Novel Crystal Growth from a Two-Dimensionally Bound Nanoscopic System. Formation of Oriented Anatase Nanocrystals from Titania Nanosheets

A monolayer film of unilamellar titania crystallites consisting of two planes of Ti/O atoms and two additional planes of O atoms underwent an interesting structural change by heat treatment at 800 °C and above to produce anatase nanocrystals oriented along the c-axis. This phenomenon is distinct from phase transformation of the bulk phase in terms of the significantly higher crystallization temperature of anatase and the preferential orientation of nanocrystals. This may be peculiar to two-dimensional nanosystems, providing a new route for the fabrication of oriented nanocrystals.