Phenazine functionalized pillar[5]arene: Synthesis, host-guest property and application in the fluorescence sensing of biogenic amine in solution, gel and air

The development of selective sensing materials for biogenic amine detection has attracted tremendous interest because amines have high toxicity and exist widely. In this paper, phenazine-bridged pillar[5]arene monomers PA and a naphthalene diimide containing neutral guest-bearing alkyl chain binding sites NDI were designed and synthesized. They could self-assemble by host–guest interactions to form a microsphere structure in dilute solution. A series of biogenic amines can selectively quench the microsphere fluorescence. The microsphere structure transformed into the supramolecular polymer gel at relatively high concentrations. More interestingly, the supramolecular polymerization process induced fluorescence emission enhancement based on an AIE mechanism in the gel state. The supramolecular polymer gel material exhibited sensitive stimulus–response behavior owing to stimuli-induced reversible electron transfer in the presence of various amines. The gel soft material collapse could be achieved by fuming under a series of amines vapors. Besides, our results demonstrate an effective material design strategy that may be extended to fluorescence sensing of biogenic amine in solution, gel, and air and applications to detect food spoilage. It is envisaged that this important method would pave the way for overcoming the sensor's application constraints in the solution state.