Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE Phosphor-embedded nanocellulose-reinforced gum self-healing hydrogel was prepared. Maleic-cellulose nanocrystals were used as dispersing and reinforcing agents. UV-induced photoresponse was observed from transparent (365 nm) to green (517 nm). Persistent photoluminescence emission-driven anticounterfeiting was developed. Hydrogel prints displayed photostability, transparency, and mechanical reliability.

ABSTRACT
Optical inks have shown numerous drawbacks, such as high cost, poor efficiency, and weak durability. On the other hand, self-healing hydrogels can autonomously repair damage to restore their structural features, demonstrating stability and durability. Herein, a novel invisible hydrogel layer was developed using the principle of stamping films, capable of generating fluorescence emission under UV light and afterglow emission in darkness. This smart hydrogel was prepared by distributing nanoparticles of lanthanide aluminate (NLA) in a maleic-substituted cellulose nanowhisker-reinforced gum Arabic medium. The diameters of maleic-substituted cellulose nanowhiskers ranged from 5 to 14 nm, whereas NLA exhibited diameters between 41 and 109 nm. The resultant color-tunable and fluorescent hydrogel was applied to paper sheets. Colorimetric analysis of the paper surface verified the presence of a transparent layer. Photoluminescence spectroscopy revealed an excitation readout at 365 nm and an emission readout at 517 nm. The printed pattern was imperceptible in daytime, becoming green in UV light. All prints had shown reversibility without fatigue, displaying a colorless appearance in visible light, green fluorescence under UV rays, and greenish-yellow afterglow in the dark. The mechanical features of the imprinted sheets and the rheology of hydrogels were examined.