Turn-off Fluorescence Chemosensor for Iron with Bis(2-aminoethyl)-2-(9-fluorenyl)malonamide Functionlized SBA-15

An bis(2-aminoethyl)-2-(9-fluorenyl)malonamide as fluorophore ligand was immobilized onto mesoporous silica type SBA-15 via post synthesis grafting. The obtained material was characterized by small and wide angle X-ray diffraction, N2 adsorption-desorption, Fourier transform infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis that indicate the successful immobilization of the ligand on the surface of mesoporous silica. The sensing ability of the obtained material was studied by addition of the cations Fe(3+), Mg(2+), Cr(3+), Co(2+), Ni(2+), Cu(2+), Hg(2+) and Zn(2+) to water suspensions of the assayed solid. Of all the cations tested addition of Fe(3+) ion to a suspension of this material resulted in the largest decrease in the fluorescence intensity. Turn-off photoluminescence of this material was remarkably observed for iron ions in comparing of the other cations. A good linearity between the fluorescence intensity of this material and the concentration of Fe(3+) ion is constructed, which enables it as a fluorescence chemosensor for detecting the Fe(3+) ion with a suitable detection limit of 1.35 × 10(-5). It can be introduced as a novel fluorescent sensor in aqueous solution for a lot of practical applications in chemical, environmental and biological systems.