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Raman Spectroscopy (PowerPoint download)

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					Raman Analyser



   Dr. Shreeram Oak
Basic Principles of Vibrational Spectroscopy




   Inelastic scattering of light at a molecule
                      Raman Principle
When a sample is irradiated with monochromatic light
(e. g. with laser light using discrete lines between 300 and 1064 nm)

Different physical phenomena happen:

1. The main part of the incident light is transmitted without interaction

2. Roughly 10-4 part of the light is elastically scattered
   with no energy absorption --->Rayleigh line

3. A part of the incident light may be absorbed by electronic transitions
   and is emitted as ---> Flourescence

4. Only 10-8 of the incident light is inelastically scattered and interacts
   with the sample .
   The energy is partly absorbed ---> Raman spectrum
    Advantages of FT-Raman compared to FT-IR



•   Little or no sample preparation

• High sensitivity for symmetric molecules, non
  polar bondings and homonuclear chains

• Only low interferences of water and glass
  (measurement of aqueous solutions in
  glass vials)

• Raman lines are usually narrower

• Low frequency information to 50 cm-1
        Simple measurement
1.0           3.0
              2.5
    Raman Intensity
         1.5  0.5
              0.0   2.0                      FT-Raman spectrum of caffeine




                     1800             1600   1400            1200           1000       800              600      400   200
                                                                           Wavenumber cm-1

Coffein durch Standardglaeschen braun.1             Coffein durch Standardglaeschen braun   FT-Raman, RFS100/S               2004/11/12

                                 Blue: measurement of powder inFT-Raman, RFS100/S
Coffein durch Standardglaeschen weiss.0            Coffein durch Standardglaeschen weiss sample cup                          2004/11/12
Coffein.0                   Coffein FT-Raman, RFS100/S                                                                       2004/11/12
                                 Green: measurement in standard laboratory vial
                                 Red: measurement in brown laboratory vial
      FT-Raman Spectroscopy



• Introduced by Hirshfeld and Chase in 1986

• Avoid fluorescence by using near-infrared
  excitation

• Use interferometry instead of dispersive
  methods
              Why FT-Raman Spectroscopy?
              FT-Raman versus dispersive Raman


  • Near-infrared
 excitation instead
     of UV/VIS




  • Interferometry
instead of dispersive
       methods
   Why Near-Infrared Excited Raman
           Spectroscopy?
Fluorescence - a problem of visible excitation




  VIS-Raman       Fluorescence       NIR-Raman
      Fluorescence the Enemy of Raman
0.8
                 Scattering



                    785 nm
0.7




                                                             FT- Raman spectra of
0.6




                                                                  Chocolate
0.5




                                                             top: 785 nm
                                                             bottom: 1064 nm
0.4
0.3
0.2




                                       1064 nm
0.1




      3500   3000   2500    2000         1500   1000   500
                           Wavenumber cm-1
     No Fluorescence of Real World Raman
     Samples with 1064 nm




              Raman spectra of endolithic green algal layer from Antarctica
                      collected using different laser excitations



Courtesy: Prof. Edwards, Univ. Bradford, UK
FT-Raman Spectroscopy: Why?



  • Fluorescence virtually reduced due to
    long wave length excitation at 1064 nm
  • Photochemical degradation is unlikely
Comparison between FT and dispersive
Raman

FT-Raman                       Dispersive Raman


• Fluorescence-free Raman      • Better spatial resolution for
spectra by 1064nm excitation   microscopy applications (down to
                               1µm)

• Simple measurement of bulk
samples due to advantage of    • Higher sensitivity and shorter
sample compartment             measurement times for non-
                               fluorescing samples

• Quantification
                               • Selection of different excitation
                               lines (488-785nm)
100 Rupees banknote
                blue




                       white




 red
100 Rupees Banknote – White area (reference)
and Red colour


                     0.40




                                   Additional peak due to red colour
                     0.35
                     0.30 0.25
             Raman Intensity
         0.15   0.20 0.10
                     0.05




                            3500       3000         2500   2000             1500   1000   500
                                                           Wavenumber cm-1


         100 Rupees - red colour        RFS 100/S                                               2005/11/09


         100 Rupees - white area        RFS 100/S                                               2005/11/09


                                                            Seite 1 von 1
100 Rupees Banknote – white area (reference) and
yellowish colour



                       0.40


                                     Additional peak due to yellowish colour
                       0.35
                       0.30 0.25
               Raman Intensity
           0.15   0.20 0.10
                       0.05




                              3500      3000                2500   2000             1500   1000   500
                                                                   Wavenumber cm-1


           100 Rupees - yellowish colour (100)       RFS 100/S                                          2005/11/09


           100 Rupees - white area       RFS 100/S                                                      2005/11/09


                                                                    Seite 1 von 1
Copy 10 Euro Banknote – White area in
comparison to White area of true banknote


                      0.40




                                                                Differences
                      0.35
                      0.30 0.25
              Raman Intensity
          0.15   0.20 0.10
                      0.05




                             3500   3000                 2500      2000             1500   1000   500
                                                                   Wavenumber cm-1


          100 Rupees - white area        RFS 100/S                                                      2005/11/09


          Copy 100 Rupees - white area       RFS 100/S                                                  2005/11/09


                                                                    Seite 1 von 1




      Paper materials of true and fake bank note differ largely!
                            Summary
-   For the investigated banknotes differences could be found
    between true and simulated fake banknotes
-   Spectral differences may be observed due to differences in the
    paper and due to differences in the ink used for the original and
    the false banknote
-   For the paper different fillers and binders used for true and false
    note can provoke different Raman spectra
    Especially fillers are very often of inorganic nature (e.g. TiO2) and
    yield good Raman spectra
-   Limitations: green and blue colours often show fluorescence even
    with FT-Raman (long wavelength excitation!); further
    fluorescence may be increased for old and often used banknotes
    compared to new ones.
Analyzing cis/trans Isomers with FT-Raman



                  55
                            C-C double bonds
                  50
                  45   40
       RAMAN INTENSITY
       30      35 25
                  20
                  15




                            3000   2500   2000         1500    1000   500
                                            WAVENUMBERS CM-1




                            FT-Raman spectrum of cis (upper)
                               and trans (lower) stilbene
        TLC FT-Raman Accessory


                     • enables mapping of TLC
                       plates or other flat
                       samples

                     • sampling area 75 x 50
                       mm

                     • horizontal arrangement



R 315   X-Y Stage for TLC-FT-Raman
        Spectroscopy
HPTLC-FT-SERS                       HPLC1.HGL




Surface Enhanced Spectra of Hypoxanthine
       (Estimated Sample Amounts)
          Special Sampling Accessories


                Low
                temperature
                accessory




                              Variable
                              Temperature
Heating                       Cell
 Stage
                     Phase transitions of active agent with
                     temperature rise
           0.25




                                                      180°C
           0.20




                                                      170°C
                                                      160°C
   Raman Intensity
             0.15




                                                      150°C
                                                       140°C
                                                      130°C
0.10




                                                        120°C
                                                      100°
                                                      C
                                                      80°C
           0.05




                                                      60°C
                                                        40°C

                 1800      1600   1400    1200           1000      800   600   400
                                                 Wavenumber cm-1

 Sample: Ramprobe S331381 40degree
 Sample: Ramprobe S331381 60degree
 Sample: Ramprobe S331381 80degree
            .... More Accessories




                                    Goniometer

Bottle
holder


    Sample rotator
Well plate accessory
  for FT-Raman
   Spectroscopy


     Advantage:
High sample throughput
HTS-Raman



            Measurement through
            bottom of well plate


            → focus is fixed


            → best reproducibility
                           Forensic Application
Textile tissue contaminated with explosive material
               0.040




                                                                       x
                   0.030
   Raman Intensity
     0.020




                                                SemtexB
               0.010




                                                       Cotton
               0.000




                           3500       3000              2500            2000         1500                        1000   500
                                                                     Wavenumber cm-1


     D:\SM06\RASCOPE\SM06\SemtexB_onTextile_tissue.0       SemtexB_onTextile_tissue        Ramscope III an RFS100,            2006/02/16

                             Red: SemtexB
     D:\SM06\RASCOPE\SM06\Textile_tissue.0    Textile_tissue     Ramscope III an RFS100,                                      2006/02/16

                             Blue: Textle tissue, cotton 1 of 1
                                                       Page
                             Laser; 1064nm, res: 8 cm-1, 200mw,
                             300 scans,10x obj.
                         Forensic Application
Cocaine particle on banknote
            0.05
            0.04




                                                                x
    Raman Intensity
              0.03




                                                          Cocaine
   0.02     0.01




                                                  Banknote paper
            0.00




                      3500         3000              2500              2000                   1500       1000   500
                                                                    Wavenumber cm-1


    C:\Programme\OPUS5_0_53\WORK\Av.10      Cocaine_onbanknote | Av. of 2      Ramscope III an RFS100,                2006/02/16

                       Red: Cocaine
    D:\SM06\RASCOPE\SM06\banknote_paper.1     banknote_paper        Ramscope III an RFS100,                           2006/02/16
                       Blue: Banknote paper
                                                 Page 1 of 1
                       Laser; 1064nm, res: 8 cm-1, 200mw,
                       300 scans,10x obj.
                                                    Forensic Application                                  Heroine
secured on adhesive tape
             0.014
             0.012




                                                                   x
             0.010
    Raman Intensity
    0.006 0.008




                                                              Heroine
             0.004




                                                      Adhesive tape
             0.002
             0.000




                      3500           3000            2500              2000                 1500   1000     500
                                                                    Wavenumber cm-1


     D:\SM06\RASCOPE\SM06\Heroine_on_tape.0     Heroine_on_tape       Ramscope III an RFS100,                     2006/02/16

                      Red: Heroine
     D:\SM06\RASCOPE\SM06\Tape_securing.0     Tape_securing       Ramscope III an RFS100,                         2006/02/16
                      Blue: Adhesive tape
                                                Page 1 of 1
                      Laser; 1064nm, res: 8 cm-1, 200mw,
                      300 scans,10x obj.
Depth Profiling of the First Three Layers of a
5-Layer Polymer Laminate


                                                            5


    Raman laser


                                                            10


    OPP 1. Layer
      20µm

    PA 2. Layer
                                   d ~ 5µm                  15
      2µm

    EVOH 3. Layer
      20µm



                                                            20
                            1600             1500    1400

                    Contour Line Map          cm-1
Depth Profiling of the First Three Layers of a
5-Layer Polymer Laminate

                               Conclusions
                               - Layer thickness is pertubed by
                                  refraction (2µm layer is broadened to
    Raman laser
                                  5µm)
                               - Refraction causes deeper penetration
                                  than “nominal” focal point
    OPP 1. Layer
      20µm
                               Recommended Solutions
    PA 2. Layer
      2µm
                               - Use immersion objectives
    EVOH 3. Layer
      20µm
                               - Make a cross section and map laterally


                    Everall, Neil J.
                    Applied Spectroscopy, Volume 54, Number 6, June 2000, pp. 773-782(10)
Raman:   Non Destructive Analysis


                              Diamond


                    8
                    4
                    0
                                           1500                                    1000                 500

           Raman Intensity
           Raman Intensity
              4     08        Moissanite

                                           1500
                                           1500                                   1000
                                                                                  1000                  500


                               Zirconia
                    8
                    4
                    0




                                           1500                                    1000                 500
                                                                                  Wavenumber cm-1


                                       Gemmologic studies of jewellery:
            D:\RA-Spektren\Anorganika\Diamond.0       Diamond         FT-Raman, RFS100/S, 1064 nm             2005/04/12

            D:\RA-Spektren\Anorganika\Moissanite.0      Moisannite        FT-Raman, RFS100/S, 1064 nm         2005/04/12

                             Diamond (C), Moissanite (SiC), Zirconia (ZrO2)
            D:\RA-Spektren\Anorganika\Zirkonia.0     Zirkonia        FT-Raman, RFS100/S, 1064 nm              2005/04/12

                                                                                    Page 1 of 1
      Distribution of API in tablets




                                       Integration of a
Integration of a
                                       band relevant
peak relevant
                                       for one
for API
                                       excipient
              FT-Raman microscopy
           Investigation of an Ancient Manuscript




                                               2.0
                                               1.5
                                      RAMAN INTENSITY
                                        1.0    0.5
                                               0.0
                                                        450   400   350     300        250   200   150   100
                                                                          WAVENUMBER CM-1




                                     Red ink: Cinnabar (HgS)




Piece of medieval manuscript



                               Surface map by FT-Raman
                                     spectroscopy
                FT-Raman Microscopy




                                            Reference Spectrum
                           Inclusion             of Sulfur




Mineral with
                    Calcium Fluorite Host
 inclusions
 (bright spot:
position of laser
     focus)
                                                            Analysis of Artwork
                                                                                                                                                                With courtesy of Prof. Ernst, ETH Zürich


                           Ancient tibetian Mandala
              0.10
           0.020
           0.018
           0.08
 0.012 0.014 0.016
  Raman Intensity
            0.06
  Raman Intensity
 0.04      0.008 0.010
           0.006
            0.000.02




                    800
                    1000     900 700     800       600 700              500
                                                                         600       500400                 400     300      300          200
                                                                                                                                          200             100
                                                                        Wavenumber cm-1


  O:\3OG_Ettlingen\CL\Spektren\Prof Ernst\FRA\Grosses Bild 1, 1(rot), FRA Sonde.1
                                                              4 (gelb), FRA Sonde.1     Grosses Bild 1(rot), FRA Sonde
                                                                                      Grosses Bild 1, 1, 4 (gelb), FRA Sonde                      10/09/2002
                                                                                                                               E55+FRA106/S; FT-Raman
                                                                                                                                  E55+FRA106/S; FT-Raman



Red: Spectrum of red area in Mandala
Blue: Spectrum of yellow area in Mandala
  O:\3OG_Ettlingen\CL\Spektren\Prof Ernst\RFS\1, weisser Untergrund, Sonde.5
                                    Ernst\RFS\6,                     Sonde.1      1, weisser Untergrund, Sonde
                                                                                  6,                                FT-Raman, RFS100/S            2002/08/14




Blue: Reference spectrum of Auripigment
Black:Reference Spectrum of Cinnabar
                           FT-Raman Microscopy


              0.04
                 0.03
    RAMAN INTENSITY




                                                                    (S-S)
    0.02      0.01
              0.00




                    3500   3000   2500   2000        1500   1000     500
                                         WAVENUMBER CM-1




RAMANSCOPE TM spectrum of a single human hair

				
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