Plasmoniresonansseja

Plasmoniresonanssi, also known as surface plasmon resonance (SPR), is a phenomenon that occurs when free electrons in a metal film are excited by light at a specific frequency. This excitation causes the electrons to oscillate collectively, leading to a sharp increase in the absorption and scattering of light at that resonance frequency. The exact frequency at which plasmon resonance occurs is highly sensitive to the refractive index of the medium surrounding the metal film.

This sensitivity is the basis for SPR sensing. By immobilizing a sample of interest onto the surface of the metal film, changes in the local refractive index due to binding events can be detected. When molecules bind to the immobilized sample, they alter the refractive index near the metal surface, shifting the plasmon resonance frequency. This shift can be measured, providing a quantitative measure of the binding interaction. SPR is a label-free technique, meaning it does not require the use of fluorescent or radioactive tags on the molecules being studied.

Applications of plasmon resonance sensing are widespread, particularly in the fields of biosensing and chemical sensing. It is used to study molecular interactions, such as antigen-antibody binding, protein-ligand interactions, and DNA hybridization. Due to its high sensitivity and ability to monitor real-time interactions, SPR has become a valuable tool in drug discovery, diagnostics, and fundamental research in molecular biology and chemistry. The phenomenon itself is a manifestation of the interaction between light and matter at the nanoscale.