Researchers have performed simultaneous optical and electrical measurements on a single molecule
Understanding how individual molecules conduct electricity is essential in efforts to make single-molecule devices, but it is difficult for researchers to be sure that they are measuring the properties of just one molecule. Now Douglas Natelson of Rice University and co-workers1 have shown for the first time that it is possible to make simultaneous electrical and optical measurements on the same molecule.
Natelson and co-workers used electron beams to make two gold electrodes on a silicon wafer, leaving a gap of less than 5 nm — which is comparable to the size of a molecule — between the electrodes. The device was then soaked in a solution of organic molecules and observed with near-infrared Raman spectroscopy. The electrical conductance of the gap was found to be well correlated with the Raman signal, implying that both measurements were being made on the same molecule.
The technique works because the gap between electrodes magnifies radiation in the near-infrared part of the spectrum, which makes it possible to see the optical 'fingerprint' of a single molecule trapped in the gap. Their technique could pave the way to mass-produced single-molecule sensors.
References
Ward, D. R. et al. Simultaneous measurements of electronic conduction and Raman response in molecular junctions. Nano. Lett. 10.1021/nl073346h (2008).
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Reid, T. At the double. Nature Nanotech (2008). https://doi.org/10.1038/nnano.2008.55
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DOI: https://doi.org/10.1038/nnano.2008.55
