The Preparation Of The Magnetic TiO₂Mesocrystals

Mesocrystals are a kind of special nano-structured materials, which are built ofcrystallographically oriented nanoparticles.TiO2mesocrystals are reported to possess highphotocatalytic activity due to their high degree of crystallinity and large porosity. And tosolve the problem on the callback of TiO2after the light-catalyzed reaction, a route hadbeen designed to endow the TiO2mesocrystals with magnetic property, because of whichmesocrystals can be easily separated from the reaction by external magnetic field. Themain work is summarized as follows:Firstly, the co-precipitation and solve-thermal methods were adopted to prepareFe₃O₄nanoparticles with small and large size, and to increase the stability, these two kindof magnetic particles were coated with a thin SiO2layer via the hydrolysis of TEOS.Secondly, the prepared Fe₃O₄@SiO2was introduced into the synthetic process of theNH4TiOF3mesocrystals as seeds. Thirdly, the obtained Fe₃O₄@SiO2@NH4TiOF3mesocrystals were converted to Fe₃O₄@SiO2@TiO2through the hydrolysis in HBO3solution or the sintering process. Lastly the photocatalytic activity of Fe₃O₄@SiO2@TiO2was evaluated by degrading the methylene blue solution. XRD, DLS and TEM resultsshowed that the uniform magnetic nanoarticles with narrow size distribution had beensuccessfully prepared and magnetic mesocrystals were obtained with a “round inside withsquare outside” structure, while the Fe₃O₄coated with SiO2served as the core andNH4TiOF3mesocrystals as the shell. The magnetic TiO2had good magnetic property andexcellent photocatalytic activity.