•This paper reviewed the recent research progress on MOF nanosheets.•Almost all MOF nanosheets prepared in last decade under different synthetic strategies were summarized.•Key application of MOF ...nanosheets are listed.•The challenges and outlooks on MOF nanosheets are specifically outlined.
Metal-organic framework (MOF) nanosheets have attracted extensive attention due to their remarkable properties, such as nanoscale and tunable thickness, adjustable structure and function, high-aspect-ratio, large surface area, more exposed accessible active site, favorable mechanical flexibility, and optical transparency. This article aims to review the latest developments in MOF nanosheets. Firstly, the assortments of the synthetic methods of MOF nanosheets will be introduced. Then, the wide applications and utilization of these ultrathin MOF nanosheets in the fields of electronics, gas separation, catalysis, sensors, energy storage/transfer, and as enzyme inhibitors will also be explored. Finally, the prospects and challenges of MOF nanosheets will be presented.
A novel SARS-related coronavirus (SARS-CoV-2) has recently emerged as a serious pathogen that causes high morbidity and substantial mortality. However, the mechanisms by which SARS-CoV-2 evades host ...immunity remain poorly understood. Here, we identified SARS-CoV-2 membrane glycoprotein M as a negative regulator of the innate immune response. We found that the M protein interacted with the central adaptor protein MAVS in the innate immune response pathways. This interaction impaired MAVS aggregation and its recruitment of downstream TRAF3, TBK1, and IRF3, leading to attenuation of the innate antiviral response. Our findings reveal a mechanism by which SARS-CoV-2 evades the innate immune response and suggest that the M protein of SARS-CoV-2 is a potential target for the development of SARS-CoV-2 interventions.
High-entropy ceramics (HECs) are solid solutions of inorganic compounds with one or more Wyckoff sites shared by equal or near-equal atomic ratios of multi-principal elements. Although in the infant ...stage, the emerging of this new family of materials has brought new opportunities for material design and property tailoring. Distinct from metals, the diversity in crystal structure and electronic structure of ceramics provides huge space for properties tuning through band structure engineering and phonon engineering. Aside from strengthening, hardening, and low thermal conductivity that have already been found in high-entropy alloys, new properties like colossal dielectric constant, super ionic conductivity, severe anisotropic thermal expansion coefficient, strong electromagnetic wave absorption, etc., have been discovered in HECs. As a response to the rapid development in this nascent field, this article gives a comprehensive review on the structure features, theoretical methods for stability and property prediction, processing routes, novel properties, and prospective applications of HECs. The challenges on processing, characterization, and property predictions are also emphasized. Finally, future directions for new material exploration, novel processing, fundamental understanding, in-depth characterization, and database assessments are given.
Integrating desirable light absorption, energy levels, and morphology in one matrix is always the aspiration to construct high‐performance organic solar cells (OSCs). Herein, an asymmetric acceptor ...Y6‐1O is incorporated into the binary blends of acceptor Y7‐BO and donor PM6 to prepare ternary OSCs. Two isogenous asymmetric–symmetric acceptors with similar chemical skeletons tend to form alloy‐like state in blends due to their good compatibility, which contributes to optimizing the morphology for efficient charge generation and extraction. The complementary absorption of two acceptors helps to improve the photon harvesting of ternary blends, and the higher lowest unoccupied molecular orbital (LUMO) energy level of Y6‐1O offers the chance to uplift the mixed LUMO energy levels of acceptors. Combining the aforesaid benefits, the ternary OSCs with 10 wt% Y6‐1O produce a top‐ranked power conversion efficiency (PCE) of 18.11% with simultaneously elevated short‐circuit current density, open‐circuit voltage, and fill factor in comparison to Y7‐BO‐based binary devices. Furthermore, the optimized ternary OSCs with ≈300 nm active layers obtain a champion PCE of 16.61%, which is the highest value for thick‐film devices reported so far. This work puts forward an avenue for further boosting the performance of OSCs with two isogenous acceptors but different asymmetric structures.
The synergistically optimized light absorption, energy levels, and morphology, by incorporating an asymmetric isogenous acceptor Y6‐1O in PM6:Y7‐BO‐based ternary organic solar cells (OSCs), is demonstrated. The optimized ternary OSCs produce a top‐ranked power conversion efficiency (PCE) of 18.11% and with ≈300 nm active layers obtain a champion PCE of 16.61%, which is the highest value for thick‐film devices reported so far.
High entropy materials (HEMs, e.g. high entropy alloys, high entropy ceramics) have gained increasing interests due to the possibility that they can provide challenge properties unattainable by ...traditional materials. Though a large number of HEMs have emerged, there is still in lack of theoretical predictions and simulations on HEMs, which is probably caused by the chemical complexity of HEMs. In this work, we demonstrate that the machine learning potentials developed in recent years can overcome the complexity of HEMs, and serve as powerful theoretical tools to simulate HEMs. A deep learning potential (DLP) for high entropy (Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)C is fitted with the prediction error in energy and force being 9.4 meV/atom and 217 meV/Å, respectively. The reliability and generality of the DLP are affirmed, since it can accurately predict lattice parameters and elastic constants of mono-phase carbides TMC (TM = Ti, Zr, Hf, Nb and Ta). Lattice constants (increase from 4.5707 Å to 4.6727 Å), thermal expansion coefficients (increase from 7.85×10-6 K-1 to 10.58×10-6 K-1), phonon thermal conductivities (decrease from 2.02 W·m-1·K-1 to 0.95 W·m-1·K-1), and elastic properties of high entropy (Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)C in temperature ranging from 0 °C to 2400 °C are predicted by molecular dynamics simulations. The predicted room temperature properties agree well with experimental measurements, indicating the high accuracy of the DLP. With introducing of machine learning potentials, many problems that are intractable by traditional methods can be handled now. It is hopeful that deep insight into HEMs can be obtained in the future by such powerful methods.
TiB2 exhibits a unique combination of excellent properties that make it promising candidate for applications in extreme environments, where retention of strength at high temperatures is essential. ...Tailoring grain boundary properties by segregation is believed a prominent way to design high‐temperature performance of ceramics. In this work, segregation tendencies of solute elements, including Sc, Y, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, in TiB2 grain boundaries and the strengthening/weakening effects induced by segregations are investigated by first‐principles calculations. The results reveal that small atoms tend to segregate to grain boundary sites with local compression strains, while large atoms prefer grain boundary sites with local expansion strains. Deteriorated grain boundary strength is usually caused by additional expansion strain induced by segregation, while improved grain boundary strength results from either enhanced local bonding induced by segregation of small atoms or increased fracture strain due to segregation of large atoms. Cr and V, especially Cr, exhibit strong segregation tendency and improvement on grain boundary strength, which provides useful guidelines for the design of high performance TiB2‐based materials.
Ferrites are the most widely used microwave absorbing materials to deal with the threat of electromagnetic (EM) pollution. However, the lack of sufficient dielectric loss capacity is the main ...challenge that limits their applications. To cope with this challenge, three high-entropy (HE) spinel-type ferrite ceramics including (Mg
0.2
Mn
0.2
Fe
0.2
Co
0.2
Ni
0.2
)Fe
2
O
4
, (Mg
0.2
Fe
0.2
Co
0.2
Ni
0.2
Cu
0.2
)Fe
2
O
4
, and (Mg
0.2
Fe
0.2
Co
0.2
Ni
0.2
Zn
0.2
)Fe
2
O
4
were designed and successfully prepared through solid state synthesis. The results show that all three HE MFe
2
O
4
samples exhibit synergetic dielectric loss and magnetic loss. The good magnetic loss ability is due to the presence of magnetic components; while the enhanced dielectric properties are attributed to nano-domain, hopping mechanism of resonance effect and HE effect. Among three HE spinels, (Mg
0.2
Mn
0.2
Fe
0.2
Co
0.2
Ni
0.2
)Fe
2
O
4
shows the best EM wave absorption performance, e.g., its minimum reflection loss (RL
min
) reaches −35.10 dB at 6.78 GHz with a thickness of 3.5 mm, and the optimized effective absorption bandwidth (EAB) is 7.48 GHz from 8.48 to 15.96 GHz at the thickness of 2.4 mm. Due to the easy preparation and strong EM dissipation ability, HE MFe
2
O
4
are promising as a new type of EM absorption materials.
Considering the emergence of severe electromagnetic interference problems, it is vital to develop electromagnetic (EM) wave absorbing materials with high dielectric, magnetic loss and optimized ...impedance matching. However, realizing the synergistic dielectric and magnetic losses in a single phase material is still a challenge. Herein, high entropy (HE) rare earth hexaborides (REB
6
) powders with coupling of dielectric and magnetic losses were designed and successfully synthesized through a facial one-step boron carbide reduction method, and the effects of high entropy borates intermedia phases on the EM wave absorption properties were investigated. Five HE REB
6
ceramics including (Ce
0.2
Y
0.2
Sm
0.2
Er
0.2
Yb
0.2
)B
6
, (Ce
0.2
Eu
0.2
Sm
0.2
Er
0.2
Yb
0.2
)B
6
, (Ce
0.2
Y
0.2
Eu
0.2
Er
0.2
Yb
0.2
)B
6
, (Ce
0.2
Y
0.2
Sm
0.2
Eu
0.2
Yb
0.2
)B
6
, and (Nd
0.2
Y
0.2
Sm
0.2
Eu
0.2
Yb
0.2
)B
6
possess CsCl-type cubic crystal structure, and their theoretical densities range from 4.84 to 5.25 g/cm
3
. (Ce
0.2
Y
0.2
Sm
0.2
Er
0.2
Yb
0.2
)B
6
powders with the average particle size of 1.86 µm were found to possess the best EM wave absorption properties among these hexaborides. The
RL
min
value of (Ce
0.2
Y
0.2
Sm
0.2
Er
0.2
Yb
0.2
)B
6
reaches −33.4 dB at 11.5 GHz at thickness of 2 mm; meanwhile, the optimized effective absorption bandwidth (
E
AB
) is 3.9 GHz from 13.6 to 17.5 GHz with a thickness of 1.5 mm. The introduction of HE REBO
3
(RE = Ce, Y, Sm, Eu, Er, Yb) as intermediate phase will give rise to the mismatching impedance, which will further lead to the reduction of reflection loss. Intriguingly, the HEREB
6
/HEREBO
3
still possess wide effective absorption bandwidth of 4.1 GHz with the relative low thickness of 1.7 mm. Considering the better stability, low density, and good EM wave absorption properties, HE REB
6
ceramics are promising as a new type of EM wave absorbing materials.
The electromagnetic (EM) wave absorbing properties of Cr2AlB2 powders and those after high‐temperature oxidation were investigated. Coupling of magnetic and dielectric loss enables Cr2AlB2 with good ...absorption properties. The minimum reflection loss (RL) value is −44.9 dB at 8.5 GHz with a thickness of 2.7 mm, and the optimized effective absorption bandwidth (EAB) is 4.4 GHz (13.0‐17.4 GHz) with a thickness of 1.6 mm. After oxidation at 750, 900, and 1000°C for 2 h, the minimum RL values, respectively, are −23.9 dB (17.5 GHz, 1.5 mm), −41.4 dB (16.5 GHz, 1.5 mm), and −39.5 dB (8.0 GHz, 3.0 mm); and the corresponding EAB values, respectively, are 3.8 GHz (13.6‐17.4 GHz, 1.7 mm), 4.1 GHz (13.5‐17.6 GHz, 1.6 mm), and 4.4 GHz (13.0‐17.4 GHz, 1.7 mm). With an absorber thickness of 1.5‐4.0 mm, the EAB with a RL value of less than −10 dB can be tuned in a broad‐frequency range 5.0‐18.0 GHz, which basically covers C (4‐8 GHz), X (8‐12 GHz), and Ku (12‐18 GHz) bands. These results demonstrate that Cr2AlB2, as a high‐efficient and oxidation‐resistant absorber, is a promising candidate for microwave absorption applications and can retain good EM wave absorbing properties after high‐temperature oxidation.
Microwave absorption properties of Cr2AlB2 powders (A, B) and the Cr2AlB2 powders oxidized at 900°C (C, D).
Y
2
O
3
is regarded as one of the potential environmental barrier coating (EBC) materials for Al
2
O
3f
/Al
2
O
3
ceramic matrix composites owing to its high melting point and close thermal expansion ...coefficient to Al
2
O
3
. However, the relatively high thermal conductivity and unsatisfactory calcium-magnesium-aluminosilicate (CMAS) resistance are the main obstacles for the practical application of Y
2
O
3
. In order to reduce the thermal conductivity and increase the CMAS resistance, four cubic bixbyite structured high-entropy oxides RE
2
O
3
, including (Eu
0.2
Er
0.2
Lu
0.2
Y
0.2
Yb
0.2
)
2
O
3
, (Sm
0.2
Er
0.2
Lu
0.2
Y
0.2
Yb
0.2
)
2
O
3
, (Sm
0.2
Eu
0.2
Er
0.2
Y
0.2
Yb
0.2
)
2
O
3
, and (Sm
0.2
Eu
0.2
Lu
0.2
Y
0.2
Yb
0.2
)
2
O
3
were designed and synthesized, among which (Eu
0.2
Er
0.2
Lu
0.2
Y
0.2
Yb
0.2
)
2
O
3
and (Sm
0.2
Er
0.2
Lu
0.2
Y
0.2
Yb
0.2
)
2
O
3
bulks were prepared by spark plasma sintering (SPS) to investigate their mechanical and thermal properties as well as CMAS resistance. The mechanical properties of (Eu
0.2
Er
0.2
Lu
0.2
Y
0.2
Yb
0.2
)
2
O
3
and (Sm
0.2
Er
0.2
Lu
0.2
Y
0.2
Yb
0.2
)
2
O
3
are close to those of Y
2
O
3
but become more brittle than Y
2
O
3
. The thermal conductivities of (Eu
0.2
Er
0.2
Lu
0.2
Y
0.2
Yb
0.2
)
2
O
3
and (Sm
0.2
Er
0.2
Lu
0.2
Y
0.2
Yb
0.2
)
2
O
3
(5.1 and 4.6 W·m
−1
·K
−1
) are only 23.8% and 21.5% respectively of that of Y
2
O
3
(21.4 W·m
−1
·K
−1
), while their thermal expansion coefficients are close to those of Y
2
O
3
and Al
2
O
3
. Most importantly, HE RE
2
O
3
ceramics exhibit good CMAS resistance. After being attacked by CMAS at 1350 °C for 4 h, the HE RE
2
O
3
ceramics maintain their original morphologies without forming pores or cracks, making them promising as EBC materials for Al
2
O
3f
/Al
2
O
3
composites.
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