EA SERS 495 Presentation.pdf

8/19/2019 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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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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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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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



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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

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