Efficient Direct Water-Solubilisation of Single-Walled Carbon Nanotube Derivatives

Application under mild conditions of a one-pot reductive-oxidative synthetic protocol to single-walled carbon nanotubes (SWNT) affords water-soluble oxygenated products that have been characterised by mean of XPS, solution ¹H-NMR, UV-VIS-NIR, vibrational FTIR and Raman, SEM-energy dispersive x-ray (EDX), XRD, and ESI-MS techniques. Different oxygenated functionalities are evicted to be covalently bonded to carbon nanotubes frameworks, due to electrophilic insertion of O₂ upon reduced carbon structures. The pH-dependent behaviour in water solution and the observed partial fragmentation of oxidised nanotubes, that can contribute in enhancing water solubility by shortening structures, are discussed. Prolonged heating of the material affords a higher graphitisation index of the functionalised carbonaceous water-soluble frameworks, and possible chemical paths for the partial recovering of pristine carbon nanostructures are reported. The achieved hydrophily due to polar oxygen moieties insertions on nanostructures provides a remarkable unprecedented water solubility for these carbon substrates without the attachment of large polar appendages.     

Ultrahigh Frequency Carbon Nanotube Transistor Based on a Single Nanotube

Single-walled carbon nanotube field-effect transistors (CNT FETs) are predicted to have intrinsic cutoff frequencies approaching the THz range. Here ldquointrinsicrdquo means that the parasitic capacitance due to fringing fields is negligible compared to the gate-source capacitance required to modulate the conductance. In practice, although there are strategies proposed to mitigate this based on parallel arrays of CNT FETs, this parasitic capacitance dominates most geometries (even aligned arrays to date). In this work we show nanotube transistor performance with maximum stable gain above 1 GHz (even including the parasitics) by combining ldquoon-chiprdquo the electrical properties of 100 CNT FETs fabricated on one long nanotube. This also solves the problem of impedance matching by boosting the on current to a large (mA) value, and at the same time allows one to extract properties of each individual CNT FET, since they are identical in electrical characteristics as they are made out of the same CNT. This strategy opens the door to applications of carbon nanotube devices in the RF and microwave frequency range, a technologically relevant portion of the spectrum for both wired and wireless electronics, that has been (until now) incompatible with nanotube device technology.     

Electrothermal Characterization of Single-Walled Carbon Nanotube (SWCNT) Interconnect Arrays

Electrothermal characterization of a metallic single-walled carbon nanotube (SWCNT) interconnect array is performed in this paper. The array is biased by a high voltage or under the impact of an electrostatic discharge pulse current. Using both time-dependent and -independent finite-difference methods, 1-D longitudinal heat conduction equation of SWCNT in the array is first solved, with CNT length-dependent temperature distribution, breakdown voltage, power handling capability, as well as transient thermal response captured and compared. Two modified equivalent electrothermal circuit models of a single SWCNT and an SWCNT array are proposed to accurately characterize hybrid effects of the biasing voltage, CNT length, and maximum rise in temperature. Their electrothermal circuit models are further implemented for investigating self-heating impact on signal integrities of SWCNT interconnect arrays, in particular, time-delay-induced crosstalk and noise. It is theoretically demonstrated that self-heating effect should be considered carefully in the design of local SWCNT interconnects when a high biasing signal voltage is applied.      

Improving the Electrical Contact Property of Single-Walled Carbon Nanotube Arrays by Electrodeposition

Nano-Micro Letters - A parallel method for the fabrication of metal contacts on single-walled carbon nanotube (SWNT) arrays was presented and the electrical contact property was evaluated by a...     

Study of Random Telegraph Signals in Single-Walled Carbon Nanotube Field Effect Transistors

Random telegraph signals (RTSs) are observed in the single-walled carbon nanotube (SWNT) field-effect transistors. The RTS mechanism is studied in detail. It is shown that trapping/detrapping due to the defects in the oxide is the main reason for RTSs in the carbon nanotube field-effect transistors (CNT-FETs). The amplitude of the RTSs in CNT-FETs is mainly attributed to mobility modulation. The defect causing the RTSs is a hole-type Coulomb repulsive center located near the valance band of the SWNT.     

Equilibrium Parameters of the Interaction of a C60 Fullerene Molecule with a Single-Walled Carbon Nanotube

Technical Physics Letters - The potential of the interaction between a C60 fullerene molecule and a single-walled carbon nanotube is calculated. Using this potential, the equilibrium distance and...     

Pseudo Y-Junction Single-Walled Carbon Nanotube Based Ambipolar Transistor Operating at Room Temperature

A nanoscale field-effect transistor (FET) was fabricated based on pseudo Y-junction single-walled carbon nanotubes (Y-SWNTs). The Y-junction transistor was modulated by a metallic branch of the Y-SWNTs, and exhibited ambipolar FET characteristics at room temperature. A subthreshold swing of 700 mV/decade and an on/off ratio of 10⁵ with a low off-state current of ~10^-13 A were obtained. Analysis of the electrical transport of pseudo Y-SWNTs is fundamental to the study of transport properties in a carbon nanotube mat (CNT-mat)     

Transparent and Freestanding Single-Walled Carbon Nanotube Films Synthesized Directly and Continuously via a Blown Aerosol Technique

Single-walled carbon nanotube (SWCNT) films are promising materials as flexible transparent conductive films (TCFs). Here, inspired by the extrusion blown plastic film technique and the SWCNT synthesis approach by floating catalyst chemical vapor deposition (FCCVD), a novel blown aerosol chemical vapor deposition (BACVD) method is reported to directly and continuously produce freestanding SWCNT TCFs at several hundred meters per hour. The synthesis mechanism, involving blowing a stable aerosol bubble and transforming the bubble into an aerogel, is investigated, and a general phase diagram is established for this method. For the SWCNT TCFs via BACVD, both carbon conversion efficiency and SWCNT TCF yield can reach three orders of magnitude higher than those with the conventional FCCVD. The film displays a sheet resistance of 40 ohm sq⁻¹ at 90% transmittance after being doped, representing the record performance based on large-scale SWCNT films. Transparent, flexible, and stretchable electrodes based on BACVD films are demonstrated. Moreover, this high-throughput method of producing SWCNT TCFs can be compatible with the roll-to-roll process for mass production of flexible displays, touch screens, solar cells, and solid-state lighting, and is expected to have a broad and long-term impact on many fields from consumer electronics to energy conversion and generation.     

碳纳米管弯曲和拉伸等效弹性模量的计算分析

碳纳米管中的结合键为C-C共价键,它有3个特征参数：键能、键长和键角,首先给出C-C键合关系的坐标描述,然后基于对势函数定义了相应的势能泛函,并建立了相应的计算模型,系统分析了不同手性矢量参数单壁碳纳米管在拉伸和弯曲情形下的力学行为,基于实验结果,按碳纳米管的中空结构计算了相应的等效弹性模量,研究了扶手椅型SWNT(3,3)～SWNT(14,14)的等效弹性模量变化规律,研究结果表明,在拉伸和弯曲情形下。按碳纳米管中空结构计算得到的等效弹性模量为237-239GPa,泊松比为0.21,该结果具有实验上的统计性质。     

多壁碳纳米管湿度传感器频率特性(英文)

为了研究测试频率对传感器性能的影响,改善多壁碳纳米管(multi-walled carbon nanotubes,MWCNTs)湿度传感器检测方法并提高传感器检测精度,对传感器频率特性进行了分析.在玻璃衬底上利用蒸镀和光刻技术制作了叉指电极,在电极表面涂敷了MWCNTs-SiO2敏感薄膜,最后通过烧结完成传感器制作.利用饱和盐溶液法产生相应湿度值,并使用RCL自动测试仪对传感器进行测试,测试频率选择在1 kHz到500 kHz之间.对传感器频率特性进行了实验与理论分析,结果表明,该传感器电容值对环境湿度敏感,并且其敏感特性受传感器检测频率的影响.使用毛细凝聚理论以及电解质物理理论对上述实验现象进行了合理的解释.传感器静态电容以及对湿度的灵敏度均随着测试频率的增加明显降低,测试频率为500 kHz时传感器灵敏度仅为测试频率1 kHz时的0.24倍.     

Proximity Effect of Magnesium Diboride on Single-Walled Carbon Nanotube: an Ab Initio Study

Magnesium diboride (MgB₂) superconductor with excellent physical properties continues to attract the attention of researchers since its discovery. It derives its versatility from the absence of weak links, large coherence length, and small anisotropy. On the other hand, reports of superconductivity in small-diameter single-walled carbon nanotubes (SWCNTs) suspended between superconducting contacts and proximity induced supercurrents in Ta/SWNTs/Au junctions have also aroused great interest in the scientific community. Proximity induced superconductivity in SWCNTs has opened up new frontiers of research which will lead to many novel discoveries. This paper reports ab initio investigations on the proximity effect of MgB₂ on the electronic structure of a SWCNT. Condensation of electronic states is observed in the electronic band structure of the pristine SWCNT when MgB₂ is held in proximity. An additional band gap is generated below the lowest energy state of the valence band of the pristine CNT which we suggest, is due to Cooper pair formation. This leads to the prediction that SWCNTs will show superconducting properties in proximity of MgB₂. We envision MgB₂-coated SWCNTs as a novel nanomaterial that has a combination of proximity induced superconductivity and inherently unique mechanical and optical properties of SWCNTs.     

The Influence of Cs Adsorption on Field Electron Emission from Single-Walled Carbon Nanotube Layers

The influence of Cs adsorption on field emission characteristics of single-walled carbon nanotube (SWNT) layers has been investigated. It has been found that Cs adsorption onto SWNT tips not only decreases the work function of SWNTs with the corresponding increase of the emission current, but also causes the additional increasing of the emission current in tens times without the decrease of the work function. We attribute the second effect to the appearance of local surface states associated with Cs, that increase the transparency of the surface potential barrier.     

Thermal Conductivity of Single-Walled Carbon Nanotube with Internal Heat Source Studied by Molecular Dynamics Simulation

The thermal conductivity of (5, 5) single-walled carbon nanotubes (SWNTs) with an internal heat source is investigated by using nonequilibrium molecular dynamics (NEMD) simulation incorporating uniform heat source and heat source-and-sink schemes. Compared with SWNTs without an internal heat source, i.e., by a fixed-temperature difference scheme, the thermal conductivity of SWNTs with an internal heat source is much lower, by as much as half in some cases, though it still increases with an increase of the tube length. Based on the theory of phonon dynamics, a function called the phonon free path distribution is defined to develop a simple one-dimensional heat conduction model considering an internal heat source, which can explain diffusive-ballistic heat transport in carbon nanotubes well.     

单壁碳纳米管作沟道的场效应晶体管输运特性理论研究

为研究以单壁碳纳米管(CNT)作沟道的场效应晶体管(FET)的输运特性,采用非平衡格林函数(NEGF)理论,构建了CNTFET的电子输运模型,该方法摒弃粗糙的连续体模型,可实现CNTFET输运性质与手性指数的直接对接。以(17,0)锯齿型管为例,数值计算了CNTFET输出特性、转移特性、跨导、亚阈值摆幅、开关态电流比等电学特性;在等效栅氧化层厚度相同的情况下,对比了采用不同栅介质材料时上述电学特性在数值上的差异,发现随栅介质介电常数的增加,漏感应势垒降低效应变得显著,这不但导致开态时从源注入到漏的电子浓度增加、电流增大,也导致关态电流增大,开关态的电流比减少。研究还发现在通常的栅源和漏源电压下,沟道中出现热电子。     

Alignment of Nanoscale Single-Walled Carbon Nanotubes Strands

Nano-Micro Letters - Depositing single-walled carbon nanotubes (SWNTs) with controllable density, pattern and orientation on electrodes presents a challenge in today’s research. Here, we...     

碳纳米管纤维研究进展

主要概述了碳纳米管纤维的最新研究进展,详细介绍了当前碳纳米管纤维的3种主要制备方法--溶液纺丝、阵列抽丝以及浮动CVD直接纺丝法,探讨了各种工艺参数对碳纳米管纤维纺丝工艺以及产品最终性能的影响,分析和展望了碳纳米管纤维目前仍存在的一些关键问题和可能的发展方向、应用前景等.     

纳米碳管在聚合物中的应用及其复合材料研究进展

介绍了纳米碳管的制备、表面改性等，论述了纳米碳管在聚合物中的应用及其复合材料的制备方法和研究进展，并总结了存在的主要问题，展望了纳米碳管／聚合物基复合材料的应用前景。