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 six hours 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. • A highly efficient and photostable organic fluorophore was developed using a simple “twisted structure” design. • The fluorophore shows bright emission in both solution (QY = 94.4%) and solid state (QY = 95.2%). • SKOV-3 cell imaging and anti-counterfeiting application have been realized by using this fluorophore at very different concentrations.