Question

Compare and contract chemiluminescence, fluorescence, phosphorescence, bioluminescence, and triboluminescence.

Answer 1

1) Chemiluminescence is the production of light from a chemical reaction. Two chemicals react to form an excited (high-energy) intermediate, which breaks down releasing some of its energy as photons of light to reach its ground state.

2) Fluorescence, a type of luminescence, occurs in gas, liquid or solid chemical systems. Fluorescence is brought about by absorption of photons in the singlet ground state promoted to a singlet excited state. The spin of the electron is still paired with the ground state electron, unlike phosphorescence. As the excited molecule returns to ground state, it involves the emission of a photon of lower energy, which corresponds to a longer wavelength, than the absorbed photon.

3) As in fluorescence, a phosphorescent material absorbs high energy light (usually ultraviolet), causing the electrons to move into a higher energy state, but the transition back to a lower energy state occurs much more slowly and the direction of the electron spin may change. Phosphorescent materials may appear to glow for several seconds up to a couple of days after the light has been turned off. The reason phosphorescence lasts longer than fluorescence is because the excited electrons jump to a higher energy level than for fluorescence. The electrons have more energy to lose and may spend time at different energy levels between the excited state and the ground state.

4) The light emitted by a bioluminescent organism is produced by energy released from chemical reactions occurring inside (or ejected by) the organism.The chemical reaction that results in bioluminescence requires two unique chemicals: luciferin and either luciferase or photoprotein. Luciferin is the compound that actually produces light. In a chemical reaction, luciferin is called the substrate. The bioluminescent color (yellow in fireflies, greenish in lanternfish) is a result of the arrangement of luciferin molecules.

5) Triboluminescence is tribology phenomenon resulting in the generation of light through creating any frictional interaction between the materials. Triboluminescence can be observed only when there is a material that absorbs the generated ultraviolet light and then emits it in the visible range (fluoresces). Many other materials exhibit triboluminescence. Regular sugar cubes as well as any candy made with sugar (sucrose).