Studying the gelation process of titanium isopropoxide by method of positron annihilation spectroscopy

Thank to its harmlessness titanium dioxide is widely utilized material. One of the new areas to use titanium dioxide is photocatalysis, which could be the way to e.g. remove organic pollutants from water or air. Titanium dioxide based gels are perspective form of TiO2 for photocatalysis because of their high porosity thus high surface area. Positron annihilation spectroscopy is a physical method to study microporous structure and electron energy distribution in materials. We studied gelation process of titanium isopropoxide in ethanol with various amount of water catalyzed by hydrochloric acid by positron annihilation lifetime spectroscopy and doppler broadening of annihilation line in this work. Positronium is weakly formed in TiO2 in general wherefore it cannot be monitored by positron annihilation spectroscopy very well. Gelation process can be monitored through pick-off annihilation of ortho-positronium. (authors)