An off-on-off fluorescence probe based on a pyrazole derivative for Al3+ and Fe3+ detection

Abstract

A new fluorescence probe (E)-N′-(2,3-dihydroxybenzylidene)-1-(pyridin-2-yl)-5-(thiophen-2-yl)-1H-pyrazol-3-carbohydrazide (L) was designed and synthesized, which could be applied as an off-on-off sensor for the successive detection of Al³⁺ and Fe³⁺. The detection limits of L towards Al³⁺ and Fe³⁺ were determined to be 1.10 × 10⁻⁸ M and 4.45 × 10⁻⁸ M, respectively. The 1 : 2 binding stoichiometry of L to Al³⁺ and Fe³⁺ was established from Job plot analysis, ¹H NMR spectroscopy and mass spectrometry titration. Application experiments proved that L had excellent ability to monitor Al³⁺ and Fe³⁺ in tap water, and the sensing process could be performed on test paper as well.