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单壁碳纳米管束针尖增强近场拉曼光谱探测实验研究 总被引:2,自引:0,他引:2
针尖增强近场拉曼光谱术是最近发展起来的光谱技术。金属探针在获得样品纳米局域表面形貌的同时,受激光激发,在针尖附近产生增强电磁场,得到与形貌位置精确对应的针尖增强局域拉曼光谱,形貌和光谱的结合实现了纳米局域的光谱指认。文章建立了一套针尖增强近场拉曼光谱测量装置,并用此装置对电弧法合成的单壁碳纳米管进行了近场拉曼光谱探测。测量了直径为100 nm单壁碳纳米管束的针尖增强拉曼光谱,进一步得到至多3根单壁碳纳米管的近场拉曼光谱,实现了超衍射分辨光谱探测。通过与远场拉曼光谱比较发现,针尖增强近场拉曼光谱的增强因子大于230倍。实验证明,同时具有超衍射空间分辨和拉曼光谱信号增强能力的针尖增强近场拉曼光谱术将是纳米材料和纳米结构表征的一种重要方法。 相似文献
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提出一个根据拉曼基频模及其倍频模的斯托克斯和反斯托克斯拉曼成分的不同共振行为来探测样品与激光共振的系统能级的方法.此方法被应用到不均匀单壁碳纳米管束样品中某一径向呼吸模频率为219波数的金属型碳纳米管.通过分析呼吸模及其倍频模和切向模的共振行为,获得了该碳纳米管的电子跃迁能量,并获得纳米管C-C最近邻重叠积分因子为2.80 eV.此数值可以很好的解释单壁碳纳米管径向呼吸模的共振行为.
关键词:
单壁碳纳米管
呼吸模
共振拉曼散射
电子跃迁能 相似文献
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单壁碳纳米管吸附对三联苯的研究 总被引:1,自引:1,他引:0
利用对三联苯对单壁碳纳米管进行了化学修饰,并利用透射电镜、紫外可见吸收光谱、拉曼光谱对修饰后的单壁碳纳米管进行了表征分析.通过对比吸附前后的紫外可见吸收光谱发现,吸附后的光谱强度大约下降63.1%,说明单壁碳纳米管吸附上了对三联苯.通过拉曼光谱分析发现,吸附后单壁碳纳米管的拉曼光谱中主要峰的位置向长波方向移动了6~7 cm-1,认为拉曼光谱发生移动的原因是单壁碳纳米管吸附对三联苯前后状态的改变导致的. 相似文献
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用紧束缚法研究了单壁碳纳米管在轴向磁场下费米能级附近电子性质的变化规律.研究发现:能隙随轴向磁场变化的快慢及磁致能隙峰值都与碳纳米管直径有着紧密联系;对于相同直径的碳纳米管,金属性管的磁致能隙峰值最大.具体计算了锯齿型碳纳米管费米能级附近电子态密度随轴向磁场的变化关系,发现所有碳纳米管的电子态密度和能隙变化都体现出周期性.磁场使得碳纳米管发生绝缘体-金属周期性相转变的根本原因是由于在磁场的作用下范霍夫奇异点出现分裂-移动-融合的周期性变化.
关键词:
磁场
碳纳米管
紧束缚法
范霍夫奇异点 相似文献
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采用气相扩散方法将C60分子填充到单壁碳纳米管(SWNTs)中,制备出高填充比率的豆荚形纳米材料C60@SWNT,又称为peapod.用金刚石对顶砧(DAC)装置获得高压,在高压下同时利用紫外激光处理样品,通过激光和压力的共同作用研究了C60分子在碳管内的聚合相变.在21.5GPa高压下,同时紫外激光(325nm)照射30min后,拉曼光谱表明C60分子在碳管内发生了聚合,形成一维链状O相聚合结构,且该相变是不可逆的.
关键词:
60 peapod')" href="#">C60 peapod
紫外激光
高压
拉曼光谱 相似文献
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Single-walled carbon nanotubes (SWNTs) of 0.4 nm in diameter are produced inside channels of microporous zeolite single crystals. Three possible structures: (5,0), (4,2), and (3,3) contribute to three bands at 1.37, 2.1, and 3.1 eV in optical absorption spectra. The direct correspondence between chiralities and absorption bands is identified by density functional calculations. The resonant Raman spectrum shows the features that can be assigned to van Have singularities in calculated phonon density of states. In the low-frequency region, two peaks at 510 and 550 cm-1 are attributed to the radial breathing modes (RBMs) of the (5,0) and (4,2) tubes. After removing the zeolite framework, the RBM frequencies downshift by 10 cm-1. The charge-transfer behavior in lithium-doped 0.4-nm SWNTs is investigated. The Raman peak at 1558 cm-1 couples with the electronic continuum, and shows a Breit–Wigner–Fano line shape. PACS 78.67.Ch; 73.22.-f; 82.75.Mj; 63.22.+m; 71.20.Tx 相似文献
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Synthesis of single-wall carbon nanotubes (SWNTs) was carried out by an ablation method using a XeCl excimer laser. It was irradiated onto a graphite target containing Co and Ni at the temperatures of 1073, 1173, 1273, 1373, 1473, 1523 and 1623 K under the atmosphere (0.1 MPa) of Ar gas with the flow rate of 12 ml/min. The measurement by a scanning/transmission electron microscope and Raman spectroscopy found the formation of SWNTs with the diameter of about 1.3 nm and the length of about 2 μm in ablated carbonaceous soot. The ratio of peak intensity of 1590 cm−1 (G band) to that of 1335 cm−1 (D band) in the high frequency Raman spectra increased with increasing the ambient temperature. The radial breathing mode (RBM) in the low frequency Raman spectra shows that the mean diameter of SWNTs increased with increasing the ambient temperature. 相似文献
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Ioan Baltog Mihaela Baibarac Serge Lefrant Jean Yves Mevellec 《Journal of Raman spectroscopy : JRS》2011,42(3):303-312
The capability of anti‐Stokes/Stokes Raman spectroscopy to evaluate chemical interactions at the interface of a conducting polymer/carbon nanotubes is demonstrated. Electrochemical polymerisation of the monomer 3,4‐ethylenedioxythiophene (EDOT) on a Au support covered with a single‐walled carbon nanotube (SWNT) film immersed in a LiClO4/CH3CN solution was carried out. At the resonant optical excitation, which occurs when the energy of the exciting light coincides with the energy of an electronic transition, poly(3,4‐ethylenedioxythiophene) (PEDOT) deposited electrochemically as a thin film of nanometric thickness on a rough Au support presents an abnormally intense anti‐Stokes Raman spectrum. The additional increase in Raman intensity in the anti‐Stokes branch observed when PEDOT is deposited on SWNTs is interpreted as resulting from the excitation of plasmons in the metallic nanotubes. A covalent functionalisation of SWNTs with PEDOT both in un‐doped and doped states takes place when the electropolymerisation of EDOT, with stopping at +1.6 V versus Ag/Ag+, is performed on a SWNT film deposited on a Au plate. The presence of PEDOT covalently functionalised SWNTs is rationalised by (1) a downshift by a few wavenumbers of the polymer Raman line associated with the symmetric C C stretching mode and (2) an upshift of the radial breathing modes of SWNTs, both variations revealing an interaction between SWNTs and the conjugated polymer. Raman studies performed at different excitation wavelengths indicate that the resonant optical excitation is the key condition to observe the abnormal anti‐Stokes Raman effect. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Meyer JC Paillet M Michel T Moréac A Neumann A Duesberg GS Roth S Sauvajol JL 《Physical review letters》2005,95(21):217401
Using electron diffraction on freestanding single-walled carbon nanotubes, we have determined the structural indices (n,m) of tubes in the diameter range from 1.4 to 3 nm. On the same freestanding tubes, we have recorded Raman spectra of the tangential modes and the radial breathing mode. For the smaller diameters (1.4-1.7 nm), these measurements confirm previously established radial breathing mode frequency versus diameter relations and would be consistent with the theoretically predicted proportionality to the inverse diameter. However, for extending the relation to larger diameters, either a yet unexplained environmental constant has to be assumed, or the linear relation has to be abandoned. 相似文献
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V. N. Bezmel’nitsyn A. G. Domantovskii A. V. Eletskii E. V. Obraztsova A. G. Pernbaum K. E. Prikhod’ko S. V. Terekhov 《Physics of the Solid State》2002,44(4):656-658
The high-yield synthesis of single-walled carbon nanotubes (SWNTs) is carried out in an electric-arc discharge using the Ni-Cr alloy as a catalyst. A new method of introducing the catalyst into the plasma hot region is used in the synthesis. In this method, the anode with a sandwich structure consists of two longitudinal graphite rods of a rectangular cross section, between which the Ni-Cr alloy in the form of a foil having a thickness approximately equal to 0.2 mm is placed. The obtained samples are investigated using transmission electron microscopy (TEM), Raman spectroscopy, and thermogravimetry. According to the results of TEM observations, SWNTs are tied into bundles with a length of several micrometers and a diameter of about 10 nm. The Raman spectra indicate that the diameter distribution of SWNTs lies between 1.2 and 1.5 nm with a peak at approximately 1.24 nm. The SWNT content in the obtained samples is approximately 20%. Heat treatment at various temperatures with a dosed air supply leads to a noticeable mass loss of the sample and to a change in its composition. For example, thus heating to 600 K causes a mass loss of about 40%, leading to an increase in the content of SWNTs up to 35% without their noticeable destruction. Further heating above 600 K leads to a virtually complete thermal decomposition of SWNTs. 相似文献
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Jorio A Pimenta MA Souza Filho AG Samsonidze GG Swan AK Unlü MS Goldberg BB Saito R Dresselhaus G Dresselhaus MS 《Physical review letters》2003,90(10):107403
Resonance Raman studies on single wall carbon nanotubes (SWNTs) show that resonance with cross polarized light, i.e., with the E(mu,mu+/-1) van Hove singularities in the joint density of states needs to be taken into account when analyzing the Raman and optical absorption spectra from isolated SWNTs. This study is performed by analyzing the polarization, laser energy, and diameter dependence of two Raman features, the tangential modes (G band) and a second-order mode (G' band), at the isolated SWNT level. 相似文献
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碳纳米管晶格振动模及拉曼光谱的研究进展 总被引:7,自引:0,他引:7
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 相似文献
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A detailed theoretical study of the phonon and thermal properties of achiral single wall carbon nanotubes has been carried out using force constant model considering up to third nearest-neighbor interactions. We have calculated the phonon dispersions, density of states, radial breathing modes (RBM) and the specific heats for various zigzag and armchair nanotubes, with radii ranging from 2.8 Å to 11.0 Å. A comparative study of phonon spectrum with measured Raman data reveals that the number of Raman active modes for a tube does not depend on the number of atoms present in the unit cell but on its chirality. Calculated phonon modes at the zone center more or less accurately predicted the Raman active modes. The radial breathing mode is of particular interest as for a specific radius of a nanotube it is found to be independent of its chirality. We have also calculated the variation of RBM and G-band modes for tubes of different radii. RBM shows an inverse dependence on the radius of the tube. Finally, the values of specific heat are calculated for various nanotubes at room temperature and it was found that the specific heat shows an exponential dependence on the diameter of the tube. 相似文献