fluoresen

Fluoresen, also called fluorescence in many contexts, is the emission of light by a substance after it has absorbed electromagnetic radiation, typically ultraviolet or visible light. When a molecule or material absorbs a photon, an electron is promoted to a higher energy level. Much of the absorbed energy is dissipated as heat through rapid vibrational relaxation, and the remaining energy is released as a photon when the molecule returns to a lower energy state. The emitted light generally has a longer wavelength than the excitation light, a difference known as the Stokes shift.

Fluoresen is characterized by several key properties. The quantum yield describes the efficiency of fluorescence as the ratio of emitted to absorbed photons. The emission spectrum depends on the electronic structure of the fluorophore and can be broadened by interactions with the surrounding environment. Fluorescence lifetimes are typically in the nanosecond range, and the exact spectral profile can shift with factors such as solvent, temperature, and binding to other molecules.

Fluorophores used in fluorescence vary widely. Common organic dyes include fluorescein and rhodamine, while biological systems often employ fluorescent proteins such as green fluorescent protein (GFP). Inorganic fluorescent materials include certain quantum dots and rare-earth-doped phosphors. The choice of fluorophore depends on factors like brightness, photostability, and compatibility with detection equipment.

Applications of fluoresen span biology, chemistry, and materials science. It is foundational in fluorescence microscopy, flow cytometry, and various labeling and sensing assays. Fluorescence is also used in lighting and display technologies through fluorescent materials and phosphors. Limitations include photobleaching, autofluorescence from biological samples, and environmental effects that can alter spectral properties.