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"Shu Yu"
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A multi-responsive healable supercapacitor
Self-healability is essential for supercapacitors to improve their reliability and lifespan when powering the electronics. However, the lack of a universal healing mechanism leads to low capacitive performance and unsatisfactory intelligence. Here, we demonstrate a multi-responsive healable supercapacitor with integrated configuration assembled from magnetic Fe
3
O
4
@Au/polyacrylamide (MFP) hydrogel-based electrodes and electrolyte and Ag nanowire films as current collectors. Beside a high mechanical strength, MFP hydrogel exhibits fast optical and magnetic healing properties arising from distinct photothermal and magneto-thermal triggered interfacial reconstructions. By growing electroactive polypyrrole nanoparticles into MFP framework as electrodes, the assembled supercapacitor exhibits triply-responsive healing performance under optical, electrical and magnetic stimuli. Notably, the device delivers a highest areal capacitance of 1264 mF cm
−2
among the reported healable supercapacitors and restores ~ 90% of initial capacitances over ten healing cycles. These prominent performance advantages along with the facile device-assembly method make this emerging supercapacitor highly potential in the next-generation electronics.
Self-healing property is important for supercapacitors when powering the electronics, but designing devices that possess a universal healing mechanism remains challenging. Here, the authors achieve an optically, electrically, and magnetically-responsive self-healing device with integrated configuration.
Journal Article
Anisotropic and self-healing hydrogels with multi-responsive actuating capability
Inspired by smart biological tissues, artificial muscle-like actuators offer fascinating prospects due to their distinctive shape transformation and self-healing function under external stimuli. However, further practical application is hindered by the lack of simple and general routes to fabricate ingenious soft materials with anisotropic responsiveness. Here, we describe a general in situ polymerization strategy for the fabrication of anisotropic hydrogels composed of highly-ordered lamellar network crosslinked by the metal nanostructure assemblies, accompanied with remarkably anisotropic performances on mechanical, optical, de-swelling and swelling behaviors. Owing to the dynamic thiolate-metal coordination as healing motifs, the composites exhibit rapid and efficient multi-responsive self-healing performance under NIR irradiation and low pH condition. Dependent on well-defined anisotropic structures, the hydrogel presents controllable solvent-responsive mechanical actuating performance. Impressively, the integrated device through a healing-induced assembly way can deliver more complicated, elaborate forms of actuation, demonstrating its great potentials as superior soft actuators like smart robots.
The development of artificial muscle-like actuators is often hampered by the lack of general fabrication routes towards anisotropic responsive materials. Here, the authors fabricate anisotropic hydrogels by an in-situ polymerization strategy of a lamellar network, crosslinked by metal nanostructure assemblies.
Journal Article
Relaxing the cosmological moduli problem by low-scale inflation
A
bstract
We show that the cosmological abundance of string axions is much smaller than naive estimates if the Hubble scale of inflation,
H
inf
, is sufficiently low (but can still be much higher than the axion masses) and if the inflation lasts sufficiently long. The reason is that the initial misalignment angles of the string axions follow the Bunch-Davies distribution peaked at the potential minima. As a result, the cosmological moduli problem induced by the string axions can be significantly relaxed by low-scale inflation, and astrophysical and cosmological bounds are satisfied over a wide range of the mass without any fine-tuning of the initial misalignment angles. Specifically, the axion with its decay constant
f
ϕ
= 10
16
GeV satisfies the bounds over 10
−18
eV ≲
m
ϕ
≲ 10 TeV for
H
inf
≲ 10 keV-10
6
GeV. We also discuss cases with multiple axions and the QCD axion.
Journal Article
Unconventional CN vacancies suppress iron-leaching in Prussian blue analogue pre-catalyst for boosted oxygen evolution catalysis
The incorporation of defects, such as vacancies, into functional materials could substantially tailor their intrinsic properties. Progress in vacancy chemistry has enabled advances in many technological applications, but creating new type of vacancies in existing material system remains a big challenge. We show here that ionized nitrogen plasma can break bonds of iron-carbon-nitrogen-nickel units in nickel-iron Prussian blue analogues, forming unconventional carbon-nitrogen vacancies. We study oxygen evolution reaction on the carbon-nitrogen vacancy-mediated Prussian blue analogues, which exhibit a low overpotential of 283 millivolts at 10 milliamperes per square centimeter in alkali, far exceeding that of original Prussian blue analogues and previously reported oxygen evolution catalysts with vacancies. We ascribe this enhancement to the in-situ generated nickel-iron oxy(hydroxide) active layer during oxygen evolution reaction, where the Fe leaching was significantly suppressed by the unconventional carbon-nitrogen vacancies. This work opens up opportunities for producing vacancy defects in nanomaterials for broad applications.
Defect-engineering offers a promising route to vary material properties and reactivities, although the achievable defect types are limited. Here, the authors introduced unusual CN-vacancies in Prussian blue analogue pre-catalysts that can limit Fe leaching and improve oxygen evolution performances.
Journal Article
An asymmetric SIMP dark matter model
A
bstract
In this paper, we construct the first asymmetric strongly interacting massive particles (SIMP) dark matter (DM) model, where a new vector-like fermion and a new complex scalar both having nonzero chemical potentials can be asymmetric DM particles. After the spontaneous breaking of a U(1)
D
dark gauge symmetry, these two particles can have accidental ℤ
4
charges making them stable. By adding one more complex scalar as a mediator between the SIMP DM, the relic density of DM is determined by 3 → 2 and two-loop induced 2 → 2 annihilations in this model. On the other hand, the SIMP DM can maintain kinetic equilibrium with the thermal bath until the DM freeze-out temperature via the new gauge interaction. Interestingly, this model can have a bouncing effect on DM, whereby the DM number density rises after the chemical freeze-out of DM. With this effect, the prediction of the DM self-interacting cross section in this model can be consistent with astrophysical observations, and the ratio of the DM energy density to the baryonic matter energy density can be explained by primordial asymmetries. We also predict the DM-electron elastic scattering cross section that can be used to test this model in future projected experiments.
Journal Article