Molecular sensors based on scattering spectroscopy of single gold nanoparticles can be improved three-fold by the use of gold nanoshells instead of solid gold nanoparticles. The particle plasmon resonance responds more sensitively to changes in the environment, the biological spectral window is accessible, and the scattering spectra show sharper resonances. In particular, we focus our discussion on the narrow homogeneous line width of only 180 meV.

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