Sol-gel derived silica thin films immobilized with 1,10-phenanthroline and their binding activity toward iron(II)

Transparent sol-gel thin films immobilized with 1,10-phenanthroline were prepared via the acid-catalyzed sol-gel reaction of tetraethylorthosilicate (TEOS) in the presence of phen. Three surfactants that include cationic cetyl trimethyl ammonium bromide (CTAB), anionic sodium dodecyl sulfate (SDS) and non-ionic Triton X-100 (TX-100) were tested for the improvement of the host material mesostructure, increasing its porosity and good accommodation of the phen within the silica matrix. The immobilized phen thin films showed similar behavior as their free counterpart in aqueous solution. The immobilized phen complex retained its activity toward Fe2+ metal ions by immobilization and produced a stable complex without any shift in the wavelength of Vis absorption spectra comparing with its free counterpart. Different parameters including concentrations of phen, Fe2+ and surfactant, type of surfactant, lifetime and number of measurements were investigated. The phen thin film sensor showed high sensitivity, chemical stability, good reproducibility and long lifetime behavior. The immobilized phen thin films were used for quantification of iron(II) in versatile aqueous samples. The polarized light microscopy indicated that the phen molecules were distributed uniformly within the host silica network.