Three-dimensional wormhole mesoporous-based material as a regenerative solid optical sensor for detection of Hg2+ in aqueous media

Abstract

With the aim of optical sensing of Hg²⁺ in water, a new optical sensor (RhB–HMS) for detecting Hg²⁺ has been successfully prepared by immobilizing a Rhodamine B (RhB) derivative on hexagonal mesoporous silica (HMS) via triethoxysilane groups. The transmission electron microscopy (TEM) images and X-ray powder diffraction (XRD) data of RhB–HMS confirm that the worm-like mesoporous structure is preserved during the post-grafting procedure. The nitrogen adsorption–desorption isotherms and Fourier transform infrared (FT-IR) spectroscopy results show that the grafting of the RhB derivative onto HMS is successful. A detailed study of the fluorescence properties of RhB–HMS is reported. RhB–HMS affords “turn-on” fluorescence enhancement and displays high brightness in water. In addition, RhB–HMS is able to react with Hg²⁺ between pH 5.2 and 8.3 and offer a high selectivity over several interfering cations (K⁺, Na⁺, Li⁺, Ag⁺, Cd²⁺, Ca²⁺, Co²⁺, Cu²⁺, Ni²⁺, Mg²⁺, Pb²⁺ and Fe²⁺). More importantly, RhB–HMS shows excellent reversible and regenerative ability to detect Hg²⁺ by the naked-eye.