Pseudocapacitance
holds great promise for energy density improvement
of supercapacitors, but electrode materials show practical capacity
far below theoretical values due to limited ion diffusion accessibility
and/or low electron transferability. Herein, inducing two kinds of
straight ion-movement channels and fast charge storage/delivery for
enhanced reaction kinetics is proposed. Very thick electrodes consisting
of vertically aligned and ordered arrays of NiCo2S4-nanoflake-covered slender nickel columns (NCs) are achieved via a scalable route. The vertical standing ∼5 nm
ultrathin NiCo2S4 flakes build a porous covering
with straight ion channels without the “dead volume”,
leading to thickness-independent capacity. Benefiting from the architecture
acting as a “superhighway” for ultrafast ion/electron
transport and providing a large surface area, high electrical conductivity,
and abundant availability of electrochemical active sites, the NiCo2S4@NC-array electrode achieves a specific capacity
up to 486.9 mAh g–1. The electrode even can work
with a high specific capacity of 150 mAh g–1 at
a very high current density of 100 A g–1. In particular,
due to the advanced structure features, the electrode exhibits excellent
flexibility with a unexpected improvement of capacity when being largely
bent and excellent cycling stability with an obvious resistance decrease
after the cycles. An asymmetric pseudocapacitor applying the NiCo2S4@NC-array as a positive electrode achieves an
energy density of 66.5 Wh kg–1 at a power density
of 400 W kg–1, superior to the most reported values
for asymmetric devices with NiCo2S4 electrodes.
This work provides a scalable approach with mold-replication-like
simplicity toward achieving thickness-independent electrodes with
ultrafast ion/electron transport for energy storage.
Nowadays, numerous
electrochemical and photoelectrochemical (PEC)
methods have been utilized for water-splitting hydrogen production.
Herein, we designed a novel photocathode based on a TiO2/Au nanoring (AuNR)/Si nanohole (SiNH) hetero-nanostructure (HN),
which can be fabricated in a programmable way. The SiNH arrays substrate
was prepared by nanoimprint lithography, and then, embedded AuNRs
were fabricated by sputtering deposition and subsequent ion beam etching
to remove the Au layer covering the horizontal Si surface. Cylindrical
AuNRs clinging to the sidewalls of SiNH arrays could maximize the
horizontal exposure area of the Si substrate and have little adverse
effect on its light absorption. The design is supported by theory
simulation and could lead to expectable PEC performance by precisely
controlling the geometry and size of the AuNR which will trigger localized
surface plasmon resonance (LSPR), bringing about a prominent enhancement
of the light harvesting ability and exciting vast hot electrons under
light illumination. Generated electrons could transfer across the
Schottky junction formed by AuNR and TiO2 to contribute
to the hydrogen evolution reaction (HER). The excellent hydrogen production
performance with an onset potential of 0.32 VRHE of our
prepared HN electrode could be attributed to the synergetic effect
of an electrochemical and PEC process, and the maximum photon-to-energy
conversion efficiency reaches 13.3%. The experimental results are
in good accordance with the simulation analysis and demonstrate an
enhancement of the catalytic performance by optimizing the sizes of
those components. This work may provide a new path to boost hydrogen
production performance by designing customized HNs with a positive
effect for electrocatalysis or photoelectrocatalysis.
Nanoimprint lithography presents a new strategy for preparing uniform nanostructures with predefined sizes and shapes and has the potential for developing nanosized drug delivery systems. However, the current nanoimprint lithography is a type of an additive nanofabrication method that has limited potential due to its restricted template-dependent innate character. Herein, we have developed a novel subtractive UV-nanoimprint lithography (sUNL) for the scalable fabrication of PLGA nanostructures with variable sizes for the first time. sUNL can not only fabricate a variety of predefined nanostructures by simply utilizing different nanoimprint molds but also precisely prepare scalable nanocylinders with different length to diameter ratios. Particularly, sUNL can fabricate paclitaxel-loaded PLGA nanocylinders (PTX-PLGA NCs) with high drug-loading rate of 40% and long storage stability over a year. We demonstrate that PTX-PLGA NCs target clathrin-and caveolae-mediated cell transport pathways and display increased cellular uptake, in comparison to traditional PTX-loaded PLGA nanoparticles (PTX-PLGA NPs), leading to enhanced anticancer effects. Therefore, sUNL represents a promising nanofabrication method for efficiently developing predefined drug delivery systems.
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