Light-responsive smart nanopapers and ink: design for information storage and encryption

Abstract

In the present study, spiropyran (SP)-like photoactive molecules were embedded in situ into cavities of lanthanide metal–organic frameworks (Ln-MOFs), resulting in individually aligned molecules to generate dynamically photo-responsive materials (Ln-MOFs@SP). To realize the practical application of Ln-MOFs@SP, we developed a series of light-responsive smart materials, including a nanopaper (Ln-nanopaper@SP) and inks (Tb-PU-ink@SP and Tb-PEG-ink@SP). The ultrasensitive light-coloring effect of nanopapers allowed erasing under ultraviolet and white light, suggesting the potential use of these nanopapers for information storage. Based on the written and printable characteristics of ink, multi-channel, cross-disciplinary information encryption and decryption of invisible two-dimensional (2D) codes, fluorescent 2D codes, and fluorescent 3D codes were achieved by building multicolour modular 2D codes. In addition, the Tb-PU-ink@SP ink was printed on various complex surfaces, expanding the potential applications of this ink.