https://en.m.wikipedia.org/wiki/Plasmonic_nanoparticles https://en.m.wikipedia.org/wiki/Plasmonic_nanoparticles Plasmonic nanoparticles are particles whose ele

https://en.m.wikipedia.org/wiki/Plasmonic_nanoparticles https://en.m.wikipedia.org/wiki/Plasmonic_nanoparticles Plasmonic nanoparticles are particles whose electron density can couple with electromagnetic radiation of wavelengths that are far larger than the particle due to the nature of the dielectric-metal interface between the medium and the particles https://en.m.wikipedia.org/wiki/Surface_plasmon https://en.m.wikipedia.org/wiki/Surface_plasmon Surface plasmons (SPs) are coherent delocalized electron oscillations that exist at the interface between any two materials where the real part of the dielectric function changes sign across the interface (e.g. a metal-dielectric interface, such as a metal sheet in air). SPs have lower energy than bulk (or volume) plasmons which quantise the longitudinal electron oscillations about positive ion cores within the bulk of an electron gas (or plasma). https://en.m.wikipedia.org/wiki/Plasmon https://en.m.wikipedia.org/wiki/Plasmon In physics, a plasmon is a quantum of plasma oscillation. Just as light (an optical oscillation) consists of photons, the plasma oscillation consists of plasmons. The plasmon can be considered as a quasiparticle since it arises from the quantization of plasma oscillations, just like phonons are quantizations of mechanical vibrations. Thus, plasmons are collective (a discrete number) oscillations of the free electron gas density. For example, at optical frequencies, plasmons can couple with a photon to create another quasiparticle called a plasmon polariton.