Light and Ferric Ion Responsive Fluorochromic Hydrogels with High Strength and Self-healing Ability
Here, light and ferric ion (Fe3+) responsive fluorochromic hydrogels with high strength and self-healing ability were designed and fabricated. The hydrogel was prepared via physical crosslinking of poly(vinyl alcohol) (PVA), in the presence of γ-cyclodextrin-spiropyran (γ-CD-SP) and tannic acid (TA). By utilizing the hydrogen bonding interaction between the γ-CD moiety and PVA chain, the fluorophore γ-CD-SP could be incorporated into the PVA gel successfully. Owing to photo-isomerization of the SP moiety, the hydrogel showed “on/off” fluorescence behavior upon ultraviolet/bright light irradiation. Moreover, the fluorescent emission of the hydrogel could also be turned off in the presence of Fe3+, by fluorescence inner filter effects, and then recovered by adding EDTA. The hydrogel possessed high tensile strength (i.e. 2.18 MPa) as well as self-healing ability. With the features of high strength, self-healing, tunable fluorescent properties, the hydrogels would have potential applications in wearable device, fluorescence sensors, and optical switches.