Organically Functionalized Mesoporous SBA-15 Type Material Bearing Fluorescent Sites for Selective Detection of Hg^II...

Hg(II) contamination in water resources is one of the major health issues in keeping the purity standard of the municipal water supply. Herein, we report a new mesoporous sensor probe material SBA-ABZ-PEA having a 2D-hexagonally ordered mesoporous framework bearing covalently bonded fluorescent sites, and this has been synthesized through a two-step post-synthesis grafting route. A pure silica mesoporous SBA-15 material has been functionalized with (3-chloropropyl)triethoxysilane (ClPTES) to obtain chloro-functionalized SBA-15, which was further reacted with 4-aminobenzaldehyde followed by treatment with 2-(2-pyridyl)-ethylamine resulting in functionalized 2D-hexagonal mesoporous sensor probe SBA-ABZ-PEA. Small angle PXRD, N₂ adsorption/desorption, HRTEM, TGA, and FT-IR studies have been carried out to characterize these materials. Our experimental results suggested successful grafting of the organic moiety on the SBA-15 surface along with preservation of mesoporosity throughout the grafting process. Photoluminescence measurements were carried out in the aqueous suspension of SBA-ABZ-PEA in the presence of different metal cations, like Na^I, Mg^II, Al^III, K^I, Ca^II, Mn^II, Co^II, Cu^II, Zn^II, Cd^II, Pb^II, and Hg^II. This result revealed that, among the various metal-ions, the emission intensity of the mesoporous sensing probe material SBA-ABZ-PEA has been dramatically quenched in the presence of the Hg^II ion. To check the sensitivity of the sensor probe, the fluorescence emission was also studied in the presence of different concentrations of Hg^II ions. A perfect linear plot between the concentrations of Hg^II ions in the aqueous medium with their corresponding fluorescence intensities with a detection limit of 1.2 × 10^-6 M has been observed.