Chemistry Reference
In-Depth Information
Generally, dimensionally controlled nanostructures have
attracted significant interest for a wide range of materials, some of
which also demonstrated fascinating properties. For example, Ag and
Au nanocrystals of different shapes possess unique optical scattering
responses [45-47]. Although highly symmetric spherical particles
exhibit a single scattering peak, anisotropic shapes — such as rods
[47], triangular prism [45], and cubes [46] — of these materials
exhibit multiple scattering peaks in the visible wavelengths due
to highly localized charge polarizations at corners and edges. This
suggests that control of nanocrystals shape could offer a strategy for
optical tuning. Yet, chemical reactivity is highly dependent on surface
morphology, the bonding facets of the nanocrystal, the number of the
step edges and kink sites, as well as the surface-to-volume ratio. By
exploiting these properties, El-Sayed
. [48] showed that shape-
controlled Pt and Pd nanocrystals can be used to achieve highly
selective catalysis. In another study, Huynh
et al
. [49] showed that
by integrating 1D semiconducting CdSe nanorods with P3HT hole
transporting polymers, photovoltaic devices (i.e., solar cells) can
be fabricated. In another work, the same group demonstrated the
development of a new type of single-electron transistor (SET) using
CdSe tetrapods [50]. Therefore, shape-controlled nanomaterials do
not have merely aesthetic appeal but offer huge promise in catalysis,
electronic, as well as biomedical industries. In the following
sections, however, we will limit our discussion to representative
dimensionally controlled rare earth nanostructures, their synthesis,
and mechanism of formations.
et al
2.3.1
Zero-Dimensional (0D) Rare Earth Nanostructures
Among the 0D nanocrystals, spheres are the most basic and
symmetric motif. Cubes, truncated cubes, truncated octahedral, and
octahedral structures are other typical shapes. There have been a
great number of reports on various 0D rare earth nanoparticles.
However, only a few representative works will be highlighted in this
section.
Rare earth fluorides (REF
), an extensively studied class of rare
earth materials, will be used to illustrate different forms of 0D
nanostructures. Li
4
et al
. reported a series of REF
nanostructures
4
