Overview of Raman Spectroscopy and portable markets

Mark Schnittker 2013, Aug-23

schnittker@yahoo.com 408-368-1064

Some common measurement techniques

.

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).

.

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

.

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

.

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.

.

acetaminophenMinerals

Want to get measurement in-house?

.

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

Schnittker@yahoo.com

408-368-1064

.