What are the factors affecting Fluorescence and Phosphorescence?

The fluorescence and phosphorescence depends on following factors.

1. Fluorescence and phosphorescence depends on temperature and pH of the solution.

2. Association, Dissociation of solute with solvent will affect the fluorescence and phosphorescence.

3. Molecules with electron donating groups like -OH and –NH₂ are strongly fluorescence.

4. Electrons withdrawing groups like -COOH, -N=N-, -NO₂ and halides decreases florescence.

5. Heavy atoms like chlorine, bromine and iodine cause the un-pairing of electrons. As a result the singlet state gets converted into a triplet state and the chances of fluorescence occurring are greatly reduced.

6. Some groups like -NH₄⁺, -SO₃H and alkyl groups do not have, any affect on the fluorescence and phosphorescence phenomenon.

7. The introduction of an atom of higher atomic number, in to a $\pi$ electron system decreases fluorescence and increases phosphorescence.