A Colorimetric and Fluorescent Indicator for Hg 2+ Detection Based on Cinnamamide Group-Containing Rhodamine Derivative.

A colorimetric and fluorescent indicator based on cinnamamide group-containing rhodamine derivative was synthesized for the detection of Hg2+ . The rhodamine B and cinnamamide were connected via ethylenediamine as a bridging molecule through a condensation reaction to obtain a colorimetric and fluorescent indicator for the detection of Hg2+ in H2 O-EtOH (4:1, v/v). The indicator was excellent in the selectivity of Hg2+ and was almost unaffected by other common ions such as Na+ , K+ , Mg2+ , Fe3+ , Cu2+ , Zn2+ , Cr3+ . The Hg2+ -containing aqueous solution turned from colorless to red within 7 min after the addition of the indicator, and had an absorption peak at 564 nm in UV-vis, which implies a significant colorimetric phenomenon. Their characteristic peaks varied with the Hg2+ content, and they reached a linear relationship at low concentrations. The binding stoichiometry proved to be 1:1. The lowest detection limit was 4.1 × 10-7  mol/L, ranging from acidic to neutral.