Integrated Upcycling of Rice Straw into Electrospun Nanocellulose Chemiresistors and Lignin Nanoparticles with Superior Photoprotection

Abstract Open-field burning of rice straw, an abundant source of renewable biomacromolecules, remains a major environmental and public health concern. Herein, we report an integrated upcycling strategy that simultaneously valorizes rice-straw-derived cellulose and lignin into high-value functional nanomaterials. Microcrystalline cellulose is converted into nanocellulose (NC) and processed into electrospun nanofibers by incorporating rhodamine B (RhB) as a fluorescent dye. The resulting nonwoven fibrous network serves as a dual-mode sensor, selectively detecting CO2 gas over CH4 through its hydroxyl-rich network while modulating rhodamine B fluorescence in the presence of acidic vapors. In parallel, self-assembly of low-density lignin yields lignin nanoparticles (314 ± 66 nm) exhibiting broad-spectrum UV shielding and antioxidant activity (IC50 = 0.25 mg mL−1). Adding just 5 wt % lignin nanoparticles boosts sunscreen sun protection factor (SPF) from 32.5 to 104. Our work demonstrates a multi-product biorefinery approach for biomass valorization into value-added materials for environmental sensing and photoprotection.