Reversible light-controlled fluorescence switch of block polymer-grafted carbon dots and cellular imaging.

Abstract

A novel type of aggregation-induced emission (AIE) nanoparticles, which are carbon dots (CDs) grafted with block polymer of tetraphenylethylene, spiropyran and <i>N</i>-isopropylacrylamide (CD-<i>g</i>-poly((TPE-<i>co</i>-SPA)-<i>block</i>-NIPAM)), was synthesized. The CD-<i>g</i>-poly((TPE-<i>co</i>-SPA)-<i>block</i>-NIPAM) nanoparticles can emit weak cyan fluorescence in tetrahydrofuran, while showing AIE-enhanced cyan fluorescence in water and solid film. The fluorescence of the CD-<i>g</i>-poly((TPE-<i>co</i>-SPA)-<i>block</i>-NIPAM) nanoparticles can reversibly transform cyan to red with UV/visible light irradiation, and functioned as a reversible fluorescence photoswitch. Importantly, the CD-<i>g</i>-poly((TPE-<i>co</i>-SPA)-<i>block</i>-NIPAM) nanoparticles have low cytotoxicity and, therefore, can be used for imaging in living cells.