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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,红外和,Raman,光谱学,第一章：红外和,Raman,光谱介绍,什么是红外光谱？什么是,Raman,光谱,红外谱仪和,Raman,谱仪,红外光谱和,Raman,光谱方法的特点,红外光谱和,Raman,光谱研究的基本问题,F Yang,et al. Nature,510, 522-524 (2014),doi:10.1038/nature13434,Characterizations of SWNTs grown at 1,030 C.,红外和,Raman,光谱举例,F Yang,et al. Nature,510, 522-524 (2014),doi:10.1038/nature13434,Characterizations of SWNTs nucleated on catalyst nanoparticles.,Science, 346, 1352(2014),Fig. 4 Various ultrasmooth metallic and metal-graphene nanostructures made by LSI with enhanced electromagnetic and optical properties.,Huang Gao et al. Science 2014;346:1352-1356,Published by AAAS,DG Pearson,et al. Nature,507, 221-224 (2014) doi:10.1038/nature13080,Raman spectra of ringwoodite and walstromite inclusions in,Ju,na diamond JUc29.,R Banerjee,et al. Nature,000, 1-4 (2015),doi:10.1038/nature14160,Reaction of sMMO with O,2,.,(a) Polarized IR spectra of the Azo-PI film with a LPL exposure of 320 J=cm,2,. (b) Polarized IR spectra of the pentacene films on 11 J=cm,2,and 320 J=cm,2,exposed Azo-PI. (c) LPL exposure dependence of DR (A,/,A,) of the Azo-PI films (1370 cm,-1,band) and the pentacene films (905 cm,-1,band). (,Phys. Rev. Lett.,101, 236103 (2008),High-frequency first- and second-order micro-Raman spectra of,n,GL films supported on a SiO2:Si substrate and HOPG,First order-allowed Raman G-band for supported,n,GL films vs number of layers,n,.,Nano Lett,.,6 (,12), 2667(06),JF Li,et al.,Nature,464, 392-395 (2010) doi:10.1038/nature08907,In situ,probing of biological structures by SHINERS.,DG Pearson,et al. Nature,507, 221-224 (2014) doi:10.1038/nature13080,FTIR spectra of ringwoodite inclusion in Ju,na diamond JUc29.,Raman Spectrum of Si (300 K),更全面了解,Raman Spectrum,红外和,Raman,光谱的比较,电磁波波段,红外光波段,红外光谱仪光路示意图,红外和,Raman,光谱测量,红外测量最主要的特点是特殊元件的需要，包括光源、分光元件和光学窗口等。（大多数材料对红外光有强烈的吸收）,光源：钨灯用于近红外、电热棒用于中红外、高压水银弧光灯用于远红外波段。（同步辐射光源）,分光元件,反射式光栅,红外光学窗口和反射式光学元件,红外谱仪中使用的元器件,FT-IR,谱仪基本框图,FT-IR,谱仪的基础,Michelson,干涉仪,单色光,入射，干涉强度的变化,两列单色光,1,、,2,入射，干涉强度的变化,普通光入射后，干涉强度的变化,传统透射式红外谱仪适合中红外波段应用。,FTIR,谱仪更适合在远红外波段应用，但现在也已经普遍应用于中红外波段。,FTIR,使用的光学元件较少，不用狭缝，因此光通量大。此外，测量比较节约时间。,传统红外光谱仪和,FTIR,谱仪特点,红外光谱的测量有很多方法，这些方法可分为：色散法、,FTIR,和非色散法（滤波法）。,非色散法多用于特定的检测。例如用于气体的分析等。优点是方便使用，缺点是参数变动困难。,针对特殊的样品和特殊的需要，有很多特殊的红外测量方法。如光电导法、辐射量热法、光声光谱法、光热光谱法、反射式、内反射式、消逝波式等,其它红外光谱测量方法,反射测量方法,光学常数之间彼此不是独立的，通过一组光学常数的测定可以得到另外的光学常数。而,K-K,关系告诉我们，一组光学常数也不是彼此独立的。,红外内反射测量方,法,光电导测量：样品吸收光导致电导率的变化,量热法：样品吸收光转化为热,1-,辐射量热法,2-,光声光谱法,3-,光热偏转光谱法,光电导方法和量热法,Raman,谱仪,Raman,谱仪结构框图,红外光谱能够得到的信息,分子振动模式,分子振动模式,对称伸缩,Symmetric stretching,反对称伸缩,Asymmetric stretching,剪刀式摆动,Scissoring,左右摇摆,Rocking,上下摇摆,Wagging,扭摆,Twisting,（来源于维基百科）,CH,2,分子团的振动模式,分子振动频率,k,为力常数，决定于化学键的强度。,为折合质量。（同位素效应）,分子振动可以看成谐振子振动，频率为：,=(k/),1/2,红外吸收和,Raman,散射的基本原理,Raman,散射的经典理论,Raman,光谱更适合研究生物分子，因为红外对水特别敏感，不能用水溶液。而,Raman,可以。,共振,Raman,散射对于研究有机分子常常更有优势。,无机材料,Raman,光谱比红外光谱更适宜用于振动谱研究。,特别是很多无机材料溶于水。,各种,Raman,散射,共振,Raman,散射,电子共振,Raman,散射,表面增强,Raman,散射,受激,Raman,散射,超,Raman,散射,逆,Raman,散射,相干反,Stokes Raman,散射（,CARS,）,SERS (Surface Enhanced Raman Scattering),Science, 275, 1102(1997),(A) Unfiltered photograph showing scattered laser light from all particles immobilized on a polylysine-coated surface. (B) Filtered photographs taken from a blank Ag colloid sample (incubated with 1 mM NaCl and no R6G analyte molecules). (C) and (D) Filtered photographs taken from a Ag colloid sample incubated with 2 3 10211 M R6G. These images were selected to show at least one Raman scattering particle. Different areas of the cover slip were rapidly screened, and most fields of view did not contain visible particles. (E) Filtered photograph taken from Ag colloid incubated with 2 3 10210 M R6G. (F) Filtered photograph taken from Ag colloid incubated with 231029MR6G. A high-performance bandpass filter was used to remove the scattered laser light and to pass Stokes-shifted Raman signals from 540 to 580 nm (920 to 2200 cm21). Continuous-wave excitation at 514.5 nm was provided by an Ar ion laser. The total laser power at the sample was 10 mW. Note the color differences between the scattered laser light in (A) and the red-shifted light in (C) through (F).,Direct comparison of laser-induced fluorescence and SERS of a single R6G molecule. Note that single-molecule fluorescence signals were observed as diffraction-limited spots (500 nm in diameter or 6 pixels). The integrated Raman signal appeared much larger in size, but its full width at half maximum was similar to that for fluorescence. Detailed signal intensities and widths are shown for lines (,A,) and (,B,). Laser wavelength, 514.5 nm; excitation power, 10 mW; integration time, 5 s.,CARS,(,相干反,Stokes Raman,散射,),Coherent anti-Stokes Raman scattering is a four-wave mixing process in which a pump beam at frequency,w,p and a Stokes laser beam at frequency,w,s interact with a sample to generate an anti-Stokes signal at frequency,w,as,=,2,w,p,-w,s. The energy diagram of CARS is shown in Fig. 1. The CARS signal is enhanced when the frequency difference between the pump and Stokes beams,w,p-,w,s, is tuned to a vibrational frequency W, providing the vibrational contrast for CARS microscopy.,Left,CARS image of,fibroblast cells,that are stimulated to synthesize lipids. The lipid droplets can be visualized with CARS when tuning to the aliphatic C-H vibration. Image was taken in 2.7 seconds and measures 100 by 100 um.,Right,F-CARS image of a natural single lipid bilayer (erythrocyte ghost) at 2845 cm-1, taken with parallel polarized beams along the x axis (note the polarization dependence). Image size is 15 x 15 um.,红外光谱测量样品准备,金属或者玻璃容器，两端带有红外窗口。,真空和阀控保证气体样品的正确导入。,因为气体吸收一般较弱，光学长程池的应用。,低气压下转动光谱精细结构的分辨。,气体样品：,液体样品：,液体：,带有红外窗口的吸收池；液膜法,如滴入两片,NaCl,平板之间制样。,溶液：,对于溶液样品来说，红外测量是个需要仔细考虑问题，因为多数常用的溶剂都吸收红外光，因此只能根据波段选择溶剂。,较好的溶剂有,CCl,4, CS,2,氯仿等，红外不激活。,水肯定不是好的溶剂。吸收和溶解光学窗口,晶体样品：,大块晶体样品只要适当切割成合适的薄片就可以。厚度的选择取决于材料的吸收系数。表面粗糙度小于红外光波长。,粉末样品：,直接压片：首先要经过较好研磨，粒度小于红外光波长。,混入有机液体涂片（如,NaCl,片）,KBr,压片：,KBr,是常用的压片辅助剂，因为到,25,微米它仍然有很好的红外的通过率。,固体样品：,薄膜样品：,要选择合适的衬底。普通玻璃不是合适的衬底，而,c-Si, c-Ge,是就是比较好的衬底（到,10,微米左右），,NaCl,是更好的选择。,对于薄膜样品有时要故意进行表面粗糙处理，让衬底，同时也是让薄膜不要产生等厚干涉。两个相邻干涉极大值位置满足下式。,薄膜的透过率曲线 ，从中可以看到等厚干涉条纹,Raman,光谱测量样品准备,一般来说气体的,Raman,散射非常困难得到。需要强的激发和灵敏的探测。,相应的样品池的准备同红外，但不同的是不需要红外窗口。,气体样品：,液体样品：,液体：,样品池（同样不需要红外窗口，只要光学窗口就可以），一般采用,90,散射配置。,溶液：,有机溶液和水溶液都可以，根据需要选择。,晶体样品：,最好有光学平面，越是光滑的平面越有利于,Raman,光谱的测量。（,SERS,除外）,粉末样品：,微区,Raman,光谱仪可以容许直接做数微米大小的样品。当然，压片和涂片也是常见的做法。,固体样品：,Raman,散射一个重要的实验技术是抑制荧光背底。,方法：,光滑的平面、改变激发波长等。,荧光背底的抑制,
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