A simple BODIPY–imidazole-based probe for the colorimetric and fluorescent sensing of Cu(II) and Hg(II)

A novel acylhydrazone derivative B3 was designed and synthesized as a multichannel chemosensor. B3 formed stable gels with several organic solvents and aqueous THF (THF:H2O = 4:1, v/v); good aggregation-induced emission (AIE) effects were observed, and each gel exhibited fluorescence. As a chemosensor, B3 detected F− selectively and sensitively via both colorimetric and fluorometric responses with detection limits of 1.4 × 10−7 and 9.5 × 10−9 M, respectively. Furthermore, B3 indicated the presence of AcO− selectively through a coloring–decoloring process within approximately 30 min, Fe3+ efficiently quenched the fluorescence of the gel fromed by B3 in aqueous THF (GB3). For example, 1 equiv of Fe3+ caused a 11-fold reduction in the fluorescence intensity (FI, quenching 91%) of GB3. Conversely, Zn2+, Mg2+, Ca2+, and Na+ effected negligible decreases in FI, while Cu2+, Al3+, Co2+, Cr3+, and Fe2+ reduced FI non-significantly. The detection limit of GB3 for Fe3+ was 1.6 × 10−6 M. Importantly, the maximum emission wavelength of GB3 and gels with the aforementioned cations were all approximately 470 nm, but the addition of Fe3+ resulted in a significant redshift (550 nm). As a result, GB3 was deemed an outstanding chemosensor for Fe3+. Finally, a test strip based on B3 and a film based on GB3 were prepared, which could be used for colorimetric detection of F− and fluorometric display of Fe3+ detection in real time.