A novel rhodamine-based Hg2+ sensor with a simple structure and fine performance

Abstract

An excellent spectral sensor for Hg²⁺ named 2-(2-((2-aminoethyl)thio)ethyl)-3′,6′-bis(diethylamino)spiro[isoindoline-1,9′-xanthen]-3-one (RMTE) was achieved by a one-step reaction between rhodamine B and thiobisethylamine. RMTE could detect Hg²⁺ in nearly pure water reversibly and highly selectively, indicated by a new increasing absorption peak at 561 nm and 170-fold enhanced fluorescence at 578 nm coupled with remarkable visual and fluorescence color changes. When the Hg²⁺ concentration ([Hg²⁺]) varied from 0 to 120 μM, the absorbance and fluorescence intensity of the RMTE solution responded linearly to [Hg²⁺] with the detection limits of 2.08 and 0.14 μM, respectively. RMTE could work in ecologically and biologically favorable pH values of 6.41–8.33. The binding mode of RMTE toward Hg²⁺ was 1 : 1. RMTE could monitor Hg²⁺ in environmental water and living cells effectively with low cytotoxicity.