Wavelength Tech Forum: Raman Technology

Raman spectroscopy is one of the fastest growing analytical techniques in use today. In this month's Technology Forum, we look at some of the reasons for the increase in its popularity and new applications for the technique. From Mesophotonics Limited, our participants are Caterina Netti, applications manager, and Stephen Allen, Vice President, Analytical Business. Our participants from HORIBA Jobin Yvon are Fran Adar, Worldwide Raman Applications Manager, and Andrew Whitley, Vice President, Raman Spectroscopy.

The Raman market has grown significantly in recent years, as the technique has grown in popularity. Where do you see the market going from here?

Netti/Allen: We expect the growth to accelerate as smaller, lower-cost Raman instruments drive applications in 3 main areas: process monitoring, medical diagnostics, and field-based analysis.

Adar/Whitley: I can only see the rapid expansion continuing. The market is really starting to see the beauty and power of Raman now. Fundamental molecular information with no sample preparation or damage, the ability to measure samples through light transparent material (so easy in-situ experiments), submicron (in some cases 50nm) spatial resolution, very high sensitivity (when coupled with SERS) - all this and it is now very easy to use and affordable. We will not only see smaller and less expensive application-specific systems but also more systems that combine Raman with other techniques, like Raman/FT-IR and Raman/AFM hybrids that provide researchers simultaneous but different information from a sample.

What are the best/most cutting-edge application(s) of Raman that you have seen recently?

Netti/Allen: We're really excited about some of the medical diagnostics applications that are being developed using Surface-Enhanced Resonance Raman (SERRS) tagged biomolecules. It looks like they can achieve 1,000 times lower detection limits than fluorescence, with much better specificity.

Adar/Whitley: Raman mapping/imaging is really starting to move forward. Using new advanced components and software, we are providing many of our customers with the ability to do rapid Raman hyperspectral imaging - often each pixel in the Raman map is obtained in only milliseconds. Also, the combined AFM/Raman (TERS) systems are pushing the spatial resolution of the technique down to 50nm.

What do you see for the future with regard to process-scale Raman? Will it grow as rapidly as microscopic/analytical-scale research has?

Netti/Allen: The non-destructive, non-invasive nature of Raman fits perfectly with the goals of the pharmaceutical industry's Process Analytical Technology (PAT) initiative. This should fuel rapid growth of the use of Raman, although its rollout beyond Method Development will be tempered by the regulatory hurdles.

Adar/Whitley: It already is. Raman provides information that few process techniques can, though there is a price barrier for process control instrumentation. People will always choose cheaper, simpler instrumentation whenever possible.

What is the one Raman application area that you see growing the fastest?

Netti/Allen: There's so much going on in developing medical diagnostic applications that the area will explode as soon as one or two specific tests are approved.

Adar/Whitley: Sorry, but I have to give two. The use of Raman in the fields of nanotechnology and biotechnology will grow the fastest. The majority of people studying carbon nanotubes use Raman, and the market will continue to grow as the work in this field continues to be heavily funded. Raman is also growing very rapidly in the field of biotechnology. Long-term I see this becoming the fastest-growing market - the ability of Raman to provide high enough spatial resolution to enable cellular studies without interference from water is very powerful. This is one area where Raman imaging, discussed above, is providing a wealth of information.

Raman was first theorized in the 1920s by C.V. Raman. Why has it taken so long for the technique to achieve prominence in the field?

Netti/Allen: The complexity and cost of Raman instrumentation, as well as its relatively poor sensitivity, have, until very recently, confined the technique to the research lab. Meanwhile, Infrared, especially FT-IR spectroscopy, has become the established technique for vibrational spectroscopy. Now, the availability of low-cost, small instruments and techniques such as SERS that dramatically improve sensitivity should tip the balance toward Raman.

Adar/Whitley: Until CCDs and holographic notch filters became available in the 1980s, the technique had low sensitivity and was difficult to use, though many researchers still recognized the advantages of the technique. With the introduction of new Raman instruments in the 1990s, which took advantage of the new technology, Raman slowly started to catch people's attention and now there is no holding it back.

What do you think?

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