A rhodamine based fluorescent and colorimetric chemosensor for the detection of Cr ions and its utility in a molecular logic gate

A new rhodamine based fluorescent and colorimetric chemosensor S1 was synthesized for the selective recognition of Cr 3+ , a trivalent metal ion. The interaction of S1 toward different metal ions has been studied via fluorescence and UV-visible spectroscopy. The studies revealed that the fluorescence and colorimetric changes of chemosensor S1 are prominent for Cr 3+ over other competitive metal ions. Moreover, the chemosensor S1 exhibits 1 : 1 complex formation with Cr 3+ as apparent from the Job's plot and the Benesi-Hildebrand (B-H) plot. Density functional theory (DFT) studies also revealed that the Cr 3+ ion is coordinated to three atoms of S1 , which validates the formation of a complex between S1 and Cr 3+ . The limit of detection (LOD) of chemosensor S1 for Cr 3+ was 0.21 μM. Furthermore, to explore the recyclability of S1 , ethylenediaminetetraacetic acid (EDTA) was added to the S1-Cr 3+ solution. On the addition of EDTA to the solution of S1-Cr 3+ , the reversibility of the complex was observed, and a colorimetric variation was also observed on the addition of Cr 3+ and EDTA to S1 which mimics the "INHIBIT "molecular logic gate. Chemosensor S1 also demonstrated practical utility through detection of Cr 3+ in the solid state. The reversible fluorescent and colorimetric changes of S1 on adding Cr 3+ and EDTA were found to mimic the 'INHIBIT' molecular logic gate.