Preparation and characterization of an optical sensor based on magnetic core and fluorescence “Off-On” probe for Hg(II) sensing and removal

• A Hg(II) sensing and removal optical sensor was constructed.
• Superparamagnetic Fe3O4 nanodots were used as the excitation core.
• Silica molecular sieve MCM-41 was used as the shell.
• A rhodamine derivative probe was grafted into MCM-41 tunnels.
• Linear response, high selectivity and good recycling performance were observed.

We reported a core–shell structured nanocomposite for Hg(II) sensing and removal, using superparamagnetic Fe3O4 nanodots as the core and silica molecular sieve MCM-41 as the shell. A rhodamine derived emission “Off-On” probe was grafted into the tunnels of MCM-41. The resulting nanocomposite was fully characterized and studied with electron microscopy images, XRD curves, thermogravimetric analysis and N2 adsorption/desorption isotherms, confirming the core–shell structure and the successful probe loading. The Hg(II) sensing and removal performance of this nanocomposite was then explored in detail. Experimental data suggested that the emission from the probe increased with the increasing Hg(II) concentration, showing emission “Off-On” effect and linear response towards Hg(II) ion. Fast response, good selectivity and low detection limit were also obtained, owing to the highly ordered tunnels from MCM-41. In addition, good recycling performance was achieved by this nanocomposite.

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