Surface plasmon resonance
Overview
 
The excitation of surface plasmon
Surface plasmon
Surface plasmons , are coherent electron oscillations that exist at the interface between any two materials where the real part of the dielectric function changes sign across the interface...

s by light is denoted as a surface plasmon resonance (SPR) for planar surfaces or localized surface plasmon resonance (LSPR) for nanometer-sized metallic structures.

This phenomenon is the basis of many standard tools for measuring adsorption
Adsorption
Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...

 of material onto planar metal (typically gold and silver) surfaces or onto the surface of metal nanoparticle
Nanoparticle
In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size : in terms of diameter, coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are sized...

s. It is the fundamental behind many color-based biosensor
Biosensor
A biosensor is an analytical device for the detection of an analyte that combines a biological component with a physicochemical detector component.It consists of 3 parts:* the sensitive biological element A biosensor is an analytical device for the detection of an analyte that combines a biological...

 applications and different lab-on-a-chip
Lab-on-a-chip
A lab-on-a-chip is a device that integrates one or several laboratory functions on a single chip of only millimeters to a few square centimeters in size. LOCs deal with the handling of extremely small fluid volumes down to less than pico liters. Lab-on-a-chip devices are a subset of MEMS devices...

 sensors.
Surface plasmons, also known as surface plasmon polaritons
Surface plasmon polaritons
Surface plasmon polaritons , are infrared or visible frequency electromagnetic waves trapped at or guided along metal-dielectric interfaces. These are shorter in wavelength than the incident light...

, are surface electromagnetic waves that propagate in a direction parallel to the metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

/dielectric
Dielectric
A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric...

 (or metal/vacuum) interface.
 
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