Hackmanite—The Natural Glow-in-the-Dark Material
Cecilia Agamah, Sami Vuori, Pauline Colinet, Isabella Norrbo, José Miranda de Carvalho, Liana Key Okada Nakamura, Joachim Lindblom, L. Van Goethem, Axel Emmermann, Timo Saarinen, Tero Laihinen, Eero Laakkonen, J. Lindén, J. Konu, Henk Vrielinck, David Van der Heggen, Philippe F. Smet, Tangui Le Bahers, Mika Lastusaari
Abstract
“Glow-in-the-dark” materials are known to practically everyone who has ever traveled by airplane or cruise ship, since they are commonly used for self-lit emergency exit signs. The green afterglow, persistent luminescence (PeL), is obtained from divalent europium doped to a synthetic strontium aluminate, but there are also some natural minerals capable of afterglow. One such mineral is hackmanite, the afterglow of which has never been thoroughly investigated, even if its synthetic versions can compete with some of the best commercially available synthetic PeL materials. Here we combine experimental and computational data to show that the white PeL of natural hackmanite is generated and controlled by a very delicate interplay between the natural impurities present. The results obtained shed light on the PeL phenomenon itself thus giving insight into improving the performance of synthetic materials.