Tube-like Nanostructures Research Articles

Metal-Organic Framework on Fullerene (MOFOF) as a Hierarchical Composite by the Integration of Coordination Chemistry and Supramolecular Chemistry.

There is a synergy between coordination chemistry and supramolecular chemistry that has led to the development of innovative hierarchical composites with diverse functionalities. Here, we present a novel approach for the synthesis and characterization of a metal-organic framework on fullerene (MOFOF) composites, achieved through the integration of coordination chemistry and supramolecular chemistry principles. The hierarchical nature of the MOFOF harnesses the inherent properties of metal-organic frameworks and fullerenes. The two-step synthesis procedure involves controlled assembly of fullerenes as tube-like nanostructures (fullerene nanotube: FNT), their surface functionalization, and the on-surface growth of the MOF (in this case, ZIF-67). The method permits the precise tuning of morphology, effective distribution of MOF-on-FNT, and tight compositional control. The materials were comprehensively structurally characterized using electron microscopy, spectroscopic techniques, and other methods to elucidate the unique features and interactions within the MOFOF composites. The main findings reveal that the novel synthesis and characterization of MOFOF composites demonstrate the successful integration of coordination chemistry and supramolecular chemistry for the designing and fabricating of advanced hierarchical composites with tailored properties, including micro- and mesopore channels, interfacial facets, and defect sites. These properties are expected to lead to numerous potential applications such as gas storage and separation, catalysis, sensing, energy storage, and environmental remediation. However, only the capability of acid vapor sensing was tested and is described here.

Dynamic Response of an Elastic Tube-like Nanostructure Embedded in a Vibrating Medium and under the Action of Moving Nano-Objects

In recent years, researchers have looked at how tube-like nanostructures respond to moving loads and masses. However, no one has explored the scenario of a nanostructure embedded in a vibrating medium used for moving nano-objects. In this study, the governing equations of the problem are methodically derived using the nonlocal elasticity of Eringen as well as the Rayleigh and Reddy–Bickford beam theories. Analytical and numerical solutions are developed for capturing the nonlocal dynamic deflection of the nanostructure based on the moving nanoforce approach (excluding the inertia effect) and the moving nanomass approach (including the inertia effect), respectively. The results predicted by the established models are successfully verified with those of other researchers in some special cases. The results reveal that for low velocities of the moving nano-object in the absence of the medium excitation, the midspan deflection of the simply supported nanotube exhibits an almost symmetric time-history curve; however, by increasing the nano-object velocity or the medium excitation amplitude, such symmetry is violated, mainly due to the lateral inertia of the moving nano-object, as displayed by the corresponding three-dimensional plots. The study addresses the effects of the mass and velocity of the moving nano-object, amplitude, and frequency of the medium excitation, and the lateral and rotational stiffness of the nearby medium in contact with the nanostructure on the maximum dynamic deflection. The achieved results underscore the significance of considering both the inertial effect of the moving nano-object and the shear effect of stocky nanotubes embedded in vibrating media. This research can serve as a strong basis for conducting further investigations into the vibrational properties of more intricate tube-shaped nanosystems that are embedded in a vibrating medium, with the aim of delivering nano-objects.

Impact of annealing on charge storage capability of thermally evaporated molybdenum oxide thin films

Rapid technological advancements in recent years have necessitated the creation of energy-related devices. Due to their unique properties, including an exceptional cycling life, safe operation, low processing cost, and a higher power density than batteries, supercapacitors (SCs) have been identified as one of the most promising candidates to meet the demands of human sustainability. To increase the energy density of SCs, several advanced electrode materials and cell designs have been researched during the past few years. Utilizing the Faradaic charge storage process of transition metal cations, transition metal compounds have recently received attention as prospective electrode materials for SCs with high energy densities. In this work, the structure, morphology and electrochemical properties of molybdenum oxide (MoO3) films deposited via thermal evaporation technique and annealed at various temperatures were systematically investigated in order to examine the potential use of MoO3 for supercapacitors. Electrochemical analysis confirmed the pseudocapacitance characteristics of the synthesized films. The annealing temperature affects the oxidation and reduction observed in the cyclic voltammetry (CV) plots. Areal capacitance of thin films annealed at 150°C was found to be maximum and this could be attributed to the formation of hollow tube-like nanostructures which provided more active sites, than films annealed at higher temperatures. This also influences the charge storage ability of the synthesized films. It would be logical to assume that additional research in this area will result in more interesting discoveries and, eventually, the vi-ability of those promising Mo-based compounds in high-tech energy storage systems.

Novel green route synthesis of CdO nanostructures by using CdCO3 obtained by MICP and its application in photodegradation of methylene blue and Congo red

This research developed a new green route synthesis of cadmium oxide (CdO) nanostructures. First, the microbially induced carbonate precipitation was employed as a bioremediation strategy of Cd+2 in wastewater using granular sludge to precipitate it as cadmium carbonate (CdCO3) crystals. Then, the CdCO3 powder was subjected to calcination treatment at 450°C for 10, 20, 30, and 60 min to convert it to CdO and remove organic compounds. The characterization results showed that CdCO3 was converted entirely to CdO at 60 min of the thermal annealing at 450°C. CdO exhibited a simple cubic structure with an average crystallite size of 28 nm. Scanning electron microscopy images showed agglomerations composed of CdO tube-like nanostructures with an average of 60 nm in diameter. The optical energy band-gaps of the CdO nanostructures were 2.15 eV and 2.0 eV for direct and indirect transitions, respectively.Finally, the CdO nanostructures exhibited excellent removal efficiencies for Methylene blue and Congo red photodegradation at 120 min with apparent rate constants of 0.013 and 0.009 min−1, respectively.

Superhydrophobic behavior of polymer-coated nanowire-arrays as a function of interfacial affinity and etching

We have investigated the superhydrophobic behavior of coatings of polydimethylsiloxane (PDMS) and polystyrene (PS) on ZnO nanowire-arrays. PDMS produced a conformal coating on the ZnO nanowires due to high interfacial affinity between ZnO and PDMS, resulting in a large water contact angle of 168.0° (compared to 108.8° for planar PDMS surfaces) and droplet roll-off angles that were too small to measure. The superhydrophobicity of these coatings is among the largest reported for any polymeric coating. PS instead preferentially coated the bases of the ZnO nanowires and valleys between nanowires due to low interfacial affinity between ZnO and PS, resulting in a water contact angle of 149.3° (compared to 90.5° for planar PS surface) and droplet roll-off angles of 5°–8°. If, however, the ZnO nanowires were etched away after PS deposition, hollow tube-like nanostructures of PS were left behind, and exhibited a water contact angle of 164.3° and droplet roll-off angles of 1°–2°. These nanostructured PS coatings offer unique potential for food-safe superhydrophobic coatings because they consist only of PS without any inorganic components.

Effect of morphology and surface treatment on the performance of ZnO nanorod-based dye-sensitized solar cells

The effect of morphology and surface treatment on the performance of solution-grown ZnO nanorods as an electrode in a dye sensitized solar cell is demonstrated. Treatment includes the addition of EosinY during growth, post growth NaOH-based treatment and the production of nanorod-nanoparticle hybrid structures. The electrodes were sensitized using the organic indoline dye DN216 and dye-sensitized solar cells were prepared. Charge transfer dynamics and light harvesting properties were studied by absorbance spectroscopy, I–V measurements, voltage-decay measurements and electrochemical impedance spectroscopy. The introduction of EosinY to the precursor solution was found to increase the diameter of the rods and to produce nano-scale roughness. This lead to an improvement in dye loading and surface passivation against recombination leading to both an increase in VOC and JSC of the device, compared to ZnO nanorods deposited without EosinY. Subsequent treatment of as-deposited ZnO nanorods in aqueous NaOH increased the surface area by producing tube-like nanostructures, without compromising the electron mobility. When compared to untreated nanorods, this morphology improves dye loading and increases electron lifetime, which then leads to a higher fill factor and Voc. A significant increase in JSC and drastic decrease in VOC are obtained for a hybrid electrode consisting of nanorods and nanoparticles which is both caused by a higher surface area and faster back-recombination. Highest efficiencies were obtained by post-deposition treated nanorod electrodes deposited from EosinY containing solutions.

TiO2 Nanoribbons/Carbon Nanotubes Composite with Enhanced Photocatalytic Activity; Fabrication, Characterization, and Application

TiO2 nanoribbons (TiO2 NRs) loaded with FeCo-Al2O3 catalyst were synthesized and used as a precursor in the synthesis of TiO2 nanoribbons/carbon nanotubes (TiO2 NRs/CNTs) composite by a chemical vapor deposition (CVD) method. TiO2 NRs and TiO2 NRs/CNTs composite were characterized by XRD, FT-IR, TEM, SEM, EDX and UV-Vis spectrophotometer. The results revealed the formation of TiO2-B and hydrogen titanate nanoribbon like structures by the hydrothermal treatment. After loading TiO2 NRs by FeCo-Al2O3 catalyst and the CVD growth of carbon nanotubes, the synthetic TiO2 nanoribbons converted entirely to TiO2-B nanoribbons with nanopits structure. The composite composed of tube-like nanostructures forming an interlocked network from CNTs and TiO2-B NRs. The composite shows a relatively red-shifted band gap (3.09 eV), broader and stronger UV absorption band relative to TiO2 NRs. The photocatalytic properties of TiO2 NRs and TiO2 NRs/CNTs composite were studied under sunlight irradiation. The photocatalytic degradation of methylene blue (MB) dye was investigated as a function of contact time, dye concentration, and catalyst dose. The kinetics and mechanisms of degradation were discussed. TiO2 NRs/CNTs composite showed higher stability after six runs and 50% shorter irradiation time than TiO2 NRs photocatalyst.

Impedance Of 3D Nanostructured MEAs: Influence of Coating and Cell Cultivation

Impedance Of 3D Nanostructured MEAs: Influence of Coating and Cell Cultivation

1D TiO2 Nanostructures Prepared from Seeds Presenting Tailored TiO2 Crystalline Phases and Their Photocatalytic Activity for Escherichia coli in Water

TiO2 nanotubes were synthesized by alkaline hydrothermal treatment of TiO2 nanoparticles with a controlled proportion of anatase and rutile. Tailoring of TiO2 phases was achieved by adjusting the pH and type of acid used in the hydrolysis of titanium isopropoxide (first step in the sol-gel synthesis). The anatase proportion in the precursor nanoparticles was in the 3–100% range. Tube-like nanostructures were obtained with an anatase percentage of 18 or higher while flake-like shapes were obtained when rutile was dominant in the seed. After annealing at 400°C for 2 h, a fraction of nanotubes was conserved in all the samples but, depending on the anatase/rutile ratio in the starting material, spherical and rod-shaped structures were also observed. The photocatalytic activity of 1D nanostructures was evaluated by measuring the deactivation of E. coli in stirred water in the dark and under UV-A/B irradiation. Results show that in addition to the bactericidal activity of TiO2 under UV-A illumination, under dark conditions, the decrease in bacteria viability is ascribed to mechanical stress due to stirring.

Thin-Wall GaN/InAlN Multiple Quantum Well Tubes.

Thin-wall tubes composed of nitride semiconductors (III-N compounds) based on GaN/InAlN multiple quantum wells (MQWs) are fabricated by metal-organic vapor-phase epitaxy in a simple and full III-N approach. The synthesis of such MQW-tubes is based on the growth of N-polar c-axis vertical GaN wires surrounded by a core-shell MQW heterostructure followed by in situ selective etching using controlled H2/NH3 annealing at 1010 °C to remove the inner GaN wire part. After this process, well-defined MQW-based tubes having nonpolar m-plane orientation exhibit UV light near 330 nm up to room temperature, consistent with the emission of GaN/InAlN MQWs. Partially etched tubes reveal a quantum-dotlike signature originating from nanosized GaN residuals present inside the tubes. The possibility to fabricate in a simple way thin-wall III-N tubes composed of an embedded MQW-based active region offering controllable optical emission properties constitutes an important step forward to develop new nitride devices such as emitters, detectors or sensors based on tubelike nanostructures.

Synthesis of magnetite nanostructures with complex morphologies and effect of these morphologies on magnetic and electromagnetic properties

Magnetite nanostructures with different morphologies (tube, urchin and dendrite) were synthesized via hydrothermal method and consequent reduction by hydrogen gas. Magnetization and electromagnetic (EM) properties were characterized. The results showed that the morphology of the nanostructures has a major role in the microwave magnetic and dielectric properties. The surface area and shape isotropy are the key factors for changes in EM properties of different morphologies. High surface area and anisotropic elongated shape of the dendritic nanostructures lead to their high microwave permittivity, whereas for urchin-like nanostructures their very high surface area resulted to low magnetization and microwave permeability. However, high permeability and low permittivity of tube-like nanostructures caused a good impedance matching and therefore the best EM absorption performance was observed in their case. The tube-like nanostructures produced a reflection loss peak value of about −40dB at the frequency of 2GHz with the layer thickness of 2mm. The results showed that tube-like magnetite nanostructures are promising particles for efficient EM wave absorbing applications.

Tungsten carbide nanotubes supported platinum nanoparticles as a potential sensing platform for oxalic acid.

Supported tungsten carbide is an efficient and vital nanomaterial for the development of high-performance, sensitive, and selective electrochemical sensors. In this work, tungsten carbide with tube-like nanostructures (WC NTs) supported platinum nanoparticles (PtNPs) are synthesized and explored as an efficient catalyst toward electrochemical oxidation of oxalic acid for the first the time. The WC NTs supported PtNPs modified glassy carbon (GC) electrode is highly sensitive toward the electrochemical oxidation of oxalic acid. A large decrease in the oxidation overpotential (220 mV) and significant enhancement in the peak current compared to unmodified and Pt/C modified GC electrodes have been observed without using any redox mediator. Moreover, WC NTs supported PtNPs modified electrode possessed wide linear concentration ranges from 0 to 125 nM and a higher sensitivity toward the oxidation of oxalic acid (80 nA/nM) achieved by the amperometry method. The present modified electrode showed an experimentally determined lowest detection limit (LOD) of 12 nM (S/N = 3). Further, WC NTs supported PtNPs electrode can be demonstrated to have an excellent selectivity toward the detection of oxalic acid in the presence of a 200-fold excess of major important interferents. The practical application of WC NTs supported PtNPs has also been demonstrated in the detection of oxalic acid in tomato fruit sample, by differential pulse voltammetry under optimized conditions.

One-step synthesis of mesoporous Al2O3–In2O3nanofibres with remarkable gas-sensing performance to NOxat room temperature

The mesoporous Al2O3–In2O3 composites with one-dimensional (1D) nanofibres (NFs) have been fabricated via a facile one-step synthesis of the electrospinning approach, followed by appropriate thermal treatment under ambient conditions. The composite nanomaterials display high dispersion of both In2O3 and Al2O3, forming a heterostructure and mesoporous tubular structure in a broad Al : In atomic ratio up to 1 : 4. It has been found that the Al2O3 composite tube-like nanostructures not only increase efficient sites for gas adsorption, but also possess higher donor densities. Moreover, the mesoporous structure also provides effective and fast channels for fast capturing and migration of electrons. The results show that the mesoporous Al2O3–In2O3 nanotubes exhibit excellent sensing properties to NOx down to a detection limit of 291 ppb at room temperature (RT), while containing 20 at% Al2O3 (labeled as meso-20AI NTs) with an average diameter of nanoparticles of about 10 nm. With respect to the 97 ppm NOx, the maximum response of 100 was determined, 7.3 times as high as the pure In2O3 NTs. Owing to its unique composite structure, 1D meso-20AI NTs may be promising for application in gas sensors.

Sensing devices based on ZnO hexagonal tube-like nanostructures grown on p-GaN heterojunction by wet thermal evaporation

High-quality ZnO hexagonal tube-like nanostructures grown on p-type GaN heterojunction have been synthesized for sensing applications through a low-cost catalyst-free process by thermal evaporation at 800°C. The morphological, structural, and optical properties of the ZnO heterostructures have been examined. In this study, Pd/ZnO/Pd metal–semiconductor–metal gas sensor has been fabricated based on the ZnO tube-like nanostructures. The sensitivity of ZnO/p-GaN heterostructures is measured at different flow rates (25, 50, 100, and 150sccm) of H2 gas at room temperature. The highest response of the ZnO/p-GaN sensor was 1250%, when 150sccm of H2 gas was injected. In addition, Pd/Al n-ZnO/p-GaN heterojunction as an ultraviolet photodiode is demonstrated. The current–voltage curve of the heterojunction demonstrates obvious rectifying behavior in the dark and under illumination. For illumination conditions, one light source of wavelength 365nm and another at 400nm were used, sweeping the bias voltage from +4 to −4V. Under UV light at 365nm the current was almost 12 times greater than that in the dark, while under UV light at 400nm the current was 2.2 times greater than that in the dark at 3V.

Riboflavin laurate nanosuspensions as an intramuscular injection for long-term riboflavin supplementation

The aim of this study was to prepare riboflavin laurate (RFL) nanosuspensions as an intramuscular injection for long-term riboflavin supplementation. Stable RFL nanosuspensions were obtained by injecting RFL/poloxamer solution in N,N-dimethyl formamide into a trehalose solution. Long soft nanostructures initially appeared and then tube-like rigid nanostructures were obtained after removal of solvents according to the transmission electron microscopic images. The nanosuspensions had narrow size distribution and the mean size was about 300 nm. Molecular self-assembly of RFL may drive the formation of nanostructures. RFL formed a monolayer at the air/water interface and poloxamer 188 could insert into the monolayer. The nanosuspensions were intramuscularly injected into rats to provide long-term riboflavin supplementation for more than 30 days in light of body weight, food intake, and urinary riboflavin. The nanosuspensions were also used to resist the riboflavin deficiency induced by methotrexate chemotherapy. RFL nanosuspensions are a promising nanomedicine for long-term riboflavin supplementation.

Fe2O3/TiO2 Tube-like Nanostructures: Synthesis, Structural Transformation and the Enhanced Sensing Properties

The paper describes for the first time the successful synthesis of Fe(2)O(3)/TiO(2) tube-like nanostructures, in which TiO(2) shell is of quasi-single crystalline characteristic and its thickness can be controlled through adjusting the added amount of aqueous Ti(SO(4))(2) solution. The characterization of samples obtained at different stages using transmission electron microscope indicates that the outer TiO(2) shell is changed gradually from amorphous and polycrystalline phase into quasi-single crystal under thermal actions through the Ostwald ripening process, accompanying the corrosion of the central parts of Fe(2)O(3) nanorods, and the formation of small particles separating each other, leading to the special core/shell nanorods. Furthermore, Fe(2)O(3)/TiO(2) tube-like nanostructures can be transformed into Fe(2)TiO(5) nanostructures after they are thermally treated at higher temperatures. Those nanostructures exhibit enhanced ethanol sensing properties with respect to the monocomponent. Our results imply that not only hollow nanostructures, but also a novel type of nanostructures can be fabricated by the present method for nanodevices.

Highly sensitive humidity sensor based on amorphous Al2O3nanotubes

Amorphous Al2O3 nanotubes were obtained by the transformation of NH4Al(OH)2CO3 nanotubes annealed at 600 °C. The tube-like nanostructures not only increase efficient sites for gas adsorption, but also promote the dissociation of water absorbed onto the surfaces of the nanotube walls. Moreover, they also provide effective and fast channels for vapor and liquid transport. Therefore, the sensors based on Al2O3 nanotubes show high sensitivity and fast response/recovery time to humidity. The impedance changes approximately four orders of magnitude as relative humidity (RH) varies from 11% to 95% at the measured frequency of 40 Hz. Additionally, the sensor also presents relatively small hysteresis and long-term stability. For low RH levels, the protonic conductor is dominant, whereas for increasing RH levels the ionic contribution becomes prevalent. This study demonstrates that Al2O3 nanotubes have promising applications in environmental monitoring.

Superconducting single crystalline MgB 2 nanotubes

Large-scale single crystalline MgB 2 tubelike nanostructures were successfully prepared by thermal evaporation of MgB 2 particles precursors without involvement of template or patterned catalyst. The inner diameter, outer diameter and length of the as-fabricated single MgB 2 nanotube (NT) are respectively about 30 nm, 90 nm and several tens of microns. Existence of superconductivity within the products is confirmed by AC and DC magnetic susceptibility at low temperatures. The work represents the achievement to produce the bulk superconductivity with the hollow-structured morphology. Synthesis of MgB 2 NTs with bulk superconductivity may open up new possibilities for the fundamental understanding of the effect of dimensionality on superconductivity.

Shape-Controlled Synthesis of Tellurium 1D Nanostructures via a Novel Circular Transformation Mechanism

A facile surfactant-assisted solvothermal method had been employed to selectively synthesize single-crystalline tellurium nanowires and nanotubes and realize the circular transformation of wirelike and tubelike nanostructures by means of tuning the reaction time. Nanowires with an average diameter of about 23 nm were fabricated after 16 h; however, the reaction time was elongated to 28 h, these nanowires transformed into needlelike nanotubes ranging from 15 to 45 μm in length and 250−320 nm in wall thickness with cuneiform groovelike nozzles. Surprisingly, as the time continued to 45 h, nanowires with diameters in the range of 10−20 nm were obtained finally. What's more, the influence of the amount of PVP, ethanol amine, and the reaction temperature on the crystal morphology and controlled synthesis had been studied systematically. Through the exact observation of time-dependent samples in the transformation process, a micellar template-based wire-self-assembly mechanism was proposed to illuminate the tra...

Biomolecular rods and tubes in nanotechnology

Biomolecules are vitally important elements in nanoscale science and also in future nanotechnology. Their shape and their chemical and physical functionality can give them a big advantage over inorganic and organic substances. While this becomes most obvious in proteins and peptides, with their complicated, but easily controlled chemistry, other biomolecular substances such as DNA, lipids and carbohydrates can also be important. In this review, the emphasis is on one-dimensional molecules and on molecules that self-assemble into linear structures, and on their potential applications. An important aspect is that biomolecules can act as templates, i.e. their shape and chemical properties can be employed to arrange inorganic substances -- such as metals or metal compounds -- on the nanometre scale. In particular, rod- and tube-like nanostructures can show physical properties that are different from those of the bulk material, and thus these structures are likely to be a basis for new technology.