Fluorophore
Definition and meaning of Fluorophore in chemistry.
A fluorophore is a molecule, or a specific chemical group within one, that absorbs light at one wavelength and re-emits it at a longer wavelength through fluorescence.
In more detail
Fluorophores typically contain extended conjugated pi-electron systems, often aromatic rings, that allow an electron to absorb a photon and jump to an excited singlet state. As the molecule relaxes back to the ground state, it loses some energy as heat (vibrational relaxation) before emitting a photon of lower energy and longer wavelength than the one absorbed, a gap called the Stokes shift. This property makes fluorophores essential as fluorescent dyes and tags for labeling biomolecules in microscopy, flow cytometry, and diagnostic assays. Note: "fluorophor" is an older or alternate spelling of the now-standard term "fluorophore."
Key facts
| Field | Analytical Chemistry |
|---|---|
| Key property | Stokes shift (emission wavelength > absorption wavelength) |
| Common examples | Fluorescein, DAPI, GFP chromophore, quantum dots |
| Structural feature | Extended conjugated pi-electron system, often aromatic |
Fluorescein, a widely used synthetic fluorophore, absorbs blue light near 494 nm and emits green light near 521 nm, making it useful for labeling antibodies in fluorescence microscopy.
Frequently asked questions
What is the difference between a fluorophore and a chromophore?
A chromophore is any group that absorbs visible light and gives a compound color; a fluorophore is a chromophore that also re-emits a portion of that absorbed energy as fluorescence rather than dissipating it entirely as heat.
Why is fluorescent emission always at a longer wavelength than the light absorbed?
Some absorbed energy is lost as heat through vibrational relaxation before the molecule emits a photon, so the emitted photon has lower energy and thus a longer wavelength than the absorbed one, a phenomenon called the Stokes shift.