라만 의 원리와 그의 응용 (Normal,SERS,TERS) 군산대학교 화학과 유수창 기초과학지원연구원, 2012. 11.01 Kunsan National University, Department of Chemistry, Raman Spectroscopy Lab.

Raman and Fraud

Raman vs Infrared Spectra McCreery, R. L., Raman Spectroscopy for Chemical Analysis, 3rd ed., Wiley, New York: 2000

Presentation of Raman Spectra lex = 1064 nm = 9399 cm-1 Breathing mode: 9399 – 992 = 8407 cm-1 Stretching mode: 9399 – 3063 = 6336 cm-1

Resonance Raman Raman signal intensities can be enhanced by resonance by factor of up to 105 => Detection limits 10-6 to 10-8 M. Typically requires tunable laser as light source.

Resonance Raman Spectra lex = 441.6 nm lex = 514.5 nm lex = 1014 nm http://www.photobiology.com/v1/udaltsov/udaltsov.htm

Fluorescence Background in Raman Scattering McCreery, R. L., Raman Spectroscopy for Chemical Analysis, 3rd ed., Wiley, New York: 2000

Applications of Raman Spectroscopy Identification of phases (mineral inclusions, composition of the gas phase inclusions) Anions in the fluid phase (OH-, HS-, etc.) Identification of crystalline polymorphs (Sillimanite, Kyanite, andalusite, etc.) Measurement of mid-range order of solids Measurement of stress High-pressure and High-temperature in situ studies Phase transition and order-disorder transitions in minerals (quartz, graphite) Water content of silicate glasses and minerals Speciation of water in glasses To visit caltech webpage: mineral.gps.caltech.edu Mineral Spectroscopy Server.

Raman Instrumentation

Dispersive and FT-Raman Spectrometry McCreery, R. L., Raman Spectroscopy for Chemical Analysis, 3rd ed., Wiley, New York: 2000

Extremely high spectral resolution by Echelle grating Actual pixels of CCD camera are plotted Spectral resolution: 0.26 1/cm (per pixel) for 473 nm laser For 785 nm laser spectra resolution would be even higher: 0.1 1/cm per pixel Measurement parameters Laser: 473 nm Objective: 100x, 0.95 NA Grating: Echelle ! CCD pixels H shift speed: 32 Exposure time: 1 sec Number of exposures: 15 Si line, 1st order

AFM with 100x 0.7 NA objective in upright configuration – for non-transparent samples Laser deflectometer objective Imaging optics CCD video camera AFM probe Sample XYZ scanner Excitation light Scattered light Beam splitter 2 Beam splitter 1 Probe deflectometer Optical AFM head (100x,0.7 NA objective inside) Laser input&scanning module NA=0.7 400 nm resolution NTEGRA Spectra 19

Combination of AFM with Raman NTEGRA Spectra One object – many techniques Atomic-force microscopy: mechanical, electrical, magnetic properties and nanomanipulations Confocal Raman: imaging and spectroscopy Near-field optical microscopy Confocal fluorescence: imaging and spectroscopy Conventional microscopy and reflected laser confocal imaging Tip Enhanced Raman and Fluorescence microscopy Measurements both in air and liquid NTEGRA Spectra NTEGRA Spectra 20

center of mass position Si nanowire Raman map (main Si band) Optical image Stressed Si Pristine Si _____ 5 µm _____ 5 µm Raman map, Si band center of mass position AFM topography _____ 5 µm _____ 5 µm Fluorescence map Raman map (stressed Si band) _____ 5 µm NT-MDT NTEGRA Spectra + Renishaw Raman microscope

Chemical composition mapping AFM image, Raman spectra and Raman images of single-walled carbon nanotubes. Amorphous carbon is visualized in D-band (1351 cm-1) while well structured nanotubes are present in RBM- band (173 cm-1). Raman images size 5x5 μm. Images courtesy of Dr.Kudryashov, TII, Tokyo, Japan. NTEGRA Spectra 22

Graphene flakes: AFM & Raman microscopy 70x70 µm 4 layers 3 layers 70x70 µm 2 layers Optical image 70x70 µm 4 layers 3 layers 2 layers 1 layer AFM topography 1 layer 2D band center of mass NTEGRA Spectra Data measured: P.Dorozhkin & E. Kuznetsov, NT-MDT 23

Double resonant Raman scattering – Raman spectroscopy of graphene flakes From: Davy Graph et al., 2006 G-band 2D-band 2D band center of mass 4 layers 3 layers G-band intensity 2 layers Double resonant Raman scattering – origin of 2D peak 1 layer NTEGRA Spectra Data measured: P.Dorozhkin & E. Kuznetsov, NT-MDT

Polymer blend 40x40 µm scans AFM topography AFM phase Confocal laser image Raman map (line A – next slide) NTEGRA Spectra Data measured: P. Dorozhkin, NT-MDT 25

Raman spectra and intensity maps of 2 characteristic lines Polymer blend Raman spectra and intensity maps of 2 characteristic lines Line B Line A Line A 40x40 µm scans Line B NTEGRA Spectra Data measured: P. Dorozhkin, NT-MDT 26

Raman Spectroscopy of Graphite

Probing Single Molecules and Single Nanoparticles by Surface-Enhanced RAMAN Scattering SHUMING NIE * and Steven R. Emory Science 21 February 1997: Vol. 275. no. 5303, pp. 1102 - 1106

Figure 2. Tapping-mode AFM images of screened Ag nanoparticles. (A) Large area survey image showing four single nanoparticles. Particles 1 and 2 were highly efficient for Raman enhancement, but particles 3 and 4 (smaller in size) were not. (B) Close-up image of a hot aggregate containing four linearly arranged particles. (C) Close-up image of a rod-shaped hot particle. (D) Close-up image of a faceted hot particle.

Figure 3. Surface-enhanced Raman spectra of R6G obtained with a linearly polarized confocal laser beam from two Ag nanoparticles. The R6G concentration was 2 × 10 -11 M, corresponding to an average of 0.1 analyte molecule per particle. The direction of laser polarization and the expected particle orientation are shown schematically for each spectrum. Laser wavelength, 514.5 nm; laser power, 250 nW; laser focal radius, ~250 nm; integration time, 30 s. All spectra were plotted on the same intensity scale in arbitrary units of the CCD detector readout signal.

Figure 6. 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.  

Tip Enhanced Raman Scattering A route to Raman microscopy with subwavelength spatial resolution and single molecule sensitivity TERS – “inverted” SERS effect (scanning metal tip is a HOT SPOT) Metal AFM probe Enhanced Raman signal 200 nm Electromagnetic field intensity around metal tip Focused laser spot NTEGRA Spectra 34

UPRIGHT geometry (non-transparent samples) Tip Enhanced Raman UPRIGHT geometry (non-transparent samples) TERS collection E TERS excitation 35

TERS- A sensitive Surface Probe

Tip Enhanced Raman Scattering

TERS – SSC in Air

TERS: Carbon deposited on YSZ

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