Open-ended Nanotubes Research Articles

Facile fabrication of aligned doubly open-ended TiO2 nanotubes, via a selective etching process, for use in front-illuminated dye sensitized solar cells

A simple selective etching process easily removed a 2nd anodized TiO(2) nanotubes (TNTs) layer from a physically stable 1st anodized TNTs layer to produce noncurling, freestanding, large-area aligned doubly open-ended TNTs. These TNTs were easily transferred to a conducting glass for use in fabricating front-illuminated dye sensitized solar cells.

A novel 1D independent metal–organic nanotube based on cyclotriveratrylene ligand

A novel nanotubular metal–organic framework [Cu3L2(EtOH)(Py)2(H2O)2]·9DEF·8H2O (CTV-Cu) was prepared by assembly of the rigid, trigonal pyramidal ligand tri-(4-carboxy-phenyl)-trimethoxycyclobenzylene (H33L) and Cu(NO3)2·3H2O viasolvothermal reaction. The Cu(II) ions in the crystal serve as square and linear molecular building blocks, thus forming a framework with ternary topology. One single open-ended nanotube contains two identical orthogonally interpenetrated two-nodal nets. This framework exhibits permanent microporosity and relatively high surface area.

Methane storage in homogeneous armchair open-ended single-walled boron nitride nanotube triangular arrays: a grand canonical Monte Carlo simulation study

The physisorption of methane in homogeneous armchair open-ended SWBNNT triangular arrays was evaluated using grand canonical ensemble Monte Carlo simulation for tubes 11.08, 13.85, 16.62, and 19.41 Å [(8,8), (10,10), (12,12), and (14,14), respectively] in diameter, at temperatures of 273, 298, 323, and 373 K, and at fugacities of 0.5-9.0 Mpa. The intermolecular forces were modeled using the Lennard-Jones potential model. The absolute, excess, and delivery adsorption isotherms of methane were calculated for the various boron nitride nanotube arrays. The specific surface areas and the isosteric heats of adsorption, Q(st), were also studied, different isotherm models were fitted to the simulated adsorption data, and the model parameters were correlated. According to the results, it is possible to reach 108% and 140% of the US Department of Energy's target for CH(4) storage (180 v/v at 298 K and 35 bar) using the SWBNNT array with nanotubes 16.62 and 19.41 Å in diameter, respectively, as adsorbent. The results show that for a van der Waals gap of 3.4 Å, there is no interstitial adsorption except for arrays containing nanotubes with diameters of >15.8 Å. Multilayer adsorption starts to occur in arrays containing nanotubes with diameters of >16.62 Å, and the minimum pressure required for multilayer adsorption is 1.0 MPa. A brief comparison of the methane adsorption capacities of single-walled carbon and boron nitride nanotube arrays was also performed.

Covalent coupling of polyacrylic acid coated magnetic-nanoparticles to multi-wall carbon nanotubes for manipulation targets

This research effort investigated the chemical heterojunction between magnetic nanoparticles coated with polyacrylic acid and multi-wall carbon nanotubes (MWCNTs). Here, magnetic nanoparticles were covalently attached to open-ended nanotubes in the presence of diclohexylcarbodiiimide. Initial evidence demonstrated that short functionalised multi-wall nanotubes can be continuously connected at their terminals ends to build-up relatively large nanostructures. It has also been shown that magnetic-carbon nanotubes (CNTs) systems exhibited defined arrangements due to the influence of magnetic fields. Indeed, linear arrays of CNTs interconnected through magnetic nanoparticles were prone to be manipulated in the presence of a magnetic device. A potential application of these kind of magnetic nanostructures was shown here by successfully manipulating agarose beads in a buffer solution. These results suggest that the use of continuously connected magnetic nanostructures with non-modified sidewall surfaces will find potential applications in the area of bio-sensing, force transduction and cancer screening-manipulation among many others.

Room temperature synthesis of indium tin oxide nanotubes with high precision wall thickness by electroless deposition

Conductive nanotubes consisting of indium tin oxide (ITO) were fabricated by electroless deposition using ion track etched polycarbonate templates. To produce nanotubes (NTs) with thin walls and small surface roughness, the tubes were generated by a multi-step procedure under aqueous conditions. The approach reported below yields open end nanotubes with well defined outer diameter and wall thickness. In the past, zinc oxide films were mostly preferred and were synthesized using electroless deposition based on aqueous solutions. All these methods previously developed, are not adaptable in the case of ITO nanotubes, even with modifications. In the present work, therefore, we investigated the necessary conditions for the growth of ITO-NTs to achieve a wall thickness of around 10 nm. In addition, the effects of pH and reductive concentrations for the formation of ITO-NTs are also discussed.

Cerium (IV) oxide nanotubes prepared by low temperature deposition at normalpressure

This paper reports the synthesis of cerium dioxide nanotubes (CeNTs) by electrolessdeposition using ion-track-etched polycarbonate templates. To achieve nanotubes with thinwalls and small surface roughness the tubes were generated by a several-step-containingprocedure under aqueous conditions. The approach reported below will process open endnanotubes with well-defined outer diameter and wall thickness.

Fabrication of nickel hydroxide electrodes with open-ended hexagonal nanotube arrays for high capacitance supercapacitors

A nickel hydroxide electrode with open-ended hexagonal nanotube arrays, prepared by hydrolysis of nickel chloride in the presence of hexagonal ZnO nanorods, shows a very high capacitance of 1328 F g(-1) at a discharge current density of 1 A g(-1) due to the significantly improved ion transport.

Fabrication of Zinc Oxide Nanotubes by Chemical Bath Deposition Using Ion Track-Etched Templates

Nanotubes consisting of zinc oxide were fabricated by electroless deposition, using ion track-etched polycarbonate templates. To achieve nanotubes with thin walls and small surface roughness, the tubes were generated by a several steps containing procedure under aqueous conditions. The reported approach that is described shortly will process open-end nanotubes with well-defined outer diameter and wall thickness.

Fabrication of open-ended TiO2 nanotube arrays by anodizing a thermally evaporated Ti/Au bilayer film

Fabrication of TiO2 nanotube arrays (TNAs) with through-hole morphology is practical significance to enhance the photocatalytic activity of TNAs, as well as expanding their applications. In present work, open-ended TNAs are synthesized on a conductive Au layer by anodizing a thermally evaporated Ti/Au bilayer film. In the anodizing process, the upper Ti layer is transformed into well-aligned TNAs. The barrier layer under the growing TNAs ultimately touches the Au layer and is completely dissolved by the electrochemical etching. In order to avoid the bubble disruption of TNAs caused by the water electrolysis after the Au layer is exposed to the electrolyte, a specific non-aqueous electrolyte is used. The XRD results reveal that the as-formed open-ended TNAs are amorphous and can be transformed into anatase by annealing at 350°C.

The Influence of the Rigidity of a Carbon Nanotube on the Structure and Dynamics of Confined Methanol

In this paper, we compare the behavior of liquid methanol confined by an open-ended single-walled nanotube (SWCNT) under four different simulation conditions by using the molecular dynamics (MD) simulations technique. The first model is a rigid and fixed SWCNT with all its carbon atoms fixed at their initial positions; the second is a flexible and fixed SWCNT with its centre-of-mass fixed at the center of the MD box and with the carbon–carbon bond potential applied; the third is a rigid and floating SWCNT, and the fourth is the most realistic flexible and floating SWCNT model — without fixed atoms and with bond potential. The microscopic structure and transport properties of bulk methanol confined by the four different SWCNTs were analyzed. No changes in the radial distribution functions of the hydrogen bond between MeOH molecules are found, and the self-diffusion constant and microscopic dipole relaxation time are essentially unaffected by the confinements. In spite of the flexible/rigid or fixed/floating ð15; 15Þ SWCNT model used, the structure and transport properties of confined MeOH are found to be very close in all the simulated cases. We conclude that using the approximation of rigid or/and fixed SWCNT does not lead to any systematic errors in properties of the confined liquid. The results show that simulations using rigid carbon nanotubes provide a reliable description of molecular diffusion and other solvent properties in a variety of applications, such electro-chemical devices, membranes and sensors that rely on these properties.

Modifying Surface Structure to Tune Surface Properties of Vertically Aligned Carbon Nanotube Films

We report a simple etching process to modify surface of vertically aligned carbon nanotube (VACNT) arrays for their applications in superhydrophobic surface, field emission display, and sun energy conversion, etc. At a high temperature (700-800 degrees C), very low concentration water vapor in presence with Ar and hydrogen flow can be a weak oxidant, and mildly etch nanotube tips without damaging their walls. This process can be performed right after the CNT growth process. Surface of nanotube arrays becomes multi-tiered nanotube patterns with open-ended nanotubes standing straightly. Surface morphology of nanotube arrays can be tuned by changing the etching time. Water droplets on a modified nanotube surface show a large contact angle and sliding angle, which make the etched nanotube film suitable for application such as small amount liquid transport. Light absorption measurement indicated that surface roughness has no effect to improve the light absorption, indicating a different mechanism from other black material. The surface modified nanotube arrays have much increased field enhancement factor in our field emission test, showing the better field emission ability of the nanotube arrays with open tips.

Fabrication of anatase titanium dioxide nanotubes by electroless deposition using polycarbonate for separate casting method

Abstract Titanium dioxide nanotubes (TNTs) were prepared by electroless deposition using ion track etched polycarbonate templates. The ion tracks were prepared to the desired diameter of the TNTs outer diameter. Titanium dioxide nanotubes with a diameter of minimum 80 nm having a wall thickness of minimum 10 nm can be fabricated using this method. To achieve nanotubes with thin walls and small surface roughness the tubes were generated by a several steps procedure under aqueous conditions at nearly room temperature. The presented approach will process open end nanotubes with well defined outer diameter and wall thickness. Using this method TNT arrays up to 109 tubes per cm2 having a tube length up to 30 μm can be produced, single tubes are also possible. The structural properties of the grown TNTs were investigated by using various analytical techniques, i.e. scanning electron microscopy (SEM), energy dispersive X-ray fluoresence spectrometer (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and Photoluminescence.

One-step realization of open-ended TiO2 nanotube arrays by transition of the anodizing voltage

Free-standing TiO2 nanotubes with both their ends open are required in many applications. This article reports the authors’ latest progress in meeting these requirements. Elevating the voltage at the end of an anodization process can break the adhesion of the TiO2 nanotube layer to the underlying Ti substrate and simultaneously open their bottoms. Furthermore, by modulating the value and duration of the elevated voltage, the bottom morphology of the nanotubes can also be effectively tailored. Compared with most of the related work, in which obtaining free-standing TiO2 nanotube layers and opening their bottom ends are often performed in two separate procedures, this newly-developed route features a simple one-step solution and also good controllability. Both the detachment of the nanotubes from the Ti substrate and the tailoring of their bottom ends are ascribable to the local acidification and gas evolution induced by the sudden voltage transition.

Synthesis and electrochemical performance of lithium vanadium oxide nanotubes as cathodes for rechargeable lithium-ion batteries

Abstract A new kind of cathode materials for rechargeable lithium-ion batteries, lithium vanadium oxide nanotubes synthesized by a combined sol–gel reaction and hydrothermal treatment procedure is reported in this paper. SEM, TEM, XRD and XPS techniques were performed to investigate the morphology and structure of the resulting materials. The results confirmed that the synthetic materials are composed of uniformly open-ended multiwalled nanotubes with a length from 1 to 3 μm. The inner and the outer diameters of the obtained nanotubes vary from 30 to 50 nm and 50 to 120 nm, respectively. The electrochemical performance as a cathode material was examined and evaluated by cyclic voltammetry, galvanostatic charge–discharge cycling and AC impedance spectroscopy techniques. The results indicated that the resultant lithium vanadium oxide nanotubes have a high initial discharge capacity of 457 mAh g−1 in the potential range of 1.0–4.0 V (vs. Li/Li+) and good cycling performance. The improved electrochemical performance of the products should be due to its special one-dimensional multiwalled tubular structure and the contribution of lithium-ions.

Theoretical study of the transition metal ring functionalized tips of open-ended (5,5) boron nitride nanotube (BNNT)

The nanotube with open edges is an excellent candidate for designing efficient tip for atomistic scanning probes or field emission display (FED) devices. In the present work, we have studied the functionalization of an open-ended boron nitride nanotube (BNNT) with a series of transition metal rings and the effects on the properties of open-ended BNNT through density functional theory (DFT) calculations. The results show that the TM-BNNT complexes are energetically favorable. Moreover, it is found that the functionalization (a) significantly decreases the band gap of BNNT to different degrees, which might effectively modify the electronic properties of the open-ended BNNT; and (b) efficiently lowers the work function, which might improve the field emission properties. Our results might be helpful not only to design specific BNNT-based tips but also to further discuss the chemical vapor deposition (CVD) growth of BNNT on nanoparticles.

Theoretical Studies of the Interaction of an Open-Ended Boron Nitride Nanotube (BNNT) with Gas Molecules

We have systematically studied the effects of several gaseous adsorbates (H2, N2, O2, and H2O) on the electronic properties of open edges of boron nitride nanotubes (BNNTs) by using density functional theory calculations. The results indicate that all of the molecules, except N2, dissociate and chemisorb on open BNNT edges with large adsorption energies because the tube edge has either an open or capped structure and thus has dangling bonds or pentagonal defects. The high reactivity of an open-ended BNNT even can be comparable with that of its carbon counterpart, although the wall of the BNNT is chemically more stable than a single-walled carbon nanotube’s wall. Moreover, we note that adsorption of gases at the tips of open BNNTs can modify their electronic properties in various ways. A considerable amount of charge transferred for the adsorption of gases on the open BNNTs may account for the changes of the electronic properties. Interestingly, the open (5,5) BNNT exhibits the properties of wide-band-gap materials when gases are adsorbed at top sites, while a smaller band gap is observed when these gases are adsorbed on seat sites. Additionally, the magnetic moments of gas-adsorbed N atoms in the open N-rich-ended (8,0) are significantly decreased because the dangling bonds are “saturated”. The present results might be helpful in the design of BNNT-based nanomaterials such as field emitters or nanojunctions.

Impregnating ionic Pt species on vanadium oxide nanotubes

Vanadium oxide nanotubes (VNT) have drawn increasing attention as vanadium compounds may be used in a wide range of applications. In this contribution, VNT was synthesized by a hydrothermal treatment from V 2O 5 using hexadecylamine as template. XRD, FTIR, SEM, TEM/HRTEM and TG analyses were used to investigate their chemical stability and suitability to adsorb platinum ionic species without damaging the nanostructure. It was shown that the nanostructures are open-ended multiwalled nanotubes, formed by 13–16 layered walls, with inner diameter of 30–50 nm and outer diameter of 150–200 nm. The impregnation of Pt was found to be feasible but their structure and morphology are sensitive to the pH of the impregnation media.

Hierarchical Supramolecular Self‐Assembly of Nanotubes and Layered Sheets

Roll up! Roll up! The self-assembly of para-terphenylen-1,4′′-ylenebis(dodecanamide) in THF results in either multiwalled, rolled-up, open-ended organic nanotubes or layered sheets (see picture) depending on the conditions used. The nanotubes can co-assemble with fullerene to produce quasi-cable-like structures with C60 nanowires inside the nanotubes.

Impact of mesoporous pore distribution on adsorption of methylene blue onto titania nanotubes in aqueous solution

This study investigates the liquid-phase adsorption behavior of methylene blue (MB) dye onto titania nanotubes, prepared by hydrothermal method, at different temperatures ranging from 30 °C to 50 °C. The nanotubes are mainly mesoporous, and their pore sizes were found to increase with calcination temperature. The maximum of MB adsorption capacity was found to be ca. 290 mg/g at 30 °C. The isosteric heat ( q st) of adsorption was obtained from the adsorption isotherm measurements. The heat of adsorption at low coverage is in the range ∼10.1–13.5 kJ/mol, while at the monolayer completion, the value of q st displays a minima within 4.6–6.2 kJ/mol. The magnitude of q st confirms that the adsorption mechanism is physisorption. The variation of isosteric heat with surface coverage reflects that the titania nanotubes have a surface heterogeneity for adsorption of MB in liquid phase. The heat of adsorption of MB on the nanotubes is the decreasing function of the tubular size of the nanotubes. The difference of q st value can be attributed to two concepts: (i) in narrow pores, the concave pore walls would provide overlapping potentials at low coverage; (ii) at high coverage, capillary process easily takes place in the smaller pore. This result supports the usefulness of open-ended titania nanotubes for dye adsorption in liquid phase.

Hosoya polynomial of zigzag polyhex nanotorus

The Hosoya polynomial of a molecular graph G is defined as H(G,?)=?{u,v}V?(G) ?d(u,v), where d(u,v) is the distance between vertices u and v. The first derivative of H(G,?) at ?=1 is equal to the Wiener index of G, defined as W(G)?{u,v}?V(G)d(u,v). The second derivative of 1/2 ?H(G, ?) at ?=1 is equal to the hyper-Wiener index, defined as WW(G)+1/2?{u,v}?V(G)d(u,v)?. Xu et al.1 computed the Hosoya polynomial of zigzag open-ended nanotubes. Also Xu and Zhang2 computed the Hosoya polynomial of armchair open-ended nanotubes. In this paper, a new method was implemented to find the Hosoya polynomial of G = HC6[p,q], the zigzag polyhex nanotori and to calculate the Wiener and hyper Wiener indices of G using H(G,?).