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Issue 11, 2018
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Bipyridine bisphosphonate-based fluorescent optical sensor and optode for selective detection of Zn2+ ions and its applications

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Abstract

In this study, a bipyridine bisphosphonate-based tetrabutyl 2,2′-bisbipyridine-5,5′-diylbis(methylene) diphosphonate (L) was developed as fluorescence optical sensor for sensitive and selective determination of Zn2+. The sensing ability of L was investigated in solution as well as polymeric membrane phase using absorption and emission spectroscopy. L exhibits weak fluorescence in CH3CN/H2O (9 : 1, v/v). Upon interaction of L with Zn2+ ions, the emission intensity of L significantly increases due to chelation-enhanced fluorescence (CHEF). The Job's plot and Benesi–Hildebrand (B–H) studies revealed the formation of a L–Zn2+ complex in 1 : 1 binding stoichiometry with an estimated association constant of 4.2 × 103 M−1. The complex formation between L and Zn2+ was established from 1H NMR, 31P NMR, mass and theoretical studies. In order to make a low-cost and effective probe for sensing Zn2+ in aqueous media, the optode was prepared by incorporating L as a neutral ligand, dioctyl phthalate (DOP) as plasticizer, sodium tetraphenyl borate (NaTPhB) as an anionic additive and polyvinyl chloride (PVC) as supporting membrane. These components were systematically coated on a quartz plate of dimensions 12 mm × 16 mm with 5 mm thickness. After equilibration with Zn2+, the optode exhibited a selective and strong fluorescence at 350 nm due to CHEF. The best performance of the optode was observed with a membrane having L : PVC : DOP : NaTPhB in proportions of 2 : 62 : 35 : 1 (w/w) in 4.5–8.5 pH range. The probe can detect Zn2+ at concentrations as low as 1.3 nM with fast response time of 15 s and the optical response remains unaltered even after 3 months of use. The fluorescence reversibility of L was studied by sequential addition of Zn2+ and EDTA. The probe was used successfully used for determination of Zn2+ in pharmaceutical and water samples. In addition, L was applied for Zn2+ ions determination in HeLa cells using optical fluoroscence microscope.

Graphical abstract: Bipyridine bisphosphonate-based fluorescent optical sensor and optode for selective detection of Zn2+ ions and its applications

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Publication details

The article was received on 10 Jan 2018, accepted on 06 Apr 2018 and first published on 06 Apr 2018


Article type: Paper
DOI: 10.1039/C8NJ00158H
Citation: New J. Chem., 2018,42, 8494-8502
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    Bipyridine bisphosphonate-based fluorescent optical sensor and optode for selective detection of Zn2+ ions and its applications

    R. Selva Kumar, S. K. Ashok Kumar, K. Vijayakrishna, A. Sivaramakrishna, P. Paira, C. V. S. Brahmmananada Rao, N. Sivaraman and S. K. Sahoo, New J. Chem., 2018, 42, 8494
    DOI: 10.1039/C8NJ00158H

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