7 research outputs found
Self-Assembled Three-Dimensional Nanocrown Array
Although an ordered nanoplasmonic probe array will have a huge impact on light harvesting, selective frequency response (<i>i.e.</i>, nanoantenna), and quantitative molecular/cellular imaging, the realization of such an array is still limited by conventional techniques due to the serial processing or resolution limit by light diffraction. Here, we demonstrate a thermodynamically driven, self-assembled three-dimensional nanocrown array that consists of a core and six satellite gold nanoparticles (GNPs). Our ordered nanoprobe array is fabricated over a large area by thermal dewetting of thin gold film on hexagonally ordered porous anodic alumina (PAA). During thermal dewetting, the structural order of the PAA template dictates the periodic arrangement of gold nanoparticles, rendering the array of gold nanocrown. Because of its tunable size (<i>i.e.</i>, 50 nm core and 20 nm satellite GNPs), arrangement, and periodicity, the nanocrown array shows multiple optical resonance frequencies at visible wavelengths as well as angle-dependent optical properties
Omnidirectionally Stretchable and Transparent Graphene Electrodes
Stretchable and transparent electrodes
have been developed for
applications in flexible and wearable electronics. For customer-oriented
practical applications, the electrical and optical properties of stretchable
electrodes should be independent of the directions of the applied
stress, and such electrodes are called omnidirectionally stretchable
electrodes. Herein, we report a simple and cost-effective approach
for the fabrication of omnidirectionally stretchable and transparent
graphene electrodes with mechanical durability and performance reliability.
The use of a Fresnel lens-patterned electrode allows multilayered
graphene sheets to achieve a concentric circular wavy structure, which
is capable of sustaining tensile strains in all directions. The as-prepared
electrodes exhibit high optical transparency, low sheet resistance,
and reliable electrical performances under various deformation (<i>e</i>.<i>g</i>., bending, stretching, folding, and
buckling) conditions. Furthermore, computer simulations have also
been carried out to investigate the response of a Fresnel lens-patterned
structure on the application of mechanical stresses. This study can
be significant in a large variety of potential applications, ranging
from stretchable devices to electronic components in various wearable
integrated systems
Plasmonic Optical Interference
Understanding
optical interference is of great importance in fundamental
and analytical optical design for next-generation personal, industrial,
and military applications. So far, various researches have been performed
for optical interference phenomena, but there have been no reports
on plasmonic optical interference. Here, we report that optical interference
could be effectively coupled with surface plasmons, resulting in enhanced
optical absorption. We prepared a three-dimensional (3D) plasmonic
nanostructure that consists of a plasmonic layer at the top, a nanoporous
dielectric layer at the center, and a mirror layer at the bottom.
The plasmonic layer mediates strong plasmonic absorption when the
constructive interference pattern is matched with the plasmonic component.
By tailoring the thickness of the dielectric layer, the strong plasmonic
absorption can facilely be controlled and covers the full visible
range. The plasmonic interference in the 3D nanostructure thus creates
brilliant structural colors. We develop a design equation to determine
the thickness of the dielectric layer in a 3D plasmonic nanostructure
that could create the maximum absorption at a given wavelength. It
is further demonstrated that the 3D plasmonic nanostructure can be
realized on a flexible substrate. Our 3D plasmonic nanostructures
will have a huge impact on the fields of optoelectronic systems, biochemical
optical sensors, and spectral imaging
Asymmetrically Coupled Plasmonic Core and Nanotriplet Satellites
Here,
we report asymmetrical multiple electromagnetic coupling
of plasmonic core and nanotriplet satellites. Within the plasmonic
core and nanotriplet satellites, an enhanced local field is generated
which expands across the core due to multiple electromagnetic coupling
between a core and nanotriplets. Based on 3D simulations of our plasmonic
nanosystem, the overall local field enhancement reaches to over 10<sup>4</sup> times, compared with that of a single nanoparticle array.
A strong local field distribution across the core to nanotriplets
as well as the critical role of the plasmonic core is demonstrated
through the 3D simulations. It is proposed that a self-assembled nanotriplet
array is completed through two stages of dewetting of a gold thin
film on an anodic aluminum oxide (AAO) template. Formation of the
core–nanotriplet satellites is significantly influenced by
geometrical parameters (i.e., the pore diameter and depth) of the
AAO template. Our experimental results show that the local field of
our plasmonic nanostructures is amplified up to ∼110 times
by adopting a core into the nanotriplet satellites, compared with
that of the nanotriplets array without a core. This approach offers
a promising strategy for creating an advanced nanoplasmonic platform
with strong local field distribution and high-throughput production
Plasmonic–Photonic Interference Coupling in Submicrometer Amorphous TiO<sub>2</sub>–Ag Nanoarchitectures
In this study, we report the crystallinity
effects of submicrometer
titanium dioxide (TiO<sub>2</sub>) nanotube (TNT) incorporated with
silver (Ag) nanoparticles (NPs) on surface-enhanced Raman scattering
(SERS) sensitivity. Furthermore, we demonstrate the SERS behaviors
dependent on the plasmonic–photonic interference coupling (P-PIC)
in the TNT-AgNP nanoarchitectures. Amorphous TNTs (A-TNTs) are synthesized
through a two-step anodization on titanium (Ti) substrate, and crystalline
TNTs (C-TNTs) are then prepared by using thermal annealing process
at 500 °C in air. After thermally evaporating 20 nm thick Ag
on TNTs, we investigate SERS signals according to the crystallinity
and P-PIC on our TNT-AgNP nanostructures. (A-TNTs)-AgNP substrates
show dramatically enhanced SERS performance as compared to (C-TNTs)-AgNP
substrates. We attribute the high enhancement on (A-TNTs)-AgNP substrates
with electron confinement at the interface between A-TNTs and AgNPs
as due to the high interfacial barrier resistance caused by band edge
positions. Moreover, the TNT length variation in (A-TNTs)-AgNP nanostructures
results in different constructive or destructive interference patterns,
which in turn affects the P-PIC. Finally, we could understand the
significant dependency of SERS intensity on P-PIC in (A-TNTs)-AgNP
nanostructures. Our results thus might provide a suitable design for
a myriad of applications of enhanced EM on plasmonic-integrated devices
P-Type Polymer-Hybridized High-Performance Piezoelectric Nanogenerators
Enhancing the output power of a nanogenerator is essential
in applications
as a sustainable power source for wireless sensors and microelectronics.
We report here a novel approach that greatly enhances piezoelectric
power generation by introducing a p-type polymer layer on a piezoelectric
semiconducting thin film. Holes at the film surface greatly reduce
the piezoelectric potential screening effect caused by free electrons
in a piezoelectric semiconducting material. Furthermore, additional
carriers from a conducting polymer and a shift in the Fermi level
help in increasing the power output. PolyÂ(3-hexylthiophene) (P3HT)
was used as a p-type polymer on piezoelectric semiconducting zinc
oxide (ZnO) thin film, and phenyl-C<sub>61</sub>-butyric acid methyl
ester (PCBM) was added to P3HT to improve carrier transport. The ZnO/P3HT:PCBM-assembled
piezoelectric power generator demonstrated 18-fold enhancement in
the output voltage and tripled the current, relative to a power generator
with ZnO only at a strain of 0.068%. The overall output power density
exceeded 0.88 W/cm<sup>3</sup>, and the average power conversion efficiency
was up to 18%. This high power generation enabled red, green, and
blue light-emitting diodes to turn on after only tens of times bending
the generator. This approach
offers a breakthrough in realizing a high-performance flexible piezoelectric
energy harvester for self-powered electronics
Halide Perovskite Nanopillar Photodetector
Numerous studies have reported the
use of halide perovskites as highly functional light-harvesting materials.
The development of optimized compositions and deposition approaches
has led to impressive improvements; however, no noticeable breakthrough
in performance has been observed for these materials recently. Here,
a breakthrough that enables the fabrication of vertically grown halide
perovskite (VGHP) nanopillar photodetectors <i>via</i> a
nanoimprinting crystallization technique is demonstrated. We used
engraved nanopatterned polymer stamps to form VGHP nanopillars during
the pressurized crystallization of the softly baked gel state of a
methylammonium lead iodide (CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>, denoted MAPI) film. The VGHP films exhibit much lower defect density
and higher conductivity, as supported by current–voltage characteristic
measurements and conductive atomic force microscopy measurements.
Ultimately, two-terminal lateral photodetectors based on the VGHP
nanopillar films show a greatly enhanced photoresponse compared with
flat film-based photodetectors. We expect that the deposition method
presented here will help surpass the technical limits and contribute
to further improvements in various halide-perovskite-based devices