Achieving Highly Robust Polymeric Microspheres with Efficient and Full-Color Organic Afterglow for 3D Printing and Anti-Counterfeiting.

In this work, highly robust polymer-based luminescent microspheres with efficient and full-color organic afterglow are developed for the first time. N-phenylnaphthalen-1-amine, N-phenylphenanthren-9-amine, and N-phenyltriphenylen-2-amine are employed as guest luminogens and embedded into melamine-formaldehyde polymer matrices with compact and permanent three-dimensional (3D) covalent networks via host-guest doping and emulsion polymerization. The resulting polymeric microspheres, with a diameter of ≈2 µm, show blue to yellow-green organic afterglow at room temperature. Excitingly, their phosphorescence quantum yields and lifetimes are up to 18.0% and 1.39 s, respectively, representing a breakthrough in comprehensive organic afterglow performance for polymer-based luminescent microspheres. Meanwhile, dual-mode organic afterglow and persistent red fluorescence with a lifetime of 0.24 s and a quantum yield of 22.2% are also achieved from the microspheres by simply replacing the guest luminogen and the phosphorescence resonance energy transfer approach, respectively. More importantly, the polymer-based organic afterglow microspheres exhibit outstanding resistance to water and organic solvents. Inspired by the efficient and highly robust organic afterglow, potential applications of the polymeric microspheres are demonstrated in stretchable elastomers, information anti-counterfeiting, 3D printing, and explosive detection. This work provides a universal strategy for developing polymeric microspheres with efficient, robust, and colorful organic afterglow.