Derivatising the compounds:
Despite the above described categories of molecules, the number of molecules having intrinsic fluorescence capabilities is extremely small. Therefore this does not limit the applications of the fluorescence measurements. The applicability of fluorimetry could be extended through derivatising the compounds which do not exhibit intrinsic fluorescence to make fluorescent derivatives. Another possibility is that the nonfluorescent molecule might be chemically attached along with a fluorescent tag or label.
Let us now know how structure of a molecule affects its features of phosphorescence. As regards phosphorescence, it has been observed in which the introduction of certain paramagnetic metal ions like as copper and nickel provides rise to phosphorescence. These ions do not induce fluorescence, on the contrary Mg and Zn compounds display strong fluorescence. Phosphorescence is affected through the molecular structure such as unsubstituted cyclic and polycyclic hydrocarbons and those containing -CH3, -NH2, -OH2, -COOH, -OCH3 substituents which have lifetimes in the range of 5-10 seconds for benzene derivatives and 1- 4 seconds for naphthalene derivatives. The introduction of a nitro group (NO2) within a structure diminishes the intensity of phosphorescence, as does the introduction of aldehyde and ketonic carbonyl groups. The emission life time (τ) is in seconds within rigid media and is 10-2 -100 seconds in fluid media.