Opal‐Inspired SiO ₂ ‐Mediated Carbon Dot Doping Enables the Synthesis of Monodisperse Multifunctional Afterglow Nanocomposites for Advanced Information Encryption

Abstract Despite recent advancements in inorganic and organic phosphors, creating monodisperse afterglow nanocomposites (NCs) remains challenging due to the complexities of wet chemistry synthesis. Inspired by nanoinclusions in opal, we introduce a novel SiO 2 ‐mediated carbon dot (CD) doping method for fabricating monodisperse, multifunctional afterglow NCs. This method involves growing a SiO 2 shell matrix on monodisperse nanoparticles (NPs) and doping CDs into the SiO 2 shell under hydrothermal conditions. Our approach preserves the monodispersity of the parent NP@SiO 2 NCs while activating a green afterglow in the doped CDs with an impressive lifetime of 1.26 s. Additionally, this method is highly versatile, allowing for various core and dopant combinations to finely tune the afterglow through core‐to‐CD or CD‐to‐dye energy transfer. Our findings significantly enhance the potential of SiO 2 coatings, transforming them from merely enhancing the biocompatibility of NCs to serving as a versatile matrix for emitters, facilitating afterglow generation and paving the way for new applications.