Abstract
Owing to the advantages of cellulose such as exceptional biocompatibility and biodegradability, we synthesized cellulose-grafted bisindolyl methane (BIM) (1. Cell) composite. This biobased smart material was used as an effective colorimetric and fluorescent sensor for hypochlorite in the aqueous medium with a detection limit of 0.02 μM. Interestingly, cellulose exhibited inherent clusteroluminescence in solution, which was further intensified by the probe acting as a dopant. Both the boronic acid and bisindole groups in probe 1 are essential for this enhanced fluorescence, as boronic acid enables boronate ester formation with cellulose, while the bisindole groups facilitate additional hydrogen bonding interactions. This unique dual functionality produces a strong, solution-phase clusteroluminescent effect, creating a rigid microenvironment that promotes long-range exciton migration and an amplified fluorescence response. Furthermore, the 1. Cell exhibited ∼2.8-fold quenching, while probe 1 alone exhibited negligible fluorescence change in the presence of hypochlorite. Mechanistic investigation reveals that the probe formed a boronate ester via the interaction with cellulose, which was subsequently cleaved in the presence of hypochlorite. The differences in the response might be attributed to the distinct nature of their self-assemblies; 1. Cell could form long-range highly ordered aggregates, while probe 1 alone in the aqueous medium resulted in spontaneous random aggregates. Additionally, we employed cellulose paper strips to explore the practicability of the probe as a paper-based sensor. The chemically modified paper strips, grafted with probe molecules, were found to be stable for a week and could effectively detect hypochlorite in the presence of interfering analytes via the naked eye and fluorescent color-changing response.