Water‐Resistant SrAl₂O₄:Eu²⁺, Dy³⁺ Phosphor with Extended Afterglow Duration

Long afterglow phosphors are expected to find applications in biomedical imaging, security inks, and environmental monitoring, which typically involve aqueous environments. However, the current commercial phosphor, SrAl 2 O 4 :Eu 2+ ,Dy 3+ (SAOED), is susceptible to hydrolysis. To overcome this limitation, crystal field engineering is combined with surface modification to simultaneously enhance the chemical stability and afterglow performance of SAOED. By incorporating Sc 3+ doping and oxygen vacancies (V O ), a novel material, V O ‐SAOEDS is developed, which demonstrated a 19.07% increase in luminescence intensity and a 37.04% extension in afterglow duration. Further, coating this material with B 2 O 3 resulted in a highly chemically stable V O ‐SAOEDS@B 2 O 3 . After 30 days of immersion in water, this coated material retained 81.8% of its initial brightness. Compared to commercial SAOED, V O ‐SAOEDS@B 2 O 3 exhibits significant enhancements, including more than a tenfold improvement in water resistance, a 22.87% increase in afterglow duration, a 12.03% boost in luminous intensity, and an 8.97% enhancement in thermostability. This study paves the way for the broader application of long afterglow phosphors in water‐based systems.