Redox-responsive, reversibly fluorescent nanoparticles from sustainable cellulose derivatives†
In comparison to single-stimuli responsive cellulose derivatives, multi-stimuli and reversibly responsive compounds from cellulose are still scarce. In this report, the fabrication of redox-controllable nanoparticles (NPs) from novel cellulose derivatives containing thiol groups and rhodamine spiroamide showing reversible fluorescence is described. The thiol groups were introduced into cellulose chains after esterification by 3,3′-dithiodipropionic acid and further reductive cleavage of disulfide bonds. Then, rhodamine spiroamide was immobilized via thiol–ene reaction between cellulose thiopropionyl ester and rhodamine B methacrylamide. The obtained cellulose derivative containing rhodamine spiroamide (cellulose-RhBMA) could be transformed into NPs in aqueous medium and dissolved again via redox reactions on thiol groups. At the same time, cellulose-RhBMA exhibited reversible fluorescence that could be switched using pH (protons) or UV-illumination/heating as external stimuli. In total, we demonstrated the fabrication of redox-controllable NPs with reversible fluorescence, and a novel platform for the chemical modification of cellulose via thiol–ene reaction.