A Dual-Functional Intelligent Felt-like Label from Cationic Rice Straw Fibers Loaded with Alizarin Red S for Monitoring Al(III) and the Freshness of Fish

To achieve dual functionality that can monitor both Al3+ levels in food and the freshness of fish, rice straw fibers (RSFs) were treated in NaOH solutions and then cationized with 2,3-epoxypropyltrimethylammonium chloride, onto which alizarin red S molecules were im- mobilized through electrostatic interaction to develop a smart felt-like label. An optimized treatment in 5 wt% NaOH solution effectively removed lignin and hemicellulose, facilitating quaternary ammonium group grafting and stable...