Controlling
Surface Defects and Photophysics in TiO<sub>2</sub> Nanoparticles
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Abstract
Titanium dioxide (TiO<sub>2</sub>) is widely used for photocatalysis
and solar cell applications, and the electronic structure of bulk
TiO<sub>2</sub> is well understood. However, the surface structure
of nanoparticulate TiO<sub>2</sub>, which has a key role in properties
such as solubility and catalytic activity, still remains controversial.
Detailed understanding of surface defect structures may help explain
reactivity and overall materials performance in a wide range of applications.
In this work we address the solubility problem and surface defects
control on TiO<sub>2</sub> nanoparticles. We report the synthesis
and characterization of ∼4 nm TiO<sub>2</sub> anatase spherical
nanoparticles that are soluble and stable in a wide range of organic
solvents and water. By controlling the temperature during the synthesis,
we are able to tailor the density of defect states on the surface
of the TiO<sub>2</sub> nanoparticles without affecting parameters
such as size, shape, core crystallinity, and solubility. The morphology
of both kinds of nanoparticles was determined by TEM. EPR experiments
were used to characterize the surface defects, and transient absorption
measurements demonstrate the influence of the TiO<sub>2</sub> defect
states on photoinduced electron transfer dynamics
