The
precise regulation of the electron-withdrawing/electron-donating
strength in a probe is of great significance for the design of reaction-based
fluorescent probes with specific functionalities. Here, a family of
excited-state intramolecular proton transfer (ESIPT)-based probes
with fluorescence turn-on sensing properties toward KMnO4 was designed by precisely modulating the electron-withdrawing strength
of the substituents located at the para-position
of the recognition group. It is found that −F, −CHO,
and −H as the electron-withdrawing groups bound at the probe
can specifically recognize KMnO4, which ensures a blue
emission displayed by the reaction products. Especially with −CHO
as the electron-withdrawing group, the reaction product shows the
most stable fluorescence. The probe 2-(benzo[d]oxazol-2-yl)-4-formylphenyl
acrylate (BOPA-CHO) demonstrated a more superior sensing performance
toward KMnO4, including a low limit of detection (LOD,
0.96 nM), a rapid response (<3 s), and a rather good selectivity
even in the presence of 21 interferents. Moreover, the practicality
of the probe was further verified by a test pen comprising a BOPA-CHO-embedded
sponge, which is capable of detecting KMnO4 solid with
a naked-eye LOD of 11.62 ng. The present probe design and modulation
strategy would open up a new path for the design of high-performance
fluorescent probes.
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