Synthesis of thiophene derived fluorescent sensor for Hg2+ ion detection and its applications in cell imaging, latent fingerprint, and real water analysis
P. Sunitha, Bhavana G. Gowda, Pallavi Singh, G. Vengatesh, Kavitharaj Varadaraju, Kasim Sakran Abass, Victor Stupin, Ekaterina Silina, Shiva Prasad Kollur
Abstract
A new, simple, and robust thiol-based Schiff base ligand, ( E )-3-(((2-mercaptophenyl) imino) methyl) pyridin-2-ol (PMP) as a chemical sensor for Hg 2+ ion detection was synthesized through the condensation reaction between 2-hydroxynicotinaldehyde and 2-aminobenzenethiol. The structure of PMP was elucidated by using 1 H NMR, LC-MS, and UV-Visible and spectrofluorometric techniques. PMP exhibits chelation-enhanced fluorescence quenching upon exposure to Hg 2+ , as coordination with the sulfur and nitrogen atoms, which results in the formation of a simple “turn-off” sensor in DMSO: H 2 O (v/v: 6/4) (HEPES 0.01 M, pH = 7.4) at room temperature. Job’s plot confirmed that the binding ratio of PMP and Hg 2+ ions was in 1:1 ratio. The detection limit of PMP for Hg 2+ ions was found to be 5.2 × 10 − 8 M. Furthermore, PMP was effectively employed in a smartphone application-based RGB analysis for the detection of Hg 2+ and the limit of detection in this case was found to be 0.2 × 10 − 6 M. In addition, this study also reports potential application of PMP as a sensor for Hg 2+ ions in human HeLa cells and for the quantitative detection of Hg 2+ in real water samples. The cell imaging studies using PMP against HeLa cells revealed that it has a high permeability into cell membranes, making it a practical and biocompatible probe, which can be used to detect Hg 2+ ions in the live cells. The latent fingerprint visualizations using PMP was performed to evaluate its efficiency in forensic application. Furthermore, we used density functional theory (DFT) calculations to do an extensive computational modelling investigation of PMP and its Hg(II) complex.