RESUMEN
Electromagnetic (EM) wave absorption materials have attracted considerable attention because of EM wave pollution caused by the proliferation of electronic communication devices. One-dimentional (1D) structural magnetic metals have potential as EM absorption materials. However, fabricating 1D core-shell bimetallic magnetic species is a significant challenge. Herein, 1D core-shell bimetallic magnetic chains are successfully prepared through a modified galvanic replacement reaction under an external magnetic field, which could facilitate the preparation of 1D core-shell noble magnetic chains. By delicately designing the orientation of bimetallic magnetic chains in polyvinylidene fluoride, the composites reveal the decreased complex permittivity and increased permeability compared with random counterparts. Thus, elevated EM wave absorption perfromances including an optimal reflection loss of -43.5 dB and an effective bandwidth of 7.3 GHz could be achieved for the oriented Cu@Co sample. Off-axis electron holograms indicate that the augmented magnetic coupling and remarkable polarization loss primarily contribute to EM absorption in addition to the antenna effect of the 1D structure to scatter microwaves and ohmic loss of the metallic attribute. This work can serve a guide to construct 1D core-shell bimetallic magnetic nanostructures and design magnetic configuration in polymer to tune EM parameters and strengthen EM absorption properties.
RESUMEN
Core@shell structures have been attracting extensive attention to boost microwave absorption (MA) performance due to the unique interfacial polarization. However, it still remains a challenge to synthesize sophisticated 1D semiconductor-based materials with excellent MA competence. Herein, a hierarchical cable-like TiO2 @Fe3 O4 @PPy is fabricated by a sequential process of solvothermal treatment and polymerization. The complex permittivity of ternary composites can be optimized by tunable PPy coating thickness to improve the loss ability. The maximum reflection loss can reach -61.8 dB with a thickness of 3.2 mm while the efficient absorption bandwidth can achieve over 6.0 GHz, which involves the X and Ku band at only a 2.2 mm thickness. Importantly, the heterojunction contacts constructed by PPy-Fe3 O4 and Fe3 O4 -TiO2 contribute to the enhanced polarization loss. Besides, the configuration of magnetic Fe3 O4 sandwiched between dielectric TiO2 and PPy facilitates the magnetic stray field to radiate into the TiO2 core and out of the PPy shell, which significantly promotes magnetic-dielectric synergy. Electron holography validates the distinct charge distribution and magnetic coupling. The new findings might shed light on novel structures for functional core@shell composites and the design of semiconductor-based materials for microwave absorption.
RESUMEN
Antibodies against N-methyl-D-aspartate receptors (NMDARs) are most frequently detected in persons with autoimmune encephalitis (AE) and used as diagnostic biomarkers. Elucidating the structural basis of monoclonal antibody (mAb) binding to NMDARs would facilitate the development of targeted therapy for AE. Here, we reconstructed nanodiscs containing green fluorescent protein-fused NMDARs to label and sort individual immune B cells from persons with AE and further cloned and identified mAbs against NMDARs. This allowed cryo-electron microscopy analysis of NMDAR-Fab complexes, revealing that autoantibodies bind to the R1 lobe of the N-terminal domain of the GluN1 subunit. Small-angle X-ray scattering studies demonstrated NMDAR-mAb stoichiometry of 2:1 or 1:2, structurally suitable for mAb-induced clustering and endocytosis of NMDARs. Importantly, these mAbs reduced the surface NMDARs and NMDAR-mediated currents, without tonically affecting NMDAR channel gating. These structural and functional findings imply that the design of neutralizing antibody binding to the R1 lobe of NMDARs represents a potential therapy for AE treatment.
RESUMEN
Aiming to solve the poor response of titanium dioxide (TiO2) in the microwave frequency, versatile series of N-doped carbon (NC) components are employed to improve the conductivity and polarization strength of TiO2-based composites. The bimetallic zeolitic imidazolate framework-derived TiO2@NC complex (TNC-3) exhibits hierarchical microstructures and large-scale hetero-interfaces, whereas the pyrolysis composite of metal-polydopamine-coated TiO2 (TNC-4) possesses the vesicle-like NC shell and bulk TiO2 core. Thus, the optimal reflection loss and efficient absorption bandwidth of TNC-3 realize -44.0 dB at 3.0 mm and 5.4 GHz at only 2.0 mm of coating thickness, respectively. Nevertheless, the corresponding attenuation ability of TNC-4 is separately -24.3 dB and 4.8 GHz with a thickness of 5.0 and 2.0 mm, respectively. Importantly, the conduction and polarization loss can be enhanced by the large-scale interfacial contacts between nanoscale rutile nanoparticles and hierarchical graphitized carbon. Meanwhile, the superior performance of TNC-3 stems from the large proportion of pyridinic N and pyrrolic N, which provides asymmetric lone pairs to strengthen the dipole rotation. These results are of great value in constructing semiconductor-based complexes by carbon-coating engineering as functional materials.
RESUMEN
The electrochemical properties of layered cathodes can be enhanced by doping with aluminium. However, understanding of the underlying mechanism of Al ion behaviour is deficient, which obstructs its further application. Herein, we adjusted the aluminium content in model LiNi0.85-xCo0.15AlxO2 (LNCA) materials; the sample with the optimum aluminium content (x = 0.05) exhibited excellent electrochemical performance (98.6% capacity retention at 275 mA g-1). Meanwhile, for the samples with excessive aluminium (x = 0.15, 0.30), fast decay of the cycling stability could be observed. Meanwhile, their reversible capacities in the initial cycles were also greatly inferior to the theoretical values. These abnormal phenomena can be attributed to structure cracking and the impedance of Li-ion migration in samples with higher aluminium content. According to the microstructure observations, an unexpected beneficial heterostructure was found to cover the samples with optimum aluminium content, while in the samples with higher aluminium content, this heterostructure was not present. Furthermore, as confirmed by activation barrier calculations, Al ions were found to prefer to thermodynamically occupy the tetrahedral interstices instead of the octahedral sites in Li layers in a high delithiation state. Due to this selective occupancy, proper aluminium content can improve the stability of layered cathodes during cycling. However, excessive aluminium content instead impedes the formation of beneficial surface heterogeneity during synthesis and deeply affects Li-ion migration during cycling. Therefore, the electrochemical performance of the samples with higher aluminium content suffered severe decay. These results and discoveries significantly advance the guidance of microstructural design for next-generation layered cathode materials.