Efficient Visible Light Activated Afterglow Through Stabilizing Excited Dimers Via a Melt‐Injection Reaction for Multiple Applications

Abstract Achieving efficient and long‐lasting afterglow that can be activated by visible light remains challenging. In this work, a melt‐injection strategy is proposed for the synthesis of afterglow materials. Excitingly, the afterglow materials can be excited by visible light with a wavelength of up to 500 nm, achieving a photoluminescence quantum yield of 25.6%. The efficient and visible light‐excited afterglow is attributed to a matrix‐stabilized dimers mechanism. Specifically, injection of formaldehyde into melt urea initiated the formation of urea‐formaldehyde (UF) matrix. Phenanthroline is incorporated into this matrix in the form of dimers, which caused a red‐shift in the absorption and excitation spectra of phenanthroline into the visible light range. Aided by hydrogen and chemical bonding, cross‐linking networks are established between the UF matrix and the phenanthroline dimers. These networks further reduce the energy gaps between the singlet and triplet states, promote the intersystem crossing processes, and stabilize the excitons from quenching. This research offers novel insights into the design of visible‐light‐activated afterglow materials, which show great potential in information security and bio‐imaging.