The poly(ethylene glycol) assisted preparation of NH4TiOF3 mesocrystals and their topotactic conversion to TiO2

Abstract

Poly(ethylene glycols) with different molecular weights were used to prepare NH₄TiOF₃ mesocrystals. The use of PEG-1000, -10 000, or -20 000 produced NH₄TiOF₃ mesocrystals whereas, PEG-4500 produced TiO₂ (anatase) in nanoparticulate form. The shapes and the crystal structures of NH₄TiOF₃ mesocrystals formed with PEGs are similar to those obtained with the Brij family of nonionic surfactants. The conversion of NH₄TiOF₃ mesocrystals prepared with PEG-20 000 to TiO₂ (anatase) mesocrystals by heat treatment or washing with boric acid was also studied. The TiO₂ mesocrystals retained the crystallographical orientation of the parent NH₄TiOF₃ mesocrystals and the apparent average sizes of the nanoparticles are between several and tens of nanometers.