The Science Behind Glow in the Dark"Glow in the dark" falls under several different sciences including:
- Photoluminescence by definition is the emission of light from a molecule or atom that has absorbed electromagnetic energy: examples include fluorescence and phosphorescence materials. The glow in the dark plastic constellation kits that you stick on your wall or ceiling are an example of a photoluminescence based product.
- Bioluminescence is the light emitted by living organisms using an internal chemical reaction (think deep sea creatures)
- Chemiluminescence is the emission of light without the emission of heat as the result of a chemical reaction (for example glowsticks),
- Radioluminescence is created by the bombardment of ionizing radiation.
Chemiluminescence and photoluminescence are behind the majority of glow in the dark products. According to Alfred University professors, "the distinct difference between chemical luminescence and photo luminescence is that for light to work via chemical luminescence a chemical reaction has to occur, however during photo luminescence light is released without a chemical reaction.
Glow in the Dark - HistoryPhosphorus 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 photoluminescence 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 commonly used phosphors.
GlowsticksSeveral patents were issued for "Chemiluminescent Signal Devices" during the early seventies that were used for naval signaling. Inventors, Clarence Gilliam and Thomas Hall patented the first Chemical Lighting Device in October, 1973 (Patent 3,764,796). However, it is not clear who patented the very first glowstick designed for play.
In December, 1977 a patent was issued for a Chemical Light Device to inventor Richard Taylor Van Zandt (US Patent 4,064,428). Zandt's design was the first to add a steel ball inside the plastic tube that when shook would break the glass ampoule and start the chemical reaction. Many toy glowsticks were then built based on this design.
Glow in the Dark PigsScientists in Taiwan say they have bred three pigs that "glow in the dark".
Photoluminescence SpectroscopyPhotoluminescence 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.