Overview of Raman Spectroscopy and portable markets
Mark Schnittker 2013, Aug-23
[email protected] 408-368-1064
Some common measurement techniques
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Atomic techniques (usually inorganic)X-ray spectroscopyOptical absorptionPlasma discharge
Molecular techniques (usually organic)ChromatographyMass spectroscopyVibrational Spectroscopy
General TechniquesFluorescenceRefractometryReflectometryAbsorbance
IR resonance Scattering Resonance
Trans FTIRRefl FTIRFTIR ATRThermal Spectroscopy
Raman spectroscopyFT RamanSurface 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).
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FTIR and Raman spectrum of Glucose showing vibrational modes
0.00E+00
2.00E-01
4.00E-01
6.00E-01
8.00E-01
1.00E+00
1.20E+00
400600800100012001400
Wave number (1/cm)
FTIR Glucose in H2O
Raman Glucose in H2O
Marker lines
What information is in the spectrum?
Most of the identifying signatures are in the 500-1500 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.
Harmonics
Molecular rotation
information
Single BondsDouble BondsTriple Bonds
Carbonyl group Lattice
vibrational modes
200cm-1
acetone
ethanol
Dimethyl sulfoxide
Ethyl acetate
toluene
Raman of similar chemicals
Why is Raman spectroscopy “special”?
Low cost optics High resolution arrays No water absorption Fluorescence
NIR
FTIR sees this region
Water Absorption
Mid IR
Raman Bond information similar to FTIR
Stokes
Molecular Bond information is in this range
Laser
Visible
Raman Scattering moves information to shorter wavelengths
Anti-Stokes
C.V. Raman
Attributes of Raman Spectroscopy -Consequences Probability of Raman scatter ~1E-6.
– 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)
Avoids water absorption
– Able to see many of the molecular resonances – Works well with aqueous solutions
Probability of Raman scattering has dependencies (angular, temperature, ext)– 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– 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.
0
20
40
60
80
100
250525010250152502025025250Frequency (1/cm)
water absorption IR Si-CCD InGaAs array Fluorescence issues
532nm laser 650nm laser 785nm laser 830nm laser
Raman design trade offs
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
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Raman spectral range
Raman
Raman
FTIR
Raman
Raman market overview
http://www.spectroscopyonline.com/spectroscopy/Articles/Market-Profile-Portable-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)
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
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Need to see and know the peaks
Existing Portable Market ParticipantsCompany Product, Average
Selling PriceMarket Comments
Laser Spectral range
resolution
Thermo Scientific
First Defender Homeland Security Purchased from Ahura for $140M in 2010, and now has the largest market share.
785nm 300mW
250-2875 cm-1
8-10.5 cm-1
B&W Tek NanoRam Pharmaceuticals and Toxins
Awarded FDA contract over Thermo by being more willing to work with FDA.
785nm 300mW
175-3200 cm-1
<10 cm-1
Rigaku FirstGaurd Purchased from Bay Spec for undisclosed amount. Bayspec no longer allowed in handheld space.
532, 785,1064nm 500mW
200-2000 cm-1
7-10 cm-1
Intevac Pharma-ID Geology, Pharmaceuticals, Hazardous materials
Purchased from DeltaNu in 2007
785nm <100mW
300-2400 cm-1
10-12 cm-1
Existing Portable Market Participants Cont.Company Product, Average
Selling PriceMarket Comments
Laser Spectral Range
Resolution
Ocean Optics
Pin Pointer General Purchased from Raman Systems
785nm 5-500mW
200-2400cm-1
10 cm-1
Jasco RPM300 Authenticity. Art paintings Small volume specialty market
Enwave Optronics
EZ-Raman DefenseHazmat
785nm 300mW
100-2700 cm-1
6.5 cm-1
OptoTrace Ram Tracer Japanese backed Chinese company with silicon valley operations.
Redox module is very compact. Designed for biological applications
Optical Port
Raman Module65mm square
Power/Data Cable
Optional Li-Ion Battery
Data processing and bluetooth transmitter
Light weight molded optics with laser and integrated spectrometer
Specs: 830nm @140mW. 300-1700 cm-1 spectral range. ~10cm-1 resolution
Redox attributes in this marketbased 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.
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acetaminophenMinerals
Want to get measurement in-house?
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Portable Raman Research grade Fiber coupled
Too integrated. Not flexible enough Too expensive
and requires skilled operator
Good match. Flexible, and less expensive
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
408-368-1064
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