Surface plasmon resonance (SPR) refers to a phenomenon that occurs when light interacts with a metallic surface causing the excitation of collective electron oscillations, known as plasmons, near the surface. This phenomenon typically occurs when a thin metal film, such as gold or silver, is deposited on a transparent material, like glass, enabling the coupling of light and electron oscillations.
In more technical terms, SPR involves the absorption of photons by the metal film, which leads to the generation of plasmons. These plasmons propagate along the metal-dielectric interface, resulting in a redistribution of electrical charges and the creation of a standing wave. The incident light and evanescent wave component interact with the excited plasmons, leading to a characteristic decrease in the reflected or transmitted light intensity at a specific angle known as the resonance angle.
SPR has found widespread use in various fields, particularly in the study of molecular interactions. When a biomolecular analyte binds to a surface immobilized with specific receptors, such as antibodies, the local refractive index changes, affecting the resonance condition. By monitoring the shifts in the angle or intensity of the reflected or transmitted light, valuable information about the analyte's concentration, binding affinity, kinetics, and other relevant parameters can be obtained.
Due to its sensitivity, label-free nature, real-time measurements, and wide dynamic range, SPR has become an invaluable tool in numerous applications, including biosensing, drug discovery, environmental monitoring, and nanotechnology research.
