Novel fluorescent Schiff bases as Al3+ sensors with high selectivity and sensitivity, and their bioimaging applications

Abstract

Abstract A short set of three new Schiff base chemosensors with high selectivity and sensitivity towards Al3+ over other metal cations in aqueous solution were developed and fully characterized. Compounds (E)-1-(( l -glutamine-imino)methyl)naphthalen-2-ol (A), (E)-1-((glucosamine-imino)methyl)naphthalen-2-ol (B), and (E)-3-hydroxy-4-(((2-hydroxynaphthalen-1-yl)methylene)amino)benzoic acid (C) exhibited a significant fluorescence enhancement in the presence of Al3+ over other competitive metal ions with a low detection limit of 0.103, 0.317 and 0.091\u202fμM respectively, much lower than the WHO acceptable limit (0.05\u202fmg/L or 1.85\u202fμM of Al3+) in drinking water. The Schiff base C, shows high sensitivity in aqueous media (Limit of detection, LOD: 0.091\u202fμM) and with a 38-fold (ϕ\u202f=\u202f1.64% for Schiff free base; ϕ\u202f=\u202f63.91% for Aluminium complex) fluorescence enhancement in the presence of Al3+. The theoretical research has enabled us to rationalize the behaviours of the three selective-sensors to Al3+ synthesized in this work. Based on the design, the amino acid Schiff bases (A) showed good solubility and compatibility with and without Al3+ and some fluorescent bioimaging (FBI) are reported in human epithelial cells Hs27.