A Schiff-base receptor based chromone derivate: Highly selective fluorescent and colorimetric probe for Al(III)

Upon excitation of the visible light, probes show colorimetric and fluorescent responses to the specific metal ion, which can be easily detected by the naked eye. Owing to the excitation of the visible light at 423 nm, a novel and simple Schiff-base receptor based chromone derivative called 7-methoxychromone-3-carbaldehyde-(indole-3-formyl) hydrazone (MCIH2) had been investigated as a selective and sensitive probe for Al³⁺ with colorimetric and fluorescent responses. Upon addition of Al³⁺ to compound MCIH2 solution, compound MCIH2 could respond to Al³⁺ with a good selective colorimetric signal, which was easily observed from colorless to yellow-green by the naked eye. Furthermore, a remarkable fluorescence emission enhancement with an "OFF-ON" signal by over 700-fold was triggered, but other various metal ions had no such significant effects on the fluorescence emission. In addition, the detection limit of compound MCIH2 for recognizing Al³⁺ was evaluated to be as low as 1 × 10^-7 M level, which was sufficiently low for sensing Al³⁺ widely distributed in various environmental and biological systems.