Unveiling Chemical Reactivity and Structural Transformation
of Two‑Dimensional Layered Nanocrystals
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Abstract
Two-dimensional
(2D) layered nanostructures are emerging fast due
to their exceptional materials properties. While the importance of
physical approaches (e.g., guest intercalation and exfoliation) of
2D layered nanomaterials has been recognized, an understanding of
basic chemical reactions of these materials, especially in nanoscale
regime, is obscure. Here, we show how chemical stimuli can influence
the fate of reaction pathways of 2D layered nanocrystals. Depending
on the chemical characteristics (Lewis acid (<sup>1</sup>O<sub>2</sub>) or base (H<sub>2</sub>O)) of external stimuli, TiS<sub>2</sub> nanocrystal
is respectively transformed to either a TiO<sub>2</sub> nanodisc through
a “compositional metathesis” or a TiO<sub>2</sub> toroid
through multistage “edge-selective structural transformation”
processes. These chemical reactions can serve as the new design concept
for functional 2D layered nanostructures. For example, TiS<sub>2(disc)</sub>-TiO<sub>2(shell)</sub> nanocrystal constitutes a high performance
type II heterojunction which not only a wide range solar energy coverage
(∼80%) with near-infrared absorption edge, but also possesses
enhanced electron transfer property
