A bifunctional optical probe based on ESIPT-triggered disalicylaldehyde with ratiometric detection of iron and copper ions

In this paper, we design and synthesize an N -linked disalicylaldehyde H 2 Q j1 based on the economical substrates, and it is composed of two identical salicylaldehyde moieties with the intramolecular ESIPT character. During the process of sensing heavy metal ions, it is found that the ESIPT state of H 2 Q j1 can be rapidly (60 s) destroyed by Fe(III) and Cu(II), resulting in the turn-off fluormetric and colorimetric responses. Serial fluorescence and absorption titration experiments reveal that the H 2 Q j1 -Fe(III) and H 2 Q j1 -Cu(II) sensing systems are ratiometric and their corresponding coordination modes are 1:1 and 2:1. Especially, their LOD values are as low as 0.40 μΜ and 0.21 μΜ which are comparable to reported examples. Moreover, we also develop a convenient technique to detect Fe(III) and Cu(II) using paper-based sensing devices together with smartphone-based RGB analysis method which will rapidly provide the precise determination results, even in the tap water sample. Therefore, this bifunctional disalicylaldehyde H 2 Q j1 is taken as a useable platform to monitor Fe(III) and Cu(II) and offers some valuable lights for further optical probes.