Highly Selective Detection of Al³⁺ by Carboxamide-Based Fluorescent Chemosensor

We designed a carboxamide-based fluorescent chemosensor HTPQ ((E)-2-(((8-hydroxy-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9-yl)methylene)amino)thiophene-3-carboxamide) for detecting Al³⁺. HTPQ could probe Al³⁺ by fluorescence enhancement. Limit of detection for Al³⁺ toward HTPQ was 1.4 μM. Binding of HTPQ to Al³⁺ was determined to be a 1:1 ratio with the analysis of Job plot and ESI-mass. In addition, HTPQ was able to detect Al³⁺ using the test strip by fluorescent variation. The sensing process of Al³⁺ by HTPQ was presented by UV–vis titration, ESI–MS, Job plot, ¹H NMR titration and DFT calculation.