In this study,the performances of fixed and fluidized bed reactors in the production of single-walled carbon nanotubes(SWNTs)have been investigated.In both reactors,single-walled carbon nanotubes were grown by catal...In this study,the performances of fixed and fluidized bed reactors in the production of single-walled carbon nanotubes(SWNTs)have been investigated.In both reactors,single-walled carbon nanotubes were grown by catalytic chemical vapor decomposition(CCVD)of methane over Co-Mo/MgO nanocatalyst under two different operating conditions.The synthesized samples were characterized by TEM,TGA and Raman spectroscopy.It is found that the performance of a fluidized bed in the synthesis of carbon nanotubes is much better than that of a fixed bed.The quality of carbon nanotubes obtained from the fluidized bed was significantly higher than that from the fixed bed and the former one with the ID/IG ratio of 0.11 while the latter one with the ID/IG ratio of 0.71.Also,the yield of SWNTs in the fluidized bed was 92 wt%,while it was 78 wt%in the fixed bed.These advantages of fluidized bed reactors for the synthesis of carbon nanotubes can be attributed to more available space for the growth of carbon nanotubes and more uniform temperature and concentration profiles.展开更多
The adsorption of hydrogen onto single-walled carbon nanotubes (SWCNTs) was studied by molecular dynamics (MD) sim'lation. It was found that the hydrogen molecules distribute regularly inside and outside of the tu...The adsorption of hydrogen onto single-walled carbon nanotubes (SWCNTs) was studied by molecular dynamics (MD) sim'lation. It was found that the hydrogen molecules distribute regularly inside and outside of the tube. Density distribution was computed for H2 molecule. Theoretical analysis of the result showed the multilayer adsorption mechanism of SWCNTs. The storage of H2 in SWCNTs is computed, which provides essential theoretical reference for further study of hydrogen adsorption in SWCNTs.展开更多
Nitrogen-doped single-walled carbon nanotubes (CNx-SWNTs) with tunable dopant concentrations were synthesized by chemical vapor deposition (CVD), and their structure and elemental composition were characterized by...Nitrogen-doped single-walled carbon nanotubes (CNx-SWNTs) with tunable dopant concentrations were synthesized by chemical vapor deposition (CVD), and their structure and elemental composition were characterized by using transmission electron microscopy (TEM) in combination with electron energy loss spectroscopy (EELS). By comparing the Raman spectra of pristine and doped nanotubes, we observed the doping-induced Raman G band phonon stiffening and 2D band phonon softening, both of which reflect doping-induced renormalization of the electron and phonon energies in the nan- otubes and behave as expected in accord with the n-type doping effect. On the basis of first principles calculations of the distribution of delocalized carrier density in both the pristine and doped nanotubes, we show how the n-type doping occurs when nitrogen heteroatoms are substitutionally incorporated into the honeycomb tube-shell carbon lattice.展开更多
A new chromatographic purification of single-walled carbon nanotubes using high-speed countercurrent chromatography is reported. The purification was accomplished on the basis of experiment that dispersed the single-w...A new chromatographic purification of single-walled carbon nanotubes using high-speed countercurrent chromatography is reported. The purification was accomplished on the basis of experiment that dispersed the single-walled carbon nanotubes with sodium dodecyl sulfate, and the result mixture was separated using the two phase system composed of n-butanol/water = 1/1 (v/v). The sizes of SWNTs separated were observed by scanning electron microscopy. The results demonstrated that the high-speed countercurrent chromatography possessed a good efficency for purification of single-walled carbon nanotubes.展开更多
The binding energies, geometric structures and electronic properties of molybde- num trioxide (MOO3) molecule encapsulated inside (8, 0), (9, 0), (10, 0) and (14, 0) single-walled carbon nanotubes (SWNTs) ...The binding energies, geometric structures and electronic properties of molybde- num trioxide (MOO3) molecule encapsulated inside (8, 0), (9, 0), (10, 0) and (14, 0) single-walled carbon nanotubes (SWNTs) have been investigated using density functional theory (DFT) method. Due to curvature effect, the calculated binding energy values are different, the variation of which indicated that the stability of MoO3/SWNT systems increases with increasing the radius of SWNTs. At the same time, owing to the presence of MoO3 molecule, the band gap of MoO3/SWNTs systems decreases. The analysis of density of states (DOS) reveals hybridization between C-2p and Mo-4d and between C-2p and O-2p orbitals near the Fermi level, which results in electron transfer from SWNTs to MoO3 molecule. The present computations suggest that electronic properties of SWNTs can be modified by doping MoO3 molecule.展开更多
In this study, a model for dynamic instability of embedded single-walled car- bon nanotubes (SWCNTs) is presented. SWCNTs are modeled by the sinusoidal shear deformation beam theory (SSDBT). The modified couple st...In this study, a model for dynamic instability of embedded single-walled car- bon nanotubes (SWCNTs) is presented. SWCNTs are modeled by the sinusoidal shear deformation beam theory (SSDBT). The modified couple stress theory (MCST) is con- sidered in order to capture the size effects. The surrounding elastic medium is described by a visco-Pasternak foundation model, which accounts for normal, transverse shear, and damping loads. The motion equations are derived based on Hamilton's principle. The differential quadrature method (DQM) in conjunction with the Bolotin method is used in order to calculate the dynamic instability region (DIR) of SWCNTs. The effects of differ- ent parameters, such as nonlocal parameter, visco-Pasternak foundation, mode numbers, and geometrical parameters, are shown on the dynamic instability of SWCNTs. The re- sults depict that increasing the nonlocal parameter shifts the DIR to right. The results presented in this paper would be helpful in design and manufacturing of nano-electromechanical system (NEMS) and micro-electro-mechanical system (MEMS).展开更多
The analytical expression of the electronic density of states (DOS) for single-walled carbon nanotubes (SWNTs) has been derived on the basis of graphene approximation of the energy E(k) near the Fermi level EF. The di...The analytical expression of the electronic density of states (DOS) for single-walled carbon nanotubes (SWNTs) has been derived on the basis of graphene approximation of the energy E(k) near the Fermi level EF. The distinctive properties of the DOS, the normalized differential conductivity and the current us bias for SWNTs are deduced and analyzed theoretically. The singularities in the DOS (or in the normalized differential conductivity) predict that the jump structure of current (or conductance)-bias of SWNTs exists. All conclusions from the theoretical analysis are in well agreement with the experimental results of SWNT's electronic structure and electronic transport. In other words, the simple theoretical model in this paper can be applied to understand a range of spectroscopic and other measurement data related to the DOS of SWNTs.展开更多
An all-fiber laser using a single-walled carbon nanotube(SWCNT) as the saturable absorber(SA) for Q-switched operation in the 1031 nm region is demonstrated in this work. A lasing threshold as low as 17 mW was rea...An all-fiber laser using a single-walled carbon nanotube(SWCNT) as the saturable absorber(SA) for Q-switched operation in the 1031 nm region is demonstrated in this work. A lasing threshold as low as 17 mW was realized for continuous wave operation. By further increasing the pump power, stable Q-switched pulse trains are obtained when the pump power ranges from 38 mW to 125 mW, corresponding to repetition rate varying from 40.84 kHz to 66.24 kHz, the pulse width from 2.0 μs to 1.0 μs,and the highest single pulse energy of 40.6 nJ respectively.展开更多
Organics of the phthalocyanine category have very good nonlinear optical properties. The single-walled carbon nanotubes were modified by using the phenoxy phthalocyanine. Characterization analysis was made by means of...Organics of the phthalocyanine category have very good nonlinear optical properties. The single-walled carbon nanotubes were modified by using the phenoxy phthalocyanine. Characterization analysis was made by means of the transmission electron microscope (TEM), ultraviolet visible absorptive spectra, fluorescent spectra and Raman spectra. Under the TEM, it was observed that the composite looked like sugarcoated haws. By comparing the ultraviolet visible absorptive spectra before and after absorption, it was disclosed that the spectral intensity and the intensity of the peaks in the fluorescent spectra dropped remarkably. This shows that the single-walled carbon nanotubes have absorbed a large number of phenoxy phthalocyanines. Raman analysis revealed that in the Raman spectra, the position of the main peaks of the single-walled carbon nanotubes after absorption moved in the direction of long waves. The analysis suggests that the movement of the Raman spectra results from the change in the state of the single-walled carbon nanotubes before and after absorption.展开更多
This article reviews the use of electronic quality single-walled carbon nanotubes grown via chemical vapor deposition (CVD) approaches at high temperatures as building blocks for fabricating flexible field-effect de...This article reviews the use of electronic quality single-walled carbon nanotubes grown via chemical vapor deposition (CVD) approaches at high temperatures as building blocks for fabricating flexible field-effect devices, such as thin-film transistors (TFTs) and chemical sensors. Dry transfer printing technique is developed for forming films of CVD nanotubes on low-temperature plastic substrates. Examples of TFTs with the use of nanotubes and thin dielectrics and hydrogen sensors with the use of nanotubes decorated with palladium nanoparticles are discussed in detail to demonstrate the promising potentiality of single-walled carbon nanotubes for building high performance flexible devices, which can find applications where traditional devices on rigid substrates are not suitable.展开更多
In the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), carboxylic group-functionalized single-walled carbon nanotubes (SWNTs) were assembled vertic...In the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), carboxylic group-functionalized single-walled carbon nanotubes (SWNTs) were assembled vertically on the glassy carbon electrode using ethylenediamine as linking agent to fabricate an aligned electrode (SWNTE). The morphological characteristic was studied with atomic force microscope (AFM) and its electrochemical property was investigated using K3[Fe(CN)6] as probe. ssDNA had a sensitive voltammetric response at the SWNTE and the oxidative peak potentials of guanine base and adenine base were 0.608 Vand 0.896 V, respectively. Under the optimal conditions, the DPV peak current of guanine base vs. the concentration of ssDNA was linear in the range of 5.4 μg/L-10.8 mg/L with a detection limit of 1 μg/L (S/N = 3).展开更多
Parametric instabilities induced by the coupling excitation between the high frequency quantum Langmuir waves and the low frequency quantum ion-acoustic waves in single-walled carbon nanotubes are studied with a quant...Parametric instabilities induced by the coupling excitation between the high frequency quantum Langmuir waves and the low frequency quantum ion-acoustic waves in single-walled carbon nanotubes are studied with a quantum Zakharov model. By linearizing the quantum hydrodynamic equations, we get the dispersion relations for the high frequency quantum Langmuir wave and the low frequency quantum ion-acoustic wave. Using two-time scale method, we obtain the quantum Zaharov model in the cylindrical coordinates. Decay instability and four-wave instability are discussed in detail. It is shown that the carbon nanotube's radius, the equilibrium discrete azimuthal quantum number, the perturbed discrete azimuthal quantum number, and the quantum parameter all play a crucial role in the instabilities.展开更多
The excellent mechanical properties of carbon nanotubes make them potential candidates for engineering application. In this paper, the impact and failure behaviors of single-walled carbon nanotubes (SWCNTs) are inve...The excellent mechanical properties of carbon nanotubes make them potential candidates for engineering application. In this paper, the impact and failure behaviors of single-walled carbon nanotubes (SWCNTs) are investigated. The effects of diameter, length, and chirality on their energy absorption characteristics under lateral impact and axial crush are studied. By integrating the principle of molecular structural mechanics (MSM) into finite element method (FEM), the locations and directions of fracture process can be predicted. It is shown that the specific energy absorption (SEA) of SWCNTs is 1-2 order of magnitude higher than that of the ordinary metallic materials and composites in axial impact, indicating that carbon nanotubes are promising energy absorption materials for engineering applications.展开更多
We report instability of the single-walled carbon nanotubes(SWCNT) filled with non-Newtonian Jeffrey fluid.Our objective is to get the influences of relaxation time and retardation time of the Jeffrey fluid on the vib...We report instability of the single-walled carbon nanotubes(SWCNT) filled with non-Newtonian Jeffrey fluid.Our objective is to get the influences of relaxation time and retardation time of the Jeffrey fluid on the vibration frequency and the decaying rate of the amplitude of carbon nanotubes.An elastic Euler-Bernoulli beam model is used to describe vibrations and structural instability of the carbon nanotubes.A new vibration equation of an SWCNT conveying Jeffrey fluid is first derived by employing Euler-Bernoulli beam equation and Cauchy momentum equation taking constitutive relation of Jeffrey fluid into account.The complex vibrating frequencies of the SWCNT are computed by solving a cubic eigenvalue problem based upon differential quadrature method(DQM).It is interesting to find from computational results that retardation time has significant influences on the vibration frequency and the decaying rate of the amplitude.Especially,the vibration frequency decreases and critical velocity increases with the retardation time.That is to say,longer retardation time makes the SWCNT more stable.展开更多
Carbon nanotubes (CNTs) were extensively explored for their beneficial use in nervous system tissue engineering. However, an important concern regarding the use of CNTs is their toxicity during the interaction betwe...Carbon nanotubes (CNTs) were extensively explored for their beneficial use in nervous system tissue engineering. However, an important concern regarding the use of CNTs is their toxicity during the interaction between cells and the nano particles. The rat pheochromocytoma cell line (PC12) was co-cultured with three types of single-walled carbon nanotubes (SWNTs), purified raw SWNTs (C), hydroxyl purified SWNTs (C-OH) and carboxyl purified SWNTs (C-COOH) at 25 μg/mL and 100 μg/ml. The experimental results revealed that SWNTs at the concentration below 100 μg/mL did not affect the cell viability. Notably, powerful antioxidant system in nerous system tissue is able to counteract with the toxicity of CNTs, which is characterized by the prominently enhanced expression of main antioxidant enzymes (catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S-transferase (GST)). Therefore, we believe that CNTs can be good candidates for the fabrication of biomedical scaffolds for the nerve tissue repair.展开更多
The reaction mechanism between CC12 and armchair single-walled carbon nanotubes (ASWCNTs) (3,3) and (4,4) has been studied by semiempirical AM1 and ab initio methods. The activation barriers of CC12 adding to AS...The reaction mechanism between CC12 and armchair single-walled carbon nanotubes (ASWCNTs) (3,3) and (4,4) has been studied by semiempirical AM1 and ab initio methods. The activation barriers of CC12 adding to ASWCNT (3,3) and (4,4) are computed and compared. The lower barrier of CC12 forms cycloaddition isomer on (3,3) maybe because the strain energy of (3,3) is larger than that of (4,4). Our theoretical results are consistent with the experimental results.展开更多
Depositing single-walled carbon nanotubes(SWNTs) with controllable density, pattern and orientation on electrodes presents a challenge in today's research. Here, we report a novel solvent evaporation method to ali...Depositing single-walled carbon nanotubes(SWNTs) with controllable density, pattern and orientation on electrodes presents a challenge in today's research. Here, we report a novel solvent evaporation method to align SWNTs in patterns having nanoscale width and micronscale length. SWNTs suspension has been introduced dropwise onto photoresist resin microchannels; and the capillary force can stretch and align SWNTs into strands with nanoscale width in the microchannels. Then these narrow and long aligned SWNTs patterns were successfully transferred to a pair of gold electrodes with different gaps to fabricate carbon nanotube field-effect transistor(CNTFET). Moreover, the electrical performance of the CNTFET show that the SWNTs strands can bridge different gaps and fabricate good electrical performance CNTFET with ON/OFF ratio around 106. This result suggests a promising and simple strategy for assembling well-aligned SWNTs into CNTFET device with good electrical performance.展开更多
The electromechanical properties of metallic single-walled carbon nanotubes (SWCNTs) in the electric field are demonstrated with a column shell model in this paper. A hemisphere model is introduced to determine the ...The electromechanical properties of metallic single-walled carbon nanotubes (SWCNTs) in the electric field are demonstrated with a column shell model in this paper. A hemisphere model is introduced to determine the charge distribution and the local electric field in SWCNTs. By treating the SWCNT as an elastic column shell, the analytical solutions of the charged SWCNT's axial strain and the radial strain are obtained. SWCNTs with a larger aspect ratio show greater deformation. The greatest radial deformation appears at the end of the tube. The significant axial strain can be induced in CNTs with a large length (around 100 nm) even though the applied electric field is not strong enough. When SWCNTs are fixed at both ends, the radius of SWCNTs becomes small along the axial position.展开更多
The exciton states of semiconducting carbon nanotubes are calculated by a tight-binding model supplemented by Coulomb interactions under the combined effect of uniaxial strain and magnetic field. It is found that the ...The exciton states of semiconducting carbon nanotubes are calculated by a tight-binding model supplemented by Coulomb interactions under the combined effect of uniaxial strain and magnetic field. It is found that the excitation energies and absorption spectra of zigzag tubes(11,0) and(10,0) show opposite trends with the strain under the action of the magnetic field. For the(11,0) tube, the excitation energy decreases with the increasing uniaxial strain, with a splitting appearing in the absorption spectra. For the(10,0) tube, the variation trend firstly increases and then decreases, with a reversal point appearing in the absorption spectra. More interesting,at the reversal point the intensity of optical absorption is the largest because of the degeneracy of the two bands nearest to the Fermi Level, which is expected to be observed in the future experiment. The similar variation trend is also exhibited in the binding energy for the two kinds of semiconducting tubes.展开更多
文摘In this study,the performances of fixed and fluidized bed reactors in the production of single-walled carbon nanotubes(SWNTs)have been investigated.In both reactors,single-walled carbon nanotubes were grown by catalytic chemical vapor decomposition(CCVD)of methane over Co-Mo/MgO nanocatalyst under two different operating conditions.The synthesized samples were characterized by TEM,TGA and Raman spectroscopy.It is found that the performance of a fluidized bed in the synthesis of carbon nanotubes is much better than that of a fixed bed.The quality of carbon nanotubes obtained from the fluidized bed was significantly higher than that from the fixed bed and the former one with the ID/IG ratio of 0.11 while the latter one with the ID/IG ratio of 0.71.Also,the yield of SWNTs in the fluidized bed was 92 wt%,while it was 78 wt%in the fixed bed.These advantages of fluidized bed reactors for the synthesis of carbon nanotubes can be attributed to more available space for the growth of carbon nanotubes and more uniform temperature and concentration profiles.
文摘The adsorption of hydrogen onto single-walled carbon nanotubes (SWCNTs) was studied by molecular dynamics (MD) sim'lation. It was found that the hydrogen molecules distribute regularly inside and outside of the tube. Density distribution was computed for H2 molecule. Theoretical analysis of the result showed the multilayer adsorption mechanism of SWCNTs. The storage of H2 in SWCNTs is computed, which provides essential theoretical reference for further study of hydrogen adsorption in SWCNTs.
基金supported by the National Natural Science Foundation of China(Grant Nos.11004230,51172273,11290161,and 11027402)the National Key Basic Research Program of China(Grant Nos.2012CB933003 and 2013CB932603)the Innovative Project of the Chinese Academy of Sciences(GrantNo.KJCX2-YW-W35)
文摘Nitrogen-doped single-walled carbon nanotubes (CNx-SWNTs) with tunable dopant concentrations were synthesized by chemical vapor deposition (CVD), and their structure and elemental composition were characterized by using transmission electron microscopy (TEM) in combination with electron energy loss spectroscopy (EELS). By comparing the Raman spectra of pristine and doped nanotubes, we observed the doping-induced Raman G band phonon stiffening and 2D band phonon softening, both of which reflect doping-induced renormalization of the electron and phonon energies in the nan- otubes and behave as expected in accord with the n-type doping effect. On the basis of first principles calculations of the distribution of delocalized carrier density in both the pristine and doped nanotubes, we show how the n-type doping occurs when nitrogen heteroatoms are substitutionally incorporated into the honeycomb tube-shell carbon lattice.
基金supported by National Natural Science Foundation (No.20775066)Yunnan Province's Natural Science Foundations of China (Nos.2005E0006Z and 2007B203M).
文摘A new chromatographic purification of single-walled carbon nanotubes using high-speed countercurrent chromatography is reported. The purification was accomplished on the basis of experiment that dispersed the single-walled carbon nanotubes with sodium dodecyl sulfate, and the result mixture was separated using the two phase system composed of n-butanol/water = 1/1 (v/v). The sizes of SWNTs separated were observed by scanning electron microscopy. The results demonstrated that the high-speed countercurrent chromatography possessed a good efficency for purification of single-walled carbon nanotubes.
基金Supported by the National Natural Science Foundation of China(Nos.11074176and10976019,11176020)the Research Fund for the Doctoral Program of Higher Education of China(No.20100181110080)
文摘The binding energies, geometric structures and electronic properties of molybde- num trioxide (MOO3) molecule encapsulated inside (8, 0), (9, 0), (10, 0) and (14, 0) single-walled carbon nanotubes (SWNTs) have been investigated using density functional theory (DFT) method. Due to curvature effect, the calculated binding energy values are different, the variation of which indicated that the stability of MoO3/SWNT systems increases with increasing the radius of SWNTs. At the same time, owing to the presence of MoO3 molecule, the band gap of MoO3/SWNTs systems decreases. The analysis of density of states (DOS) reveals hybridization between C-2p and Mo-4d and between C-2p and O-2p orbitals near the Fermi level, which results in electron transfer from SWNTs to MoO3 molecule. The present computations suggest that electronic properties of SWNTs can be modified by doping MoO3 molecule.
文摘In this study, a model for dynamic instability of embedded single-walled car- bon nanotubes (SWCNTs) is presented. SWCNTs are modeled by the sinusoidal shear deformation beam theory (SSDBT). The modified couple stress theory (MCST) is con- sidered in order to capture the size effects. The surrounding elastic medium is described by a visco-Pasternak foundation model, which accounts for normal, transverse shear, and damping loads. The motion equations are derived based on Hamilton's principle. The differential quadrature method (DQM) in conjunction with the Bolotin method is used in order to calculate the dynamic instability region (DIR) of SWCNTs. The effects of differ- ent parameters, such as nonlocal parameter, visco-Pasternak foundation, mode numbers, and geometrical parameters, are shown on the dynamic instability of SWCNTs. The re- sults depict that increasing the nonlocal parameter shifts the DIR to right. The results presented in this paper would be helpful in design and manufacturing of nano-electromechanical system (NEMS) and micro-electro-mechanical system (MEMS).
基金The work is financially supported by the National Natural Science Foundation of China (No.59972031)and the Scientific Research Fund of Hunan Provincial Education Department (No.01C248). Authors wish to express their sincere appreciation to these sponsors
文摘The analytical expression of the electronic density of states (DOS) for single-walled carbon nanotubes (SWNTs) has been derived on the basis of graphene approximation of the energy E(k) near the Fermi level EF. The distinctive properties of the DOS, the normalized differential conductivity and the current us bias for SWNTs are deduced and analyzed theoretically. The singularities in the DOS (or in the normalized differential conductivity) predict that the jump structure of current (or conductance)-bias of SWNTs exists. All conclusions from the theoretical analysis are in well agreement with the experimental results of SWNT's electronic structure and electronic transport. In other words, the simple theoretical model in this paper can be applied to understand a range of spectroscopic and other measurement data related to the DOS of SWNTs.
基金Project supported by the National Key Scientific Instruments Development Program of China(Grant No.2012YQ120047)
文摘An all-fiber laser using a single-walled carbon nanotube(SWCNT) as the saturable absorber(SA) for Q-switched operation in the 1031 nm region is demonstrated in this work. A lasing threshold as low as 17 mW was realized for continuous wave operation. By further increasing the pump power, stable Q-switched pulse trains are obtained when the pump power ranges from 38 mW to 125 mW, corresponding to repetition rate varying from 40.84 kHz to 66.24 kHz, the pulse width from 2.0 μs to 1.0 μs,and the highest single pulse energy of 40.6 nJ respectively.
文摘Organics of the phthalocyanine category have very good nonlinear optical properties. The single-walled carbon nanotubes were modified by using the phenoxy phthalocyanine. Characterization analysis was made by means of the transmission electron microscope (TEM), ultraviolet visible absorptive spectra, fluorescent spectra and Raman spectra. Under the TEM, it was observed that the composite looked like sugarcoated haws. By comparing the ultraviolet visible absorptive spectra before and after absorption, it was disclosed that the spectral intensity and the intensity of the peaks in the fluorescent spectra dropped remarkably. This shows that the single-walled carbon nanotubes have absorbed a large number of phenoxy phthalocyanines. Raman analysis revealed that in the Raman spectra, the position of the main peaks of the single-walled carbon nanotubes after absorption moved in the direction of long waves. The analysis suggests that the movement of the Raman spectra results from the change in the state of the single-walled carbon nanotubes before and after absorption.
基金UChicago Argonne,LLC,Operator of Argonne National Laboratory("Argonne").Argonne,a U.S.Department of Energy Office of Science laboratory,is operated under Contract No.DE-AC02-06CHl1357.
文摘This article reviews the use of electronic quality single-walled carbon nanotubes grown via chemical vapor deposition (CVD) approaches at high temperatures as building blocks for fabricating flexible field-effect devices, such as thin-film transistors (TFTs) and chemical sensors. Dry transfer printing technique is developed for forming films of CVD nanotubes on low-temperature plastic substrates. Examples of TFTs with the use of nanotubes and thin dielectrics and hydrogen sensors with the use of nanotubes decorated with palladium nanoparticles are discussed in detail to demonstrate the promising potentiality of single-walled carbon nanotubes for building high performance flexible devices, which can find applications where traditional devices on rigid substrates are not suitable.
基金supports from the National Science Foundation of China(No.20635020,No.20375020)Doctoral Foundation of the Ministry of Education of China(No.20060426001).
文摘In the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), carboxylic group-functionalized single-walled carbon nanotubes (SWNTs) were assembled vertically on the glassy carbon electrode using ethylenediamine as linking agent to fabricate an aligned electrode (SWNTE). The morphological characteristic was studied with atomic force microscope (AFM) and its electrochemical property was investigated using K3[Fe(CN)6] as probe. ssDNA had a sensitive voltammetric response at the SWNTE and the oxidative peak potentials of guanine base and adenine base were 0.608 Vand 0.896 V, respectively. Under the optimal conditions, the DPV peak current of guanine base vs. the concentration of ssDNA was linear in the range of 5.4 μg/L-10.8 mg/L with a detection limit of 1 μg/L (S/N = 3).
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11274255 and 10975114)the Natural Science Foundation of Gansu Province of China (Grant No.2011GS04358)the Creation of Science and Technology of Northwest Normal University of China (Grant No.NWNU-KJCXGC-03-48)
文摘Parametric instabilities induced by the coupling excitation between the high frequency quantum Langmuir waves and the low frequency quantum ion-acoustic waves in single-walled carbon nanotubes are studied with a quantum Zakharov model. By linearizing the quantum hydrodynamic equations, we get the dispersion relations for the high frequency quantum Langmuir wave and the low frequency quantum ion-acoustic wave. Using two-time scale method, we obtain the quantum Zaharov model in the cylindrical coordinates. Decay instability and four-wave instability are discussed in detail. It is shown that the carbon nanotube's radius, the equilibrium discrete azimuthal quantum number, the perturbed discrete azimuthal quantum number, and the quantum parameter all play a crucial role in the instabilities.
基金Funded by the National Natural Science Foundation of China(No.50975011)
文摘The excellent mechanical properties of carbon nanotubes make them potential candidates for engineering application. In this paper, the impact and failure behaviors of single-walled carbon nanotubes (SWCNTs) are investigated. The effects of diameter, length, and chirality on their energy absorption characteristics under lateral impact and axial crush are studied. By integrating the principle of molecular structural mechanics (MSM) into finite element method (FEM), the locations and directions of fracture process can be predicted. It is shown that the specific energy absorption (SEA) of SWCNTs is 1-2 order of magnitude higher than that of the ordinary metallic materials and composites in axial impact, indicating that carbon nanotubes are promising energy absorption materials for engineering applications.
基金Project supported by the National Natural Science Foundation of China(Grant No.11772162)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(Grant No.2019BS01004)the Inner Mongolia Grassland Talent,China(Grant No.12000-12102408)。
文摘We report instability of the single-walled carbon nanotubes(SWCNT) filled with non-Newtonian Jeffrey fluid.Our objective is to get the influences of relaxation time and retardation time of the Jeffrey fluid on the vibration frequency and the decaying rate of the amplitude of carbon nanotubes.An elastic Euler-Bernoulli beam model is used to describe vibrations and structural instability of the carbon nanotubes.A new vibration equation of an SWCNT conveying Jeffrey fluid is first derived by employing Euler-Bernoulli beam equation and Cauchy momentum equation taking constitutive relation of Jeffrey fluid into account.The complex vibrating frequencies of the SWCNT are computed by solving a cubic eigenvalue problem based upon differential quadrature method(DQM).It is interesting to find from computational results that retardation time has significant influences on the vibration frequency and the decaying rate of the amplitude.Especially,the vibration frequency decreases and critical velocity increases with the retardation time.That is to say,longer retardation time makes the SWCNT more stable.
基金Funded by the National Natural Science Foundation of China(No.31300791)
文摘Carbon nanotubes (CNTs) were extensively explored for their beneficial use in nervous system tissue engineering. However, an important concern regarding the use of CNTs is their toxicity during the interaction between cells and the nano particles. The rat pheochromocytoma cell line (PC12) was co-cultured with three types of single-walled carbon nanotubes (SWNTs), purified raw SWNTs (C), hydroxyl purified SWNTs (C-OH) and carboxyl purified SWNTs (C-COOH) at 25 μg/mL and 100 μg/ml. The experimental results revealed that SWNTs at the concentration below 100 μg/mL did not affect the cell viability. Notably, powerful antioxidant system in nerous system tissue is able to counteract with the toxicity of CNTs, which is characterized by the prominently enhanced expression of main antioxidant enzymes (catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S-transferase (GST)). Therefore, we believe that CNTs can be good candidates for the fabrication of biomedical scaffolds for the nerve tissue repair.
基金This work was supported by the National Natural Science Foundation of China (No. 20303010), NKStar HPC Program and the Science Foundation of Nankai University
文摘The reaction mechanism between CC12 and armchair single-walled carbon nanotubes (ASWCNTs) (3,3) and (4,4) has been studied by semiempirical AM1 and ab initio methods. The activation barriers of CC12 adding to ASWCNT (3,3) and (4,4) are computed and compared. The lower barrier of CC12 forms cycloaddition isomer on (3,3) maybe because the strain energy of (3,3) is larger than that of (4,4). Our theoretical results are consistent with the experimental results.
基金the financial supports of NSFC(No.20805033 and 30901199)SRF for ROCS,SEM(2008890-19-9)Doctoral Education Fund for New Teachers(200806101048)
文摘Depositing single-walled carbon nanotubes(SWNTs) with controllable density, pattern and orientation on electrodes presents a challenge in today's research. Here, we report a novel solvent evaporation method to align SWNTs in patterns having nanoscale width and micronscale length. SWNTs suspension has been introduced dropwise onto photoresist resin microchannels; and the capillary force can stretch and align SWNTs into strands with nanoscale width in the microchannels. Then these narrow and long aligned SWNTs patterns were successfully transferred to a pair of gold electrodes with different gaps to fabricate carbon nanotube field-effect transistor(CNTFET). Moreover, the electrical performance of the CNTFET show that the SWNTs strands can bridge different gaps and fabricate good electrical performance CNTFET with ON/OFF ratio around 106. This result suggests a promising and simple strategy for assembling well-aligned SWNTs into CNTFET device with good electrical performance.
基金Project supported by the National Natural Science Foundation of China (Nos. 10972128 and 10472061)the Ph. D. Programs Foundation of Ministry of Education of China (No. 20060280015)the Shanghai Leading Academic Discipline Project (No. S30106)
文摘The electromechanical properties of metallic single-walled carbon nanotubes (SWCNTs) in the electric field are demonstrated with a column shell model in this paper. A hemisphere model is introduced to determine the charge distribution and the local electric field in SWCNTs. By treating the SWCNT as an elastic column shell, the analytical solutions of the charged SWCNT's axial strain and the radial strain are obtained. SWCNTs with a larger aspect ratio show greater deformation. The greatest radial deformation appears at the end of the tube. The significant axial strain can be induced in CNTs with a large length (around 100 nm) even though the applied electric field is not strong enough. When SWCNTs are fixed at both ends, the radius of SWCNTs becomes small along the axial position.
基金Supported by the National Natural Science Foundation of China under Grant No 11304378the Fundamental Research Funds for the Central Universities under Grant No 2017XKQY093
文摘The exciton states of semiconducting carbon nanotubes are calculated by a tight-binding model supplemented by Coulomb interactions under the combined effect of uniaxial strain and magnetic field. It is found that the excitation energies and absorption spectra of zigzag tubes(11,0) and(10,0) show opposite trends with the strain under the action of the magnetic field. For the(11,0) tube, the excitation energy decreases with the increasing uniaxial strain, with a splitting appearing in the absorption spectra. For the(10,0) tube, the variation trend firstly increases and then decreases, with a reversal point appearing in the absorption spectra. More interesting,at the reversal point the intensity of optical absorption is the largest because of the degeneracy of the two bands nearest to the Fermi Level, which is expected to be observed in the future experiment. The similar variation trend is also exhibited in the binding energy for the two kinds of semiconducting tubes.