Organic fluorophores with high photostability and strong emission in both solution and solid state

Abstract

Realizing highly efficient emission of organic fluorophores in both solution and solid state still represents a challenging task, due to either aggregation-caused quenching (ACQ, requiring relatively low working concentration) or aggregation-induced emission (AIE, requiring relatively high working concentration). Herein, we report a highly efficient fluorophore consisting of a pyrido [1,2-a]benzimidazole core and a simple twisted phenyl substituent. The planarity of pyrido [1,2-a]benzimidazole ensures the conjugation thus achieving strong emission in dilute solution (quantum yield: 94.4%). Meanwhile, the π-π stacking induced fluorescence quenching is blocked by the twisted phenyl ring, which leads to efficient emission in the solid state (quantum yield: 95.2%). The compound exhibits high photostability as evidenced by minimal loss of the fluorescence even after 6 h of continuous irradiation in air. More importantly, SKOV-3 cell imaging and anti-counterfeiting application have been realized by using this fluorophore at very different concentrations. Such “twisted structure” design would open new possibilities for development of high-efficiency robust organic fluorophores that can function under a wide range of conditions.