Design, Synthesis And Application Of A Novel Formaldehyde Fluorescent Probe With Dual Quenching Mechanism Based On Aggregation-induced Luminescence Molecules

Energy transfer between fluorescent dyes and quenchers is critical in the design of light-up probes.In principle,fluorescent probes with two quenchers will have lower background signal and higher turn-on ratios than those with only one quencher.But in literature,it is rare to report dual-quenched fluorescent probes.Because in a dual-quenched fluorescent probe,both quenching groups need to be located near the fluorophore,which needs tedious synthetic work and possesses low detection efficiency.These drawbacks thereby limit the development of the double quenched fluorescent probe.In this thesis,we utilized intramolecular motion(IM)and photoinduced electron transfer(PET)as dual-quenching mechanisms to build dual-quenched light-up probes based on fluorogens with aggregation-induced emission(AIEgen).The water-soluble group can increase the water solubility of the probe and promote the intramolecular movement of AIEgen to quench the fluorescence.As this quenching group depends little on the distance,it is at the far-end of the fluorophore.The quencher with photoinduced electron transfer needs to be close to the fluorophore,so it is at the near-end of the fluorophore.To demonstrate the feasibility of this strategy,we developed probes for the detection of formaldehyde(FA)using this dual-quenched mechanism.The probe has a negligible background,which is capable of detecting not only free formaldehyde molecules but also paraformaldehyde,and has high sensitivity and the turn-on ratios higher than 4,900.Importantly,the probe also produces good results in human serum.This study thereby indicates that the dual-quenched design based on AIEgens could be applied to develop light-up probes for other functional molecules.