Triggering anti-Kasha organic room temperature phosphorescence of clusteroluminescent materials†

Abstract

Clusterization-triggered emission (CTE) from organic materials without π-conjugated structures for room temperature phosphorescence (RTP) is fascinating with extraordinary photophysical properties and diversified applications, but rather challenging in material design owing to the limited mechanism understanding. Here, we demonstrate a facile strategy to construct CTE polymers with stimuli-responsive emission, anti-Kasha RTP and organic ultralong RTP (OURTP) by introducing ions into the hydrolyzed nonconjugated maleic anhydride and acrylamide copolymers. Thanks to the synergistic effects of hydrogen and ionic bonding with the ion-triggered electrostatic and coordinate interactions to suppress non-radiative decays and promote intersystem crossing, the amorphous copolymers show efficient photoluminescence with quantum efficiencies up to 13.5%, anti-Kasha RTP blue-shift of 29 nm, and OURTP lifetime up to 420 ms. Moreover, the temperature-dependent and water-sensitive anti-Kasha RTP and OURTP are also observed due to the formation of highly emissive CTE structure regulated by ionization. With the excellent processability and flexibility of the copolymer, lifetime-, temperature- and color-encrypted information anti-counterfeiting is designed and explored. The anti-Kasha RTP in CTE materials realized for the first time demonstrates impressive potential for multi-level encryption/anti-counterfeiting applications and more importantly, providing fundamental mechanism understanding for the rational modulation and design of CTE materials with extraordinary photophysical properties.