A Facile Synthesis of Uniform NH_4TiOF_3 Mesocrystals and Their Conversion to TiO_2 Mesocrystals

摘要

Uniform mesocrystals of TiO_2 (anatase) have been prepared from mesocrystals of NH_4TiOF_3. NH_4TiOF_3 was synthesized from an aqueous solution containing (NH_4)_2TiF_6 and H_3BO_3 in the presence of a nonionic surfactant Brij 56, Brij 58, or Brij 700, at low temperatures. The exterior shapes of NH_4TiOF_3 mesocrystals can be tuned by adjusting the reagent concentration, reaction time, reaction temperature, and rate of stirring. The formation of the NH_4TiOF_3 mesocrystals proceeds via a self-assembly process involving nonclassical crystal growth. By sintering in air at 450 ℃, or washing with H_3BO_3 solution at ambient temperatures, the NH_4TiOF_3 mesocrystals can be converted to mesocrystals of TiO_2 (anatase), and the original architecture is retained.