posted on 2024-02-16, 19:11authored byJibin Shin, Mahnmin Choi, Doeun Shim, Tyler Joe Ziehl, Seongmin Park, Eunhye Cho, Peng Zhang, Hangil Lee, Joongoo Kang, Sohee Jeong
Colloidal quantum dots (CQDs) have garnered significant
attention
in nanoscience and technology, with a particular emphasis on achieving
high monodispersity in their synthesis. Recent advances in understanding
the chemistry of reaction intermediates such as magic-sized nanoclusters
(MSC) have paved the way for innovative synthetic strategies. Notably,
monodisperse CQDs of various compositions, including indium phosphide,
indium arsenide, and cadmium chalcogenide, have been successfully
prepared using nanocluster intermediates as single-source precursors.
Still, the early stage conversion chemistry of these nanoclusters
preceding CQD formation has not been fully unveiled yet. Herein, we
report the first-order conversion of amorphous nanoclusters (AMCs)
to InAs MSCs prior to the formation of CQDs. We find that MSC, isolated
via gel-permeation chromatography, is more stable than purified AMCs,
as demonstrated in various chemical and thermolytic reactions. While
the surface of InAs AMCs and MSC is similarly bound with carboxylate
ligands, detailed structural analyses employing synchrotron X-ray
scattering and X-ray absorption spectroscopy unveil subtle distinctions
arising from the distinct surface properties and structural disorder
characteristics of InAs nanoclusters. We propose that InAs AMCs undergo
a surface reduction and structural ordering process, resulting in
the formation of an InAs MSC in a thermodynamically local minimum
state. Furthermore, we demonstrate that both types of nanoclusters
serve as viable precursors, providing a similar monomer supply rate
at elevated temperatures of around 300 °C. This study offers
invaluable insights into the interplay of structure and chemical stability
in binary nanoclusters, enhancing our ability to design these nanoclusters
as precursors for highly monodisperse CQDs.