Synthesis of Dispersed Anatase Microspheres with Hierarchical Structures via Homogeneous Precipitation

Abstract

Abstract Spherical anatase microparticles with good crystallinity have been synthesized by homogeneous precipitation under mild conditions (83–100 °C), employing ammonium fluotitanate as the titanium source and urea as the precipitant instead of more commonly used and highly reactive titanium sources such as titanium alkoxides and tetrachloride, which are sensitive to atmospheric moisture and therefore require special precautions. The as‐prepared anatase particles were characterized by XRD, FE‐SEM, UV/Vis spectroscopy, TG‐DSC, and FTIR spectroscopy. The microspheres obtained in this work are hierarchically structured and are built up of rounded anatase nanocrystallites with a diameter of approximately 15–40 nm. The morphology of the nanoparticles within each microparticle changes from sphere to spindle as the reaction time is increased from 30 to 120 min in the experimental temperature range from 83 to 100 °C. A higher reaction temperature leads to enhanced growth of the nanocrystallites (primary particles) in solution and somewhat smaller anatase microspheres. The optical bandgaps and indirect bandgaps for all samples are approximately 3.23 and 2.95 eV, respectively, irrespective of their morphologies.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)