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Defect and interface engineering are efficient approaches to adjust the physical and chemical properties of nanomaterials. In order to effectively utilize these strategies for the improvement of microwave absorption properties (MAPs), in this study, we reported the synthesis of hollow carbon shells and hollow carbon@MoS 2 nanocomposites by the template-etching and template-etching-hydrothermal methods, respectively. The obtained results indicated that the degree of defect for hollow carbon shells and hollow carbon@MoS 2 could be modulated by the thickness of hollow carbon shell, which effectively fulfilled the optimization of electromagnetic parameters and improvement of MAPs. Furthermore, the microstructure investigations revealed that the precursor of hollow carbon shells was encapsulated by the sheet-like MoS 2 in high efficiency. And the introduction of MoS 2 nanosheets acting as the shell effectively improved the interfacial effects and boosted the polarization loss capabilities, which resulted in the improvement of comprehensive MAPs. The elaborately designed hollow carbon@MoS 2 samples displayed very outstanding MAPs including strong absorption capabilities, broad absorption bandwidth, and thin matching thicknesses. Therefore, this work provided a viable strategy to improve the MAPs of microwave absorbers by taking full advantage of their defect and interface engineering.

Background Understanding the in vivo size-dependent pharmacokinetics and toxicity of nanoparticles is crucial to determine their successful development. Systematic studies on the size-dependent biological effects of nanoparticles not only help to unravel unknown toxicological mechanism but also contribute to the possible biological applications of nanomaterial. Methods In this study, the biodistribution and the size-dependent biological effects of Fe 3 O 4 @SiO 2 –NH 2 nanoparticles (Fe@Si-NPs) in three diameters (10, 20 and 40 nm) were investigated by ICP-AES, serum biochemistry analysis and NMR-based metabolomic analysis after intravenous administration in a rat model. Results Our findings indicated that biodistribution and biological activities of Fe@Si-NPs demonstrated the obvious size-dependent and tissue-specific effects. Spleen and liver are the target tissues of Fe@Si-NPs, and 20 nm of Fe@Si-NPs showed a possible longer blood circulation time. Quantitative biochemical analysis showed that the alterations of lactate dehydrogenase (LDH) and uric acid (UA) were correlated to some extent with the sizes of Fe@Si-NPs. The untargeted metabolomic analyses of tissue metabolomes (kidney, liver, lung, and spleen) indicated that different sizes of Fe@Si-NPs were involved in the different biochemical mechanisms. LDH, formate, uric acid, and GSH related metabolites were suggested as sensitive indicators for the size-dependent toxic effects of Fe@Si-NPs. The findings from serum biochemical analysis and metabolomic analysis corroborate each other. Thus we proposed a toxicity hypothesis that size-dependent NAD depletion may occur in vivo in response to nanoparticle exposure. To our knowledge, this is the first report that links size-dependent biological effects of nanoparticles with in vivo NAD depletion in rats. Conclusion The integrated metabolomic approach is an effective tool to understand physiological responses to the size-specific properties of nanoparticles. Our results can provide a direction for the future biological applications of Fe@Si-NPs.

Due to the good manipulation of electronic structure and defect, anion regulating should be a promising strategy to regulate the electromagnetic (EM) parameters and optimize the EM wave absorption performances (EMWAPs). In this work, we proposed a facile route for the large-scale production of core@shell structured hollow carbon spheres@MoS x Se 2− x ( x = 0.2, 0.6, and 1.0) multicomponent nanocomposites (MCNCs) through a mild template method followed by hydrothermal process. The obtained results revealed that the designed hollow carbon spheres@MoS x Se 2− x MCNCs presented the improved sulfur vacancy concentration by regulating the x value from 0.2 to 1.0. The obtained hollow carbon spheres@MoS x Se 2− x MCNCs displayed the extraordinary comprehensive EMWAPs because of the introduced abundant defects and excellent interfacial effects. Furthermore, the as-prepared hollow carbon spheres@MoS x Se 2− x MCNCs presented the progressively improved comprehensive EMWAPs with the x value increasing from 0.2 to 1.0, which could be explained by their boosted polarization loss abilities and impedance matching characteristics originating from the enhanced sulfur vacancy concentration. Therefore, our findings not only demonstrated that the anion regulating was a promising method to optimize EM parameters and EMWAPs, but also provided a facile route to design the transition metal dichalcogenides-based MCNCs as the much more attractive candidates for high-performance microwave absorbers.

The development of Pt-based core/shell nanoparticles represents an emerging class of electrocatalysts for fuel cells, such as methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). Here, we present a one-pot synthesis approach to prepare hexagonal PtBi/Pt core/shell nanostructure composed of an intermetallic Pt 1 Bi 1 core and an ultrathin Pt shell with well-defined shape, size, and composition. The structure and the synergistic effect among different components enhanced their MOR and EOR performance. The optimized Pt 2 Bi nanoplates exhibit excellent mass activities in both MOR (4,820 mA·mgPt –1 ) and EOR (5,950 mA·mgPt –1 ) conducted in alkaline media, which are 6.15 times and 8.63 times higher than those of commercial Pt/C, respectively. Pt 2 Bi nanoplates also show superior operation durability to commercial Pt/C. This work may inspire the rational design and synthesis of Pt-based nanoparticles with improved performance for fuel cells and other applications.

Cobalt ferrite (CoFe 2 O 4 ), with good chemical stability and magnetic loss, can be used to prepare composites with a unique structure and high absorption. In this study, CoFe 2 O 4 @mesoporous carbon hollow spheres (MCHS) with a core-shell structure were prepared by introducing CoFe 2 O 4 magnetic particles into hollow mesoporous carbon through a simple in situ method. Then, the microwave absorption performance of the CoFe 2 O 4 @MCHS composites was investigated. Magnetic and dielectric losses can be effectively coordinated by constructing the porous structure and adjusting the ratio of MCHS and CoFe 2 O 4 . Results show that the impedance matching and absorption properties of the CoFe 2 O 4 @MCHS composites can be altered by tweaking the mass ratio of MCHS and CoFe 2 O 4 . The minimum reflection loss of the CoFe 2 O 4 @MCHS composites reaches -29.7 dB at 5.8 GHz. In addition, the effective absorption bandwidth is 3.7 GHz, with the thickness being 2.5 mm. The boosted microwave absorption can be ascribed to the porous core-shell structure and introduction of magnetic particles. The coordination between the microporous morphology and the core-shell structure is conducive to improving the attenuation coefficient and achieving good impedance matching. The porous core-shell structure provides large solid-void and CoFe 2 O 4 −C interfaces to induce interfacial polarization and extend the electromagnetic waves’ multiple scattering and reflection. Furthermore, natural resonance, exchange resonance, and eddy current loss work together for the magnetic loss. This method provides a practical solution to prepare core-shell structure microwave absorbents.

Controlled photocatalytic conversion of CO2 into premium fuel such as methane (CH4) offers a sustainable pathway towards a carbon energy cycle. However, the photocatalytic efficiency and selectivity are still unsatisfactory due to the limited availability of active sites on the current photocatalysts. To resolve this issue, the design of oxygen vacancies (OVs) in metal–oxide semiconductors is an effective option. Herein, in situ deposition of TiO2 onto SiO2 nanospheres to construct a SiO2@TiO2 core–shell structure was performed to modulate the oxygen vacancy concentrations. Meanwhile, charge redistribution led to the formation of abundant OV‐regulated Ti–Ti (Ti–OV–Ti) dual sites. It is revealed that Ti–OV–Ti dual sites served as the key active site for capturing the photogenerated electrons during light‐driven CO2 reduction reaction (CO2RR). Such electron‐rich active sites enabled efficient CO2 adsorption and activation, thus lowering the energy barrier associated with the rate‐determining step. More importantly, the formation of a highly stable *CHO intermediate at Ti–OV–Ti dual sites energetically favored the reaction pathway towards the production of CH4 rather than CO, thereby facilitating the selective product of CH4. As a result, SiO2@TiO2‐50 with an optimized oxygen vacancy concentration of 9.0% showed a remarkable selectivity (90.32%) for CH4 production with a rate of 13.21 μmol g−1 h−1, which is 17.38‐fold higher than that of pristine TiO2. This study provides a new avenue for engineering superior photocatalysts through a rational methodology towards selective reduction of CO2. In this work, we describe the construction of a SiO2@TiO2 core–shell composite structure through a controlled growth strategy to achieve the precise modulation of the oxygen vacancy (OV) concentration in TiO2. The abundant Ti–OV–Ti dual sites enable not only efficient adsorption and activation of CO2 but also a stable adsorption configuration of the *CHO intermediate, thereby contributing to remarkable catalytic activity and selectivity for photoreduction of CO2 towards CH4.

Material composition and structural design are important factors influencing the electromagnetic wave (EMW) absorption performance of materials. To alleviate the impedance mismatch attributed to the high dielectric constant of Ti3C2Tx MXene, we have successfully synthesized core‐shell structured SiO2@MXene@MoS2 nanospheres. This architecture, comprising SiO2 as the core, MXene as the intermediate layer, and MoS2 as the outer shell, is achieved through an electrostatic self‐assembly method combined with a hydrothermal process. This complex core‐shell structure not only provides a variety of loss mechanisms that effectively dissipate electromagnetic energy but also prevents self‐aggregation of MXene and MoS2 nanosheets. Notably, the synergistic combination of SiO2 and MoS2 with highly conductive MXene enables the suitable dielectric constant of the composites, ensuring optimal impedance matching. Therefore, the core‐shell structured SiO2@MXene@MoS2 nanospheres exhibit excellent EMW absorption performance, featuring a remarkable minimum reflection loss (RLmin) of −52.11 dB (2.4 mm). It is noteworthy that these nanospheres achieve an ultra‐wide effective absorption bandwidth (EAB) of 6.72 GHz. This work provides a novel approach for designing and synthesizing high‐performance EMW absorbers characterized by “wide bandwidth and strong reflection loss.” The sandwich‐like structured SiO2@MXene@MoS2 nanospheres were synthesized by coating MoS2 nanosheets on SiO2@MXene, which is promising for strong electromagnetic wave absorption. Due to the formation of a unique structure, multiple loss mechanisms are achieved by a multipolarization synergistic effect. Thus, SiO2@MXene@MoS2 nanospheres exhibit a remarkable minimum reflection loss of −52.11 dB at 2.4 mm.

HighlightsA simple two-step multi-element co-doping strategy is proposed to fabricate core-shell structured LiCoO2 based on the different diffusivities of dopant ions.The high diffusivity Al3+/Mg2+ ions occupy the core of single-crystal grain while the low diffusivity Ti4+ ions enrich the shell layer. In-situ XRD demonstrates the mitigated structural distortion under a high cut-off voltage of 4.6 V, resulting in a significantly improved cycling stability.Inactive elemental doping is commonly used to improve the structural stability of high-voltage layered transition-metal oxide cathodes. However, the one-step co-doping strategy usually results in small grain size since the low diffusivity ions such as Ti4+ will be concentrated on grain boundaries, which hinders the grain growth. In order to synthesize large single-crystal layered oxide cathodes, considering the different diffusivities of different dopant ions, we propose a simple two-step multi-element co-doping strategy to fabricate core–shell structured LiCoO2 (CS-LCO). In the current work, the high-diffusivity Al3+/Mg2+ ions occupy the core of single-crystal grain while the low diffusivity Ti4+ ions enrich the shell layer. The Ti4+-enriched shell layer (~ 12 nm) with Co/Ti substitution and stronger Ti–O bond gives rise to less oxygen ligand holes. In-situ XRD demonstrates the constrained contraction of c-axis lattice parameter and mitigated structural distortion. Under a high upper cut-off voltage of 4.6 V, the single-crystal CS-LCO maintains a reversible capacity of 159.8 mAh g−1 with a good retention of ~ 89% after 300 cycles, and reaches a high specific capacity of 163.8 mAh g−1 at 5C. The proposed strategy can be extended to other pairs of low- (Zr4+, Ta5+, and W6+, etc.) and high-diffusivity cations (Zn2+, Ni2+, and Fe3+, etc.) for rational design of advanced layered oxide core–shell structured cathodes for lithium-ion batteries.

Silicon holds great potential as anode material for next-generation advanced lithium-ion batteries (LIBs) due to its exceptional capacity. However, its low conductivity and huge volume changes during charge/discharge process result in a poor electrochemical performance of silicon anode. This study introduces a cost-effective strategy to repurpose KL Si waste from photovoltaic industry into feedstock for LIBs. A Si@C composite with core–shell structure was synthesized from kerf loss (KL) Si waste as the primary capacity contributing ingredient. The nanoscale Si particles (Si NPs) was produced through ball milling and acid pickling of KL Si waste, and then coated a carbon shell by the pyrolyzed phenolic resin. This core–shell structure enhances the electrical conductivity of silicon-based anode, facilitates ion/electron movement, and reduces volume fluctuations of silicon during lithiation/de-lithiation process. Compared to the pure Si anode, the Li + transmission efficiency of the Si@C anode was significantly improved, leading to a better cycle and rate performance. The resulting SP-2 electrode demonstrated a consistent capacity of 602 mAh g −1 after 150 cycles under current density of 0.5 A g −1 . Graphical abstract

By growing one metal organic frameworks (MOFs) on different metal organic frameworks plays an important role in catalytic reaction, but its cooperative catalysis in tandem reaction is an undeveloped field yet, and the reports are very limited. In this work, the material MIL-101(Cr)@MOF-867 with core–shell structure was constructed by growing MOF-867 on the ultra-stable MIL-101(Cr). The synthesized core–shell material had acid–base sites at the same time. Thus, the synergistic catalysis of deacetalization-Knoevenagel tandem reaction showed good catalytic performance and obtained ultra-high yield. In addition, all experiments showed that the core–shell catalyst MIL-101(Cr)@MOF-867 had high stability and under the same conditions, the activity remained still high after five cycles. At the same time, this is the first time to apply MIL-101(Cr)@MOF-867 catalyzing deacetalization-Knoevenagel tandem reaction.A bifunctional material with core–shell structure was successfully synthesized. The obtained MIL-101(Cr)@MOF-867 with both acid and base sites showed ultra-high conversion in the deacetalization-Knoevenagel tandem reaction, thanks to the Lewis acid sites catalytic deacetalization reaction provided by Cr and Zr clusters and the Brönsted base sites to catalyze Knoevenagel reaction provided by pyridine. Fortunately, after five cycles of experiments, all the characterization showed that it still maintained ultra-high catalytic performance and stability. In addition, this is the first time to catalyze the deacetalization-Knoevenagel tandem reaction by MIL-101(Cr)@MOF-867.