Color-Tunable Room Temperature Afterglow of Non-Conventional Organogels for Dynamic Anti-Counterfeiting

Low-molecular-weight organogels with ultra-long room temperature phosphorescent (RTP) are ideal materials for dynamic anti-counterfeiting, due to their sensitive thermal-responsive character. However, it is a great challenge to realize ultra-long RTP in a single-component organogel because conventional auxiliary groups for the promotion of gel formation are usually flexible, which increases non-radiative decay through molecular motions to quench the RTP. Non-conventional organogelators with rigid chemical structures may be able to alleviate the non-radiative decay to maintain the phosphorescent characters in the gel state like in the crystalline state. In this work, potential low-molecular weight phosphorescent organogelators with rigid chemical structures are predicted by using the descriptors derived from all-atom molecular dynamics simulation, and successfully screen out two RTP non-conventional organogelators. It is exciting that one of them exhibited ultra-long RTP in the gel state. Furthermore, triplet-to-singlet Forster resonance energy transfer between the RTP gelator (donor) and fluorescent sulforhodamine 101 (SR101) (acceptor) in the gel state provided a long-lived red fluorescence. Due to the sensitive thermal-responsive property of organogel, the afterglow can be well switched between "on" and "off" with excellent fatigue-resistant properties, which is promising for dynamic anti-counterfeiting. Two non-conventional organogelators with room temperature phosphorescence are successfully developed and ultra-long afterglow emission is observed in the gel state for the first time. Through triplet to singlet Forster resonance energy transfer from the phosphorescent gelator m-PBCM to fluorescent sulforhodamine 101 (SR101) dye, long-lived red fluorescence is achieved, showing promising application in dynamic anti-counterfeiting.image