Jing Zhang

Nature Photonics, Published online: 22 August 2022; doi:10.1038/s41566-022-01057-0

An ultrabroadband femtosecond enhancement cavity is developed, using gold-coated mirrors and a wedged-diamond-plate input coupler. Simultaneous enhancement of a 22–40 THz offset-free frequency comb allows cavity-enhanced time-domain spectroscopy of gas mixtures based on electro-optic sampling in the mid-infrared range.

Nature Communications, Published online: 22 August 2022; doi:10.1038/s41467-022-31604-w

Studies of twisted bilayer transition metal dichalcogenides have so far focused only on those containing group-VI metals. Here, the authors predict that twisted bilayers of ZrS2, with the group-IV metal Zr, form an emergent moiré Kagome lattice with a uniquely strong spin-orbit coupling, leading to quantum-anomalous-Hall and fractional-Chern-insulating states.

Nature Materials, Published online: 24 August 2022; doi:10.1038/s41563-022-01338-7

Planar Josephson junctions with Nb electrodes and a composite weak link barrier combining heavy metal Pt and ferrimagnetic Y3Fe5O12 enable a large supercurrent diode effect at 4He fridge temperatures in the absence of an applied magnetic field.

Nature Electronics, Published online: 23 August 2022; doi:10.1038/s41928-022-00831-w

Tailoring heat flow in 2D materials

Nature Physics, Published online: 15 August 2022; doi:10.1038/s41567-022-01700-1

A superconducting diode effect is observed at zero magnetic field in twisted trilayer graphene. This suggests that time-reversal symmetry is intrinsically broken and leads to pairing between electrons with non-zero centre-of-mass momentum.

Nature Materials, Published online: 15 August 2022; doi:10.1038/s41563-022-01329-8

Unlike electron spins, nuclear spins in van der Waals materials remain a largely untapped quantum resource. Here we report the fast coherent control of nuclear spins and strong electron-mediated nuclear–nuclear spin coupling in hexagonal boron nitride.

Nature, Published online: 17 August 2022; doi:10.1038/s41586-022-04977-7

Multidimensional time- and angle-resolved photoelectron spectroscopy is used to determine the interlayer exciton formation process, reveal a direct hallmark of the superlattice moiré modification, and reconstruct the real-space wavefunction distribution.

Functional inks based on two-dimensional (2D) materials have potential application in building new and commercially viable photonic devices via different printing techniques. Printed photonics using 2D material-based inks brings together the unique optical properties of 2D materials and different printing techniques in the fabrication of photonic devices that can revolutionize telecommunication, information technology, and computing. Understanding the need for a comprehensive guide for researchers using 2D material-based inks of printed photonics, we have compiled the essential concepts governing this field in this review. We begin with a discussion of the optical properties of 2D materials commonly used in photonic applications. The general properties of functional inks, and commonly used substrates compatible for printed photonics application are also listed. The printing methods commonly used in 2D material-based photonic device fabrication are explained, with a focus on inkjet printing, the most demonstrated method in this field. We have discussed a few examples of photonic devices printed with 2D material-based functional inks. Finally, our perspective on 2D materials that have the potential to improve the performance of photonic devices as well as build devices with new functionalities are listed.

Twisted 2D bilayer materials are created by artificial stacking of two monolayer crystal networks of 2D materials with a desired twisting angle θ. The material forms a moiré superlattice due to the periodicity of both top and bottom layer crystal structure. The optical properties are modified by lattice reconstruction and phonon renormalization, which makes optical spectroscopy an ideal characterization tool to study novel physics phenomena. Here, we report a Raman investigation on a full period of the twisted bilayer (tB) WSe2 moiré superlattice (i.e. 0 60∘). We observe that the intensity ratio of two Raman peaks, and correlates with the evolution of the moiré period. The Raman intensity ratio as a function of twisting angle follows an exponential profile matching the moiré period with two local maxima at 0∘ and 60∘ and a minimum at 30∘. Using a series of temperature-dependent Raman and photoluminescence measurements as well as ab initio calculations, the intensity ratio is explained as a signature of lattice dynamics in tB WSe2 moiré superlattices. By further exploring different material combinations of twisted hetero-bilayers, the results are extended for all kinds of Mo- and W-based transition metal dichalcogenides.

Laser-induced graphene (LIG) is an emerging porous material produced when irradiating a laser beam on certain carbon materials. This in-depth review highlights the recent advances in LIG research, including the mechanism of LIG formation, typical lasers in LIG fabrication, effects of lasing parameters on LIG structures and properties, and applications of LIG in flexible electronics.

Abstract

Laser-induced graphene (LIG) is a newly emerging 3D porous material produced when irradiating a laser beam on certain carbon materials. LIG exhibits high porosity, excellent electrical conductivity, and good mechanical flexibility. Predesigned LIG patterns can be directly fabricated on diverse carbon materials with controllable microstructure, surface property, electrical conductivity, chemical composition, and heteroatom doping. This selective, low-cost, chemical-free, and maskless patterning technology minimizes the usage of raw materials, diminishes the environmental impact, and enables a wide range of applications ranging from academia to industry. In this review, the recent developments in 3D porous LIG are comprehensively summarized. The mechanism of LIG formation is first introduced with a focus on laser-material interactions and material transformations during laser irradiation. The effects of laser types, fabrication parameters, and lasing environment on LIG structures and properties are thoroughly discussed. The potentials of LIG for advanced applications including biosensors, physical sensors, supercapacitors, batteries, triboelectric nanogenerators, and so on are also highlighted. Finally, current challenges and future prospects of LIG research are discussed.

The large-scale industrial applications of graphene highly depend on its mass production with efficiency (high-yield, time-saving, and low-cost) and controllability (high-quality, safe, and environmentally friendly). The usage of bubbling as a new tool makes a big difference in multiple aspects of graphene production. Here, the mass production of graphene with the assistance of bubbles is summarized and discussed.

Abstract

The large-scale industrial applications of graphene highly depend on its mass production with efficiency (high-yield, time-saving, and low-cost) and controllability (high-quality, safe, and environmentally friendly). However, this requirement can hardly be satisfied by incumbent chemical exfoliation methods exploiting liquid–solid interactions. Recently, many studies have demonstrated that the usage of bubbling as a new tool makes a big difference in multiple aspects of graphene production. Benefiting from their unique properties, the bubbles can be employed as the driving force to cleave graphite layers for graphene preparation or as the favorite interface for graphene growth at a high temperature. Therefore, the bubble-mediated technique represents a new strategy promising to achieve efficient and controllable preparation of graphene. Here, the formation and evolution of bubbles in liquid media are first analyzed. Then, two routes including “top-down” and “bottom-up” toward mass production of graphene with the assistance of bubbles are summarized and discussed. This review sheds light on the introduction of gas to realize the mass production of graphene for the development of graphene's applications on large scale.

This study demonstrate simultaneous manipulation of microrobots motion and targeted antimicrobial activity. The peptide modified microrobots exhibit excellent selectivity and antimicrobial performance against methicillin-resistant Staphylococcus aureus (MRSA) biofilm eradication. It shows a general strategy for targeted delivery of microrobots and boosting of antimicrobial effect against resistant MRSA biofilms.

Abstract

Bacterial biofilms are composed of a consortium of bacteria that communicate with each other through quorum sensing. Therefore, bacteria can form an extracellular matrix, which is a mucus composed of exopolysaccharides, peptidoglycans, and extracellular DNA, through these communication molecules. The matrix protects the community of bacteria from the adverse effects of the external environment, including antibiotics, biocides, and eradicating agents. Self-propelled functional microrobots offer great promises in the biomedical field. The self-propelled microrobots represent an innovative platform in microrobotic research, aiming to have an important role in the biomedical field. One of the potential applications is removal of bacterial biofilms. Herein, the specific design of multifunctional microrobots is demonstrated using antimicrobial-designed peptides for eradication of methicillin-resistant Staphylococcus aureus (MRSA)-produced biofilms. The designed microrobots can perform various tasks, including autonomous navigation toward bacterial cells, mechanical entry into bacterial biofilms, and blockage of the replication of bacterial DNA by indolicidin peptides. The implemented design extends the microrobot applications not only to the removal of biological aggregates but also to the delivery and release of drugs or even target manipulation, demonstrating their great potential for use in biomedical research.

The use of Ti₃C₂T _x as an electrode to build Ti₃C₂T _x -MoS₂ vdWs contact can improve the performance of the 2D field effect transistors, including alleviating the Fermi level pinning and decreasing the Schottky barrier height to 121 eV. Moreover, a simple and time-saving technique has been proposed to tune the work function of Ti₃C₂T _X electrode in the range of 4.33 to 5.32 eV.

Abstract

The quality of the contact between source/drain electrodes and 2D transition metal dichalcogenides plays a decisive role in improving transistor performance. Understanding the mechanisms of Fermi level pinning (FLP) and finding out the strategies to solve FLP problems can further promote the development of 2D electronics. In this study, the suppressing effect of MXene on FLP in MoS₂ transistors by using Ti₃C₂T _x as an electrode to build a Ti₃C₂T _x -MoS₂ heterostructure is systematically studied. A simple and time-saving ultraviolet ozone technique to tune the work function of the Ti₃C₂T _x electrode in the range of 4.33–5.32 eV is proposed, and a low Schottky barrier height of 121 meV is achieved. The van der Waals contact between Ti₃C₂T _x and MoS₂ can alleviate the FLP effectively, and the pinning factor can be greatly optimized from 0.28 (metal electrode) to 0.87 (MXene electrode). This study can pave the way for extensive use of MXene and provide a new strategy to eliminate the negative effects of FLP in 2D materials-based electronic devices.

A systematic understanding of phase distribution mechanism in 2D perovskite films is critical for the development of high-performance 2D perovskite solar cells (PSCs). A systematic understanding of phase distribution and guidelines on 2D perovskite phase regulation is provided, aiming for establishing a general manual for efficient charge-carrier transport design and high-performance PSC fabrication.

Abstract

Solution-processed 2D perovskite films generally contain mixed quantum wells (QWs) with multiple well width distribution, which seriously weakens the charge transfer. To achieve regulation of the QW width, strategies to optimize the crystallization dynamics of 2D perovskite films are urgently needed. In this review, systematic summary on QW distribution and guidelines for 2D perovskite phase regulation is provided, aiming to establish a general manual for preparing efficient 2D perovskite solar cells (PSCs). The factors affecting the distribution of multiple-QWs in 2D perovskite films, including component engineering, additive engineering, process optimization, are first generalized. Then an extensive review of these factors that are widely used to reconstruct 2D perovskite crystallization process is conducted. Leveraging these insights, the effect of QWs distributions on 2D PSCs properties is also summarized. Similarly, considering the crystallization kinetics and device performance, the QWs width control of 2D perovskite films from the aspects of ligand engineering, precursor design, and fabrication optimization, is rationalized. Finally, an outlook on how to realize ordered QWs distribution in perovskite films for efficient 2D PSCs is proposed.

Quantum Conductance

In article number 2201248, Gianluca Milano, Ilia Valov, and co-workers review the state-of-the-art of quantum conductance effects in memristive devices. Besides analyzing fundamental physicochemical phenomena and electronic ballistic transport in nanofilaments, recent developments in experimental observation of quantum effects in memristive devices and related challenges are discussed. Representing suitable platforms for investigating quantum phenomena at room temperature, future perspectives of memristive devices in quantum and neuromorphic systems are envisioned.

A novel metal-mirror-enhanced n–p–n van der Waals heterostructure is designed. The device exhibits excellent performance including high blackbody photoresponsivity up to 0.77 A W⁻¹, high specific detectivity of 8.61 × 10¹⁰ cm Hz^1/2 W⁻¹ under blackbody radiation, and fast response speed of ≈4 µs.

Abstract

Room-temperature-operating highly sensitive mid-wavelength infrared (MWIR) photodetectors are utilized in a large number of important applications, including night vision, communications, and optical radar. Many previous studies have demonstrated uncooled MWIR photodetectors using 2D narrow-bandgap semiconductors. To date, most of these works have utilized atomically thin flakes, simple van der Waals (vdW) heterostructures, or atomically thin p–n junctions as absorbers, which have difficulty in meeting the requirements for state-of-the-art MWIR photodetectors with a blackbody response. Here, a fully depleted self-aligned MoS₂-BP-MoS₂ vdW heterostructure sandwiched between two electrodes is reported. This new type of photodetector exhibits competitive performance, including a high blackbody peak photoresponsivity up to 0.77 A W⁻¹ and low noise-equivalent power of 2.0 × 10⁻¹⁴ W Hz^−1/2, in the MWIR region. A peak specific detectivity of 8.61 × 10¹⁰ cm Hz^1/2 W⁻¹ under blackbody radiation is achieved at room temperature in the MWIR region. Importantly, the effective detection range of the device is twice that of state-of-the-art MWIR photodetectors. Furthermore, the device presents an ultrafast response of ≈4 µs both in the visible and short-wavelength infrared bands. These results provide an ideal platform for realizing broadband and highly sensitive room-temperature MWIR photodetectors.

Carbon suboxide is a molecule spontaneously polymerizing into conjugated ladder oligomers composed of carbon and oxygen atoms only, and named “red carbon.” Herein, this partially forgotten chemistry is brought back to the attention of the community of covalent semiconductors. As-synthesized red carbon generates superoxide species upon light irradiation, acting as an efficient photocatalyst, with performance superior to the state-of-the-art carbon nitrides.

Abstract

Carbon suboxide (C₃O₂) is a unique molecule able to polymerize spontaneously into highly conjugated light-absorbing structures at temperatures as low as 0 °C. Despite obvious advantages, little is known about the nature and the functional properties of this carbonaceous material. In this work, the aim is to bring “red carbon,” a forgotten polymeric semiconductor, back to the community's attention. A solution polymerization process is adapted to simplify the synthesis and control the structure. This allows one to obtain this crystalline covalent material at low temperatures. Both spectroscopic and elemental analyses support the chemical structure represented as conjugated ladder polypyrone ribbons. Density functional theory calculations suggest a crystalline structure of AB stacks of polypyrone ribbons and identify the material as a direct bandgap semiconductor with a medium bandgap that is further confirmed by optical analysis. The material shows promising photocatalytic performance using blue light. Moreover, the simple condensation–aromatization route described here allows the straightforward fabrication of conjugated ladder polymers and can be inspiring for the synthesis of carbonaceous materials at low temperatures in general.

MoSe₂–VSe₂–NbSe₂ ternary alloy nanosheets are synthesized via a colloidal reaction. Ternary alloying produces a miscible phase over a wide range. Compared to each binary alloy, the ternary alloys display higher electrocatalytic activity toward the hydrogen evolution reaction (HER) in an acidic electrolyte. Spin-polarized density functional theory (DFT) calculations consistently predict the homogenous atomic distributions and support that ternary alloying greatly enhances the HER performance.

Abstract

Alloying of transition metal dichalcogenides (TMDs) is a pioneering method for engineering electronic structures with expanded applications. In this study, MoSe₂–VSe₂–NbSe₂ ternary alloy nanosheets are synthesized via a colloidal reaction. The composition is successfully tuned over a wide range to adjust the 2H–1T phase transition. The alloy nanosheets consist of miscible atomic structures at all compositions, which is distinct from immiscible binary alloys. Compared to each binary alloy, the ternary alloys display higher electrocatalytic activity toward the hydrogen evolution reaction (HER) in an acidic electrolyte. The HER performance exhibits a volcano-type composition dependence, which is correlated with the experimental d-band center (ε_d). Spin-polarized density functional theory (DFT) calculations consistently predict the homogenous atomic distributions. The Gibbs free energy of H adsorption (ΔG _H*) and the activation barrier (E _a) support that miscible ternary alloying greatly enhances the HER performance.

Nature Communications, Published online: 12 August 2022; doi:10.1038/s41467-022-32498-4

Here, the authors report tunable luminescence from a single lanthanide ion upon changing excitation conditions through co-doping an energy-modulator ion, thus adjusting the photon transition process of the lanthanide activator ion. Optical encryption has also been demonstrated as an application of this universal strategy.

Nature Communications, Published online: 19 August 2022; doi:10.1038/s41467-022-32292-2

2D semiconductors offer a promising platform for the realization of compact and CMOS-compatible optoelectronic components. Here, the authors report the realization of light-emitting diodes based on 2D WSe2 integrated with a planar cavity, showing the electrical control of the emission angle and polarization at room temperature.

Nature Nanotechnology, Published online: 16 August 2022; doi:10.1038/s41565-022-01192-3

Suspensions of 2D hexagonal boron nitride show an anomalously large specific Cotton–Mouton coefficient, enabling the fabrication of a magnetically tuneable and stable birefringent optical device. This device serves as a transmissive light modulator with wavelengths entering the ultraviolet (UV)-C region, representing a technological advance in deep-UV modulation.

Nature Nanotechnology, Published online: 18 August 2022; doi:10.1038/s41565-022-01172-7

Heterostructure of graphene and biaxial van der Waals crystal supports a species of plasmon-phonon-polaritons whose isofrequency dispersion contour can be manipulated while experiencing a topological transition.