Jing Zhang

We report experimental and theoretical studies on the magnetoelastic interactions in MnPS 3 . Raman scattering response measured as a function of temperature shows a blue shift of the Raman active modes at 120.2 and 155.1 cm −1 , when the temperature is raised across the antiferromagnetic-paramagnetic transition. Density functional theory (DFT) calculations have been performed to estimate the effective exchange interactions and calculate the Raman active phonon modes. The calculations lead to the conclusion that the peculiar behavior with temperature of the two low energy phonon modes can be explained by the symmetry of their corresponding normal coordinates which involve the virtual modification of the super-exchange angles associated with the leading antiferromagnetic (AFM) interactions.

Quantum confinement endows two-dimensional (2D) layered materials with exceptional physics and novel properties compared to their bulk counterparts. Although certain two- and few-layer configurations of graphene have been realized and studied, a systematic investigation of the properties of arbitrarily layered graphene assemblies is still lacking. We introduce theoretical concepts and methods for the processing of materials information, and as a case study, apply them to investigate the electronic structure of multi-layer graphene-based assemblies in a high-throughput fashion. We provide a critical discussion of patterns and trends in tight binding band structures and we identify specific layered assemblies using low-dispersion electronic bands as indicators of potentially interesting physics like strongly correlated behavior. A combination of data-driven models for visualization and prediction is used to intelligently explore the materials space. This work more generally aims t...

2D materials support unique excitations of quasi-particles that consist of a material excitation and photons called polaritons. Especially interesting are in-plane propagating polaritons, which can be confined to a single monolayer and carry large momentum. In this work, we theoretically predict the existence of a new type of in-plane propagating polariton, supported on monolayer transition-metal-dicalcogonides (TMDs) in the visible spectrum. This 2D in-plane exciton-polariton (2DEP) is described by the coupling of an electromagnetic light field with the collective oscillations of the excitons supported by monolayer TMDs. We experimentally demonstrate the specific conditions required for the excitation of the 2DEP and show that these can be achieved if the TMD is encapsulated with hexagonal-boron-nitride (hBN) and cooled to cryogenic temperatures. In addition, we compare the properties of the 2DEP with those of the surface-plasmon-polariton at the same spectral range, and find t...

Two‐dimensional (2D) layered membranes are a multidisciplinary selective unit for possessing parallel interlayer channels to control mass transport. Besides these flat channels, wrinkled structures can also emerge to affect transmembrane transport. The formation and tuning of nanowrinkles are studied in graphene‐based membranes to understand their role in regulating mass transport in 2D membranes.

Abstract

Laminar membranes stacked by 2D materials are an emerging selective unit in separating processes across disciplines for their controllable mass transport properties. In general, parallel nanochannels formed between neighboring layers, owing to their adjustable size and surface chemistry, are considered the dominant transport regulator. Besides these flat interlayer channels, wrinkled morphology has also existed in 2D membranes, but the structure and potential transporting role of such curved channel remain largely unexplored. This study demonstrates that nanowrinkles are intrinsically formed in graphene‐based membranes, featuring an arc‐like shape with around 2.5 nm high center and two narrow wedge corners. By a facile “solvent‐treatment” during assembly, the membranes are tuned to possess different wrinkle density. In transport tests involving water and ions, the appearance of more wrinkles yields higher water permeation yet has limited effect on ion passage. These findings suggest that nanowrinkles by themselves serve as fast transporting ways while their connection with narrow interlayer channels can form a selective network. Results here are expected to deepen the understanding of mass transport mechanisms in current laminar membranes (e.g., graphene‐based) and provide strategies for designing future 2D membranes via wrinkle engineering.

An alcohol‐based electric‐field‐assisted plasma enhanced chemical vapor deposition method is developed to grow vertical graphene (VG) arrays with high thermal conductivity. Using this method, high‐quality and vertically aligned graphene sheets at a height of 18.7 µm are obtained. Thermal interface materials constructed with these VG arrays exhibit excellent thermal properties for the heat dissipation of electrical devices.

Abstract

Owing to the development of electronic devices moving toward high power density, miniaturization, and multifunction, research on thermal interface materials (TIMs) is become increasingly significant. Graphene is regarded as the most promising thermal management material owing to its ultrahigh in‐plane thermal conductivity. However, the fabrication of high‐quality vertical graphene (VG) arrays and their utilization in TIMs still remains a big challenge. In this study, a rational approach is developed for growing VG arrays using an alcohol‐based electric‐field‐assisted plasma enhanced chemical vapor deposition. Alcohol‐based carbon sources are used to produce hydroxyl radicals to increase the growth rate and reduce the formation of defects. A vertical electric field is used to align the graphene sheets. Using this method, high‐quality and vertically aligned graphene with a height of 18.7 µm is obtained under an electric field of 30 V cm⁻¹. TIMs constructed with the VG arrays exhibit a high vertical thermal conductivity of 53.5 W m⁻¹ K⁻¹ and a low contact thermal resistance of 11.8 K mm² W⁻¹, indicating their significant potential for applications in heat dissipation technologies.

Understanding deformation mechanisms in silicon is critical for reliable design of miniaturized devices operating at high temperatures. Bulk silicon is brittle, but it becomes ductile at about 540 °C. It creeps (deforms plastically with time) at high temperatures (∼800 °C). However, the effect of small size on ductility and creep...

Magnetic parameters can be efficiently estimated from an experimental observation of spin configuration by combining machine learning and micro‐magnetic simulation. The method includes learning a mapping from spin configurations to magnetic parameters on a small amount of micro‐magnetic simulated images and applying the trained machine learning model to a single unexplored experimental image to estimate its key parameters.

Abstract

Hamiltonian parameters estimation is crucial in condensed matter physics, but is time‐ and cost‐consuming. High‐resolution images provide detailed information of underlying physics, but extracting Hamiltonian parameters from them is difficult due to the huge Hilbert space. Here, a protocol for Hamiltonian parameters estimation from images based on a machine learning (ML) architecture is provided. It consists in learning a mapping between spin configurations and Hamiltonian parameters from a small amount of simulated images, applying the trained ML model to a single unexplored experimental image to estimate its key parameters, and predicting the corresponding materials properties by a physical model. The efficiency of the approach is demonstrated by reproducing the same spin configuration as the experimental one and predicting the coercive field, the saturation field, and even the volume of the experiment specimen accurately. The proposed approach paves a way to achieve a stable and efficient parameters estimation.

An intriguing and powerful molten‐salt‐assisted chemical vapor deposition strategy is developed to achieve effective metal substitutional doping of monolayer MoS₂. In this process, the salt with low melting point promotes the volatilization of the dopant precursors during the growth of monolayer MoS₂, which creates excellent conditions and opportunities for heteroatoms (Fe, Co, and Mn) incorporation.

Abstract

Substitutional doping of layered transition metal dichalcogenides (TMDs) has been proved to be an effective route to alter their intrinsic properties and achieve tunable bandgap, electrical conductivity and magnetism, thus greatly broadening their applications. However, achieving valid substitutional doping of TMDs remains a great challenge to date. Herein, a distinctive molten‐salt‐assisted chemical vapor deposition (MACVD) method is developed to match the volatilization of the dopants perfectly with the growth process of monolayer MoS₂, realizing the substitutional doping of transition metal Fe, Co, and Mn. This doping strategy effectively alters the electronic structure and phononic properties of the pristine MoS₂. In addition, a temperature‐dependent Raman spectrum is employed to explore the effect of dopants on the lattice dynamics and first‐order temperature coefficient of monolayer MoS₂, and this doping effect is illustrated in depth combined with the theoretical calculation. This work provides an intriguing and powerful doping strategy for TMDs through employing molten salt in the CVD system, paving the way for exploring new properties of 2D TMDs and extending their applications into spintronics, catalytic chemistry and photoelectric devices.

Graphene oxide liquid crystal (GOLC) fibers with hierarchical core‐skin architectures are successfully fabricated using an innovative synchronous nanofluidic rectification technique, in which the hydrogel skin formation and graphene oxide sheet assemblies are synchronous. The GOLC fibers possess a reversed cholesteric order and exhibit controllable optical appearances that can be used for optical sensing and recognition.

Abstract

Colloidal liquid crystals (LCs) formed by nanoparticles hold great promise for creating new structures and topologies. However, achieving highly ordered hierarchical architectures and stable topological configurations is extremely challenging, mainly due to the liquid‐like fluidity of colloidal LCs in nature. Herein, an innovative synchronous nanofluidic rectification (SNR) technique for generating ultralong graphene oxide (GO) liquid crystal (GOLC) fibers with hierarchical core‐skin architectures is presented, in which the GO sheet assemblies and hydrogel skin formation are synchronous. The SNR technique conceptually follows two design principles: horizontal polymer‐flow promotes the rapid planar alignment of GO sheets and drives the chiral‐reversing of cholesteric GOLCs, and in situ formed hydrogel skin affords some protection against environmental impact to maintain stable topological configurations. Importantly, the dried fibers retain the smooth surface and ordered internal structures, achieving high mechanical strength and flexibility. The linear and circular polarization potential of GOLC fibers are demonstrated for optical sensing and recognition. This work may open an avenue toward the scalable manufacture of uniform and robust, yet highly anisotropic, fiber‐shaped functional materials with complex internal architectures.

Nature Nanotechnology, Published online: 29 June 2020; doi:10.1038/s41565-020-0717-2

Formation of interlayer excitons with high oscillator strength in a WS2/HfS2 heterostructure enables the realization of high-responsivity room-temperature mid- and long-wavelength infrared photodetectors.

Nature Nanotechnology, Published online: 29 June 2020; doi:10.1038/s41565-020-0715-4

The accidental band-crossing origin of Weyl nodes paired with the absence of sizeable band gaps hampers the exploitation of low-energy relativistic quasiparticles in Weyl semimetals. In a gate-tunable high-quality tellurene film, quantum Hall measurements unveil a topologically non-trivial π Berry phase caused by unconventional Weyl nodes in these tellurium two-dimensional sheets.

A novel postcuring transfer process of graphene is introduced to greatly enhance the interfacial strength at both the graphene/poly(methyl methacrylate) (PMMA) and PMMA/polydimethylsiloxane (PDMS) interfaces. Moreover, an interesting continuous light diffraction pattern through the delamination‐free functional graphene surface with multiscale conformal wrinkle patterns, which differs greatly from discrete light diffraction patterns, is observed.

Abstract

Obtaining a delamination‐free wrinkled functional graphene surface in layered systems is an interesting challenge because the interface is usually too weak to withstand interfacial stress mismatch, which can trigger mechanical instability. In this paper, a general strategy is proposed toward addressing the delamination limitation imposed by fabricating conformal graphene wrinkles with bilayer systems of poly(methyl methacrylate) (PMMA) and polydimethylsiloxane (PDMS). To improve the interfacial strength, a postcuring transfer process is introduced to form a gradient interface layer without interfacial liquid between the PMMA and PDMS by entanglement of polymer chains during high‐temperature curing. Compared to the conventional wet transfer of graphene,the transfer method can greatly enhance the interfacial strength. The chemical and mechanical mechanisms underlying the enhancement are revealed both experimentally and theoretically in terms of the transition from the buckled‐induced delamination state to the delamination‐free wrinkled state. Moreover, the light diffraction behaviors of multiscale graphene wrinkles are initially demonstrated to be an interesting continuous pattern induced by overlapping. The delamination‐free conformal wrinkled functional graphene surface can provide valuable insight and design guidelines for the fundamental problems of deformed graphene and its applications in flexible functional devices.

The boundary modes of topological insulators are protected by the symmetries of the nontrivial bulk electronic states. Unless these symmetries are broken, they can give rise to novel phenomena, such as the quantum spin Hall effect in one-dimensional (1D) topological edge states, where quasiparticle backscattering is suppressed by time-reversal symmetry...

Atomistic simulations of dislocation mobility reveal that body-centered cubic (BCC) high-entropy alloys (HEAs) are distinctly different from traditional BCC metals. HEAs are concentrated solutions in which composition fluctuation is almost inevitable. The resultant inhomogeneities, while locally promoting kink nucleation on screw dislocations, trap them against propagation with an appreciable energy...

Herein, the anisotropic nanoscale features of antiphase boundaries in 2H phase of transition metal dichalcogenides are investigated (i.e., saw‐toothed for transition metal‐facing and linear for chalcogen‐facing antiphase boundaries) in order to preserve the thermodynamically most stable atomic configurations. In addition, they have different in‐plane transport behavior because lots of kinks in the saw‐toothed antiphase boundary act as scattering centers.

Abstract

Antiphase boundaries (APBs) in 2D transition metal dichalcogenides have attracted wide interest as 1D metallic wires embedded in a semiconducting matrix, which could be exploited in fully 2D‐integrated circuits. Here, the anisotropic morphologies of APBs (i.e., linear and saw‐toothed APBs) in the nanoscale are investigated. The experimental and computational results show that despite their anisotropic nanoscale morphologies, all APBs adopt a predominantly chalcogen‐oriented dense structure to maintain the energetically most stable atomic configuration. Moreover, the effect of the nanoscale morphology of an APB on electron transport from two‐probe field effect transistor measurements is investigated. A saw‐toothed APB has a considerably lower electron mobility than a linear APB, indicating that kinks between facets are the main factors of scattering. The observations contribute to the systematical understanding of the faceted APBs and its impact on electrical transport behavior and it could potentially extend the applications of 2D materials through defect engineering to achieve the desired properties.

Nature Nanotechnology, Published online: 22 June 2020; doi:10.1038/s41565-020-0700-y

Tuning a flexoelectric polarization field in centrosymmetric semiconductor single crystals enables the observation of a giant flexoelectronic effect.

Applications of 2D materials often require deposition of non‐2D metals and non‐2D metal‐oxides but mechanisms of such non‐2D/2D interfacing remain elusive. Here, atomically resolved scanning transmission electron microscopy follows in a “quasi‐in‐situ” fashion the entire fabrication cycle of application‐relevant non‐2D In and non‐2D In₂O₃ nanostructures on graphene and thereby clarifies key factors governing non‐2D/2D interfacing the atomic scale.

Abstract

Many applications of 2D materials require deposition of non‐2D metals and metal‐oxides onto the 2D materials. Little is however known about the mechanisms of such non‐2D/2D interfacing, particularly at the atomic scale. Here, atomically resolved scanning transmission electron microscopy (STEM) is used to follow the entire physical vapor deposition (PVD) cycle of application‐relevant non‐2D In/In₂O₃ nanostructures on graphene. First, a “quasi‐in‐situ” approach with indium being in situ evaporated onto graphene in oxygen‐/water‐free ultra‐high‐vacuum (UHV) is employed, followed by STEM imaging without vacuum break and then repeated controlled ambient air exposures and reloading into STEM. This allows stepwise monitoring of the oxidation of specific In particles toward In₂O₃ on graphene. This is then compared with conventional, scalable ex situ In PVD onto graphene in high vacuum (HV) with significant residual oxygen/water traces. The data shows that the process pathway difference of oxygen/water feeding between UHV/ambient and HV fabrication drastically impacts not only non‐2D In/In₂O₃ phase evolution but also In₂O₃/graphene out‐of‐plane texture and in‐plane rotational van‐der‐Waals epitaxy. Since non‐2D/2D heterostructures' properties are intimately linked to their structure and since influences like oxygen/water traces are often hard to control in scalable fabrication, this is a key finding for non‐2D/2D integration process design.

Graphene supported electrocatalysts, including RuO₂ and Pt, are synthesized via laser (248 nm) irradiation of semiconducting electrochemical graphene oxide (EGO) and metal salts precursor solutions. The catalysts show superior electrocatalytic activities for oxygen evolution reaction and hydrogen evolution reaction, which is attributed to the homogeneous distribution of ultrafine nanoparticles (≈2 nm) on the deeply reduced EGO support.

Abstract

Simple, yet versatile, methods to functionalize graphene flakes with metal (oxide) nanoparticles are in demand, particularly for the development of advanced catalysts. Herein, based on light‐induced electrochemistry, a laser‐assisted, continuous, solution route for the simultaneous reduction and modification of graphene oxide with catalytic nanoparticles is reported. Electrochemical graphene oxide (EGO) is used as starting material and electron–hole pair source due to its low degree of oxidation, which imparts structural integrity and an ability to withstand photodegradation. Simply illuminating a solution stream containing EGO and metal salt (e.g., H₂PtCl₆ or RuCl₃) with a 248 nm wavelength laser produces reduced EGO (rEGO, oxygen content 4.0 at%) flakes, decorated with Pt (≈2.0 nm) or RuO₂ (≈2.8 nm) nanoparticles. The RuO₂–rEGO flakes exhibit superior catalytic activity for the oxygen evolution reaction, requiring a small overpotential of 225 mV to reach a current density of 10 mA cm⁻². The Pt–rEGO flakes (10.2 wt% of Pt) show enhanced mass activity for the hydrogen evolution reaction, and similar performance for oxygen reduction reaction compared to a commercial 20 wt% Pt/C catalyst. This simple production method is also used to deposit PtPd alloy and MnO _x nanoparticles on rEGO, demonstrating its versatility in synthesizing functional nanoparticle‐modified graphene materials.

Due to the prominent contribution of both the intrinsic and extrinsic Hall mechanisms, significantly enhanced AHC (≈1850 Ω⁻¹ cm⁻¹) and AHA (≈33%) are obtained at the zero field in the magnetic Weyl semimetal Co₃Sn₂S₂ by controlling slight Fe doping. In comparison with other AHE materials, the AHC and AHA for Co_{3– x} Fe _x Sn₂S₂ exhibit record values, which can greatly benefit Weyltronics applications.

Abstract

The anomalous Hall effect (AHE) can be induced by intrinsic mechanisms due to the band Berry phase and extrinsic one arising from the impurity scattering. The recently discovered magnetic Weyl semimetal Co₃Sn₂S₂ exhibits a large intrinsic anomalous Hall conductivity (AHC) and a giant anomalous Hall angle (AHA). The predicted energy dependence of the AHC in this material exhibits a plateau at 1000 Ω⁻¹ cm⁻¹ and an energy width of 100 meV just below E _F, thereby implying that the large intrinsic AHC will not significantly change against small‐scale energy disturbances such as slight p‐doping. Here, the extrinsic contribution is successfully triggered from alien‐atom scattering in addition to the intrinsic one of the pristine material by introducing a small amount of Fe dopant to substitute Co in Co₃Sn₂S₂. The experimental results show that the AHC and AHA can be prominently enhanced up to 1850 Ω⁻¹ cm⁻¹ and 33%, respectively, owing to the synergistic contributions from the intrinsic and extrinsic mechanisms as distinguished by the TYJ model. In particular, the tuned AHA exhibits a record value among known magnetic materials in low fields. This study opens up a pathway to engineer giant AHE in magnetic Weyl semimetals, thereby potentially advancing the topological spintronics/Weyltronics.

Anisotropic particles that have one hemisphere selectively loaded with magnetite nanoparticles rotate in response to magnetic fields as indicated by visually observable color changes.

Abstract

Magnetic Janus particles (MJPs) have received considerable attention for their rich assembly behavior and their potential technological role in applications ranging from simple magnetophoretic displays to smart cloaking devices. However, further progress is hampered by the lack of predictive understanding of the cooperative self‐assembly behavior of MJPs and appropriate dynamic control mechanisms. In this paper, a detailed experimental and theoretical investigation into the magnetically directed spatiotemporal self‐assembly and switching of MJPs is presented. For this purpose, a novel type of MJPs with defined hemispherical compartments carrying superparamagnetic iron oxide nanoparticles as well as a novel simulation model to describe their cooperative switching behavior is established. Combination of the theoretical and experimental work culminates in a simple method to direct assemblies of MJPs, even at high particle concentrations. In addition, a magnetophoretic display with switchable MJPs is developed on the basis of the theoretical findings to demonstrate the potential usefulness of controlled large‐area assemblies of magnetic Janus particles.

Topological electrons in semimetals are usually vulnerable to chemical doping and environment change, which restricts their potential application in future electronic devices. In this paper, we report that the type-II Dirac semimetal VAl3 hosts exceptional, robust topological electrons which can tolerate extreme change of chemical composition. The Dirac electrons remain...

A class of peasecod‐like hollow Yb³⁺/Er³⁺‐doped Li₄ZrF₈ upconverting nanocrystals (UCNCs) that features a 2D layered crystal lattice is reported. Abnormal green upconverting luminescence that cannot be achieved in the solid UCNCs is observed in these peasecod‐like hollow UCNCs, thereby making them suitable as supersensitive nanothermometers with a wide temperature range for optical temperature sensing.

Abstract

Trivalent lanthanide (Ln³⁺)‐doped hollow upconversion nanocrystals (UCNCs) usually exhibit unique optical performance that cannot be realized in their solid counterparts, and thus have been receiving tremendous interest from their fundamentals to diverse applications. However, all currently available Ln³⁺‐doped UCNCs are solid in appearance, the preparation of hollow UCNCs remains nearly untouched hitherto. Herein, a class of UCNCs based on Yb³⁺/Er³⁺‐doped tetralithium zirconium octafluoride (Li₄ZrF₈:Yb/Er) featuring 2D layered crystal lattice is reported, which makes the fabrication of hollow UCNCs with a peasecod‐like shape possible after Ln³⁺ doping. By employing the first‐principle calculations, the unique peasecod‐like hollow nanoarchitecture primarily associated with the hetero‐valence Yb³⁺/Er³⁺ doping into the 2D layered crystal lattice of Li₄ZrF₈ matrix is revealed. Benefiting from this hollow nanoarchitecture, the resulting Li₄ZrF₈:Yb/Er UCNCs exhibit an abnormal green upconversion luminescence in terms of the population ratio between two thermally coupled states (²H_11/2 and ⁴S_3/2) of Er³⁺ relative to their solid Li₂ZrF₆:Yb/Er counterparts, thereby allowing to prepare the first family of hollow Ln³⁺‐doped UCNCs as supersensitive luminescent nanothermometer with almost the widest temperature sensing range (123–800 K). These findings described here unambiguously pave a new way to fabricate hollow Ln³⁺‐doped UCNCs for numerous applications.

Nature Nanotechnology, Published online: 15 June 2020; doi:10.1038/s41565-020-0691-8

Radiative Auger processes in the single-photon limit provide insights in single particle states of quantum dots, which remain otherwise inaccessible.

Nature Nanotechnology, Published online: 10 June 2020; doi:10.1038/s41565-020-0721-6

The efforts to develop electron lens systems that can achieve atomic resolution in transmission electron microscopy have been awarded the most prestigious accolade dedicated to nanoscience.

Nature Nanotechnology, Published online: 12 June 2020; doi:10.1038/s41565-020-0689-2

An approach to identify and classify different shapes of nanomaterials starting from transmission electron microscopy images could be a powerful instrument to categorize the different shapes of nanoparticles and fingerprint the geometrical variability of an ensemble.

This review systematically introduces the classic synthesis strategies, catalytic performances, and mechanisms of single‐atom catalysts with Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Sn, W, Bi, Ru, Rh, Pd, Ag, Ir, Pt, and Au as single or dual metal sites in oxygen reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, hydrogen oxidation reaction, CO₂ reduction reaction, and nitrogen reduction reaction.

Abstract

The recent advances in electrocatalysis for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), carbon dioxide reduction reaction (CO₂RR), and nitrogen reduction reaction (NRR) are thoroughly reviewed. This comprehensive review focuses on the single‐atom catalysts (SACs) including Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Sn, W, Bi, Ru, Rh, Pd, Ag, Ir, Pt, and Au with single‐metal sites or dual‐metal sites. The recent development of single‐atom electrocatalysts with novel configurations and compositions is documented. The understanding of the process–structure–property relationships is highlighted. For the SACs, their electrocatalytic performance and stability in fuel cells, zinc–air batteries, electrolyzers, CO₂RR, and NRR are summarized. The challenges and perspectives in the emerging field of single‐atom electrocatalysis are discussed.

The research progress in graphene‐ and MXene‐based microwave absorption (MA) materials are reviewed with a special focus on advances in general strategies. Moreover, their respective advantages in achieving high‐performance MA are presented based on performance comparison. Furthermore, the future challenges, research orientation, and prospect for these MA materials are also highlighted and discussed.

Abstract

Searching for advanced microwave absorption (MA) nanomaterials is one of the most feasible ways to address the increasing electromagnetic pollution in both military and civil fields. To this end, graphene and MXene have won the widespread attention as the main representatives due to their remarkable structures and properties. The common features such as the large aspect ratio, active chemical surface, and varieties of synthesis processes endow graphene and MXene with unique superiorities for developing high‐efficiency MA structures, in particular lightweight assemblies and various hybrids. Meanwhile, the structural and performance differences (such as different conductivities) between them result in distinctive techniques in the design, fabrication, and application of their MA materials. Herein, the research progress in graphene‐ and MXene‐based MA materials is reviewed, with a special focus on advances in general strategies. Moreover, through the comparison between graphene‐ and MXene‐based MA materials, their respective advantages in achieving high‐performance MA are presented. Furthermore, the future challenge, research orientation, and prospect for these MA materials are also highlighted and discussed.

As revealed by density functional theory calculations and analog simulations, nanopatterned graphene is obtained by selective growth on the c‐plane of nanopatterned sapphire substrates. Moreover, the coverage of graphene can be controlled by adjusting the carbon precursor and system pressure. The thus obtained patterned graphene ensures selective nucleation of aluminium nitride on the c‐plane with well‐aligned orientation, targeting high‐performance light‐emitting diodes.

Abstract

Direct growth of graphene films on functional substrates is immensely beneficial for the large‐scale applications of graphene by avoiding the transfer‐induced issues. Notably, the selective growth of patterned graphene will further boost the development of graphene‐based devices. Here, the direct growth of patterned graphene on the c‐plane of nanopatterned sapphire substrate (NPSS) is realized and the superiority of the patterned graphene for high‐performance ultraviolet light‐emitting diodes (UV‐LED) is demonstrated. As confirmed by density functional theory calculations and analog simulations, compared to the concave r‐plane the flat c‐plane of NPSS is characterized by a lower active barrier for methane decomposition and carbon species diffusion, as well as a greater supply of carbon precursor for graphene growth. The synthesized patterned graphene on the c‐plane of NPSS is verified to be monolayer and high quality. The patterned graphene enables the selective and well‐aligned nucleation of aluminium nitride (AlN) to promote rapid epitaxial lateral overgrowth of single‐crystal AlN films with low dislocation density. Consequently, the fabricated UV‐LED demonstrates high luminescence intensity and stability. The method is suitable for obtaining various patterned graphene by substrate design, which will allow for greater progress in the cutting‐edge applications of graphene.

Since their first discovery in 2011, MXenes have gained ever increasing interest. Despite their intriguing optical and electrical properties for optoelectronics, 2D MXenes have been thus far marginally explored for photodetectors. Nonetheless, the progress over the past few years cannot be ignored. In this review, the recent development of MXene photodetectors is summarized, including simple photoconductors, self‐driven photodetectors, and plasmon‐enhanced photodetectors.

Abstract

A new class of 2D transition metal carbides, carbonitrides and nitrides, termed MXenes, has emerged as a new candidate for many applications in electronics, optoelectronics, and energy storage. Since their first discovery in 2011, MXenes have gathered increasingly more interest owing to their unique physical, chemical, and mechanical properties that can be tuned by different surface terminations and transition metals. In particular, the intriguing optical and electrical properties, including transparency, saturable absorption, and high conductivity, grant MXenes various roles in photodetectors, such as transparent electrodes, Schottky contacts, photoabsorbers, and plasmonic materials. Given the solution‐processability, MXenes also hold great potential for large‐scale synthesis, and thus are favored for a number of electronic and photonic device applications. In this review, recent advances in photodetectors based on 2D MXenes are summarized. Despite the fact that such applications have only recently been explored compared with other 2D materials, MXenes have shown promise in low‐cost and high‐performance photodetection.

Two-dimensional (2D) nanofluidic ion transporting membranes show great promise in harvesting the “blue” osmotic energy between river water and sea water. Black phosphorus (BP), an emerging layered material, has recently been explored for a wide range of ambient applications. However, little attention has been paid to the extraction of the...