A crosslinking confined charge-transfer complex for the construction of photo-responsive hydrogels

The development of charge-transfer (CT) complexes offers promising applications in optical switches and memories, yet stably integrating them into optical hydrogel systems remains a significant challenge. In this work, 1,8-naphthalimide (NA) is employed as an acceptor and confined within an organosilicon network to form zero-dimensional NA doped organosilicon nanoparticles (NASiNPs) via a crosslinking process. The formation of a CT complex can be effectively triggered by UV irradiation in solution. Simultaneously, the intrinsic blue emission from an excited singlet state is largely quenched and a faint reddish emission originating from the CT complex is observed. We reveal that non-covalent interactions between NA and the organosilicon network induce a CT complex-like state upon photo-excitation. Benefiting from the Si-O-Si confined structure, the optimal distance between the donor and acceptor species endows the CT emission with robust photo-stability. Hydrogen bonding between polyvinyl alcohol (PVA) and NASiNPs leads to the establishment of hydrogels with photo-responsive optical and excellent mechanical properties. The resulting system exhibits green CT emission (λ_em: ∼525 nm, lifetime: ∼14 ns), exceptional mechanical performance (elastic strain up to 475%), and high self-healing efficiency (∼92%). This study provides an effective strategy for producing UV-light-driven photoswitches, offering new opportunities for the development of innovative hydrogel materials.