ea sers 495 presentation.pdf
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Surface Enhanced Raman
Spectroscopy
Presented by: Eden Almakias
CHEM 495
March 21st 2016
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Presentation Outline
Introduction and background information
SERS theory
Applications of SERS
Conclusions
References
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Basics of Raman Spectroscopy
Raman spectroscopy is a technique which uses in
scattering to obtain information about molecular st
Incident light interacts with the analyte electron clo
momentarily exciting the molecule to a “virtual” sta
As light scatters off the molecule, some energy is
gained), resulting in a shift in the wavelength (Ram
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The Raman Effect: A Unified Treatment of the Theory of Raman Scattering by Mole
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http://bwtek.com/raman-theory-of-raman-scattering/
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The Raman Effect: A Unified Treatment of the Theory of Raman Scattering by Mole
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History of Raman Spectroscopy
In the mid-1920’s Indian physicists C.V. Raman and K.
used simple experiments to investigate light scattering
They observed that a portion of the scattered light was
lower energy (colour change).
This phenomenon occurred consistently in approximat
different liquids investigated.
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Initial experiments using sunlight and visual observatio
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C.V. Raman with his quartz spectrograph
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http://chemwiki.ucdavis.edu/Core/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Ram
scopy/Resonant_vs._Nonresonant_Raman_Spectroscopy
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What is SERS?
The Raman effect is relatively weak since only ≈ 1
photons scatter inelastically.
By using a metal (usually Ag or Au) surface, the in
Raman signals are greatly enhanced (up to a facto
This technique therefore counteracts one of the w
of Raman spectroscopy (low sensitivity).
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Discovery of SERS
SERS was first observed by Martin Fleischmann,
Hendra and A. J. McQuillan at the University of So
(1973).
The original purpose of their research was to inves
adsorption of pyridine on a roughened silver electr
Raman spectroscopy.
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Principles of Surface-Enhanced Raman Spectroscopy Eric C. Le Ru and Pablo G. E
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Abstract of original paper describing SERS.
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Explanation for SERS effect
The researchers attributed the enhanced intensity to th
surface area of the silver electrode.
In 1977, two research groups independently calculated
surface area cannot account for the observations.
One group proposed an electromagnetic enhancemen
other proposed a chemical enhancement (still under de
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Principles of Surface-Enhanced Raman Spectroscopy Eric C. Le Ru and Pablo G. E
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Factors influencing Enhancement
µ = E ·α
Magnitude of induced
dipole in scattering
molecule Magnitude of the
applied electric field
Polariza
scatterin
Determines intensity
of Raman signalInfluenced by local
electromagnetic
environment
Intrinsic pro
scattering m
(bond leng
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Chemical Enhancement
Chem. Soc. Rev
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Electromagnetic Enhancement
Incoming light of the appropriate frequency is able
a localized surface plasmon resonance (LSPR) in
surface.
This local electric oscillation supplements the elec
the incoming radiation and increases the magnitud
field experienced by the scattering molecule.
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Principles of Surface-Enhanced Raman Spectroscopy Eric C. Le Ru and Pablo G. E
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Angew. Chem. In
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19 SERS S b t t
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19 SERS Substrates
Anal Bioanal
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Illustration of SERS effect: Single Molecule Detectio
rhodamine 6G
Principles of Surface-Enhanced Raman Spectroscopy Eric C. Le Ru and Pablo G. E
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Application of SERS: monitoring of chem
syntheses in micro-droplets
Researchers at the university of Leipzig used SER
monitor dynamic chemical processes in a microflu
The reaction which they investigated was the Han
synthesis of 2-aminothiazoles.
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Chem. Commun
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Chem. Commun
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By monitoring the characteristic Ram
reactants and products the research
follow the progress of the reaction as
Chem. Commun
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Application of SERS: A ultrasensitive an
method for the quantitation of hydrazine
Hydrazine is a highly toxic compound used in man
processes including the synthesis of pesticides an
pharmaceuticals (120,000 tons produced annually
Researchers at the university of Notre Dame used
develop a method for the detection and quantificat
hydrazine at a sub-nanomolar level.
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Anal. Ch
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Anal. Ch
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Anal. Ch
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Anal. Ch
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Application of SERS: A platform for the
of cancer cells (SERS-microscopy)
Researchers at the university of Osnabruck have d
gold nanoparticles wrapped with a SERS active se
monolayer.
By coating these particles with silica and conjugat
antibodies, the particles were able to image the lo
p63 (tumor suppressor) in prostate biopsies.
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J. Biophotonics
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J. Biophotonics
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J. Biophotonics
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J. Biophotonics
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J. Biophotonics
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Conclusions
SERS is a very versatile and effective tool which can bmany different areas of research.
Since it is a relatively new technique, there are still are
be optimized (e.g. design of better substrates and rep
molecules)
Current trends in research show that SERS will definite
as researchers explore its potential.
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Anal Bioanal
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R f
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References
1) The Raman Effect: A Unified Treatment of the Theory of Raman Scattering by Molecules. Derek A
2) http://www.acs.org/content/dam/acsorg/education/whatischemistry/landmarks/ramaneffect/the-ra
commemorative-booklet.pdf
3) Principles of Surface-Enhanced Raman Spectroscopy Eric C. Le Ru and Pablo G. Etchegoin
4) Chem. Commun., 2015, 51, 8588—8591
5) Anal. Chem. 2015, 87, 6460−6464
6) J. Biophotonics 4, No. 6, 453 –463 (2011)
7) Anal Bioanal Chem (2012) 403:27 –54
http://www.acs.org/content/dam/acsorg/education/whatischemistry/landmarks/ramaneffect/the-raman-effect-commemorative-booklet.pdfhttp://www.acs.org/content/dam/acsorg/education/whatischemistry/landmarks/ramaneffect/the-raman-effect-commemorative-booklet.pdfhttp://www.acs.org/content/dam/acsorg/education/whatischemistry/landmarks/ramaneffect/the-raman-effect-commemorative-booklet.pdfhttp://www.acs.org/content/dam/acsorg/education/whatischemistry/landmarks/ramaneffect/the-raman-effect-commemorative-booklet.pdf