Sunlight-driven photochromic hydrogel based on silver bromide with antibacterial property and non-cytotoxicity

A novel photochromic hydrogel system was designed and fabricated based on silver bromide and cuprous bromide in poly(hydroxyethyl acrylate-co-polyacrylamide) hydrogel matrix. The first time we overcome the atoms side reaction and migration of halides in opening hydrogel system to realize photochromism. Here, polyvinyl pyrrolidone (PVP) and glycerol were employed as a surfactant and sustainable co-solvent, respectively, whose synergistic effect make AgBr endows the hydrogel with photochromic stability and repeatability. The photochromic hydrogel can be changed reversibly between light-blue and brown color for least 15 times in air under a simulated solar light irradiation. Both UV–vis absorption (approximately 408 nm) and the valence states of the metal ions were studied and verified the conversion between Ag+ and Ag0. The process of color changing was studied and the fabricated hydrogel with a half-life fading period (t1/2) was 6.78 min under a simulated solar light irradiation. Reasonably, the as-fabricated photochromic hydrogel displayed remarkable antibacterial ability to both Gram-positive- and Gram-negative bacterium with the Ag ions in the system. Interestingly, due to the little dosage of AgBr and CuBr in the hydrogel, it also possessed excellent non-cytotoxicity property to L929 Mouse Fibroblast cells. Since its excellent photochromic and biological properties, the hydrogel has potential applications in the field of smart materials such as photochromic contact lenses, sensors and artificial intelligent devices or bionic skin.