Photochromic Sodalites by a New Method of Synthesis

Abstract

Photochromic sodalites, also known as hackmanites, are minerals that belong to the sodalite mineral group and have a general formula of Na8(SiAlO4)6(Cl,S)2. Hackmanites can exhibit reversible photochromism i.e., tenebrescence, photoluminescence and persistent luminescence upon UV irradiation. In tenebrescence, hackmanite changes colour, traditionally from white to purple corresponding to a formation of an F-centre which absorbs light of around 540 nm, after UV or X-ray irradiation. The tenebrescence colour can be bleached with either heat or visible light. Synthesized hackmanites show various luminescence and tenebrescence properties, and, for the first time, yellow and near-infrared tenebrescence are reported for hackmanites. Hackmanites with these exciting new properties could potentially be used as materials for different applications, including advanced anti-counterfeiting.