Specific colorimetric detection of Fe 3+ ions in aqueous solution by squaraine-based chemosensor.

A new squaraine based chemosensor TSQ was developed for colorimetric detection of Fe 3+ ions. A thymine moiety in TSQ was constructed to act as an ion acceptor. The sensor displayed an instant colorimetric response specific to Fe 3+ over the other metal ions in 20% AcOH-H 2 O solution. The limit of detection was much lower than that of the environmental protection agency guideline (5.37 μM) in drinking water. A 1 : 1 binding between TSQ and Fe 3+ ion was evidenced by Job's plot measurement, ESI-MS and Fourier transform infrared (IR) measurements. Moreover, the proposed sensing mechanism of the receptor towards Fe 3+ was strongly supported by DFT calculation. Finally, the sensor has proven to be suitable in real sample applications.