Two novel Al 3+ fluorescent-on probes based on thiazole substituted salicylaldehyde and its applications

In this study, two structurally similar 'turn on' fluorescent probes B1 and B2 with high binding energy with Al3+ were synthesised. With new thiazole substituted salicylaldehyde fluorophore, these two hosts also have good selectivity and sensitivity in the detection of Al3+ based on the chelating fluorescence-enhancing effect under test conditions. They show an extremely low detection limit, 0.478 nM and 4.04 nM, respectively, with binding constants of 2.34 × 106 M−1 and 1.36 × 106 M−1. A 1:1 binding ratio of dual probes to Al3+ was demonstrated by working curves and mass spectrometry. The mechanisms were confirmed by 1H NMR and DFT calculations, defined that both two compounds combined with Al3+ by two oxygen atoms (one in C=O and another in -OH) and one nitrogen atom in -NH group to form triple coordination structure. Further application in test strips, actual soil and traditional Chinese medicine (TCM) suggest probes B1 and B2 have well application prospects in detecting Al3+.