Reversible polymerization of carbon dots based on dynamic covalent imine bond.

Carbon dots (CDs), as new type of carbon-based nanoparticles, are considered to be an aggregate with irreversible polymerization. Achieving the reversible tunability of CDs luminescence based on their reversible polymerization is a challenging subject. Herein, we, for the first time, design and construct the blue-emitting CDs with reversible polymerization by a room-temperature Schiff base reaction between tannic acid and ethylenediamine. The formation of CDs is proven to be due to the crosslinking polymerization of precursors caused by imine bond. As a dynamic covalent bond, imine bond endows CDs with controllable structural transformation properties, and the prepared CDs can be depolymerized and polymerized reversibly by pH-controlled imine bond cleavage and re-formation. These properties of reversible fluorescence photoswitching make the CDs have a good application prospect in reversible information encryption.