Sonication-Responsive Organic Afterglow Emulsions

In contrast to their fluorescence counterparts, stimuli-responsive organic afterglow materials display distinct advantages to function normally in the presence of strong fluorescence background. However, most of the stimuli-responsive afterglow materials can only work in their solid states with those in aqueous medium being rarely reported. In addition, the types of these materials are limited to mechanical force-, pH-, ion-, and temperature-responsive ones. Here, a serendipitous finding of sonication-responsive organic afterglow emulsions in aqueous medium is reported. The afterglow emulsions are produced by dopant-matrix strategy and emulsion technique. In-depth studies reveal that the key to achieve the sonication responsiveness is the selection of a specialized organic matrix that can form microcrystalline particles in aqueous medium with the aid of surfactants. In matrix's microcrystalline state, the triplet excited states of luminescent dopant within the matrix can be protected to exhibit room-temperature afterglow. Under sonication, matrix's microcrystalline structure can be disrupted and consequently the triplet excited states of luminescent dopants lose protection to show afterglow quenching. To the best of the authors' knowledge, this study represents the first report of sonication-responsive afterglow materials in aqueous medium, which show promising biomedical applications.