ABSTRACT
A new rhodamine based fluorescent and colorimetric chemosensor S1 was synthesized for the selective recognition of Cr3+, 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 Cr3+ over other competitive metal ions. Moreover, the chemosensor S1 exhibits 1 : 1 complex formation with Cr3+ as apparent from the Job's plot and the Benesi-Hildebrand (B-H) plot. Density functional theory (DFT) studies also revealed that the Cr3+ ion is coordinated to three atoms of S1, which validates the formation of a complex between S1 and Cr3+. The limit of detection (LOD) of chemosensor S1 for Cr3+ was 0.21 µM. Furthermore, to explore the recyclability of S1, ethylenediaminetetraacetic acid (EDTA) was added to the S1-Cr3+ solution. On the addition of EDTA to the solution of S1-Cr3+, the reversibility of the complex was observed, and a colorimetric variation was also observed on the addition of Cr3+ and EDTA to S1 which mimics the "INHIBIT "molecular logic gate. Chemosensor S1 also demonstrated practical utility through detection of Cr3+ in the solid state.
ABSTRACT
A pyridine dicarboxylate Schiff-base DAS was synthesized for cascade colorimetric recognition of Ni2+ and PPi. The selectivity and sensitivity of chemosensor DAS was investigated through colorimetric and UV-vis studies in MeOH-PBS (5 : 1, v/v, pH = 7.4). The chemosensor formed a 2 : 1 complex with Ni2+ metal ions with a binding constant of Ka = 3.07 × 103 M-2. Besides, a plausible sensing mechanism is confirmed by single crystal X-ray diffraction (SC-XRD), Job's plot and Benesi-Hildebrand plot (B-H plot) experiments. Furthermore, the DAS-Ni2+ ensemble formed 'in situ' was used to selectively recognise PPi. The limit of detection (LOD) of DAS for Ni2+ was found to be 0.14 µM and that of the DAS-Ni2+ ensemble for PPi was found to be 0.33 µM. Also, the potential of the chemosensor has been applied for solid state detection of Ni2+ as well as to mimic the 'INHIBIT' logic gate on the addition of Ni2+ ions and PPi.
ABSTRACT
A novel pyranopyrazole-based Schiff base PPS has been synthesized via a condensation reaction between aldehyde and hydrazide derivatives of pyranopyrazole. The probe acted as a selective and sensitive chemosensor for the colorimetric detection of arginine under aqueous conditions with a detection limit of 1.8 × 10-5 M. The 1 : 1 binding stoichiometry was established using various UV-vis spectroscopic methods. A plausible binding mechanism of PPS towards arginine was established via 1H NMR titration techniques and the results were further validated using DFT studies. Moreover, PPS provided a reasonable response for arginine in dietary supplements and human blood plasma which demonstrates its potential application in real sample analysis as well.
