A Little Taste of Mushy-Brain Syndrome

I've returned from SPIE Defense Security & Sensing both refreshed and also mentally exhausted. It was a multi-day bombardment of all things awesome in the world of remote environmental sensing and other similar fields. In fact, I left a day before the conference was scheduled to end because I knew my brain would turn to mush if I stayed for the entire duration. I know this because I stayed for the whole shebang last year and, although I learned much, could make little of the notes that I had taken once I returned. Those conference sessions seemed to boil together into a steamy stew of science in my brain. I kept getting confused between different sensing mechanisms and who, of the talks that I particularly enjoyed, gave talks about which subject...'Now, I think that was the Air Force Research Lab that's doing the aptamer-based sensors...or was it MIT? Oh no...'

This year at the conference, I tried to stick with sessions that were at least somewhat related to my research, which means that I strayed away from imaging and target detection and tracking and instead mostly attended sessions on environmental and chemical sensing and the like. It didn't take long for me to notice a very obvious trend. In fact, I noticed it on the very first morning when I gave my talk. I would've been a fool to not notice it because the topic every other speaker in my session presented was on a particular type of research. That research, you may be wondering, was SERS. SERS, not to be confused with SARS, stands for surface-enhanced Raman spectroscopy. To get a picture of how SERS works, let's start with the end in mind. And when I say 'end,' I mean the last two letters of the abbreviation: RS. Raman spectroscopy is a method of analyzing Raman scattering, the inelastic scattering of incident photons, from a species. The wavelength or wavelengths at which Raman scattering occurs are related to the vibrational energy of the molecular species, so that every molecule or compound has a particular Raman spectral fingerprint. By analyzing a particular sample, the Raman spectrum can be compared to known spectral fingerprints to identify the molecular makeup of the sample. The problem, however, is that Raman scattering is very weak, and this is where the first two letters, SE, come into play. Surfance enhancement of the Raman signal can be created when the sample being interrogated is applied to a nano-structured metallic surface. The gaps between nano-scale structures are tiny little amplifiers of the Raman scattering effect, most likely caused by local surface plasmon resonance effects.

This method of analyzing and identifying particular compounds with SERS is quite effective and also thoroughly documented, and so the primary research focus was on how to enhance the effect with various surface processing techniques and use of newfangled light sources, and also on how to apply this signal transduction method to a broader sensing platform. More specifically, how to grab the analyte of interest out of the environment so that SERS can be used to interrogate it. In fact, one group from the Army Research Lab was combining SERS signal transduction with molecularly imprinted polymers as a method for capturing the analyte. The reason this is of particular interest to me is because I also work with imprinted polymers and I found the entire scheme to be quite brilliant in its simplicity and effectiveness. However, I also realize from working with imprinted polymers that in practice there is absolutely nothing simple about it.

I have to admit that there were many other topics besides SERS that were discussed during the chemical and environmental sensing sessions at this year's Defense Security & Sensing. I noticed that laser-induced breakdown spectroscopy (LIBS) was a recurring theme, as was ion mobility spectroscopy (IMS), but SERS was overwhelmingly the most popular subject within the sessions that I attended. And now that I've got the topics that I was most interested in (and I'm probably the only one interested in them) out of the way, I will return shortly with another post that shares some of the more wicked-cool things that I learned about at this year's SPIE Defense Security & Sensing conference.