Synthesis of fluorescent probes based on cellulose for Fe2+ recognition

Abstract As the plentiful and easily accessible natural polymer, cellulose is insoluble in most organic solvents. Improving the solubility of cellulose is necessary. In this work, cellulose-based fluorescent probes were prepared by chemical modification, and they could be dissolved in organic-water mixed solvent. The obtained cellulose based fluorescent probes could selectively recognize Fe 2+ in H 2 O/DMSO (1:2, v/v) or H 2 O/DMF (1:2, v/v) system. Firstly, through the esterification reaction between −OH on cellulose and acryloyl chloride, cellulose derivatives with −C = C were prepared. Secondly, via thiol-ene click reaction between −C = C on cellulose and −SH on cysteamine, −NH 2 groups at the chain ends are attached to cellulose. At the same time, three small molecular derivatives (N1, N2, N3) from 4-bromo-1,8-naphthalene anhydride were synthesized. Finally, the reaction between –NH 2 on cellulose and –CO–O–CO– on 4-bromo-1,8-naphthalene anhydride derivatives occurred readily. By this method, three cellulose-based fluorescent probes (CN1, CN2, CN3) were prepared successfully. These as-prepared fluorescent probes could be easily dissolved in H 2 O/DMSO or H 2 O/DMF mixed solvents. Fluorescence detection measurements indicate that the probes could selectively detect Fe 2+ . The fluorescence is quenched after the probes contacting with Fe 2+ , which are turn-off fluorescent probes. In addition, the prepared probes could be fabricated into cellulose membrane by a simple method for portable detection of Fe 2+ . The prepared cellulose-based fluorescent probes could be used as macromolecular sensors for Fe 2+ detection, and could be processed into cellulose-friendly materials, which are expected to be used in environmental systems. Graphical abstract