显微共焦拉曼光谱 PPT

水拉曼特征峰随NaCl 浓度变化趋势图,曲线A, B,C,D , E,F的盐度分别 为:0.05 ,0.20 ,0.50 ,1.00 ,2.00 ,5.00mol/ L
W/Si多层膜
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年代估计
Bertoluzza等对28个年代在1750~1940年之
Principle of Confocal Microscopy and Depth Discrimination:
显微共焦拉曼光谱
拉曼光谱是以光子为探针，它对 样品的结构和成分极为敏感并有很强 的特征性,就像人的指纹一样。
特别是显微拉曼光谱可进行空间分 辨、原位无损的光谱分析。
Hale Waihona Puke Baidu
Raman Spectrum of CCl4
435.8 nm
(Hg-line)
anti-Stokes
Stokes
Spectrum taken by Raman in 1929; Resolution ca. 10 cm-1
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
Confocal Raman Microspectroscopy
Making the Microscope Confocal: Introducing an Aperture
Focal length of the lense Effective diameter at the lense
Beam waist of diameter (Gaussian intensity profile)
间的工艺玻璃杯 进行了拉曼光谱分析，仅从
拉曼峰的位置和强度并不能反映出与样品的
年代有什么关系，但发现1080cm-1的拉曼峰
的强度与位于高波数的荧光峰强度的比值与
年代有关。
给出一个经验公式：
y=a+bx x= 年代
y=log(I1080/I荧光) a=-25.384 b=0.013
Why SERS spectroscopy?
Accumulation time: ca. 1 s
从拉曼光谱获取的信息
characteristic Raman peak
changes in frequency of Raman peak
width of Raman peak
polarization of Raman peak
Composition and structure of material
N H2
N
N
N H
N
Raman 10-1 M
SERS
Raman Intensity Raman Intensity
10-2 M 10-3 M
10-5 M 10-6 M
10-7 M
1500
1000
500
Wavenumber / cm-1
10-8 M
1500
1000
500
Wavenumber / cm-1
Typical SERS media
Resonance with electronic states
Virtual state
r
w0 = wir
wir
w0
wStokes
f i
wR
f i
Continuum Resonance Raman Scattering in Iodine Excited with l0 = 488 nm
l0 = 488 nm
Wavenumber/cm-1
TS-1 的紫外共振拉曼光谱
lex=244 nm
Integration of the Microscope and the Spectrometer: Microscope
Microscope + Spectrometer
dispersing element: grating monochromator Baldwin, Batchelder, Webster: “Raman Microscopy: Confocal and Scanning Near-Field“, in: Handbook of Raman Spectroscopy
stress/strain state Crystal size
quality of crystal(crystal size)
crystal (molecule) symmetry and orientation
不同的物质，其拉曼谱是不同的，就象人的指纹 一样，因此拉曼光谱可用于物相的分析与表征。
Focal volume (cylindrical)
Baldwin, Batchelder, Webster: “Raman Microscopy: Confocal and Scanning Near-Field“, in: Handbook of Raman Spectroscopy
Confocal Raman Microspectroscopy
SERS quenches fluorescence
Raman silver colloids
M. x piperita 514.5 nm
Raman Intensity
10 mm
essential oil
2000
1500
1000
500
Wavenumber / cm-1
SERS improves the detection limit: Adenine
Sample Volume: ca. 1 liter
Exposure time: ca. 40 hours
Isotopic (35,37Cl) splitting of n1vibration
461.5-CCl435
455.1-CCl335Cl37
453.4-CCl235Cl237
Spectrum taken with a modern Raman set-up; Resolution ca. 0.5 cm-1 Sample Volume: ca. 1 ml