Diketopyrrolopyrrole-doped hybrid FONs as two-photon absorbing and dual-emission fluorescent nanosensors for Hg2+

Fluorescent organic nanoparticles (FONs) with dual-emission and two-photon fluorescence emission are promising sensing tools. In this work, novel hybrid FONs with two-photon absorption and dual-emission properties were used to detect Hg2+. The FONs were prepared by the co-self-assembly of amphiphilic furyl diketopyrrolopyrrole (DPP1) and tetraphenylethylene (TPE1) in water. Inside the water-soluble FONs, DPP1 worked as a two-photon absorption material and an effective Hg2+ receptor with emission peak at 540 nm. Meanwhile, TPE1, a typical aggregation-induced emission (AIE) molecule, maintained the nanostructure's stability and offered another distinguishable fluorescent signal at 470 nm as the internal reference. These hybrid FONs were successfully used in the ratiometric and two-photon fluorescence detection of Hg2+ in water. The FONs showed selective and sensitive Hg2+ detection with a limit of detection of ca. 13 nM. Tests on tap-water samples indicated good reliability of the FONs in practical application. Furthermore, the FONs were used in cell imaging, and results demonstrated their potential application in biological sensing.