Manipulation of dual fluorescence behavior in aggregation-induced emission enhancement of a tetraphenylethene-appended polymer by optical tweezers

Abstract

The manipulation of dual fluorescence behavior in aggregation-induced emission enhancement (AIEE) of a tetraphenylethene (TPE)-appended polymer by optical tweezers was investigated herein. Optical tweezers using a focused near-infrared continuous-wave laser resulted in the generation of a single micrometer-sized aggregate consisting of polymers at the laser focus. After a few minutes, AIEE was activated, and green fluorescence emission was observed at 530 nm. Continuous irradiation into the aggregate led to the formation of a highly concentrated solution of polymers around the aggregate, the fluorescence of which changed from green to blue. The blue solution exhibited two fluorescence emissions at 457 and 530 nm, and their intensity depended on the distance from the laser focus. The two fluorescence ratios could be arbitrarily regulated by tuning the laser power, indicating that optical tweezers could enable arbitrary control of the fluorescence position. Optical tweezers controlled the local environment around the fluorophore and provided various polymer associations, resulting in dual fluorescence emissions. The dynamics and mechanism of dual AIEE fluorescence by optical tweezers were examined in terms of polymer association and change in the fluorophore conformation depending on the laser power.