A Naphthol and Nitroaniline-Based Dual-target Chemosensorfor Fluorometric Sensing of Al³⁺ and Colorimetric Sensing of Fe³⁺

A naphthol and nitro-aniline-based fluorometric and colorimetric chemosensor BHMN, 1,1-bis(2-(((E)-(2-hydroxy naphthalene-1-yl)methylene)amino)ethyl)-3-(4-nitrophenyl)thiourea, was synthesized. Sensor BHMN detected Al³⁺ with fluorescence turn-on and Fe³⁺ via color variation of colorless to purple. Binding ratios of BHMN to Al³⁺ and Fe³⁺ turned out to be 1 : 1. Detection limits for Al³⁺ and Fe³⁺ by BHMN were analyzed to be 8.22 μM and 3.10 μM. Additionally, the naked-eye test strip was applied for sensing Fe³⁺ and showed that BHMN could effectively discriminate Fe³⁺ from Fe²⁺ and other cations. The binding mechanisms of BHMN to Al³⁺ and Fe³⁺ were identified by ESI-mass, Job plot, NMR titration, and DFT calculations.