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In this work, we reported the FeS2@C nanocapsules-modified petal-shaped MoS2 nanosheets (MoS2/FeS2@C) peroxidase prepared by arc discharging combined with hydrothermal methods. We thoroughly investigated their peroxidase-like activities in the colorimetric detection of H2O2 and glutathione (GSH). The results indicate that the prepared petal-shaped MoS2/FeS2@C nanocomposites exhibit enhanced peroxidase activity compared to the single-component MoS2 or FeS2@C. The detection ranges and detection limits (LOD) are 1–150 μM and 0.43 μM for H2O2, respectively, while for GSH, they are 0.2–40 μM and 0.14 μM, respectively. The superior peroxidase-like activity of the MoS2/FeS2@C results from the synergy between the MoS2 and FeS2@C. This synergy creates abundant active sites and more substance shuttle channels, which increases the cyclic efficiency among Fe3+/Fe2+ and Mo6+/Mo4+ and improves the yield of hydroxyl radicals. As a result, the MoS2/FeS2@C nanocomposites acquired quick electron transport and improved peroxidase-like catalytic performance. Moreover, the MoS2/FeS2@C nanocomposites exhibit high stability and selectivity, retaining high-activity levels even after 30 days. These make them promising candidates for use in biosensing and catalysis applications. [ABSTRACT FROM AUTHOR]

Herein, we report the core–shell structured Ni@CN/SiCN nanohybrids synthesized by a one-step arc-discharge method. The high-resolution transmission electron microscope study reveals that the as-prepared Ni@CN/SiCN nanohybrids mainly consist of Ni nanoparticles core and composite outer shells, accompanied by a few nano-sized SiC/C grains. The composite outer layer consists of an N-doped graphite C shell or a hybrid shell of N-doped SiC assembled with N-doped C. The Ni@CN/SiCN nanohybrids show outstanding microwave absorption properties, and their optimal reflection loss is achieved in − 57.6 dB at 10.83 GHz with a thickness of 2.24 mm. The absorption bandwidth below − 10 dB is 6 GHz at a single thickness of 1.8 mm. The Ni@CN/SiCN nanohybrids can arouse multiple polarizations, which contribute to a forceful dielectric resonance, resulting in optimized impedance matching and excellent microwave absorption capacity. Therefore, this work provided a feasible way to obtain a high-efficiency microwave absorbent with a multi-polarization effect. [ABSTRACT FROM AUTHOR]

In this study, we adopted a simple strategy of the arc discharge to prepare the B-doped SiC microwave nano-absorbers. Herein, the amorphous boron was selected as a doping B element source to tune the electromagnetic parameters of the SiC nanopowders. The experimental results indicate that the doping B in the SiC can conveniently tailor the microwave absorption capability of the SiC nanopowders. The appropriate doping B in the SiC can contribute to excellent synergistic effects among its defect dipoles, leakage, and magnetism. Among the doped SiC with B doping content of 0, 5, 10, and 15 at.%, the SiC with doping B content of 10 at.% acquired the optimized impedance matching and enhanced microwave absorption properties. And the optimal reflection loss (RL) value − 51.2 dB at 6.76 GHz with a matching thickness of 2.9 mm is acquired. The RL of the B-doped SiC nanopowders with B doping content of 10 at.% exceeding − 10 dB is about 3–5 times those of the other three samples in the ranges of 1–18 GHz at a matching thickness of 1.2–6.0 mm. Therefore, this work provided a feasible way to tune the microwave absorption properties of the B-doped SiC, which is of great significance to improve SiC-based high-temperature dielectric ceramics of microwave absorption performances by the defect-engineering strategy. [ABSTRACT FROM AUTHOR]

A type of core–shell structured N-doped C-coated Ni nanocapsules (Ni@NC) with a size range of 20–70 nm was prepared by a simple strategy of the arc discharge. And the microwave absorption capability of the Ni@NC nanocapsules can be conveniently tuned by N-doping content varying from changing nitrogen pressure in their preparation process. The study revealed that the variable microwave absorption capability of the Ni@NC nanocapsules results from their tuned dielectric behavior. The tuned dielectric responses depend on the degrees of the broken atomic symmetry of the graphite carbon for carbon atoms substituted with nitrogen ones. The optimized impedance matching of the Ni@NC nanocapsules can be achieved by the appropriate content of N doping in graphite C shells. An optimal reflection loss value − 50.7 dB at 14.43 GHz with a thin thickness of 1.8 mm is acquired while choosing the pressure of 15 kPa nitrogen for the preparation of the Ni@NC nanocapsules (the N content in Ni@NC is about 4.62 at.% estimated by XPS). Therefore, it is a feasible strategy to tuning the microwave absorption properties of the Ni@NC nanocapsules by changing the content of N doping, which is of great significance for the study microwave absorbing materials at the atomic scale. [ABSTRACT FROM AUTHOR]

We adopted a facile method consisting of the arc discharge method combined with the in situ self-polymerization process to synthesize the cubic TiN@CN nanocapsules in this work, and we also investigated the electrochemical performance and microwave absorption properties of the TiN@CN nanocapsules in detail. The results show that the TiN@CN nanocapsules exhibit excellent electrochemical performance. The specific capacitance of the TiN@CN nanocapsules is 119 F g−1 at 1 A g−1, and their capacitance retention rate is 92% after 5000 cycles at the current density of 2 A g −1. Besides, the cubic TiN@CN nanocapsules also exhibit powerful microwave absorption capacity. The reflection loss (RL) below − 20 dB is achieved in a wide frequency range of 7.2–15.5 GHz with a thickness range of 1.1–2.3 mm, and the optimal RL value is − 40.6 dB at 10.6 GHz with a relatively thin thickness of 1.6 mm. Therefore, TiN@CN nanocapsules are promising and applicable as electrode materials for supercapacitors and as microwave absorbers. [ABSTRACT FROM AUTHOR]

In this study, we have reported nitrogen-doped graphite C coated Co nanocomposite (Co@CN) catalysts synthesized by one-step arc discharge method. The surface compositions, morphologies and the catalytic properties of the Co@CN nanocomposites were studied minutely. The results reveal that the prepared Co@CN nanocomposites have typical core-shell structure and show highly efficient catalytic performance in a reduction of 4-nitrophenol (4-NP), rhodamine and methylene blue. Their rate constant (Kapp) is 0.074 s−1 in a reduction of 4-NP, which is much higher than that of reported transition metal-based catalysts. Moreover, the overpotential of Co@CN is only 96 mV at a current density of 10 mA cm−2 in alkaline solution, showing high electrocatalytic activities in the hydrogen evolution reaction. The excellent synergistic effect between nitrogen-doped graphite C shell and magnetic Co core enables the Co@CN nanocomposites catalysts to hold abundant active sites and to transmit rapidly electron ability, resulting in Co@CN nanocomposite catalysts having a highly efficient catalytic nature. [ABSTRACT FROM AUTHOR]

In this study, the three types of core–shell structured Fe-based nanocapsules with different shapes were synthesized using arc-discharge method via fine-tuning Al content in Fe–Al raw material alloy. The synthetic parameters on the microstructure and shape as well as microwave absorption properties of Fe-based nanocapsules were investigated in detail. The results show that the Al content in Fe–Al raw material alloy will affect the shape and microwave absorption properties of the synthesized Fe-based nanocapsule absorbent. The polyhedral Fe@FeOx–Al2O3 nanocapsules absorbents can be obtained while Fe–Al raw material alloy containing Al 3 wt% was used as an anode in arc-discharge process, and their microwave absorption properties can be significantly improved, compared with those of the prepared other two Fe-based nanocapsules. Reflection loss (RL) values below − 20 dB for polyhedral Fe@FeOx–Al2O3 nanocapsules absorbent are acquired in the frequency range of 3.21–18 GHz within 1.2–5.5 mm thickness, covering few S-bands and whole C–Ku bands. Besides, the FexAly phase existed in Fe-based nanocapsules cause the frequency band of the strongest RL (exceeding − 20 dB) shifting low-frequency region, which can be of help in further researching microwave absorption (L–S wave band) of FexAly alloy or other Al-magnetic transition metal nanoparticles absorbent in future work. These results demonstrate that the polyhedral Fe nanocapsules hold excellent microwave absorption properties, which could be promising candidate materials for the manufacture of microwave devices with broadband. [ABSTRACT FROM AUTHOR]

In this work, we reported P-doped WO 3-δ coated Ni (Ni@P-WO 3-δ) nanocomposites prepared by the arc discharge method with a subsequent phosphorylation treatment, where the Ni@P-WO 3-δ nanocomposites exhibited a tunable electromagnetic wave absorption (EMA) performances by the doping P into the surface shell WO 3-δ compared with the Ni@WO 3-δ. The experimental evidence combined with the theory calculation results based on First-principles revealed that the doping P into the WO 3-δ endowed improvable electrical conductivity, resulting in higher conduction loss for the Ni@P-WO 3-δ nanocomposites. Meanwhile, P doping causes more defects and distorted lattice for the WO 3-δ shell, which enhances defect-induced polarization loss. As a result, enhanced conduction loss and polarization relaxation loss of the Ni@P-WO 3-δ nanocomposites are dominant for improving EMA performance. Further, the study found that the EMA properties of the Ni@P-WO 3-δ nanocomposites are related to P doping content and can be tailored efficiently by controlling the amount of P dopant source. Thus, the Ni@P-WO 3-δ nanocomposites with appropriate P doping can optimize their balance between impedance matching and dielectric loss, achieving excellent microwave absorption performance. The minimum reflection loss (RL) value of the Ni@P-WO 3-δ nanocomposites was − 55.62 dB, and the efficient absorption bandwidth achieved in 12.58 GHz, with a thickness rang of 1.61–5.00 mm. Therefore, this work confirms that doping engineering has a significant application for the design and synthesis of dielectric-typed microwave absorbers. [Display omitted] [ABSTRACT FROM AUTHOR]

Herein, we synthesized S, N co-doped graphitic carbon-coated Ni/NiS/NiS 2 (Ni/NiS/NiS 2 @C(S, N)) nanocomposites via the arc-discharge method combined with the sulfidation process. The as-prepared Ni/NiS/NiS 2 @C(S, N) nanocomposites with unique core-shell structures and multiple interfaces exhibit highly efficient electrocatalytic capacity. They only needed the overpotential of 60 mV to afford the current density of −10 mA cm−2 towards hydrogen evolution reaction (HER). Meanwhile, they required a low potential of 1.381 V at 10 mA cm−2 towards urea oxidation reaction (UOR). Even during urea electrolysis, they only needed the cell voltage of 1.45 V at 10 mA cm−2 and exhibited strong stability in the long-time test. Further, the catalytic mechanism of Ni/NiS/NiS 2 @C(S, N) nanocomposites was discussed in detail. The superior electrocatalytic capacity of Ni/NiS/NiS 2 @C(S, N) nanocomposites towards HER, UOR, and urea electrolysis results from the synergistic effect among multiple interfaces. Such synergistic effect triggers rapid electron transfer, fast rate cleavage of H 2 O and urea, and improved hydrogen adsorption free energy. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, we have successfully synthesized the core-shell Fe/FeS 2 @C nanoparticles using the arc-discharge method combined with heat treatment technology. The study shows that as-prepared core-shell Fe/FeS 2 @C nanoparticles exhibit excellent peroxidase-like activity. As for TMB and H 2 O 2 , the Michaelis–Menten constant value (K m : 0.1021 mM, 0.037 mM) of the core-shell Fe/FeS 2 @C nanoparticles are much lower than that of natural horseradish peroxidase (HRP)(K m : 3.7 mM), respectively. And the core-shell Fe/FeS 2 @C nanoparticles hold the two response ranges of the sensor to H 2 O 2 are 2–200 μM and 200–1000 μM, respectively. The corresponding detection limits (LOD) are 0.42 μM (3σ/slope). Moreover, it is no evident influence on the result while adding Cu2+, K+, Na+, NH 4 +, Ni2+, Zn2+, Ca2+, Mg2+, NO 3 -, Glucose, and some biomolecules into the reaction systems. The excellent peroxidase-like activity for the colorimetric detection of H 2 O 2 results from the synergistic effect between the Fe/FeS 2 core and the graphite C shell, which increases the active sites of the core-shell Fe/FeS 2 @C nanoparticles sites as well as the electronic state densities of graphite C near its Fermi level, resulting in accelerating the cyclic effect between the Fe3+ and Fe2+. As a result, the Fe/FeS 2 @C core-shell nanoparticles acquire an excellent peroxidase-like catalytic performance. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • N-doped graphite coated Ni (Ni@CN) nanocapsules were prepared by one-step method. • The Ni@CN have efficient dual-functional behavior in HER and microwave absorption. • The Ni@CN shows a low overpotential of 85 mV at 10 mA cm−2 in HER. • Complementarity between CN shell and Ni core induce superior properties. • Doping N into graphite boosts the electronic transmission ability of graphite C. Developing high efficient, stable, and earth-abundant materials is still a great challenge both in the electrocatalytic and microwave absorption fields nowadays. Herein, we construct unique core-shell structured N-doped graphite coated Ni (Ni@CN) nanocapsules through a facile one-step arc-discharge method. The as-obtained Ni@CN show superior hydrogen evolution reaction (HER) activities with a low overpotential of 85 mV at 10 mA cm−2, a small Tafel slope of 69 mV dec-1, and strong long-term stability of 10 h. Besides, the Ni@CN nanocapsules exhibit high microwave absorption performance as microwave absorbers. Their optimal value of reflection loss (RL) is -35.8 dB at 11.7 GHz with a thickness of 2.3 mm. The dual-functional behavior of Ni@CN nanocapsules in catalytic and microwave absorption is due to their strong synergistic effect between the N-doped graphite shell and Ni core, the high electrical conductivity of Ni, and the abundant defects caused by the N doping into the graphite shell. [ABSTRACT FROM AUTHOR]