Nanotube Research Papers - Academia.edu (original) (raw)

Growth mechanism of a single wall carbon nanotube on the surface of a nickel nanoparticle in the CVD method has been investigated by classical molecular dynamics method. Using first principles methods, we have first constructed a classical potential to describe the interaction between a carbon atom and the nickel surface. The important ingredient in this potential is its coordination number dependence, which also provides the key to the growth mechanism of the nanotube. From the simulations, it is proposed that the growth of an armchair nanotube takes place via attachment of dimers to its end which is in contact with the nickel surface. The effect of nickel nanoparticleÕs radius on the attachment barrier is also discussed.

- by
- •
- Materials Science, Nanotechnology, Molecular Dynamics, Growth

The emerging fields of nanoscience and nanoengineering are leading to unprecedented understanding and control over the fundamental building blocks of all physical matter. This is likely to change the way almost everythingfrom vaccines to computers to automobile tires to objects not yet imagined-is designed and made. Use it as a prefix for any unit like a second or a meter and it means a billionth of that unit. A nanosecond is one billionth of a second. And a nanometer is one billionth of a meter-about the length of a few atoms lined up shoulder to shoulder. A world of things is built up from the tiny scale of nanometers. The thousands of cellular proteins and enzymes that constitute eg., The human bodies are a few nanometers thick. Enzymes typically are constructions of thousands of atoms in precise molecular structures that span some tens of nanometers. That kind of natural nanotechnology is about ten times smaller than some of the smallest synthetic nanotechnology that has been prepared until now. The individual components of an Intel Pentium III microprocessor span about 200 nanometers. This is the reason that computing is so powerful and easy these days. Nanotechnology makes microelectronics to be mere hints of what will come from engineering that begins on the even smaller scales of nanostructures. Nanostructure science and technology is a broad and interdisciplinary area of research and development activity that has been growing explosively worldwide in the past few years. It has the potential for revolutionizing the ways in which materials and products are created and the range and nature of functionalities that can be accessed. It is already having a significant commercial impact, which will assuredly increase in the future. In this paper, we have reviewed briefly some nano materials related works already published or available in the internet with organized manner.

- by Prajit Ghosh
- •
- Nanoparticle, Nanowire, Nanocomposite, Nanotube

Titanate nanotubes were synthesized by hydrothermal method at 105 C for 24 h (setting temperature) using natural leucoxene mineral as the starting material. The samples were characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The prepared nanotubes showed internal diameter of 4-6 nm, external diameter of 8-10 nm, and the length of 0.2-1 μm. This synthesis method provided a simple route to fabricate nanostructured material from low cost natural mineral using Thai autoclave unit.

- by Ana Olvera
- •
- Materials Science, Nanotechnology, Nanoscience, TiO2

This paper reports on a methodology for synthesizing vertical arrays of hollow platinum nanotubes with [111] single-crystalline nanoflakes. Initially, single-component nickel nanorods were fabricated with the aid of AAO templates and electrochemical deposition. When the resulting nickel nanorods were immersed in a Pt-ion-containing aqueous solution, the nickel metal dissolved into Ni2+ ions through spontaneous galvanic replacement with Pt ions. However, the direct replacement between nickel nanorods and Pt ions led to an irregular architecture in the resulting deposition of platinum. Instead, a pitting corrosion pretreatment of the nickel nanorods produced nucleation sites for replacement with the Pt ions. This step was critical for accelerating the interfacial replacement reaction rate and the formation of the regular platinum nanotubes with ultrathin superficial nanoflakes. We found that the Kirkendall effect was operative in the formation of platinum nanotubes.

- by Lichun Liu
- •
- Chemistry, Catalysis, Nanofabrication, Nano Synthesis

The unique features of axial, torsional, transverse and radial breathing vibrations are captured for armchair and zigzag singlewalled boron nitride nanotubes (BNNTs) based on molecular mechanics simulations and continuum mechanics theories. Equivalent Young's modulus 1 TPa and shear modulus 0.4 TPa are obtained independent of the chirality of BNNTs. In particular, a distorted optimized structure is observed for the first time for BNNTs with sufficiently large diameter and length. It is found that the deformed structures result in behaviours of BNNTs deviating from those of classical columns/beams. Such symmetry-breaking could also exert significant impacts on the structural instability (buckling) and electronic properties of BNNTs that are sensitive to the structural symmetry.

MODIFICATION OF MIXED STRUCTURE TiO 2 NANOPOROUS-NANOTUBE ARRAYS WITH CdS NANO PARTICLE AND THEIR PHOTO ELECTRO CHEMICALPROPERTIES . In thiswork, a mixed structure TiO 2 with a top nanoporous layer and an underneath highly ordered nanotube arrays layer (TNPs-NTAs) were prepared by anodic oxidation of Ti foil under controlled anodization time in an electrolyte containing fluoride ion,water and ethylene glycol. CdS nanoparticles (NPs) was deposited onto the mixed structure of TiO 2 by Successive Ionic Layer Adsorption and Reaction (SILAR) with an aim toward tuning the photoelectrochemical performance to visible region. Themorphology, elemental composition, crystal structure, optical properties and photoelectrochemical performance of TNPs-NTs and CdS modified (CdS/TNP-NTAs) samples were characterized by Field Emisi Scanning Electron Microscope (FESEM), Electron Dispersive Spectroscopy (EDS), X-Ray Diffractometer (XRD), Diffuse Reflactance Spectroscopy (DRS) and electrochemical working ...

- by Hedi Surahman
- •
- Materials Science, Nanotube

We report the morphology-tuned synthesis of single-crystalline V5Si3 nanotubes and nanowires. Free-standing hexagonal V5Si3 nanostructures are grown on a vanadium foil substrate placed on Si powder by a chemical vapor deposition method. By controlling the reaction time and substrate temperature, we have succeeded in morphology tuning of V5Si3 nanotubes and nanowires. When the downstream temperature is fixed at 950 °C, V5Si3 nanotubes are formed with the reaction time of 5 min and V5Si3 nanowires are obtained with the reaction time of 15 min. With the downstream temperature of 950 °C and the reaction time of 15 min, when Si powder is mixed with carbon powder to the Si composition of 10-50%, both nanotubes and nanowires are simultaneously formed on the vanadium foil along the temperature gradient. Single-crystalline V5Si3 nanotubes thus synthesized are the first metal silicide nanotubes reported so far.

- by Sunghun Lee
- •
- Nanowire, Chemical Vapor Deposition, Nanotube

Mass production of carbon nanotubes (CNTs) by a cost effective process is still a challenge for further research and application of CNTs. Our group has focussed on the deposition of CNTs on a continuously-fed carbon substrate via arc discharge at atmospheric pressure. This process produces MWNTs using carbon from the substrate. The method differs in other respects from the conventional batch arc discharge method by using lower currents (< 20 A) and larger inter-electrode gaps. To help define the local conditions of nanotube growth, the substrate surface temperature (T s ) was measured by optical pyrometry. Here, we report the influence of inter-electrode gap, substrate velocity and arc current on this temperature. It is found that carbon nanotube growth is favourable over a certain temperature range and retention time in the arc. To further understand the effect of arc parameters, we used a computer simulation to model the arc plasma. Computational fluid dynamic (CFD) software, Comsol Multiphysics, was used to simulate the temperature distribution and flow properties of the arc plasma. It was found necessary to include dusty plasma conductivity near to the electrodes to adequately represent observed arc behaviour.

- by Dan Eusoff
- •
- Nanotechnology, Nanoscience, Land Surface Temperature, Nanotube

Carbon nanotubes (CNTs) constitute a class of nanomaterials that possess characteristics suitable for a variety of possible applications. Their compatibility with aqueous environments has been made possible by the chemical functionalization of their surface, allowing for exploration of their interactions with biological components including mammalian cells. Functionalized CNTs (f-CNTs) are being intensively explored in advanced biotechnological applications ranging from molecular biosensors to cellular growth substrates. We have been exploring the potential of f-CNTs as delivery vehicles of biologically active molecules in view of possible biomedical applications, including vaccination and gene delivery. Recently we reported the capability of ammonium-functionalized single-walled CNTs to penetrate human and murine cells and facilitate the delivery of plasmid DNA leading to expression of marker genes. To optimize f-CNTs as gene delivery vehicles, it is essential to characterize their interactions with DNA. In the present report, we study the interactions of three types of f-CNTs, ammonium-functionalized single-walled and multiwalled carbon nanotubes (SWNT-NH 3 + ; MWNT-NH3 +), and lysine-functionalized single-walled carbon nanotubes (SWNT-Lys-NH3 +), with plasmid DNA. Nanotube-DNA complexes were analyzed by scanning electron microscopy, surface plasmon resonance, PicoGreen dye exclusion, and agarose gel shift assay. The results indicate that all three types of cationic carbon nanotubes are able to condense DNA to varying degrees, indicating that both nanotube surface area and charge density are critical parameters that determine the interaction and electrostatic complex formation between f-CNTs with DNA. All three different f-CNT types in this study exhibited upregulation of marker gene expression over naked DNA using a mammalian (human) cell line. Differences in the levels of gene expression were correlated with the structural and biophysical data obtained for the f-CNT:DNA complexes to suggest that large surface area leading to very efficient DNA condensation is not necessary for effective gene transfer. However, it will require further investigation to determine whether the degree of binding and tight association between DNA and nanotubes is a desirable trait to increase gene expression efficiency in vitro or in vivo. This study constitutes the first thorough investigation into the physicochemical interactions between cationic functionalized carbon nanotubes and DNA toward construction of carbon nanotube-based gene transfer vector systems.

- by ravi singh
- •
- Chemistry, Scanning Electron Microscopy, Carbon Nanotubes, Carbon Nanotube

"Background: Natural organic matters (NOMs) have the main role in formation of trihalomethanes. These compounds are in natural water sources due to biological activities. In the presented study, adsorption and separation of humic acid as an index of natural organic matters using multi-walled carbon nanotubes is evaluated.
Methods: The experiments were carried out in bath adsorption reactors with different concentrations of humic acid. The effects of pH, adsorbent dose, national concentrations of humic acid and contact time as study variables were tested in separated experiments, as well as, kinetic and isotherm models of the adsorption process were determined.
Results: The results showed that the adsorption follows Freundlich isotherm model and pseudo second-order kinetic equation. The removal percent of humic acid reached to higher than 90% with dosage of 1g/l of nanotube.
Conclusion: Adsorption of humic acid from water by multi-walled carbon nanotubes is an efficient alternative pretreatment method in water treatment plants."

- by Journal of Human Environment and Health Promotion JHEHP
- •
- Water, Adsorption, Humic acid, Nanotube

We report about the ambient conditions and electrolytes influence on the synthesis of self-organized titania nanotube arrays prepared by anodic oxidation. Arrays of randomly disordered Titanium dioxide nanotubes with pores diameter ranging between 60 and 100 nm, wall thickness of 25 up to 40 nm and around 300 nm nanotubes length, can be prepared under HF electrolyte and its mixtures with sulphuric acid at RT anodization.

- by Victor de la Prida
- •
- Mechanical Engineering, Condensed Matter Physics, Materials Science, Nanowire

TiO 2 nanotube arrays are promising candidates for applications such as photocatalysis and for potential employment in spin-electronic (spintronic) devices. The functionality of TiO 2-based nanotubes is highly dependent on their structure (microstructure and crystallographic symmetry) and magnetic properties. Unified understanding of the influence of these factors on the electronic structure of TiO 2 is of paramount importance towards engineering these materials. This Dissertation aims at investigating the correlations of the crystallinity, crystal structure, electronic structure and magnetic properties of TiO 2 nanotubes, with potential relevance to their functionality. Self-ordered arrays of amorphous TiO 2 nanotubes (pure and Fe-doped with cationic concentration of ~2.1 at%) were synthesized by the electrochemical anodization technique, followed by subjecting them to thermal treatments up to 450 °C to crystallize these nanostructures. A variety of probes – morphological, structur...

- by Pegah Hosseinpour
- •
- Materials Science, Catalysis, Crystal structure, Magnetism

- by Dr. Sukhendu Jana
- •
- Nanoparticle, Nanowire, Nanocomposite, Nanotube

Microcavities based on group-III nitride material offer a notable platform for the investigation of light-matter interactions as well as the development of devices such as high efficiency light emitting diodes (LEDs) and low-threshold nanolasers. Disk or tube geometries in particular are attractive for low-threshold lasing applications due to their ability to support high finesse whispering gallery modes (WGMs) and small modal volumes. In this article we present the fabrication of homogenous and dense arrays of axial InGaN/GaN nanotubes via a combination of displacement Talbot lithography (DTL) for patterning and inductively coupled plasma top-down dry-etching. Optical characterization highlights the homogeneous emission from nanotube structures. Power-dependent continuous excitation reveals a non-uniform light distribution within a single nanotube, with vertical confinement between the bottom and top facets, and radial confinement within the active region. Finite-difference time-domain simulations, taking into account the particular shape of the outer diameter, indicate that the cavity mode of a single nanotube has a mixed WGM-vertical Fabry-Perot mode (FPM) nature. Additional simulations demonstrate that the improvement of the shape symmetry and dimensions primarily influence the Q-factor of the WGMs whereas the position of the active region impacts the coupling efficiency with one or a family of vertical FPMs. These results show that regular arrays of axial InGaN/GaN nanotubes can be achieved via a low-cost, fast and large-scale process based on DTL and top-down etching. These techniques open a new perspective for cost effective fabrication of nano-LED and nano-laser structures along with biochemical sensing applications.

- by Pierre-Marie COULON and +1
- •
- Nanoscience, Nanotube, Microcavity, Whispering Gallery Modes

In this work, we demonstrate a simple methodology for synthesizing vertical or free-standing palladium (Pd) nanotube arrays in a highly efficient fashion. The hydroxyl-terminated surface of the nanochannel in an alumina membrane is used to form an interfacial double layer by specifically adsorbing hydrogen ions (H+) from an acidic solution and leaving counterions to predominate in the diffuse layer. Locally enriched H+ ions at the wall of alumina nanochannel produce a higher content of adsorbed hydrogen on the electrochemically reduced metallic Pd surface under an appropriate electric potential. The higher Pd growth rate at peripheral positions rather than elsewhere in the nanochannel was due to the dual reductions of Pd(II) compound by hydrogen and electric potential. The disparity of growth rates in combination with diffusion-controlled growth efficiently gives rise to the formation of nanotubes with wall thicknesses as narrow as 6 nm.

- by Lichun Liu
- •
- Electrodeposition, Nanotube, AAO, Palladium