Rational design of uniform SiO₂-based afterglow microparticles for photonic crystals

Despite recent advancements in organic phosphors, the synthesis of monodisperse afterglow microparticles (MPs) suitable for creating photonic crystals remains challenging. The SiO₂ matrix is an attractive host material for activating the long-lived emissions of doped molecules due to several factors, including its cross-linked polymer-like structure, abundance of -OH groups, robustness, and presence of numerous emitter defects. However, the Stöber method struggles to produce monodisperse molecule-doped SiO₂ MPs due to the complexity of the system. Our reported pseudomorphic transformation-assisted doping method shows promise in addressing this issue by using monodisperse SiO₂ MPs as parent materials in the presence of dopants under hydrothermal conditions. This method offers flexibility in controlling the optical properties of the resulting monodisperse molecule-doped SiO₂ MPs. The uniformity allows for the assembly of afterglow SiO₂ MPs into photonic crystals, which demonstrate not only afterglow but also angle-dependent structural colors. Furthermore, adjusting the match between the stopband of the photonic crystals and the emission bands of the doped molecules presents additional opportunities to tune the optical properties of the assemblies. Our findings significantly expand the applications of afterglow materials in fields such as information storage and anticounterfeiting.