Raman and vibrational spectroscopy

Report
Overview of Raman Spectroscopy
and portable markets
Mark Schnittker 2013, Aug-23
[email protected] 408-368-1064
Some common measurement techniques
General Techniques
Fluorescence
Refractometry
Reflectometry
Absorbance
Molecular techniques (usually organic)
Chromatography
Mass spectroscopy
Vibrational Spectroscopy
IR resonance
Atomic techniques
(usually inorganic)
X-ray spectroscopy
Optical absorption
Plasma discharge
Trans FTIR
Refl FTIR
FTIR ATR
Thermal Spectroscopy
.
Scattering Resonance
Raman spectroscopy
FT Raman
Surface Enhanced
Raman (SERS)
How vibrational spectroscopy works




Every molecule has vibrational modes (states).
Vibrational modes = 3N-5 or 3N-6 pending the type of molecule where N=number of
atoms
“Group theory” determines which vibrational modes are “IR active”, “Scattering
active”, or “forbidden”.
Vibrational modes are quantized and will absorb photons of a specific energy (IR
spectroscopy), or steal that same amount of energy from an incident photon and
change the wavelength of the scattered photon (Raman spectroscopy).
FTIR and Raman spectrum of Glucose showing vibrational modes
1.20E+00
FTIR Glucose in H2O
Raman Glucose in H2O
1.00E+00
Marker lines
8.00E-01
6.00E-01
4.00E-01
2.00E-01
0.00E+00
1400
1200
1000
. (1/cm)
Wave number
800
600
400
What information is in the spectrum?
Triple Bonds Double Bonds
Single Bonds
Molecular
rotation
information
Harmonics
Carbonyl
group
Lattice
vibrational
modes
200cm-1
Raman of similar chemicals



Most of the identifying signatures are in the 5001500 cm-1 range
Carbonyl group in the 1600-1900cm-1 range is good
at differentiating similar chemicals.
With a good filter, raman can show lattice vibrational
modes down at 200cm-1 which describes the
physical structure of the sample.
acetone
ethanol
Dimethyl
sulfoxide
Ethyl
acetate
toluene
Why is Raman spectroscopy “special”?
Visible
Mid IR
NIR
Laser
Raman Scattering
moves information to
shorter wavelengths
Molecular Bond
information is in
this range
FTIR sees this region
Raman Bond
information
similar to FTIR
Anti-Stokes




Water
Absorption
Stokes
Low cost optics 
High resolution arrays 
No water absorption 
Fluorescence 
C.V. Raman
Attributes of Raman Spectroscopy
-Consequences

Probability of Raman scatter ~1E-6.
–
–
–
–

Avoids water absorption
–
–

Quantitative measurements are difficult
Raman is good at determining the presence of a molecule but not good at determining
percentages.
Centering based on available detectors and lasers
–
–

Able to see many of the molecular resonances
Works well with aqueous solutions
Probability of Raman scattering has dependencies (angular, temperature, ext)
–
–

Needs lots of laser power
Can over heat samples which have low Raman activity and low thermal conductivity
Does not work well for trace detection (SNR of CCD)
Does not work well with low density samples (gasses)
Has very low cost options
Fluorescence is often an issue
Sensitive to polarizable bonds like C=C C=N , but less sensitive to dipoles like O-H,
C-H, N-H
–
Needs good detector sensitivity in the 500-1500cm-1
range
.
Raman design trade offs
water absorption
IR Si-CCD
InGaAs array
Fluorescence issues
532nm laser
650nm laser
785nm laser
830nm laser
100
Raman spectral range
80
Raman
FTIR
Raman
60
Raman
40
20
0
25250
20250
15250
10250
5250
250
Frequency (1/cm)



Si detectors ~$50 with high pixel count
High frequency lasers product too much fluorescence. Low frequency lasers “walk off” Si
detector and reduce the available spectral range
InGaAs detectors solve spectral range issues but are expensive and have reduced
pixels=>lower spectral resolution
.
Raman market overview
http://www.spectroscopyonline.com/spectroscopy/Articles/Market-ProfilePortable-Raman-Spectroscopy/ArticleStandard/Article/detail/773924
Portable Raman Markets overview
 Biological: Hydration, Glucose- needs good fluorescence removal.
Must compete with transmission, fluorescent and low tech options.
 Homeland Security: Explosives and chemical agents detection. –
needs built in chemical library
 Consumer products regulatory compliance: Detection of phthalates
and other toxins in consumer products. –needs low cost and ease of
use, and high SNR for trace detection.
 Law Enforcement: Narcotics Analysis –needs built in chemical library
and authenticity certification
 Oil and Mining: Chemical /Mineral field analysis.
 Hazmat handling: First responders to accidents to evaluate threat –
needs built in chemical library and sealed.
Portable Raman Markets overview Cont.
 Environmental: Field evaluation of contaminants in waterways and
soils. These can also be permanently mounted modules in a
distributed sensing network. –needs super weather tight and UV
resistant housing
 Pharmaceuticals: Confirm shipments and mixtures through
containers. – needs large spectral rang, carbonyl group detection.
 Defense: Combat troops to check for explosives and chemical
weapons facilities –needs compact, light weight, battery powered,
hermetically sealed
 Authenticity: Counterfeit detection of paintings, money, branded
alcohol. –needs low fluorescence to see through glass
 Waste Management: Identification of reclaimed materials to
determine proper recycling method –needs high speed, high
efficiency to measure plastic fast without carbonizing it.
Process Raman Market.
 Process Raman uses small rugged modules which are
connected via USB to send back spectrum insitu from the
manufacturing line.
 Pharmaceuticals, plastics, petroleum, and chemical
manufacturing companies are the final customers of
process Raman.
 Example 1: Placing a small Raman module on the outside
of a rotating drum to monitor the mixture of pharmaceutical
chemicals
 Example 2: Leak detection. Sensor module mounted at
each valve or potential leak point, per recent new
regulation of hazardous emissions.
Key specifications (and how to
engineer them)
Need to
see and
know the
peaks

Fluorescence avoidance (Excitation laser l, post
process/fluorescence subtraction, feature-free spectral
throughput, very good spectral throughput calibration)

Spectral range (Excitation laser l, Detector choice)

Signal to noise (optical scattering, Laser power, detector dark
current, electrical noise, integration time, optical throughput)

Accuracy (temperature stabilization, calibration methods)

Resolution (Spectrometer design, detector choice)

Size, Weight, Ruggedness, Battery life
.
Existing Portable Market Participants
Company
Product, Average
Selling Price
Market
Thermo
Scientific
First Defender
Homeland Security
B&W Tek
NanoRam
Laser
785nm
300mW
2502875
cm-1
resolution
8-10.5
cm-1
1753200
cm-1
<10 cm1
FirstGaurd
532,
785,
1064nm
500mW
Intevac
Spectral
range
Pharmaceuticals and
Toxins
785nm
300mW
Rigaku
Comments
Pharma-ID
2002000
cm-1
7-10 cm1
Geology,
Pharmaceuticals,
Hazardous materials
785nm
<100m
W
3002400
cm-1
10-12
cm-1
Purchased from Ahura
for $140M in 2010, and
now has the largest
market share.
Awarded FDA contract
over Thermo by being
more willing to work
with FDA.
Purchased from Bay
Spec for undisclosed
amount. Bayspec no
longer allowed in
handheld space.
Purchased from
DeltaNu in 2007
Existing Portable Market Participants Cont.
Company
Ocean
Optics
Product, Average
Selling Price
Market
Pin Pointer
General
Laser
785nm
5500mW
Comments
Spectral
Range
2002400cm1
Resoluti
on
Purchased from
Raman Systems
10 cm-1
Jasco
RPM300
Authenticity. Art paintings
Enwave
Optronics
EZ-Raman
Defense
Hazmat
785nm
300mW
OptoTrace
Ram Tracer
1002700
cm-1
Small volume specialty
market
6.5 cm-1
Japanese backed
Chinese company with
silicon valley
operations.
Redox module is very compact.
Designed for biological applications
Specs: 830nm @140mW. 300-1700 cm-1 spectral range. ~10cm-1 resolution
Power/Data Cable
Optical Port
Data processing
and bluetooth
transmitter
Raman Module
65mm square
Optional LiIon Battery
Light weight molded
optics with laser and
integrated
spectrometer
Redox attributes in this market
based on current product form.
Small size and weight
Connectivity over cellular to libraries
Bluetooth enabled
Dynamically adjustable laser power
High Signal to Noise Ratio
Module is “smart” with on-board
processing.
Scratch resistant optical contact
Internal temperature stabilization
Reliable-Ruggedized
Auto proximity sensor for laser eye
safety concerns
Can be USB controlled
Battery operated option
Sealed
Investigating technical needs of a
market segment
 Partner with a customer which can test efficacy of a
system.
 Many chemicals have been cataloged in Raman
databases. To investigate a market, find out what
chemicals are involved in that market and pull up their
spectrum. Evaluate what spectral range and resolution
would be needed to identify the chemical. acetaminophen
Minerals
.
Want to get measurement in-house?
Portable Raman
Too integrated.
Not flexible
enough
Research grade
Fiber coupled
Good match. Flexible,
and less expensive
Too expensive
and requires
skilled operator
Home brew: Most flexible.
Good if you have in house
expertise.
Make a cheap fluorescence
set up and explore excitation
wavelengths before investing
in a Raman system.
.
Thanks 
Mark Schnittker
Market development specialist contractor for Redox
[email protected]
408-368-1064
.

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