Overview of Raman Spectroscopy and portable markets

1. Overview of Raman Spectroscopy and portable markets Mark Schnittker 2013, Aug-23 schnittker@yahoo.com 408-368-1064

2. Some common measurement techniques General Techniques Fluorescence Refractometry Reflectometry Absorbance Molecular techniques (usually organic) Chromatography Mass spectroscopy Vibrational Spectroscopy IR resonance Scattering Resonance Atomic techniques (usually inorganic) X-ray spectroscopy Optical absorption Plasma discharge Trans FTIR Refl FTIR FTIR ATR Thermal Spectroscopy Raman spectroscopy FT Raman Surface Enhanced Raman (SERS) .

3. How vibrational spectroscopy works FTIR and Raman spectrum of Glucose showing vibrational modes 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). .

4. What information is in the spectrum? Triple Bonds Double Bonds Single Bonds Molecular rotation information Carbonyl group Harmonics Lattice vibrational modes 200cm-1 Raman of similar chemicals acetone ethanol Dimethylsulfoxide Ethyl acetate toluene 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.

5. Why is Raman spectroscopy “special”? Visible Mid IR NIR Molecular Bond information is in this range Raman Scattering moves information to shorter wavelengths Laser FTIR sees this region Raman Bond information similar to FTIR Water Absorption Anti-Stokes Stokes C.V. Raman Low cost optics  High resolution arrays  No water absorption  Fluorescence 

6. 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 .

7. Raman design trade offs Raman spectral range FTIR Raman Raman Raman 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 .

8. Raman market overview • http://www.spectroscopyonline.com/spectroscopy/Articles/Market-Profile-Portable-Raman-Spectroscopy/ArticleStandard/Article/detail/773924

9. 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.

10. 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.

11. 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.

12. 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 .

13. Existing Portable Market Participants

14. Existing Portable Market Participants Cont.

15. Investigating technical needs of a market segment acetaminophen Minerals 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. .

16. Want to get measurement in-house? Portable Raman Research grade Fiber coupled Too integrated. Not flexible enough 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. .

17. Thanks  Mark Schnittker Market development specialist contractor for xxxx Schnittker@yahoo.com 408-368-1064 .