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Polymorph engineering involves the manipulation of material properties through controlled structural modification and is a candidate technique for creating unique two-dimensional transition metal dichalcogenide (TMDC) nanodevices. Despite its promise, polymorph engineering of magnetic TMDC monolayers has not yet been demonstrated. Here we grow FeSe2 monolayers via molecular beam epitaxy and find that they have great promise for magnetic polymorph engineering. Using scanning tunneling microscopy (STM) and spectroscopy (STS), we find that FeSe2 monolayers predominantly display a 1T' structural polymorph at 5 K. Application of voltage pulses from an STM tip causes a local, reversible transition from the 1T' phase to the 1T phase. Density functional theory calculations suggest that this single-layer structural phase transition is accompanied by a magnetic transition from an antiferromagnetic to a ferromagnetic configuration. These results open new possibilities for creating functional magnetic devices with TMDC monolayers via polymorph engineering.

Layer-by-layer (LbL) assembly of oppositely charged materials has been widely used as an approach to make two-dimensional (2D) nanosheet-based membranes, which often involves 2D nanosheets being alternately deposited with polymer-based polyelectrolytes to obtain an electrostabilized nanosheet-polymer structure. In this study, we hypothesized that using 2D nanosheets with matching physical properties as both polyanions and polycations may result in a more ordered nanostructure with better stability than a nanosheet-polymer structure. To compare the differences between nanosheet-nanosheet vs nanosheet-polymer structures, we assembled negatively charged molybdenum disulfide nanosheets (MoS2) with either positively charged graphene oxide (PrGO) nanosheets or positively charged polymer (PDDA). Using combined measurements by ellipsometer and quartz crystal microbalance with dissipation, we discovered that the swelling of MoS2-PrGO in ionic solutions was 60% lower than that of MoS2-PDDA membranes. Meanwhile, the MoS2-PrGO membrane retained its permeability upon drying, whereas the permeability of MoS2-PDDA decreased by 40% due to the restacking of MoS2. Overall, the MoS2-PrGO membrane demonstrated a better filtration performance. Additionally, our X-ray photoelectron spectroscopy results and analysis on layer density revealed a clearer transition in material composition during the LbL synthesis of MoS2-PrGO membranes, and the X-ray diffraction pattern suggested its resemblance to an ordered, layer-stacked structure. In conclusion, the MoS2-PrGO membrane made with nanosheets with matching size, shape, and charge density exhibited a much more aligned stacking structure, resulting in reduced membrane swelling under high salinity solutions, controlled restacking, and improved separation performance.

Photocatalytic water splitting (PWS) is a promising approach for sustainable hydrogen production, which can potentially address the growing energy demands and environmental concerns. In this paper, we designed a family of 18 two-dimensional materials, AX 2 B 3 (A = K, Rb, Cs; X = Ni, Pd, Pt; B S, Se), and further investigated their stability, electronic structures and PWS performance. We illustrated that all the materials possess high stability, and exhibit semiconducting characteristics with band-gaps from 0.78 to 2.07 eV. Interestingly, there are 6 Pt-containing materials, KPt 2 S 3 , KPt 2 Se 3 , RbPt 2 S 3 , RbPt 2 Se 3 , CsPt 2 S 3 and CsPt 2 Se 3 , with suitable band-edges to drive hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in the process of PWS. Besides, these 6 candidates can release high PWS activity due to their high electron mobility of ∼103 cm2/Vs, which is significantly higher than that of hole. Moreover, they have strong optical absorption coefficient (∼105 cm−1) covering visible to ultraviolet light, and deliver amazing solar-to-hydrogen efficiencies from 24.57% to 26.72%, which are higher than those of common PWS materials. Ultimately, two-dimensional APt 2 B 3 (A = K, Rb, Cs; B S, Se) are suitable candidates for PWS application under sun light. [Display omitted] • Two-dimensional AX 2 B 3 (A = K, Rb, Cs; X = Ni, Pd, Pt; B = S, Se), are revealed to possess high stability, and show band-gaps from 0.78 to 2.07 eV. • The 6 Pt-containing materials have suitable band-edges to drive photocatalytic water splitting. • They have strong optical absorption coefficient of 105 cm−1), and deliver amazing solar-to-hydrogen efficiencies from 24.57% to 26.72%. [ABSTRACT FROM AUTHOR]

In the field of hydrogen storage and transportation, the development of hydrogen barrier coatings with excellent hydrogen permeation resistance is crucial for reducing hydrogen-induced damage caused by hydrogen leakage and hydrogen embrittlement. In recent years, benefiting from its excellent hydrogen barrier performance and wide application range, polymer-based hydrogen barrier composite coatings, membrane and films are expected to become an essential technology in promoting efficient hydrogen storage and transportation in the future. Primarily, starting from the material design of the composite systems, commonly applied gas barrier polymers and two-dimensional nanofillers are explicitly outlined. The detailed data of hydrogen barrier performance as well as advantages and disadvantages of their applications in this field are analysed and highlighted, and strategies are conceived and proposed to optimize their hydrogen barrier performance. Then, the major factors influencing the performance of hydrogen barrier composite system are put forward, providing ideas for strengthening the performance of hydrogen barrier composite from diverse perspectives and exploring failure mechanisms. Finally, a systematic classification overview of the currently researched hydrogen barrier composite system has been provided, and based on their different categories, the development trend of how to achieve large-scale applications of these coatings in the future is discussed. The H 2 barrier composite membrane, coating & film exhibit tremendous application prospects in abundant hydrogen-related fields. [Display omitted] • The H 2 barrier composites for efficient H 2 transportation and storage are discussed. • Major gas barrier polymers are explicitly summarized. • Common two-dimensional gas barrier fillers are outlined and compared. • Future development and optimization of H 2 barrier composites are envisioned. [ABSTRACT FROM AUTHOR]

Nowadays, Alkaline earth metal halofluoride, as part of layered materials, have drawn considerable interest for applications in optoelectronic devices and sensors, benefiting from wide bandgap properties. In this work, the monolayer alkaline earth metal halofluoride XYF (X = Ca/Sr/Ba, Y = Cl/Br/I) were investigated based on first-principles calculations. These monolayers can be exfoliated with energies comparable to conventional two-dimensional (2D) materials, suggesting their potential for practical applications. Additionally, XYF monolayers all exhibit excellent structural stability, with a maximum elastic modulus ranging from 37.144 to 76.829 N/m, indicating significant flexibility. More strikingly, these materials are characterized as ultra-wide bandgap (UWBG) semiconductors, with direct bandgaps spanning from 5.06 to 7.56 eV using HSE06 functional. Furthermore, exploration was conducted into introducing magnetism by doping of S and P atoms, thereby providing magnetic moments in non-magnetic systems. Our research broadens the spectrum of 2D wide-bandgap materials, and holds promise for their applications in optoelectronics, flexible electronics and spintronics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Large area, 2D β-Ni(OH) 2 , < 3 nm thin nanosheets synthesized at water–air interface. • Device shows 820 mAh.cm−3 capacity with 70% retention after 30,000 cycles. • Device achieved ultrahigh energy density of 0.33 Wh.cm−3 at 275.86 W.cm −3. • β- Ni(OH) 2 shows enhanced OER activity η 10 :308 mV with Tafel value of 42 mV dec-1. • After charge storage & OER, XPS analysis confirms structural stability of the film. Bifunctional electrode materials are highly desirable for meeting increasing global energy demands and mitigating environmental impact. However, improving the atom-efficiency, scalability, and cost-effectiveness of storage systems, as well as optimizing conversion processes to enhance overall energy utilization and sustainability, remains a significant challenge for their application. Herein, we devised an optimized, facile, economic, and scalable synthesis of large area (cm2), ultrathin (∼2.9 ± 0.3 nm) electroactive nanosheet of β-Ni(OH) 2, which acted as bifunctional electrode material for charge storage and oxygen evolution reaction (OER). The β-Ni(OH) 2 nanosheet electrode shows the volumetric capacity of 2.82 Ah.cm−3(0.82 µAh.cm−2) at the current density of 0.2 mA.cm −2. The device shows a high capacity of 820 mAh.cm−3 with an ultrahigh volumetric energy density of 0.33 Wh.cm−3 at 275.86 W.cm −3 along with promising stability (30,000 cycles). Furthermore, the OER activity of ultrathin β-Ni(OH) 2 exhibits an overpotential (η 10) of 308 mV and a Tafel value of 42 mV dec-1 suggesting fast reaction kinetics. The mechanistic studies are enlightened through density functional theory (DFT), which reveals that additional electronic states near the Fermi level enhance activity for both capacitance and OER. [ABSTRACT FROM AUTHOR]

We present the results of gas sensing using the fluctuation-enhanced sensing method in selected two-dimensional materials (2DMs). We claim that gas sensing selectivity can be improved further by considering semiconducting two-dimensional materials doped by noble metal nanoparticles. The 2DMs’ structures exhibit some imperfections defined by their structure, occurring repeatedly there. These imperfections are adsorption–desorption centers responsible for gas-sensing properties and generating flicker noise of various intensities. We consider how these imperfections can be modulated and utilized for fluctuations-enhanced gas sensing. We propose the decoration of 2DMs by noble metal nanoparticles that impact flicker noise. Additionally, we consider utilizing localized surface plasmonic resonance induced by irradiation at selected wavelengths. [ABSTRACT FROM AUTHOR]

Metal ion intercalation into van der Waals gaps of layered materials is vital for large-scale electrochemical energy storage. Transition-metal sulfides, ABS4 (where A and B represent Zr, Hf, and Ti as monolayers as anodes), are examined as lithium and sodium ion storage. Our study reveals that these monolayers offer exceptional performance for ion storage. The low diffusion barriers enable efficient lithium bonding and rapid separation while all ABS4 phases remain semiconducting before lithiation and transition to metallic states, ensuring excellent electrical conductivity. Notably, the monolayers demonstrate impressive ion capacities: 1639, 1202, and 1119 mAh/g for Li-ions, and 1093, 801, and 671 mAh/g for Na-ions in ZrTiS4, HfTiS4, and HfZrS4, respectively. Average voltages are 1.16 V, 0.9 V, and 0.94 V for Li-ions and 1.17 V, 1.02 V, and 0.94 V for Na-ions across these materials. Additionally, low migration energy barriers of 0.231 eV, 0.233 eV, and 0.238 eV for Li and 0.135 eV, 0.136 eV, and 0.147 eV for Na make ABS4 monolayers highly attractive for battery applications. These findings underscore the potential of monolayer ABS4 as a superior electrode material, combining high adsorption energy, low diffusion barriers, low voltage, high specific capacity, and outstanding electrical conductivity. [ABSTRACT FROM AUTHOR]

For metal-free low-dimensional ferromagnetic materials, a hopeful candidate for next-generation spintronic devices, investigating their magnetic mechanisms and exploring effective ways to regulate their magnetic properties are crucial for advancing their applications. Our work systematically investigated the origin of magnetism of a graphitic carbon nitride (Pca21 C4N3) monolayer based on the analysis on the partial electronic density of states. The magnetic moment of the Pca21 C4N3 originates from the spin-split of the 2pz orbit from special carbon (C) atoms and 2p orbit from N atoms around the Fermi energy, which was caused by the lone pair electrons in nitrogen (N) atoms. Notably, the magnetic moment of the Pca21 C4N3 monolayer could be effectively adjusted by adsorbing nitric oxide (NO) or oxygen (O2) gas molecules. The single magnetic electron from the adsorbed NO pairs with the unpaired electron in the N atom from the substrate, forming a Nsub-Nad bond, which reduces the system's magnetic moment from 4.00 μB to 2.99 μB. Moreover, the NO adsorption decreases the both spin-down and spin-up bandgaps, causing an increase in photoelectrical response efficiency. As for the case of O2 physisorption, it greatly enhances the magnetic moment of the Pca21 C4N3 monolayer from 4.00 μB to 6.00 μB through ferromagnetic coupling. This method of gas adsorption for tuning magnetic moments is reversible, simple, and cost-effective. Our findings reveal the magnetic mechanism of Pca21 C4N3 and its tunable magnetic performance realized by chemisorbing or physisorbing magnetic gas molecules, providing crucial theoretical foundations for the development and utilization of low-dimensional magnetic materials. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have garnered increasing attention due to their unusual properties and significant potential applications in electronic devices. However, the performance of these devices is closely related to the atomic structure of the material, which can be influenced through manipulation and fabrication at the atomic scale. Transmission electron microscopes (TEMs) and scanning TEMs (STEMs) provide an attractive platform for investigating atomic fabrication due to their ability to trigger and monitor structural evolution at the atomic scale using electron beams. Furthermore, the accuracy and consistency of atomic fabrication can be enhanced with an automated approach. In this paper, we briefly introduce the effect of electron beam irradiation and then discuss the atomic structure evolution that it can induced. Subsequently, the use of electron beams for achieving desired structures and patterns in a controllable manner is reviewed. Finally, the challenges and opportunities of atomic fabrication on 2D materials inside an electron microscope are discussed. [ABSTRACT FROM AUTHOR]

The present research utilizes the simple "plug-and-play" strategy to effectively impart layered rare-earth hydroxides with remarkable sensitivity, selectivity, and rapid fluorescence sensing detection ability towards nitroaromatic compounds, employing the excited-state proton transfer fluorescence quenching mechanism. This opens new possibilities for the efficient and accurate detection of toxic and hazardous nitroaromatic compounds and effectively protecting environmental health and public safety. [Display omitted] Convenient, rapid, and accurate detection of nitroaromatic organic toxins and harmful substances is of great significance in research. In the present study, two-dimensional layered rare-earth hydroxides (LYH) were used as ion-exchange matrix materials, and the anionic fluorescent dye molecules (HPTS) were successfully introduced into the LYH structures in situ via a simple and effective "plug-and-play" strategy, which gave the compounds ultra-sensitive fluorescence sensing detection of nitrobenzene, p-nitrotoluene and p-nitrophenol (Fluorescence response time < 1 sec , and the LOD for nitrobenzene, p-nitrophenol and p-nitrotoluene reached an impressive 349 ppb, 22 ppb and 98 ppb, respectively). Combined with theoretical calculations, we elucidated in detail the fluorescence quenching response mechanism of the LYH-HPTS towards nitroaromatic. Additionally, we also constructed fluorescent paper sensor, which effectively transformed the LYH-HPTS from theoretical detection to device application. The LYH-HPTS material is not only simple to synthesize, cost-effective and stable, but also has the features of fast response, excellent sensitivity and selectivity, and good reproducibility, which provides a new approach for the rapid and accurate detection of nitroaromatic. [ABSTRACT FROM AUTHOR]

Two-dimensional materials with chemical formula MA2Z4 are a promising class of materials for optoelectronic applications. To exploit their potential, their stability with respect to air pollution has to be analyzed under different conditions. In a first-principle study based on density functional theory, we investigate the adsorption of three common environmental gas molecules (O2, H2O, and CO2) on monolayer WSi2N4, an established representative of the MA2Z4 family. The computed adsorption energies, charge transfer, and projected density of states of the polluted monolayer indicate a relatively weak interaction between substrate and molecules resulting in an ultrashort recovery time of the order of nanoseconds. O2 and water introduce localized states in the upper valence region but do not alter the semiconducting nature of WSi2N4 nor its band-gap size apart from a minor variation of a few tens of meV. Exploring the same scenario in the presence of photogenerated electrons and holes, we do not notice any substantial difference except for O2 chemisorption when negative charge carriers are in the system. In this case, monolayer WSi2N4 exhibits signs of irreversible oxidation, testified by an adsorption energy of -5.5 eV leading to an infinitely long recovery time, a rearrangement of the outermost atomic layer bonding with the pollutant, and n-doping of the system. Our results indicate stability of WSi2N4 against H2O and CO2 in both dark and bright conditions, suggesting the potential of this material in nanodevice applications. [ABSTRACT FROM AUTHOR]

Unique properties possessed by transition metal dichalcogenides (TMDs) attract much attention in terms of investigation of their formation and dependence of their characteristics on the production process parameters. Here, we investigate the formation of TMD films during chemical vapor deposition (CVD) in a mixture of thermally activated gaseous H2S and vaporized transition metals. Our observations of changes in morphology, Raman spectra, and photoluminescence (PL) properties in combination with in situ measurements of the electrical conductivity of the deposits formed at various precursor concentrations and CVD durations are evidence of existence of particular stages in the TMD material formation. Gradual transformation of PL spectra from trion to exciton type is detected for different stages of the material formation. The obtained results and proposed methods provide tailoring of TMD film characteristics necessary for particular applications like photodetectors, photocatalysts, and gas sensors. [ABSTRACT FROM AUTHOR]

Context: The relentless need for new materials to be used in electronic devices has opened new research directions in materials science. One of them involves using two-dimensional materials, among which there is current interest in using germanene. The heteroatom doping of germanene has been proposed as a possible approach to fine-tuning its electronic properties. However, this procedure is complicated because locating the dopants with a specific arrangement is challenging, thus achieving reproducibility. To avoid this problem, we propose the codoping of germanene to understand if dopants prefer to be agglomerated as observed for graphene or if they prefer to adopt a random disposition. Herein, we employed first-principles calculations to study 21 codoped germanene systems with one 3p (Al, Si, P, and S) and one 4p (Ga, As, and Se) element. Our results indicate that in the cases of AlP, AlS, GaP, GaS, GaAs, and GaSe codoped germanene, the dopants show a tendency to be located in specific lattice positions. The ortho disposition of dopants is preferred for AlP, AlS, GaP and GaS codoped germanene and their 4p counterparts GaAs and GaSe codoped germanene, and the materials showed interesting electronic properties making them suitable to develop germanene-based electronic materials. Methods: We utilized the M06-L, HSE06 methods accompanied by the 6-31G* basis sets to perform periodic boundary conditions calculations as implemented in Gaussian 09. The unit cells were sampled employing 100 k-points for geometry optimizations and 2000 k-points for electronic properties The ultrafine grid was employed. Results were visualized employing Gaussview 5.0.1. In addition to this, we performed B3LYP-D3 periodic calculations as implemented in CRYSTAL17. [ABSTRACT FROM AUTHOR]

Pulsed solid‐state lasers comprise 2D materials as saturable absorbers that contain transparent windows of the atmosphere and characteristic fingerprint spectra of several vital molecules that are significant in various applications and research. Over the past few decades, significant progress has been made in the development of narrow pulse width, high energy, high average output power, high efficiency, and simple construction of passively Q‐switched and mode‐locked lasers with 2D materials as saturable absorbers. This review summarizes the development of 2D materials, including graphene, transition metal dichalcogenides, black phosphorus, topological insulators, and MXenes, as modulator devices for solid‐state lasers owing to their broadband operation, excellent nonlinear optical response, low recovery time, ultrafast dynamic processing, and easy fabrication. Then, some new emerging and representative applications of pulsed solid‐state lasers are introduced and illustrated such as laser surgery, material processing, and lidar. Finally, future challenges and perspectives of pulsed solid‐state lasers with 2D materials‐based saturable absorbers are analyzed and addressed. The rapid development of pulsed solid‐state lasers with the continuous improvement of modulation technology is expected to expand opportunities for application in industry, scientific, medical, and other areas. [ABSTRACT FROM AUTHOR]

Photodetectors are critical components in a wide range of applications, from imaging and sensing to communications and environmental monitoring. Recent advancements in material science have led to the development of emerging photodetecting materials, such as perovskites, polymers, novel two-dimensional materials, and quantum dots, which offer unique optoelectronic properties and high tunability. This review presents a comprehensive overview of the synthesis methodologies for these cutting-edge materials, highlighting their potential to enhance photodetection performance. Additionally, we explore the design and fabrication of photodetectors with novel structures and physics, emphasizing devices that achieve high figure-of-merit parameters, such as enhanced sensitivity, fast response times, and broad spectral detection. Finally, we discuss the demonstration of new applications enabled by these advanced photodetectors, including flexible and wearable devices, next-generation imaging systems, and environmental sensing technologies. Through this review, we aim to provide insights into the current trends and future directions in the field of photodetection, guiding further research and development in this rapidly evolving area. [ABSTRACT FROM AUTHOR]

This current study focuses on predicting the electronic and magnetic behaviors of WCl3 monolayer when subjected to an external electric field. Unlike CrI3, the WCl3 monolayer displays a preference for an antiferromagnetic (AFM) ground state with an in-plane easy axis. This AFM state remains consistent across the entire spectrum (0–1 V/Å) of the external electric field. The indirect electronic band gap of the WCl3 monolayer is predicted to be about 2.16 eV. Through our analysis, we've identified that the dominance of the valence band maximum and the conduction band minimum stems mainly from the d x 2 - y 2 orbital (52% contribution) and the d z 2 orbital (97% contribution) respectively, attributed to the W element. The majority of electronic transitions related to the band gap arise due to these specific orbitals. Furthermore, the application of an external electric field can adjust the band gap to zero, prompting a transition from semiconductor to metal at an electric field intensity of E = 0.9 V/Å. Using mean field theory, we estimate the Neel temperature (TN) of the AFM system to be approximately 356 K, a notably high value surpassing room temperature. Moreover, the application of an electric field demonstrates the potential to further elevate the Neel temperature, crucial for the functionality of high-temperature spintronic devices. Our comprehensive examination also delves into the magnetic anisotropy of the WCl3 monolayer. The analysis of magnetic anisotropy energy (MAE) indicates that, contrary to the CrI3 monolayer, the transition metal W significantly contributes to the system's MAE, which is predicted to be − 3.44 meV / W . The magnetic easy axis aligns along the x direction (in-plane). [ABSTRACT FROM AUTHOR]

Since the isolation of graphene, two-dimensional (2D) materials have attracted increasing interest because of their excellent chemical and physical properties, as well as promising applications. Nonetheless, particular challenges persist in their further development, particularly in the effective identification of diverse 2D materials, the domains of large-scale and high-precision characterization, also intelligent function prediction and design. These issues are mainly solved by computational techniques, such as density function theory and molecular dynamic simulation, which require powerful computational resources and high time consumption. The booming deep learning methods in recent years offer innovative insights and tools to address these challenges. This review comprehensively outlines the current progress of deep learning within the realm of 2D materials. Firstly, we will briefly introduce the basic concepts of deep learning and commonly used architectures, including convolutional neural and generative adversarial networks, as well as U-net models. Then, the characterization of 2D materials by deep learning methods will be discussed, including defects and materials identification, as well as automatic thickness characterization. Thirdly, the research progress for predicting the unique properties of 2D materials, involving electronic, mechanical, and thermodynamic features, will be evaluated succinctly. Lately, the current works on the inverse design of functional 2D materials will be presented. At last, we will look forward to the application prospects and opportunities of deep learning in other aspects of 2D materials. This review may offer some guidance to boost the understanding and employing novel 2D materials. [ABSTRACT FROM AUTHOR]

With the increasing levels of CO2 emissions and the decreasing availability of energy resources, the electrocatalytic CO2 reduction reaction (CO2RR) offers a promising method for utilizing CO2 as a valuable resource using sustainable electrical energy. However, developing cost‐effective and highly efficient catalysts remains a significant challenge. Although zinc, an abundant element on Earth, has shown potential for converting CO2 into CO, its effectiveness as a catalyst for CO2 reduction is hindered by its low selectivity and stability. This study introduces a fast, efficient, and simple electrochemical deposition method for preparing porous zinc nanosheets (NS) using the hydrogen bubble template approach. The as‐prepared zinc NS catalyst demonstrates exceptional catalytic activity due to its highly porous structure and high specific surface area. At a voltage of −1 V versus RHE, it achieves a maximum CO Faradaic efficiency of 89.5 %. The performance of this system is characterized by a partial current density of around −6.17 mA cm−2 in an H‐cell configuration. Additionally, our catalyst exhibits remarkable durability over 10 h, highlighting its significant potential for real‐world utilization in CO2RR. [ABSTRACT FROM AUTHOR]

In recent years, solar energy has become popular because of its clean and renewable properties. Meanwhile, two-dimensional materials have become a new favorite in scientific research due to their unique physicochemical properties. Among them, monolayer molybdenum disulfide (MoS2), as an outstanding representative of transition metal sulfides, is a hot research topic after graphene. Therefore, we have conducted an in-depth theoretical study and design simulation using the finite-difference method in time domain (FDTD) for a solar absorber based on the two-dimensional material MoS2. In this paper, a broadband solar absorber and thermal emitter based on a single layer of molybdenum disulfide is designed. It is shown that the broadband absorption of the absorber is mainly due to the propagating plasma resonance on the metal surface of the patterned layer and the localized surface plasma resonance excited in the adjacent patterned air cavity. The research results show that the designed structure boasts an exceptional broadband performance, achieving an ultra-wide spectral range spanning 2040 nm, with an overall absorption efficiency exceeding 90%. Notably, it maintains an average absorption rate of 94.61% across its spectrum, and in a narrow bandwidth centered at 303 nm, it demonstrates a near-unity absorption rate, surpassing 99%, underscoring its remarkable absorptive capabilities. The weighted average absorption rate of the whole wavelength range (280 nm–2500 nm) at AM1.5 is above 95.03%, and even at the extreme temperature of up to 1500 K, its heat radiation efficiency is high. Furthermore, the solar absorber in question exhibits polarization insensitivity, ensuring its performance is not influenced by the orientation of incident light. These advantages can enable our absorber to be widely used in solar thermal photovoltaics and other fields and provide new ideas for broadband absorbers based on two-dimensional materials. [ABSTRACT FROM AUTHOR]

Water electrolysis has been recognized as a promising technology that can convert renewable energy into hydrogen for storage and utilization. The superior activity and low cost of catalysis are key factors in promoting the industrialization of water electrolysis. Single-atom catalysts (SACs) have attracted attention due to their ultra-high atomic utilization, clear structure, and highest hydrogen evolution reaction (HER) performance. In addition, the performance and stability of single-atom (SA) substrates are crucial, and various two-dimensional (2D) nanomaterial supports have become promising foundations for SA due to their unique exposed surfaces, diverse elemental compositions, and flexible electronic structures, to drive single atoms to reach performance limits. The SA supported by 2D nanomaterials exhibits various electronic interactions and synergistic effects, all of which need to be comprehensively summarized. This article aims to organize and discuss the progress of 2D nanomaterial single-atom supports in enhancing HER, including common and widely used synthesis methods, advanced characterization techniques, different types of 2D supports, and the correlation between structural hydrogen evolution performance. Finally, the latest understanding of 2D nanomaterial supports was proposed. [ABSTRACT FROM AUTHOR]

Phosphine‐ligated transition metal complexes play a pivotal role in modern catalysis, but our understanding of the impact of ligand counts on the catalysis performance of the metal center is limited. Here we report the synthesis of a low‐coordinate mono(phosphine)‐Rh catalyst on a metal‐organic layer (MOL), P‐MOL • Rh, and its applications in the hydrogenation of mono‐, di‐, and tri‐substituted alkenes as well as aryl nitriles with turnover numbers (TONs) of up to 390000. Mechanistic investigations and density functional theory calculations revealed the lowering of reaction energy barriers by the low steric hindrance of site‐isolated mono(phosphine)‐Rh sites on the MOL to provide superior catalytic activity over homogeneous Rh catalysts. The MOL also prevents catalyst deactivation to enable recycle and reuse of P‐MOL • Rh in catalytic hydrogenation reactions. [ABSTRACT FROM AUTHOR]

Abnormal cancer metabolism causes hypoxic and immunosuppressive tumor microenvironment (TME), which limits the antitumor efficacy of photodynamic therapy (PDT). Herein, we report a photosensitizing nanoscale metal–organic layer (MOL) with anchored 3‐bromopyruvate (BrP), BrP@MOL, as a metabolic reprogramming agent to enhance PDT and antitumor immunity. BrP@MOL inhibited mitochondrial respiration and glycolysis to oxygenate tumors and reduce lactate production. This metabolic reprogramming enhanced reactive oxygen species generation during PDT and reshaped the immunosuppressive TME to enhance antitumor immunity. BrP@MOL‐mediated PDT inhibited tumor growth by >90 % with 40 % of mice being tumor‐free, rejected tumor re‐challenge, and prevented lung metastasis. Further combination with immune checkpoint blockade potently regressed the tumors with >98 % tumor inhibition and 80 % of mice being tumor‐free. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have the characteristics of low loss, ultrafast carrier response, and wideband nonlinear saturable absorption, which have originated a range of innovative applications in photonics and photoelectric device owing to their advantages of layered structures. Graphene-like materials have recently been utilized for short and ultrashort pulsed laser generation in visible, near-infrared, and mid-infrared wavelength ranges. This article reviews the recent progress of 2D materials as saturable absorbers for Q-switched and mode-locked solid-state lasers. First, the preparation methods of 2D materials as saturable absorbers, the saturable absorption principle, and methods for measuring nonlinear absorption properties are introduced and explained theoretically. Second, the solid-state pulsed laser is summarized based on performance of 2D saturable absorbers in operating wavelength, output power, and pulse width. Finally, the development trends of two-dimensional saturable absorbers in solid-state lasers are prospected. [ABSTRACT FROM AUTHOR]

In this work, we employ molecular dynamics simulations with semi-empirical interatomic potentials to explore heat dissipation in Janus transition metal dichalcogenides (JTMDs). The middle atomic layer is composed of either molybdenum (Mo) or tungsten (W) atoms, and the top and bottom atomic layers consist of sulfur (S) and selenium (Se) atoms, respectively. Various nanomaterials have been investigated, including both pristine JTMDs and nanostructures incorporating inner triangular regions with a composition distinct from the outer bulk material. At the beginning of our simulations, a temperature gradient across the system is imposed by heating the central region to a high temperature while the surrounding area remains at room temperature. Once a steady state is reached, characterized by a constant energy flux, the temperature control in the central region is switched off. The heat attenuation is investigated by monitoring the characteristic relaxation time (τav) of the local temperature at the central region toward thermal equilibrium. We find that SMoSe JTMDs exhibit thermal attenuation similar to conventional TMDs (τav~10–15 ps). On the contrary, SWSe JTMDs feature relaxation times up to two times as high (τav~14–28 ps). Forming triangular lateral heterostructures in their surfaces leads to a significant slowdown in heat attenuation by up to about an order of magnitude (τav~100 ps). [ABSTRACT FROM AUTHOR]

In the attempt to induce spin-polarized states in graphene (Gr), rare-earth deposition on Gr/Co(0001) has been demonstrated to be a successful strategy: the coupling of graphene with the cobalt substrate provides spin-polarized conical-shaped states (minicone) and the rare-earth deposition brings these states at the Fermi level. In this manuscript, we theoretically explore the feasibility of an analogue approach applied on Gr/Ni(111) doped with rare-earth ions by means of density functional theory calculations. Even if not well mentioned in the literature, this system owns a minicone, similar to the cobalt case. By testing different rare-earth ions, not only do we suggest which one can provide the required doping but we also explain the effect behind this proper charge transfer. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have emerged as a promising candidate in the chemoresistive gas sensor field to overcome the disadvantages of conventional metal-oxide semiconductors owing to their strong surface activities and high surface-to-volume ratio. This review summarizes the various approaches to enhance the 2D-material-based gas sensors and provides an overview of their progress. The distinctive attributes of semiconductor gas sensors employing 2D materials will be highlighted with their inherent advantages and associated challenges. The general operating principles of semiconductor gas sensors and the unique characteristics of 2D materials in gas-sensing mechanisms will be explored. The pros and cons of 2D materials in gas-sensing channels are discussed, and a route to overcome the current challenges will be delivered. Finally, the recent advancements to enhance the performance of 2D-material-based gas sensors including photo-activation, heteroatom doping, defect engineering, heterostructures, and nanostructures will be discussed. This review should offer a broad range of readers a new perspective toward the future development of 2D-material-based gas sensors. [ABSTRACT FROM AUTHOR]

Owing to the atomically thin nature, two-dimensional (2D) oxide materials have been widely reported to exhibit exciting transport and dielectric properties, such as fine gate controllability and ultrahigh carrier mobility, that outperform their bulk counterpart. However, unlike the successful synthesis of bulk oxide single crystals, reliable methods for synthesizing large-area single crystal of 2D oxide, that would suppress the negative influence from defective grain boundaries, remain unavailable, especially for nonlayered oxide. Herein, we report that the lattice symmetry between the substrate and cerium dioxide (CeO2) would allow for the aligned nucleation and epitaxial growth of CeO2 on sapphire substrates, enabling the wafer-sized growth of CeO2 single crystal. The careful tuning of the growth temperature and oxygen flow rate contributed to the harvesting of CeO2 wafer with reduced thickness and enhanced growth rates. The removal of grain boundaries improved the dielectric performance in terms of high dielectric strength (Ebd ≈ 8.8 MV·cm−1), suppressed leakage current, along with high dielectric constants (εr ≈ 24). Our work demonstrates that with fine dielectric performance and ease of synthesizing wafer-sized single crystals, CeO2 can function as potential candidate as gate insulator for 2D-materials based nanoelectronics, and we believe the reported protocol of aligned nucleation can be extended to other 2D oxides. [ABSTRACT FROM AUTHOR]

Plasmonic hot carrier engineering holds great promise for advanced infrared optoelectronic devices. The process of hot carrier transfer has the potential to surpass the spectral limitations of semiconductors, enabling detection of sub‐bandgap infrared photons. By harvesting hot carriers prior to thermalization, energy dissipation is minimized, leading to highly efficient photoelectric conversion. Distinguished from conventional band‐edge carriers, the ultrafast interfacial transfer and ballistic transport of hot carriers present unprecedented opportunities for high‐speed photoelectric conversion. However, a complete description on the underlying mechanism of hot‐carrier infrared optoelectronic device is still lacking, and the utilization of this strategy for tailoring infrared response is in its early stages. This review aims to provide a comprehensive overview of the generation, transfer and transport dynamics of hot carriers. Basic principles of hot‐carrier conversion in heterostructures are discussed in detail. In addition, progresses of two‐dimensional (2D) infrared hot‐carrier optoelectronic devices are summarized, with a specific emphasis on photodetectors, solar cells, light‐emitting devices and novel functionalities through hot‐carrier engineering. Furthermore, challenges and prospects of hot‐carrier device towards infrared applications are highlighted. [ABSTRACT FROM AUTHOR]

Abstract Two-dimensional materials with chemical formula MA2Z4 are a promising class of materials for optoelectronic applications. To exploit their potential, their stability with respect to air pollution has to be analyzed under different conditions. In a first-principle study based on density functional theory, we investigate the adsorption of three common environmental gas molecules (O2, H2O, and CO2) on monolayer WSi2N4, an established representative of the MA2Z4 family. The computed adsorption energies, charge transfer, and projected density of states of the polluted monolayer indicate a relatively weak interaction between substrate and molecules resulting in an ultrashort recovery time of the order of nanoseconds. O2 and water introduce localized states in the upper valence region but do not alter the semiconducting nature of WSi2N4 nor its band-gap size apart from a minor variation of a few tens of meV. Exploring the same scenario in the presence of photogenerated electrons and holes, we do not notice any substantial difference except for O2 chemisorption when negative charge carriers are in the system. In this case, monolayer WSi2N4 exhibits signs of irreversible oxidation, testified by an adsorption energy of -5.5 eV leading to an infinitely long recovery time, a rearrangement of the outermost atomic layer bonding with the pollutant, and n-doping of the system. Our results indicate stability of WSi2N4 against H2O and CO2 in both dark and bright conditions, suggesting the potential of this material in nanodevice applications.

Molybdenum disulfide (MoS2) is a representative two-dimensional layered transition-metal dichalcogenide semiconductor. Layer-number-dependent electronic properties are attractive in the development of nanomaterial-based electronics for a wide range of applications including sensors, switches, and amplifiers. MoS2 field-effect transistors (FETs) have been studied as promising future nanoelectronic devices with desirable features of atomic-level thickness and high electrical properties. When a naturally n -doped MoS2 is contacted with metals, a strong Fermi-level pinning effect adjusts a Schottky barrier and influences its electronic characteristics significantly. In this study, we investigate multilayer MoS2 Schottky barrier FETs (SBFETs), emphasizing the metal-contact impact on device performance via computational device modeling. We find that p -type MoS2 SBFETs may be built with appropriate metals and gate voltage control. Furthermore, we propose ambipolar multilayer MoS2 SBFETs with asymmetric metal electrodes, which exhibit gate-voltage dependent ambipolar transport behavior through optimizing metal contacts in MoS2 device. Introducing a dual-split gate geometry, the MoS2 SBFETs can further operate in four distinct configurations: p − p, n − n, p − n, and n − p. Electrical characteristics are calculated, and improved performance of a high rectification ratio can be feasible as an attractive feature for efficient electrical and photonic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] The development of efficient and stable electrocatalysts is crucial for the advancement of green and clean hydrogen energy technologies. In this work, we synthesized a nanocomposite of nickel–iron layered double hydroxide/molybdenum titanium carbide (NiFe-LDHs/Mo 2 Ti 2 C 3) using a deep eutectic solvent (DESs) by the solvothermal method. The formation of NiFe-LDHs/Mo 2 Ti 2 C 3 nanocomposite was confirmed by various electron microscopic and spectroscopic techniques. The synthesized nanocomposite was investigated as a bifunctional electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under the alkaline condition. The NiFe-LDHs/Mo 2 Ti 2 C 3 -based electrodes exhibit small overpotentials of 204 and 306 mV for HER and OER at a current density of 10 mA cm−2. The anchor of NiFe-LDHs on the surface of Mo 2 Ti 2 C 3 induces an interfacial synergistic effect, leading to a significantly improvement in electrochemical performance. Remarkably, the proposed NiFe-LDHs/Mo 2 Ti 2 C 3 modified electrode demonstrates superior performance compared to many recently reported LDHs and MXenes-based electrocatalysts in an alkaline environment. Furthermore, a symmetrical two-electrode water splitting setup employing the NiFe-LDHs/Mo 2 Ti 2 C 3 electrocatalyst requires an electrolysis voltage of 1.65 V to achieve a current density of 10 mA cm−2. The findings provide a new perspective on the rational design and synthesis of multifunctional electrocatalysts for electrochemical applications. [ABSTRACT FROM AUTHOR]

Ta 4 C 3 T x MXene, a novel two-dimensional material, shows significant application potential for electromagnetic wave (EMW) absorption because of its unique layered structure and high conductivity. In this study, hydrofluoric acid etching was used to obtain Ta 4 C 3 T x MXenes with varying interlayer spaces by adjusting the etching duration, which enhanced the EMW absorption performance. The impact of interlayer spacing on the EMW absorption performance of Ta 4 C 3 T x MXene was systematically evaluated for the first time. The results show that the sample etched with hydrofluoric acid for 48 h (S2-48 h) exhibited the best EMW absorption performance. For S2-48 h, the optimal reflection loss (RL) value was −33.53 dB at a frequency of 9.74 GHz and a thickness of 1.4 mm. In addition, the widest effective absorption bandwidth was 2.97 GHz (10.73–13.7 GHz), which was achieved at a frequency of 11.72 GHz and a thickness of 1.2 mm. This outstanding performance is mainly attributed to good impedance matching and multiple loss mechanisms induced by the etching process, including conduction loss, dipolar polarization, interfacial polarization, and multiple RLs. Furthermore, this research expands the application potential of two-dimensional MXene materials in EMW absorption. [ABSTRACT FROM AUTHOR]

Abstract Recent advancements in cancer research have led to the generation of innovative nanomaterials for improved diagnostic and therapeutic strategies. Despite the proven potential of two-dimensional (2D) molybdenum disulfide (MoS2) as a versatile platform in biomedical applications, few review articles have focused on MoS2-based platforms for cancer theranostics. This review aims to fill this gap by providing a comprehensive overview of the latest developments in 2D MoS2 cancer theranostics and emerging strategies in this field. This review highlights the potential applications of 2D MoS2 in single-model imaging and therapy, including fluorescence imaging, photoacoustic imaging, photothermal therapy, and catalytic therapy. This review further classifies the potential of 2D MoS2 in multimodal imaging for diagnostic and synergistic theranostic platforms. In particular, this review underscores the progress of 2D MoS2 as an integrated drug delivery system, covering a broad spectrum of therapeutic strategies from chemotherapy and gene therapy to immunotherapy and photodynamic therapy. Finally, this review discusses the current challenges and future perspectives in meeting the diverse demands of advanced cancer diagnostic and theranostic applications. Graphical Abstract

Light–matter interactions in two-dimensional (2D) materials have been the focus of research since the discovery of graphene. The light–matter interaction length in 2D materials is, however, much shorter than that in bulk materials owing to the atomic nature of 2D materials. Plasmonic nanostructures are usually integrated with 2D materials to enhance the light–matter interactions, offering great opportunities for both fundamental research and technological applications. Nanoparticle-on-mirror (NPoM) structures with extremely confined optical fields are highly desired in this aspect. In addition, 2D materials provide a good platform for the study of plasmonic fields with subnanometer resolution and quantum plasmonics down to the characteristic length scale of a single atom. A focused and up-to-date review article is highly desired for a timely summary of the progress in this rapidly growing field and to encourage more research efforts in this direction. In this review, we will first introduce the basic concepts of plasmonic modes in NPoM structures. Interactions between plasmons and quasi-particles in 2D materials, e.g., excitons and phonons, from weak to strong coupling and potential applications will then be described in detail. Related phenomena in subnanometer metallic gaps separated by 2D materials, such as quantum tunneling, will also be touched. We will finally discuss phenomena and physical processes that have not been understood clearly and provide an outlook for future research. We believe that the hybrid systems of 2D materials and NPoM structures will be a promising research field in the future.

The impact of radiation on MoS2-based devices is an important factor in the utilization of two-dimensional semiconductor-based technology in radiation-sensitive environments. In this study, the effects of gamma irradiation on the electrical variations in MoS2 field-effect transistors with buried local back-gate structures were investigated, and their related effects on Al2O3 gate dielectrics and MoS2/Al2O3 interfaces were also analyzed. The transfer and output characteristics were analyzed before and after irradiation. The current levels decreased by 15.7% under an exposure of 3 kGy. Additionally, positive shifts in the threshold voltages of 0.50, 0.99, and 1.15 V were observed under irradiations of 1, 2, and 3 kGy, respectively, compared to the non-irradiated devices. This behavior is attributable to the comprehensive effects of hole accumulation in the Al2O3 dielectric interface near the MoS2 side and the formation of electron trapping sites at the interface, which increased the electron tunneling at the MoS2 channel/dielectric interface. [ABSTRACT FROM AUTHOR]

Bi 2 WO 6 has attracted extensive attention in photocatalysts in recent years as a typical Aurivillius oxide. However, it suffers from severe electron-hole recombination due to the large charge transfer distance from bulk to surface. Unfortunately, strong chemical bonds between the neighboring layers in Aurivillius oxides lead to difficulties in the construction of 2D materials. Here, a facile NaBH 4 -assisted hydrothermal method is developed to construct 2D Bi 2 WO 6 nanosheets with adjustable thickness from 4.03 to 1.51 nm and O vacancies density (named as BWO-x, x = 15, 30, 45, 60). By balancing the thickness and the O vacancy density in the nanosheets, the charge separation efficiency can be tuned and consequently, the photocatalytic activity can be optimized, leading to over 11 times enhancement in photocatalytic hydrogen evolution. Furthermore, the best performed nanosheets demonstrate universality in dye polluted water treatment. Nearly 100% degradation can be reached after only 5, 50, and 30 min with degradation rate constant of 29.73, 3.21, and 6.62 min−1g−1 for Rhodamine B, methyl orange, and methylene blue, respectively. This work provides a comprehensive approach to produce ultrathin 2D nanosheets of Aurivillius photocatalysts for enhanced charge separation and photocatalytic activity. • Ultrathin 2D Bi 2 WO 6 nanosheets have been constructed. • Improved charge separation has been achieved in the ultrathin 2D BWO nanosheets. • The 2D BWO nanosheets exhibit enhanced photocatalytic H 2 evolution and dye degradation. • This work provides a comprehensive approach to produce ultrathin 2D nanosheets of Aurivillius Oxides. [ABSTRACT FROM AUTHOR]

New two‐dimensional (2D) transition‐metal borides have attracted considerable interest in research on electrode materials for Li‐ion batteries (LIBs) owing to their promising properties. In this study, 2D molybdenum boride (Mo2B2) with and without transition metal (TM, TM=Mn, Fe, Co, Ni, Ru, and Pt) atom doping was investigated. Our results indicated that all TM‐doped Mo2B2 samples exhibited excellent electronic conductivity, similar to the intrinsic 2D Mo2B2 metal behavior, which is highly beneficial for application in LIBs. Moreover, we found that the diffusion energy barriers of Li along paths 1 and 2 for all TM‐doped Mo2B2 samples are smaller than 0.30 and 0.24 eV of the pristine Mo2B2. In particular, for 2D Co‐doped Mo2B2, the diffusion energy barriers of Li along paths 1 and 2 are reduced to 0.14 and 0.11 eV, respectively, making them the lowest Li diffusion barriers in both paths 1 and 2. This indicates that TM doping can improve the electrochemical performance of 2D Mo2B2 and that Co‐doped Mo2B2 is a promising electrode material for LIBs. Our work not only identifies electrode materials with promising electrochemical performance but also provides guidance for the design of high‐performance electrode materials for LIBs. [ABSTRACT FROM AUTHOR]

The carbides and nitrides of transition metals known as "MXenes" refer to a fast-growing family of two-dimensional materials discovered in 2011. Thanks to their unique nanolayer structure, superior electrical, mechanical, and thermal properties, MXenes have shown great potential in addressing the critical overheating issues that jeopardize the performance, stability, and lifetime of high-energy-density components in modern devices such as microprocessors, integrated circuits, and capacitors, etc. The outstanding intrinsic thermal conductivity of MXenes has been proved by experimental and theoretical research. Numerous MXenes-enabled high thermal conductivity composites incorporated with polymer matrix have also been reported and widely used as thermal management materials. Considering the booming heat dissipation demands, MXenes-enabled thermal management material is an extremely valuable and scalable option for modern electronics industries. However, the fundamental thermal transport mechanisms behind the MXenes family remain unclear. The MXene thermal conductivity disparities between the theoretical prediction and experimental results are still significant. To better understand the thermal conduction in MXenes and provide more insights for engineering high-performance MXene thermal management materials, in this article, we summarize recent progress on thermal conductive MXenes. The essential factors that affect MXenes intrinsic thermal conductivities are tackled, selected MXenes-polymer composites are highlighted, and prospects and challenges are also discussed. [ABSTRACT FROM AUTHOR]

The boundary slip condition is pivotal for nanoscale fluid motion. Recent research has primarily focused on simulating the interaction mechanism between the electronic structure of two-dimensional materials and slip of water at the nanoscale, raising the possibility for ultralow friction flow of water at the nanoscale. However, experimentally elucidating electronic interactions at the dynamic solid–liquid interface to control boundary slip poses a significant challenge. In this study, the crucial role of electron structures at the dynamic solid–liquid interface in regulating slip length was revealed. Notably, the slip length of water on the molybdenum disulfide/graphene (MoS2/G) heterostructure (100.9 ± 3.6 nm) significantly exceeded that of either graphene (27.7 ± 2.2 nm) or MoS2 (5.7 ± 3.1 nm) alone. It was also analyzed how electron transfer significantly affected interface interactions. Excess electrons played a crucial role in determining the type and proportion of excitons at both MoS2–water and MoS2/G–water interfaces. Additionally, by applying voltage, distinct photoluminescence (PL) responses at static and dynamic interfaces were discovered, achieving a 5-fold modulation in PL intensity and a 2-fold modulation in the trion to exciton intensity ratio. More electrons transfer from the top graphene to the bottom MoS2 at the MoS2/G–water interface, reducing surface charge density. Thus, the reduction of electrostatic interactions between the solid and water leads to an increased slip length of water on the MoS2/G heterostructure. The process aids in comprehending the origin of frictional resistance at the subatomic scale. This work establishes a foundation for actively controlling and designing of fluid transport at the nanoscale. [ABSTRACT FROM AUTHOR]

Two-dimensional materials are excellent lubricants with inherent advantages. However, superlubricity has been reported for only a few of these materials. Unfortunately, other promising two-dimentional (2D) materials with different physical properties cannot be discovered or applied in production; thus, energy consumption can be greatly reduced. Here, we carry out high-throughput calculations for 1,475 2D materials and screen for low-friction materials. To set a standard, we propose, for the first time, a geometry-independent lubricating figure of merit based on the conditions for stick-slip transition and our theory of Moiré friction. For the efficient calculation of this figure of merit, an innovative approach was developed based on an improved registry index model. Through calculations, 340 materials were found to have a figure of merit lower than 10−3. Eventually, a small set of 21 materials with a figure of merit lower than 10−4 were screened out. These materials can provide diverse choices for various applications. In addition, the efficient computational approach demonstrated in this work can be used to study other stacking-dependent properties. [ABSTRACT FROM AUTHOR]

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In this paper, we investigate the so-called electronic dressed states, a unified quasiparticle resulting from the interaction between electrons in a two-dimensional material with an off-resonance optical dressing field. If the frequency of this field is much larger than all characteristic energies in the system, such as the Fermi energy or bandgap(s), the electronic band structure is affected by radiation so that some important properties of the electron dispersions could be modified in a way desirable for practical applications. For example, circularly polarized light can be used to vary the bandgap of Dirac materials: it opens a gap in graphene and other metallic and semimetallic lattices, or it modifies the magnitude of an existing gap. This will either enhance or reduce a gap, depending on its initial value as well as properties of a host material. Here, we consider gapped dice and Lieb lattices as samples, and we put forward a full theoretical model to reveal how these electronic states are deformed by elliptically-polarized irradiation with a focus on the generation and modification of a bandgap. [ABSTRACT FROM AUTHOR]

The contact resistance formed between MoS2 and metal electrodes plays a key role in MoS2-based electronic devices. The Schottky barrier height (SBH) is a crucial parameter for determining the contact resistance. However, the SBH is difficult to modulate because of the strong Fermi-level pinning (FLP) at MoS2-metal interfaces. Here, we investigate the FLP effect and the contact types of monolayer and multilayer MoS2-metal van der Waals (vdW) interfaces using density functional theory (DFT) calculations based on Perdew–Burke–Ernzerhof (PBE) level. It has been demonstrated that, compared with monolayer MoS2-metal close interfaces, the FLP effect can be significantly reduced in monolayer MoS2-metal vdW interfaces. Furthermore, as the layer number of MoS2 increases from 1L to 4L, the FLP effect is first weakened and then increased, which can be attributed to the charge redistribution at the MoS2-metal and MoS2-MoS2 interfaces. In addition, the p-type Schottky contact can be achieved in 1L–4L MoS2-Pt, 3L MoS2-Au, and 2L–3L MoS2-Pd vdW interfaces, which is useful for realizing complementary metal oxide semiconductor (CMOS) logic circuits. These findings indicated that the FLP and contact types can be effectively modulated at MoS2-metal vdW interfaces by selecting the layer number of MoS2. [ABSTRACT FROM AUTHOR]

Although hexagonal boron nitride (h‐BN) was initially considered a less promising photocatalyst due to its large band gap and apparent chemical inertness, its unique two‐dimensional lamellar structure coupled with high stability and environmental friendliness, as the second largest van der Waals material after graphene, provides a unique platform for photocatalytic innovation. This review not only highlights the intrinsic qualities of h‐BN with photocatalytic potentials, such as high stability, environmental compatibility, and tunable bandgap through various modification strategies but also provides a comprehensive overview of the recent advances in h‐BN‐based nanomaterials for environmental and energy applications, as well as an in‐depth description of the modification methods and fundamental properties for these applications. In addition, we discuss the challenges and prospects of h‐BN‐based nanomaterials for future photocatalysis. [ABSTRACT FROM AUTHOR]

While considering the appearance of Dirac cones in spin–orbit coupled two-dimensional materials, Young and Kane (Phys Rev Lett 115:126803, 2015) have found that, in the absence of other symmetries, spatial-, time-reversal and vertical glide plane (or horizontal screw rotation) symmetry give four-fold degenerate Dirac point at the time-reversal invariant momentum along the fractional translation. Here we show in which cases additional symmetries lead to Dirac line instead of Dirac cone in the band structure. We found three centrosymmetric, non-symmorphic layer double groups with line-like degeneracies instead of nodal points. We show that besides these Dirac lines, no other band contacts occur, including the accidental ones. Our results are illustrated using a tight binding example arising from s-orbitals on two atoms in the primitive cell. Finally, we discussed ways towards realistic materials where such features in the electronic dispersion are expected to appear. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) anisotropic materials have garnered significant attention in the realm of anisotropic optoelectronic devices due to their remarkable electrical, optical, thermal, and mechanical properties. While extensive research has delved into the optical and electrical characteristics of these materials, there remains a need for further exploration to identify novel materials and structures capable of fulfilling device requirements under various conditions. Here, we employ heterojunction interface engineering with black phosphorus (BP) to disrupt the C3 rotational symmetry of monolayer WS2. The resulting WS2/BP heterostructure exhibits pronounced anisotropy in exciton emissions, with a measured anisotropic ratio of 1.84 for neutral excitons. Through a comprehensive analysis of magnetic-field-dependent and temperature-evolution photoluminescence spectra, we discern varying trends in the polarization ratio, notably observing a substantial anisotropy ratio of 1.94 at a temperature of 1.6 K and a magnetic field of 9 T. This dynamic behavior is attributed to the susceptibility of the WS2/BP heterostructure interface strain to fluctuations in magnetic fields and temperatures. These findings provide valuable insights into the design of anisotropic optoelectronic devices capable of adaptation to a range of magnetic fields and temperatures, thereby advancing the frontier of material-driven device engineering. [ABSTRACT FROM AUTHOR]