2 research outputs found
Three-Dimensional Reduced-Symmetry of Colloidal Plasmonic Nanoparticles
Owing to their novel optical properties, three-dimensional
plasmonic
nanostructures with reduced symmetry such as a nanocrescent and a
nanocup have attracted considerable current interest in biophotonic
imaging and sensing. However, their practical applications have been
still limited since the colloidal synthesis of such structures that
allows, in principle, for in vivo application and large-scale production
has not been explored yet. To date, these structures have been fabricated
only on two-dimensional substrates using micro/nanofabrication techniques.
Here we demonstrate an innovative way of breaking symmetry of colloidal
plasmonic nanoparticles. Our strategy exploits the direct overgrowth
of Au on a hybrid colloidal dimer consisting of Au and polystyrene
(PS) nanoparticles without the self-nucleation of Au in an aqueous
solution. Upon the overgrowth reaction, the steric crowding of PS
leads to morphological evolution of the Au part in the dimer ranging
from half-shell, nanocrescent to nanoshell associated with the appearance
of the second plasmon absorption band in near IR. Surface-enhanced
Raman scattering signal is obtained directly from the symmetry-broken
nanoparticles solution as an example showing the viability of the
present approach. We believe our concept represents an important step
toward a wide range of biophotonic applications for optical nanoplasmonics
such as targeting, sensing/imaging, gene delivery, and optical gene
regulations
Synthetic Control of Intrinsic Defect Formation in Metal Oxide Nanocrystals Using Dissociated Spectator Metal Salts
Crystallographic
defects are essential to the functional properties
of semiconductors, controlling everything from conductivity to optical
properties and catalytic activity. In nanocrystals, too, defect engineering
with extrinsic dopants has been fruitful. Although intrinsic defects
like vacancies can be equally useful, synthetic strategies for controlling
their generation are comparatively underdeveloped. Here, we show that
intrinsic defect concentration can be tuned during the synthesis of
colloidal metal oxide nanocrystals by the addition of metal salts.
Although not incorporated in the nanocrystals, the metal salts dissociate
at high temperatures, promoting the dissociation of carboxylate ligands
from metal precursors, leading to the introduction of oxygen vacancies.
For example, the concentration of oxygen vacancies can be controlled
up to 9% in indium oxide nanocrystals. This method is broadly applicable
as we demonstrate by generating intrinsic defects in metal oxide nanocrystals
of various morphologies and compositions