A new off-on fluorescent sensor for the detection of Al(III) based on a chromone-derived Schiff-base

[Display omitted] •We designed and synthesized a new off-on fluorescent sensor for the detection of Al3+.•The sensor showed good selectivity and high sensitivity for Al3+ in ethanol and water (3:1, v/v), and the detection limit was as low as 1.82 × 10−7 M.•The binding ratio between L and Al3+ was 2:1.•The yield of the sensor can be reached 95.4%. A new Al3+ sensor, 6-ethoxychromone-3-carbaldehyde-(3-hydroxy-2-naphthalene acyl) hydrazone (L), was designed and synthesized. The sensor L could exist steadily and detect Al3+ in the pH range from 5.0 to 8.0 in ethanol and water (3:1, v/v). This sensor showed good selectivity and high sensitivity towards Al3+ in the presence of most metal ions, and a remarkable enhancement in fluorescence emission intensity at 508 nm (λex = 420 nm) was observed with addition of 1equiv Al3+, which was attributed to the inhibition of photoinduced electron-transfer (PET) phenomenon and CN isomerization process. With the fluorescence titration experiments and the ESI-MS spectrum data, we reached the conclusion that the binding ratio between L and Al3+ was 2:1. Besides, the binding constant (Ka) between L and Al3+ was calculated to be 9.24 × 103 M−1 and the detection limit of L for Al3+ was as low as 1.82 × 10−7 M.