Facile synthesis of magnetic fluorescence probe for recyclable displacement detection of Hg2+ in aqueous solutions and living cells

In this work, a high-performance probe for Hg 2+ detection has been successfully synthesized based on Rhodamine B isothiocyanate (RBI) and thioglycolic acid (TA) co-modified Fe 3 O 4 @Au nanocomposites. The probe has many favorable properties, including suitable size and magnetic response (46.28 emu/g). Importantly, the fluorescence changes of the probe are remarkably specific for Hg 2+ in the presence of other competitive cations, and the limit of detection (LOD) for Hg 2+ in aqueous solutions is lower (3.03   nM) than the value of the World Health Organization (30   nM), which meet the selective and sensitive requirements for practical application. Interestingly, due to the magnetic responsive performance of Fe 3 O 4 , the probe can be recycled by a magnet and reused by addition of free RBI into Fe 3 O 4 @Au solutions that were already used for Hg 2+ detection. Furthermore, the experiments of probe for monitoring Hg 2+ inside human umbilical vein endothelial (HUVEC) cells reveal that the probe has biocompatibility and low cytotoxicity, and can effectively detect Hg 2+ in a short time. All the results presented in this study show that the proposed probe has significant potential for Hg 2+ detection in environmental and biological samples.