Citric Acid/Cysteine-Modified Cellulose-Based Materials: Green Preparation and Their Applications in Anticounterfeiting, Chemical Sensing, and UV Shielding

Functionalized cellulose-based materials are in high demand for many applications. In this work, we report a green approach to fabricate a type of versatile cellulose-based material through facile citric acid/cysteine treatment. For its preparation, cellulose-based materials were conjugated with citric acid/cysteine-based fluorophores (CCFs) by simply soaking them in a concentrated citric acid/cysteine aqueous solution followed by drying above 80 °C. Chemical modification occurred, which was completed in the swollen state of the cellulose, and the highest conjugating ratio reached 1.6 wt %. It was noted that the treatment had no effect on the crystallinity of the cellulose while the structural morphology of various cellulose-based components in the material was maintained. We also found that the CCF-modified cellulose-based products had remarkable fluorescence, a selective quenching ability toward chloride ions, and excellent UV absorption capacity. Thus, they could have new applications in anticounterfeiting, chemical sensing, and UV shielding. Furthermore, our developed route to fabricate these CCF-modified cellulose-based products was environmentally friendly since water was the only solvent, and no organic solvent was involved throughout the procedures.