PerspectiveApplied Physics

Hot Electrons Cross Boundaries

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Science  06 May 2011:
Vol. 332, Issue 6030, pp. 676-677
DOI: 10.1126/science.1205312

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Summary

When light hits the surface of gold or silver, it can excite collective oscillations of the conduction electrons called surface plasmons. The sensitivity of surface plasmons to changes in the surface region forms the basis of analytical tools such as surface plasmon resonance detection, which can be used in lab-on-a-chip applications to detect biomolecules. The excitation of surface plasmons also underlies surface-enhanced Raman spectroscopy. The surface plasmon of silver and gold surfaces that are rough at a nanoscale greatly increases local electric fields and boosts the signal from adsorbed molecules. The wavelength that excites surface plasmons can also be tuned by creating nanoparticles of different sizes, and on page 702 of this issue, Knight et al. (1) exploit this effect to create a detector for near-infrared light. They fabricated a device consisting of rod-like nanoantennas that harvest light and convert a portion of the resulting plasmonic energy into an electric current without the need for an applied bias voltage.

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