A phenoxazine-based
fluorescence chemosensor 4PB [(4-(tert-butyl)-N-(4-((4-((5-oxo-5H-benzo[a]phenoxazin-6-yl)amino)phenyl)sulfonyl)phenyl)benzamide)]
was designed and synthesized by a simple synthetic methods. The 4PB fluorescence chemosensor selectively detects Ba2+ in the existence of other alkaline metal ions. In addition, 4PB showed high selectivity and sensitivity for Ba2+ detection. The detection limit of 4PB was 0.282 μM
and the binding constant was 1.0 × 106 M–1 in CH3CN/H2O (97.5:2.5 v/v, HEPES = 1.25 mM,
pH 7.3) medium. This chemosensor functioned through the intramolecular
charge transfer (ICT) mechanism, which was further confirmed by DFT
studies. Live cell imaging in MCF-7 cells confirmed the cell permeability
of 4PB and its capability for specific detection of Ba2+ in living cells.