Tetraphenylethene–2-Pyrone Conjugate: Aggregation-Induced Emission Study and Explosives Sensor

Design
and synthesis of a novel tetraphenylethene–2-pyrone (TPEP) conjugate exhibiting donor–acceptor characteristics
is reported. The localized frontier molecular orbitals (DFT studies)
and the solvent polarity dependent photoluminescence characteristics
directly corroborate the presence of intramolecular charge transfer
character in TPEP. TPEP is poorly emissive
in the solution state. In contrast, upon aggregation (THF/water mixtures), TPEP exhibits aggregation-induced emission enhancement. Upon
aggregation, dyad TPEP forms a fluorescent nanoaggregate
which was confirmed by transmission electron microscopy imaging studies.
The luminescence nanoaggregates were elegantly exploited for selective
detection of nitro aromatic compounds (NACs). It was found that nanoaggregates
of TPEP were selectively sensing the picric acid over
the other NACs. Efficiency of the quenching process was further evaluated
by the Stern–Volmer equation. TPEP-based low-cost
fluorescent test strips were developed for the selective detection
of picric acid.