A novel Fe3+ ions chemosensor by covalent coupling fluorene onto the mono, di- and tri-ammonium functionalized nanoporous silica type SBA-15

Fluorene functionalized mesoporous silica (FM-SBA-15, FD-SBA-15 and FT-SBA-15) were prepared the post synthesis grafting method of SBA-15. The grafting of fluorene in nanochannels of SBA-15 was performed in two steps: (i) attachment of the 3-aminopropyltriethoxysilane, [1-(2-aminoethyl)-3-aminopropyl]trimethoxysilane and 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane on SBA-15, then (ii) covalent linkage of fluorene. The obtained material was characterized by SAXS, N2 adsorption–desorption, FT-IR spectroscopy, Raman spectroscopy and thermogravimetric analysis that indicate the successful immobilization of fluorene on the surface of mesoporous silica. The sensing ability of FM-SBA-15, FD-SBA-15 and FT-SBA-15 was studied by addition of the cations Fe3+, Mg2+, Cr3+, Co2+, Ni2+ Cu2+, Hg2+ and Zn2+ to water suspensions of the assayed solid. Of all the cations tested addition of Fe3+ ion to a suspension of these materials resulted in the largest decrease in the fluorescence intensity but addition of Mg2+, Cr3+, Co2+, Ni2+, Cu2+, Hg2+ and Zn2+ did not quench the fluorescence of FM-SBA-15, FD-SBA-15 and FT-SBA-15. A good linearity between the fluorescence intensity of the prepared materials and the concentration of Fe3+ ion is constructed, which enables these materials as a fluorescence chemo sensor for detecting the Fe3+ ion with a suitable detection limit.