In situ total X-ray scattering study of the formation mechanism and structural defects in anatase TiO₂ nanoparticles under hydrothermal conditions

Abstract

Polymorphism, morphology, particle size, and defects play key roles in the physical and chemical properties of nanoparticles. In hydrothermal synthesis of metal oxide nanoparticles, it is important to understand the influence of the specific precursor on these characteristics. Here, the formation mechanism of anatase TiO 2 nanoparticles by hydrolysis of titanium isopropoxide under hydrothermal conditions is studied by in situ total X-ray scattering and pair distribution function (PDF) analysis. It is shown that the amorphous precursor structure has short-range order up to~6.5 Å consisting of titanium hydroxide clusters made from TiO 6 /TiO 5 units in an arrangement related to anatase. Insight into the structural disorder of the anatase TiO 2 nanocrystals is obtained from both PDF and powder X-ray diffraction (PXRD)analyses. Defects of OH species are present on the surface of the nanocrystals, and their concentration correlates strongly with the particle size. Even though the formation of anatase TiO 2 under hydrothermal conditions resembles a solid-state phase transition from amorphous titania, the crystallization and grain growth kinetics of the nanocrystals are different due to the effects of the solvent. CrystEngCommThis journal is † Electronic supplementary information (ESI) available: Time evolution of in situ PXRD patterns; details and examples of the refinements of the PDFs of the ordered structure, the oxygen vacancy model, and OH defect model; details of the Rietveld refinement of the PXRD data; the oxygen z coordinate and the closest Ti-O distance as functions of reaction time; determination of the crystallinity of TiO 2 nanoparticles by PXRD. See

Insight into Nucleation and Growth of Bi2–xSbxTe3 (x = 0–2) Nanoplatelets in Hydrothermal Synthesis

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Formation of a Dimeric Precursor Intermediate during the Nonaqueous Synthesis of Titanium Dioxide Nanocrystals

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The evolution of crystalline ordering for ligand-ornamented zinc oxide nanoparticles

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