Pyrene-based water dispersible orange emitter for one- and two-photon fluorescence cellular imaging

A water-dispersible orange emitter (Pyrene4BTF–PEG–TAT) containing pyrene as the donor core and benzothiadiazole as the acceptor is synthesized through click chemistry for one- and two-photon fluorescence imaging application. Pyrene4BTF–PEG–TAT has an emission maximum at 586 nm in water with a large Stokes shift of 181 nm. It self-assembles into nanoparticles with diameters of ∼190 nm in water. The nanoparticles have a fluorescence quantum yield of 0.11 and a two-photon absorption (TPA) cross-section of 512 GM at 820 nm based on molecule. Pyrene4BTF–PEG–TAT could be effectively internalized by HeLa cells to show bright red fluorescence upon both one- and two-photon excitation. The successful demonstration of the first water-dispersible pyrene-based TPA material will trigger more research on developing red emitters for bioimaging applications.