Synthesis of vanadium oxide nanotubes via an ultrasonic method

Vanadium oxide nanotubes were synthesized using V₂O₅ powder as the precursor and hexadecylamine as the structure-directing template using a sol-gel reaction method followed by a one-step hydrothermal treatment. The effect of ultrasonics on the formation of nanotubes is reported. The structure and morphology of the nanotubes were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The inner and outer diameters of the nanotubes varied from 20 to 40 nm and 80 to 100 nm, respectively. The nanotubes measured several micrometers in length.     

Facile preparation of stabilized polymeric nanotubes using sacrificial yttrium hydroxide nanotubes as template and block copolymer micelles as precursor

We report here facile preparation of stabilized polymeric nanotubes with a hair-like shell using yttrium hydroxide nanotubes as the sacrificial template and block copolymer micelles as the precursor, and orientation of the polymeric nanotubes encapsulating magnetic particles under magnetic field.     

Multi-walled BN nanotubes synthesized by carbon-free method

Pure multi-walled BN nanotubes were synthesized via a carbon-free chemical vapor deposition process using boron and gallium oxide mixture as reaction precursor. Transmission electron microscopy was used to investigate their structure, morphology and defects. The wall deformation, dependent on tube diameter, was observed and explained in terms of strain relaxation of bond rotation. Opposed to carbon nanotubes, bending of BN nanotubes typically results in fracture at their concave side. Ring defect-related mechanism was proposed to interpret the fracture. The ring defects also result in the formation of a nanocone with 300° disclination. The nanocones end up with BN nanotubes exhibiting the small innermost shell ∼0.4 nm in diameter.     

La~2NiO~4催化制备纳米碳管

制备了四方结构复合氧化物La~2NiO~4,并以其为催化剂前体,甲烷和一氧化碳为碳,合成出大量高纯度的纳米碳管。XRD结果表明La~2NiO~4经还原后,在La~2O~3的隔离作用下Ni晶粒实现纳米级均匀分散。利用TEM,HRTEM,SEM,XRD,Raman等手段对所制备的纳米碳管进行了观察和表征。所制备的纳米碳管管径均匀、石墨化程度较高,该法制备纳米碳管工艺简单、产量较高,产品易于纯化。     

Synthesis of high purity single-walled carbon nanotubes in high yield

A simple method for the synthesis of high purity single wall carbon nanotubes has been developed by using nickel formate as a precursor for the formation of nearly mono-dispersed nickel seed-nanoparticles as catalysts in the CVD growth process.     

Selective synthesis of boron nitride nanotubes by self-propagation high-temperature synthesis and annealing process

Four types of BN nanotubes are selectively synthesized by annealing porous precursor in flowing NH₃ and NH₃/H₂ atmosphere at temperature ranging from 1000 to 1200 °C in a vertical furnace. The as-synthesized BN nanotubes, including cylinder, wave-like, bamboo-like and bubble-chain, are characterized by XRD, FTIR, Raman, SEM, TEM and HRTEM. Three phenomenological growth models are proposed to interpret growth scenario and structure features of the four types of BN nanotubes. Selectivity of nanotubes formation is estimated as approximately 80-95%. The precursor containing B, Mg, Fe and O prepared by self-propagation high-temperature synthesis (SHS) method plays a key role in selective synthesis of the as-synthesized BN nanotubes. Chemical reactions are also discussed.     

Composite polymer nanofibers with carbon nanotubes and titanium dioxide particles

Composite nanofibers containing nanometric TiO2 particles and multiwalled carbon nanotubes dispersed in poly(acrylonitrile) (PAN) were prepared by the electrospinning technique. The structure and quality of the precursor dispersions were evaluated by cryo-transmission electron microscopy. The fabricated nanofibers, the diameters of which were in the 20-200 nm range, contained well-oriented nanotubes and spherical TiO2 nanoparticles in close proximity. Such nanofibers are under investigation as new photocatalytic reactor elements.     

High-yield bamboo-shaped carbon nanotubes from cresol for electrochemical application

High-yield bamboo-shaped carbon nanotubes (BCNTs) have been produced by using cresol as the precursor, for the first time and there are almost no straight CNTs or amorphous carbon found in the product: the role of cresol in promoting the growth of BCNTs is discussed; improved cycle stability and electric conductivity of the BCNTs as an anode additive in a lithium ion battery are achieved.     

Formation and characterization of mesostructured silica nanotubes

The multi-walled mesoporous silica nanotubes are prepared using cetyltrimethylammonium bromize (CTAB) as the surfactant micellar template and tetraethylorthosilicate (TEOS) as the silica precursor via a one-step wet chemical approach. The synthesized tubes are found to be double/triple walled and of amorphous nature. Their diameter and the length are about 100 nm to 1 μm and about 0.1–20 μm, respectively. The specific surface area approaches 1,488 m²/g. Based on the transmission electron microscopy analysis, it is inferred that the formation of the double/triple walled silica nanotubes is associated with the lamellar curling mechanism. A striking photoluminescence effect is detected in the mesostructured silica nanotubes. These nanotubes are expected to be a promising material for various applications such as gas storage, catalyst, or catalyst supports.     

A simple method for controllable preparation of polymer nanotubes via a single capillary electrospinning

Polymer nanotubes have been successfully electrospun via a single capillary spinneret instead of coaxial electrospinning. By altering the volume of ethanol under a fixed amount of poly(vinyl pyrrolidone) (PVP) and tetraethyl orthosilicate (TEOS) in the precursor, the nanotubes could be controllably produced for a proper concentration of PVP solution. Further investigation showed that the diameters of nanotubes, the thicknesses of nanotube walls, and the ratios of the thickness of the nanotube wall to the nanotube diameter (RTNWND) could be controlled by altering the amount of TEOS in the precursor. With increasing the ratios of TEOS to PVP solution, the nanotube diameters were increased and the nanotube walls were decreased. Thus, the RTNWND were decreased. The applied voltages also have an effect on the nanotube diameter and the thickness of the nanotube wall, but little on the RTNWND. The effects of ethanol and TEOS on evaporation and phase separation processes were discussed.     

Utilization of iron oxide film obtained by CVD process as catalyst to carbon nanotubes growth

Thin films of Fe₂O₃ were obtained on silica glass substrates through the thermal decomposition of ferrocene in air. These films were characterized by Raman spectroscopy and X-ray diffractometry (XRD), and subsequently used as catalyst on the growth of carbon nanotubes, using benzene or a benzene solution of [Fe₃(CO)₁₂] as precursor. A great amount of a black powder was obtained as product, identified as multi-walled carbon nanotubes by XRD, Raman spectroscopy and transmission electron microscopy. The carbon nanotubes formed through the pyrolysis of the [Fe₃(CO)₁₂] solution were identified as structurally better than the one obtained by the pyrolysis of pristine benzene.     

Catalytic synthesis of bamboo-like multiwall BN nanotubes via SHS-annealing process

Bamboo-like multiwall boron nitride (BN) nanotubes were synthesized via annealing porous precursor prepared by self-propagation high temperature synthesis (SHS) method. The as-synthesized BN nanotubes were characterized by the field emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), Raman and Fourier transform infrared (FTIR) spectroscopy. These nanotubes have uniform diameters of about 60 nm and an average length of about 10 μm. Four growth models, including tip, base, based tip and base-tip growth models, are proposed based on the catalytic vapor-liquid-solid (VLS) growth mechanism for explaining the formation of the as-synthesized bamboo-like BN nanotubes. Chemical reactions and annealing mechanism are also discussed.     

A multistep attachment process: Transformation of titanate nanotubes into nanoribbons

The mechanism of the conversion of titanate nanotubes into nanoribbons is of considerable interest.The details of the transformation processes involved when nanoribbons are produced from a P25 TiO 2 powder precursor by alkaline hydrothermal treatment have been investigated systematically by transmission electron microscopy.A multistep attachment model is proposed for the growth at the early stage of coarsening.The treatment duration has a strong effect on the change in product morphology from hollow nanotubes into nanoribbons,since the nanotubes cannot retain their morphology in the strong alkaline solution for extended periods of time.Most of the nanotubes were etched and dissolved,providing the nutrients for subsequent nanoribbon growth.Some stable nanotubes grew spirally internally to form nanowires or became connected together to form rafts which acted as the grains for nanoribbon growth.With increasing hydrothermal time,a large number of nanotubes and other fragments became attached to the grains which began to grow larger and eventually formed the nanoribbons,in a process in which the stepped faces and kinked faces became fused and were eliminated while the flat faces were retained in the nanoribbon morphology.     

EuF3 nanotubes fabricated via Eu(NO3)3/cysteamine as precursor and their derived thermosensitive nanogels

In this paper, we report a novel solution route to obtain rare earth nanotubes. Firstly, the complex of Eu(NO₃)₃/cysteamine (Eu-Complex) was used as the precursor, then nanotubes of EuF₃ were fabricated from the precursor and NaF. Secondly, the EuF₃ nanotubes reacted with acrylic acid (AA) and converted into vinyl decorated nanotubes. Finally, the decorated nanotubes copolymerized with N-isopropylacrylamide via free radical polymerization and thermosensitive EuF₃ nanotubes/poly (N-isopropylacrylamide) (PNIPAm) nanogels were prepared. In order to investigate the mechanism to produce the nanotubes, the morphology structures of samples at different reaction stages were studied via TEM, and the formation mechanism of nanotubes is proposed. The chemical composition was confirmed by FTIR, XRD, XPS and elemental analyzer. The optical property of the as-prepared nanotubes and the nanogels was investigated in detail by photoluminescence (PL). The results suggest that, compared with their bulk counterparts, the nanogels present different thermosensitive fluorescence behavior, for instance, around their low critical solution temperature (LCST), the variation of PL emission intensity of the nanogels is slightly gentler.     

Template-based electrophoretic growth of PbZrO<Subscript>3</Subscript> nanotubes

Lead zirconate (PbZrO₃) nanotubes have been grown using porous anodic alumina templates. Sol–gel electrophoresis technique was utilized to form the nanotubes on the pore walls. The alumina templates were prepared using various anodizing voltages and times to achieve different pore diameters and lengths. Phosphoric acid solution was employed as the anodizing electrolyte. Stabilized lead zirconate sols were prepared using lead acetate trihydrate and an alkoxide precursor of zirconium. Acetic acid was used as the modifier. The prepared sols were driven into the template channels under various electrophoretic voltages and times, and the effect of the electrophoresis parameters on the formation of nanotubes was investigated. The filled templates were dried at 100 °C and sintered at 700 °C. Scanning and transmission electron microscopy (SEM and TEM) investigations demonstrated the tubular form of the lead zirconate arrays. The SEM investigations also showed the nanotubes have been efficiently grown in the template pores. The TEM studies further confirmed the polycrystalline nature of the tubes.     

A novel precursor for synthesis of pure boron nitride nanotubes

A novel precursor, a mixture of B2O2 and Mg which is generated in situ by reacting B and MgO at 1300 degrees C, can be used to effectively synthesize bulk amounts of pure BN nanotubes with Mg evaporated from the final product; transmission electron microscope observation for the synthesized BN nanotubes indicates that defects present strongly depend on the tube diameter.     

Low-temperature catalytic preparation of multi-wall MoS_2 nanotubes

Since the first report on inorganic fullerene-like WS2 polyhedra and nanotubes by Tenne et al.[1] in 1992, this kind of nanostructural materials have become extensive research topics owing to their unique electronic structures. WS2 and MoS2 nanomaterials have shown potential applications in the fields of scanning probe microscopy[2], solid-state lubrication[3], heterogeneous catalysis[4], and electrochemical hydrogen storage[5]. Up to now, a great deal of progress has been achieved in the st…     

Patterning catalyst via inkjet printing to grow single-walled carbon nanotubes

We demonstrated a method to pattern catalyst via inkjet printing to grow SWNTs, using metal salt solutions as the inks and an ordinary office-use printer. We printed water solutions of cobalt acetate on hydrophilic Si substrates and grew high quality SWNT films.     

Fabrication of silica nanotubes using silica coated multi-walled carbon nanotubes as the template

Silica nanotubes were synthesized using the multi-walled carbon nanotubes (MWCNTs) as the template material. First, we prepared silica coated MWCNT composites by surface oxidation of MWCNTs using KMnO(4) in the presence of a phase transfer catalyst and followed by grafting of 2-aminoethyl 3-aminopropyl trimethoxy silane, AEAPS. The amine groups in grafted AEAPS on MWCNTs could activate the silica shell formation by acid-base interaction. The synthesized silica was formed a uniform layer on MWCNTs with a controllable thickness and possessed sturdy 3-dimensional stability. After calcinations at 800 degrees C, the inner MWCNTs of the composite were completely decomposed and the outer silica shell layer maintained without distortion of its original shape. Finally, we could obtain the silica nanotubes having 13.0 nm of average layer thickness.     

Rational growth of Bi2S3 nanotubes from quasi-two-dimensional precursors

Synthesis of Bi2S3 nanotubes from rolling of the quasi-two-dimensional (2-D) layered precursor represents new progress in the synthetic approach and adds new members to the present inorganic fullerene family. These nanotubes display multiwalled structures that resemble that of a multiwalled carbon nanotube. The successful synthesis of Bi2S3 nanotubes highlights the feasibility of inorganic fullerene-like structures from other chemicals that possess layered crystalline structures, not only the well-known 2-D family, but possibly also those quasi-2-D members.