Purification of Single-walled Carbon Nanotubes Grown by a Chemical Vapour Deposition(CVD) Method

A procedure for purification of single walled carbon nanotubes(SWNTs) grown by the chemical vapour deposition(CVD) of carbon monooxide has been developed. Based on the result from TGA/DTA of as prepared sample, the oxidation temperature was determined. The process included sonication, oxidation and acid washing steps. The purity and yield after purification were determined and estimated by TEM. Moreover, for the first time, a loop structure for CVD SWNTs has been observed.

Ethane Adsorption in Single Walled Carbon Nanotube by Density Functional Theory

Density functional theory (DFT) is used to calculate adsorption of ethane molecules in single walled carbon nanotubes. A compari-son of DFT calculations and grand canonical ensemble Monte Carlo (GCMC) simulations is made first and the two methods are in good agree-ment. Adsorption isotherms and structures of ethane molecules inside the tubes have been studied by DFT for the nanotubes of diameters 0.954, 2.719 and 4.077 nm at 157 K and ambient temperature, 300 K. By using the grand potential, the positions of phase transitions are exactly lo-cated, and the effect of temperature and tube diameter on phase transitions and adsorption is discussed. We found that lowering temperature and increasing the pore size of several nanometer is preferable for the ethane adsorption when temperature is in the range of 157 K—300 K and op-erating pressure reaches several MPa. Layering transitions and capillary condensations are observed at 157 K in two larger pore diameters, while these phase transitions disappear or the hysteres is loops become very narrow at 300 K.

Preferable Orientations of Interacting C_(60) Molecules inside Single Wall Boron Nitride Nanotubes

This work focuses on the preferable orientation analysis of the hybrid system where the C60 molecules are encap- sulated inside the boron nitride nanotubes by using the two-molecule model. The low-energy state can be acquired in the contour map, which provides the visual information of the systematical van der Waals interaction potential for the C60 molecules adopting different orientations. Our results show that the C60 molecules exhibit the pre- ferred pentagon and hexagon orientations with the tube＇s diameter smaller and larger than 13.55A, respectively. The preferred two-bond orientation obtained in the single-molecule model is absent in this study, indicating that the intermolecular interaction of adjacent C60 molecules plays an important role in the orientational behaviors of this peapod structure.

Single Wall Carbon Nanotubes (SWCNTs) as (i) Type in the Photovoltaic Cell of Nano-Dimensions

In this paper, a new modified approach to design the photovoltaic cell has been presented by adding Single Wall Carbon Nanotubes (SWCNTs) as type (i). The main issue is to increase the efficiency of the photovoltaic cell, on the other hand, to exploit a larger range of electromagnetic wave frequencies, specifically a range within terahertz (THz) frequency domain, using 3D EM computer simulation technology (CST). It is clear in the normal PV cell start working at frequency of 500 THz, while the frequency at which the PV cell with SWCNTs operates is much less and it is close to zero, on the other hand, the PV cell with SWCNTs needs a larger cross-section area of 2800 nm2 to operate at frequency of 500 THz. This cell can be easily produced industrially, which means increases the efficiency of solar cell.

ITO-free silicon-integrated perovskite electrochemical cell for light-emission and light-detection

Halide perovskite light-emitting electrochemical cells are a novel type of the perovskite optoelectronic devices that differs from the perovskite light-emitting diodes by a simple monolayered architecture.Here,we develop a perovskite electrochemical cell both for light emission and detection,where the active layer consists of a composite material made of halide perovskite microcrystals,polymer support matrix,and added mobile ions.The perovskite electrochemical cell of CsPbBr3:PEO:LiTFSI composition,emitting light at the wavelength of 523 nm,yields the luminance more than 7000 cd/m2 and electroluminescence efficiency of 4.3 lm/W.The device fabricated on a silicon substrate with transparent single-walled carbon nanotube film as a top contact exhibits 40%lower Joule heating compared to the perovskite optoelectronic devices fabricated on conventional ITO/glass substrates.Moreover,the device operates as a photodetector with a sensitivity up to 0.75 A/W,specific detectivity of 8.56×1011 Jones,and linear dynamic range of 48 dB.The technological potential of such a device is proven by demonstration of 24-pixel indicator display as well as by successful device miniaturization by creation of electroluminescent images with the smallest features less than 50μm.

Plasmon-enhanced ultra-high photoresponse of single-wall carbon nanotube/copper/silicon near-infrared photodetectors

Single wall carbon nanotube(SWCNT)/Si heterojunction photodetectors have the advantages of high photoresponse ability and simple structure,however,their detection wavelength range are usually lower than 1100 nm,which limits their application in the infrared band.We report a SWCNT/Cu/Si photodetector with both a high photoresponse and a detection range up to the infrared band by depositing a Cu nanoparticles(NPs)layer between a SWCNT film and a n-Si substrate.It was found that the Cu NPs produce strong surface plasmon resonance(SPR)under laser irradiation,which breaks through the limitation of Si band gap and greatly improves the photoresponse of the SWCNT/Cu/Si photodetector in the near infrared band.The responsivity(R)of the photodetector in the wavelength range of 1850–1200 nm reached 2.2–14.15 mA/W,which is the highest value in the reported plasmon enhanced n-Si based photodetectors,and about 20,000 times higher than that of a SWCNT/Si photodetector.Its R value for 1550 nm wavelength used in optical communications reached~8.2 mA/W,which is 64%higher than the previously reported values of commonly used photodetectors.We attribute the significant increase to the strong SPR and low Schottky barrier of Cu with n-Si,which facilitates the generation and transfer of the carriers.

Improvement of electrical and photovoltaic properties of methyl red dye based photoelectrochemical cells in presence of single walled carbon nanotubes

In this work, we investigated the effect of single walled carbon nanotubes （SWCNT） on the electrical and photovoltaic properties of methyl red （MR） dye based photoelectrochemical cell （PEC）. MR dye based PEC with LiCl04 as ion salt were fabricated with and without mixing SWCNT. The cells were characterized through electrical and optical measurements. The performance of the devices changed drastically in presence of SWCNT. The transition voltage and trap energy of the cells were estimated from the steady-state dark current voltage （I-V） analysis. The transition voltage and trap energy decreased for MR dye cell in presence of SWCNT. Open circuit voltage （Voc）, short circuit current （Jsc）, fill factor （FF） and power conversion efficiency （v/） increased due to the addition of SWCNT. Further measurement of the transient photo- current showed that the growth and decay of photocurrent was quite faster in presence of SWCNT. The photocurrent decay with time was fitted for both the cells and found to follow a power law relation which indicates dispersive transport mechanism with exponential trap states distrib- uted in between lowest unoccupied molecular orbital （LUMO） and highest occupied molecular orbital （HOMO） levels. Possible interpretation is done on the lowering of trap energy with the photocurrent. These results suggest that SWCNT lowers the trap energy of the cells by providing efficient percolation pathways for the conduction of charges. It is expected that due to lowering of trap energy the residing time of the free carriers within the traps decreases. In other words, it may also be said that the charge recombination decreases. These factors affect the overall conduction of charges and improve the electrical and photovoltaic properties.

Electrochemical Studies of Cytochrome c on Electrodes Modified by Single-Wall Carbon Nanotubes

Single wall carbon nanotubes (SWNTs) modified gold electrodes were prepared by using two different methods. The electrochemical behavior of cytochrome c on the modified gold electrodes was investigated. The first kind of SWNT modified electrode (noted as SWNT/Au electrode) was prepared by the adsorption of carboxyl terminated SWNTs from DMF dispersion on the gold electrode. The oxidatively processed SWNT tips were covalently modified by coupling with amines (AET) to form amide linkage. Via Au—S chemical bonding, the self assembled monolayer of thiol unctionalized nanotubes on gold surface was fabricated so as to prepare the others SWNT modified electrode (noted as SWNT/AET/Au electrode). It was shown from cyclic voltammetry experiments that cytochrome c exhibited direct electrochemical responses on the both electrodes, but only the current of controlled diffusion existed on the SWNT/Au electrode while both the currents of controlled diffusion and adsorption of cytochrome c occurred on the SWNT/AET/Au electrode. Photoelastic Modulation Infared Reflection Absorption Spectroscopy (PEM IRRAS) and Quartz Crystal Microbalance (QCM) were employed to verify the adsorption of SWNTs on the gold electrodes. The results proved that SWNTs could enhance the direct electron transfer process between the electrodes and redox proteins.

Demonstration of Covalent Sidewall Functionalization of Single Wall Carbon Nanotubes by NMR Spectroscopy:Side Chain Length Dependence on the Observation of the Sidewall sp^(3)Carbons

Carboxylic acid-functionalized single walled carbon nanotubes(SWNTs)prepared via the reaction of an amino acid,NH2(CH2)nCO2H where n=1(glycine,GLY),5(6-aminohexanoic acid,AHA),10(11-aminoundecanoic acid,AUDA),with fl uorinated single walled carbon nanotubes(F-SWNTs)have been characterized by MAS 13C NMR spectroscopy.The ease of observing the aliphatic CH2 groups and the resolution of the signal are dependent on the length of the amino acid’s aliphatic chain.We have proposed that where substituent chains are short(making NMR data collection difficult)chemical modification to extend the chain length should alleviate analysis problems.In this regard,we have investigated the esterifi cation of the carboxylic acid termini.The amino acid-functionalized SWNTs were esterified with an appropriate alcohol to ensure parity of the overall substituent length,i.e.,GLY-SWNT(C1)+1-dodecanol(C_(12))=DOD-GLY-SWNT(1),AHA-SWNT(C_(5))+1-octanol(C_(8))=OCT-AHA-SWNT(2),and AUDA-SWNT(C_(10))+1-propanol(C_(3))=PRO-AUDA-SWNT(3).The 13C NMR shift for the sp3 nitrogen-substituted carbon atoms of the SWNT sidewall is observed atδ≈75 ppm.Increasing the length of SWNT sidewall functional groups enhances the ability to observe the sidewall sp^(3)carbon.The methylene carbon signal intensity is less attenuated in the dipolar dephasing spectrum of the ester-functionalized SWNTs than their associated amino acid derivatives,suggesting more motional freedom of the side chain in the solid state.The confi rmation of the dipolar dephasing spectral effects was assisted by the characterization of the ester of AUDA-SWNT with 1,3-propanediol:PPD-AUDA-SWNT(4).

Comprehensive study of nanostructured supports with high surface area for Fischer-Tropsch synthesis

An extensive study of Fischer-Tropsch synthesis on nanostructure supports with high surface area such as nanostructure -y-alumina, single wall carbon nanotubes （SWNTs）, and the hybrid of SWNTs/nanostructure -y-alumina has been investigated. The nanostructure γ-alumina was promoted with lanthanum to obtain better performance of catalyst and 15 wt% cobalt loading was the basis of our investigation. Fischer- Tropsch synthesis was performed in a fixed bed reactor under different reaction conditions （220-240 ℃, 15-25 bar, H2/CO ratio of 2, GHSV of 900-1400） in order to study the effects of temperature, pressure and gas hourly space velocity （GHSV） changes on hydrocarbon selec- tivity and catalyst activity. The catalysts were extensively characterized by different methods including X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, inductively coupled plasma （ICP）, hydrogen （H2） chemisorption and temperature-programmed reduction （TPR）. The results showed that the yield of hybrid supported catalyst （55.4%） is higher than that of nanos- tructure -y-alumina supported catalyst （55.0%） and lower than that of SWNTs supported cobalt catalyst （71.0%）. The hybrid supported catalyst showed higher reduction degree and dispersion of cobalt particles. The temperature, pressure and GHSV effects on hybrid supported catalyst were studied and results showed that higher pressure favors the chain growth and temperature increase leads to the increases in methane selec- tivity and CO conversion. Higher hydrocarbon selectivity and CO conversion showed positive relationship with increasing GHSV while lower hydrocarbon selectivity diminishes.

Carbon nanotube-based nanoelectromechanical resonatoras mass biosensor

The use of single walled carbon nanotube-based nanoelectromechanical system(NEMS)resonator to sense the biomolecules'mass is investigated under the influence of an external ac-field.A single walled carbon nanotube(SWCNT)cantilever has been proposed and studied if the mass is attached at the tip or various intermediate positions.The shift of the resonant frequency and the quality factor have been investigated and show high sensitivity to the attached mass of biomolecule and its position.The proposed SWCNT-based NEMS resonator is a good candidate for sensing and tracing biomolecules'mass as concentration of acetone in human exhale,resulting in a painless,correct,and simple diabetics'diagnosis.

Quantum Chemistry Calculation on Oxygen and Nitrogen Adsorption in Carbon Nanotude

Oxygen and nitrogen adsorption in single walled carbon nanotube (SWCNT) is studied by density function and discrete variational (DFT-DVM) method.The models of O 2 and N 2 adsorption in the SWCNT are optimized based on the energy minimization.The calculated results of density of state,populations and energy gaps of the molecular orbitals show that oxygen adsorption in SWCNT increases the carbon nanotube`s electrical conductivity more notably than nitrogen adsorption,which is consistent with the experiment.

Nonlinear vibration analysis of an embedded branched nanofluid-conveying carbon nanotube:Influence of downstream angle,temperature change and two dimensional external magnetic field

In this study,non-linear thermal-mechanical stability and vibration analyses of different end-shaped single-walled carbon nanotube conveying viscous nano-magnetic fluid embedded in non-linear visco-elastic foundation under the influence of magnetic fields are presented.The development of the equation of motion was based on Euler-Bernoulli theory,Hamilton principle and nonlocal elasticity theory.The results of the analytical solutions using Galerkin decomposition differential transform method(GDDTM)were validated with existing experimental results.From the parametric studies,it was shown that decreasing the temperature difference as well as increasing the downstream angle decreased the system's stability for pre-bifurcation analysis but increased stability of the system for post bifurcation analysis.Also,the results obtained from the dynamic behaviour of the system indicated that the magnetic effect had an attenuating impact of about 45%on the system's response at any mode and for any boundary condition considered.It is hoped that this work will enhance the design and optimization of nano-devices with I,V,Y,L,K and T-shaped junctions under the influence of thermal-magneto-mechanical flow induced vibration.

Midinfrared optical frequency comb based on difference frequency generation using high repetition rate Er-doped fiber laser with single wall carbon nanotube film

We demonstrated stable midinfrared(MIR) optical frequency comb at the 3.0 μm region with difference frequency generation pumped by a high power, Er-doped, ultrashort pulse fiber laser system. A soliton mode-locked161 MHz high repetition rate fiber laser using a single wall carbon nanotube was fabricated. The output pulse was amplified in an Er-doped single mode fiber amplifier, and a 1.1–2.2 μm wideband supercontinuum(SC) with an average power of 205 m W was generated in highly nonlinear fiber. The spectrogram of the generated SC was examined both experimentally and numerically. The generated SC was focused into a nonlinear crystal, and stable generation of MIR comb around the 3 μm wavelength region was realized.

Single-wall carbon nanotube-containing cathode interfacial materials for high performance organic solar cells

Water/alcohol soluble cathode interfacial materials(CIMs)are playing important roles in optoelectronic devices such as organic light emitting diodes,perovskite solar cells and organic solar cells(OSCs).Herein,n-doped solution-processable single-wall carbon nanotubes(SWCNTs)-containing CIMs for OSCs are developed by dispersing SWCNTs to the typical CIMs perylene diimide(PDI)derivatives PDIN and PDINO.The Raman and X-ray photoelectron spectroscopy(XPS)measurement results illustrate the ndoped behavior of SWCNTs by PDIN/PDINO in the blend CIMs.The blended and n-doped SWCNTs can tune the work function and enhance the conductivity of the PDI-derivative/SWCNT(PDI-CNT)composite CIMs,and the composite CIMs can regulate and down-shift the work function of cathode,reduce the charge recombination,improve the charge extraction rate and enhance photovoltaic performance of the OSCs.High power conversion efficiency(PCE)of 17.1%and 17.7%are obtained for the OSCs based on PM6:Y6 and ternary PM6:Y6:PC_(71) BM respectively with the PDI-CNTcomposites CIMs.These results indicate that the ndoped SWCNT-containing composites,like other n-doped nanomaterials such as zero dimensional fullerenes and two dimensional graphenes,are excellent CIMs for OSCs and could find potential applications in other optoelectronic devices.

Structure of Graphene, and Mechanical and Bonding Characteristics of Single Wall Carbon Nanotube by Linear Scaling Quantum Mechanical Method

Using a linear scaling self-consistent-charge density functional tight binding （SCC-DFTB） and an ab initio Omol method, the bonding characteristics and Young＇s modulus of （10, 0） and （10,10） single-walled carbon nanotubes are calculated. The structure of a graphene is also calculated. It is found that the C-C and C-H bond length, their distribution characteristics on the tube, and Young^s modulus of the tube by linear scaling SCC-DFTB are identical to those by ab initio, while the computing cost by the linear scaling SCC-DFTB is reduced by more than 30 times as compared with that by the Dmol for the （10,0） and （10,10） tubes. By computing the structure of a graphene it is also found that the linear scaling SCCDFTB is reliable and time-saving.

Tunable filter Raman spectroscopy of purified semiconducting and metallic carbon nanotubes

Tunable filter Raman spectroscopy is used to efficiently produce Raman excitation maps of unpurified and type-purified single walled carbon nanotubes (SWCNTs). Maps with fine excitation resolution (1 nm) are created over a wide wavelength range (727 to 980 nm), extending from metallic to semiconducting resonances. At a given wavelength, the wide bandwidth (>3,000 cm–1) allows the comparison of the G band with the radial breathing mode (RBM), and shows the 2D band and other less prominent bands. Materials examined included unsorted powders, aqueous sorted semiconductors, aqueous sorted metals, and polyfluorene sorted semiconductors in toluene. The Raman excitation profiles of the G band are broad, relative to the RBM bands. The maps offer evidence of minority species contamination, except in the case of the polyfluorene sorted semiconductors. Tunable Raman spectroscopy data help validate the simpler fixed wavelength Raman spectroscopy approaches to purity assessment. [Figure not available: see fulltext.] © 2016, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

Effect of electric field on metallic SWCNT interconnects for nanoscale technologies

The influence of an electric field on metallic single walled carbon nanotube （SWCNT） interconnects is studied. A voltage-dependent equivalent circuit model is presented for the impedance parameters of single-wall carbon nanotubes that capture various electron-phonon scattering mechanisms as a function of the electric field. To estimate the performance of SWCNT bundle interconnects, signal delay and power dissipation are calculated based on the field dependent model that results in an improvement in the delay and power estimation accuracy compared to the field-independent model. We find that the power delay product of a SWCNT bundle increases with the increase in electric field but decreases with technology scaling showing that at a low electric field, the SWCNT bundle is a potential reliable alternative interconnect for future high performance VLSI industry at scaled technologies.

Structure adapting of bulk FeS_(2) micron particles and the corresponding anode for high performance sodium-ion batteries

The practical application of Pyrite iron disulfide (FeS_(2)) as anode material of sodium-ion battery is limitedby its low electronic conductivity, large volume changes during charge/discharge. To overcome thesechallenges, a novel structure design single-walled carbon nanotubes (SWCNTs) composited polyaniline(PANI)-wrapped FeS_(2) (FeS_(2)-PANI-SWCNTs) electrodes are successfully achieved in this work. PANI canprotect the FeS_(2) particles from collapse and offer a protective layer to relive the polysulfides shuttlingeffect, and also promote the electron and Naþ diffusion during the chemical conversion process. Underthe dual protection of PANI and SWCNTs, the FeS_(2)-PANI-SWCNTs film electrode demonstrates a goodstructural integrity, which accounts for the excellent rate capability and long cycling performance. Inaddition, the PANI coating and SWCNT network in the fabricated electrode can synergistically anchorpolysulfides and therefore strongly suppress shuttle effect during the chargeedischarge processes,resulting in less capacity loss. The anode with a loading 3.2 mg cm 2 of FeS_(2) coated with PANI exhibitsthe initial coulombic efficiency of 81.5% and delivers a specific capacity of 625.8 mAh g^(-1) after 100 cyclesat 200 mA g^(-1). High flexible and binder-free FeS_(2)-PANI-SWCNTs film anode demonstrates a reversiblecapacity of 537 mAh g^(-1) after 550 cycles at 1 A g^(-1). This research may offer an efficient method toimprove electrochemical performance of the metal sulfides in sodium-ion batteries.

Promoting Si-graphite composite anodes with SWCNT additives for half and NCM 811 full lithium ion batteries and assessment criteria from an industrial perspective

Single wall carbon nanotube(SWCNT)additives were formulated into(im-Si-graphite composite electrodes and tested in both half cells and full cells with high nickel cathodes.The critical role of small amount of SWCNT addition(0.2 wt%)was found for significantly improving delithiation capacity,first cycle coulombic efficiency(FCE),and capacity retention.Particularly,Si(10 wt%)-graphite electrode exhibits 560 mAh/g delithiation capacity and 92%FCE at 0.2 C during the first chargedischarge cycle,and 91%capacity retention after 50 cycles(0.5 C)in a half cell.Scanning electron microscope(SEM)was used to illustrate the electrode morphology,compositions and promoting function of the SWCNT additives.In addition,full cells assembled with high nickel-NCM811 cathodes and fim-Si-graphite composite anodes were evaluated for the consistence between half and full cell performance,and the consideration for potential commercial application.Finally,criteria to assess Si-containing anodes are proposed and discussed from an industrial perspective.