Search Results (149)

One of the key challenges in commercializing proton exchange membrane (PEM) electrolyzer technology is reducing the production costs while maintaining high efficiency and operational stability. Significant contributors to the overall cost of the device are the electrode catalysts with IrO₂ and Pt/C. Due to the high cost and limited availability of noble metals, there is growing interest in developing alternative, low-cost catalytic materials. In recent years, two-dimensional transition metal dichalcogenides (2D TMDCs), such as molybdenum disulfide (MoS₂) and rhenium disulfide (ReS₂), have attracted considerable attention due to their promising electrochemical properties for hydrogen evolution reactions (HERs). These materials exhibit unique properties, such as a high surface area or catalytic activity localized at the edges of the layered structure, which can be further enhanced through defect engineering or phase modulation. To increase the catalytically active surface area, the investigated materials were deposited on a carbon-based support—Vulcan XC-72R—selected for its high electrical conductivity and large specific surface area. This study investigated the physicochemical and electrochemical properties of six catalyst samples with varying MoS₂ and ReS₂ to carbon support ratios. Among the composites analyzed, the best sample on MoS₂ (containing the most carbon soot) and the best sample on ReS₂ (containing the least carbon soot) were selected. These were then used as cathode catalysts in an experimental PEM electrolyzer setup. The results confirmed satisfactory catalytic activity of the tested materials, indicating their potential as alternatives to conventional noble metal-based catalysts and providing a foundation for further research in this area. Full article

Near-infrared (NIR) photoelectric synaptic devices show great potential in studying NIR artificial visual systems integrating excellent optical characteristics and bionic synaptic plasticity. However, NIR synapses based on transition metal dichalcogenides (TMDCs) suffer from low stability and poor environmental performance. Thus, an environmentally friendly NIR synapse was fabricated based on lanthanide-doped upconversion nanoparticles (UCNPs) and two-dimensional (2D) WSe₂ via solution spin coating technology. Biological synaptic functions were simulated successfully through 975 nm laser regulation, including paired-pulse facilitation (PPF), spike rate-dependent plasticity, and spike timing-dependent plasticity. Handwritten digital images were also recognized by an artificial neural network based on device characteristics with a high accuracy of 97.24%. In addition, human and animal identification in foggy and low-visibility surroundings was proposed by the synaptic response of the device combined with an NIR laser and visible simulation. These findings might provide promising strategies for developing a 24/7 visual response of humanoid robots. Full article

Fermi-level pinning (FLP) at metal–semiconductor interfaces remains a key obstacle to achieving low-resistance contacts in two-dimensional (2D) transition metal dichalcogenide (TMDC)-based heterostructures. Here, we present a first-principles study of Schottky barrier formation in WSe₂-MoSe₂ van der Waals heterostructures interfaced with four representative metals (Ag, Al, Au, and Pt). It was found that all metal–WSe₂/MoSe₂ direct contacts induce pronounced metal-induced gap states (MIGSs), leading to significant FLP inside the WSe₂/MoSe₂ band gaps and elevated Schottky barrier heights (SBHs) greater than 0.31 eV. By introducing a 2D metal-doped metallic (mWSe/mMoSe) layer between WSe₂/MoSe₂ and the metal electrodes, the MIGSs can be effectively suppressed, resulting in nearly negligible SBHs for both electrons and holes, with even an SBH of 0 eV observed in the Ag-AgMoSe-MoSe₂ contact, thereby enabling quasi-Ohmic contact behavior. Our results offer a universal and practical strategy to mitigate FLP and achieve high-performance TMDC-based electronic devices with ultralow contact resistance. Full article

Two-dimensional (2D) materials have revolutionized the field of optoelectronics by offering exceptional properties such as atomically thin structures, high carrier mobility, tunable bandgaps, and strong light–matter interactions. These attributes make them ideal candidates for next-generation photodetectors operating across a broad spectral range—from ultraviolet to mid-infrared. This review comprehensively examines the recent progress in 2D material-based photodetectors, highlighting key material classes including graphene, transition metal dichalcogenides (TMDCs), black phosphorus (BP), MXenes, chalcogenides, and carbides. We explore their photodetection mechanisms—such as photovoltaic, photoconductive, photothermoelectric, bolometric, and plasmon-enhanced effects—and discuss their impact on critical performance metrics like responsivity, detectivity, and response time. Emphasis is placed on material integration strategies, heterostructure engineering, and plasmonic enhancements that have enabled improved sensitivity and spectral tunability. The review also addresses the remaining challenges related to environmental stability, scalability, and device architecture. Finally, we outline future directions for the development of high-performance, broadband, and flexible 2D photodetectors for diverse applications in sensing, imaging, and communication technologies. Full article

Opto-spintronics is an emerging field that focuses on harnessing light to manipulate and analyze electron spins to develop next-generation electronic devices. This paper explores recent progress and the role of solid-state materials in opto-spintronics by focusing on key classes of materials, such as ferromagnetic semiconductors, two-dimensional (2D) transition metal dichalcogenides (TMDCs), and topological insulators. It examines the unique properties of ferromagnetic and antiferromagnetic materials and their ability to interact with light to affect spin dynamics, offering potential for improved sensing and quantum computing. By combining opto-spintronics with solid-state systems, spintronic devices could become faster and more efficient, leading to new technological advancements and scalable technologies. Full article

Objective: Tuo-Min-Ding-Chuan decoction (TMDC), a traditional Chinese prescription, has demonstrated significant clinical efficacy in treating allergic asthma. This study aimed to investigate the mechanism of TMDC in treating asthma from the perspective of Treg cells and gut microbiota across distinct gut segments (jejunum, ileum, cecum, and colon). Methods: An ovalbumin (OVA)-induced asthma model was established in mice, followed by oral administration of TMDC at high, medium, and low dose. Immune cells and lung inflammation were examined to assess asthma severity. Microbial composition was determined by 16S rRNA sequencing. Antibiotic cocktail and Lactobacillus rhamnosus GG (LGG) were administrated to confirm the key role of specific bacteria. Results: TMDC attenuated lung inflammation (p < 0.01) and eosinophilic infiltration (p < 0.01) as well as IL-4 and IL-5 secretion (p < 0.01); it was also associated with an increase in Treg cells in the lung, small intestine (SI), and colon (p < 0.05). Meanwhile, TMDC restored the number of microbiota species and the Shannon index in the hindgut and reinstated beneficial bacteria, such as Allobaculum and Turicibacter, which were diminished in asthmatic mice. Notably, TMDC significantly enriched Bifidobacterium and Lactobacillus, particularly in the hindgut. Lactobacillus abundance was significantly correlated (p < 0.05) with Treg cells, IL-4, IL-5, and eosinophils. Furthermore, LGG supplementation restored elevated lung inflammation (p < 0.05) and decreased Treg cells (p < 0.01) due to antibiotic-induced microbiota depletion. Conclusion: TMDC alleviated asthma by promoting Treg cell expansion in a Lactobacillus-dependent manner across different gut segments, providing new insights into its therapeutic mechanisms. Full article

With the rapid development of high-speed imaging, aerospace, and telecommunications, high-performance photodetectors across a broadband spectrum are urgently demanded. Due to abundant surface configurations and exceptional electronic properties, two-dimensional (2D) materials are considered as ideal candidates for broadband photodetection applications. However, broadband photodetectors with both high responsivity and fast response time remain a challenging issue for all the researchers. This review paper is organized as follows. Introduction introduces the fundamental properties and broadband photodetection performances of transition metal dichalcogenides (TMDCs), perovskites, topological insulators, graphene, and black phosphorus (BP). This section provides an in-depth analysis of their unique optoelectronic properties and probes the intrinsic physical mechanism of broadband detection. In Two-Dimensional Material-Based Broadband Photodetectors, some innovative strategies are given to expand the detection wavelength range of 2D material-based photodetectors and enhance their overall performances. Among them, chemical doping, defect engineering, constructing heterostructures, and strain engineering methods are found to be more effective for improving their photodetection performances. The last section addresses the challenges and future prospects of 2D material-based broadband photodetectors. Furthermore, to meet the practical requirements for very large-scale integration (VLSI) applications, their work reliability, production cost and compatibility with planar technology should be paid much attention. Full article

The transition metal dichalcogenide (TMDC) NbSe₂ is a highly conductive and superconducting material with great potential for next-generation electronic and optoelectronic devices. However, its bulk form suffers from reduced charge density and conductivity due to interlayer van der Waals interactions. To address this, we exfoliated NbSe₂ into nanosheets using lithium-ion intercalation and utilized them as diaphragms in acoustic transducers. Conventional electromagnetic and electrostatic mechanisms have limitations in sound pressure level (SPL) performance at high and low frequencies, respectively. To overcome this, we developed a hybrid force mechanism combining the strengths of both approaches. The NbSe₂ nanosheets were successfully prepared and analyzed, and the NbSe₂-based hybrid acoustic transducer (N-HAT) demonstrated significantly improved SPL performance across a wide frequency range. This study offers a novel approach for designing high-performance acoustic devices by harnessing the unique properties of NbSe₂. Full article

We perform a theoretical investigation of the electron–surface optical phonon (SOP) interaction in Van der Waals heterostructures (vdWHs) formed by monolayer graphene (1LG) and transition metal dichalcogenides (TMDCs), using eigenenergies obtained from the tight-binding Hamiltonian for electrons. Our analysis reveals that the SOP interaction strength strongly depends on the specific TMDC material. TMDC layers generate localized SOP modes near the 1LG/TMDC interface, serving as effective scattering centers for graphene carriers through long-range Fröhlich coupling. This interaction leads to resonant coupling of electronic sub-levels with SOP, resulting in Rabi splitting of the electronon energy levels. We further explore the influence of different TMDCs, such as WS₂, WSe₂, MoS₂, and MoSe₂, on transport properties such as SOP-limited mobility, resistivity, conductivity, and scattering rates across various temperatures and charge carrier densities. Our analysis confirms that at elevated temperatures and low carrier densities, surface optical phonon scattering becomes a dominant factor in determining resistivity. Additionally, we investigate the Auger recombination process at the 1LG/TMDC interface, showing that both Auger and SOP scattering rates increase significantly at room temperature and higher, ultimately converging to constant values as the temperature rises. In contrast, their impact is minimal at lower temperatures. These results highlight the potential of 1LG/TMDC-based vdWHs for controlling key processes, such as SOP interactions and Auger recombination, paving the way for high-performance nanoelectronic and optoelectronic devices. Full article

The prerequisite for rapid and steady development of TMDC-based optoelectronic devices is high efficiency in materials preparation, which relies on a mature synthesis technique and optimized production conditions. Visualization based on numerical simulation, which illustrates the impact of growth parameters on deposited products, is helpful to understand formation mechanisms and modify growth conditions. In this work, we construct two models with two different substrate placements, where the substrate is parallel or perpendicular to gas flow direction. The simulation results show more velocity distribution uniformity across a wider range from −1.4 cm to 1.4 cm for vertically placed (VP) compared to horizontally placed (HP) substrates. The calculated average velocities of 0.048, 0.053, 0.078, 0.137, and 0.391 cm/s along five different positions on the VP substrate are greater than the values of 0.027, 0.026, 0.025, 0.023, and 0.036 cm/s on the HP substrate. Comparing the precursor concentration distributions on both substrates, it is observed that the S molar concentration gradient on both substrates is negligible and the uniform Mo molar concentrations from z = −1.4 cm to 2.0 cm on the VP substrate ensure minimal change in the S/Mo ratio, which contributes to forming single-morphology domains. Furthermore, increasing the distance between the precursor inlets and the VP substrate decreases the amount of molecules on the substrate surface, achieving near-stoichiometry and promoting monolayer deposition. This is verified by the experimental result, which showed gentle morphological transformation on the VP substrate from a truncated triangle to a hexagon, and then back to a truncated triangle. By contrast, the multi-morphology and thickness of MoS₂ on the HP substrate result from the complex Mo concentration along the flow direction. Moreover, PL intensities of the MoS₂ domains deposited on the VP substrate are enhanced by 11.9-fold compared to the average intensity on the HP substrate. This result indicates the MoS₂ grown on the VP substrate has less intrinsic defects than that grown on the HP substrate. The combination of numerical simulation with experimental methods facilitates the visualization of invisible growth conditions, which provides effective guidance for using simulation results for other TMDC materials. Full article

Transition metal dichalcogenides (TMDCs), particularly molybdenum disulfide (MoS₂), have gained significant attention in the field of optoelectronics and photonics due to their unique electronic and optical properties. The integration of TMDCs with plasmonic materials allows to tailor the optical response and offers significant advantages for photonic applications. This study presents a novel approach to synthesize MoS₂-Au nanocomposites utilizing femtosecond laser ablation in liquid to achieve tunable optical properties in the near-infrared (NIR) region. By adjusting ablation and fragmentation protocols, we successfully synthesize various core–shell and core–shell–satellite nanoparticle composites, such as MoS₂/MoS_xO_y, MoS_xO_y/Au, and MoS₂/MoS_xO_y/Au. UV-visible absorption spectroscopy unveils considerable changes in the optical response of the particles depending on the fabrication regime due to structural modifications. Hybrid nanoparticles exhibit enhanced photothermal properties when subjected to NIR-I laser irradiation, demonstrating potential benefits for selective photothermal therapy. Our findings underscore that the engineered nanocomposites not only facilitate green synthesis but also pave the way for tailored therapeutic applications, highlighting their role as promising candidates in the field of nanophotonics and cancer treatment. Full article

The hybrid heterostructures formed between two-dimensional (2D) materials and organic molecules have gained great interest for their potential applications in advanced photonic and optoelectronic devices, such as solar cells and biosensors. Characterizing the interfacial structure and dynamic properties at the molecular level is essential for realizing such applications. Here, we report a time-resolved sum-frequency generation (TR-SFG) approach to investigate the hybrid structure of polymethyl methacrylate (PMMA) molecules and 2D transition metal dichalcogenides (TMDCs). By utilizing both infrared and visible light, TR-SFG can provide surface-specific information about both molecular vibrations and electronic transitions simultaneously. Our setup employed a Bragg grating for generating both a narrowband probe and an ultrafast pump pulse, along with a synchronized beam chopper and Galvo mirror combination for real-time spectral normalization, which can be readily incorporated into standard SFG setups. Applying this technique to the TMDC/PMMA interfaces yielded structural information regarding PMMA side chains and dynamic responses of both PMMA vibrational modes and TMDC excitonic transitions. We further observed a prominent enhancement effect of the PMMA vibrational SF amplitude for about 10 times upon the resonance with TMDC excitonic transition. These findings lay a foundation for further investigation into interactions at the 2D material/organic molecule interfaces. Full article

Chemical warfare agents (CWAs) are known as poor man’s bombs because of their small lethal dose, cheapness, and ease of production. Therefore, the highly sensitive and rapid detection of CWAs at room temperature (RT = 25 °C) is essential. In this paper, we have developed a resistive semiconductor sensor for the highly sensitive detection of CWAs at RT. The gas-sensing material is SnS₂/rGO nanosheets (NSs) prepared by hydrothermal synthesis. The lower detection limits of the SnS₂/rGO NSs-based gas sensor were 0.05 mg/m³ and 0.1 mg/m³ for the typical chemical weapons sarin (GB) and sulfur mustard (HD), respectively. The responsivity can reach −3.54% and −10.2% in 95 s for 1.0 mg/m³ GB, and in 47 s for 1.0 mg/m³ HD. They are 1.17 and 2.71 times higher than the previously reported Nb-MoS₂ NSs-based gas sensors, respectively. In addition, it has better repeatability (RSD = 6.77%) and stability for up to 10 weeks (RSD = 20.99%). Furthermore, to simplify the work of later researchers based on the detection of CWAs by two-dimensional transition metal sulfur compounds (2D-TMDCs), we carried out calculations of the SnS₂ NSs-based and SnS₂/rGO NSs-based gas sensor-adsorbing CWAs. Detailed comparisons are made in conjunction with experimental results. For different materials, it was found that the SnS₂/rGO NSs-based gas sensor performed better in all aspects of adsorbing CWAs in the experimental results. Adsorbed CWAs at a distance smaller than that of the SnS₂ NSs-based gas sensor in the theoretical calculations, as well as its adsorption energy and transferred charge, were larger than those of the SnS₂ NSs-based gas sensor. For different CWAs, the experimental results show that the sensitivity of the SnS₂/rGO NSs-based gas sensor for the adsorption of GB is higher than that of HD, and accordingly, the theoretical calculations show that the adsorption distance of the SnS₂/rGO NSs-based gas sensor for the adsorption of GB is smaller than that of HD, and the adsorption energy and the amount of transferred charge are larger than that of HD. This regularity conclusion proves the feasibility of adsorption of CWAs by gas sensors based on SnS₂ NSs, as well as the feasibility and reliability of theoretical prediction experiments. This work lays a good theoretical foundation for subsequent rapid screenings of gas sensors with gas-sensitive materials for detecting CWAs. Full article

Recently, two-dimensional materials have gained significant attention due to their outstanding properties such as high charge mobility, mechanical strength, and electrical characteristics. These materials are considered one of the most promising solutions to overcome the limitations of semiconductor technology and are being utilized in various semiconductor device research. In particular, molybdenum diselenide (MoSe₂) and tungsten diselenide (WSe₂) are actively being developed for device applications due to their high electron mobility, optical properties, and electrical characteristics. In this study, we fabricated MoSe₂ and WSe₂-based junction field-effect transistors (JFET) and further deposited two-dimensional materials on the same device to fabricate and compare JFETs with a gate-all-around (GAA) structure. The research results showed that the GAA-structure JFET exhibited performance improvements in drain current, subthreshold swing (SS) transconductance (gm), and mobility, achieving enhancements ranging from a minimum of 1.2 times to a maximum of 10 times compared to conventional JFET. Full article

Doping semiconductors is crucial for controlling their carrier concentration and enabling their application in devices such as diodes and transistors. Furthermore, incorporating magnetic dopants can induce magnetic properties in semiconductors, paving the way for spintronic devices without an external magnetic field. This review highlights recent advances in growing doped, two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors through various methods, like chemical vapor deposition, molecular beam epitaxy, chemical vapor transport, and flux methods. It also discusses approaches for achieving n- and p-type doping in 2D TMDC semiconductors. Notably, recent progress in doping 2D TMDC semiconductors to induce ferromagnetism and the development of quantum emitters is covered. Experimental techniques for achieving uniform doping in chemical vapor deposition and chemical vapor transport methods are discussed, along with the challenges, opportunities, and potential solutions for growing uniformly doped 2D TMDC semiconductors. Full article