Forensic and homeland security
applications of modern portable
Raman spectroscopy
Laura Fairburn
Mike Rusak
Summary of the Paper
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Applications in forensics and homeland security,
including field testing for chemical and biological
warfare agents
Subtypes of Raman Discussed:
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Convential Raman Spectroscopy
Resonance enhanced
Spatially offset (SORS)
Surface Enhancement (SERS)
can be coupled with Stand-Off Raman Detection
Raman Spectroscopy
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measures the scattering of monochromatic light
caused by the sample
most of the light reflects off the sample at the
same wavelength, while some light does scatter
at different wavelengths
this is caused by an interaction with a phonon,
which causes the laser to gain or lose energy
From that, information about the phonon mode
is supplied, from which we can determine
similarly to FT-IR what functional groups are in
the compound.
Raman Spectroscopy’s
Drawbacks
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Specific structure can’t be determined
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should be used as a last step analysis, not
first on site technique
Not very Powerful
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One photon in 108 photons will exhibit
Raman scattering
Drawbacks Cont.d
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Mixtures drastically complex the spectra,
therefore sample preparation may be
needed
Because of the high intensity laser used,
dark coloured explosives have been
known to heat up.
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In some causes, it has even caused
ignition
Drawbacks Cont.d
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Very expensive compared to other more
commonly used instruments
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double monochromators and laser
sources make it more expensive
compared to other instruments
Fluorescence can be a large problem
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Especially in the visible and UV regions
Slight impurities in compound may
fluoresce, complicating the spectrum
Drawbacks Cont.d
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If the intensity of the wavelength is too
high, such as when a UV laser is used,
the sample may thermally decompose.
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the most modest of lasers have been
known to cause band shifts in the
Raman Spectra
Potential Questions
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There were some questioned to be asked
after reading this article.
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What will happen if the material
you’re scanning through is Raman
active?
Is there a library of spectra for all
known biological hazardous agents?
Is this really the best technique for the
job it’s required to do?
Conclusion
• Raman Spectroscopy is undeniably
useful in the same way as infrared
spectroscopy in a chemistry lab, but it is
not routinely used in a forensic setting.
Therefore, why use it when concrete
techniques are can be used instead?
Eg) GC-MS, ion mobility spectrometry,
etc.