Raman光谱(拉曼光谱)第四章4-2-左健-理化中心.ppt

1、(surface enhanced Raman spectroscopy),SERS,Raman spectroscopy: high characteristic good spatial resolution (micro Raman) minimal sample preparation all solvents can be used but: biological samples often show high fluorescence biological molecules appear often at low concentration level,Why SERS spec

2、troscopy?,SERS quenches fluorescence,essential oil,Raman,silver colloids,SERS improves the detection limit: Adenine,How does SERS work? The SERS EM enhancement,metal colloid,excitation,detection,SERS,molecule,SERS EM enhancement shape effect,SERS: Excitation of plasmon resonances in Ag (Au or Cu) na

3、noparticles Raman spectroscopy utilizes optical properties of nanostructures,Wavelength nm,SCS nm,J. Kottmann et al., IFH Field Theory Group, ETH Zrich,Ag, Au or Cu,Wavelength/nm,Scattering Cross section,Field enhancement,SERS: Raman spectroscopy utilizes optical properties of nanostructures,J. Kott

4、mann et al., IFH Field Theory Group, ETH Zrich,Wavelength nm,SCS nm,*10,SERS EM enhancement shape effect,Scattering Cross section,Wavelength/nm,Field enhancement,SERS: Raman spectroscopy utilizes optical properties of nanostructures,20 nm,J. Kottmann et al., IFH Field Theory Group, ETH Zrich,Ag, Au

5、or Cu,SERS EM enhancement aggregation effect,Scattering Cross section,Wavelength/nm,Typical SERS media,不同形状金纳米粒子的表面增强拉曼光谱,自组装好的不同形状的金纳米粒子的硅片浸没在20mM NaSCn 的溶液里,取出后测量其SERS信号,以SCN - 作为探针分子,绿光(51415nm) 作为激发光波长得到的SERS谱图,具有较高SERS 活性的粗糙铂电极的STM (a) 和镍纳米线阵列的A FM (b) 图像,各种过渡金属表面上吸附的吡啶在最强峰电位下的表面增强拉曼谱图,Near-fie

6、ld Raman spectroscopy,Near-Field Microscopy,Rayleigh Limit,Near-field resolution,Near-Field Geometries,Schematic Near-Field Microscope Set-up,L. Novotny and C. Hafner, Phys. Rev. E 50 (1994).,Light at Small Apertures,Aluminum,Near-field Apertures,pulled etched/old etched/new,Investigation of Liquid-

7、Liquid Interfaces,NF Raman studies of water-carbon-tetrachloride interface,Raman intensity of water stretching vibration vs. the distance covered by the piezo translator,NF Raman studies of water-carbon-tetrachloride interface,Raman spectral shift of water stretching vibration vs the distance covere

8、d by the piezo translator,Investigation of Chemical Reactions using NF-Raman,Heterogeneous Catalysis,Heterogenous Catalysis,Correlation of Topography and Spectra,Topography,C. Fokas and V. Deckert, Appl. Spectrosc. 56, 192 (2002),TERS - Tip Enhanced Raman Spectroscopy,Sample,Single SERS active particle,A