Interface Strategy To Achieve Tunable High Frequency Attenuation

Among all polarizations, the interface polarization effect is the most effective, especially at high frequency. The design of various ferrite/iron interfaces can significantly enhance the materials’ dielectric loss ability at high frequency. This paper presents a simple method to generate ferrite/iron interfaces to enhance the microwave attenuation at high frequency. The ferrites were coated onto carbonyl iron and could be varied to ZnFe₂O₄, CoFe₂O₄, Fe₃O₄, and NiFe₂O₄. Due to the ferrite/iron interface inducing a stronger dielectric loss effect, all of these materials achieved broad effective frequency width at a coating layer as thin as 1.5 mm. In particular, an effective frequency width of 6.2 GHz could be gained from the Fe@NiFe₂O₄ composite

Optimization of Zn_<i>x</i>Fe_3–<i>x</i>O₄ Hollow Spheres for Enhanced Microwave Attenuation

We report here the composition optimization of Zn_<i>x</i>Fe_3–<i>x</i>O₄ hollow nanospheres for enhancing microwave attenuation. Zn_<i>x</i>Fe_3–<i>x</i>O₄ hollow nanospheres were synthesized through a simple solvothermal process. The maximum magnetization moment of 91.9 emu/g can be obtained at <i>x</i> = 0.6. The composite filled with Zn_0.6Fe_2.4O₄ exhibited the bandwidth of 3.21–8.33 GHz for RL < −10 dB and a maximum relative bandwidth (<i>W</i>_p,max) of 88.6% at optimized thickness <i>t</i>₀ = 0.34 cm. The enhancement should be attributed to the enhanced permeability resonance at high frequency. This optimized hollow material is very promising to be used as a mass efficient and broadband microwave attenuation material

Smart Magnetic Nanosensors Synthesized through Layer-by-Layer Deposition of Molecular Beacons for Noninvasive and Longitudinal Monitoring of Cellular mRNA

Noninvasive and longitudinal monitoring of gene expression in living cells is essential for understanding and monitoring cellular activities. Herein, a smart magnetic nanosensor is constructed for the real-time, noninvasive, and longitudinal monitoring of cellular mRNA expression through the layer-by-layer deposition of molecular beacons (MBs) and polyethylenimine on the iron oxide nanoparticles. The loading of MBs, responsible for the signal intensity and the tracking time, was easily tuned with the number of layers incorporated. The idea was first demonstrated with the magnetic nanosensors for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA, which was efficiently internalized into the cells under the influence of magnetic field. This nanosensor allowed the continuous monitoring of the cellular GAPDH mRNA expression for 1 month. Then this platform was further utilized to incorporate two kinds of MBs for alkaline phosphatase (ALP) and GAPDH mRNAs, respectively. The multifunctional nanosensors permitted the simultaneous monitoring of the reference gene (GAPDH mRNA) and the early osteogenic differentiation marker (ALP mRNA) expression. When the fluorescence signal ratio between ALP mRNA MBs and GAPDH mRNA MBs was taken, the dynamic osteogenic differentiation process of MSCs was accurately monitored

Interface Polarization Strategy to Solve Electromagnetic Wave Interference Issue

Design of an interface to arouse interface polarization is an efficient route to attenuate high-frequency electromagnetic waves. The attenuation intensity is highly related to the contact area. To achieve stronger interface polarization, growing metal oxide granular film on graphene with a larger surface area seems to be an efficient strategy due to the high charge carrier concentration of graphene. This study is devoted to fabricating the filmlike composite by a facile thermal decomposition method and investigating the relationship among contact area, polarization intensity, and the type of metal oxide. Because of the high-frequency polarization effect, the composites presented excellent electromagnetic wave attenuation ability. It is shown that the optimal effective frequency bandwidth of graphene/metal oxide was close to 7.0 GHz at a thin coating layer of 2.0 mm. The corresponding reflection loss value was nearly −22.1 dB. Considering the attenuation mechanism, interface polarization may play a key role in the microwave-absorbing ability

Novel Conjugated Ladder-Structured Oligomer Anode with High Lithium Storage and Long Cycling Capability

Herein we report the development of nanostructured poly­(1,4-dihydro-11H-pyrazino­[2′,3′:3,4]­cyclopenta­[1,2-<i>b</i>]­quinoxalin-11-one) (PPCQ), a novel conjugated ladderlike oligomer with the presence of a rich amount of heteroatoms, as the anode material. Beyond its remarkable lithium storage of 972 mAh g^–1 after 120 cycles, the superior cycle life and stable capacity performance of 489 mAh g^–1 revealed by ultralong testing of 1000 cycles (with an average Coulombic efficiency 99.8%) at a high current density of 2.5 A g^–1 indicate its excellent electrochemical stability to be promisingly applied for high-performance lithium-ion batteries (LIBs)

Supplemental material for Detection of Bacteria in Water with β-Galactosidase-Coated Magnetic Nanoparticles

<p>Supplemental material for Detection of Bacteria in Water with β-Galactosidase-Coated Magnetic Nanoparticles by Mingyue Cui, Hao Chang, Yang Zhong, Min Wang, Tianze Wu, Xiao Hu, Zhichuan J. Xu, and Chenjie Xu in SLAS Technology</p

β‑FeOOH: An Earth-Abundant High-Capacity Negative Electrode Material for Sodium-Ion Batteries

Thanks to the great earth abundance and excellent energy density of sodium, sodium-ion batteries are promising alternative energy storage devices for large-scale applications. Developing cheap, safe, and high-capacity sodium-ion battery anode materials is one of the critical challenges in this field. Here, we show that β-FeOOH is a very promising low-cost anode material, with a high reversible capacity (>500 mAh g^–1 during initial cycles). The fundamental characteristics associated with the discharge/charge processes, in terms of the redox reactions, formation/deformation of the solid electrolyte interface (SEI) layers, and structural and morphological changes, are comprehensively investigated. In addition, a comparison study shows that the smaller-sized FeOOH has more serious kinetic restrictions, and thus lower capacities, while it shows better cyclability than the bigger one. Origins of the large overpotential are discussed, and it is suggested that the overpotential should be mainly due to the features of the surface-concentration-dependent potential and the slow diffusion of Na⁺; in addition, the presence of the SEI layers may also contribute to the overpotential

Degree of Geometric Tilting Determines the Activity of FeO₆ Octahedra for Water Oxidation

Fe oxides and (oxy)­hydroxides are promising cost-effective catalysts for scalable water electrolysis. For an improvement in the understanding of the structural factors required by the most active Fe sites, the role of geometric tilting in determining the activity of the FeO₆ octahedron for water oxidation was investigated. The catalytic performance of the FeO₆ octahedron in a series of crystalline structures, i.e., perovskites AFeO₃, spinel ZnFe₂O₄, and β-FeOOH, was found to be negatively correlated with their octahedral tilting degree. This correlation was rationalized through the Fe–O covalency, which is reflected by the O 2p band center as well as the charge-transfer energy obtained from ab initio calculations. Thus, it was disclosed that FeO₆ octahedral tilting alters the activity for water oxidation through changing the covalency degree of Fe–O bonds

Electrochemical Approach for Effective Antifouling and Antimicrobial Surfaces

Biofouling, the adsorption of organisms to a surface, is a major problem today in many areas of our lives. This includes: (i) health, as biofouling on medical device leads to hospital-acquired infections, (ii) water, since the accumulation of organisms on membranes and pipes in desalination systems harms the function of the system, and (iii) energy, due to the heavy load of the organic layer that accumulates on marine vessels and causes a larger consumption of fuel. This paper presents an effective electrochemical approach for generating antifouling and antimicrobial surfaces. Distinct from previously reported antifouling or antimicrobial electrochemical studies, we demonstrate the formation of a hydrogen gas bubble layer through the application of a low-voltage square-waveform pulses to the conductive surface. This electrochemically generated gas bubble layer serves as a separation barrier between the surroundings and the target surface where the adhesion of bacteria can be deterred. Our results indicate that this barrier could effectively reduce the adsorption of bacteria to the surface by 99.5%. We propose that the antimicrobial mechanism correlates with the fundamental of hydrogen evolution reaction (HER). HER leads to an arid environment that does not allow the existence of live bacteria. In addition, we show that this drought condition kills the preadhered bacteria on the surface due to water stress. This work serves as the basis for the exploration of future self-sustainable antifouling techniques such as incorporating it with photocatalytic and photoelectrochemical reactions

Tailoring the Co 3d‑O 2p Covalency in LaCoO₃ by Fe Substitution To Promote Oxygen Evolution Reaction

LaCoO₃ is an active, stable catalyst in alkaline solution for oxygen evolution reaction (OER). With lower cost, it is a potential alternative to precious metal oxides like IrO₂ and RuO₂ in water electrolysis. However, room still remains for improving its activity according to recent understandings of OER on perovskite oxides. In this work, Fe substitution has been introduced in LaCoO₃ to boost its OER performance. Density function theory (DFT) calculation verified that the enhanced performance originates from the enhanced Co 3d-O 2p covalency with 10 at% Fe substitution in LaCoO₃. Both DFT calculations and Superconducting Quantum Design (SQUID) magnetometer (MPMS-XL) showed a Co³⁺ spin state transition from generally low spin state (LS: t_2g⁶ e_g⁰, S = 0) to a higher spin state with the effect of 10 at% Fe substitution. X-ray absorption near-edge structure (XANES) supports DFT calculations on an insulator to half-metal transition with 10 at% Fe substitution, induced by spin state transition. The half-metallic LaCo_0.9Fe_0.1O₃ possesses increased overlap between Co 3d and O 2p states, which results in enhanced covalency and promoted OER performance. This finding enlightens a new way of tuning the metal–oxygen covalency in oxide catalysts for OER