Cellulose Nanofiber/Polyvinyl Alcohol-Based pH-Responsive Films Containing Anthocyanin and Carbon Dots

Environment-responsivefluorescent materials have been widely studiedin the determination and utilization of different environmental factors.Particularly, it is still challenging to develop multifunctional environment-friendlypH-responsive fluorescent materials based on biomass and renewablepolymers. In this study, a pH-responsive intelligent color-changingfluorescent film based on cellulose nanofibers (CNFs)/polyvinyl alcohol(PVA) incorporated with anthocyanin (Ant) extracted from the Lycium ruthenicum fruit and amino-functionalizedcarbon dots (CO-CDs) was prepared. Due to the influence of Ant andCO-CDs, the mechanical properties, oxidation resistance, and UV resistanceare obviously promoted. Under different pH conditions, the compositefilm exhibits obvious pH-dependent color change and fluorescence colorchange. Its fluorescence intensity ratio (F (550)/F (450)) varies linearly with pH at 1-6and 6-13. Thereby, qualitative and quantitative perceptionof environmental pH change can be realized by using the compositefilm. In food trial, with the extension of shrimp storage time, boththe visual color and fluorescence emission color of the film changeevidently. The film can delay deterioration. The Ant/CO-CDs/CNF-PVAfilm, as a pH-responsive smart color-changing fluorescent film, hasa potential application value in the fields of intelligent packaging,agriculture, and pH sensing.