High-contrast mechano-responsive luminescence (MRL) materials with mechano-induced emission enhancement properties are fascinating candidates but few, for applications in rewritable media and recording devices.Here, an interesting design strategy of "Y-shape" donoracceptor (DÀ A) type molecules for high-contrast MRL materials was presented, based on substituted diphenylamine donor and planar acceptor. Interestingly, their DÀ A torsion angles are small in crystals but increased after ground, resulted in planar and twist intramolecular charge transfer (PICT and TICT) states, respectively. Therefore, high-contrast MRL switching between weak blue (450 nm) fluorescence and bright yellow (552 nm) thermally activated delayed fluorescence (TADF) can be achieved for compound TXDO (4,4'-dimeth-oxydiphenylamine donor), which photoluminescence quantum yield increased from 2.8 % to 54.7 % after ground. Most importantly, the two independent DÀ A conjugation dihedral angles are actually independent in the "Y-shape" molecules. Especially for compound TXDT (4,4'-di-tert-butyldiphenylamine donor), its crystal exhibited both PICT and TICT processes inside, resulted from the different dihedral angles of 11.8°and 35.5°, respectively. The TXDT crystal thus showed dual-peak emission, including both TICT fluorescence and PICT room-temperature phosphorescence. Therefore, this strategy of "Y-shape" DÀ A type molecules provide a new approach to design advanced luminescent materials with mechano-induced TADF feature, for high-contrast MRL and single-component white luminescence.
Organic persistent luminescence (pL) systems with photoresponsive dynamic features have valuable applications inthe fields of data encryption, anticounterfeiting, and bioimaging. Photoinduced radical luminescent materials have a unique luminous mechanism with the potential to achieve dynamic pL. It is extremely challenging to obtain radical pL under ambient conditions; on account of it, it is unstable in air. Herein, a new semialiphatic polyimide-based polymer (A0) is developed, which can achieve dynamic pL through reversible conversion of radical under photoexcitation. A "joint-donor-spacer-acceptor" molecular design strategy is applied to effectively modulate the intramolecular charge-transfer and charge-transfer complex interactions, resulting in effective protection of the radical generated under photoirradiation. Meanwhile, polyimide-based polymers of A1-A4 are obtained by doping different amine-containing fluorescent dyes to modulate the dynamic afterglow color from green to red via the triplet to singlet Förster resonance energy-transfer pathway. Notably, benefiting from the structural characteristics of the polyimide-based polymer, A0-A4 have excellent processability, thermal stability, and mechanical properties and can be applied directly in extreme environments such as high temperatures and humidity.
Host–guest doping systems with phthalimides (BI) and N-methylphthalimide (NMeBI) as
the host and 1,8-naphthalimide (NI) and 4-bromo-1,8-naphthalimide
(4BrNI) as the guest have been developed. The 0.2% NI/BI (molar ratio) with a strong C=O···H–N
hydrogen bond exhibited a phosphorescence quantum efficiency (29.2%)
higher than that of NI/NMeBI with a weak C=O···H–C
hydrogen bond (10.1%). A similar trend was observed in the 4BrNI guest system. A remarkable phosphorescent efficiency of 42.1% was
achieved in a 0.5% 4BrNI/BI composite, which represents
the highest value in NI-based phosphors. This research
indicates stronger hydrogen bonding may have a greater contribution
in boosting the phosphorescence efficiency.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.