Selective fluorescence sensing of Hg2+ and Zn2+ ions through dual independent channels based on the site-specific functionalization of mesoporous silica nanoparticles

Abstract

A novel method for the selective fluorescence sensing of Hg²⁺ and Zn²⁺ ions via dual independent channels was reported, based on the site-specific functionalization of mesoporous silica nanoparticles (MSN). Taking advantage of the distinctive co-condensation and post-grafting process of different organoalkoxysilanes, amine and azide functionalities were covalently attached to the inner and outer surfaces of MSN, respectively. The site-specific incorporation of rhodamine B-based Hg²⁺ (RhBHA) and quinoline-based Zn²⁺ (CQA) ion sensors was then achieved via the combination of nucleophilic substitution reactions, click chemistry, and living radical polymerization. Spatial separation produced by the silica framework can effectively eliminate the possibility of fluorescence resonance energy transfer (FRET) processes between the two fluorescence sensors, providing dual independent channels for the selective detection of Hg²⁺ and Zn²⁺ ions simultaneously. This work represents the first report of the concurrent detection of dual heavy metals through the regional modification of hybrid MSN. Most importantly, freedom to combine diverse fluorescence sensors with distinct fluorophores can also be achieved following similar procedures, offering promising potential for the detection of multiple heavy metal ions.