共查询到20条相似文献,搜索用时 46 毫秒
1.
Kim Bolton Anders Börjesson Wuming Zhu Hakim Amara Christophe Bichara 《Nano Research》2009,2(10):774-782
Density functional theory (DFT) and tight binding (TB) models have been used to study systems containing single-walled carbon
nanotubes (SWNTs) and metal clusters that are of relevance to SWNT growth and regrowth. In particular, TB-based Monte Carlo
(TBMC) simulations at 1000 or 1500 K show that Ni atoms that are initially on the surface of the SWNT or that are clustered
near the SWNT end diffuse to the nanotube end so that virtually none of the Ni atoms are located inside the nanotube. This
occurs, in part, due to the lowering of the Ni atom energies when they retract from the SWNT to the interior of the cluster.
Aggregation of the atoms at the SWNT end does not change the chirality within the simulation time, which supports the application
of SWNT regrowth (seeded growth) as a potential route for chirality-controlled SWNT production. DFT-based geometry optimisation
and direct dynamics at 2000 K show that Cr and Mo atoms in Cr5Co50 and Mo5Co50 clusters prefer to be distributed in the interior of the clusters. Extension of these calculations should deepen our understanding
of the role of the various alloy components in SWNT growth.
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2.
3.
A novel process is demonstrated whereby dense arrays of single-walled carbon nanotubes (SWNT) are grown directly at the interface
of a carbon material or carbon fiber. This growth process combines the concepts of SWNT tip growth and alumina-supported SWNT
base growth to yield what we refer to as “odako” growth. In odako growth, an alumina flake detaches from the carbon surface
and supports catalytic growth of dense SWNT arrays at the tip, leaving a direct interface between the carbon surface and the
dense SWNT arrays. In addition to being a new and novel form of SWNT array growth, this technique provides a route toward
future development of many important applications for dense aligned SWNT arrays.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.
This article is published with open access at Springerlink.com 相似文献
4.
Cyrille Richard Nathalie Mignet Céline Largeau Virginie Escriou Michel Bessodes Daniel Scherman 《Nano Research》2009,2(8):638-647
The possibility of delivering DNA efficiently to cells represents a crucial issue for the treatment of both genetic and acquired
diseases. However, even although the efficiency of non-viral transfection systems has improved in the last decade, none have
yet proven to be sufficiently effective in vivo. We report herein our results on the functionalization of single-walled carbon nanotubes (SWNT) and multi-walled carbon nanotubes
(MWNT) by two cationic amphiphiles (lipid RPR120535 and pyrenyl polyamine), their use for the complexation of plasmid DNA,
and their efficiency in transfecting cells in vitro. The experiments have shown that the efficiency of transfection is higher when using SWNT instead of MWNT, and that transfection
efficiency is similar or slightly higher when using nanoplexes (SWNT/lipid RPR120535/DNA) instead of lipoplexes (lipid RPR120535/DNA)
and several orders of magnitude higher than that of naked DNA. This study therefore shows both that the transfection is better
when using SWNTs and that it is dependent on the nature of the amphiphilic molecules adsorbed on the nanotubes.
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5.
Ernesto Joselevich 《Nano Research》2009,2(10):743-754
The organization of carbon nanotubes into well-defined straight or curved geometries and arrays on surfaces is a critical
prerequisite for their integration into nanocircuits and a variety of functional nanosystems. We review the recent development
of a new approach to carbon nanotube organization based on self-organized growth directed by well-defined crystal surfaces,
or “nanotube epitaxy”. We identify three different modes of surface-directed growth, namely by atomic rows, atomic steps,
and nanofacets. Particular emphasis is given here to the combinations of such surface-directed growth with external forces—like
those exerted by an electric field or gas flow—for the creation of well-defined complex geometries, including crossbar architectures,
serpentines, and coils.
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6.
Single-walled carbon nanotube (SWNT) thin film electrodes have been printed on flexible substrates and cloth fabrics by using
SWNT inks and an off-the-shelf inkjet printer, with features of controlled pattern geometry (0.4–6 cm2), location, controllable thickness (20–200 nm), and tunable electrical conductivity. The as-printed SWNT films were then
sandwiched together with a piece of printable polymer electrolyte to form flexible and wearable supercapacitors, which displayed
good capacitive behavior even after 1,000 charge/discharge cycles. Furthermore, a simple and efficient route to produce ruthenium
oxide (RuO2) nanowire/SWNT hybrid films has been developed, and it was found that the knee frequency of the hybrid thin film electrodes
can reach 1,500 Hz, which is much higher than the knee frequency of the bare SWNT electrodes (˜158 Hz). In addition, with
the integration of RuO2 nanowires, the performance of the printed SWNT supercapacitor was significantly improved in terms of its specific capacitance
of 138 F/g, power density of 96 kW/kg, and energy density of 18.8 Wh/kg. The results indicate the potential of printable energy
storage devices and their significant promise for application in wearable energy storage devices.
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7.
Current methods of synthesizing single-walled carbon nanotubes (SWNTs) result in racemic mixtures that have impeded the study
of left- and right-handed SWNTs. Here we present a method of isolating different SWNT enantiomers using density gradient ultracentrifugation.
Enantiomer separation is enabled by the chiral surfactant sodium cholate, which discriminates between left- and right-handed
SWNTs and thus induces subtle differences in their buoyant densities. This sorting strategy can be employed for simultaneous
enrichment by handedness and roll-up vector of SWNTs having diameters ranging from 0.7 to 1.5 nm. In addition, circular dichroism
of enantiomer refined samples enables identification of high-energy optical transitions in SWNTs.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
8.
A simple method for high-yield, chemical vapor deposition (CVD) synthesis of serpentine carbon nanotubes, employing quartz
substrates and a molecular cluster catalyst, is described. The growth mechanism is analyzed by controlled addition of nanoscale
barriers, and by mechanical analysis of the curved sections. The serpentine structures are used to study the electrical transport
properties of parallel arrays of identical nanotubes, which show three-terminal conductance that scales linearly with the
number of nanotube segments.
This article is published with open access at Springerlink.com 相似文献
9.
The stability of open edged multi-walled carbon nanotubes has been investigated by using in situ high resolution transmission
electron microscopy at elevated temperatures. Formation of inter-shell structures was experimentally observed for the first
time and attributed to a robust interaction between adjacent concentric shells (so-called lip-lip interaction). The fl uctuating
behavior of the inter-shell structures suggests a mechanism by which the carbon atoms can pass in or out through the inter-shell
edges during carbon nanotube growth or shrinkage processes.
This article is published with open access at Springerlink.com 相似文献
10.
Pavel Nikolaev William Holmes Edward Sosa Peter Boul Sivaram Arepalli 《Nano Research》2009,2(10):818-827
Many potential applications of carbon nanotubes are expected to benefit from the availability of single-walled carbon nanotube
materials enriched in metallic species, and specifically armchair nanotubes. The present work focuses on the modification
of the pulsed laser vaporization (PLV) technique to selectively produce certain carbon nanotube structures. Nanotube nuclei
were “warmed-up” with an additional laser pulse, timed to coincide approximately with the nucleation event. The effect of
the second laser on the carbon vapor temperature was studied by emission spectroscopy. Nanotube type populations with and
without warm-up were compared by means of absorption, photoluminescence, and Raman spectroscopy. It was found that the warm-up
of nanotube nuclei with a laser pulse has a noticeable, albeit small, effect on the nanotube population. The intensity of
spectral features associated with (9,7) nanotube and its large chiral angle neighbors increased, while small chiral angle
nanotubes decreased, with exception of the (15,0) tube. This experiment demonstrates that nanotube population during PLV synthesis
can be manipulated in a controlled fashion.
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11.
Novel photodetectors based on double-walled carbon nanotube film/TiO2 nanotube array heterodimensional contacts 总被引:1,自引:0,他引:1
A new kind of photodetector based on a double-walled carbon nanotube (DWCNT) film and a TiO2 nanotube array with hetrodimensional non-ohmic contacts has been fabricated. Due to the dimensionality difference effect,
the DWCNT film/TiO2 nanotube array photodetector exhibits a much higher photocurrent-to-dark current ratio and photoresponse relative to an Au
film/TiO2 nanotube array device, even at small bias voltage. The photocurrent-to-dark current ratio reached four orders of magnitude
and a high photoresponse of 2467 A/W was found upon irradiation at 340 nm. Furthermore, the photosensitive regions could be
extended into the visible range. The photocurrent-to-dark current ratio reached approximately three orders of magnitude upon
irradiation at 532 nm, where the photon energy is much lower than the band gap of TiO2.
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12.
Various materials have been found to “catalyze” carbon nanotube growth in chemical vapor deposition (CVD) when they become
nano-sized particles. These involve not only metals, such as Pd, Pt, Au, Ag, and Cu, but also semiconductors, such as Si,
Ge, and SiC. Alumina and diamond nanoparticles also produce carbon nanotubes. These “catalysts”, which are better called “seeds”,
can be categorized into two types: one type forms a eutectic liquid or highly-mobile alloy with carbon, and carbon atoms precipitate
from the eutectic alloy; the other type remains as a solid phase and form a carbon surface layer during CVD growth. In this
paper, we review recent studies of SWCNT growth with these non-iron-group materials and highlight the mechanisms involved.
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13.
We demonstrate the role of catalysts in the surface growth of single-walled carbon nanotubes (SWNTs) by reviewing recent progress
in the surface synthesis of SWNTs. Three effects of catalysts on surface synthesis are studied: type of catalyst, the relationship
between the size of catalyst particles and carbon feeding rates, and interactions between catalysts and substrates. Understanding
of the role of catalysts will contribute to our ability to control the synthesis of SWNTs on various substrates and facilitate
the fabrication of nanotube-based devices.
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14.
Using carbon nanotubes as nanobarriers, the growth of single-walled carbon nanotubes (SWNTs) on a quartz surface can be terminated. First, carbon nanotube nanobarriers were grown on a quartz surface by the gas flow-directed growth mode. Then, the SWNTs were grown on the quartz surface via the lattice-oriented growth mode, in which growth of SWNTs can be terminated by hitting the nanotube nanobarriers. Moreover, using the carbon nanotube nanobarrier as a marker, the mechanism of the growth of SWNTs on the quartz surface can be studied; a base-growth mechanism is indicated. Based on this termination process and the base-growth mechanism, SWNT arrays with controlled lengths can be grown on a quartz surface by fixing the sites of both catalysts and nanobarriers. 相似文献
15.
Inna Wiesel Hamutal Arbel Ana Albu-Yaron Ronit Popovitz-Biro Jeffrey M. Gordon Daniel Feuermann Reshef Tenne 《Nano Research》2009,2(5):416-424
Inorganic fullerene-like WS2 and MoS2 nanoparticles have been synthesized using exclusively solid precursors, by reaction of the corresponding metal oxide nanopowder,
sulfur and a hydrogen-releasing agent (NaBH4 or LiAlH4), achieved either by conventional furnace heating up to ∼900 °C or by photothermal ablation at far higher temperatures driven
by highly concentrated white light. In contrast to the established syntheses that require toxic and hazardous gases, working
solely with solid precursors permits relatively safer reactor conditions conducive to industrial scale-up.
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16.
We report synthesis windows for growth of millimeter-long ZnTe nanoribbons and ZnSe nanowires using vapor transport. By tuning
the local conditions at the growth substrate, high aspect ratio nanostructures can be synthesized. A Cu-ion immersion doping
method was applied, producing strongly p-type conduction in ZnTe and ionic conduction in ZnSe. These extreme aspect ratio
wide-bandgap semiconductors have great potential for high density nanostructured optoelectronic circuits.
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17.
Xiaolei Zuo Cheng Peng Qing Huang Shiping Song Lihua Wang Di Li Chunhai Fan 《Nano Research》2009,2(8):617-623
We report a novel nanotechnology-based approach for the highly efficient catalytic oxidation of phenols and their removal
from wastewater. We use a nanocomplex made of multi-walled carbon nanotubes (MWNTs) and magnetic nanoparticles (MNPs). This
nanocomplex retains the magnetic properties of individual MNPs and can be effectively separated under an external magnetic
field. More importantly, the formation of the nanocomplex enhances the intrinsic peroxidase-like activity of the MNPs that
can catalyze the reduction of hydrogen peroxide (H2O2). Significantly, in the presence of H2O2, this nanocomplex catalyzes the oxidation of phenols with high efficiency, generating insoluble polyaromatic products that
can be readily separated from water.
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18.
Wenjie Liang Oded Rabin Allon I. Hochbaum Melissa Fardy Minjuan Zhang Peidong Yang 《Nano Research》2009,2(5):394-399
The thermoelectric properties of individual solution-phase synthesized p-type PbSe nanowires have been examined. The nanowires
showed near degenerately doped charge carrier concentrations. Compared to the bulk, the PbSe nanowires exhibited a similar
Seebeck coefficient and a significant reduction in thermal conductivity in the temperature range 20 K to 300 K. Thermal annealing
of the PbSe nanowires allowed their thermoelectric properties to be controllably tuned by increasing their carrier concentration
or hole mobility. After optimal annealing, single PbSe nanowires exhibited a thermoelectric figure of merit (ZT) of 0.12 at
room temperature.
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19.
We revisit the mechanism leading to the photoresponse of locally illuminated single-walled carbon nanotube (SWNT) films deposited
on substrates. Our study examines the impact of multiple device parameters and provides many evidences that the position-dependent
photocurrent is dominated by photothermoelectric effects. The photoresponse arises from the temperature variations at the
metal-nanotube film interfaces, where mismatches of the Seebeck coefficients are measured. Our work also stresses the impact
of the substrates, electrode materials and post-thermal treatments on the amplitude and dynamics of the photoresponse. The
knowledge gained should guide the future development of photothermoelectric devices and detectors based on SWNTs.
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20.
Chemistry gives us the ability to manipulate atoms and molecules into nanometer and micrometer scale building blocks, while
the science of crystallography is concerned with the spatial arrangement of atoms, ions, and molecules and thus the morphology
and structures of materials. Complex three-dimensional ZnS nanostructures have been fabricated via step-by-step crystallographically-controlled
chemical processes. Tricrystals of ZnS whiskers were prepared via a controlled thermal evaporation process, and then the tricrystals
were thermally treated in an atmosphere formed by evaporating B-N-O precursors into N2/NH3 to afford BN-coated arrays of nanobranches. The ZnS nanobranches grew epitaxially on the ternary facets and extended in three
[0001] directions forming ordered nanostructures. Meanwhile, the protecting insulating sheath of BN formed on the ZnS nanostructures
confined the growth of the nanospines and enhanced their stability. The method may be extended to fabricate other semiconductor
nanomaterials with novel structures.
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