Fluorescence is a type of luminescence, which is the emission of light by a substance that has absorbed light or other electromagnetic radiation. Specifically, fluorescence involves the absorption of light at one wavelength and the subsequent re-emission of light at a longer wavelength. The emitted light occurs almost instantaneously and ceases when the excitation light source is removed.
Key characteristics of fluorescence include:
Excitation and emission wavelengths: Fluorescent materials absorb photons of light at a specific wavelength (excitation wavelength) and then release photons at a longer wavelength (emission wavelength). The difference in wavelengths is known as the Stokes shift.
Fluorophores: Fluorescence is typically associated with substances called fluorophores or fluorescent dyes. These molecules contain specific chemical groups or structures that allow them to absorb and emit light in a characteristic manner.
Short duration: Fluorescence is a relatively short-lived process, with the emission occurring promptly after excitation. The duration of fluorescence is on the order of nanoseconds.
Fluorescence is widely used in various scientific and technological applications. In fluorescence microscopy, for example, fluorescent dyes are used to label specific structures or molecules within cells for visualization. Fluorescent markers are also employed in flow cytometry, medical diagnostics, and environmental monitoring.
The fluorescence of a material can be influenced by factors such as temperature, pH, and the presence of certain ions. Additionally, fluorescence can be quenched (reduced) or fade over time, which may impact the reliability of fluorescence-based assays.
Fluorescence is a powerful tool in biological and chemical research, providing a non-invasive and highly sensitive means of detecting and imaging specific substances. It has diverse applications in fields such as biology, medicine, environmental science, and materials science.