Stimuli-Responsive Organic Ultralong Phosphorescent Materials with Complete Biodegradability for Sustainable Information Encryption

Constructing eco-friendly stimuli-responsive phospho-rescence materials remains challenging and fascinat-ing. Herein, we use natural cellulose as the raw material to prepare pH-responsive room-temperature phos-phorescent (RTP) materials with excellent biode-gradability by introducing anionic structures. The introduction of a phenylcarboxylate substituent not only promotes intersystem crossing but also brings about electrostatic-attractive and strong hydrogen-bonding interactions, which enhance the intermolecu-lar chain interactions. Therefore, the obtained anionic cellulose derivatives containing phenylcarboxylate groups exhibit ultra-long RTP. More intriguingly, these cellulose-based phosphorescent materials have a dis-tinctive pH-responsive behavior. Under acidic condi-tions, the carboxylate is converted into the carboxylic acid, resulting in phosphorescence quenching. This process is reversible. Moreover, the obtained cellulose-based phosphorescent materials have excellent pro-cessability and can be easily processed into various material forms, such as film, coating, and pattern, by using eco-friendly aqueous solution processing strate-gies. Such proof-of-concept biomass-based phospho-rescent materials with unique pH-responsive behavior and excellent processability have a huge potential in information encryption, advanced anti-counterfeiting, and food monitoring.