Safranin O-functionalized cuboid mesoporous silica material for fluorescent sensing and adsorption of permanganate

Incorporation of dual functions, i.e., sensing and adsorption, into one single organic-inorganic hybrid material for the detection and removal of toxic permanganate (MnO₄^-) ions is of great importance, representing a challenging and new task in the design and application of new functional materials. However, most of the reported materials display only one function as either sensing probes or adsorbents. In this work, a fluorescent cuboid mesoporous silica-based hybrid material (SiO₂@SFNO) is first prepared by the covalent coupling of a new safranin O-based fluorophore (2,8-dimethyl-5-phenyl-3,7-bis(3-(3-(triethoxysilyl)propyl)ureido)phenazin-5-ium chloride) (SFNO) and newly-made cuboid mesoporous silica, which showed selective dual-functional activities towards MnO₄^- and green emission at 575 nm with a long-range excitation wavelength that is suitable for bio-imaging application. The design of this SiO₂@SFNO material is based on the position of -NHCONH- groups, which are mainly responsible for the strong and selective coordination with MnO₄^-. SiO₂@SFNO is responsive to MnO₄^- at parts per billion (67 ppb) level; it also displays high adsorption ability (292 mg g^-1) to MnO₄^- in aqueous solutions. The fluorescence responses of MnO₄^-in vivo (limnodrilus claparedianus and zebrafish) demonstrate the possibility of further application in biology. Interestingly, this SiO₂@SFNO material is also capable of monitoring trace amounts of Hg²⁺ and Cu²⁺ in living organisms, holding great potential in bio-related applications.