![]() Over the past 30 years, the material has been studied intensively by many other researchers. It is the material that makes the hands, dials and markers of a watch glow in the dark and is marketed under the brand names LumiNova, Super-LumiNova and LumiBrite, among others. The phosphor has been used as pigments in luminous paints and coatings for various applications. The material is strontium aluminate with small amounts of rare-earth elements europium and dysprosium, which act as defects (atomic-scale imperfections) in the otherwise perfect crystal. "Their discovery gave birth to an exciting and rapidly growing era of scientific research on persistent luminescence-a physical phenomenon in which a material re-emits light over a long period of time after the light source has been switched off." in Japan successfully developed a new material that re-emits extremely bright green light over many hours in the dark," said Khang Hoang, the author of the paper. ![]() "The story really began on March 12, 1993, when researchers with Nemoto and Co. The findings are reported in a paper titled "Defects and persistent luminescence in Eu-doped SrAl 2O 4," published in the journal Physical Review Applied. ![]() DOI: 10.1103/PhysRevApplied.19.024060Ī researcher in NDSU's Center for Computationally Assisted Science and Technology and the Department of Physics has uncovered what makes a prominent paint glow in the dark for hours. Schematic illustrations of a persistent luminescence mechanism under (a) band-to-band or (b) below-gap excitation: 1, excitation-electrons are excited and holes generated under illumination 2, trapping-the excited electrons (generated holes) are captured nonradiatively by electron (hole) traps through the conduction (valence) band and/or via quantum tunneling 3, detrapping-the trapped electrons are released under thermal stimulation 4, recombination-the released electrons return to the emission center and recombine with holes, resulting in a delayed luminescence.
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