Molecular Engineering of Plant Polyphenols into Amorphous Room‐Temperature Phosphorescent Materials

Room‐temperature phosphorescent (RTP) materials have potential applications in optoelectronics and bioimaging but encounter significant challenges. Traditional heavy‐metal‐based and crystalline systems are often toxic and environmentally sensitive, while strategies involving host–guest doping and encapsulation frequently suffer from phase separation and limited controllability–ultimately resulting in poor repeatability and restricted applications. Here, we developed a novel polyphenol‐mediated molecular splicing and ring‐locking strategy to incorporate benzo[c][1,2,5]thiadiazole (BZT) into polyphenol molecules, yielding a range of eco‐friendly and processable amorphous single‐component systems with a lifetime of up to 124 ms. Experimental and calculational analyses confirm that phosphorescence arises from synergistic interactions between polyphenol and BZT. Furthermore, phosphorescent nanoparticles (NPs) were synthesized via nanoprecipitation in tetrahydrofuran with 30% water content. These well‐dispersed, metal‐free NPs demonstrate excellent biocompatibility and low cytotoxicity, facilitating time‐resolved luminescence imaging with minimal background fluorescence interference both in vitro and in vivo. This research establishes a versatile and sustainable design strategy for developing high‐performance amorphous RTP materials using plant polyphenols, offering promising prospects for advanced biomedical applications.