11 research outputs found
Breath Figure Micromolding Approach for Regulating the Microstructures of Polymeric Films for Triboelectric Nanogenerators
A triboelectric nanogenerator
(TENG) is an innovative kind of energy
harvester recently developed on the basis of organic materials for
converting mechanical energy into electricity through the combined
use of the triboelectric effect and electrostatic induction. Polymeric
materials and their microstructures play key roles in the generation,
accumulation, and retainment of triboelectric charges, which decisively
determines the final electric performance of TENGs. Herein we report
a simple and efficient breath figure (BF) micromolding approach to
rapidly regulate the surface microstructures of polymeric films for
the assembly of TENGs. Honeycomb porous films with adjustable pore
size and dimensional architectures were first prepared by the BF technique
through simply adjusting the concentration of the polymer solution.
They were then used as negative molds for straightforward synthesis
of polydimethylsiloxane (PDMS) films with different microlens arrays
(MLAs) and lens sizes, which were further assembled for TENGs to investigate
the influence of film microstructures. All MLA-based TENGs were found
to have an obviously enhanced electric performance in comparison with
a flat-PDMS-film-based TENG. Specifically, up to 3 times improvement
in the electric performance can be achieved by the MLA-based TENG
with optimal surface microstructures over flat-PDMS-film-based TENG
under the same triggering conditions. A MLA-based TENG was further
successfully used to harvest the waste mechanical energy generated
by different human body motions, including finger tapping, hand clapping,
and walking with a frequency ranging from 0.5 to 5.5 Hz
Diastereo- and Enantioselective Asymmetric Hydrogenation of α‑Amido-β-keto Phosphonates via Dynamic Kinetic Resolution
Dynamic kinetic resolution of various α-amido-β-keto phosphonates via asymmetric hydrogenation proceeded efficiently to give the corresponding β-hydroxy-α-amido phosphonates in high diastereo- and enantioselectivities (up to 99:1 syn/anti, 99.8% ee). The addition of catalytic amounts of CeCl<sub>3</sub>·7H<sub>2</sub>O is necessary to achieve both good selectivity and catalytic efficiency under mild reaction conditions
Edge Structural Stability and Kinetics of Graphene Chemical Vapor Deposition Growth
The energetics and growth kinetics of graphene edges during CVD growth on Cu(111) and other catalyst surfaces are explored by density functional theory (DFT) calculations. Different from graphene edges in vacuum, the reconstructions of both armchair (AC) and zigzag (ZZ) edges are energetically less stable because of the passivation of the edges by the catalytic surface. Furthermore, we predicated that, on the most used Cu(111) catalytic surface, each AC-like site on the edge is intended to be passivated by a Cu atom. Such an unexpected passivation significantly lowers the barrier of incorporating carbon atoms onto the graphene edge from 2.5 to 0.8 eV and therefore results in a very fast growth of the AC edge. These theoretical results are successfully applied to explain the broad experimental observations that the ZZ egde is the dominating edge type of growing graphene islands on a Cu surface
Enantioselective Hydrogenation of β‑Ketophosphonates with Chiral Ru(II) Catalysts
Highly effective asymmetric hydrogenation of β-ketophosphonates
in the presence of Ru–(<i>S</i>)-SunPhos as catalyst
was realized; good to excellent enantioselectivities (up to 99.9%
ee) and excellent diastereoselectivities (96:4) were obtained
Enantioselective Ruthenium(II)/Xyl-SunPhos/Daipen-Catalyzed Hydrogenation of γ‑Ketoamides
A series of γ-hydroxy amides
were synthesized with high enantioselectivities
(up to 99%) using asymmetric hydrogenation of the corresponding γ-ketoamides
in the presence of Ru-Xyl-SunPhos-Daipen catalyst providing key building
blocks for a variety of naturally occurring and biologically active
compounds
Ruthenium-Catalyzed Enantioselective Hydrogenation of Aryl-Pyridyl Ketones
Various substituted aryl-pyridyl ketones were hydrogenated
in the
presence of Ru-XylSunPhos-Daipen bifunctional catalytic system with
enantiomeric excesses up to 99.5%. Upon introduction of a readily
removable <i>ortho</i>-bromo atom to the phenyl ring, enantiomerically
enriched 4-chlorophenylpyridylmethanol was obtained by hydrogenation method
with 97.3% ee, which provided an important chiral intermediate for
some histamine H<sub>1</sub> antagonists
Graphene-Bridged Multifunctional Flexible Fiber Supercapacitor with High Energy Density
Portable
fiber supercapacitors with high-energy storage capacity are in great
demand to cater for the rapid development of flexible and deformable
electronic devices. Hence, we employed a 3D cellular copper foam (CF)
combined with the graphene sheets (GSs) as the support matrix to bridge
the active material with nickel fiber (NF) current collector, significantly
increasing surface area and decreasing the interface resistance. In
comparison to the active material directly growing onto the NF in
the absence of CF and GSs, our rationally designed architecture achieved
a joint improvement in both capacity (0.217 mAh cm<sup>–2</sup>/1729.413 mF cm<sup>–2</sup>, 1200% enhancement) and rate
capability (87.1% from 1 to 20 mA cm<sup>–2</sup>, 286% improvement),
which has never been achieved before with other fiber supercapacitors.
The in situ scanning electron microscope (SEM) microcompression test
demonstrated its superior mechanical recoverability for the first
time. Importantly, the assembled flexible and wearable device presented
a superior energy density of 109.6 μWh cm<sup>–2</sup> at a power density of 749.5 μW cm<sup>–2</sup>, and
the device successfully coupled with a flexible strain sensor, solar
cell, and nanogenerator. This rational design should shed light on
the manufacturing of 3D cellular architectures as microcurrent collectors
to realize high energy density for fiber-based energy storage devices
Graphene-Bridged Multifunctional Flexible Fiber Supercapacitor with High Energy Density
Portable
fiber supercapacitors with high-energy storage capacity are in great
demand to cater for the rapid development of flexible and deformable
electronic devices. Hence, we employed a 3D cellular copper foam (CF)
combined with the graphene sheets (GSs) as the support matrix to bridge
the active material with nickel fiber (NF) current collector, significantly
increasing surface area and decreasing the interface resistance. In
comparison to the active material directly growing onto the NF in
the absence of CF and GSs, our rationally designed architecture achieved
a joint improvement in both capacity (0.217 mAh cm<sup>–2</sup>/1729.413 mF cm<sup>–2</sup>, 1200% enhancement) and rate
capability (87.1% from 1 to 20 mA cm<sup>–2</sup>, 286% improvement),
which has never been achieved before with other fiber supercapacitors.
The in situ scanning electron microscope (SEM) microcompression test
demonstrated its superior mechanical recoverability for the first
time. Importantly, the assembled flexible and wearable device presented
a superior energy density of 109.6 μWh cm<sup>–2</sup> at a power density of 749.5 μW cm<sup>–2</sup>, and
the device successfully coupled with a flexible strain sensor, solar
cell, and nanogenerator. This rational design should shed light on
the manufacturing of 3D cellular architectures as microcurrent collectors
to realize high energy density for fiber-based energy storage devices
Graphene-Bridged Multifunctional Flexible Fiber Supercapacitor with High Energy Density
Portable
fiber supercapacitors with high-energy storage capacity are in great
demand to cater for the rapid development of flexible and deformable
electronic devices. Hence, we employed a 3D cellular copper foam (CF)
combined with the graphene sheets (GSs) as the support matrix to bridge
the active material with nickel fiber (NF) current collector, significantly
increasing surface area and decreasing the interface resistance. In
comparison to the active material directly growing onto the NF in
the absence of CF and GSs, our rationally designed architecture achieved
a joint improvement in both capacity (0.217 mAh cm<sup>–2</sup>/1729.413 mF cm<sup>–2</sup>, 1200% enhancement) and rate
capability (87.1% from 1 to 20 mA cm<sup>–2</sup>, 286% improvement),
which has never been achieved before with other fiber supercapacitors.
The in situ scanning electron microscope (SEM) microcompression test
demonstrated its superior mechanical recoverability for the first
time. Importantly, the assembled flexible and wearable device presented
a superior energy density of 109.6 μWh cm<sup>–2</sup> at a power density of 749.5 μW cm<sup>–2</sup>, and
the device successfully coupled with a flexible strain sensor, solar
cell, and nanogenerator. This rational design should shed light on
the manufacturing of 3D cellular architectures as microcurrent collectors
to realize high energy density for fiber-based energy storage devices
Graphene-Bridged Multifunctional Flexible Fiber Supercapacitor with High Energy Density
Portable
fiber supercapacitors with high-energy storage capacity are in great
demand to cater for the rapid development of flexible and deformable
electronic devices. Hence, we employed a 3D cellular copper foam (CF)
combined with the graphene sheets (GSs) as the support matrix to bridge
the active material with nickel fiber (NF) current collector, significantly
increasing surface area and decreasing the interface resistance. In
comparison to the active material directly growing onto the NF in
the absence of CF and GSs, our rationally designed architecture achieved
a joint improvement in both capacity (0.217 mAh cm<sup>–2</sup>/1729.413 mF cm<sup>–2</sup>, 1200% enhancement) and rate
capability (87.1% from 1 to 20 mA cm<sup>–2</sup>, 286% improvement),
which has never been achieved before with other fiber supercapacitors.
The in situ scanning electron microscope (SEM) microcompression test
demonstrated its superior mechanical recoverability for the first
time. Importantly, the assembled flexible and wearable device presented
a superior energy density of 109.6 μWh cm<sup>–2</sup> at a power density of 749.5 μW cm<sup>–2</sup>, and
the device successfully coupled with a flexible strain sensor, solar
cell, and nanogenerator. This rational design should shed light on
the manufacturing of 3D cellular architectures as microcurrent collectors
to realize high energy density for fiber-based energy storage devices