Tough, Self-Healing, and UV Light-Switchable Luminescent Hydrogels with Reversible Stimuli-Responsive Properties for Cu²⁺

Stimuli-responsive luminescent hydrogels (LHs) are of great potential for applications in advanced luminescent sensors; however, structural optimizations and challenges in implementation still remain in their practical applications. Herein, we reported a promising and cooperative strategy to prepare smart LH actuators. Lanthanide(III)-based complexes (LnCs) and sulfur quantum dots (S-QDs) in this contribution are constructed in a cooperative manner; that is, (1) a noncovalent hydrogen bonding model between polyethylene glycol (PEG) in S-QDs and polyurethane (PU) endows LHs with interwoven double networks and improved the mechanical properties and (2) LnCs and S-QDs are two excellent emitting centers with different luminescent excitation properties, leading to the modulating emission colors of LHs by varying the UV irradiation between 254 and 365 nm. Meanwhile, the resultant LHs containing 3.26 wt % of PU possess good mechanical performance and self-healing capability. As a proof of application in stimuli response, our LHs can be served as a ratiometric luminescence probe to electively detect Cu 2+ via exponentially correlating the emission intensity ratio of LnCs and S-QDs to the Cu 2+ concentration. Remarkably, the obtained LHs also show reversible luminescence “On/Off” switch upon alternate exposure to Cu 2+ /glutathione (GSH) under 254 nm, while no obvious luminescent variation is observed under 365 nm.