Glow in the Dark Science

Photoluminescence by definition is the emission of light from a molecule or atom that has absorbed electromagnetic energy: examples include fluorescence and phosphorescence materials. Photoluminescence spectroscopy is a contactless, nondestructive method of probing the electronic structure of materials.

The photo to the right depicts photoluminescence materials spread on 7-inch wide roll. This is from a patent pending technology developed at Pacific Northwest National Laboratory that uses small organic molecule materials to create organic light-emitting devices (OLEDs) and other electronics. Proof-of-principle of the technique has been demonstrated by successfully coating the small molecule Alq3 on a PET substrate (photo). The method may also be used to produce “patterned” electronic thin-film devices in which an active small molecule organic material is selectively deposited on a substrate to form a pattern appropriate for the operation of the device. Photo: Department of Energy

History of Glow in the Dark
Glow in the dark powders, glow sticks, ropes etc. are all fun examples of photoluminescence. Phosphorus and its various compounds are phosphorescents, or materials that glow in the dark. Before knowing what phosphorus was, its glowing properties have been reported in ancient writings. The oldest known written observations were made in China, dating back to 1000 B.C. regarding fireflies and glow-worms. In 1602, Vincenzo Casciarolo, discovered the phosphorus glowing "Bolognian Stones" just outside of Bologna that started the first scientific study of photoluminescence.

Phosphorus was first isolated in 1669 by German physician Hennig Brand. Brand was an alchemist who was attempting to change metals into gold when he isolated phosphorus. All glow in the dark products contain phosphor. To make a glow in the dark toy, toymakers use a phosphor that is energized by normal light and that has a very long persistence - the length of time it glows. Zinc Sulfide and Strontium Aluminate are the two most commomly used phosphors.

Scientists in Taiwan say they have bred three pigs that "glow in the dark".