Journal article

Nonhydrolytic Synthesis of High-Quality Anisotropically Shaped Brookite TiO2 Nanocrystals

A surfactant-assisted nonaq. strategy, relying on high-temp. aminolysis of titanium carboxylate complexes, has been developed to access anisotropically shaped TiO2 nanocrystals selectively trapped in the metastable brookite phase. Judicious temporal manipulation of precursor supply to the reaction mixt. enables systematic tuning of the nanostructure geometric features over an exceptionally wide dimensional range (30-200 nm). Such degree of control is rationalized within the frame of a self-regulated phase-changing seed-catalyzed mechanism, in which homogeneous nucleation, on one side, and heterogeneous nucleation/growth processes, on the other side, are properly balanced while switching from the anatase to the brookite structures, resp., in a continuous unidirectional crystal development regime. The time variation of the chem. potential for the monomer species in the soln., the size dependence of thermodn. structural stability of the involved titania polymorphs, and the reduced activation barrier for brookite nucleation onto initially formed anatase seeds play decisive roles in the crystal-phase- and shape-tailored growth of titania nanostructures by the present approach.


Related material