Imaging of Al3+ in plant roots by the interaction with a bisphenol A-based chemosensor

Abstract

Al³⁺ ions are considered to be the most toxic form of aluminum for plant roots. To identify this metal ion in roots, a molecule, 4,4′-(propane-2,2-diyl)bis(2-((E)-(2-hydroxyphenylimino)methyl)phenol) (H₄L), has been synthesized from the condensation reaction between 5,5′-(propane-2,2-diyl)bis(2-hydroxybenzaldehyde) and 2-aminophenol. H₄L shows a 470-fold increase in its fluorescence intensity at 519 nm in the presence of two eq. of Al³⁺ ions in 10 mM HEPES buffer in H₂O/DMF = 4 : 1 (v/v) (pH 7.4). It forms a 1 : 2 complex with Al³⁺ with an association constant value of 6.95 × 10⁸ M⁻². Its quantum yield increased from 0.003 to 0.530 on complexation. The LOD value of the probe was determined to be 4.6 × 10⁻⁷ M, indicating its high sensitivity towards Al³⁺. This probe has been used for the imaging of aluminum ions in rice (Oryza sativa).