Thoughts About ICORS 2010 and Where Raman Spectroscopy Is Headed

Oct 01, 2010

Fran Adar
What I see as being really interesting is how the applications and instrumentation developments are driving each other. Raman, of course, is mainly a spectroscopy of vibrational transitions, and as such, is loaded with information-content. For a variety of reasons, IR absorption, in particular FT-IR, is more mature as an analytical technique than Raman, but with the introduction of the holographic notch filters in 1990 (1), air-cooled lasers, and low-noise CCD detectors, Raman instrumentation has become smaller, less expensive, and easier to use, so its successful implementation in many disciplines has created new applications. This in turn is pushing the instrumentation to do more.

Microscopy is an area where Raman has had a potential impact since its introduction in 1973 (2). I say potential because as long as the instrumentation was large with utility-intensive lasers and little computational power, its use was limited. But now that proof-of-principle has been shown for many applications, and the instrumentation is more user friendly, people want higher sensitivity and higher spatial resolution, and these are two of the areas that I want to discuss.


We see a lot of activity in the study of carbon nanomaterials such as nanotubes and graphene (single hexagonal carbon sheets). There is no space to review all the carbon talks and posters, but we want to mention at least, the plenary talk by Andrea C. Ferrari (3) as well as talks by Mildred Dresselhaus (4), Marcos Pimenta (5), and Janina Maultzsch (6). These materials have fascinating resonance. Raman properties following from their unique electronic properties and because of their high electronic mobility are of interest in integrating into electronic circuitry. Raman studies will aid in selecting the particular species and engineering their use.

I discussed surfaced-enhanced Raman scattering (SERS) in a column almost two years ago. The topic was selected because of its potential to provide sensitivity to things that cannot be detected or studied presently. Because I want to discuss the sensitivity issue in this column, I will start with a review of some of the SERS work reported at ICORS 2010. John Lombardi (7) reviewed the various theories of SERS, and discussed how the mechanisms determining these effects can be differentiated. In one of the plenary talks, Martin Moskovits (8) reviewed the status of robust SERS platforms that can enable reliable application of this technology to reproducible analysis. In his opinion, this technology is robust enough for reliable commercial application of Raman. If he is correct, specialized Raman products will be used for routine analytical chemistry that can be applied to clinical chemistry, industrial analysis, homeland security, and so forth.

Using a "lab-on-a-chip" to study chemical reactions, separations, analysis, and bio-organisms has always seemed to have potential. For example, Anne Marz (9), working with Juergen Popp, demonstrated sensitivity and robustness for detecting specific molecules in blood assays. In one case, they looked for an antibiotic, and in the second case, they looked for a metabolite of an immunosuppressant agent that is myelotoxic. They used a sum vector machine (SVM) to evaluate the accuracy of their enzyme activity test. The goal was to provide a means to adjust the drug dosage within a range where it would be active, but not generate the toxic side product. Mischa Bonn (10)and Marcus Motzkus (11) have been developing micro-CARS for the lab-on-a-chip application, as well as some other applications, and their innovations will be discussed in the instrumentation section of this column.

For me, the greatest excitement lies in the developments in the biological and clinical sciences. My postgraduate career started in the Johnson Foundation at the University of Pennsylvania, which was the Department of Biochemistry and Biophysics. When I left academia for the commercial life, the hope was that Raman could play a role in these areas. But, at the time (1978), I looked at the complexity of these systems and felt that even the microscope offered little hope of being able to unravel complex biochemical and physiological states. I am glad that 30 years has changed this. Let me try to select some areas in which Raman is having an impact. There is a lot to choose from, as many researchers who have been active in these areas gave talks during the conference. In addition, I should report that there was a tribute to Michael Feld, a pioneer in this field, who passed away a few months ago.

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