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2015: A new type of plasmon ruler

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Researchers from Lomonosov Moscow State University demonstrate the feasibility of using second-order plasmon resonances in order to increase the working range of plasmon rulers.

Nanoscale metrology is key to many applications in biology, physics, material science and others. One of the ways to measure distance on nanoscale—e.g., between DNA nucleotidesis to use the plasmon ruler approach. Within this approach, two gold nanoparticles are placed in two points of interest. It is known that gold nanoparticles exhibit strong plasmon resonances in the visible. The central wavelength of the resonance depends on the distance between the two nanoparticles. Knowing this dependence, one can solve the inverse problem by mapping the experimentally measured resonance wavelength to the unknown distance between the two points.

Traditional plasmon rulers that utilize the well-studied first order plasmon resonance have a substantial downsidethe working range of such a ruler has an upper limit of about 100 nm. In order to overcome this limitation, in collaboration with University Paris Sud 11, researchers from Lomonosov Moscow State University experimentally investigated the optical response of pairs of gold nanorods. It is known that elongated metallic objects support high-order modes; it turns out that watching at the second-order mode is far more beneficial in terms of extending the working range of the plasmon ruler. Now, with a second-order-based ruler, the upper limits of plasmon rulers are pushed all the way to 400 nm roughly the resolution limit of conventional optical microscopes, therefore tailoring the novel plasmonic ruler approach to routine optical metrology.

The results of this work have been published in the paper: M. R. Shcherbakov, A. T. Le, N. Dubrovina, A. Lupu, A. A. Fedyanin, “Plasmon ruler with gold nanorod dimers: utilizing the second-order resonance,” Optics Letters 40, 7, 1571-1574 (2015).