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An efficient near-infrared (NIR) afterglow emission at over 750 nm is highly valuable for the advanced detection technology. Herein, a new kind of organic NIR afterglow system with persistent emission (0.16 s) at 808 nm is prepared by using a red room temperature phosphorescence (RTP) excimer as a donor and a NIR dye cyanine 7 (Cy7) as an acceptor. In the pyren-1-ylboronic acid@poly(vinyl alcohol) (PYB@PVA) system, its red persistent RTP emission at over 590 nm is proved to be derived from the triplet excimer of PYB. So, the bright NIR afterglow is achieved via only a single triplet-to-singlet Förster-resonance energy transfer process between PYB@PVA and Cy7. Moreover, PYB2@PVA with more triplet excimers is beneficial to improve NIR emission intensity with a quantum yield of 1.6%. This work demonstrates that exploiting triplet excimers is meaningful to develop purely organic red or NIR afterglow materials with the emission at a long wavelength. [ABSTRACT FROM AUTHOR]

The Förster resonance energy transfer (FRET) process has been utilized to construct host–guest systems with stimuli-responsive room-temperature phosphorescence (RTP). However, only two guests have been reported for these systems. Thus, the design of new guests and investigation of their molecular structural effects on their RTP properties has become an important and challenging work for improving their stimuli-responsive performance. In this work, a series of asymmetric diarylamine guests were designed and prepared for the DMAP host to construct host–guest systems, which exhibited stimuli-responsive RTP to heating, pressing, grinding and pH values; and it was revealed that the FRET process changes were the key to the stimulus-responsive RTP, by careful investigation. Interestingly, the host–guest system of DMAP/MDPA-Ph showed the best RTP performance, in which the T1h state of the host is close to the center between S1g and T1g states of the guest. Based on the time-resolved characteristics of RTP of these systems, anti-counterfeiting applications could be achieved through screen-printing or stamping processes. This work thus opened up a way to achieve excellent performance of stimulus-responsive RTP materials through molecular design of the guest. [ABSTRACT FROM AUTHOR]

Developing stable room-temperature phosphorescence (RTP) emission without being affected by moisture and mechanical force remains a great challenge for purely organic systems, due to their triplet states sensitive to the infinitesimal motion of phosphors and the oxygen quencher. We report a kind of highly robust phosphorescent systems, by doping a rigid phosphor into a copolymer (polyvinyl butyral resin) matrix with a balance of mutually exclusive features, including a rigidly hydrophilic hydrogen bond network and elastically hydrophobic constituent. Impressively, these RTP polymeric films have superior adhesive ability on various surfaces and showed reversible photoactivated RTP with lifetimes up to 5.82 seconds, which can be used as in situ modulated anticounterfeit labels. They can maintain a bright afterglow for over 25.0 seconds under various practical conditions, such as storage in refrigerators, soaking in natural water for a month, or even being subjected to strong collisions and impacts. These findings provide deep insights for developing stable ultralong RTP materials with desirable comprehensive performance.