Ultralong colorful sodium alginate-based room temperature phosphorescence materials with heat-resistance, flexibility and easy large-area preparation

Ultralong colorful organic room temperature phosphorescence (RTP) materials combining heat-resistance, flexibility and large-area preparation are of great significance for their fabrication, processing and application. However, developing polymer-based RTP materials with above properties still faces daunting challenges. Herein, a sodium alginate (SA)-based binary doping system SA-H 2 NDC is developed by doping 2,6-naphthalic acid (H 2 NDC) into SA matrix, which demonstrates ultralong RTP with a lifetime of up to 877 ms and a bright green afterglow persisting for 8 s under ambient condition. A ternary doping system SA-H 2 NDC-R6G further achieves persistent delayed fluorescence with emission peak centered at a longer wavelength of 600 nm via triplet-to-singlet Förster resonance energy transfer (TS-FRET). Inspiritingly, SA-H 2 NDC-R6G shows time-dependent tunability of afterglow color. Significantly, the phosphorescence of SA-H 2 NDC and SA-H 2 NDC-R6G presents excellent heat-resistant properties in a temperature range from 298 to 353 K. Furthermore, large-area flexible SA-based RTP films are conveniently prepared by a simple doping-coating-drying process. The excellent optical and mechanical properties of SA-based RTP materials enable their successful applications in flexible display and advanced information encryption. This work expands the scope of ultralong polymer-based phosphorescence materials with heat-resistant luminescence, and provides a new avenue for developing large-area flexible colorful RTP materials.