'Naked-eye' detection of biologically important anions in aqueous media by colorimetric receptor and its real life applications

Abstract

A colorimetric receptor R 2-[(2-Hydroxy-naphthalen-1-ylmethylene)-hydrazonomethyl]-quinolin-8-ol has been designed and synthesized with good yield and characterized by the standard spectroscopic techniques such as FT-IR, UV-Visible, ¹H NMR, ¹³C NMR and ESI-MS. The receptor R showed naked-eye detection and spectral change in the presence of F^-, AcO^- and H₂PO₄^- over other anions. Interestingly, receptor R displaying high selective recognition towards F^-, AcO^- ion with a drastic color change from pale yellow to red in dry DMSO solvent and orange in mixed solvent DMSO/H₂O (9:1, v/v). The behavior of receptor R towards F^-, AcO^- ion was investigated using UV-Vis and ¹H NMR experiment. The detailed ¹H NMR experiment result revealed that the receptor R is forming the hydrogen bonding between imine nitrogen and phenolic OH proton towards anions. The receptor R is able to detect sodium salts of flouride (NaF) and acetate (NaAcO) in aqueous medium and it exhibited dramatic color change from pale yellow to red. The receptor R demonstrated itself to be useful for real life application by detecting flouride and acetate ion in sea-water and commercially available product such as toothpaste, mouthwash and vinegar solution.

Keywords: Acetate ion; Aqueous solution; Buffer study; Colorimetric sensor; Flouride ion; Real life application.