Yongtao Wang

The development of multifunctional purely organic room-temperature phosphorescence materials remains a formidable challenge. Herein, a pyridine-bromobenzene-based luminogen named NNPA was successfully prepared, integrating both aggregation-induced emission (AIE) activity and pH-dependent fluorescence emission. More importantly, the fluorescence emission maxima of NNPA exhibits a monotonic red shift with increasing water content in THF-H2O mixtures,enabling precise water quantification over a broad range (0-90%). Remarkable acid-triggered fluorescence emission shifts are demonstrated, transitioning from 383 to 520 nm in solution and 390 to 465 nm in the crystalline state. Meanwhile, the ultralong phosphorescence lifetime undergoes a monotonic attenuation with increasing acid concentration, allowing for time-resolved, naked-eye sensing of acid vapors. Crucially, by incorporating Rhodamine B via melt-blending, a red-shifted room-temperature phosphorescence system reaching 655 nm was constructed through a Förster resonance energy transfer (FRET) mechanism, effectively overcoming the inherent wavelength barrier of organic afterglow. Leveraging alcohol solubility and processability of NNPA, eco-friendly flexible afterglow papers were fabricated, enabling advanced information encryption including static covert codes, dynamic time-resolved decryption, and 3D stereoscopic anti-counterfeiting. This work not only elucidates the intrinsic mechanism of multifunctional NNPA but also paves the way for next-generation smart photonic materials.

Stress–strain responsiveness and visualization materials have considerable potential for information encryption, environmental sensing, and flexible optoelectronics. However, there still remain challenges in molecular design and understanding the intrinsic mechanism. Herein, two novel luminogens are designed and synthesized. They simultaneously exhibited TADF and RTP emissions in plastic polyvinyl chloride (PVC) and elastic styrene‐isoprene‐styrene block copolymer (SIS) doping matrices, accompanied by time‐dependent afterglow from blue to green. The high‐contrast stretchable and stress–strain responsiveness and visualization behaviors are achieved for the two luminogens in PVC and SIS matrices. Noteworthy, 1% AN‐CN@PVC and 1% AN‐NH ₂ @PVC films showed continuously decreasing RTP intensity and lifetime, as well as increased RTP‐to‐TADF intensity ratio with the increase of elongation, with the lowest strain detection limits of 13.19% and 5.84% in turn. This work not only obtained new long‐lived TADF and RTP materials, achieved multi‐color dynamic afterglow, strain detection and visualization, advanced anti‐counterfeiting, and high‐contrast stretchable behaviors, but also can be expected to provide more inspirations and possibilities for using TADF and RTP materials in a more cutting‐edge field, as well as theoretical guidance and experimental supports for further molecular designs.

Long afterglow luminogens with thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) emissions have important value in achieving a dynamic afterglow and exploring the intrinsic mechanism of phosphorescence. Therefore, based on different electron substitution effects, we designed and successfully prepared six host and guest materials and constructed and studied their host-guest doping systems. The doping systems present doping concentration and host-dependent TADF and RTP. Noteworthy, the host-guest doping system with an electron donating substituent group shows the longest RTP lifetime (1270 ms) and afterglow durations (11 s). Subsequently, four ternary doping systems were constructed based on Förster resonance energy transfer (FRET), with long-lived red and white afterglows, lasting for 6 and 11 s, respectively. In poly(methyl methacrylate) (PMMA), three guests give obvious TADF and RTP emissions. The maximum TADF and RTP lifetimes can reach 514 and 843 ms, respectively, corresponding to fluorescence, TADF, and RTP quantum yields of 0.17, 0.10, and 0.22, respectively, as well as afterglow durations of over 10 s in turn. Based on crystal analysis and theoretical calculations, the internal mechanisms of TADF and RTP are revealed. This work not only achieves long-lived red, white, and dynamic afterglows, high-level anticounterfeiting, and digital information encryption but also offers important theoretical insights into TADF and RTP emission mechanisms. It holds significant implications for advancing the applications of long afterglow materials in fields such as visual temperature detection, illumination, and encryption.