Room temperature long afterglow from boron oxide: A boric acid calcined product

Afterglow materials are of increasing importance. Here we report for the first time an intense long-lasting blue afterglow observed in a metal-activator-free boric acid calcined product. It was found that the afterglow intensity varied with the calcination temperature and reaches a maximum at around 250 °C, with a high phosphorescence lifetime of 1.87 s under 254 nm excitation (more than 25 s to the naked eye). Defects formed during the calcination process are associated with oxygen vacancies, which store the energy and are thought to be the origin of the afterglow. The as-prepared boric acid calcined product serves well as an afterglow material for anti-counterfeiting and time-resolved information protection.