Lyoluminescence refers to the emission of light while dissolving a solid into a liquid
solvent
A solvent (s) (from the Latin '' solvÅ'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
. It is a form of
chemiluminescence. The most common lyoluminescent effect is seen when solid samples which have been heavily
irradiated
Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve ...
by
ionizing radiation are dissolved in water. The total amount of light emitted by the material increases proportionally with the total radiation dose received by the material up to a certain level called the saturation value.
Many gamma-irradiated substances are known to produce lyoluminescence; these include
spices
A spice is a seed, fruit, root, bark, or other plant substance primarily used for flavoring or coloring food. Spices are distinguished from herbs, which are the leaves, flowers, or stems of plants used for flavoring or as a garnish. Spices are ...
,
powdered milk
Powdered milk, also called milk powder, dried milk, or dry milk, is a manufactured dairy product made by evaporating milk to dryness. One purpose of drying milk is to preserve it; milk powder has a far longer shelf life than liquid milk and do ...
, soups, cotton and paper. While the broad variety of materials which exhibit lyoluminescence confounds explanation by a single common mechanism there is a common feature to the phenomenon, the production of
free radicals in solution. Lyoluminescence intensity can be increased by performing the dissolution of the solid in a solution containing conventionally chemiluminescent compounds such as
luminol
Luminol (C8H7N3O2) is a chemical that exhibits chemiluminescence, with a blue glow, when mixed with an appropriate oxidizing agent. Luminol is a white-to-pale-yellow crystalline solid that is soluble in most polar organic solvents, but insolub ...
.
These are thus called lyoluminescence sensitizers.
References
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Luminescence