“Fluorescence of fluorescein” experiment
How to make green luminescent dye
This colorful and interesting experiment demonstrates the properties of substances to emit radiation, usually light, under the impact of an external source of energy, usually ultra-violet. From this experiment, you will find out about the luminescence of fluorescent (ultraviolet) dyes, which are used, for example, in the manufacture of banknotes, decorating rooms and nightclubs, while fluorescein itself is used to dye rivers green on St. Patrick’s Day.
Reagents and equipment:
- sodium hydroxide;
- distilled water;
Prepare 20 ml of a 5 g/l solution of alkali in a 50 ml glass, by dissolving 0.1 g of NaOH in 20 ml of distilled water. Then add fluorescein to the obtained solution until the solution becomes brown, so we get a saturated solution of fluorescein in NaOH. Pour it into a beaker of water, turn off the light and turn on the UV lamp. Add the fluorescein solution to the water. Place a beaker on a blender, lower the rotor,pour in water and turn on the blender. Wait until a “distinctive” whirlpool forms, and add the fluorescein solution.
Fluorescence is the emission of radiation, usually light, from a substance, the atoms of which have received an excess amount of energy, for example under ultraviolet light. Without a source of energy, the fluorescence stops. Many substances possess this property, for example, fluorescein, quinine, the chlorophyll of plants and many others.
Be careful when working with an alkali and its solutions.
Warning! Substances of this experiment are toxic and highly dangerous for your health. Do not try this at home. Only under professional supervision.