ε-Polylysine organic ultra-long room-temperature phosphorescent materials based on phosphorescent molecule doping

Abstract

Achieving long-lived room-temperature phosphorescence from pure organic amorphous polymers is attractive, and afterglow materials with colour-tunable and multiple-stimuli-responsive afterglow are particularly important, but only few materials with these characteristics have been reported so far. Herein, a facile and general method is reported to construct a series of ε-polylysine (ε-PL)-based afterglow materials with tunable colour (from blue to red) and long life. By doping guest molecules into ε-PL to obtain composite materials, the polymer matrix provides a rigid environment for luminescent groups, resulting in amorphous polymers with different RTPs. In this system, the materials even have impressive humidity-stimulated responses, and the phosphorescence emission exhibits excitation-dependent and time-dependent properties. The humidity-responsive afterglow is caused by the destruction of hydrogen bonds and quenching of triplet excitons. The time-dependent afterglow should stem from the formation of diversified RTP emissive species with comparable but different lifetimes. 9,10-diaminophene has Ex-De properties in the film doping state. With the change of excitation wavelength (254 nm to 365 nm), the emission wavelength shifts from 461 nm to 530 nm, accompanied by the change of emission colour from blue to green. In addition, the phosphorescence life of the film is the longest, up to 2504.7 ms, and the afterglow lasts up to 15 s, which is conducive to its applications in anti-counterfeiting and information encryption.