Green Synthesis
of Anatase TiO<sub>2</sub> Nanocrystals
with Diverse Shapes and their Exposed Facets-Dependent Photoredox
Activity
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Abstract
The
exposed facets of a crystal are known to be one of the key
factors to its physical, chemical and electronic properties. Herein,
we demonstrate the role of amines on the controlled synthesis of TiO<sub>2</sub> nanocrystals (NCs) with diverse shapes and different exposed
facets. The chemical, physical and electronic properties of the as-synthesized
TiO<sub>2</sub> NCs were evaluated and their photoredox activity was
tested. It was found that the intrinsic photoredox activity of TiO<sub>2</sub> NCs can be enhanced by controlling the chemical environment
of the surface, i.e.; through morphology evolution. In particular,
the rod shape TiO<sub>2</sub> NCs with ∼25% of {101} and ∼75%
of {100}/{010} exposed facets show 3.7 and 3.1 times higher photocatalytic
activity than that of commercial Degussa P25 TiO<sub>2</sub> toward
the degradation of methyl orange and methylene blue, respectively.
The higher activity of the rod shape TiO<sub>2</sub> NCs is ascribed
to the facetsphilic nature of the photogenerated carriers within the
NCs. The photocatalytic activity of TiO<sub>2</sub> NCs are found
to be in the order of {101}+{100}/{010} (nanorods) > {101}+{001}+{100}/{010}
(nanocuboids and nanocapsules) > {101} (nanoellipsoids) > {001}
(nanosheets)
providing the direct evidence of exposed facets-depended photocatalytic
activity
