the SWNT. Therefore, the large-size nanowires are easier to be synthesized than the corresponding multiwalled tubes or single-walled nanotube in experiment. The dangling bonds of surface atoms cause the “localized edge-induced states”. These two nanostructures C and F are still wide band gap semiconductors accompanied by a few surface states located in the band gap of bulk AlN and thus extremely suitable for application in flexible pulse wave sensors, nanomechanical resonators and light-emitting diodes.

Preparation and properties of multiwalled carbon nanotube/epoxy‐amine composites

AbstractDifferent amounts of multiwalled carbon tubes (MWCNTs) were incorporated into an epoxy resin based on diglycidyl ether of bisphenol A and both epoxy precursor and composite were cured with 4,4′‐diamino diphenyl sulfone. Transmission and scanning electron microscopy demonstrated that the carbon nanotubes are dispersed well in the epoxy matrix. Differential scanning calorimetry measurements confirmed the decrease in overall cure by the addition of MWCNTs. A decrease in volume shrinkage of the epoxy matrix caused by the addition of MWCNTs was observed by pressure–volume–temperature measurements. Thermomechanical and dynamic mechanical analysis were performed for the MWCNT/epoxy composites, showing that the Tg was slightly affected, whereas the dimensional stability and stiffness are improved by the addition of MWCNTs. Electrical conductivity measurements of the composite samples showed that an insulator to conductor transition takes place between 0.019 and 0.037 wt % MWCNTs. The addition of MWCNTs induces an increase in both impact strength (18%) and fracture toughness (38%) of the epoxy matrix with very low filler content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

A molecular dynamics simulation study for the mechanical properties of different types of carbon nanotubes

Carbon nanotubes have caught tremendous attention of the researchers during the last decade due to their excellent mechanical, electrical, optical and thermal prop- erties. The exploitation of these fibers as reinforcing agents in making strong fiber composites has been a primary research topic in the recent investigations on composite materials. Although the theoretical results are rather opti- mistic, the goal of achieving high strength of the carbon nanotube composites is still not satisfactorily realized. We report here a comparative study of the mechanical properties of single-walled, multi-walled and bundle of single-walled carbon nanotubes. Their mechanical behavior is investigated by molecular dynamics simulation, considering Brenner's second generation reactive empirical bond order interatomic potential between the carbon atoms making a tube. For a long range interaction, we have defined a weak van der Waals force which acts between different layers of a multi-walled tube or between different tubes of a bundle. Samples of three isolated armchair single-wall carbon nanotubes of different diameters, a multi-wall armchair carbon nanotube and finally a bundle of three armchair single-walled nanotubes of same diameter are taken. Their fracture pattern and buckling behavior are modeled and compared. Significant changes are observed in the mechanical properties of the samples of different types of carbon nanotubes which arise due to the interaction between the shells of a multi-walled tube or the tubes in a bundle.

A Family of Carbon-Based Nanocomposite Tubular Structures Created by in Situ Electron Beam Irradiation

We report a unique approach for the fabrication of a family of curling tubular nanostructures rapidly created by a rolling up of carbon membranes under in situ TEM electron beam irradiation. Multiwall tubes can also be created if irradiation by electron beam is performed long enough. This general approach can be extended to curve the conductive carbon film loaded with various functional nanomaterials, such as nanocrystals, nanorods, nanowires, and nanosheets, providing a unique strategy to make composite tubular structures and composite materials by a combination of desired optical, electronic, and magnetic properties, which could find potential applications, including fluid transportation, encapsulation, and capillarity on the nanometer scale.