Hg2+ chromogenic and fluorescence indicators based on rhodamine derivatives bearing thiophene group

Abstract

In this paper, chromogenic and fluorescent indicators have been prepared that can be used to detect Hg2+ in aqueous solutions. Through amide condensation reaction and primary amine-aldehyde reaction, sulfur containing thiophene group was connected to rhodamine B with diethylene triamine as bridge molecule, and rhodamine B-diethylene triamine sulfide was prepared and characterized. The prepared indicator can accurately detect Hg2+ in the environment without being interfered by other common metal ions such as ions of Na+, K+, Mg2+, Zn2+, Fe3+, Cu2+, Zn2+ and Cr3+. As the concentration of Hg2+ increases, the UV–vis absorbance at 560 nm grows. According to the Benesi-Hildebrand equation, combined with the UV–vis characterization, the stoichiometry between Hg2+ and the prepared indicator proved to be 1:1. The detection limit of detection of Hg2+ was equal to 1.95 × 10−7 mol/L, and the response of the solution turned to red after adding the indicator can be displayed within 2 min. This indicator applies to weakly acidic to neutral environments.