The new imaging method, which is described this week in the journal Nature Communications, uses a form of Raman spectroscopy in combination with an intricate but mass reproducible optical amplifier. Researchers at Rices Laboratory for Nanophotonics (LANP) said the single-molecule sensor is about 10 times more powerful that previously reported devices. Ours and other research groups have been designing single-molecule sensors for several years, but this new approach offers advantages over any previously reported method, said LANP Director Naomi Halas, the lead scientist on the study. The ideal single-molecule sensor would be able to identify an unknown molecule -- even a very small one -- without any prior information about that molecules structure or composition. Thats not possible with current technology, but this new technique has that potential. The optical sensor uses Raman spectroscopy, a technique pioneered in the 1930s that blossomed after the advent of lasers in the 1960s. When light strikes a molecule, most of its photons bounce off or pass directly through, but a tiny fraction -- fewer than one in a trillion -- are absorbed and re-emitted into another energy level that differs from their initial level. By measuring and analyzing these re-emitted photons through Raman spectroscopy, scientists can decipher the types of atoms in a molecule as well as their structural arrangement. Scientists have created a number of techniques to boost Raman signals. In the new study, LANP graduate student Yu Zhang used one of these, a two-coherent-laser technique called coherent anti-Stokes Raman spectroscopy, or CARS. By using CARS in conjunction with a light amplifier made of four tiny gold nanodiscs, Halas and Zhang were able to measure single molecules in a powerful new way. LANP has dubbed the new technique surface-enhanced CARS, or SECARS.
Posted on: Sat, 19 Jul 2014 14:06:30 +0000
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