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Manipulating the Formation of NH4TiOF3 Mesocrystals: Effects of Temperature, Surfactant, and pH
journal contribution
posted on 2016-02-21, 13:03 authored by Yanqiong Liu, Yu Zhang, Hui Li, John WangThere are two main competitive processes involved in
the formation of NH4TiOF3 mesocrystals. One
leads to the assembly of individual NH4TiOF3 nanocrystals and the subsequent formation of NH4TiOF3 mesocrystals. The other converts the NH4TiOF3 nanocrystals into TiO2 (anatase) nanoparticles
and results in the subsequent formation of TiO2 aggregates.
Surfactant (Brij 58) molecules appear to facilitate the mesoscale
assembly of NH4TiOF3 nanocrystals into NH4TiOF3 mesocrystals via the interaction of their
hydrophobic tails. Elevated temperature and higher solution pH (adjusted
by ammonia solution) increase the conversion rate of NH4TiOF3 nanocrystals into TiO2 (anatase) nanoparticles.
This conversion process reduces the amount of NH4TiOF3 nanocrystals available for the mesoscale assembly and consequently
increases the pore volume of the resultant NH4TiOF3 mesocrystals. Fluorination and {001} facets affect the photocatalytic
performance of the calcined products (anatase TiO2) of
the NH4TiOF3 mesocrystals. The present study
demonstrates the key parameters that control the formation and stability
of NH4TiOF3 mesocrystals and the photocatalytic
behavior of nanocrystalline TiO2 derived from the mesocrystals.