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In the last decade, two‐dimensional layered materials (2DLMs) have been drawing extensive attentions due to their unique properties, such as absence of surface dangling bonds, thickness‐dependent bandgap, high absorption coefficient, large specific surface area, and so on. But the high‐quality growth and transfer of wafer‐scale 2DLMs films is still a great challenge for the commercialization of pure 2DLMs‐based photodetectors. Conversely, the material growth and device fabrication technologies of three‐dimensional (3D) semiconductors photodetectors tend to be gradually matured. However, the further improvement of the photodetection performance is limited by the difficult heterogeneous integration or the inferior crystal quality via heteroepitaxy. Fortunately, 2D/3D van der Waals heterostructures (vdWH) combine the advantages of the two types of materials simultaneously, which may provide a new platform for developing high‐performance optoelectronic devices. Here, we first discuss the unique advantages of 2D/3D vdWH for the future development of photodetection field and simply introduce the structure categories, working mechanisms, and the typical fabrication methods of 2D/3D vdWH photodetector. Then, we outline the recent progress on 2D/3D vdWH‐based photodetection devices integrating 2DLMs with the traditional 3D semiconductor materials, including Si, Ge, GaAs, AlGaN, SiC, and so on. Finally, we highlight the current challenges and prospects of heterointegrating 2DLMs with traditional 3D semiconductors toward photodetection applications. image

The significance of graphene and its two-dimensional (2D) analogous inorganic layered materials especially as hexagonal boron nitride (h-BN) and molybdenum disulphide (MoS 2 ) for “clean energy” applications became apparent over the last few years due to their extraordinary properties. In this review article we study the current progress and selected challenges in the syntheses of graphene, h-BN and MoS 2 including energy storage applications as supercapacitors and batteries. Various substrates/catalysts (metals/insulator/semiconducting) have been used to obtain graphene, h-BN and MoS 2 using different kinds of precursors. The most widespread methods for synthesis of graphene, h-BN and MoS 2 layers are chemical vapor deposition (CVD), plasma-enhanced CVD, hydro/solvothermal methods, liquid phase exfoliation, physical methods etc. Current research has shown that graphene, h-BN and MoS 2 layered materials modified with metal oxide can have an insightful influence on the performance of energy storage devices as supercapacitors and batteries. This review article also contains the discussion on the opportunities and perspectives of these materials (graphene, h-BN and MoS 2 ) in the energy storage fields. We expect that this written review article including recent research on energy storage will help in generating new insights for further development and practical applications of graphene, h-BN and MoS 2 layers based materials.

The Ni‐rich layered oxides with a Ni content of >0.5 are drawing much attention recently to increase the energy density of lithium‐ion batteries. However, the Ni‐rich layered oxides suffer from aggressive reaction of the cathode surface with the organic electrolyte at the higher operating voltages, resulting in consequent impedance rise and capacity fade. To overcome this difficulty, we present here a heterostructure composed of a Ni‐rich LiNi0.7Co0.15Mn0.15O2 core and a Li‐rich Li1.2− x Ni0.2Mn0.6O2 shell, incorporating the advantageous features of the structural stability of the core and chemical stability of the shell. With a unique chemical treatment for the activation of the Li2MnO3 phase of the shell, a high capacity is realized with the Li‐rich shell material. Aberration‐corrected scanning transmission electron microscopy (STEM) provides direct evidence for the formation of surface Li‐rich shell layer. As a result, the heterostructure exhibits a high capacity retention of 98% and a discharge‐voltage retention of 97% during 100 cycles with a discharge capacity of 190 mA h g−1 (at 2.0–4.5 V under C/3 rate, 1C = 200 mA g−1). To develop high‐performance cathodes, a heterostructure composed of Ni‐rich layered oxide core and a lithium‐rich Li1.2−xNi0.2Mn0.6O2 shell is explored. The heterostructure overcomes the critical drawbacks of both the surface electrochemical instability with electrolyte of the core material as well as the voltage decline problem of the shell layer.

Transition‐metal‐based layered double hydroxides (TM‐LDHs) nanosheets are promising electrocatalysts in the renewable electrochemical energy conversion system, which are regarded as alternatives to noble metal‐based materials. In this review, recent advances on effective and facile strategies to rationally design TM‐LDHs nanosheets as electrocatalysts, such as increasing the number of active sties, improving the utilization of active sites (atomic‐scale catalysts), modulating the electron configurations, and controlling the lattice facets, are summarized and compared. Then, the utilization of these fabricated TM‐LDHs nanosheets for oxygen evolution reaction, hydrogen evolution reaction, urea oxidation reaction, nitrogen reduction reaction, small molecule oxidations, and biomass derivatives upgrading is articulated through systematically discussing the corresponding fundamental design principles and reaction mechanism. Finally, the existing challenges in increasing the density of catalytically active sites and future prospects of TM‐LDHs nanosheets‐based electrocatalysts in each application are also commented. Current fabrication strategies to design transition‐metal‐based layered double hydroxides (TM‐LDHs) nanosheets are summarized. The electrocatalytic applications of these as‐fabricated TM‐LDHs nanosheets in oxygen evolution reaction, hydrogen evolution reaction, urea oxidation reaction, nitrogen reduction reaction, small molecule oxidation, and biomass derivatives upgrading are articulated through systematically discussing the corresponding fundamental design principles and reaction mechanism.

PurposeIn the pile-soil interaction system, the disturbed soil directly affects the safety of the laterally loaded pile. The soil displacement field helps to evaluate the range and degree of soil disturbance. This study presents a method of visualiziing the displacement field of the soil around the laterally loaded pile by using transparent soil technology, which overcomes the measurement obstacles caused by the non-transparency of the real soil.MethodsGlass sand and transparent pore solution were mixed to make a saturated transparent soil with two particle sizes (0.1 ~ 0.5 mm and 0.5 ~ 1 mm). Instead of real soil, transparent soil was used to observe the degree of disturbance in the process of interaction with laterally loaded piles. In addition, particle image velocimetry (PIV) was used to capture the displacement of transparent soil particles. The displacement of each particle was integrated into the displacement field by a MATLAB program.ResultsWhen a horizontal force was applied on the top of the pile, the particles in front of the pile were compressed, producing observable movement within a certain area. From the displacement vector diagram, it could be seen that the displacement area of the soil surface in front of the pile increases as the layer thickness of large particle soil increases. The vertical displacement of soil in front of the pile was compacted to form a wedge-shaped area under the horizontal load. The angle between the direction of soil motion and the horizontal plane was positively correlated with the thickness of the soil layer.ConclusionTransparent soil and particle image velocimetry can help reveal the displacement trends of the soil around a laterally loaded pile. Based on this, an early warning can be provided when the displacement value and displacement angle of the soil around the laterally loaded pile exceeds the normal range.

In this paper, we studied domination of a Triple layered fuzzy graph, Complement of a Triple layered fuzzy graph and Complete Triple layered fuzzy graph and established bounds for the same graphs.

Organic–inorganic layered perovskites, or Ruddlesden–Popper perovskites, are two-dimensional quantum wells with layers of leadhalide octahedra stacked between organic ligand barriers. The combination of their dielectric confinement and ionic sublattice results in excitonic excitations with substantial binding energies that are strongly coupled to the surrounding soft, polar lattice. However, the ligand environment in layered perovskites can significantly alter their optical properties due to the complex dynamic disorder of the soft perovskite lattice. Here, we infer dynamic disorder through phonon dephasing lifetimes initiated by resonant impulsive stimulated Raman photoexcitation followed by transient absorption probing for a variety of ligand substitutions. We demonstrate that vibrational relaxation in layered perovskite formed from flexible alkyl-amines as organic barriers is fast and relatively independent of the lattice temperature. Relaxation in layered perovskites spaced by aromatic amines is slower, although still fast relative to bulk inorganic lead bromide lattices, with a rate that is temperature dependent. Using molecular dynamics simulations, we explain the fast rates of relaxation by quantifying the large anharmonic coupling of the optical modes with the ligand layers and rationalize the temperature independence due to their amorphous packing. This work provides a molecular and time-domain depiction of the relaxation of nascent optical excitations and opens opportunities to understand how they couple to the complex layered perovskite lattice, elucidating design principles for optoelectronic devices.

Iron/manganese‐based layered transition metal oxides have risen to prominence as prospective cathodes for sodium‐ion batteries (SIBs) owing to their abundant resources and high theoretical specific capacities, yet they still suffer from rapid capacity fading. Herein, a dual‐strategy is developed to boost the Na‐storage performance of the Fe/Mn‐based layered oxide cathode by copper (Cu) doping and nanoengineering. The P2‐Na0.76Cu0.22Fe0.30Mn0.48O2 cathode material synthesized by electrospinning exhibits the pearl necklace‐like hierarchical nanostructures assembled by nanograins with sizes of 50–150 nm. The synergistic effects of Cu doping and nanotechnology enable high Na+ coefficients and low ionic migration energy barrier, as well as highly reversible structure evolution and Cu/Fe/Mn valence variation upon repeated sodium insertion/extraction; thus, the P2‐Na0.76Cu0.22Fe0.30Mn0.48O2 nano‐necklaces yield fabulous rate capability (125.4 mA h g−1 at 0.1 C with 56.5 mA h g−1 at 20 C) and excellent cyclic stability (≈79% capacity retention after 300 cycles). Additionally, a promising energy density of 177.4 Wh kg−1 is demonstrated in a prototype soft‐package Na‐ion full battery constructed by the tailored nano‐necklaces cathode and hard carbon anode. This work symbolizes a step forward in the development of Fe/Mn‐based layered oxides as high‐performance cathodes for SIBs. Pearl necklace‐like hierarchical nanostructures of a P2‐Na0.76Cu0.22Fe0.30Mn0.48O2 cathode are synthesized by electrospinning and evaluated in sodium‐ion batteries. The synergistic effects of Cu doping and nanoengineering enable high Na+ coefficients and low ionic migration energy barrier, as well as highly reversible structure evolution and Cu/Fe/Mn valence variation upon repeated sodium insertion/extraction, rendering fabulous rate capability and excellent cyclic stability.

Van der Waals layered transition metal dichalcogenides can exist in many different atomic and electronic phases. Such diverse polymorphisms not only provide a route for investigating novel topological states, such as quantum spin Hall insulators, superconductors and Weyl semimetals, but may also have applications in fields ranging from electronic and optical/quantum devices to electrochemical catalysis. And the methods for triggering robust phase transitions between polymorphs are evolving and diversifying--several growth processes, high-pressure/strain methods, and optical, electronic and chemical treatments have been developed. Here, we discuss recent progress on phase transitions and the related physics in layered materials, and demonstrate unique features compared with conventional solid-state materials.

Mars is known to host large quantities of water in solid or gaseous form, and surface rocks show clear evidence that there was liquid water on the planet in the distant past. Whether any liquid water remains on Mars today has long been debated. Orosei et al. used radar measurements from the Mars Express spacecraft to search for liquid water in Mars' southern ice cap (see the Perspective by Diez). They detected a 20-km-wide lake of liquid water underneath solid ice in the Planum Australe region. The water is probably kept from freezing by dissolved salts and the pressure of the ice above. The presence of liquid water on Mars has implications for astrobiology and future human exploration. Science , this issue p. 490 ; see also p. 448 Radar data from Mars Express show that there is a lake of liquid water underneath the solid ice of Mars’ southern ice cap. The presence of liquid water at the base of the martian polar caps has long been suspected but not observed. We surveyed the Planum Australe region using the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument, a low-frequency radar on the Mars Express spacecraft. Radar profiles collected between May 2012 and December 2015 contain evidence of liquid water trapped below the ice of the South Polar Layered Deposits. Anomalously bright subsurface reflections are evident within a well-defined, 20-kilometer-wide zone centered at 193°E, 81°S, which is surrounded by much less reflective areas. Quantitative analysis of the radar signals shows that this bright feature has high relative dielectric permittivity (>15), matching that of water-bearing materials. We interpret this feature as a stable body of liquid water on Mars.