“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:

  • flu­o­res­cein;
  • sodi­um hy­drox­ide;
  • dis­tilled wa­ter;
  • beakers.

Step-by-step in­struc­tions

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.

Pro­cess­es de­scrip­tion

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.

Safe­ty pre­cau­tions

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.

Try it