Figure 4.

Schematic illustrations of (a) Localized Surface Plasmon Resonances and (b) Surface Plasmon Polaritons. Note the differences in morphologies of the structures involved. LSPRs are excited on metal nanostructures smaller than the electron mean free path within the material as well as smaller than the wavelength of incident light, such as the nanospheres in (a) where free electrons are displaced from the positive ions, driven by the propagating electric field component of the incident light, and oscillate collectively in resonance. In (b) the metal surface’s characteristic dimension is larger than the wavelength of incident light resulting in the excitation of a propagating surface plasmon polariton that travels along the surface with evanescent waves that diminish perpendicular to the surface. Reprinted with permission from Ref [120] Copyright Royal Society of Chemistry (2016).