PerspectivePhysics

Detecting Intruders on the Nanoscale

+ See all authors and affiliations

Science  17 Jun 2011:
Vol. 332, Issue 6036, pp. 1389-1390
DOI: 10.1126/science.1207553

You are currently viewing the summary.

View Full Text

Summary

Intruder detectors work because they contain proximity sensors; for example, a person entering a room triggers a change in distance (see the figure, panel A). At the molecular scale, small metal objects, such as gold nanoparticles, can be attached to biomolecules and used as proximity sensors. The nanoparticles act as dipolar “antennas” for visible and near-infrared light waves and create plasmon resonances that strongly absorb or scatter light at specific frequencies. They act as one-dimensional (1D) plasmon rulers because the specific resonance frequency depends strongly on the proximity of other objects (1). More elaborate metal nanostructures, or metamaterials, show complex optical responses, with resonance modes corresponding to electric dipole and higher-order multiple oscillations (2). On page 1407 of this issue, Liu et al. (3) have used a stack of five gold nanorods that can report not just a single distance but the precise position of one central rod with respect to the others, creating a 3D plasmon ruler.