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Hybrid nanocomposites with enhanced microwave absorption properties have been designed by growing CuS nanoflakes on magnetically decorated graphene, and the effect of special nanostructures on microwave absorption properties has been investigated. The structure of the nanocomposites was characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), N2 adsorption-desorption, and vibrating sample magnetometer (VSM). The influence of cetyltrimethylammonium bromide (CTAB) on the morphology of CuS nanoflakes was also investigated. A possible formation process of the nanocomposites and the mechanism of microwave absorption were explained in detail. As an absorber, the nanocomposites with a filler loading of 20 wt % exhibited enhanced microwave absorption properties due to the special nanostructures, extra void space, and synergistic effect. The maximum reflection loss can reach -54.5 dB at 11.4 GHz, and the absorption bandwidths exceeding -10 dB are 4.5 GHz with a thickness of 2.5 mm, which can be adjusted by the thickness. The results indicate that the hybrid nanocomposites with enhanced microwave absorption properties and lightweight have a promising future in decreasing electromagnetic wave irradiation.

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A two-step strategy combining in situ polymerization and a hydrothermal process has been developed for coupling polyaniline (PANI) with porous TiO 2 anchored on magnetic graphene. The microstructure and morphology of magnetic graphene@PANI@porous TiO 2 were characterized by FETEM, FESEM, XRD, XPS and VSM in detail. The results indicated that magnetic graphene@PANI was completely covered by porous TiO 2 with random orientations and the saturation magnetization value of the composite was 19.2 emu g À1 . PANI was used to decrease the absorber thickness, while the porous TiO 2 with a large surface area was designed to enhance the interaction between the electromagnetic (EM) wave and the absorber through multiple reflections, thus enhancing EM wave absorption properties. As an EM wave absorber, the maximum reflection loss of the composite was up to À45.4 dB due to the better normalized characteristic impedance (close to 1) at a thickness of only 1.5 mm and the absorption bandwidths exceeding À10 dB were 11.5 GHz when the thickness ranged from 1 to 3.5 mm. The excellent EM wave absorption performance was ascribed to the combined contribution from the enhanced dielectric relaxation processes, the unique porous nanostructures, the quarter-wave length matching model and the well-matched normalized characteristic impedance. Consequently, it is believed that the composite could be used as an excellent EM wave absorption material and the two-step strategy offered an effective way to design a high-performance EM wave absorber with a relatively thin thickness.

Metal–organic framework (MOF)-derived composites on the microwave absorption have received extensive attention. However, which kind of organic ligand corresponding MOF derivative has better electromagnetic wave absorption performance is an urgent problem to be solved. In this work, two kinds of Ni@C derived from the Ni-based MOFs with two kinds of organic ligands (dimethylimidazole as a ligand named as Ni-ZIF and trimesic acid as a ligand named as Ni-BTC) were successfully obtained. The compositions, morphologies, and electromagnetic properties of two composites were well controlled. As a result, both kinds of Ni@C exhibited the good microwave absorption properties. Comparatively speaking, the Ni@C derived from Ni-ZIF performs better. The Ni@C-ZIF microspheres with a 40% mass filling ratio exhibited a strong reflection loss of −86.8 dB at 13.2 GHz when the matching thickness was 2.7 mm, and the corresponding effective absorption bandwidth was 7.4 GHz (4–11.4 GHz) with the thickness ranging from 1.5 to 4.0 mm. The impedance matching, multiple reflection, and interfacial polarization among Ni and C were beneficial to the enhancement of microwave attenuation, which N-doping introduced by nitrogen-containing ligands leads to excellent microwave absorption properties. Therefore, this work can give insights into understanding the absorbing mechanism as well as provide a simple and flexible paradigm for the design and synthesis of the absorber with the tunable and high-efficiency performances.

Construction of an electrical signal-sensitive nanoreactor in response to small molecule remains a challenge in the developing fields of biomimetic device. Solid nanochannels are considered as promising candidates for constructing smart systems, which is highly sensitive to biochemical stimulus. Here, we report an hourglass shaped nanochannel reactor based on cascade enzymatic catalysis and cation-selective nanochannel system. The employed glucose-specific dual-enzyme combination, glucose oxidase (GOx) and horseradish peroxidase (HRP), ensures the glucose catalytic efficiency and selectivity. Presence of glucose immediately induced the bienzymatic sequential reaction. The yielding gluconic acid decreased the microenvironmental pH in the channel gradually. Different concentration of glucose produced different amount of acid and thus altered the negative charge density inside the nanochannel to different extent. Modification convenience and mechanical robustness also ensure the stability of the test platform. Owing to its unique cation-selective property and high sensitivity toward microenvironmental alteration, this nanodevice shows robust glucose-responsive properties through monitoring ionic current signatures.

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