A novel MOF derivation method is used to prepare Fe/C nanocubes, which are constructed by a cubic framework of amorphous carbon decorated uniformly by Fe@graphitic carbon nanoparticles for microwave absorption.
Metal halide perovskites and derivatives exhibit a high sensitivity and low detection limit as direct X‐ray detectors. Inorganic 2D bismuth halide perovskites are promising for X‐ray detections, but have not been reported. Moreover, the quantitative relationship between the structural dimensionality of A3B2X9 perovskites and their compositions has never been investigated, and the underlying mechanism is unclear. Here, the key structural descriptors for 2D A3B2X9 perovskite derivatives are reported: i) octahedral factor μ, 0.377 < μ < 0895; ii) tolerance factor t, 0.8 < t < 1.06; iii) (rA‐0.55)/t < 1.48 Å. Accordingly, a new 2D A3B2X9 perovskite derivative, Rb3Bi2I9, with high X‐ray attenuation coefficients is found. The assembled X‐ray detector exhibits a high μτ product of 2.51 × 10−3 cm2 V−1, good sensitivity for 159.7 μC Gyair−1 cm−2, and a record low detection limit of 8.32 nGyair s−1 among all direct and indirect perovskite X‐ray detectors. The device also exhibits good stability toward external bias and continuous gamma ray radiations (480 000 Gy). This work provides crystal structural insights to rationally design 2D perovskites for new types of radiation detectors.
Highly uniform core-shell composites, polypyrrole@polyaniline (PPy@PANI), have been successfully constructed by directing the polymerization of aniline on the surface of PPy microspheres. The thickness of PANI shells, from 30 to 120 nm, can be well controlled by modulating the weight ratio of aniline and PPy microspheres. PPy microspheres with abundant carbonyl groups have very strong affinity to the conjugated chains of PANI, which is responsible for the spontaneous formation of uniform core-shell microstructures. However, the strong affinity between PPy microspheres and PANI shells does not promote the diffusion or reassembly of two kinds of conjugated chains. Coating PPy microspheres with PANI shells increases the complex permittivity and creates the mechanism of interfacial polarization, where the latter plays an important role in increasing the dielectric loss of PPy@PANI composites. With a proper thickness of PANI shells, the moderate dielectric loss will produce well matched characteristic impedance, so that the microwave absorption properties of these composites can be greatly enhanced. Although PPy@PANI composites herein consume the incident electromagnetic wave by absolute dielectric loss, their performances are still superior or comparable to most PANI-based composites ever reported, indicating that they can be taken as a new kind of promising lightweight microwave absorbers. More importantly, microwave absorption of PPy@PANI composites can be simply modulated not only by the thickness of the absorbers, but also the shell thickness to satisfy the applications in different frequency bands.
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