A simple rhodanine-based fluorescent sensor for mercury and copper: The recognition of Hg2+ in aqueous solution, and Hg2+/Cu2+ in organic solvent

Abstract

Detection of copper and mercury attracts important in most environmental and biological systems. In this study, the simple probe 2-OxI-Rh containing rhodanine core was synthesized by a green approach and sensing properties were studied using colorimetric and fluorometric detection. The research indicated that the specific ion affinity for Hg2+ ions in aqua systems and the multi-ion affinity for Hg2+ and Cu2+ in organic solvent results in drastic color and spectral changes. According to the data obtained, while the peak intensity increases at 390 nm, the peak intensity decreased at 272 nm in the absorption spectrum of 2-OxI-Rh and an increase in fluorescence intensity of 2-OxI-Rh were observed in the presence of Hg2+ and Cu2+ ions. The binding ratio of 2-OxI-Rh to Hg2+ and Cu2+ were found to be 1:1 according to Job's plot experiments. The binding constants were calculated using the Benesi-Hildebrand equation and found to be 2.15 × 104 M−1 for Hg2+ and 1.21 × 104 M−1 for Cu2+. Based on these concentration dependent fluorescence changes, the limit of detection (LOD) values were also calculated and found to be 3.36 μM for Hg2+ and 2.31 μM for Cu2+, which is the range of copper that should be in the blood (11.8–23.6 μM). As a result of all these studies, we can understand that prove 2-OxI-Rh, which is non-toxic, is a good selective candidate turn-on sensor that can be used for Hg2+ and Cu2+ detection in different solvent systems.