IBN
CONTACT
EDUCATION
B.Eng., Materials
Engineering, Nanyang Technological University, 2007
RESEARCH
INTEREST
My research interest is to develop a rational approach to
the design and synthesis of noble metal nanocrystals (NCs)
in desired morphology as the physicochemical properties of
NCs are strongly dependent on their shape and size. Two
types of nanostructures are of particular interest:
polyhedral NCs bound by high-index facets and hybrid metal
NCs with complex but well-defined geometries.
1)
Synthesis of noble metal NCs with high-index facets
by wet chemical methods.
High-index surface planes of noble metals denoted by a set
of Miller indices {hkl} with at least one of the indices
greater than unity are often catalytically more active than
the close packed low-index planes of the same metal. The
reason has been attributed to the presence of a high density
of atomic steps and kinks. The lure and potential of
enhanced catalytic performance has spurred the search for
shape-controlled synthesis of noble metal NCs with
high-index facets.
High quality polyhedral high-index NCs with customizable
particle attributes such as size, crystallinity and exposed
facets were synthesized by a seed-mediated growth method
combined with kinetic control.
Seed-mediated growth is a two-step synthesis in which NC
seeds are prepared first and then added to a separate
solution for growth. Such a strategy uses discrete steps to
effectively separate seed formation from growth, which is
particularly advantageous for the design of NC shapes
through the optimization of the seed structure and growth
conditions. The final shapes of the NCs are manipulated by
the growth kinetics, i.e., the relative growth rates in
different crystallographic directions, in the growth
process.
Specifically, monodisperse concave trisoctahedral gold NCs
with high-index {hhl} facets are synthesized with tunable
sizes. The crystallinity of the NCs could also be
controlled, a new nanostructure–shield-like Au NCs with
singly twinned structure and high-index {hhl} facets are
formed. Using the concave Au TOH NCs as seeds, polyhedral
Au@Pd NCs with customizable high-index Pd facets could be
obtained including concave TOH, concave hexoctahedral and
tetrahexahedral NCs with {hhl}, {hkl} and {hk0} facets
respectively. The Miller indices of NCs are also modifiable.
Gold TOH NCs with tailorable sizes.
![](Gallery/yuyue02.jpg)
Shield-like Au NCs with singly twinned structure.
![](Gallery/yuyue03.jpg)
Au@Pd polyhedral NCs with variable high-index Pd facets.
2)
Synthesis of hybrid noble metal NCs with exotic but
designable morphologies.
Hybrid NCs are elaborate multi-component NCs consisting of
two or more different materials that are integrated through
chemically bonded interfaces. Hybrid NCs represent an
effective means of integrating the properties of different
materials to provide multifunctionality in applications.
Besides, the close coupling of different components on the
nanoscale may also generate synergistically enhanced
properties.
A template growth process was used to prepare the hybrid
NCs. The core NCs were prepared first where the shapes of
the cores could be customized as a single component NC
synthesis. Then the core NCs were employed as templates for
the deposition of the secondary metals. The growth
conditions were manipulated to control the deposition site
and shape of the secondary metals. We have successfully
prepared hybrid NCs with both core and secondary metals in
well-defined shapes.
![](Gallery/yuyue04.jpg)
Core-shell Au@Pd NCs with both core and shell in
well-defined shapes |