碳纳米管晶格振动模及拉曼光谱的研究进展

本文介绍了碳纳米管的结构特征和晶格振动模的理论研究 ,综述了不同方法生长的多壁碳纳米管和单壁碳纳米管拉曼光谱的研究进展。另外 ,还简单描述了单壁碳纳米管的应用前景     

碳纳米管拉曼光谱研究新进展

本文介绍碳纳米管拉曼光谱研究的最新进展。重点介绍金属性和半导体性碳纳米管的共振拉曼效应、表面增强拉曼效应和偏振拉曼效应。同时也介绍了碳纳米管的温度效应、压力效应和杨氏模量的拉曼光谱研究     

Preparation and characterization of carbon nanotubes encapsulated GaN nanowires

A novel two-step catalytic reaction is developed to synthesize gallium nitride nanowires encapsulated inside carbon nanotubes (GaN@CNT). The nanowires are prepared from the reaction of gallium metal and ammonium using metals or metal alloys as a catalyst. After the formation of the nanowires, carbon nanotubes are subsequently grown along the nanowires by chemical vapor deposition of methane. The structural and optical properties of pure GaN nanowires and GaN@CNT are characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and Raman spectroscopy. The results show that GaN nanowires are indeed encapsulated inside carbon nanotubes. The field emission studies show that the turn-on field of GaN@CNT is higher than that of carbon nanotubes, but substantially lower than that of pure GaN nanowires. This work provides a wide route toward the preparation and applications of new one-dimensional semiconductor nanostructures.     

Optical studies of carbon nanotubes and nanographites

Resonance Raman and photoluminescence excitation (PLE) spectroscopies are used to study the optical properties of different types of carbon nanostructures such as carbon nanotube, nanoribbons, nanographites and graphite edges. In the resonance Raman experiments of carbon nanotubes, the (n,m) assignment is obtained by comparing the experimental and theoretical diameter and chirality dependence of the optical transitions. The influence of the environment on the optical transitions of the nanotubes is also obtained in the Raman experiments. The PLE measurements in different samples of carbon nanotubes show both direct and phonon-assisted optical transitions, and the results give new evidences that the optical transitions in nanotubes have an excitonic character, which is very strong for the low energy transitions. We also analyze the Raman spectra of nanoribbons and nanographites, showing that this technique is an important tool for defect characterization in graphitic materials, and can be used to distinguish the atomic structure of the graphite edges.     

New progress of plasmonics in complex metal nanostructures

Noble metal nanostructures possess novel optical properties because of their collective electronic oscillations,known as surface plasmons(SPs).The resonance of SPs strongly depends on the material,surrounding environment,as well as the geometry of the nanostructures.Complex metal nanostructures have attracted research interest because of the degree of freedom in tailoring the plasmonic properties for more advanced applications that are unattainable by simple ones.In this review,we discuss the plasmonic properties of several typical types of complex metal nanostructures,that is,electromagnetically coupled nanoparticles(NPs),NPs/metal films,NPs/nanowires(NWs),NWs/NWs,and metal nanostructures supported or coated by dielectrics.The electromagnetic field enhancement and surface-enhanced Raman scattering applications are mainly discussed in the NPs systems where localized SPs have a key role.Propagating surface plasmon polaritons and relevant applications in plasmonic routers and logic gates using NWs network are also reviewed.The effect of dielectric substrates and surroundings of metal nanostructures to the plasmonic properties is also discussed.     

Recent advances in carbon nanotube photophysics

A review is given of how resonance Raman spectroscopy (RRS) and photoluminescence (PL) can be used to reveal unique information about nanostructures, 1 nm in diameter, thus providing new techniques for probing the electronic and vibrational properties of nanostructures. Special attention is given to recent advances made in this field.     

Optical emission and Raman scattering in modulation-doped gaAs-AlGaAs quantum wires and dots

Magneto-optical properties and resonant Raman spectroscopy of modulation doped GaAs-AlGaAs quantum well wires are reported. Their properties are compared with similar undoped quantum well wires to investigate the many electron effects in nanostructures. In undoped samples, the quantised energy levels observed by luminescence excitation spectroscopy are in good agreement with a particle-in-a-box model. In doped samples, the carrier confinement is explicitly revealed by magneto-luminescence and depolarised resonant Raman scattering. The calculated spectra in a Hartree model are in reasonable agreement with experiment.PACS: 78.66.Fd, 78.30.Fs, 78.55.Cr, 73.20.Dx     

Effect of Pt and Fe catalysts in the transformation of carbon black into carbon nanotubes

In this research carbon nanotubes and carbon nano onion-like structures were synthesized from carbon black using metal catalysts at 400 °C and 700 °C. Platinum and iron-group metals were used as catalysts for the transformation of CB into graphitized nanocarbon and the effect of both metals was compared. The synthesized products were characterized using X-ray diffraction (XRD), transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM) and Raman spectroscopy. The characterization shows that this process is very efficient in the synthesis of high quality graphitized products from amorphous carbon black, even though the process temperature was relatively low in comparison with previous studies. Distinguished graphitic walls of the newly formed carbon nanostructures were clearly visible in the HRTEM images. Possible growth difference related to the type of catalyst used is briefly explained with the basis of electron vacancies in d-orbitals of metals.     

Phonons in carbon nanotubes

A broad review of the unusual one-dimensional properties of phonons in carbon nanotubes is presented, including phonons in isolated nanotubes and in crystalline arrays of nanotubes in nanotube bundles. The main technique for probing the phonon spectra has been Raman spectroscopy and the many unique and unusual features of the Raman spectra of carbon nanotubes are reviewed. Also included is a brief review of the thermal properties of carbon nanotubes in relation to their unusual phonon dispersion relations and density of states.     

Impact of Mo and Ce on growth of single-walled carbon nanotubes by chemical vapour deposition using MgO-supported Fe catalysts

A series of nine catalysts containing Ce/Fe and Mo/Fe at various loadings on MgO supports have been studied as catalysts for chemical vapour deposition (CVD) of single-walled carbon nanotubes (SWCNTs) using a methane carbon source. Our results show that the Ce/Fe system is very suitable as a catalyst that favours SWCNT growth, and we question the special importance that has been attributed to Mo as an additive to Fe-based catalysts for SWCNT growth, as it appears that Ce is equally effective. Our results indicate that dehydroaromatization (DHA) is not a defining step for the growth mechanism, as has been suggested for Mo/Fe systems previously, and show that Ce and Mo do not seriously perturb the well-known Fe/MgO system for growth of high quality SWCNT. Using Raman spectroscopy, we have shown that the Ce/Fe/MgO catalyst system favours growth of SWCNTs with a different distribution of chiralities compared to the analogous Mo/Fe/MgO system.     

拉曼描述碳纳米管系统:缺陷探测,产物热处理,过程分析和催化剂(英文)

利用拉曼散射技术从多角度研究了碳纳米管合成系统。发现拉曼散射技术不仅可表征碳纳米材料本身的特性,而且可分析宏观的多壁碳纳米管与单壁碳纳米管的生长过程。针对不同的碳纳米材料的生长特性提出了催化剂与反应器设计及过程控制的研究方向。同时还发展了一种基于拉曼光谱法的定量测定单壁碳纳米管含量的方法。     

一维纳米材料的拉曼光谱学研究

本文将报告对硅纳米线、多孔硅、Si C纳米棒和碳纳米管等一维纳米体系的本征拉曼光谱及其特征的研究结果 ,并讨论拉曼光谱在上述材料的几何和物理特性研究中的应用。     

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。     

Comparison of modification of electronic properties of single-walled carbon nanotubes filled with metal halogenide, chalcogenide, and pure metal

In present work, thulium chloride, gallium selenide, bismuth telluride, and silver were encapsulated into the channels of single-walled carbon nanotubes (SWCNTs). The structural properties of obtained nanostructures were studied by high-resolution transmission electron microscopy, and the modification of electronic properties of nanotubes as result of filling their channels with chosen substances was investigated by Raman spectroscopy and X-ray photoelectron spectroscopy. It was shown that the electronic properties of filled SWCNTs depend on the chemical nature of incorporated materials. The encapsulation of TmCl₃ and GaSe into the carbon nanotube channels leads to acceptor doping of the SWCNTs, and this effect is more prominent for thulium chloride. The incorporation of bismuth telluride into the nanotube cavities does not result in any modification of their electronic properties. The filling of the nanotube channels with silver leads to donor doping of the single-walled carbon nanotubes.     

Surface enhanced Raman scattering and photoluminescence properties of catalytic grown ZnO nanostructures

Sword-like (diameter ranging from 40 nm to 300 nm) and needle-like zinc oxide (ZnO) nanostructures (average tip diameter ∼40 nm) were synthesized on annealed silver template over silicon substrate and directly on silicon wafer, respectively via thermal evaporation of metallic zinc followed by a thermal annealing in air. The surface morphology, microstructure, chemical analysis and optical properties of the grown samples were investigated by field emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis, room temperature photoluminescence and Raman spectroscopy. The sword-like ZnO nanostructures grown on annealed silver template are of high optical quality compared to needle-like ZnO nanorods for UV emission and show enhanced Raman scattering.     

Synthesis and characterization of CdS nanoparticle based multiwall carbon nanotube–maleic anhydride–1-octene nanocomposites

CdS nanoparticles were synthesized by sonication from cadmium chloride and thiourea using a multiwall carbon nanotube (MWCNT)–maleic anhydride (MA)–1-octene system as the matrix. The matrix was obtained by the “grafting from” approach from oxidized carbon nanotubes and maleic anhydride–1-octene. Multiwall carbon nanotubes used for reinforcing the matrix were synthesized by Catalytic Chemical Vapor Deposition using Fe–Co/Al₂O₃ as the catalyst. The obtained nanostructures were characterized by FTIR, XRD, Raman spectroscopy, TEM, SEM and UV–vis spectroscopy. The average CdS particle diameter was 7.9 nm as confirmed independently by TEM and XRD. UV–vis spectroscopy revealed that the obtained nanostructure is an appropriate base material for making optical devices. The novelty of this work is the use of the MWCNT–MA–1-octene matrix obtained via the “grafting from” approach for the synthesis of uniformly dispersed CdS nanocrystals by ultrasonic cavitation to obtain a polymer nanocomposite.     

High-resolution near-field Raman microscopy of single-walled carbon nanotubes

We present near-field Raman spectroscopy and imaging of single isolated single-walled carbon nanotubes with a spatial resolution of approximately 25 nm. The near-field origin of the image contrast is confirmed by the measured dependence of the Raman scattering signal on tip-sample distance and the unique polarization properties. The method is used to study local variations in the Raman spectrum along a single single-walled carbon nanotube.     

The growth of carbon nanotubes on montmorillonite and zeolite (clinoptilolite)

Synthesis of carbon nanotubes described in the present work is based on activation of methane in a hot filament CVD reactor and subsequent creation of nanostructures on a catalyst pre-treated polished surface of silicon. An essential step of the synthesis is the use of natural minerals as catalysts. We have studied the catalyst parameters, the way of its application and the amount of Fe³⁺ cations on the surface of aluminosilicates on the quality of the grown nanotube layers. The growth of carbon nanotubes catalyzed by montmorillonite and zeolite (clinoptilolite) was confirmed by scanning electron microscopy and Raman spectroscopy.     

Microscopic model of the optical absorption of carbon nanotubes functionalized with molecular spiropyran photoswitches

The adsorption of molecules to the surface of carbon nanostructures opens a new field of hybrid systems with distinct and controllable properties. We present a microscopic study of the optical absorption in carbon nanotubes functionalized with molecular spiropyran photoswitches. The switching process induces a change in the dipole moment leading to a significant coupling to the charge carriers in the nanotube. As a result, the absorption spectra of functionalized tubes reveal a considerable redshift of transition energies depending on the switching state of the spiropyran molecule. Our results suggest that carbon nanotubes are excellent substrates for the optical readout of spiropyran-based molecular switches. The gained insights can be applied to other noncovalently functionalized one-dimensional nanostructures in an externally induced dipole field.     

Raman spectroscopy of carbon nanotubes

The use of Raman spectroscopy to reveal the remarkable structure and the unusual electronic and phonon properties of single wall carbon nanotubes (SWNTs) is reviewed comprehensively. The various types of Raman scattering processes relevant to carbon nanotubes are reviewed, and the theoretical foundations for these topics are presented. The most common experimental techniques used to probe carbon nanotubes are summarized, followed by a review of the novel experimental findings for each of the features in the first order and second order Raman spectra for single wall carbon nanotubes. These results are presented and discussed in connection with theoretical considerations. Raman spectra for bundles of SWNTs, for SWNTs surrounded by various common wrapping agents, and for isolated SWNTs at the single nanotube level are reviewed. Some of the current research challenges facing the field are briefly summarized.