A novel method to prepare water-soluble cellulose-based fluorescent probes for highly sensitive and selective detection and removal of Hg2+/Hg22+ ions

Abstract

Improving the water solubility of natural product cellulose and using it to treat heavy metal ions is very important. In this work, cellulose-based fluorescent probes containing BODIPY fluorophore were synthesized by simple chemical method, which realized the selective recognition and removal of Hg2+/Hg22+ ions in an aqueous system. Firstly, fluorescent small molecule (BOK-NH2) bearing -NH2 group was synthesized through Knoevenagel condensation reaction between BO-NH2 and cinnamaldehyde. Secondly, via the etherification of -OH on the cellulose, substituents bearing -C ≡ CH groups with different lengths at the end are grafted on the cellulose. Finally, cellulose-based probes (P1, P2, and P3) were prepared by amino-yne click reaction. The solubility of cellulose is improved greatly, especially the cellulose derivative with branched long chains has excellent solubility in water (P3). Benefiting from the improved solubility, P3 could be processed into solutions, films, hydrogels, and powders. Upon the addition of Hg2+/Hg22+ ions, the fluorescence intensity enhanced, which are “turn-on” probes. At the same time, the probes could be utilized as efficient adsorbents for Hg2+/Hg22+ ions. The removal efficiency of P3 for Hg2+/Hg22+ is 79.7 %/82.1 %, and the adsorption capacity is 159.4 mg·g−1/164.2 mg·g−1. These cellulose-based probes are expected to be employed in the treatment of polluted environments.