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A hierarchical sandwich-structured MoS2/SnO2/CC heterostructure for high photocatalysis performance
摘要： A sandwich-structured MoS2/SnO2/Carbon cloth (MoS2/SnO2/CC) photocatalyst was successfully synthesized through simple two-step hydrothermal method. The MoS2/SnO2/CC composite exhibited an excellent photocatalysis performance for degradation of RhB dye under visible light. A hierarchical double-layer heterostructure is formed via introducing carbon cloth substrates, which not only enhances the photocatalysis activity by accelerating electrons transfer rate and further intensifying electron-hole separation, but also is convenient for recycle. The specific photocatalysis, optical properties and photo-generated electron-hole transmission mechanism are discussed in detail. The improved photocatalysis performance of the MoS2/SnO2/CC suggests the possibilities of developing the multi-layer heterostructure for further photocatalysis applications.
关键词： MoS2/SnO2/CC,Double-layer heterostructure,Thin films,Nanocomposites,Carbon cloth,Photocatalysis
更新于2025-09-10 09:29:36
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MoS2/ZnO nanocomposites for efficient photocatalytic degradation of industrial pollutants
摘要： In the present work, molybdenum disulphide-zinc oxide (MoS2/ZnO) nanocomposites were synthesized via a simple dual step hydrothermal reduction method using hydrazine hydrate as a reducing agent. The as prepared nanocomposites have been characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman and photoluminescence (PL) spectroscopy. The structural and morphological analysis showed that particles are crystalline in nature and cubical in shape with an average size of ~22.5 nm.The nanocomposites were evaluated for photocatalytic property. The degradation analysis of industrial pollutants such as Novacron red Hunts- man (NRH) and methylene blue (MB) dye reveals that MoS2/ZnO nanocomposite is an efficient catalyst.
关键词： XPS,Novacron red Huntsman dye,Photocatalyst,Methylene blue,MoS2/ZnO
更新于2025-09-10 09:29:36
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Laser-induced improvement in tribological performances of surface coatings with MoS2 nanosheets and graphene
摘要： To deal with the corrosive property of bio-oil, laser-induced coatings were synthesized on the typical cylinder liner rubbing surfaces. Two nano-additives including MoS2 nanosheets and graphene were introduced into the coatings. The tribological performances of the coated surfaces were tested on a multifunctional cylinder liner-piston ring tribometer. The surfaces before and after sliding were characterized with modern surface analysis technology including Raman spectra, X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and etc. The results show that the nickel-based coated surfaces can effectively prevent the corrosion of the bio-oil. In addition, the laser-induced coatings had better antifriction and antiwear performances than the corresponding traditional electroless plating coatings. With the introduction of MoS2 nanosheets or graphene, the tribological performances of the coatings were further enhanced. Laser irradiation increased the concentration of the nano-additives in the coatings and the thickness of the tribo-layers, which accounted for their outstanding tribological performances.
关键词： Laser-induced coating,Graphene,Bio-oil,MoS2 nanosheets,Tribological performance
更新于2025-09-10 09:29:36
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crystals
摘要： Transition-metal dichalcogenides open novel opportunities for the exploration of exciting new physics and devices. As a representative system, 2H -MoS2 has been extensively investigated owing to its unique band structure with a large band gap, degenerate valleys, and nonzero Berry curvature. However, experimental studies of metastable 1T polytypes have been a challenge for a long time, and electronic properties are obscure due to the inaccessibility of single phase without the coexistence of 1T (cid:2), 1T (cid:2)(cid:2), and 1T (cid:2)(cid:2)(cid:2) lattice structures, which hinder the broad applications of MoS2 in future nanodevices and optoelectronic devices. Using Kx (H2O)yMoS2 as the precursor, we have successfully obtained high-quality layered crystals of the metastable 1T (cid:2)(cid:2)(cid:2)-MoS2 with √3a superstructure and metastable 1T (cid:2)-MoS2 with a × 2a superstructure, as evidenced by structural characterizations through scanning tunneling microscopy, Raman spectroscopy, and x-ray diffraction. It is found that the metastable 1T (cid:2)-MoS2 is a superconductor with onset transition temperature (Tc) of 4.2 K, while the metastable 1T (cid:2)(cid:2)(cid:2)-MoS2 shows either superconductivity with Tc of 5.3 K or insulating behavior, which strongly depends on the synthesis procedure. Both of the metastable polytypes of MoS2 crystals can be transformed to the stable 2H phase with mild annealing at about 70 °C in He atmosphere. These ?ndings provide pivotal information on the atomic con?gurations and physical properties of 1T polytypes of MoS2.
关键词： Transition-metal dichalcogenides,MoS2,metastable phases,superconductivity,structural characterization
更新于2025-09-10 09:29:36
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European Microscopy Congress 2016: Proceedings || Exciton and Plasmon Mapping at the Nanoscale
摘要： Excitons and plasmonic interactions, which are effectively responsible for the transfer of energy within devices such as solar cells, LEDs and semiconductor circuits, have been understood in theory for decades. However, the photophysical behaviour within materials has always been rather difficult to understand and be directly observed. Surface structure, localised thickness variations and presence of edges are bound to influence the macroscopic properties of the materials. Understanding the local surface structure and chemistry of these materials at the nanoscale is crucial in order to reach the full potential of the materials for real-life applications. Hence, there is a need to fully characterise the physical and chemical properties from the bottom up i.e. at the level of individual atoms and to map the optoelectronic properties where they happen. Due to recent technical improvements we can now access parts of the low loss electron energy-loss (LL EEL) spectra which had previously been inaccessible. This opens up new possibilities to study nanomaterials not only at unprecedented energy but also – contrary to bulk optical techniques – with a spatial resolution at the nanoscale, as described by Zhou, Dellby [1]. Although some significant progress has been made recently in unravelling the physical origins of the LL EEL features as shown by Tizei, Lin [2], significant gaps in our understanding of the signals and their origins remain. In the study presented here, we used for the first time a combination of experimental monochromated LL STEM EEL spectroscopy and theoretical calculations using time-dependent density functional theory (TDDFT) as well as the Bethe-Salpeter equation (BSE) to study the optical properties of MoS2 at the nanoscale with the aim to understand the origins of the peaks and regional variations of the complete LL EEL spectrum. We report that we identified and resolved as well as mapped mid-bandgap excitonic signals at ~1.88eV and at ~2.08eV on MoS2 flakes using monochromated LL EELS (figure 1) and confirmed their origin by BSE calculations; we also identified and mapped several plasmonic peaks (figure 1) using LL EELS combined with TD DFT. Furthermore, we observed great spatial variations in the LL EELS signal when comparing the edge to inner regions of a flake, i.e. with increasing number of layers, and we show how these can be largely attributed to beam geometry effects. The effects of the experimental set-up on the low loss EELS signal will be discussed.
关键词： STEM,2D materials,MoS2,TEM,spectroscopy,Low loss EELS
更新于2025-09-10 09:29:36
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Impact of Post-Lithography Polymer Residue on the Electrical Characteristics of MoS <sub/>2</sub> and WSe <sub/>2</sub> Field Effect Transistors
摘要： The residue of common photo- and electron-beam resists, such as poly(methyl methacrylate) (PMMA), is often present on the surface of 2D crystals after device fabrication. The residue degrades device properties by decreasing carrier mobility and creating unwanted doping. Here, MoS2 and WSe2 field effect transistors (FETs) with residue are cleaned by contact mode atomic force microscopy (AFM) and the impact of the residue on: 1) the intrinsic electrical properties, and 2) the effectiveness of electric double layer (EDL) gating are measured. After cleaning, AFM measurements confirm that the surface roughness decreases to its intrinsic state (i.e., ≈0.23 nm for exfoliated MoS2 and WSe2) and Raman spectroscopy shows that the characteristic peak intensities (E2g and A1g) increase. PMMA residue causes p-type doping corresponding to a charge density of ≈7 × 1011 cm?2 on back-gated MoS2 and WSe2 FETs. For FETs gated with polyethylene oxide (PEO)76:CsClO4, removing the residue increases the charge density by 4.5 × 1012 cm?2, and the maximum drain current by 247% (statistically significant, p < 0.05). Removing the residue likely allows the ions to be positioned closer to the channel surface, which is essential for achieving the best possible electrostatic gate control in ion-gated devices.
关键词： MoS2,ionic gating,WSe2,field effect transistor,polymer residue
更新于2025-09-10 09:29:36
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Layer-Dependent Dielectric Function of Wafer-Scale 2D MoS <sub/>2</sub>
摘要： Wafer-scale, high-quality, and layer-controlled 2D MoS2 films on c-sapphire are synthesized by an innovative two-step method. The dielectric functions of MoS2 ranging from the monolayer to the bulk are investigated by spectroscopic ellipsometry over an ultra-broadband (0.73–6.42 eV). Up to five critical points (CPs) in the dielectric function spectra are precisely distinguished by CP analysis, and their physical origins are identified in the band structures with the help of first-principles calculations. Results demonstrate that the center energies of these CPs exhibit intriguing layer dependency, which are interpreted by the intrinsic layer-dependent transitions in MoS2. Specially, the change in the imaginary part of the dielectric functions versus the thickness exhibits a “W” like curve, and the two valley bottoms appear at about four-layer and 10-layer respectively. These complex fluctuations are attributed to the alternating domination of the decreasing excitonic effect, the increasing joint density of states, and the mass density increase in relative thick MoS2 samples.
关键词： layer-dependent dielectric function,two-step method,spectroscopic ellipsometry,wafer-scale 2D MoS2
更新于2025-09-10 09:29:36
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Probing the Electronic Properties of Monolayer MoS <sub/>2</sub> via Interaction with Molecular Hydrogen
摘要： This work presents a detailed experimental investigation of the interaction between molecular hydrogen (H2) and monolayer MoS2 field effect transistors (MoS2 FET), aiming for sensing application. The MoS2 FET exhibits a response to H2 that covers a broad range of concentration (0.1–90%) at a relatively low operating temperature range (300–473 K). Most important, H2 sensors based on MoS2 FETs show desirable properties such as full reversibility and absence of catalytic metal dopants (Pt or Pd). The experimental results indicate that the conductivity of MoS2 monotonically increases as a function of the H2 concentration due to a reversible charge transferring process. It is proposed that such process involves dissociative H2 adsorption driven by interaction with sulfur vacancies in the MoS2 surface (VS). This description is in agreement with related density functional theory studies about H2 adsorption on MoS2. Finally, measurements on partially defect-passivated MoS2 FETs using atomic layer deposited aluminum oxide consist of an experimental indication that the VS plays an important role in the H2 interaction with the MoS2. These findings provide insights for future applications in catalytic process between monolayer MoS2 and H2 and also introduce MoS2 FETs as promising H2 sensors.
关键词： hydrogen gas sensor,gas interaction,hydrogen detection,monolayer MoS2,field effect transistors
更新于2025-09-10 09:29:36
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Defect Engineering of MoS? and Its Impacts on Electrocatalytic and Photocatalytic Behavior in Hydrogen Evolution Reactions
摘要： Molybdenum disulfide (MoS2) has been regarded as a favorable photocatalytic co-catalyst and efficient hydrogen evolution reaction (HER) electrocatalyst alternative to expensive noble-metals catalysts, owing to earth-abundance, proper bandgap, high surface area, and fast electron transfer ability. In order to achieve a higher catalytic efficiency, defects strategies such as phase engineering and vacancy introduction are considered as promising methods for natural 2H-MoS2 to increase its active sites and promote electron transfer rate. In this study, we report a new two-step defect engineering process to generate vacancies-rich hybrid-phase MoS2 and to introduce Ru particles at the same time, which includes hydrothermal reaction and a subsequent hydrogen reduction. Compositional and structural properties of the synthesized defects-rich MoS2 are investigated by XRD, XPS, XAFS and Raman measurements, and the electrochemical hydrogen evolution reaction performance, as well as photocatalytic hydrogen evolution performance in the ammonia borane dehydrogenation are evaluated. Both catalytic activities are boosted with the increase of defects concentrations in MoS2, which ascertains that the defects engineering is a promising route to promote catalytic performance of MoS2.
关键词： Electrocatalysis,Photocatalysis,Phase engineering,MoS2
更新于2025-09-10 09:29:36
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Enhancement of Photoelectrochemical Hydrogen Evolution of P-Type Silicon Nanowires Array by Loading MoS2
摘要： To improve photoelectrochemical properties of Si nanowires (SiNWs), MoS2/SiNWs is prepared via two-step method. SiNWs is synthesized by metal?catalyzed electroless etching (MCEE) method and MoS2 is subsequently deposited onto SiNWs through the direct thermal decomposition method. MoS2 is introduced as both light absorber and catalyst for hydrogen evolution reaction (HER). Moreover, it forms a heterojunction with SiNWs that contribute to the charge separation. Herein, MoS2/SiNWs attains excellent hydrogen evolution reaction (HER) catalysis with onset potential of 55 mV. A photocurrent density of 25 mA cm?2 at ?1.0 VRHE were achieved under simulated solar illumination, which is about 6 times higher than that of SiNWs, and the carrier concentration is increased by 100?fold. The enhanced photocatalytic activity of MoS2/SiNWs toward HER is attributed to the Schottky junction at the interface, which enhances the photo?generation of electron?hole pairs and suppresses the charge recombination, making them promising earth?abundant alternatives to noble metal?based photocathode for HER.
关键词： MoS2,P?type silicon wires array,Thermal decomposition,Hydrogen generation,Heterojunction
更新于2025-09-10 09:29:36