Multilevel Information Encoding of Metal Ion-Induced Fluorescent Nanoaggregates and Full-Color Electrohydrodynamic Printing

Facing the significant challenges of information security, this work proposes an information encoding system based on the fluorescence properties of metal-ion-induced polystyrene-block-poly(acrylic acid) (PS–PAA) nanoaggregates (MIPAs), in which Eu3+, Tb3+, and Al3+ ions are embedded. By adding poly(vinylpyrrolidone) (PVP), red, green, and blue primary color inks are obtained. By precisely adjusting the ratio of cations, the control of photoluminescence (PL) intensity at different emission wavelengths is achieved, thereby obtaining a full-color fluorescent ink. Under the potential driving force in the nozzle of an electrofluidic inkjet printer, the ink can be printed onto a paper substrate and exhibit multiple fluorescent colors under ultraviolet (UV) irradiation. The printed fine image structures can carry encoded data. In these images, the multiple emission modes of fluorescent nanoaggregates induced by metal ions (Eu3+, Tb3+, and Al3+) can be combined with multiple quenching mechanisms. This will hopefully further improve the security of encoded information and the efficiency of information retrieval.