On page 6845, Q. Zhang, M.‐M. Titirici, F. Wei, and co‐workers describe a bifunctional graphene catalyst with abundant topological defects through the facile carbonization of natural gelatinized ...sticky rice and probe the underlying oxygen electrocatalytic mechanism. A nitrogen‐free configuration with adjacent pentagon and heptagon carbon rings is revealed to exhibit the lowest overpotential for both oxygen reduction and evolution catalysis.
We analyze a recently proposed model for the interaction of an electron with a nonuniform electric field under the influence of a cut-off point induced by the topology of a spiral dislocation (Maia ...and Bakke, 2021). We show that the analytical eigenvalues derived by the authors are qualitatively and quantitatively incorrect. Besides, the infinite degeneracy of the energy levels and the limit on the possible values of the radial quantum number predicted by the authors are mere artifacts of the approximation used to solve the differential equation.
•Electron in a nonuniform electric field with Dirichlet boundary condition produced by a spiral dislocation.•The radial eigenvalue equation can be solved numerically.•The analytical eigenvalues derived previously by other authors are qualitatively and quantitatively incorrect.•The predicted limit on the radial quantum number is an artifact of the approximation used.•The infinite degeneracy of the energy levels is also an artifact of the approximation just mentioned.
Two‐dimensional liquid‐crystal elastomer (LCE) sheets with preprogrammed topological defects are prepared by aligning liquid‐crystal monomers within micropatterned epoxy channels, followed by ...photopolymerization. Upon heating, the LCE films form various three‐dimensional structures in agreement with theoretical design. The miniaturized LCE actuators offer large‐area work capacities (≈1.05 J m–2) to lift over 700 times their own weight.
It was recently realized that topological spin textures do not merely have mathematical beauty but can also give rise to unique functionalities of magnetic materials. An example is the skyrmion—a ...nano-sized bundle of noncoplanar spins—that by virtue of its nontrivial topology acts as a flux of magnetic field on spin-polarized electrons. Lorentz transmission electron microscopy recently emerged as a powerful tool for direct visualization of skyrmions in noncentrosymmetric helimagnets. Topologically, skyrmions are equivalent to magnetic bubbles (cylindrical domains) in ferromagnetic thin films, which were extensively explored in the 1970s for data storage applications. In this study we use Lorentz microscopy to image magnetic domain patterns in the prototypical magnetic oxide–M-type hexaferrite with a hint of scandium. Surprisingly, we find that the magnetic bubbles and stripes in the hexaferrite have a much more complex structure than the skyrmions and spirals in helimagnets, which we associate with the new degree of freedom—helicity (or vector spin chirality) describing the direction of spin rotation across the domain walls. We observe numerous random reversals of helicity in the stripe domain state. Random helicity of cylindrical domain walls coexists with the positional order of magnetic bubbles in a triangular lattice. Most unexpectedly, we observe regular helicity reversals inside skyrmions with an unusual multiple-ring structure.
Hopfions emerge in ferroelectrics Luk'yanchuk, I; Tikhonov, Y; Razumnaya, A ...
Nature communications,
05/2020, Letnik:
11, Številka:
1
Journal Article
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Paradigmatic knotted solitons, Hopfions, that are characterized by topological Hopf invariant, attract an intense attention in the diverse areas of physics ranging from high-energy physics, cosmology ...and astrophysics to biology, magneto- and hydrodynamics and condensed matter physics. Yet, while being of broad interest, they remain elusive and under-explored. Here we demonstrate that Hopfions emerge as a basic configuration of polarization field in confined ferroelectric nanoparticles. Our findings establish that Hopfions are of fundamental importance for the electromagnetic behavior of the nanocomposits and can result in advanced functionalities of these materials.
Carbon-based materials are emerging as a type of inexpensive and efficient adsorbent, although their genuine adsorption site is still debatable. Herein, we present a novel approach for designing and ...constructing an ultra-thin defect-rich hierarchically porous carbon nanosheet (ZG-C). The ZG-C sample demonstrated a high adsorption capacity for bisphenol A (BPA) (602.2 mg/g) along with a fast adsorption process (20 min), and stable reusability (the decline efficiency was 9.14% after five consecutive cycles). Based on comprehensive experiments and a number of characterizations, the high adsorption capacity of ZG-C for BPA was connected with the hierarchical porous structure of ZG-C and multiple intrinsic defects of ZG-C. The results of density functional theory (DFT) further demonstrated that topological defects played an indispensable role in promoting adsorption, and its adsorption energy (−0.595 eV) for BPA was much higher than that of other intrinsic defects. This study not only provides an innovative and simple strategy for preparing hierarchically porous carbon-based adsorbent with abundant intrinsic defects for the efficient removal of BPA, but also significantly contributes to the understanding of the application of carbon-based materials to remove bisphenols.
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•Ultrathin defect-rich hierarchically porous carbon nanosheet (ZG-C) was fabricated.•ZG-C had high adsorption capacity, short equilibrium time and good reusability.•Intrinsic defects were one of the main adsorption sites.•The effect of topological defects was more important than other types of defects.
A plasmonic photopatterning technique is proposed and demonstrated for aligning the molecular orientation in liquid crystals (LCs) in patterns with designer complexity. Using plasmonic metamasks in ...which target molecular directors are encoded, LC alignments of arbitrary planar patterns can be achieved in a repeatable and scalable fashion withunprecedentedly high spatial resolution and high throughput.
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