Optical limiting behavior of nano-gold self-assembled multi-wall carbon nanotube

The opticallimiting behaviors of nano-gold self-assembled multi-wall carbon nanotube (MWNT) were experimentally investigated at 532 and 1064 nm, respectively. The comparison of the limiting performances between carbon nanotube suspension, C60 solution, and carbon black suspension (CBS) was performed.The results show that the optical limiting characteristic of nano-gold self-assembled MWNT is better than those of C60 and CBS. The mechanisms of the optical limiting for the samples were discussed.     

Comparison of metallic silver and copper doping effects on single-walled carbon nanotubes

In this work we performed the filling of single-walled carbon nanotube channels with metallic silver and copper by means of two-step synthesis including imbuing with metal nitrate aqueous solution and further annealing. It has been shown that metal insertion into the nanotube cavities results in the Fermi level upshift and the charge transfer from metal to carbon atoms, thus donor doping of single-walled carbon nanotubes takes place. At the same time, encapsulated silver has a larger donor effect on the carbon nanotubes that has been proved by Raman spectroscopy and X-ray photoelectron spectroscopy.     

Selective aggregation of single-walled carbon nanotubes using the large optical field gradient of a focused laser beam

We demonstrate the selective aggregation of single-walled carbon nanotubes by photon forces, using the large optical field gradient of a laser focused through a high numerical aperture objective lens. The nanotubes, dispersed in an aqueous solution with a surfactant, are detected via Raman scattering from the confocal volume of the optical trap. By using a visible-light laser for both trapping and detection, the dynamics of the radial breathing mode signal taken at short intervals shows an increase of a single breathing mode over time, indicating the increase in the density of only one species of tube in the focal volume. This result represents a significant step toward the development of techniques for the arbitrary manipulation and sorting of nanotubes by optical fields.     

剪切形变对硼氮掺杂碳纳米管超晶格电子结构和光学性能的影响

碳纳米管作为最先进的纳米材料之一, 在电子和光学器件领域有潜在的应用前景, 因此引起了广泛关注. 掺杂、变形及形成超晶格为调制纳米管电子、光学性质提供了有效途径. 为了理解相关机理, 利用第一性原理方法研究了不同剪切形变下扶手椅型硼氮交替环状掺杂碳纳米管超晶格的空间结构、电子结构和光学性质. 研究发现, 剪切形变会改变碳纳米管的几何结构, 当剪切形变大于12%后, 其几何结构有较大畸变. 结合能计算表明, 剪切形变改变了掺杂碳纳米管超晶格的稳定性, 剪切形变越大, 稳定性越低. 电荷布居分析表明, 硼氮掺杂碳纳米管超晶格中离子键和共价键共存. 能带和态密度分析发现硼氮交替环状掺杂使碳纳米管超晶格从金属转变为半导体. 随着剪切形变加剧, 纳米管超晶格能隙逐渐减小, 当剪切形变大于12%后, 碳纳米管又从半导体变为金属. 在光学性能中, 剪切形变的硼氮掺杂碳纳米管超晶格的光吸收系数及反射率峰值较未受剪切形变的均减小, 且均出现了红移.     

Fluorescence spectroscopy of single-walled carbon nanotubes in aqueous suspension

Optical studies of single-walled carbon nanotubes have advanced greatly through the recent discovery of near-infrared band gap photoluminescence from single-walled carbon nanotubes (SWNT) isolated in aqueous surfactant suspensions. This fluorescence emission has enabled the detection of many distinct optical transitions and their assignment to specific (n,m) semiconducting species of SWNT. The resulting set of precise transition energies presents a challenge to current theoretical models of nanotube electronic structure and a guide to nanotube researchers using resonance Raman spectroscopy. In the near future, structure-resolved fluorimetry should prove useful for revealing the quantitative (n,m) composition of mixed SWNT samples through sensitive, rapid, and nondestructive measurements. It will also permit detailed studies of many physical and chemical processes that vary with nanotube structure. PACS 71.35.Cc; 78.67.Ch; 78.67.-n     

Probing the Influence of Amino Acids on Photoluminescence from Carbon Nanotubes Suspended with DNA

The quantitative analysis of amino acid levels in the human organism is required for the early clinical diagnosis of a variety of diseases. In this work the influence of 13 amino acid doping on the photoluminescence (PL) from the semiconducting single-walled carbon nanotubes (SWNTs) suspended with single-stranded DNA (ssDNA) in water has been studied. Amino acid doping leads to the PL enhancement and the strongest increase was found after cysteine doping of the nanotube suspension while addition of other amino acids yielded the significantly smaller effect. The emphasis of cysteine molecules is attributed to presence of the reactive thiol group that turns cysteine into reducing agent that passivates the p-defects on the nanotube sidewall and increases the PL intensity. The reasons of PL enhancement after doping with other amino acids are discussed. The response of nanotube PL to cysteine addition depends on the nanotube aqueous suspension preparation with tip or bath sonication treatment. The enhancement of the emission from different nanotube species after cysteine doping was analyzed too. It was shown that the increase of the carbon nanotube PL at addition of cysteine allows successful monitoring of the cysteine concentration in aqueous solution in the range of 50–1000 μM.     

Comparison of influence of incorporated 3d-, 4d- and 4f-metal chlorides on electronic properties of single-walled carbon nanotubes

In the present work, the channels of single-walled carbon nanotubes were filled with melts of ZnCl₂, CdCl₂, and TbCl₃ by a capillary method with subsequent slow cooling. The detailed study of electronic structure of filled nanotubes was performed using Raman, optical absorption, and X-ray photoelectron spectroscopy. The obtained data are in mutual agreement and it proves that the filling of carbon nanotube channels with all these salts leads to the charge transfer from nanotube walls to the incorporated compounds, thus acceptor doping of nanotubes takes place. It was found out that encapsulated terbium chloride has the largest influence on the electronic properties of carbon nanotubes.     

Dispersion of boron nitride nanotubes in aqueous solution with the help of ionic surfactants

We report that ammonium oleate surfactants can help the dispersion of multiwalled boron nitride nanotubes (BNNTs) in water to form a BNNT solution stable for several months, which was due to the non-covalent functionalization of nanotube surfaces. Fourier Transform Infrared Spectroscopy (FTIR) and Photoluminescence (PL) analysis with synchrotron radiation source revealed that this BNNT aqueous solution preserves the intrinsic optical properties of BNNTs.     

Microstructural investigations of zirconium oxide—on core–shell structure of carbon nanotubes

Single-walled carbon nanotubes and multi-walled carbon nanotubes/ZrO₂ nanocomposites were obtained by isothermal hydrolyzing and chemical precipitation method for both the carbon nanotubes. The coating was taken place by dispersion of both the carbon nanotubes in ZrOCl₂·8H₂O aqueous solution. However, a highly conformal and uniform monoclinic zirconia coating was deposited on multi-walled carbon nanotubes rather than single-walled carbon nanotubes by this new and simple method. Also, it has been observed that the thickness of the individual carbon nanotube after zirconia coating was increased by isothermal hydrolyzing process rather than traditional chemical precipitation method and it has been confirmed by high-resolution transmission electron microscopy study.     

Optical transition energies for carbon nanotubes from resonant Raman spectroscopy: environment and temperature effects

This Letter reports the laser energy dependence of the Stokes and anti-Stokes Raman spectra of carbon nanotubes dispersed in aqueous solution and within solid bundles, in the energy range 1.52-2.71 eV. The electronic transition energies (E(ii)) and the radial breathing mode frequencies (omega(RBM)) are obtained for 46 different (18 metallic and 28 semiconducting) nanotubes, and the (n,m) assignment is discussed based on the observation of geometrical patterns for E(ii) versus omega(RBM) graphs. Only the low energy component of the E(M)(11) value is observed from each metallic nanotube. For a given nanotube, the resonant window is broadened and down-shifted for single wall carbon nanotube (SWNT) bundles compared to SWNTs in solution, while by increasing the temperature, the E(S)(22) energies are redshifted for S1 [(2n+m) mod 3=1] nanotubes and blueshifted for S2 [(2n+m) mod 3=2] nanotubes.     

Nonlinear vibration of carbon nanotube embedded in viscous elastic matrix under parametric excitation by nonlocal continuum theory

In the present work, the nonlinear vibration of a carbon nanotube which is subjected to the external parametric excitation is studied. By the nonlocal continuum theory and nonlinear von Kármán beam theory, the governing equation of the carbon nanotube is derived with the consideration of the large deformation. The principle parametric resonance of the nanotube is discussed and the approximation explicit solution is presented by the multiple scale method. Numerical calculations are performed. It can be observed that when the mode number is 1, the stable region can be significantly changed by the parametric excitation, length-to-diameter ratio and matrix stiffness. This phenomenon becomes different to appear if the mode number increases. Moreover, the small scale effects have great influences on the positive bifurcation point for the short carbon nanotube, and the nonlocal continuum theory can present the proper model.     

Linear and nonlinear optical properties of carbon nanotube-coated single-mode optical fiber gratings

Single-wall carbon nanotube deposition on the cladding of optical fibers has been carried out to fabricate an all-fiber nonlinear device. Two different nanotube deposition techniques were studied. The first consisted of repeatedly immersing the optical fiber into a nanotube supension, increasing the thickness of the coating in each step. The second deposition involved wrapping a thin film of nanotubes around the optical fiber. For both cases, interaction of transmitted light through the fiber core with the external coating was assisted by the cladding mode resonances of a tilted fiber Bragg grating. Ultrafast nonlinear effects of the nanotube-coated fiber were measured by means of a pump-probe pulses experiment.     

A Two-Dimensional Extremely Short Optical Pulse in a System of Carbon Nanotubes in a Direct Current Electric Field

The effect of an external dc electric field on the two-dimensional extremely short optical pulse propagating in a zigzag carbon nanotube array was investigated. The electromagnetic field evolution in the investigated nanotube system is described by the Maxwell equations. Using numerical simulation, the interaction between the pulse electromagnetic field and the external electric field applied to the carbon nanotube array is analyzed.     

Trapping and transporting aerosols with a single optical bottle beam generated by moiré techniques

We demonstrate optical trapping and manipulation of aerosols with an optical bottle beam generated by the moiré techniques. We observe stable trapping and back-and-forth transportation of a variety of absorbing carbon particles suspended in air, ranging from clusters of nanosized buckminsterfullerene C?? to micrometer-sized carbon powders.     

有序TiO2纳米管阵列结构的可控生长及其物相研究

分别在HF水溶液、含NH₄F和H₂O的乙二醇有机溶液中对Ti箔进行阳极氧化,得到TiO₂纳米管阵列结构.该结构高度有序、分布均匀、垂直取向,且通过阳极氧化工艺条件(如阳极氧化电压、电解液的选择与配比以及氧化时间等)可实现对其结构参数(如管径、管壁厚度、管密度、管长等)的有效控制.利用XRD研究了TiO₂纳米管阵列的物相结构.结果表明：退火前的TiO₂纳米管阵列为无定形结构;分别在真空和氧气氛中50 关键词： 2纳米管阵列')" href="#">TiO₂纳米管阵列 阳极氧化 可控生长     

Successful incorporation of multi-walled carbon nanotubes in nickel electrodeposited coating by electrophoresis

A homogenous and adhesive multi-walled carbon nanotube (MWCNT) coating was electrophoretically deposited on stainless steel from an aqueous solution by applying high strength electric fields. Then, nickel was electrodeposited on MWCNT films. MWCNTs content in the composite coatings was reached to 12.5 wt% which was much higher than the content of MWCNTs in conventional nickel-MWCNT electrodeposited coatings. The hardness value of composite coatings significantly increased up to 870 Vickers which it was measured by both micro and nanohardness tests.     

一维纳米SiC-CNTs复合结构的生长机制和阴极射线发光

采用直接固相反应法制备了一维SiC-CNTs纳米复合结构。初始反应原料为纯的硅粉和碳纳米管混合物,没有使用任何触媒,在1 400℃温度下获得了一维纳米产物。采用X射线衍射、扫描电子显微镜、拉曼光谱、阴极射线发光光谱研究了产物的结构和光学性质。获得的一维S iC-CNTs纳米复合结构外径约为60nm,长度超过几个微米。CL谱中存在三个发射带,中心位置分别为2.89,2.39,2.22 eV。     

Vertically aligned α-MnO<Subscript>2</Subscript> nanosheets on carbon nanotubes as cathodic materials for aqueous rechargeable magnesium ion battery

In this work, vertically aligned α-MnO₂ nanosheets on carbon nanotubes are synthesized simply by a solution process and the electrochemical performance as host materials of magnesium ion is tested in aqueous solution. Cyclic voltammetry analysis confirms the enhanced electrochemical activity of carbon nanotube-supported samples. Moreover, carbon nanotubes skeleton could reduce the charge transfer resistant of the cathode materials, which is confirmed by electrochemical impedance spectroscopy. Furthermore, when tested as magnesium ion batteries cathodic electrode, the α-MnO₂/carbon nanotube sample registers a prominent discharge capacity of 144.6 mAh g^?1 at current density of 0.5 A g^?1, which is higher than the discharge capacity of α-MnO₂ (87.5 mAh g^?1) due to the synergistic effect of insertion/deinsertion reaction and physical adsorption/desorption process. After the 1000th cycle, a remarkable discharge capacity of 48.3 mAh g^?1 is collected for α-MnO₂/carbon nanotube at current density of 10 A g^?1, which is 85% of the original. It is found that the carbon skeleton not only improved the capacity but also enhanced the cycling performance of the α-MnO₂ electrode significantly. Therefore, α-MnO₂/carbon nanotube is a very promising candidate for further application in environmentally benign magnesium ion batteries.