Quantized
Reaction Pathways for Solution Synthesis
of Colloidal ZnSe Nanostructures: A Connection between Clusters, Nanowires,
and Two-Dimensional Nanoplatelets
posted on 2020-03-23, 16:34authored byPatrick
D. Cunningham, Igor Coropceanu, Kavan Mulloy, Wooje Cho, Dmitri V. Talapin
The
morphology of nanocrystals serves as a powerful handle to modulate
their functional properties. For semiconducting nanostructures, the
shape is no less important than the size and composition, in terms
of determining the electronic structure. For example, in the case
of nanoplatelets (NPLs), their two-dimensional (2D) electronic structure
and atomic precision along the axis of quantum confinement makes them
well-suited as pure color emitters and optical gain media. In this
study, we describe synthetic efforts to develop ZnSe NPLs emitting
in the ultraviolet part of the spectrum. We focus on two populations
of NPLs, the first having a sharp absorption onset at 345 nm and a
previously unreported species with an absorption onset at 380 nm.
Interestingly, we observe that the nanoplatelets are one step in a
quantized reaction pathway that starts with (zero-dimensional (0D))
magic-sized clusters, then proceeds through the formation of (one-dimensional
(1D)) nanowires toward the (2D) “345 nm” species of
NPLs, which finally interconvert into the “380 nm” NPL
species. We seek to rationalize this evolution of the morphology,
in terms of a general free-energy landscape, which, under reaction
control, allows for the isolation of well-defined structures, while
thermodynamic control leads to the formation of three-dimensional
(3D) nanocrystals.