Fluorene-Functionalized, Dendrimer-Modified SBA-15: Detection of Iron(III) and Mercury (II) in Aqueous Media and Logic Gate Studies

A novel silica-based fluorescent sensor, (S-DPP), was prepared via grafting of dimethyl 3,3 '-(propylazanediyl)(1Z,1 ' Z)-bis(N-(9H-fluoren-2-yl)propanimidate) (DPP), onto the pore walls of SBA-15 channels. DPP was prepared by growing of dendrimer (G= 0.5) onto the amino functionalized surface of SBA-15, followed by anchoring of 2-aminflourene via imine condensation. Synthesized materials were characterized using FT-IR, PXRD, SEM, TEM, BET and TGA techniques. Fluorescence properties of the sensor were investigated in aqueous solution towards various metal ions. The signal quenching of sensor at lambda=380 nm is based on complex formation between the S-DPP and Fe3+ or Hg2+ ions, leading to the inhibition of reverse intramolecular charge transitions at the probe and appearance of new transitions at Mn+-S-DPP complex. Furthermore, the limit of detection of both ions were calculated as 2.4 x 10(-8) M and 6.3 x 10(-8) M, respectively. A reversibility in fluorescence behavior of the probe was found in the presence of Cl-, and was demonstrated a circuit logic system with the Fe3+, Hg2+ and Cl- ions. Finally, density functional theory (DFT) and time-dependent density functional theory (TDDFT) computational studies were performed in order to obtain a detailed electronic description of the quenching mechanism by Hg2+ and Fe3+ as well as studying the structure and bonding in the complexes.