Architecture of a Hybrid Mesoporous Chemosensor for Fe³⁺ by Covalent Coupling Bis-Schiff Base PMBA onto the CPTES-Functionalized SBA-15

A novel hybrid mesoporous material PMBA-SBA was designed and synthesized by immobilizing bis-schiff base N,N‘-(1,4-phenylenedimethyli- dyne)bis(1,4-benzenediamine) (PMBA) within the channels of (γ-chloropropyl)triethoxysilicane (CPTES) modified SBA-15. TEM images of the hybrid materials illustrated the reservation of the hexagonal ordered mesoporous structure of SBA-15 after functionalization. The characteristic absorbance of the CN stretching vibration of the Schiff base was observed in the IR spectrum of the hybrid materials, indicating the successful immobilization of PMBA in the mesoporous composite, while the XPS spectra confirmed that the linkage of the PMBA molecule within the channels of CPTES-functionalized SBA-15 is realized by forming a covalent bond between amino and chloropropyl groups. This novel mesoporous material PMBA-SBA showed a high selectivity to Fe³⁺ ion, which results from a dramatic fluorescence quenching by the addition of Fe³⁺ ion upon the suspensions of PMBA-SBA. A good linearity between the fluorescence intensity of PMBA-SBA and the concentration of Fe³⁺ ion is constructed, which enables this hybrid martial as a fluorescence chemosensor for detecting the Fe³⁺ ion with a satisfactory detection limit of 1.98 × 10^-6 M. Judged on the linear equation, the fluorescence quenching of the hybrid material by Fe³⁺ ion progresses by static quenching forming a nonfluorescence complex.