Search for content and authors

Facile synthesis of uniform NH4TiOF3 mesocrystals and their conversion to TiO2 mesocrystals by topotactic transformation

Lei Zhou ,  David S. Boyle ,  Paul O'Brien 

Department of Chemistry and the Manchester Materials Science Centre, Manchester M139PL, United Kingdom


Mesocrystals are an interesting class of nanomaterials, similar to colloidal crystal assemblies but differing by processing superstructures of vectorially (rather than randomly aligned) non-spherical nanocrystals. The nearly perfectly-ordered nanocrystalline subunits results in single-crystal-like electron diffraction patterns. Mesocrystals and their syntheses also provide a challenge to accepted views on crystal growth as is typically described by a process of nucleation and growth; and/or Ostwald ripening. Uniform mesocrystals of anatase TiO2 have been prepared by a topotactic transformation from NH4TiOF3. Mesocrystals of NH4TiOF3 were synthesised from an aqueous solution containing (NH4)2TiF6 and H3BO3 in presence of Brij series surfactants at room temperature. The exterior shapes of NH4TiOF3 mesocrystals can be tuned by adjusting the reaction parameters including: reagent concentration, reaction time, reaction temperature and rate of stirring. The formation of the mesocrystals of NH4TiOF3 proceeds via self-assembly process involving non-classical kinetically driven processes and amorphous intermediates. By sintering in air at 450 oC or washing with H3BO3 solution at ambient temperatures, the NH4TiOF3 mesocrystals can be converted to anatase TiO2 mesocrystals by self-templated topotaxial conversion, thus retaining their original architecture.

SEM (a & b) and TEM (c) images of NH4TiOF3 mesocrystals


Legal notice
  • Legal notice:

Related papers

Presentation: Invited at E-MRS Fall Meeting 2007, Symposium B, by Paul O'Brien
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-22 11:29
Revised:   2009-06-07 00:44