共查询到20条相似文献,搜索用时 15 毫秒
1.
We demonstrate that zinc oxide can catalyze the growth of single-walled carbon nanotubes (SWNTs) with high efficiency by a chemical vapor deposition process. The zinc oxide nanocatalysts, prepared using a diblock copolymer templating method and characterized by atomic force microscopy (AFM), were uniformly spaced over a large deposition area with an average diameter of 1.7 nm and narrow size distribution. Dense and uniform SWNTs films with high quality were obtained by using a zinc oxide catalyst, as characterized by scanning electron microscopy (SEM), Raman spectroscopy, AFM, and high-resolution transmission electron microscopy (HRTEM). 相似文献
2.
Suspended single-walled carbon nanotubes (SWCNTs) between SiO2 pillars via a direct lithographic route using a simple mixture of catalyst precursor [Co(III) acetylacetonate, Co(acac)3] and conventional electron beam resist (ma-N2403) were fabricated. The catalytic electron beam resist (Cat-ER) layer plays dual roles as a catalyst and a resist layer for the growth and alignment of CNTs, respectively. The structure of the grown nanotube was characterized by Raman spectroscopy (633 nm laser excitation). Nanotubes grown from Cat-ER with Co(acac)3 show the typical Raman spectra of SWCNTs which are characterized by the strong tangential bands near to 1590 cm−1 and radial breathing modes (RBMs) in the low frequency region (<300 cm−1). The calculated diameter of the probed nanotubes individually corresponds to the range 0.86-1.77 nm. 相似文献
3.
Electric field aligned, single-walled carbon nanotubes are grown between electrodes using thermal chemical vapour deposition (CVD) of methane. The growth occurs on a thin film layered catalyst of aluminium, iron and molybdenum patterned on top of electrodes. The nanotubes bridge 10 μm sized electrode gaps and have a typical diameter of less than 2 nm as measured by Raman spectroscopy and atomic force microscopy. We present electrical transport measurements on a directly grown nanotube which shows p-type semiconducting behaviour. 相似文献
4.
Growth of single-walled carbon nanotubes from size-selected catalytic metal particles 总被引:1,自引:0,他引:1
M. Kohno T. Orii M. Hirasawa T. Seto Y. Murakami S. Chiashi Y. Miyauchi S. Maruyama 《Applied Physics A: Materials Science & Processing》2004,79(4-6):787-790
Single-walled carbon nanotubes (SWNTs) were synthesized using size-controlled catalyst nanoparticles created by the pulsed laser ablation method. Specifically, the alloy particles (Co/Mo or Co/Pt) were prepared by ablation of the target alloy materials in an inert gas atmosphere. Size selection was performed using a differential mobility analyzer (DMA). The obtained nanoparticles were deposited on a quartz substrate from which SWNTs were grown by the alcohol catalytic CVD (ACCVD) technique that was developed by the authors group. AFM and Raman scattering analysis revealed that SWNTs were successfully synthesized. It seems the Co/Mo alloy catalyst was more effective for the synthesis of SWNTs than the Co/Pt catalyst, though this is a preliminary result to be further investigated. PACS 36.40.-c; 61.46.+w; 65.80.+n; 78.30.Na; 81.07.de 相似文献
5.
K. Bladh L.K.L. Falk F. Rohmund 《Applied Physics A: Materials Science & Processing》2000,70(3):317-322
The production of single-walled carbon nanotubes (SWNT) by catalytic disproportionation of carbon monoxide on iron particles in the gas phase was studied. The addition of hydrogen to the reactants was found to increase the SWNT yield relative to the competing formation of encapsulated iron particles. Adding acetylene, however, did not result in a significant change of the SWNT growth but gave rise to the formation of unwanted self-pyrolysis products. Iron particles are seen to decorate the SWNT and are shown to be single crystalline with several layers of encapsulation by graphitic carbon. All these observations are discussed with respect to the catalytic growth mechanism of SWNT and encapsulated metal particles from CO and hydrocarbon molecules. 相似文献
6.
In this paper, we report that ruthenium is an active and efficient catalyst for growth of single-walled carbon nanotubes (SWNTs) by a chemical vapor deposition (CVD) process for the first time. High density random and horizontally superlong well-oriented SWNTs on substrate can be fabricated via CH4 or EtOH as carbon source under suitable conditions. Scanning and transition electron microscopy investigations, Raman spectroscopy and atomic force microscopy measurements show the tubular structure, the high crystallinity, and the properties of the grown nanotubes. The results show that the SWNTs from ruthenium have better structural uniformity with less defects and provides an alternative catalyst for SWNTs growth. The successful growth of SWNTs by Ru catalyst provides new experimental information for understanding the growth mechanism of SWNTs, which may be helpful for their controllable synthesis. 相似文献
7.
Y. Zhang Y. Li W. Kim D. Wang H. Dai 《Applied Physics A: Materials Science & Processing》2002,74(3):325-328
Discrete catalytic nanoparticles with diameters in the range of 1–3 nm are obtained by placing controllable numbers of metal
atoms into the cores of apoferritin. With nanoparticles placed on transmission electron microscope (TEM) grids coated with
ultra-thin alumina membranes, isolated single-walled carbon nanotubes are grown by chemical vapor deposition and directly
examined by TEM. The characterizations, carried out at single-tube and single-particle level, obtain clear evidence that the
diameters of the nanotubes are determined by the diameters of catalytic nanoparticles. For the first time, both ends of an
as-grown single-walled nanotube are imaged by TEM, leading to a microscopic picture of the nanotube-growth mechanism.
Received: 19 September 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002 相似文献
8.
Terrones M Banhart F Grobert N Charlier JC Terrones H Ajayan PM 《Physical review letters》2002,89(7):075505
Crossing single-walled carbon nanotubes can be joined by electron beam welding to form molecular junctions. Stable junctions of various geometries are created in situ in a transmission electron microscope. Electron beam exposure at high temperatures induces structural defects which promote the joining of tubes via cross-linking of dangling bonds. The observations are supported by molecular dynamics simulations which show that the creation of vacancies and interstitials induces the formation of junctions involving seven- or eight-membered carbon rings at the surface between the tubes. 相似文献
9.
In a system of N interacting single-level quantum dots (QDs), we study the relaxation dynamics and the current–voltage characteristics determined by symmetry properties of the QD arrangement. Different numbers of dots, initial charge configurations, and various coupling regimes to reservoirs are considered. We reveal that effective charge trapping occurs for particular regimes of coupling to the reservoir when more than two dots form a ring structure with the CN spatial symmetry. We reveal that the effective charge trapping caused by the CN spatial symmetry of N coupled QDs depends on the number of dots and the way of coupling to the reservoirs. We demonstrate that the charge trapping effect is directly connected with the formation of dark states, which are not coupled to reservoirs due to the system spatial symmetry CN. We also reveal the symmetry blockade of the tunneling current caused by the presence of dark states. 相似文献
10.
Nikitin A Ogasawara H Mann D Denecke R Zhang Z Dai H Cho K Nilsson A 《Physical review letters》2005,95(22):225507
Towards the development of a useful mechanism for hydrogen storage, we have studied the hydrogenation of single-walled carbon nanotubes with atomic hydrogen using core-level photoelectron spectroscopy and x-ray absorption spectroscopy. We find that atomic hydrogen creates C-H bonds with the carbon atoms in the nanotube walls, and such C-H bonds can be completely broken by heating to 600 degrees C. We demonstrate approximately 65 +/- 15 at % hydrogenation of carbon atoms in the single-walled carbon nanotubes, which is equivalent to 5.1 +/- 1.2 wt % hydrogen capacity. We also show that the hydrogenation is a reversible process. 相似文献
11.
Fan X Buczko R Puretzky AA Geohegan DB Howe JY Pantelides ST Pennycook SJ 《Physical review letters》2003,90(14):145501
The nucleation pathway for single-wall carbon nanotubes on a metal surface is demonstrated by a series of total energy calculations using density functional theory. Incorporation of pentagons at an early stage of nucleation is energetically favorable as they reduce the number of dangling bonds and facilitate curvature of the structure and bonding to the metal. In the presence of the metal surface, nucleation of a closed cap or a capped single-wall carbon nanotube is overwhelmingly favored compared to any structure with dangling bonds or to a fullerene. 相似文献
12.
Yanli Zhao Toshiki Sugai Yahachi Saito 《Journal of Physics and Chemistry of Solids》2007,68(2):284-289
Single-walled carbon nanotubes (SWNTs) were prepared with ethanol chemical vapor deposition (CVD) on SiO2 flat and pillar-patterned Si substrates. The effect of CVD temperatures from 600 to 800 °C on SWNTs yields was investigated. By virtue of its unperturbed environment, an individual suspended SWNT grown between two different SiO2 pillars provides a possibility to study the phonon band structure of SWNT itself at a single-nanotube level. Raman spectra of individual SWNTs grown between pillars were investigated systematically. 相似文献
13.
Ester-functionalized soluble single-walled carbon nanotubes 总被引:2,自引:0,他引:2
M.A. Hamon H. Hui P. Bhowmik H.M.E. Itkis R.C. Haddon 《Applied Physics A: Materials Science & Processing》2002,74(3):333-338
We report the preparation of soluble ester- functionalized single-wall carbon nanotubes (sSWNT-COO(CH2)17CH3). By use of solution phase IR spectroscopy we are able to compare the ratio of the carbon atoms in the SWNT backbone to the
carbon atoms in the ester and amide functionalities of s-SWNTs.
Received: 16 July 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002 相似文献
14.
Xianbao Wang Alexander Volodin Chris Van Haesendonck Nicolas Moreau Antonio Fonseca Janos B. Nagy 《Physica E: Low-dimensional Systems and Nanostructures》2005,25(4):597-604
We report on the controllable growth of individual, uniform carbon nanotubes using thermal chemical vapor deposition (CVD). We performed a detailed study of the various factors influencing the growth of single nanotubes. In particular, we investigated the role played by catalyst layer thickness, catalyst dot size, deposition temperature, and gas source pressure on the growth process of straight, single nanotubes. Straight, individual nanotubes with uniform diameter can be obtained by decomposition of 0.1 mbar of acetylene at a temperature of 800 °C over a 5 nm thick nickel film that is patterned into square dots with dimensions below 500 nm. We compare the performance of thermal CVD and of plasma enhanced CVD for growing individual nanotubes. 相似文献
15.
J. Gao M. A. Loi 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,75(2):121-126
Single-walled carbon nanotubes (SWNTs) are successfully dispersed in two conjugated polymer poly(9,9-dioctylfluorenyl-2,7-diyl)
(PFO) and poly[2-methoxy-5- (2’-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEHPPV) solutions. Steady-state and time-resolved
photoluminescence spectroscopy in the near-infrared and visible spectral regions are used to study the interaction of the
dispersed carbon nanotube and the wrapped polymer in the
nano-hybrids. The SWNTs infrared emission is the signatures of the separation of single semiconducting tubes, the lifetime
of the photoluminescence of these tubes is bi-exponential with the first component varying from 6 ps (in MEHPPV wrapped SWNTs)
to 14 ps (in PFO wrapped SWNTs), while the second component of the decay for all samples is in the range of 30-40 ps, revealing
the intrinsic lifetime of the SWNTs. The study of the photoluminescence of the nano-hybrids in the visible spectral range
shows, in the case of the PFO, a relatively strong quenching, the photoluminescence lifetime for the hybrid is more than 100 ps
shorter than the one of the pristine polyfluorene solution. For the MEHPPV-SWNT hybrid an opposite behavior is revealed with
the photoluminescence lifetime surprisingly longer than the polymer solution. The possible mechanism for the interaction of
the two conjugated polymers and the SWNTs is discussed in terms of their electronic band structure. 相似文献
16.
Blazej Scheibe Ewa Borowiak-Palen Ryszard J. Kalenczuk 《Journal of nanoparticle research》2011,13(11):5769-5780
This study presents the approach to the purification and subsequent metallic/semiconductive (M/S) fractionation of single-walled
carbon nanotubes (SWCNTs) with diameter from 1.04 to 1.60 nm produced via laser ablation. SWCNTs were purified through 3-fold
refluxing processes in nitric acid followed by the multiple washings with sodium hydroxide and hydrochloric acid. The purified-annealed
SWCNTs sample was divided into seven batches. One batch was dispersed in acetone as a reference sample. Each of the remaining
batches were dispersed in one of the following surface agents: sodium dodecyl sulfate, sodium cholate acid (SCA), sodium deoxycholate,
cetrimonium bromide, cetylpyridinium chloride, and benzalkonium chloride (BKC). SWCNT suspensions were fractionated via free
solution electrophoresis technique. The recovered fractions from electrode and control areas were analyzed via optical absorption
spectroscopy in UV–Vis–NIR range to evaluate the efficiency of the separation process. Raman spectroscopy was applied to analyze
the purity of the samples. The catalyst content was estimated by atomic absorption spectroscopy. The morphology of the investigated
samples was observed via high-resolution transmission electron microscopy. This contribution clearly shows that among the
investigated surfactants there are two promising candidates (SCA and BKC) which can efficiently enrich the bulk sample in
one electronic type of carbon nanotubes when FSE is applied. 相似文献
17.
Single-walled carbon nanotubes (SWCNTs) and few-walled carbon nanotubes (FWCNTs) have been selectively synthesized by plasma enhanced chemical vapor deposition at a relative low temperature (550 °C) by tuning the thickness of iron catalyst. The parametric study and the optimization of the nanotube growth were undertaken by varying inductive power, temperature, catalyst thickness, and plasma to substrate distance. When an iron film of 3-5 nm represented the catalyst thickness for growing FWCNT arrays, SWCNTs were synthesized by decreasing the catalyst thickness to 1 nm. The nanotubes were characterized by field emission scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. Electron field emission properties of the nanotubes indicate that the SWCNTs exhibit lower turn-on field compared to the FWCNTs, implying better field emission performance. 相似文献
18.
E. A. Obraztsova E. P. Lukashev A. P. Zarubina I. M. Parkhomenko I. V. Yaminsky 《Moscow University Physics Bulletin》2009,64(3):320-323
The action of single-walled carbon nanotubes (SWCNTs) on cells of the genetically engineered K12 TG1 strain of Escherichia coli, which have a luminescent phenotype generated by the cloning of the lux operon of the native luminescent marine bacterium Photobacterium leiognathi into the strain, is studied in this work. The survival rate of the bacterial cells and their morphological changes are studied by means of atomic force microscopy as a function of their exposure to SWCNTs. 相似文献
19.
20.
Flame synthesis of single-walled carbon nanotubes 总被引:1,自引:0,他引:1
Murray J. Height Jack B. Howard Jefferson W. Tester 《Proceedings of the Combustion Institute》2005,30(2):2537-2543
Flames offer potential for synthesis of carbon nanotubes in large quantities at considerably lower costs than that of other methods currently available. This study aims to examine conditions for carbon nanotube formation in premixed flames and to characterize the morphology of solid carbon deposits and their primary formation mechanisms in the combustion environment. Single-walled nanotubes have been observed in the post-flame region of a premixed acetylene/oxygen/15 mol% argon flame operated at 6.7 kPa with Fe(CO)5 vapor used as a source of metallic catalyst necessary for nanotube growth. Thermophoretic sampling and transmission electron microscopy were used to characterize the solid material present in the flame at various heights above burner (HAB), giving a resolution of formation dynamics within the flame system. Catalyst particle formation and growth is observed to dominate the immediate post-flame region (10–40 mm HAB). Nanotubes were observed to be present after 40 mm HAB with nanotube inception occurring as early as 30 mm HAB. Between 40 and 70 mm HAB, nanotubes are observed to coalesce into clusters. A nanotube formation ‘window’ is evident with formation limited to fuel equivalence ratios between 1.5 and 1.9. A continuum of morphologies ranging from relatively clean clusters of nanotubes to amorphous material is observed between these lower and upper limits. High-resolution TEM and Raman spectroscopy revealed nanotube bundles with each nanotube being single-walled with diameters between 0.9 and 1.5 nm. 相似文献