'Molecular roller coaster' can distinguish molecules
New measurement method University of Twente not only more sensitive but also more specific
Not only can it detect molecules extremely accurately, but it can also distinguish these with incredible precision: the detection method developed by researchers from the MESA+ and MIRA research institutes of the University of Twente is even more sensitive than previously demonstrated. This was revealed by research that made the cover of the leading journal Analytical Chemistry last week. The research was partly funded by Nanoned, FOM and NWO.
The molecules present in a solution can be measured with a technique called Coherent Anti-stokes Raman Spectroscopy (CARS). Molecules that are very similar to each other remain difficult to distinguish, however. The researchers from the University of Twente had previously introduced an improved form of CARS, which is far more sensitive and can detect molecules at much lower concentrations than other techniques. In this latest piece of research, the scientists have demonstrated that their method is not only far more sensitive but can also be used to detect up to ten different types of molecule at once. Previously, that was only possible with several successive measurements. This new technique is therefore considerably faster. The technique can be used, for example, to 'film' how medicines are released from a tablet, or how a living cell combusts fats. The researchers mainly see applications in the pharmaceutical industry and in cell biology research.
If you shine laser light on two molecules then some of these will absorb photons (light particles) and emit new photons. The photons emitted have a higher energy than the original photons. With the aid of Anti-stokes Raman Spectroscopy, these photons can be caught and used to determine which molecules are present in the solution. This is done by examining the amplitude of the light vibration. The new method from the Twente researchers not only examines the amplitude of the vibration but also the phase. Plotting the amplitude and the phase of the light vibration on a graph creates a complicated spiral that the researchers have dubbed the 'molecular roller coaster'. Thanks to this roller coaster, extremely similar substances can still be distinguished from each other.
Reference
'Visualizing Resonances in the Complex Plane with Vibrational Phase Contrast Coherent Anti-Stokes Raman Scattering', Martin Jurna, Erik Garbacik, Jeroen Korterik, Jennifer Herek, Cees Otto and Herman Offerhaus, Analytical Chemistry.
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