Dual Functional Biocomposites Based on Polydopamine Modified Cellulose Nanocrystal for Fe³⁺-Pollutant Detecting and Autoblocking

In this work, a facile and sustainable strategy for ferric ion (Fe³⁺) detection was developed for the first time based on a coordination bonding between Fe³⁺ and polydopamine (PDA) modified cellulose nanocrystals (CNC) (PDA@CNC). PDA, as a probe molecule for Fe³⁺ detection, was <i>in situ</i> synthesized onto CNC template via one-pot oxidative polymerization of biological dopamine, yielding nanosized and well-dispersed PDA@CNC nanohybrid. When PDA@CNC met Fe³⁺, the coordination bonding between PDA and Fe³⁺ led to rapid agglomeration of PDA@CNC, resulting in macroscopical and flocculent PDA@CNC aggregates. Interestingly, this morphology transition of PDA@CNC enabled on-site detection of Fe³⁺ with a minimum limit of 3 ppm by the naked eye, which could be further optimized to 0.5 ppm using a dynamic light scattering method. Furthermore, we demonstrated another interesting application of the smart PDA@CNC biocomposites in automatic blockage of wastewater containing Fe³⁺. This easy and eco-friendly preparation method for dual functional PDA@CNC biocomposites provides a new strategy for Fe³⁺-pollutant detecting and autoblocking in a simple and sustainable way