BioNEM cover on Nature Nanotechnology

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BioNEM published on Nature Nanotechnology a paper on plasmonic nano-waveguides and gained the cover page of the relative journal issue. The title of the work is “Nanoscale chemical mapping using three-dimensional adiabatic compression of surface plasmon polaritons” and it deals with the combination of Raman spectroscopy and Atomic Force Microscopy (AFM) by means of cone-shaped plasmonic waveguides at the nanometer scale. The core of the work is indeed a metallic cone with height of 2.5 micrometer, base diameter of 300nm and curvature radius at the tip smaller than 10nm. This nanometric cone has been fabricated on an AFM cantilever and coupled with far field laser light through a photonic crystal optical cavity. This experimental arrangement allowed for simultaneous measurements of both sample topography by means of AFM and sample chemistry by means of Raman micro-spectroscopy with an unprecedented spatial resolution. The nanocones acts as a nanolens capable to produce an optical spot much smaller than the diffraction limit of light, exploiting the adiabatic compression of plasmon polaritons. An advantageous side effect of plasmon accumulation is a large enhancement of the electromagnetic field at the cone tip, thus producing an enhanced Raman signal in a very narrow area, comparable with the curvature radius of the tip. This effect has made possible to record Raman spectra with a spatial resolution of 7nm. The fields of applications of this technique are manifold, ranging from the materials science to biological and medical issues. As an example, the translation of this technique to wet environment could make possible to record a topographical and biochemical mapping of cells membrane with a spatial resolution never achieved before, thus opening a new world for biochemistry applied to membrane expression of biomolecules.