In recent years, the widely explored phenomenon “aggregation-induced
emission (AIE)” has played a crucial role in the development
of luminescent materials for light-emitting applications. In the same
direction, the contribution of its sister concept “AIE switching”
has been impressive. In comparison, the application of this concept
in the field of biosensing or bioimaging is still in its infancy.
Therefore, to shed light into the sensing of bioanalytes, we have
developed a new perylenediimide (PDI)-based small fluorescent probe,
benzoannulated PDI (Bp(Im)2MA), that selectively detects
diamines and biogenic amines (BAs) in solution via an “AIE-switching”
phenomenon. The synthesized probe containing the bay-annulated anhydride moiety exhibits strong cyan emission in solution.
In the mechanism, we have shown that the terminal free amine group
of BAs readily reacts with a highly reactive anhydride moiety, which
opens the cyclic anhydride moiety. In the open conformation, the free
amine group along with a carboxylate group modulates the polarity
of the system strikingly. Because of this induced polarity, the monomer
of Bp(Im)2MA-BAs conjugate aggregated in solution, thereby
exhibiting a significant change in emission property in solution.
This method may also be called a very simple and straightforward “naked
eye” detection of BAs in solution, with a nanomolar detection
limit. A detailed spectroscopic and microscopic investigation demonstrated
the existence of the aggregated state. As the reporter dye also emits
strongly in the solid state (yellowish orange), it therefore instantly
made vapor-phase detection of BAs feasible. Finally, this vapor-phase
detection of BAs by the probe was applied very effectively in the
determination of spoilage of raw fish.
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