Phototunable Full-Color Emission of Cellulose-Based Dynamic Fluorescent Materials

An iridescent chameleon-like material that can change its colors under different circumstances is always desired in color-on-demand applications. Herein, a strategy based on trichromacy and the dynamically tunable fluorescence resonance energy transfer (FRET) process to design and prepare these chameleon-like fluorescent materials is proposed. A set of trichromic (red, green, and blue), solid fluorescent materials are synthesized by covalently attaching spiropyran, fluorescein, and pyrene onto cellulose chains independently. After simply mixing them together, a full range of color is realized. The chameleon-like nature of these materials is based on the dynamic tunable FRET process between donors (green and blue) and acceptors (red) in which the energy transfer efficiency can be finely tuned by irradiation. Ultimately, the reversible and nonlinear regulation of fluorescence properties, including color and intensity, is achieved on a timescale recognizable by the naked eye. Benefited by the excellent processability inherited from the cellulose derivatives, the as-prepared materials are feasibly transformed into different forms. Particularly, a fluorescent ink with the complicated fluorescent input-output dependence suggests more than a proof-of-concept; indeed, it suggests a unique method of information encryption, security printing, and dynamic anticounterfeiting.