共查询到20条相似文献,搜索用时 301 毫秒
1.
In this paper we present some simulation results about the behaviour
of water molecules inside a single wall carbon nanotube (SWNT). We
find that the confinement of water in an SWNT can induce a wave-like
pattern distribution along the channel axis, similar phenomena are
also observed in biological water channels. Carbon nanotubes(CNTs)
can serve as simple nonpolar water channels. Molecular transport
through narrow CNTs is highly collective because of tight hydrogen
bonds in the protective environment of the pore. The hydrogen bond
net is important for proton and other signal transports. The average
dipoles of water molecules inside CNTs (7,7), (8,8) and (9,9) are
discussed in detail. Simulation results indicate that the states of
dipole are affected by the diameter of SWNT. The number of hydrogen
bonds, the water--water interaction and water--CNT interaction are
also studied in this paper. 相似文献
2.
3.
用巨正则蒙特卡罗分子模拟方法研究了单壁纳米碳管中的微孔即单壁纳米碳管基本孔-内管腔和管间孔对单壁纳米碳管储氢性能的影响.与低温下氮气吸附实验结果的比较发现单壁纳米碳管的内管腔是吸附的主要位置.分析单壁纳米碳管内管腔中吸附势的叠加和利用效率,发现管径为2nm左右时单壁纳米碳管内管腔的储氢容量最高.当单壁纳米碳管阵列的管间距增加时,单壁纳米碳管的管间孔也会成为有效的氢吸附位.
关键词:
Monte Carlo方法
单壁纳米碳管
储氢
微孔 相似文献
4.
Well-defined fibers and films of single-walled carbon nanotubes (SWNTs) with high purity and narrow diameter distributions were obtained from the strand-like raw soot produced by a dc arc-discharge method. These architectures made up of SWNTs have very uniform smooth surfaces. When the strand-like product was placed on a silicon substrate, dipped into water, treated ultrasonically, and then dried in air, another interesting architecture, an SWNT ball, was obtained. This ball-like structure could also be found on the surface of purified SWNTs. We propose that the surface tension of water and the interaction between SWNTs and silica sphere played the key role in the ball (SWNTs outside and silica sphere inside) formation process. 相似文献
5.
In this work, the influence factors, namely chirality, temperature, radius and surface chemical modification, of the interaction energy for polyethylene (PE) molecule encapsulated into single-walled carbon nanotubes (SWNTs) had been investigated by molecular mechanics (MM) and molecular dynamics (MD) simulation. The results showed that all these factors would influence the interaction energy between PE and SWNTs. The interaction energy between PE molecule and the armchair SWNTs is largest among eight kinds of chiral SWNTs. The interaction energy decreases with the increase of temperature or the SWNT radius. The methyl, phenyl, hydroxyl, carboxyl, -F, and amino groups, have been introduced onto the surface of the SWNTs by the simulation software and the influence of SWNT chemical modification has also been investigated. The interaction energy between PE and chemically modified SWNTs is larger than that between PE and pristine SWNTs, and increases with increasing the concentration of the modified groups monotonously. In addition, the group electronegativity and van der Waals force will affect the interaction energy between PE and chemically modified SWNTs greatly, which can be attributed to the electronic structures of the chemically modified groups. This study can provide some useful suggestions for the composite material design and drug transport. 相似文献
6.
X.P. Yang H.M. Weng J. Dong 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):345-350
The structural, electronic, and optical properties of 4 ? single-walled carbon nanotubes (SWNTs) contained inside the zeolite
channels have been studied based upon the density-functional theory in the local-density approximation (LDA). Our calculated
results indicate that the relaxed geometrical structures for the smallest SWNTs in the zeolite channels are much different
from those of the ideal isolated SWNTs, producing a great effect on their physical properties. It is found that all three
kinds of 4 ? SWNTs can possibly exist inside the Zeolite channels. Especially, as an example, we have also studied the coupling
effect between the ALPO4-5 zeolite and the tube (5,0) inside it, and found that the zeolite has real effects on the electronic structure and optical
properties of the inside (5,0) tube.
Received 26 January 2003 Published online 11 April 2003
RID="a"
ID="a"e-mail: yxptl@hotmail.com 相似文献
7.
Single-walled carbon nanotubes (SWNTs) have been grown on silicon nanowires (SiNWs) by ethanol chemical vapor deposition (CVD) with Co catalysts. We have found that a surface SiOx layer of SiNWs is necessary for the formation of active Co catalysts. In fact, the yield of the SWNT/SiNW heterojunctions gradually decreases as the thickness of the surface SiOx layer decreases. Since thin SiNWs are transparent to an electron beam, the Co nanoparticles on SiNWs can be easily observed as well as SWNTs by TEM. Therefore, the relationship between the diameters of each SWNT and its catalyst nanoparticle has been investigated. The diameters of SWNTs are equal to or slightly smaller than those of the catalyst nanoparticles. 相似文献
8.
S.H. Jhang S.W. Lee D.S. Lee H.Y. Yu U. Dettlaff E.E.B. Campbell S. Roth Y.W. Park 《Current Applied Physics》2006,6(6):987
The switching of resistance between two discrete values, known as random telegraph noise (RTN), was observed in individual single-walled carbon nanotubes (SWNTs) and C60-filled SWNTs (the so-called peapods). The RTN has been studied as a function of bias-voltage and gate-voltage as well as temperature. By analyzing the features of the RTN, we identify three different types of RTN existing in the SWNT related systems. While the RTN can be generated by the various charge traps in the vicinity of the SWNTs, the RTN for metallic SWNTs is mainly due to reversible defect motions between two metastable states, activated by inelastic scattering with ballistic electrons. On the other hand, the noise for peapods can be attributed to the motion of C60 molecules in hollow space of SWNTs. 相似文献
9.
《中国物理 B》2015,(7)
A novel nanoscale watermill for the unidirectional transport of water molecules through a curved single-walled carbon nanotube(SWNT) is proposed and explored by molecular dynamics simulations. In this nanoscale system, a revolving charge is introduced to drive a water chain confined inside the SWNT, the charge and the tube together serving as a nano waterwheel and nano engine. A resonance-like phenomenon is found, and the revolving frequency of the charge plays a key role in pumping the water chain. The water flux across the SWNT increases with respect to the revolving frequency of the external charge and it reaches its maximum when the frequency is 4 THz. Correspondingly, the number of hydrogen bonds in the water chain inside the SWNT decreases dramatically as the frequency increases from 4 THz to 25 THz. The mechanism behind the resonance phenomenon has been investigated systematically. Our findings are helpful for the design of nanoscale fluidic devices and energy converters. 相似文献
10.
Single-walled carbon nanotubes (SWNTs)/polyaniline (PANI) composite films with good uniformity and dispersion were prepared by electrochemical polymerization of aniline containing well-dissolved SWNTs. The composite films were dispersed Pt by electrodeposition technique. The presence of SWNTs and platinum in the composite film was confirmed by XRD analysis and scanning electron microscopy (SEM). Four-point probe investigation and electrochemical impedance spectroscopy (EIS) revealed that the well arrangement of PANI coated SWNTs in these films enhanced electric conductivity and facilitated the charge-transfer of the composite films. Cyclic voltammogram (CV) and chronoamperogram showed that Pt-modified SWNT/PANI composite film performs higher electrocatalytic activity and better long-term stability than Pt-modified pure PANI film toward formaldehyde oxidation. The results imply that the SWNT/PANI composite film as a promising support material improves the electrocatalytic activity for formaldehyde oxidation greatly. 相似文献
11.
采用可以控制真空室温度的改进型直流电弧炉,在氮气和氦气(1∶1)混合气氛下,使用Co-Ni(1∶1wt%)合金催化剂,通过控制温度等工艺条件,在容器内壁生成了大量单壁碳纳米管,尤其在阴极与阳极之间有大量的宏观网状薄膜.通过两步纯化方法:在500℃空气中烘烧30min;再用37%盐酸浸泡72h,用去离子水过滤至中性烘干.经SEM,HRTEM,XRD,Raman观察分析,纯化后其纯度高(>95%)、管径均匀(1.24—1.38nm).实验结果表明:温度强烈影响单壁碳纳米管的产量,不同温度下管子的纯度、产量都有差异,在温度为600℃时,其纯度达到70%,产量为12g/h.
关键词:
单壁碳纳米管
电弧法
温度影响 相似文献
12.
Selection of isolated and individual single-walled carbon nanotube from a film and its usage in nanodevices 下载免费PDF全文
Individual and isolated single-walled carbon nanotubes (SWNTs) are important for fabricating relevant nanode- vices and studying the properties of the SWNT devices. In this work, we demonstrate that individual and isolated SWNT can be selected and obtained from a film containing a huge number of SWNTs. By using both the polymethyl-methacrylate (PMMA) as a negative resist and the electron beam lithography, the selected SWNT can be fixed on a substrate, while the other SWNTs in the film can lift off. The selected SWNT can be used to fabricate nanodevice and a gas sensor of oxygen is demonstrated in this work. 相似文献
13.
The image contrast enhancement in scanning electron microscopy of single-walled carbon nanotubes (SWNTs) on SiO2 surfaces was experimentally investigated using a field-emission scanning electron microscope (FESEM) using a wide range of primary electron (PE) voltages. SWNT images of different contrasts were obtained at different PE voltages. Image contrast enhancement of SWNTs was investigated by charging SiO2 surfaces at different PE voltages. The phenomena are ascribed to the surface potential difference and charge injection between SWNTs and SiO2 substrates induced by the electron-beam irradiation. 相似文献
14.
Hydrophilic surface of carbon nanotubes (CNTs) are of great interest for various applications including chemical and biological sensing. Surface functionalization of single wall carbon nanotubes (SWNTs) mats with a biocompatible polymer polyvinyl alcohol (PVA) was studied. PVA modification induced a drastic change in water wettability of the SWNT surface transforming it from hydrophobic to highly hydrophilic. These PVA modified SWNTs mats have also demonstrated increasing impedance variation in relative humidity compared to the pristine nanotubes. An appreciable change in conductivity of Y-junction SWNT mats as a function of relative humidity indicates its potential application as humidity sensor. This higher sensitivity for humidity variation shown in Y-junction SWNT mats could be attributed to the greater portion of semiconducting nanotubes in these mats revealed by Raman analysis. A possible conductance changing mechanism of surface modified SWNTs mats is discussed. 相似文献
15.
Optical properties of fullerene and non-fullerene peapods 总被引:1,自引:0,他引:1
H. Kataura Y. Maniwa M. Abe A. Fujiwara T. Kodama K. Kikuchi H. Imahori Y. Misaki S. Suzuki Y. Achiba 《Applied Physics A: Materials Science & Processing》2002,74(3):349-354
Single-wall carbon nanotubes (SWNTs) encapsulating fullerenes, so-called fullerene peapods, were synthesized in high yield
by using diameter-selected nanotubes as pods. Transmission electron microscopy revealed high-density fullerene chains inside
the nanotubes. X-ray-diffraction measurements indicate 85% filling for C60 and 72% filling for C70 molecules as a total yield. Interestingly, C60 peas do not show any thermal expansion while C70 peas show normal behavior. Room-temperature Raman spectra show one-dimensional photopolymerization of C60 inside nanotubes by blue-laser irradiation, suggesting molecular rotation inside them. In C70 peapods, no photopolymerization was observed but the relative Raman intensity of each peak is different from the C70 3D crystal. This is probably caused by mixing of two different crystal structures in C70 peas. Furthermore, we synthesized Zn-diphenylporphyrin peapods. Optical absorption and Raman spectra suggest that the encapsulated
molecules are deformed by interaction with the SWNT.
Received: 12 November 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002 相似文献
16.
Surfactant-nanotube interactions in water and nanotube separation by diameter: atomistic simulations
E. J.F. Carvalho M. C. dos Santos 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,75(2):147-150
A non-destructive sorting method to separate
single-walled carbon nanotubes (SWNTs) by diameter was recently
proposed. By this method, SWNTs are suspended in water by
surfactant encapsulation and the separation is carried out by
ultracentrifugation in a density gradient. SWNTs of different
diameters are distributed according to their densities along the
centrifuge tube. A mixture of two anionic surfactants, namely
sodium dodecylsulfate (SDS) and sodium cholate (SC), presented the
best performance in discriminating nanotubes by diameter.
Unexpectedly, small diameter nanotubes are found at the low
density part of the centrifuge tube. We present molecular dynamics
studies of the water-surfactant-SWNT system to investigate the
role of surfactants in the sorting process. We found that
surfactants can actually be attracted towards the interior of the
nanotube cage, depending on the relationship between the
surfactant radius of gyration and the nanotube diameter. The
dynamics at room temperature showed that, as the amphiphile moves
to the hollow cage, water molecules are dragged together, thereby
promoting the nanotube filling. The resulting densities of filled
SWNT are in agreement with measured densities. 相似文献
17.
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
18.
We have calculated the quantum conductance of single-walled
carbon nanotube (SWNT) waveguide by using a tight binding-based
Greens function approach. Our calculations show that the slow
conductance oscillations as well as the fast conductance
oscillations are manifestations of the intrinsic quantum
interference properties of the conducting SWNTs, being independent
of the defect and disorder of the SWNTs. And zigzag type tubes do
not show the slow oscillations. The SWNT electron waveguide is
also found to have distinctly different transport behavior
depending on whether or not the length of the tube is commensurate
with a (3N+1) rule, with N the number of basic carbon repeat
units along the nanotube length. 相似文献
19.
This paper describes a new method to create nanoscale SiO2 pits or channels using single-walled carbon nanotubes (SWNTs) in an HF solution at room temperature within a few seconds. Using aligned SWNT arrays, a pattern of nanoscale SiO2 channels can be prepared. The nanoscale SiO2 patterns can also be created on the surface of three-dimensional (3D) SiO2 substrate and even the nanoscale trenches can be constructed with arbitrary shapes. A possible mechanism for this enhanced etching of SiO2 has been qualitatively analysed using defects in SWNTs, combined with H3O+ electric double layers around SWNTs in an HF solution. 相似文献
20.
Computational analysis of effect of modification on the interfacial characteristics of a carbon nanotube-polyethylene composite system 总被引:1,自引:0,他引:1
In this study, the non-covalent association of single-walled nanotube (SWNT) with polyethylene (PE) molecule and the influence of sidewall modification on the interfacial bonding between the SWNTs and polymer were investigated using molecular mechanics (MM) and molecular dynamics (MD) simulations. The model of interaction between the initially separated PE and SWNT fragments, which can be either wrapping or filling, was computed. The possible extension of polymers wrapping or filling SWNTs can be used to structurally bridge the SWNTs and polymers to significantly improve the load transfer between them when SWNTs are used to produce nanocomposites. The interfacial bonding characteristics between the single-walled nanotubes, on which -COOH, -CONH2, -C6H11, or -C6H5 groups have been chemically attached, and the polymer matrix were also investigated by performing pullout simulations. The results show that appropriate functionalization of nanotubes at low densities of functionalized carbon atoms drastically increase their interfacial bonding and shear stress between the nanotubes and the polymer matrix, where chemisorption with -C6H5 groups to as little as 5.0% of the nanotube carbon atoms increases the shear stress by about 1700%. Furthermore, this suggests the possibility to use functionalized nanotubes to effectively reinforce other kinds of polymer-based materials as well. 相似文献