A reversible Schiff base chemosensor for the spectroscopic and colorimetric sensing of Eu3+ ions in solution and solid-state

Abstract

Herein, the metal sensing properties of a previously reported aluminium sensor (E)-N’-((2-hydroxynapthalene-1-yl)thiophene-2-Carbohydrazide) (L) have been further explored in selective sensing of lanthanide ions. Among many tested lanthanide ions sensor L showed the selective colorimetric response for only Eu3+ ions. The presence of Eu3+ ions caused electronic transitions in the visible region with a color change from colorless to yellow in aqueous acetonitrile media. A red-shift in the absorption band and enhancement in emission intensity is investigated only for the addition of Eu3+ ions to L, without any interference of other existing ions. This chemosensor binds the Eu3+ ions in 1:1 stoichiometric ratio and works upto a detection limits, 2.179 × 10-8 M (LOD for Eu3+ at 415 nm from UV–Visible), 3.443 × 10-8 M (LOD for Eu3+ at 477 nm from fluorescence) with a binding constant of 8.691 × 103 M−1 for the L-Eu3+ binding. However, the developed sensor is used as a paper, cotton-based test kit assay and solid state colorimetric sensing of Eu3+ ions. The reversibility of sensor L is checked by colorimetric observation with the addition of sodium salt ethylenediaminetetraacetic acid (EDTA) and found it reversible up to three cycles.