Raman Scattering Measures Single-Molecule Vibrations

Measurement of the vibrations, or “breathing,” of single molecules is now possible using Raman spectroscopy techniques.

A team from the University of California, Irvine, viewed a bipyridylethylene (BPE) molecule vibrating via time-resolved coherent anti-Stokes Raman scattering (CARS). Two 90-nm gold plasmonic nanoantennas amplified radiation reflected from the single molecule to a detectable level.

“Detecting one molecule through scattering of light is extremely difficult, which is why we needed to amplify the signal,” said Dr. Eero Hulkko, a visiting researcher from the Academy of Finland.

Nanoparticle amplification of molecular signals is employed in various spectroscopic techniques, such as surface-enhanced Raman scattering (SERS). Combining the ability of SERS to detect single molecules with the extreme time resolution of time-resolved CARS enabled observation of the single molecule vibrations, the researchers said.

“Observing the breathing of a single molecule takes us one step closer to seeing real chemistry at work at the level of a single molecule,” said UCI professor Dr. Vartkess A. Apkarian.

The research was published in Nature Photonics (doi: 10.1038/nphoton.2014.143).