Raman spectroscopy is awesome and you should too

Sir C.V. Raman, the namesake of Raman spectroscopy. Image from Wikipedia.

Raman spectroscopy is awesome. But these days it is rapidly getting more awesome. Here are a just a few new reasons to love Raman spectroscopy:

  1. It measures the metabolism of single living bacterial cells (in conjunction with stable isotopes).
  2. In mere seconds, it quantifies essentially all the various gases in 27 nanoliters of human breath.
  3. It does video-speed label-free chemical imaging on microscopic scales.
  4. It tracks in real-time the yields and titers of chemical and bichemical reactions, even at small scales.

And that’s just a few highlights from a deluge of recent papers about improved Raman spectroscopic methods. All are less than five years old. Two of those new results rely on stimulated Raman spectroscopy, a “turbocharged” improvement over the classical spontaneous Raman that boosts sensitivities by orders of magnitude. (The standard rub on spontaneous Raman has always been that it is fantastically insensitive. It relies on non-linear scattering, something that happens to only one in every few million photons scattered when you shine light on an object.) A third &emdash; the single-cell metabolic analysis of live bacteria &emdash; relies on confocal Raman microscopy.

I’m not an expert in Raman spectroscopy (or in any other type of optical spectroscopy for that matter), but even I can tell that what is driving these results are technical advances in laser optics and electronics. Think of things like improved control of picosecond laser chirp rates or use of complex fiber-optic capillaries. So it seems that right now, many of these souped up forms of Raman spectroscopy are accessible only to nonlinear optics experts.

My hope is that this will change, and the sooner the better &emdash; because wow those new results sure are neat. Other techniques don’t really offer much competition: what else can see and quantify specific molecules in live organisms as small as single bacterial cells without needing any fluorophores or fluorescent labels?

Scientists have found the traditional spontaneous Raman spectroscopy useful enough to craft 96-well microplate-compatible instruments, Raman microscopes have been commercialized for some time, and some folks (not me!) can even build Raman spectrometers in their garage. So let us all hope that some of these amazing new Raman techniques will find their way into cheaper, off-the-shelf instruments available at a lab near you.


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