Excited-state geometry relaxation of pyrene-modified cellulose nanocrystals under UV-light excitation for detecting Fe 3

Capturing and detecting Fe 3+ ions in aqueous solution is of great significance in biological systems as well as the water treatment industry. Herein, pyrene-modified cellulose nanocrystal (CNC-1-Pyr) acting as a fluorescent probe was prepared by a one-step esterification reaction, which shows geometry relaxation under UV-light excitation. Experiments and density functional theory-based simulations revealed that the structural geometry relaxation is controlled by the electron excitation and fluorescence emission. The S1 state of CNC-1-Pyr provides a conformation match for coordination with Fe 3+ under the excitation of UV light, facilitating the detecting and capturing of Fe 3+ efficiently.