Isatin functionalized nanoporous SBA-15 as a selective fluorescent probe for the detection of Hg(II) in water

A highly ordered mesoporous silica material functionalized with isatin (SBA-Pr-IS) was designed and synthesized. Characterization techniques including XRD, TGA, BET, SEM, and FT-IR were employed to characterize the pore structure, textural properties, microscopic morphology, and molecular composition of grafted organic moieties of SBA-Pr-IS. The successful attachment of the organic moiety (0.34 mmol g^-1) without the SBA-15 structure collapsing after the modification steps was confirmed. Fluorescence characterization of SBA-Pr-IS was examined upon addition of a wide variety of cations in aqueous medium and it showed high sensitivity toward Hg²⁺ ions. During testing in an ion competition experiment, it was observed that the fluorescence changes of the probe were remarkably specific for Hg²⁺ ions. Furthermore, a good linearity between the fluorescence intensity of this material and the concentration of Hg²⁺ ions was constructed with a suitable detection limit of 3.7 × 10^-6 M. Finally, the applicability of the proposed method was successfully evaluated for the determination of Hg²⁺ ions in real samples. Therefore, SBA-Pr-IS can be used as an efficient fluorescence probe for Hg²⁺ ions. Graphical Abstract A novel organic-inorganic hybrid material was designed and synthesized by functionalization of SBA-15 mesoporous silica material with isatin. The evaluation of the sensing ability of SBA-Pr-IS using fluorescence spectroscopy revealed that the SBA-Pr-IS was a selective fluorescent probe for Hg²⁺ ion in water in the presence of a wide range of metal cations.