低温下单壁碳纳米管拉曼光谱温度效应研究

在单壁碳纳米管的低温拉曼光谱测量过程中,发现径向呼吸模(RBM)和正切拉伸模(GM)的拉曼频移在低温下的温度效应和在高温时的温度效应存在着很大的区别,在低温下拉曼光谱的频移和温度并不呈线性关系。而且,在温度为210K时,单壁碳纳米管内部的振动结构可能发生了变化。在低温下单壁碳纳米管拉曼峰的强度的变化是不可逆的。     

Observing the Stimulated Raman Gain Spectra of Solutions Using an Infrared Pump Pulse with Narrow Linewidth and a Low-Noise CW Probe Laser

Stimulated Raman gain (SRG) spectroscopy using infrared pump pulses with narrow linewidth and a low-noise cw probe infrared laser was proposed. High-resolution Raman spectra of solutions were obtained. The SRG spectra of crystal GaP, benzene, and toluene were measured to confirm the spectral resolution and sensitivity over the terahertz (THz) region. We discuss the polarization dependence of the spectral measurement of carbon tetrachloride. Our system can detect organic molecules in aqueous solutions.     

Quantitative analysis of sugar composition in honey using 532‐nm excitation Raman and Raman optical activity spectra

Raman spectroscopy based on the 1064‐nm laser excitation was suggested as a handy non‐invasive technique allowing to quickly determine sugar content in honey and similar food products. In the present study, the green 532‐nm laser radiation is explored instead as it provides higher‐quality spectra in a shorter time. The sample fluorescence was quenched by purification with activated carbon. For control mixture decomposition of Raman spectra to standard subspectra led to a typical error of the sugar content of 3%. Raman optical activity (ROA) spectra that could be measured at the shorter excitation wavelength as well provided a lower accuracy (~8%) than the Raman spectra because of instrumental sensitivity and noise limitations. The results show that Raman spectroscopy provides elegant and reliable means for fast analyses of sugar‐based food products. Copyright © 2016 John Wiley & Sons, Ltd.     

不同激发波长下单壁碳纳米管与多壁碳纳米管的拉曼光谱比较

对不同激发波长下单壁和多壁碳纳米管的激光拉曼光谱进行了比较。发现单壁碳纳米管D峰强度和G峰强度的比值(ID/IG)几乎不随激发光子能量的改变而变化,多壁碳纳米管ID/IG值随着激发光子能量的增加以斜率0 3/eV减小。并对此现象进行了初步的分析。此外,还发现在1064nm激发波长下,单壁和多壁碳纳米管2500-3500cm-1之间拉曼峰的相对强度随着入射激光功率的增加而增加。     

Continuum generation in water and carbon tetrachloride using a picosecond Nd-YAG laser pulse

We have measured the continuum generated in two non-linear media, distilled water and carbon tetrachloride, pumped by a 36 ps Neodymium Yttrium Aluminium Garnet laser pulse operating at 1.06 μm. We show that the induced spectral broadening extends from 400 nm to 850 nm in both media. However, we find that continuum spectra of carbon tetrachloride exhibit an oscillatory structure with an energy range of about 445 cm⁻¹ which corresponds to the fundamental Raman component. This behaviour is due to a spectral non-overlapping of the Raman anti-Stokes components photoinduced in this medium.     

Temperature dependence of the raman spectra of carbon nanotubes with 1064 nm excitation

In this report, the near infrared 1064 nm line of an Nd:YAG laser, which has strong thermal effect, was used as the excitation. A temperature dependence of the Raman spectra of carbon nanotubes was observed at different temperatures by varying the incident laser power. The results show that the relative Raman intensities to the tangential stretching mode (G mode) of the higher-order Raman modes within 2500–3500 cm⁻¹ increase with increasing excitation laser power at the sample and the changes in the relative Raman intensities are linear in the excitation laser power. This has not been reported elsewhere. Thorough analysis shows that this is a temperature dependence of double-phonon Raman scattering and maybe provide important information for the studying of CNTs and double-phonon Raman scattering.     

PAN基碳纤维在表面处理中的拉曼光谱研究

采用激光拉曼光谱研究了PAN基碳纤维在表面处理中的微结构变化,分析了表面处理前后碳纤维的一级拉曼光谱特性。结果表明：拉曼光谱中主要的D峰和G峰的拉曼频移、半高宽以及各个不同拉曼频移位置对应肩峰的积分面积比是表征碳纤维物相结构变化的重要参数。经过不同的表面处理,PAN基碳纤维的一级拉曼光谱参数发生了一定程度变化,D峰和G峰的拉曼峰位向高波数偏移,表征石墨微晶尺寸的R值有所提高,这说明在表面处理后碳纤维的石墨微结构受到刻蚀,微晶尺寸有所减小,石墨微晶的边界活性增大;此外,表征碳纤维结构有序程度和缺陷多少的D峰和G峰的半高宽均有减小,表征无定型碳结构或某种有机官能团的A峰和D″峰的相对积分面积减小,这说明与乱层石墨结构相比,碳纤维中存在的无定型碳结构更容易被刻蚀,经过表面处理之后无定型碳的物相比例减小,这与碳纤维XRD图谱中表观结晶度提高的规律相一致。因此,利用激光拉曼光谱可研究碳纤维物相结构的变化规律。     

Surface-enhanced Raman spectroscopy of hexabenzobenzene,C24H12, an analogue of a graphene nanostructure

While large scale fabrication of graphene nanoribbons remains a challenge, there exist materials which can be fabricated in quantities such as hexabenzobenzene,HBZB, (C₂₄H₁₂) and which have a two-dimensional (2D) carbon structure similar to graphene nanostructures. Using a 632 nm laser, no Raman spectra could be obtained from the solid material because of a strong luminescence produced by the laser. However, surface-enhanced Raman spectroscopy enabled the measurement of some of the Raman active modes. The G and D modes, which are characteristic fingerprints of a 2D graphene structure, were observed at 1331 and 1600 cm^?1, respectively. Density functional theory at the B3LYP/6-31G^* level was used to calculate the minimum energy structure and the Raman active vibrational frequencies of HBZB. The calculated minimum energy structure was 2D having D_6h symmetry in agreement with the experimental structure in the liquid phase. The calculated frequencies were in good agreement with the measured values.     

光镊拉曼光谱法分析红法夫酵母内虾青素含量

建立一种用激光镊子拉曼光谱法快速定量红法夫酵母细胞内虾青素含量的方法。测定不同浓度虾青素标准品溶液的拉曼光谱,取其1 520cm-1峰峰高绘制虾青素标准曲线;取不同氮源、碳源的红法夫酵母细胞,一部分用激光镊子拉曼光谱法测定,一部分用紫外-可见分光光度法测定;最后分析两者间的相关性。结果表明虾青素标准曲线的相关系数到达0.998 3。在单位质量红法夫酵母虾青素含量与单位体积红法夫酵母发酵液虾青素产量方面,对比激光镊子拉曼光谱法与紫外-可见分光光度法,两种方法所得数据具有良好的相关性,其相关系数分别达到0.917 7和0.905 4,表明激光镊子拉曼光谱法能够达到紫外-可见分光光度法的测定效果,是定量分析红法夫酵母细胞内虾青素的更有效方法。     

丙氨酸对映体单晶的变温偏振激光拉曼光谱研究

本文测量了在不同偏振状态下 ,D 和L 丙氨酸的变温拉曼光谱。我们发现 :1 丙氨酸对映体的非偏振拉曼光谱图极其相似。 2 着重研究了D 丙氨酸偏振拉曼光谱随温度变化的特点。 3 通过拉曼光谱的手段 ,我们未发现A Salam所预言的在 2 5 0K左右从D 丙氨酸→丙氨酸的二级相变。     

Raman spectroscopy based on a single-crystal sapphire fiber

We demonstrate the advantages of using a single-crystal sapphire fiber to perform Raman spectroscopy over using a standard glass fiber. The narrow Raman peaks and the low background signal of a single-crystal sapphire fiber allow for the detection of weaker Raman signals or Raman signals much closer to the incident laser wavelength than with a standard glass fiber, which has a strong broadband Raman spectrum of its own. The Raman spectra of calcite, single-walled carbon nanotubes, and aqueous sodium carbonate solution were collected using a 50 cm long, 200 μm diameter sapphire fiber, and then they were compared with the results using a 50 cm long, 100 μm diameter glass fiber. The Raman spectrum of each tested material becomes indistinguishable due to the background Raman signal of the glass fiber but can easily be seen using the sapphire fiber, which has only a few narrow Raman peaks of its own.     

碳纳米管的拉曼光谱及其温度效应

在室温下首次观察到碳纳米管的四级拉曼光谱，并且发现碳纳米管的Ｄ峰和Ｄ＊峰的斯托克斯线和反斯托克斯线频率不一致。此外，还发现碳纳米管的拉曼特征峰频率严重依赖样品的温度，随着温度增加，碳纳米管拉曼特征峰频率下移，频移与温度变化成线性关系。     

Resonance Raman spectra of carbon nanotubes by cross-polarized light

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.     

Laser heating method for estimation of carbon nanotube purity

A new method of a carbon nanotube purity estimation has been developed on the basis of Raman spectroscopy. The spectra of carbon soot containing different amounts of nanotubes were registered under heating from a probing laser beam with a step-by-step increased power density. The material temperature in the laser spot was estimated from a position of the tangential Raman mode demonstrating a linear thermal shift (-0.012 cm^-1/K) from the position 1592 cm^-1 (at room temperature). The rate of the material temperature rise versus the laser power density (determining the slope of a corresponding graph) appeared to correlate strongly with the nanotube content in the soot. The influence of the experimental conditions on the slope value has been excluded via a simultaneous measurement of a reference sample with a high nanotube content (95 vol. %). After the calibration (done by a comparison of the Raman and the transmission electron microscopy data for the nanotube percentage in the same samples) the Raman-based method is able to provide a quantitative purity estimation for any nanotube-containing material. Received: 11 December 2001 / Accepted: 12 December 2001 / Published online: 4 March 2002     

碳纳米管拉曼光谱的温度效应

碳纳米管拉曼光谱的温度效应黄福敏１余国滔２谭平恒１张树霖１（北京大学物理系１和生命科学院２北京１００８７１）施祖进周锡煌顾镇南（北京大学化学与分子工程学院北京１００８７１）ＴｅｍｐｅｒａｔｕｒｅＥｆｆｅｃｔｏｆｔｈｅＲａｍａｎＳｐｅｃｔｒａｏｆＣａｒ...     

a-C:N:H纳米尖端荧光产生的机理

用CH4,H2和NH3为反应气体,利用等离子体增强热丝化学气相沉积在沉积有碳膜的Si衬底上制备了a-C:N:H纳米尖端,并用扫描电子显微镜和微区Raman光谱仪对碳膜和纳米尖端进行了表征。结果表明:Raman谱中含有与碳和氮相关的峰,且纳米尖端的Raman谱比碳膜的Raman谱有很强的荧光背景。Raman谱中的峰说明沉积的碳膜和纳米尖端是a-C:N:H薄膜和a-C:N:H尖端。a-C:N:H纳米尖端的Raman谱中强荧光背景的产生表明其在激发光源照射的过程中发射了强荧光,对a-C:N:H纳米尖端产生强荧光的机理进行了探讨。     

Raman and X‐ray diffraction analysis on unburned carbon powder refined from fly ash

The bonding and crystalline structures of oil‐fried fly ash collected from a power plant were analyzed by using Raman spectroscopy and X‐ray diffraction (XRD), respectively. These carbon powders underwent a series of annealing treatment for graphitization and crystallization. In Raman spectra, the refined, unburned carbon contains clearly the D, G and D′ peaks under 2000 or 2700 °C treatment. The Raman spectral line shape of refined, unburned carbon heated at 2700 °C is similar to that of commercial graphite made from graphitization process. In the XRD spectra, the refined, unburned carbon contains (002), (100) and (004) diffraction peaks under heating at 2000 or 2700 °C. The XRD spectral line shape of refined, unburned carbon heated at 2700 °C is similar to that of a commercial graphite bar. The quantitative graphitization level from Raman spectra and crystallization degree from XRD spectra on refined, unburned carbon powders serve as preliminary guide for the qualitative evaluation of these unburned carbon powders. Copyright © 2009 John Wiley & Sons, Ltd.     

激光轰击过程中纳米碳管复合光限幅材料组成及结构的演变研究

光限幅材料在激光轰击过程中的稳定性将在很大程度上决定其实用化价值。文章采用红外(IR)光谱、拉曼(Raman)光谱、透射电子显微镜(TEM)及孔结构分析等测试方法对纳米碳管(CNTs)复合光限幅材料在激光轰击过程中组成、结构的演变进行跟踪研究。结果表明,在强激光轰击下,复合体系中二氧化硅(SiO₂)基质的组成未发生显著改变且网络结构趋于完整,具有较好的稳定性。掺杂CNTs石墨化程度提高,SiO₂凝胶玻璃基质对其起一定的保护作用。轰击过程产生的热效应使得SiO₂颗粒长大,由其堆积而成的孔随之增大。     

Pure component Raman spectral reconstruction from glazed and unglazed Yuan,Ming, and Qing shards: a combined Raman microscopy and BTEM study

Raman mapping measurements were performed on the glazed and unglazed surfaces of shards excavated from Yuan, Ming, and Qing dynasty strata. A number of areas on each surface were chosen. Circa 21 × 21 pixels were measured for each area using both 514 and 785‐nm laser as the Raman excitation. Data were collected from 100–3600 cm⁻¹. Many sets of spectra exhibited very intense fluorescence. In spite of the intense fluorescence, the resulting sets of spectra were collated and analyzed together using the band‐target entropy minimization (BTEM) algorithm. Pure component spectral estimates of many of the major components were achieved, without the use of any a priori information such as spectral libraries. These include α‐silica quartz, carbon, anatase, cobalt oxides, hematite, glassy silicate, and lanthanide complexes. In addition, two further unidentified pure component spectra A and B were recovered as well as an interference pattern due to the microscopic texture of the shards (associated with small particle/thin layer domains). The carbon was primarily present in elemental form, i.e. mixture of amorphous and graphitic (unordered and ordered domains); however there is an evidence of some partial oxidation, i.e. formation of carboxylates. The interference patterns and the lanthanide complexes were only observed when using the longer wavelength red laser. The cobalt oxides and the anatase were only observed when using the green laser. In summary, the combination of Raman microscopy and BTEM has allowed the enumeration of many of the underlying spectral patterns present and hence unambiguous identification of the major individual components present in the archaeological samples. This approach would appear applicable to other classes of archaeological materials as well. Limitations and extensions of the present approach are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

外界光对ZnCl2溶液激光拉曼光谱的影响

对ZnCl2溶液在不同外界环境光存在下的激光拉曼光谱的影响进行了探讨.研究表明不同的外界环境光,自然光和室内荧光灯光,都会对拉曼光谱产生干扰效应,存在着特征谱线,倒峰或尖锐正峰.虽干扰表现不同,但都有影响,不能忽略.因此,在进行溶液拉曼光谱检测时,需在暗室或暗罩中进行,以完全隔离外界环境光的影响.