Anatase Coarsening Kinetics under Hydrothermal Conditions As a Function of Ph and Temperature

Nanoparticles coarsen in solution via atom-by-atom dissolution and reattachment (Ostwald ripening) or via crystallographically controlled attachment of discrete particles (oriented attachment). We coarsened anatase nanoparticles in hydrothermal solutions over the temperature range 105−250 °C and the pH range 1−12 and documented three distinct coarsening mechanisms controlled by solution pH. Anatase growth at pH > 11 occurs primarily by Ostwald ripening, yielding a wide particle size distribution. Over the pH range of 2 through 11, anatase grows both by oriented attachment and Ostwald ripening. At pH values