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.