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ABSTRACT
A colorimetric anion sensor (E)-3-((2-((4-(4-Methoxyphenyl)thiophen-2- yl)methyl)hydrazono)methyl)-1 H-indole ATH was synthesised and confirmed by different spectroscopic methods, such as 1 H NMR, 13 C NMR, ESI-Mass and FT-IR spectroscopy. The ATH sensor revealed the spectral change and detection in the presence of fluoride ion over the other anions such as OH−, Cl−, AcO−, I−, HSO4−, NO3−, Br−, S2-, CN− & NO2−. Interestingly, sensor ATH exhibited highly selective fluoride ion detection with significant changes in the colour from light yellow to dark yellow in ACN and ACN: H2O (8:2, v/v) medium. The colorimetric sensor effectively responds to fluoride ion stimulation through deprotonation and (ICT) intramolecular charge transfer sensing mechanism. The fluoride sensing mechanism was confirmed by 1 H NMR titration and was supported by density functional theory (DFT) and electrochemical studies. In this study, the B–H plot calculates the stoichiometry and binding constant (Ka) of the host-guest complex and strong interaction between the probe ATH with fluoride ions forming a 1:2 binding ratio. Furthermore, the test strips based on the probe ATH were used to detect F- ions qualitatively and quantitatively in 100% aqueous solution.
Acknowledgments
This work was financially supported by the Mangalore University research fellowship. Authors gratefully acknowledge BSR one-time grant to Prof. B. Narayana for the purchase of chemicals. Authors thank DST-purse lab for ESI-Mass analysis and IISc for NMR analysis.
Disclosure statement
We do not have a direct financial relation with the commercial identities mentioned in the report submitted that might lead to an interest for any of us.
Supplementary material
Supplemental data for this article can be accessed here.