7 research outputs found
Electrochemically Induced Shape-Memory Behavior of Si Nanopillar-Patterned Electrode for Li Ion Batteries
A nanopillar-patterned Si substrate
was fabricated by photolithography,
and its potential as an anode material for Li ion secondary batteries
was investigated. The Si nanopillar electrode showed a capacity of
ā¼3000 mAh g<sup>ā1</sup> during 100 charging/discharging
cycles, with 98.3% capacity retention, and it was revealed that the
nanopillars underwent delithiation via a process similar to shape-memory
behavior. Despite the tensile stress and structural fractures resulting
from repeated lithiation, the nanoscale size and residual crystalline
tip of the pillar (influenced by the bulk crystalline Si base) enabled
recrystallization and transformation into a single-crystalline phase.
To the best of our knowledge, this observation of shape memory recrystallization
mechanism observation was not reported before for Si used as the active
material in Li ion battery applications; these findings are expected
to provide new insights into electrode materials for rechargeable
batteries
Fabrication of Superhydrophobic and Oleophobic Surfaces with Overhang Structure by Reverse Nanoimprint Lithography
This
work reports the fabrication of superhydrophobic and oleophobic surfaces
with an overhang structure by reverse nanoimprint lithography. An
overhang structure is difficult to fabricate by conventional lithography;
however, it was conveniently formed by reverse imprint lithography,
employed in conjunction with reactive ion etching. The obtained overhang
structure was coated with a fluoroalkylsilane monolayer to reduce
its surface energy. Further, four different types of nanopatterns
were separately embedded on the surface of the obtained overhang structure
by modified reverse imprint lithography to enhance its oil-repelling
properties. The embedded nanopatterns resulted in different overhang
angles, thereby enhancing the oil-repelling properties. The morphology
and wetting characteristics of the overhang structure were investigated
by scanning electron microscopy and contact angle measurements. This
study demonstrates that an overhang structure can be successfully
fabricated on a substrate by reverse nanoimprint lithography; moreover,
oleophobic structures can be realized using materials with contact
angles <90
Contribution a l'etude de la cristallisation orientee : application aux alliages Cu-Be riches en Cu
SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
MetalāOrganic Framework-Templated PdO-Co<sub>3</sub>O<sub>4</sub> Nanocubes Functionalized by SWCNTs: Improved NO<sub>2</sub> Reaction Kinetics on Flexible Heating Film
Detection
and control of air quality are major concerns in recent years for
environmental monitoring and healthcare. In this work, we developed
an integrated sensor architecture comprised of nanostructured composite
sensing layers and a flexible heating substrate for portable and real-time
detection of nitrogen dioxide (NO<sub>2</sub>). As sensing layers,
PdO-infiltrated Co<sub>3</sub>O<sub>4</sub> hollow nanocubes (PdO-Co<sub>3</sub>O<sub>4</sub> HNCs) were prepared by calcination of Pd-embedded
Co-based metalāorganic framework polyhedron particles. Single-walled
carbon nanotubes (SWCNTs) were functionalized with PdO-Co<sub>3</sub>O<sub>4</sub> HNCs to control conductivity of sensing layers. As
a flexible heating substrate, the Ni mesh electrode covered with a
40 nm thick Au layer (i.e., NiĀ(core)/AuĀ(shell) mesh) was embedded
in a colorless polyimide (cPI) film. As a result, SWCNT-functionalized
PdO-Co<sub>3</sub>O<sub>4</sub> HNCs sensor exhibited improved NO<sub>2</sub> detection property at 100 Ā°C, with high sensitivity
(<i>S</i>) of 44.11% at 20 ppm and a low detection limit
of 1 ppm. The accelerated reaction and recovery kinetics toward NO<sub>2</sub> of SWCNT-functionalized PdO-Co<sub>3</sub>O<sub>4</sub> HNCs
were achieved by generating heat on the NiĀ(core)/AuĀ(shell) mesh-embedded
cPI substrate. The SWCNT-functionalized porous metal oxide sensing
layers integrated on the mechanically stable NiĀ(core)/AuĀ(shell) mesh
heating substrate can be envisioned as an essential sensing platform
for realization of low-temperature operation wearable chemical sensor
Chemically Engineered AuāAg Plasmonic Nanostructures to Realize Large Area and Flexible Metamaterials
We
developed a simple and systematic method to fabricate optically
tunable and thermally and chemically stable AuāAg nanocrystal-based
plasmonic metamaterials. An Ag nanocrystal-based metamaterial with
desirable optical properties was fabricated via nanoimprinting and
ligand-exchange process. Its optical properties were controlled by
selectively substituting Ag atoms with Au atoms through a spontaneous
galvanic replacement reaction. The developed AuāAg-based metamaterials
provide excellent tunable plasmonic properties required for various
applications in the visible and near-infrared regions by controlling
the AuāAg composition according to the conditions of the galvanic
displacement. Furthermore, their thermal and chemical stabilities
significantly improved because of the protective Au thin layer on
the surface. Using this developed process, chemically and thermally
stable and flexible plasmonic metamaterials were successfully fabricated
on a flexible polyester terephthalate substrate
Lithography-Free, Large-Area Spatially Segmented Disordered Structure for Light Harvesting in Photovoltaic Modules
Optical losses in photovoltaic (PV)
systems cause nonradiative
recombination or incomplete absorption of incident light, hindering
the attainment of high energy conversion efficiency. The surface of
the PV cells is encapsulated to not only protect the cell but also
control the transmission properties of the incident light to promote
maximum conversion. Despite many advances in elaborately designed
photonic structures for light harvesting, the complicated process
and sophisticated patterning highly diminish the cost-effectiveness
and further limit the mass production on a large scale. Here, we propose
a robust/comprehensive strategy based on the hybrid disordered photonic
structure, implementing multifaceted light harvesting with an affordable/scalable
fabrication method. The spatially segmented structures include (i)
nanostructures in the active area for antireflection and (ii) microstructures
in the inactive edge area for redirecting the incident light into
the active area. A lithography-free hybrid disordered structure fabricated
by the thermal dewetting method is a facile approach to create a large-area
photonic structure with hyperuniformity over the entire area. Based
on the experimentally realized nano-/microstructures, we designed
a computational model and performed an analytical calculation to confirm
the light behavior and performance enhancement. Particularly, the
suggested structure is manufactured by the elastomeric stamps method,
which is affordable and profitable for mass production. The produced
hybrid structure integrated with the multijunction solar cell presented
an improved efficiency from 28.0 to 29.6% by 1.06 times
Spontaneous Registration of Sub-10 nm Features Based on Subzero Celsius Spin-Casting of Self-Assembling Building Blocks Directed by Chemically Encoded Surfaces
For low-cost and
facile fabrication of innovative nanoscale devices
with outstanding functionality and performance, it is critical to
develop more practical patterning solutions that are applicable to
a wide range of materials and feature sizes while minimizing detrimental
effects by processing conditions. In this study, we report that area-selective
sub-10 nm pattern formation can be realized by temperature-controlled
spin-casting of block copolymers (BCPs) combined with submicron-scale-patterned
chemical surfaces. Compared to conventional room-temperature spin-casting,
the low temperature (<i>e.g.</i>, ā5 Ā°C) casting
of the BCP solution on the patterned self-assembled monolayer achieved
substantially improved area selectivity and uniformity, which can
be explained by optimized solvent evaporation kinetics during the
last stage of film formation. Moreover, the application of cold spin-casting
can also provide high-yield <i>in situ</i> patterning of
light-emitting CdSe/ZnS quantum dot thin films, indicating that this
temperature-optimized spin-casting strategy would be highly effective
for tailored patterning of diverse organic and hybrid materials in
solution phase