State of the art and prospects of Fe3O4/carbon microwave absorbing composites from the dimension and structure perspective.

At present, to solve the threat of electromagnetic wave (EMW) radiation pollution to human health, intelligent control and information security, tremendous efforts have been made to manufacture EMW absorbing materials. For ideal microwave absorption materials (MAMs), it is generally necessary not only to pursue strong microwave absorption (MA) over wide effective absorption bandwidth (EAB), but also to take into account the requirements of light weight, thin matching thickness and chemical stability characteristics. It has been found that magnetite (Fe3O4) is the most promising MAM to absorb and dissipate EMW among various absorbers, because of its good mechanical and chemical stability, controllable morphology, high Curie temperature, easy preparation, economy and excellent magnetic properties. However, the application performance of Fe3O4 absorber with single composition is limited by its easy agglomeration, eddy current, high density, and impedance mismatch. In addition, achieving efficient MA metrics with low absorber loading remains a huge challenge. To overcome these limitations, conjugation with dielectric carbon-based materials and special structural designs have been extensively explored as viable solutions to optimize the microwave absorption performance (MAP) of Fe3O4. This paper reviews the recent research progress of Fe3O4/carbon MAMs, and then the influence of dimensions and structures regulations on the MAPs are introduced in detail. Finally, the current existing problems and future development direction of Fe3O4/carbon composites in the field of MA are also presented.

[Association of CYP2C19 and CYP3A5 gene polymorphisms with myocardial infarction].

OBJECTIVE: To assess the association of CYP2C19 and CYP3A5 gene polymorphisms with the risk of myocardial infarction. METHODS: Five hundred patients with myocardial infarction and 500 healthy controls were randomly selected. Fluorescent PCR and Sanger sequencing were used to detect the CYP2C19 and CYP3A5 gene polymorphisms. Logistic regression was used to analyze the correlation between the polymorphisms and myocardial infarction. Quanto software was used to evaluate the statistical power. RESULTS: The two groups had significant difference in the frequency of AG, GG genotypes and A allele of the CYP2C19 gene rs4986893 locus and the AA, AG, GG genotypes and G allele of the CYP3A5 gene rs776746 locus ( P<0.05), but not in the frequency of genotypes and alleles of CYP2C19 gene rs4244285 and rs12248560 loci, and the AA genotype of the rs4986893 locus. After correction for age, gender, and body mass index, Logistic regression indicated that the AG genotype and A allele of the CYP2C19 gene rs4986893 locus, and the GG genotype and G allele of CYP3A5 gene rs776746 locus are associated with susceptibility of myocardial infarction, while rs4986893 GG genotype and AA and AG genotypes of rs776746 may confer a protective effect. Based on the sample size and allele frequency, analysis with Quanto software suggested that the result of this study has a statistical power of 99%. CONCLUSION: CYP2C19 and CYP3A5 gene polymorphisms may increase the risk for myocardial infarction.

Noncovalent π-stacked robust topological organic framework.

Organic frameworks (OFs) offer a novel strategy for assembling organic semiconductors into robust networks that facilitate transport, especially the covalent organic frameworks (COFs). However, poor electrical conductivity through covalent bonds and insolubility of COFs limit their practical applications in organic electronics. It is known that the two-dimensional intralayer π∙∙∙π transfer dominates transport in organic semiconductors. However, because of extremely labile inherent features of noncovalent π∙∙∙π interaction, direct construction of robust frameworks via noncovalent π∙∙∙π interaction is a difficult task. Toward this goal, we report a robust noncovalent π∙∙∙π interaction-stacked organic framework, namely πOF, consisting of a permanent three-dimensional porous structure that is held together by pure intralayer noncovalent π∙∙∙π interactions. The elaborate porous structure, with a 1.69-nm supramaximal micropore, is composed of fully conjugated rigid aromatic tetragonal-disphenoid-shaped molecules with four identical platforms. πOF shows excellent thermostability and high recyclability and exhibits self-healing properties by which the parent porosity is recovered upon solvent annealing at room temperature. Taking advantage of the long-range π∙∙∙π interaction, we demonstrate remarkable transport properties of πOF in an organic-field-effect transistor, and the mobility displays relative superiority over the traditional COFs. These promising results position πOF in a direction toward porous and yet conductive materials for high-performance organic electronics.

Highly Monodisperse Cu-Sn Alloy Nanoplates for Efficient Nitrophenol Reduction Reaction via Promotion Effect of Tin.

The hexagonal copper-tin alloy (Cu-Sn) nanoplates were synthesized using a high temperature solvent method, the length of six equilateral edges of hexagonal Cu-Sn nanoplates was 23 nm, and the thickness was 13 nm. The obtained hexagonal Cu-Sn nanoplates were highly monodisperse and allowed the formation of nanoarrays arranged with long-range order. The hexagonal Cu-Sn nanoplates exhibited high catalytic activity on catalytic hydrogenation of 4-nitrophenol to 4-aminophenol. Due to the promotion effect of Sn, the apparent rate constant (ka) of hexagonal Cu-Sn nanoplates was three times that of Cu nanoparticles. The density functional theory (DFT) calculations and experimental results demonstrated that Sn could promote the coordination process of -NO2 of 4-nitrophenol with Cu-Sn nanoplates and contribute to activation of 4-nitrophenol. In addition, the hexagonal Cu-Sn nanoplates showed high stability and reusability for the reduction reaction, good adaptability in different pH and the ionic strength, and wide applicability for the degradation of methylene blue, methyl orange, and rhodamine B, even in the industrial wastewater, suggesting that the Cu-Sn nanoplates are promising catalysts in organic industry wastewater treatment.

Core-Shell ZnO@SnO2 Nanoparticles for Efficient Inorganic Perovskite Solar Cells.

The ideal charge transport materials should exhibit a proper energy level, high carrier mobility, sufficient conductivity, and excellent charge extraction ability. Here, a novel electron transport material was designed and synthesized by using a simple and facile solvothermal method, which is composed of the core-shell ZnO@SnO2 nanoparticles. Thanks to the good match between the energy level of the SnO2 shell and the high electron mobility of the core ZnO nanoparticles, the PCE of inorganic perovskite solar cells has reached 14.35% (JSC: 16.45 mA cm-2, VOC: 1.11 V, FF: 79%), acting core-shell ZnO@SnO2 nanoparticles as the electron transfer layer. The core-shell ZnO@SnO2 nanoparticles size is 8.1 nm with the SnO2 shell thickness of 3.4 nm, and the electron mobility is seven times more than SnO2 nanoparticles. Meanwhile, the uniform core-shell ZnO@SnO2 nanoparticles is extremely favorable to the growth of inorganic perovskite films. These preliminary results strongly suggest the great potential of this novel electron transfer material in high-efficiency perovskite solar cells.

MOF-Confined Sub-2 nm Stable CsPbX3 Perovskite Quantum Dots.

The metal halide with a perovskite structure has attracted significant attention due to its defect-tolerant photophysics and optoelectronic features. In particular, the all-inorganic metal halide perovskite quantum dots have potential for development in future applications. Sub-2 nm CsPbX3 (X = Cl, Br, and I) perovskite quantum dots were successfully fabricated by a MOF-confined strategy with a facile and simple route. The highly uniform microporous structure of MOF effectively restricted the CsPbX3 quantum dots aggregation in a synthetic process and endowed the obtained sub-2 nm CsPbX3 quantum dots with well-dispersed and excellent stability in ambient air without a capping agent. The photoluminescence emission spectra and lifetimes were not decayed after 60 days. The CsPbX3 quantum dots maintained size distribution stability in the air without any treatment. Because of the quantum confinement effect of CsPbX3 quantum dots, the absorption and photoluminescence (PL) emission peak were blue shifted to shorter wavelengths compare with bulk materials. Furthermore, this synthetic strategy provides a novel method in fabricating ultra-small photoluminescence quantum dots.

MXene Boosted CoNi-ZIF-67 as Highly Efficient Electrocatalysts for Oxygen Evolution.

Oxygen evolution reaction (OER) is a pivotal step for many sustainable energy technologies, and exploring inexpensive and highly efficient electrocatalysts is one of the most crucial but challenging issues to overcome the sluggish kinetics and high overpotentials during OER. Among the numerous electrocatalysts, metal-organic frameworks (MOFs) have emerged as promising due to their high specific surface area, tunable porosity, and diversity of metal centers and functional groups. It is believed that combining MOFs with conductive nanostructures could significantly improve their catalytic activities. In this study, an MXene supported CoNi-ZIF-67 hybrid (CoNi-ZIF-67@Ti3C2Tx) was synthesized through the in-situ growth of bimetallic CoNi-ZIF-67 rhombic dodecahedrons on the Ti3C2Tx matrix via a coprecipitation reaction. It is revealed that the inclusion of the MXene matrix not only produces smaller CoNi-ZIF-67 particles, but also increases the average oxidation of Co/Ni elements, endowing the CoNi-ZIF-67@Ti3C2Tx as an excellent OER electrocatalyst. The effective synergy of the electrochemically active CoNi-ZIF-67 phase and highly conductive MXene support prompts the hybrid to process a superior OER catalytic activity with a low onset potential (275 mV vs. a reversible hydrogen electrode, RHE) and Tafel slope (65.1 mV∙dec-1), much better than the IrO2 catalysts and the pure CoNi-ZIF-67. This work may pave a new way for developing efficient non-precious metal catalyst materials.

Hierarchical Structure with Highly Ordered Macroporous-Mesoporous Metal-Organic Frameworks as Dual Function for CO2 Fixation.

As a major greenhouse gas, the continuous increase of carbon dioxide (CO2) in the atmosphere has caused serious environmental problems, although CO2 is also an abundant, inexpensive, and nontoxic carbon source. Here, we use metal-organic framework (MOF) with highly ordered hierarchical structure as adsorbent and catalyst for chemical fixation of CO2 at atmospheric pressure, and the CO2 can be converted to the formate in excellent yields. Meanwhile, we have successfully integrated highly ordered macroporous and mesoporous structures into MOFs, and the macro-, meso-, and microporous structures have all been presented in one framework. Based on the unique hierarchical pores, high surface area (592 m2/g), and high CO2 adsorption capacity (49.51 cm3/g), the ordered macroporous-mesoporous MOFs possess high activity for chemical fixation of CO2 (yield of 77%). These results provide a promising route of chemical CO2 fixation through MOF materials.

CMTN-SP: A Novel Coverage-Control Algorithm for Moving-Target Nodes Based on Sensing Probability Model in Sensor Networks.

The non-consecutive coverage problem for the target nodes in Sensor Networks could lead to the coverage blind area and a large amount of redundant data, which causes the bottleneck phenomenon for the communication link. A novel Coverage Control Algorithm for Moving Target Nodes Based on Sensing Probability Model (CMTN-SP) is proposed in this work. Firstly, according to the probability theory, we derive the calculation method for the expectation of the coverage quality with multiple joint nodes, which aims to reduce the coverage blind area and improving network coverage rate. Secondly, we employ the dynamic transferring mechanism of the nodes to re-optimize the deployment of the nodes, which alleviates the rapid exhaustion of the proper network energy. Finally, it is verified via the results of the simulation that the network coverage quality could not only be improved by the proposed algorithm, but the proposed algorithm could also effectively curb the rapid exhaustion of the node energy.

Copper Nanoflower Assembled by Sub-2 nm Rough Nanowires for Efficient Oxygen Reduction Reaction: High Stability and Poison Resistance and Density Functional Calculations.

The copper nanoflowers, assembled by sub-2 nm rough nanowires with high catalytic active (200) facets, are prepared by a prompt and simple method with cetyltrimethylammonium bromide (CTAB) as a capping agent. The CTAB plays a vital role in the synthesis process, whereas the copper nanorod arrays assembled by copper nanoparticles are obtained without CTAB. The copper nanoflowers are used as catalysts in oxygen reduction reactions and exhibit excellent electrocatalytic activity, which shows nearly the same activity compared with the commercial Pt/C catalyst, attributing to the nanoflower-exposed higher catalytic active (200) facets. Furthermore, the nanoflowers can avoid methanol-poison effect and show better long-term operation stability. The density functional theory was used to calculate the atom energy of Cu(100) facets and Cu(111) facets. Both of O2 dissociation and H2O activation on the facets are very easy. However, the difference between Cu(100) facets and Cu(111) facets is the adsorption and dissociation energy of O2, and the adsorption and activation of oxygen molecule is much easier on Cu(100) facets than on Cu(111) facets because of the more open nature of (100) facets.

Diffusion-weighted MRI findings in Sjögren's syndrome: a preliminary study.

BACKGROUND: Parotid glands diffusion-weighted imaging (DWI) in Sjögren's syndrome patients have provided conflicting results currently. PURPOSE: To determine if parotid gland DWI using a small region of interest (ROI) can provide diagnosis and assess therapeutic efficacy in Sjögren's syndrome. MATERIAL AND METHODS: Twenty-three women with Sjögren's syndrome, five with dry mouth who did not meet diagnostic criteria for Sjögren's syndrome, and 11 healthy volunteers (controls) were evaluated with DWI. All participants received routine T1-weighted (T1W) imaging and T2-weighted (T2W) fat-suppressed imaging, and DWI. The SI ratios (SIRs) and ADC ratios (ADCRs) for parotid gland/spinal cord were then calculated. Approximately 8-10 round ROIs measuring approximately 5 mm(2) were placed on each lobe of the parotid gland, and the signal intensity (SI) was measured while avoiding fat, ducts, and blood vessels. A ROI encompassing the entire lobe of the parotid gland was also used to measure SI. RESULTS: Using 5 mm(2) ROIs significantly higher DWI SIRs were noted in participants with Sjögren's syndrome compared with either participants with dry mouth without Sjögren's syndrome or healthy volunteers (all, P <0.001). The difference was not related to the presence of fat. No differences were noted when the larger ROI was used. In addition, parotid gland from untreated Sjögren's participants showed significantly higher SIRs compared with those from treated participants (P = 0.015). CONCLUSION: A small ROI DWI can provide morphological and functional information on the parotid gland in Sjögren's syndrome patients, and can aid in the diagnosis and evaluation of therapeutic efficacy.