Jing Zhang

P-doped PtTe₂ nanocages with the amorphous/crystalline interface are provided by a facile template-free synthesis, which exhibits well performance for HER. Proved by density functional theory calculations, P doping can contribute to the spontaneous defects formation of Te vacancies. The inherent correlation between the unique structure and the high performance is deeply explored.

Abstract

PtTe₂, a member of the noble metal dichalcogenides (NMDs), has aroused great interest in exploring its behavior in the hydrogen evolution reaction (HER) due to the unique type-II topological semimetallic nature. In this work, a simple template-free hydrothermal method to obtain the phosphorus-doped (P-doped) PtTe₂ nanocages with abundant amorphous and crystalline interface (A/C-P-PtTe₂) is developed. Revealed by density functional theory calculations, the atomic Te vacancies can spontaneously form on the basal planes of PtTe₂ by the P doping, which results in the unsaturated Pt atoms exposed as the active sites in the amorphous layer for HER. Owing to the defective structure, the A/C-P-PtTe₂ catalysts have the fast Tafel step determined kinetics in HER, which contributes to an ultralow overpotential (η = 28 mV at 10 mA cm⁻²) and a small Tafel slope of 37 mV dec⁻¹. More importantly, benefiting from the inner stable crystalline P-PtTe₂ nanosheets, limited decay of the performance is observed after chronopotentiometry test. This work reveals the important role of the inherent relationship between structure and activity in PtTe₂ for HER, which may bring another enlightenment for the design of efficient catalysts based on NMDs in the near future.

Fast and sensitive photodetectors are critical in various applications. This study demonstrates efficient charge transfer in vanadium(V)-doped WS₂/Bi₂O₂Se heterostructures via Kelvin probe force microscopy (KPFM) photoluminescence (PL), and Raman spectroscopy. The results indicate that combining V-doped WS₂ with Bi₂O₂Se can enhance the performance of photodetectors via charge transfer modulated ultrathin p–n junctions, resulting in better sensitivity and faster response time.

Abstract

The field of photovoltaics is revolutionized in recent years by the development of two–dimensional (2D) type-II heterostructures. These heterostructures are made up of two different materials with different electronic properties, which allows for the capture of a broader spectrum of solar energy than traditional photovoltaic devices. In this study, the potential of vanadium (V)-doped WS₂ is investigated, hereafter labeled V-WS₂, in combination with air-stable Bi₂O₂Se for use in high-performance photovoltaic devices. Various techniques are used to confirm the charge transfer of these heterostructures, including photoluminescence (PL) and Raman spectroscopy, along with Kelvin probe force microscopy (KPFM). The results show that the PL is quenched by 40%, 95%, and 97% for WS₂/Bi₂O₂Se, 0.4 at.% V-WS₂/Bi₂O₂Se, and 2 at.% V-WS₂/Bi₂O₂Se, respectively, indicating a superior charge transfer in V-WS₂/Bi₂O₂Se compared to pristine WS₂/Bi₂O₂Se. The exciton binding energies for WS₂/Bi₂O₂Se, 0.4 at.% V-WS₂/Bi₂O₂Se and 2 at.% V-WS₂/Bi₂O₂Se heterostructures are estimated to be ≈130, 100, and 80 meV, respectively, which is much lower than that for monolayer WS₂. These findings confirm that by incorporating V-doped WS₂, charge transfer in WS₂/Bi₂O₂Se heterostructures can be tuned, providing a novel light-harvesting technique for the development of the next generation of photovoltaic devices based on V-doped transition metal dichalcogenides (TMDCs)/Bi₂O₂Se.

2D MoS₂ Nanosheets

MoS₂ nanosheets accumulate Fe²⁺ in lysosomes by promoting NCOA4-dependent ferritinophagy. Fe²⁺ leaks from the damaged lysosomes into the cytoplasm, resulting in ferroptosis. This has important implications for elucidating the toxicity of 2D nanoparticles and determining their medical applications. More details can be found in article number 2208063 by Wei Jiang and co-workers.

Nature Chemistry, Published online: 14 June 2023; doi:10.1038/s41557-023-01269-z

Low-coordinate lanthanide complexes with strong magnetic anisotropy could afford high-performance single-molecule magnets (SMMs) but are challenging to synthesize. Now, through ligand design, a near-linear pseudo-two-coordinate Yb(iii) complex that exhibits slow magnetic relaxation is reported. The complex has a large total splitting of the ground-state manifold, arising from the crystal field imposed by the ligands.

Nature, Published online: 14 June 2023; doi:10.1038/s41586-023-06082-9

We discovered that liquid metal endowing negative mixing enthalpy with other elements could provide a stable thermodynamic condition and act as a desirable dynamic mixing reservoir, realizing the synthesis of high-entropy alloy nanoparticles.

Nature, Published online: 14 June 2023; doi:10.1038/s41586-023-06289-w

Signatures of Fractional Quantum Anomalous Hall States in Twisted MoTe₂

Optoelectronic vision and synaptic devices can help overcome high energy requirements of computation and enable miniaturised, precise, real-time vision systems. Herein, atomically thin layers of Sb doped In₂O₃ are utilised as ultraviolet-active optoelectronic synapses with recognition and prolonged memory capabilities. The material is devised into an imaging array of photo-active pixels capable of pattern recognition and memorization at low power with very few training cycles.

Abstract

Miniaturization and energy consumption by computational systems remain major challenges to address. Optoelectronics based synaptic and light sensing provide an exciting platform for neuromorphic processing and vision applications offering several advantages. It is highly desirable to achieve single-element image sensors that allow reception of information and execution of in-memory computing processes while maintaining memory for much longer durations without the need for frequent electrical or optical rehearsals. In this work, ultra-thin (<3 nm) doped indium oxide (In₂O₃) layers are engineered to demonstrate a monolithic two-terminal ultraviolet (UV) sensing and processing system with long optical state retention operating at 50 mV. This endows features of several conductance states within the persistent photocurrent window that are harnessed to show learning capabilities and significantly reduce the number of rehearsals. The atomically thin sheets are implemented as a focal plane array (FPA) for UV spectrum based proof-of-concept vision system capable of pattern recognition and memorization required for imaging and detection applications. This integrated light sensing and memory system is deployed to illustrate capabilities for real-time, in-sensor memorization, and recognition tasks. This study provides an important template to engineer miniaturized and low operating voltage neuromorphic platforms across the light spectrum based on application demand.

Nature Electronics, Published online: 12 June 2023; doi:10.1038/s41928-023-00975-3

Antiferromagnetism of the IrMn layer in Pt/IrMn/CoFeB/MgO/CoFeB three-terminal magnetic tunnel junctions can be electrically detected using tunnelling magnetoresistance and controlled by a spin–orbit torque generated by a 0.8 ns current pulse applied across the heavy-metal platinum layer.

The first sub-ps (≈600 fs) magnetization process in a ferromagnetic quantum well is successfully demonstrated, which utilizes the high carrier coherency and a rapid photo-Demba field effect, using pump-and-probe measurements with an X-ray free-electron laser. This hopefully opens a new way to ultrafast magnetic storage and information processing.

Abstract

Strong spin-charge interactions in several ferromagnets are expected to lead to subpicosecond (sub-ps) magnetization of the magnetic materials through control of the carrier characteristics via electrical means, which is essential for ultrafast spin-based electronic devices. Thus far, ultrafast control of magnetization has been realized by optically pumping a large number of carriers into the d or f orbitals of a ferromagnet; however, it is extremely challenging to implement by electrical gating. This work demonstrates a new method for sub-ps magnetization manipulation called wavefunction engineering, in which only the spatial distribution (wavefunction) of s (or p) electrons is controlled and no change is required in the total carrier density. Using a ferromagnetic semiconductor (FMS) (In,Fe)As quantum well (QW), instant enhancement, as fast as 600 fs, of the magnetization is observed upon irradiating a femtosecond (fs) laser pulse. Theoretical analysis shows that the instant enhancement of the magnetization is induced when the 2D electron wavefunctions (WFs) in the FMS QW are rapidly moved by a photo-Dember electric field formed by an asymmetric distribution of the photocarriers. Because this WF engineering method can be equivalently implemented by applying a gate electric field, these results open a new way to realize ultrafast magnetic storage and spin-based information processing in present electronic systems.

Flexible IR Imaging Photodetectors

In article number 2300159, Jinzhong Wang, Shiyong Gao, and co-workers, successfully prepared, a large-area freestanding Bi₂S₃ nanofibrous membrane (NFM) with high flexibility, which is self-assembled from ultralong Bi₂S₃ nanowires. The flexible photodetector based on the as-prepared Bi₂S₃ NFM exhibits high responsivity, fast response, excellent stability and splendent imaging capability under both flat and bent state. The as-prepared Bi₂S₃ NFM has great potential in flexible and wearable optoelectronic devices.

Hydrogels

In article number 2213382, Soo-Jin Park, Insik In, Dong-Yeun Koh, Albert S. Lee, and co-workers propose, catechol-functionalized poly(vinyl alcohol)-based hydrogel to inhibit the oxidation of MXene nanofiller while maintaining excellent mechanical and electrical properties suitable for strain sensors. Sufficient interaction of hydrophobic catechol groups with the MXene surface reduces the oxidation-accessible sites in the MXene for reaction with water and eventually suppresses the oxidation of MXene in the hydrogel.

Interlayer lattice and polarization coupling are explored for bilayers of in-plane-polarized ferroelectric Pb_1−xSr_xTiO₃. The cross-interface coupling can induce effects analogous to exchange bias in magnetism in the form of shifted hysteresis loops. In turn, such effects can be controlled via film thickness and chemistry to produce exotic effects including multistate polarization, exchange-spring-like function, and both coercivity softening and hardening.

Abstract

Interlayer coupling in materials, such as exchange interactions at the interface between an antiferromagnet and a ferromagnet, can produce exotic phenomena not present in the parent materials. While such interfacial coupling in magnetic systems is widely studied, there is considerably less work on analogous electric counterparts (i.e., akin to electric “exchange-bias-like” or “exchange-spring-like” interactions between two polar materials) despite the likelihood that such effects can also engender new features associated with anisotropic electric dipole alignment. Here, electric analogs of such exchange interactions are reported, and their physical origins are explained for bilayers of in-plane polarized Pb_1−xSr_xTiO₃ ferroelectrics. Variation of the strontium content and thickness of the layers provides for deterministic control over the switching properties of the bilayer system resulting in phenomena analogous to an exchange-spring interaction and, leveraging added control of these interactions with an electric field, the ability to realize multistate-memory function. Such observations not only hold technological promise for ferroelectrics and multiferroics but also extend the similarities between ferromagnetic and ferroelectric materials to include the manifestation of exchange-interaction-like phenomena.

Nature Communications, Published online: 10 June 2023; doi:10.1038/s41467-023-38556-9

In this Comment, the authors discuss the current status, the challenges, and potential technological impact of exciton transport in transition metal dichalcogenide (TMD) monolayers, lateral and vertical heterostructures as well as moiré excitons in twisted TMD heterostacks.

Nature Electronics, Published online: 08 June 2023; doi:10.1038/s41928-023-00971-7

Arrays of thin-film transistors can be fabricated on the 5-inch wafer scale using solution-based processing of molybdenum disulfide and sodium-embedded alumina inks for the semiconductor and gate dielectric, respectively, yielding devices with room-temperature mobilities of up to 80 cm2 V−1 s−1.

The epitaxial growth of the high-entropy alloy CoCrFeNi on MgO(100) by DC magnetron sputtering is demonstrated. The surface reconstruction and electronic band structure of the CoCrFeNi(100) surface is investigated by low-energy electron diffraction and angle-resolved photoelectron spectroscopy, demonstrating the potential of epitaxial films for fundamental studies of low-index HEA surfaces.

Abstract

High-entropy alloys (HEAs) with their almost limitless number of possible compositions have raised widespread attention in material science. Next to wear and corrosion resistive coatings, their application as tunable electrocatalysts has recently moved into the focus. On the other hand, fundamental properties of HEA surfaces like atomic and electronic structure, surface segregation and diffusion as well as adsorption on HEA surfaces are barely explored. The lack of research is caused by the limited availability of single-crystalline samples. In the present work, the epitaxial growth of face centered cubic (fcc) CoCrFeNi films on MgO(100) is reported. Their characterization by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) demonstrates that the layers with a homogeneous and close to equimolar elemental composition are oriented in [100] direction and aligned with the substrate to which they form an abrupt interface. X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and angle-resolved photoelectron spectroscopy are employed to study chemical composition and atomic and electronic structure of CoCrFeNi(100). It is demonstrated that epitaxially grown HEA films have the potential to fill the sample gap, allowing for fundamental studies of properties of and processes on well-defined HEA surfaces over the full compositional space.

This review summarizes the recent progress in chemical vapor deposition syntheses of wafer-scale uniform monolayer or few-layer MX₂ polycrystalline films through designing homogeneous supply of metal-containing precursors, and the preparation of monolayer MX₂ single crystals through engineering the surface textures of growth substrates. The devices/circuits applications of as-achieved MX₂ wafers for logic operation, data storage, and image capturing/processing are also highlighted.

Abstract

2D semiconducting transition metal dichalcogenides (TMDCs), most with a formula of MX₂ (M=Mo, W; X=S, Se, etc.), have emerged as promising channel materials for next-generation integrated circuits, considering their dangling-bond-free surfaces, moderate bandgaps, relatively high carrier mobilities, etc. Wafer-scale preparation of 2D MX₂ films holds fundamental significance for realizing their applications. Chemical vapor deposition (CVD) is recognized as the most promising method for preparing electronic-grade 2D MX₂ films. This review hereby summarizes the recent progress in CVD syntheses of wafer-scale 2D MX₂ films and their applications in logic operations, data storage, and image capturing/processing related fields. The first part focuses on the wafer-scale syntheses of 2D MX₂ films through designing homogeneous metal precursor supply routes (e.g., precoating soluble precursor, feeding gaseous precursor, designing independent multisource supply or face-to-face metal precursor supply routes). The second part highlights the epitaxial growth of monolayer MX₂ single crystals on single-crystal Au substrates and well-designed sapphire substrates. The third part introduces various functional device/circuit related applications of CVD-derived 2D MX₂ wafers. Finally, challenges and prospects are discussed from the viewpoints of the controlled synthesis, reliable characterization, and damage-free transfer of 2D MX₂, as well as the fabrication and integration of high-performance devices.

Nature Nanotechnology, Published online: 05 June 2023; doi:10.1038/s41565-023-01405-3

A laser printing approach generates physical unclonable fluorescent patterns, made from simple sugar. These environmentally friendly and ultraviolet-stable materials can be applied as anti-counterfeiting labels.

Scientists are intrigued by the intercalation chemistry of layered hydroxides (LHs) and its impact on structure, composition, and size of LHs. One comprehensive review can be a helpful resource for scientists regarding the progress of LHs intercalated with guest anions. However, there is currently a lack of systematic information about this topic. In this review, recent developments in LHs intercalated with guest anions, including composition and structure, synthesis methods, analytical techniques, and intercalation mechanisms are summarized.

Abstract

Since the intercalation of anions into layered hydroxides (LHs) has a great impact not only on their nucleation and growth but also on their structure, composition, and size, the intercalation chemistry of LHs has aroused the strong interest of researchers. However, the progress in the fundamental understanding of LHs intercalated with guest anions have not been paralleled by a concomitant development of the preparation and performance improvement of such materials. Considering the guidance of a timely in-depth review for scientists in this area, a systematic introduction about the development that is made on the above-mentioned issues is highly needed but yet missing so far. Herein, recent advances in understanding the chemical composition and structure of LHs intercalated with guest anions are systematically summarized. Meanwhile, typical and emerging bottom-up synthesis methods of LHs intercalated with anions are reviewed, and the potential impact of external reaction parameters on the intercalation of anions into LHs are discussed . Besides, different analytical characterization techniques employed in the examination of guest anion-intercalated LHs are deliberated upon. Finally, although progress is slow in exploring the intercalation mechanism, as many examples as possible are included in this review and inferred the possible intercalation mechanism.

3D magnetic soft robots are demonstrated through a combination of photocurable magnetic elastomer design and fiber-based fabrication of helical actuators. Fiber-based robots are engineered for crawling and walking motion under unidirectional fields applied via stationary electromagnets. The versatile design and straightforward control pave the way for applications of magnetic fiber-based robots in spatially constrained environments.

Abstract

Broad adoption of magnetic soft robotics is hampered by the sophisticated field paradigms for their manipulation and the complexities in controlling multiple devices. Furthermore, high-throughput fabrication of such devices across spatial scales remains challenging. Here, advances in fiber-based actuators and magnetic elastomer composites are leveraged to create 3D magnetic soft robots controlled by unidirectional fields. Thermally drawn elastomeric fibers are instrumented with a magnetic composite synthesized to withstand strains exceeding 600%. A combination of strain and magnetization engineering in these fibers enables programming of 3D robots capable of crawling or walking in magnetic fields orthogonal to the plane of motion. Magnetic robots act as cargo carriers, and multiple robots can be controlled simultaneously and in opposing directions using a single stationary electromagnet. The scalable approach to fabrication and control of magnetic soft robots invites their future applications in constrained environments where complex fields cannot be readily deployed.

Low thermal conductivity is highly desired in thermal insulation, data storage, thermoelectric, and spintronic devices. Low thermal conductivity is typically achieved in disordered materials. Herein, this study demonstrates intrinsic superior low thermal conductivity in van der Waals ferromagnet Cr₂Si₂Te₆ single crystals. The low thermal conductivity in Cr₂Si₂Te₆ is realized via spin-phonon scattering, which can advance the spintronic device applications.

Abstract

Layered van der Waals (vdW) magnets are prominent playgrounds for developing magnetoelectric, magneto-optic, and spintronic devices. In spintronics, particularly in spincaloritronic applications, low thermal conductivity (κ) is highly desired. Herein, by combining thermal transport measurements with density functional theory calculations, this study demonstrates low κ down to 1 W m⁻¹ K⁻¹ in a typical vdW ferromagnet Cr₂Si₂Te₆. In the paramagnetic state, development of magnetic fluctuations way above T _c = 33 K strongly reduces κ via spin-phonon scattering, leading to low κ ≈ 1 W m⁻¹ K⁻¹ over a wide temperature range, in comparable to that of amorphous silica. In the magnetically ordered state, emergence of resonant magnon-phonon scattering limits κ below ≈2 W m⁻¹ K⁻¹, which will be three times larger if magnetic scatterings are absent. Application of magnetic fields strongly suppresses the spin-phonon scattering, giving rise to large enhancements of κ. This study's calculations well capture these complex behaviors of κ by taking the temperature- and magnetic-field-dependent spin-phonon scattering into account. Realization of low κ, which is easily tunable by magnetic fields in Cr₂Si₂Te₆, may further promote spincaloritronic applications of vdW magnets. This study's theoretical approach may also provide a generic understanding of spin-phonon scattering, which appears to play important roles in various systems.

Nature Communications, Published online: 02 June 2023; doi:10.1038/s41467-023-38877-9

Bilayer graphene (BLG) is promising for optoelectronic applications due to its tunable bandgap, but its large-area growth on Cu substrates is still challenging. Here, the authors demonstrate the fast synthesis of high-coverage meter-scale BLG on commercial Cu foils by introducing CO2 during the growth.

This review provides a summary and discussion on the recent significant progress of porous 2D materials. The synthesis of these porous 2D materials and their corresponding applications are introduced and discussed, followed by a discussion on the challenges in the porous structure of the materials themself, materials synthesis, and future developments of expanding the applications of porous 2D materials.

Abstract

Two-Dimensional (2D) materials have attracted immense attention in recent years. These materials have found their applications in various fields, such as catalysis, adsorption, energy storage, and sensing, as they exhibit excellent physical, chemical, electronic, photonic, and biological properties. Recently, researchers have focused on constructing porous structures on 2D materials. Various strategies, such as chemical etching and template-based methods, for the development of surface pores are reported, and the porous 2D materials fabricated over the years are used to develop supercapacitors and energy storage devices. Moreover, the lattice structure of the 2D materials can be modulated during the construction of porous structures to develop 2D materials that can be used in various fields such as lattice defects in 2D nanomaterials for enhancing biomedical performances. This review focuses on the recently developed chemical etching, solvent thermal synthesis, microwave combustion, and template methods that are used to fabricate porous 2D materials. The application prospects of the porous 2D materials are summarized. Finally, the key scientific challenges associated with developing porous 2D materials are presented to provide a platform for developing porous 2D materials.

Nature Materials, Published online: 01 June 2023; doi:10.1038/s41563-023-01548-7

Controlling the vapour transport mode with sustained release of precursor species allows for the growth of single-crystalline black phosphorus and black phosphorus–arsenic thin films on the millimetre scale.

Soft electronic devices and robots heal themselves without manual intervention.

Nature, Published online: 31 May 2023; doi:10.1038/d41586-023-01739-x

A protein has been discovered that binds to the lighter members of the rare-earth family of metals more strongly than to the heavier ones — an amazing feat, given the chemical similarities of these elements.