The Influence of Different Types of SiO₂ Precursors and Ag Addition on the Structure of Selected Titania-Silica Gels

Abstract

In this paper, samples of titania-silica system were obtained by the sol-gel method as bulk materials, using titanium propoxide Ti(C3H7O)4 to introduce titania and two precursors of SiO2: TEOS tetraethoxysilane Si(OC2H5)4 and DDS dimethyldiethoxysilane (CH3)2(C2H5O)2Si. To enhance antibacterial properties, Ag was added to gels of selected compositions. The main aim of the performed studies was to find the correlations between the structural changes and the applied precursor of silica. Simultaneously, the influence of different compositions of gels and the addition of Ag on the specimens’ structure was investigated. To study the structure, two complementary methods, FTIR (Fourier Transform InfraRed) spectroscopy and X-ray diffraction, were applied. The analysis of the FTIR spectra and the XRD patterns made it possible to confirm the amorphous state of all dried gels and establish the presence of TiO2 polymorphs: anatase and rutile in all annealed samples. The addition of Ag atoms into the gels caused the crystallization of cristobalite phase in addition to titania polymorphs. The presence of crystalline Ag phase in the annealed gels allowed the calculation dimensions of Ag crystallites based on the Scherrer equation. The use of DDS as a silica precursor led to easier and faster crystallization of different TiO2 phases in the annealed samples and parallel increases in the depolymerization of silica lattice.

Keywords

• TiO₂-SiO₂ system
• sol-gel method
• silica precursors
• FTIR spectroscopy
• X-ray diffraction