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TiO2 nanoparticles modified with 2D MoSe2 for enhanced photocatalytic activity on hydrogen evolution
摘要： As an emerging two-dimensional (2D) nanomaterial, 2D MoSe2 nanosheets has the advantages of wide light response and rapid charge migration ability. In this work, 2D MoSe2/TiO2 nanocomposites were successfully synthesized through a simple hydrothermal method. The microstructure and photocatalytic activity of the nanocomposites were systematically investigated and determined. The corresponding Raman peaks and crystal planes of MoSe2 were analysed by Raman spectroscopy and transmission electron microscopy respectively, demonstrating the successful combination of the MoSe2 nanosheets and TiO2 nanoparticles. UV-vis diffused re?ectance spectra demonstrated that the introduction of MoSe2 did increase the light absorption ability of the nanocomposites. A lower recombination of electrons and holes was demonstrated for the MoSe2/TiO2 heterojunction from photoluminescence results. The photocatalytic hydrogen evolution test showed that the hydrogen production rate was 4.9 mmol h?1 for the sample with 0.1 wt.% MoSe2, 2 times higher than that of bare TiO2. This work provides a novel strategy for improving the photocatalytic properties of semiconductor photocatalyst.
关键词： Water splitting,MoSe2 nanosheets,Two dimensional,Photocatalysis,TiO2
更新于2025-09-10 09:29:36
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Construction of direct Z-Scheme photocatalysts for overall water splitting using two-dimensional van der waals heterojunctions of metal dichalcogenides
摘要： The direct Z-scheme system constructed by two-dimensional (2D) materials is an efficient route for hydrogen production from photocatalytic water splitting. In the present work, the 2D van der Waals (vdW) heterojunctions of MoSe2/SnS2, MoSe2/SnSe2, MoSe2/CrS2, MoTe2/SnS2, MoTe2/SnSe2, and MoTe2/CrS2 are proposed to be promising candidates for direct Z-scheme photocatalysts and verified by first principles calculations. Perpendicular electric field is induced in these 2D vdW heterojunctions, which enhances the efficiency of solar energy utilization. Replacing MoSe2 with MoTe2 not only facilitates the interlayer carrier migration, but also improves the optical absorption properties for these heterojunctions. Excitingly, the 2D vdW MoTe2/CrS2 heterojunction is demonstrated, for the first time, to be 2D near-infrared-light driven photocatalyst for direct Z-scheme water splitting.
关键词： photocatalysis,direct Z-scheme systems,water splitting,two-dimensional van der Waals heterojunctions
更新于2025-09-10 09:29:36
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Tunable Schottky barrier width and enormously enhanced photoresponsivity in Sb doped SnS2 monolayer
摘要： Doping, which is the intentional introduction of impurities into a material, can improve the metal-semiconductor interface by reducing Schottky barrier width. Here, we present high-quality two-dimensional SnS2 nanosheets with well-controlled Sb doping concentration via direct vapor growth approach and following micromechanical cleavage process. X-ray photoelectron spectroscopy (XPS) measurement demonstrates that Sb contents of the doped samples are approximately 0.22%, 0.34% and 1.21%, respectively, and doping induces the upward shift of the Fermi level with respect to the pristine SnS2. Transmission electron microscopy (TEM) characterization exhibits that Sb-doped SnS2 nanosheets have a high-quality hexagonal symmetry structure and Sb element is uniformly distributed in the nanosheets. The phototransistors based on the Sb-doped SnS2 monolayers show n-type behavior with high mobility which is one order of magnitude higher than that of pristine SnS2 phototransistors. The photoresponsivity and external quantum efficiency (EQE) of Sb-SnS2 monolayers phototransistors are approximately three orders of magnitude higher than that of pristine SnS2 phototransistor. The results suggest that the method of reducing Shottky barrier width to achieve high mobility and photoresponsivity is effective, and Sb-doped SnS2 monolayer has significant potential in future nanoelectronic and optoelectronic applications.
关键词： doping,two-dimensional,SnS2,optoelectronics,Schottky barrier width
更新于2025-09-10 09:29:36
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High-performance black phosphorus field-effect transistors with long-term air-stability
摘要： Two-dimensional layered materials (2DLMs) are of considerable interest for high-performance electronic devices for their unique electronic properties and atomically thin geometry. However, the atomically thin geometry makes their electronic properties highly susceptible to the environment changes. In particular, some 2DLMs (e.g., black phosphorus (BP) and SnSe2) are unstable and could rapidly degrade over time when exposed to ambient conditions. Therefore, the development of proper passivation schemes that can preserve the intrinsic properties and enhance their lifetime represents a key challenge for these atomically thin electronic materials. Herein we introduce a simple, non-disruptive and scalable van der Waals passivation approach by using organic thin films to simultaneously improve the performance and air stability of BP field-effect transistors (FETs). We show that dioctylbenzothienobenzothiophene (C8-BTBT) thin films can be readily deposited on BP via van der Waals epitaxy approach to protect BP against oxidation in ambient conditions over 20 days. Importantly, the non-covalent van der Waals interface between C8-BTBT and BP effectively preserves the intrinsic properties of BP, allowing us to demonstrate high-performance BP FETs with a record-high current density of 920 μA/um, hole drift velocity over 1 ⅹ 107 cm/s, and on/off ratio of 104~107 at room temperature. This approach is generally applicable to other unstable two-dimensional (2D) materials, defining a unique pathway to modulate their electronic properties and realize high-performance devices through hybrid heterojunctions.
关键词： black phosphorus,saturation velocity,saturation current density,two-dimensional materials,passivation,field effect transistors
更新于2025-09-10 09:29:36
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The Evolution of Two-Dimensional Mo <sub/> 1- <i>x</i> </sub> W <sub/><i>x</i> </sub> S <sub/>2</sub> Alloy-Based Vertical Heterostructures with Various Composition Ranges <i>via</i> Manipulating the Mo/W Precursors
摘要： Two-dimensional (2D) layered transition metal dichalcogenides (TMDCs), for example, MoS2 and WS2, are gaining widespread attention at present due to their distinct physical properties. Developing the deeper potential of 2D TMDCs demands fine spatial modulation of chemical compositions and electrical performance to produce desired heterostructures. In this study, we report a one-step chemical vapor deposition (CVD) synthesis of compositionally tunable WS2-Mo1-xWxS2 vertical heterostructures by adjusting the stacking sequence of Mo/W films as the precursors. Detailed Raman and photoluminescence analyses confirm that as-grown samples present clear structural and optical modulations. The evolution of these heterostructures with different composition ranges is discussed on the basis of the tunable vapor pressure. The present study provides an alternative strategy to facilitate the development of 2D semiconductor heterostructures, which is an essential step towards realizing functional electronics and optoelectronics.
关键词： Heterostructures,Optical properties,Two-dimensional materials,Chemical vapor deposition,Transition metal dichalcogenides
更新于2025-09-10 09:29:36
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Two dimensional sinusoidal Ag nanograting exhibits polarization-independent surface-enhanced Raman spectroscopy and its surface plasmon polariton and localized surface plasmon coupling with Au nanospheres colloids
摘要： A reproducible surface‐enhanced Raman scattering (SERS) substrate based on two dimensional (2D) sinusoidal Ag nanograting is presented. This SERS substrate with large area can be easily fabricated by maskless laser interference photolithography. The potential SERS polarization‐independent performance of 2D sinusoidal Ag nanograting is deduced by finite difference time domain and demonstrated by SERS detection experiments. A double‐enhanced Raman scattering (DERS) substrate by coupling 2D sinusoidal Ag nanograting with Au nanospheres colloids is created. With the optimal DERS substrate, SERS enhancement factor can be 10 orders of magnitude as possible. The DERS substrate was fabricated and an extra SERS effect was proved by experiments. This DERS substrate will be fabricated in a microfluidics‐based sensor in the next work and used for in situ, real‐time, continuous monitoring of trace water soluble gas‐phase or airborne agents, such as trace explosives in air.
关键词： surface plasmon polaritons,surface enhanced Raman scattering,localized surface plasmons,two dimensional sinusoidal nanograting,polarization‐independent
更新于2025-09-10 09:29:36
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Fast identification of crystalline orientation of anisotropic two-dimensional materials using scanning polarization modulation microscopy
摘要： In this work, we have demonstrated that scanning polarization modulation microscopy (SPMM) provides a fast method for the identification of crystalline orientation of anisotropic two-dimensional (2D) materials. Using home-built 532 nm excited transmission SPMM, we identified the crystalline orientation of 2D orthorhombic black phosphorus, monoclinal 1T0-MoTe2, and triclinic ReS2 by measuring signals in only two incident polarization directions. So, it took just a few seconds to identify the crystalline orientation of anisotropic 2D materials. Our studies revealed that the SPMM method could be applied to arbitrary anisotropic 2D materials when selecting a suitable wavelength.
关键词： black phosphorus,1T0-MoTe2,scanning polarization modulation microscopy,anisotropic two-dimensional materials,ReS2,crystalline orientation
更新于2025-09-10 09:29:36
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Modeling charge density in AlGaN/AlN/InGaN/GaN-based double heterostructures including InGaN layer strain relaxation
摘要： An analytical model is presented to calculate the two-dimensional electron gas (2DEG) density and barrier height of bare surface AlGaN/AlN/InGaN/GaN double heterostructures, which use InGaN as the conducting layer. The basic model is derived from electrostatic analysis of the di?erent material interfaces. The e?ect of strain relaxation in the InGaN layer is also incorporated here. Further, the impact of a two-dimensional hole gas at the InGaN/GaN interface, formed when the InGaN layer thickness is high, has been considered. The presented results are seen to agree with the available experimental results. Thus, this model can be a useful tool in the design and modeling of InGaN-based III-nitride heterostructures.
关键词： two-dimensional hole gas,AlGaN/InGaN/GaN heterostructure,strain relaxation,two-dimensional electron gas
更新于2025-09-09 09:28:46
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Nonlinear optical susceptibility of atomically thin WX2 crystals
摘要： We have studied tungsten diselenide (WSe2) and tungsten disulfide (WS2) monolayer materials in second harmonic generation spectroscopy and microscopy experiments. Ultra-broadband continuum pulses served as the fundamental beam while its second harmonic spectrum in the visible and ultraviolet (UV) range was detected and analyzed with a better than 0.3 nm spectral resolution (< 2 meV). We provide dispersion data and absolute values for χ(2) for the materials within a photon energy range of 2.3–3.2 eV. Fine spectral features that were detected within the dispersion data for the optical nonlinearities indicate the impact of near bandgap exciton transitions. The fundamental bandgap of 2.35 eV and exciton binding energy of 0.38 eV were determined from the measurements for WS2 monolayers while the corresponding values in WSe2 monolayers were 2.22 eV and 0.71 eV. Ranges for the absolute values of the sheet nonlinearity for WS2 and WSe2 are shown to be 0.58–1.65 × 10?18 m2/V and 0.21–0.92 × 10?18 m2/V, correspondingly.
关键词： Nonlinear spectroscopy and microscopy,Transition metal dichalcogenides,Two-dimensional semiconductors,Second harmonic generation,Optical nonlinearity in semiconductors,Monolayer crystals,Optics at interfaces
更新于2025-09-09 09:28:46
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Synthesis of Ultrathin Few-Layer 2D Nanoplates of Halide Perovskite Cs <sub/>3</sub> Bi <sub/>2</sub> I <sub/>9</sub> and Single-Nanoplate Super-Resolved Fluorescence Microscopy
摘要： The discovery of new two-dimensional (2D) perovskite halides has created sensation recently because of their structural diversity and intriguing optical properties. The toxicity of Pb-based perovskite halides led to the development of Pb-free halides. Herein, we have demonstrated a one-pot solution-based synthesis of 2D ultrathin (～1.78 nm) few-layer (2?4 layers) nanoplates (300?600 nm lateral dimension), nanosheets (0.6?1.5 μm), and nanocrystals of layered Cs3Bi2I9 by varying the reaction temperature from 110 to 180 °C. We have established a mechanistic pathway for the variation of morphology of Cs3Bi2I9 with temperature in the presence of organic capping ligands. Further, we have synthesized the bulk powder of Cs3Bi2I9 by mechanochemical synthesis and liquid-assisted grinding and crystalline ingot by vacuum-sealed tube melting. 2D nanoplates and bulk Cs3Bi2I9 demonstrate optical absorption edge along with excitonic transition. Photoluminescence properties of individual nanoplates were studied by super-resolution ?uorescence imaging, which indicated the blinking behavior down to the level of an individual Cs3Bi2I9 nanoplate along with its emission at the far-red region and high photostability.
关键词： ultrathin nanoplates,super-resolution ?uorescence imaging,two-dimensional (2D) perovskite halides,Pb-free halides,Cs3Bi2I9
更新于2025-09-09 09:28:46