Dynamic Photochromic Polymer Nanoparticles Based on Matrix-Dependent Förster Resonance Energy Transfer and Aggregation-Induced Emission Properties.

Dynamic color-tunable fluorescent materials are sought-after materials in many applications. Here, we report a polymeric matrix-regulated fluorescence strategy via synergistically modulating aggregation-induced emission (AIE) properties and the Forster resonance energy transfer (FRET) process, which leads to tunable dynamic variation of color and photoluminescence (PL) intensity of fluorescent polymeric nanoparticles (FRET-PNPs) driven by photoirradiation. The FRET-PNPs were prepared via a facile one-pot miniemulsion copolymerization with the tetraphenyletheyl (TPE) and spiropyran (SP) units chemically bonded to the polymer matrix. The FRET-PNPs exhibited dynamic variation of fluorescence properties (colors and PL intensity) under photoirradiation on the timescale of minutes. The variation of the polymer matrix composition could deliberately influence the AIE property of TPE units and the isomerization process of SP to merocyanine units, which further affect the FRET efficiency of FRET-PNPs and, eventually, lead to versatile dynamic fluorescence variation. The dynamic fluorescence property as well as the excellent processability and film formation ability of FRET-PNPs allowed for diverse applications, such as warning labels, dynamic decorative painting, and multiple information encryption. Without sophisticated molecular design or tedious preparation processes, a new perspective for the design, fabrication, and performance optimization of fluorescent nanomaterials for innovative applications was proposed.