Recent advances in cellulose-based dual-mode colorimetric and fluorescent sensors for anions sensing: A review.

Anion contamination in aqueous and environmental systems poses severe threats to ecological balance and human health, necessitating the development of low-cost, eco-friendly, and high-performance sensing platforms for rapid and accurate anion detection. Dual-mode colorimetric and fluorescent sensors integrate the intuitive visual readout of colorimetric and fluorescent sensing. Among biopolymers, cellulose is an inexpensive/low cost raw material with many functional groups, which can be modified into wide range sensing materials. This review systematically summarizes the latest research progress of cellulose-based dual-mode colorimetric/fluorescent sensors targeting common harmful anions in recent years. It comprehensively discusses the mainstream fabrication strategies of functionalized cellulose sensing materials, including physical loading, chemical grafting and composite modification, and elaborates the dual sensing mechanisms for anions, based on photoinduced electron transfer, hydrogen bonding interactions and specific anion recognition reactions, focusing on key indicators such as detection limit, response time, selectivity and stability. Based on the structured literature search, and to the best of our knowledge, this is the first review devoted specifically to cellulose-derived colorimetric and fluorescent anion sensors and organized on anion-by-anion basis. This review aims to provide a comprehensive reference and insightful guidance for the rational design and engineering of high-performance, cellulose-based sensing materials for anion monitoring.