Highly selective, reversible and ICT-based fluorescent chemosensor for bismuth ions: Applications in bacterial imaging, logic gate and food sample analysis

Abstract

N1,N5-bis(pyridin-2-ylmethylene)naphthalene-1,5-diamine (L1) Schiff base conjugate was synthesized by the condensation reaction of 1,5-diamino naphthalene (1,5-DAN) and 2-pyridine carboxaldehyde and spectroscopically evidenced by 1H NMR, 13C NMR and Mass spectrum. The developed Schiff base conjugate was used as a fluorescent chemosensor for the selective recognition of bismuth (Bi3+) ions in the midst of various interfering heavy transition metal ions such as Ag+, Hg2+ and Cu2+ with marked fluorescence enhancement. Based on “switch-on” intramolecular charge transfer (ICT) approach, chemosensor L1 showed specific response towards bismuth ions with a low detection limit of 1.5 × 10−8 M and a high binding constant 7.11 × 105 M−1. Simultaneously, the experimental (Job’s plot, Mass spectrum, and FT-IR) and theoretical (B3LYP-D3/6–311++G(d,p)) analysis were performed for promising the 1:1 binding mode of L1 + Bi3+ complex formation. The chemosensor L1 has been successfully demonstrated in practical applications such as water and food samples, bacterial imaging and logic gate operation producing satisfactory results.