Amorphous-anatase phase transition in single immobilized TiO2 nanoparticles

Kinetics of the amorphous-anatase phase transition in single immobilized 5-nm TiO2 nanoparticles has been studied at temperatures between 400 and 1000 °C at the DORIS-III synchrotron source of Hasylab. The measurements indicate the anatase phase appearance at temperatures above 500 °C. No formation of rutile phase was observed. The transformation kinetics for each fixed temperature is rapid and completes within 5 min. The crystalline mass progressively increases with temperature and the full transformation into anatase polymorph is achieved above 800 °C. The results suggest higher surface energy of the anatase phase compared to amorphous one, which delays the crystallization process.