Materials that can produce large controllable strains are widely used in shape memory devices, actuators and sensors
, and great efforts have been made to improve the strain output
. Among them, ...ferroelastic transitions underpin giant reversible strains in electrically driven ferroelectrics or piezoelectrics and thermally or magnetically driven shape memory alloys
. However, large-strain ferroelastic switching in conventional ferroelectrics is very challenging, while magnetic and thermal controls are not desirable for practical applications. Here we demonstrate a large shear strain of up to 21.5% in a hybrid ferroelectric, C
H
N(CH
)
CdCl
, which is two orders of magnitude greater than that in conventional ferroelectric polymers and oxides. It is achieved by inorganic bond switching and facilitated by structural confinement of the large organic moieties, which prevents undesired 180° polarization switching. Furthermore, Br substitution can soften the bonds, allowing a sizable shear piezoelectric coefficient (d
≈ 4,830 pm V
) at the Br-rich end of the solid solution, C
H
N(CH
)
CdBr
Cl
. The electromechanical properties of these compounds suggest their potential in lightweight and high-energy-density devices, and the strategy described here could inspire the development of next-generation piezoelectrics and electroactive materials based on hybrid ferroelectrics.
Ferroelectricity features the electrical switching of off-centered ions between the potential double well of the non-centrosymmetric lattice, while ionic conduction requires long-range hopping of ...ions across the lattice periodic potentials. The two seemingly mutually exclusive phenomena become strongly intertwined at the nanoscale in electrochemically active materials. However, the intrinsic coupling between ferroelectric switching and ionic activities in bulk crystalline materials remains largely unexplored. Here, we report anomalous polarization switching characteristics of a van der Waals (vdW) layered ferroelectric ionic conductor, CuInP
2
S
6
. By synergistic polarization switching and dielectric spectroscopy studies in both temperature and frequency domains, we reveal that the polarization switching kinetics of this compound is ionic-conduction-limited, due to the strong electrostatic interaction between ferroelectric and ionic defect dipoles. The crucial role of thermally-activated displacive instability of Cu ions is confirmed by the single-crystal X-ray crystallography results. The findings provide fundamental insight into the ionic kinetics under an electric field in crystals with coexisting dipole order (ferroelectricity) and disorder (ionic defect and conductivity). Last but not least, we demonstrate that the spontaneous ionic defect-polarization interlock can lead to permanent ferroelectric retention, which is essential for information storage.
Ionic conduction in a ferroelectric leads to anomalous polarization switching kinetics but prevents retention failure.
Abstract
Piezoelectric materials convert mechanical stress to electrical energy and thus are widely used in energy harvesting and wearable devices. However, in the piezoelectric family, there are two ...pairs of properties that improving one of them will generally compromises the other, which limits their applications. The first pair is piezoelectric strain and voltage constant, and the second is piezoelectric performance and mechanical softness. Here, we report a molecular bond weakening strategy to mitigate these issues in organic-inorganic hybrid piezoelectrics. By introduction of large-size halide elements, the metal-halide bonds can be effectively weakened, leading to a softening effect on bond strength and reduction in polarization switching barrier. The obtained solid solution C
6
H
5
N(CH
3
)
3
CdBr
2
Cl
0.75
I
0.25
exhibits excellent piezoelectric constants (
d
33
= 367 pm/V,
g
33
= 3595 × 10
−3
Vm/N), energy harvesting property (power density is 11 W/m
2
), and superior mechanical softness (0.8 GPa), promising this hybrid as high-performance soft piezoelectrics.
The objective of this study was to investigate the effects of simvastatin (SIM) on lipid metabolism disorders and gut microbiota in high-fat diet-induced hyperlipidemic rats. The obtained results ...revealed that feeding rats with SIM (20 mg/kg/day) significantly decreased serum lipid level and inhibited hepatic lipid accumulation and steatosis. Histological analysis further indicated that SIM reduced lipid deposition in adipocytes and hepatocytes in comparison with that of the HFD group. The underlying mechanisms of SIM administration against HFD-induced hyperlipidemia were also studied by UPLC-Q-TOF/MS-based liver metabonomics coupled with pathway analysis. Metabolic pathway enrichment analysis of liver metabolites with significant difference in abundance indicated that fatty acids metabolism and amino acid metabolism were the main metabolic pathways altered by SIM administration. Meanwhile, operational taxonomic units (OTUs) analysis revealed that oral administration of SIM altered the composition of gut microbiota, including
(OTU960) and
(OTU152), and so on. Furthermore, SIM treatment also regulated the mRNA levels of the genes involved in lipid and cholesterol metabolism. Immunohistochemistry (IHC) analysis of the liver-related proteins (CD36, CYP7A1 and SREBP-1C) showed that oral administration of SIM could regulate the levels of the protein expression related to hepatic lipid metabolism.
Organic–inorganic hybrid perovskites with considerable dielectric differences near the phase transition are potential candidates as phase transition materials (PTMs). However, compared with ...traditional PTMs, which require multiple switchable channels, the hybrid perovskites so far show only switching behavior in dielectric constants. We herein report a new crystal design strategy and successful synthesis of a two-dimensional perovskite (C6H5C2H4NH3)2MnCl4. In this hybrid perovskite, the manganese chloride octahedron is a crystal field sensitive luminescent molecular system. The distortion level of MnCl6 4– also depends on temperature during the order–disorder phase transition. Hence, such a manganese octahedron-based perovskite can exhibit switching behaviors in both dielectric and optical properties. We observe a 14% decrease in optical absorption and 1.6 times increase in dielectric constant during the phase transition at 365 K. In addition, the characteristic photoluminescence decreases by 17% in intensity. Such a molecule-based crystal design paves a new way to explore multifunctional PTMs based on organic–inorganic perovskites.
Two-dimensional (2D) layered lead halide perovskites with large exciton binding energies, efficient radiative recombination, and outstanding environmental stability are regarded as supreme candidates ...for realizing highly compact and ultralow threshold lasers. However, continuous-wave (CW) pumped lasing of 2D lead halide perovskites, as the precondition for the electrically pumped lasing, is still challenging. Here, we tackled this challenge by demonstrating lasing emission in phenylethylammonium lead iodide (PEA)2PbI4 embedded in a vertical microcavity under continuous pumping at room temperature. The millimeter-sized (PEA)2PbI4 single crystal was obtained from a two-step seed-growth method, showing high crystallization, excellent thermal stability, and outstanding optical properties. We used the exfoliated (PEA)2PbI4 thin flake as the gain medium to construct a vertical-cavity surface-emitting laser (VCSEL), showing robust single-mode CW lasing operation with an ultra-low threshold of 5.7 W cm−2 at room temperature, attributed to strong optical confinement in the high-Q cavity. Our findings provide a strategy to design and fabricate solution-based 2D perovskite VCSELs and mark a significant step toward the next-generation of coherent light sources.
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•Designed a five-tier nested experimental watershed for multi-scale water cycle study.•Hydrological processes exhibit a spatiotemporal scaling effect.•Canopy leaf density has an ...exponential effect on rainfall interception.•Surface runoff serves as a major component of total runoff in the humid zone.
This paper presents the background, scientific objectives, experimental design, and preliminary achievements of the Xin’anjiang nested experimental watershed (XAJ-NEW), implemented in 2017 in eastern China, which has a subtropical humid monsoon climate and a total area of 2674 km2. The scientific objectives of the XAJ-NEW include building a comprehensive, multiscale, and nested hydrometeorological monitoring and experimental program, strengthening the observation of the water cycle, discovering the spatiotemporal scaling effects of hydrological processes, and revealing the mechanisms controlling runoff generation and partitioning in a typical humid, hilly area. After two years of operation, preliminary results indicated scale-dependent variability in key hydrometeorological processes and variables such as precipitation, runoff, groundwater, and soil moisture. The effects of canopy interception and runoff partitioning between the surface and subsurface were also identified. Continuous operation of this program can further reveal the mechanisms controlling runoff generation and partitioning, discover the spatiotemporal scaling effects of hydrological processes, and understand the impacts of climate change on hydrological processes. These findings provide new insights into understanding multiscale hydrological processes and their responses to meteorological forcings, improving model parameterization schemes, and enhancing weather and climate forecast skills.
Recently, there has been growing interest in the field of flat-band physics due to its attractive properties and wide range of practical applications. In this study, we introduce two novel ...two-dimensional monolayers, namely B
3
C
11
O
6
and B
3
C
15
O
6
, which exhibit a flat band near the Fermi level. These monolayers have been found to be energetically favorable, dynamically stable, and thermodynamically stable based on formation energies, phonon spectra, and molecular dynamics simulations. The nearly flat band (NFB) in B
3
C
11
O
6
arises from the extended kagome sublattice of carbon atoms. Due to the strong interaction between carbon atoms beyond their nearest neighbors, the bandwidth of the initial flat band is extended to approximately 0.5 eV. Nevertheless, there is still a prominent peak in the density of states near the Fermi level. On the other hand, the NFB in B
3
C
15
O
6
originates from the localized states of the carbon five-ring structure, which forms a distorted kagome lattice. The presence and characteristics of the NFB strongly depend on the interactions between next-nearest neighbors. Interestingly, the partially occupied NFB in B
3
C
11
O
6
leads to spin splitting, resulting in a transformation of the system into a ferromagnetic metal. Our research not only presents two types of lattices capable of hosting flat bands or NFBs, but also provides two monolayers that can be employed to investigate various intriguing quantum phases.
Two new two-dimensional single-layer materials exhibit nearly flat bands near the Fermi level.
Recently, there has been growing interest in the field of flat-band physics due to its attractive properties and wide range of practical applications. In this study, we introduce two novel ...two-dimensional monolayers, namely B 3 C 11 O 6 and B 3 C 15 O 6 , which exhibit a flat band near the Fermi level. These monolayers have been found to be energetically favorable, dynamically stable, and thermodynamically stable based on formation energies, phonon spectra, and molecular dynamics simulations. The nearly flat band (NFB) in B 3 C 11 O 6 arises from the extended kagome sublattice of carbon atoms. Due to the strong interaction between carbon atoms beyond their nearest neighbors, the bandwidth of the initial flat band is extended to approximately 0.5 eV. Nevertheless, there is still a prominent peak in the density of states near the Fermi level. On the other hand, the NFB in B 3 C 15 O 6 originates from the localized states of the carbon five-ring structure, which forms a distorted kagome lattice. The presence and characteristics of the NFB strongly depend on the interactions between next-nearest neighbors. Interestingly, the partially occupied NFB in B 3 C 11 O 6 leads to spin splitting, resulting in a transformation of the system into a ferromagnetic metal. Our research not only presents two types of lattices capable of hosting flat bands or NFBs, but also provides two monolayers that can be employed to investigate various intriguing quantum phases.
Recently, there has been growing interest in the field of flat-band physics due to its attractive properties and wide range of practical applications. In this study, we introduce two novel ...two-dimensional monolayers, namely B3C11O6 and B3C15O6, which exhibit a flat band near the Fermi level. These monolayers have been found to be energetically favorable, dynamically stable, and thermodynamically stable based on formation energies, phonon spectra, and molecular dynamics simulations. The nearly flat band (NFB) in B3C11O6 arises from the extended kagome sublattice of carbon atoms. Due to the strong interaction between carbon atoms beyond their nearest neighbors, the bandwidth of the initial flat band is extended to approximately 0.5 eV. Nevertheless, there is still a prominent peak in the density of states near the Fermi level. On the other hand, the NFB in B3C15O6 originates from the localized states of the carbon five-ring structure, which forms a distorted kagome lattice. The presence and characteristics of the NFB strongly depend on the interactions between next-nearest neighbors. Interestingly, the partially occupied NFB in B3C11O6 leads to spin splitting, resulting in a transformation of the system into a ferromagnetic metal. Our research not only presents two types of lattices capable of hosting flat bands or NFBs, but also provides two monolayers that can be employed to investigate various intriguing quantum phases.
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