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Giant Chemical Surface Enhancement of Coherent Raman Scattering on MoS <sub/>2</sub>
摘要： Raman spectroscopy is a powerful tool for molecular chemical analysis and bio-imaging, which shows an astonishing sensitivity when combined with a huge enhancement by the coherence and surface effects. Noble metal nanoparticles have been commonly used for the spontaneous surface-enhanced Raman scattering (SERS) and for the surface-enhanced coherent anti-Stokes Raman scattering (SECARS) spectroscopies, as they provide large enhancement factors via the electromagnetic and chemical mechanisms. Recently, two-dimensional (2D) semiconductors, such as monolayer molybdenum disulfide (MoS2), were used for the potential SERS applications as cheaper substrates compared to the noble metal nanoparticles. However, the coherent enhancement of SECARS on 2D materials has not been previously explored. Here we present the experimental SECARS measurements of pyridine-ethanol solutions containing 2D MoS2 nanocrystals with the giant chemical enhancement factor of 109 over coherent anti-Stokes Raman scattering (CARS), which is attributed to the charge transfer states and resonant MoS2 excitation. As a comparison, the SERS signals on MoS2 using incoherent nonresonant excitation show at least two orders of magnitude smaller enhancement. Time-resolved SECARS measurements directly reveal the increased vibrational dephasing rates which provide strong evidence for the charge transfer in the pyridine-ethanol-MoS2 system.
关键词： pyridine,MoS2,SERS,Raman,ethanol,CARS,SECARS
更新于2025-09-10 09:29:36
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Few-Layered MoS <sub/>2</sub> Nanoparticles Loaded TiO <sub/>2</sub> Nanosheets with Exposed {001} Facets for Enhanced Photocatalytic Activity
摘要： To improve the high charge carrier recombination rate and low visible light absorption of f001g facets exposed TiO2 [TiO2(001)] nanosheets, few-layered MoS2 nanoparticles were loaded on the surfaces of TiO2(001) nanosheets by a simple photodeposition method. The photocatalytic activities towards Rhodamine B (RhB) were investigated. The results showed that the MoS2–TiO2(001) nanocomposites exhibited much enhanced photocatalytic activities compared with the pure TiO2(001) nanosheets. At an optimal Mo/Ti molar ratio of 25%, the MoS2–TiO2(001) nanocomposites displayed the highest photocatalytic activity, which took only 30 min to degrade 50 mL of RhB (50 mg/L). The active species in the degradation reaction were determined to be h t and (cid:1)OH according to the free radical trapping experiments. The reduced charge carrier recombination rate, enhanced visible light utilization and increased surface areas contributed to the enhanced photocatalytic performances of the 25% MoS2–TiO2(001) nanocomposites.
关键词： MoS2,nanocomposites,TiO2,photocatalytic activity
更新于2025-09-10 09:29:36
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Direct Exfoliation of Natural SiO2-Containing Molybdenite in Isopropanol: A Cost Efficient Solution for Large-Scale Production of MoS2 Nanosheetes
摘要： The cost-effective exfoliation of layered materials such as transition metal dichalcogenides into mono- or few- layers is of significant interest for various applications. This paper reports the preparation of few-layered MoS2 from natural SiO2-containing molybdenite by exfoliation in isopropanol (IPA) under mild ultrasonic conditions. One- to six-layer MoS2 nanosheets with dimensions in the range of 50-200 nm are obtained. By contrast, MoS2 quantum dots along with nanosheets are produced using N-methyl-pyrrolidone (NMP) and an aqueous solution of poly (ethylene glycol)-block-poly (propylene glycol)-block-poly (ethylene glycol) (P123) as exfoliation solutions. Compared with molybdenite, commercial bulk MoS2 cannot be exfoliated to nanosheets under the same experimental conditions. In the exfoliation process of the mineral, SiO2 associated in molybdenite plays the role of similar superfine ball milling, which significantly enhances the exfoliation efficiency. This work demonstrates that isopropanol can be used to exfoliate natural molybdenite under mild conditions to produce nanosheets, which facilitates the preparation of highly concentrated MoS2 dispersions or MoS2 in powder form due to the volatility of the solvent. Such exfoliated MoS2 nanosheets exhibit excellent photoconductivity under visible light. Hence, the direct mild exfoliation method of unrefined natural molybdenite provides a solution for low-cost and convenient production of few-layered MoS2 which is appealing for industrial applications.
关键词： MoS2 nanosheet,liquid exfoliation,SiO2,photoelectric properties,natural molybdenite
更新于2025-09-10 09:29:36
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Optical Properties of Graphene/MoS2 Heterostructure: First Principles Calculations
摘要： The electronic structure and the optical properties of Graphene/MoS2 heterostructure (GM) are studied based on density functional theory. Compared with single-layer graphene, the bandgap will be opened; however, the bandgap will be reduced significantly when compared with single-layer MoS2. Redshifts of the absorption coefficient, refractive index, and the reflectance appear in the GM system; however, blueshift is found for the energy loss spectrum. Electronic structure and optical properties of single-layer graphene and MoS2 are changed after they are combined to form the heterostructure, which broadens the extensive developments of two-dimensional materials.
关键词： optical properties,graphene/MoS2 heterostructure,electronic structure
更新于2025-09-10 09:29:36
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Construct 3D Pd@MoS2-conjugated polypyrrole framworks Heterojunction with unprecedented photocatalytic activity for Tsuji-Trost reaction under visible light
摘要： Site-selective coupling of two photochemical system and one electron-transfer system to realize efficient charge separation and light absorption affords a promising route to enhance the photocatalytic efficiencies of semiconductors. To date, however, how to develop 3D porous multicomponent heterojunction systems for solar energy conversion in the visible and near-infrared (NIR) light region still remains a significant challenge. Here we report a simple technique for forming 3D Pd@MoS2-conjugated polypyrrole framworks (Pd@MoS2CPFs), in which two visible-light-active components (MoS2 nanosheets and polypyrrole) and the electron-transfer system (Pd) are spatially fixed, and the uniform Pd NPs are anchored in the MoS2CPFs. This 3D porous system exhibits good structural stability, high pore volume (0.31 cm3g-1), high surface area (105.24 m2/g), improved light absorption, and a long living electron-hole pair at the Pd@MoS2CPFs interface. Unexpectedly, we first found that the formed Pd@MoS2CPFs exhibited excellent photocatalytic activity and long-term stability for the direct Tsuji-Trost reaction between allylalcohol and 1,3-dicarbonyl under visible light at room temperature, far exceeding those of the single- and two-component systems, as a result of vectorial electron transfer driven by the one-step excitation of polypyrrole and MoS2. These results provide a promising new avenue in the design and fabrication of unique 3D porous multicomponent heterojunction for visible-light-induced efficient artificial photosynthetic systems.
关键词： MoS2,Pd nanoparticles,Tsuji–Trost reaction,synergic photocatalysis,polypyrrole
更新于2025-09-09 09:28:46
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Total-ionizing-dose effects and proton-induced displacement damage on MoS2-interlayer-MoS2 tunneling junctions
摘要： Tunneling-dominated charge transport is demonstrated in vertically stacked MoS2/interlayer/MoS2 heterostructures with Al2O3, h-BN and HfO2 dielectrics. All devices are highly resistant to 10-keV X-ray irradiation. Only small transient changes in X-ray-induced photocurrent are observed as a result of trap creation in the thin interlayer dielectric, with rapid passivation. Samples with Al2O3 and h-BN interlayer dielectrics show significant increases in conduction current during proton irradiation, due to displacement-damage-induced defects that lower the effective tunnel-barrier height. Density-functional-theory calculations provide insights into the pertinent defects. Devices with HfO2 interlayer dielectrics show great promise for use in radiation-tolerant, ultimately-scaled tunnel FETs.
关键词： 2 dimension,HfO2,proton irradiation,X-ray,DFT,h-BN,MoS2 tunnel junction
更新于2025-09-09 09:28:46
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Light-Shield Layers Free Photosensitive Inverters Comprising GaN-Drivers and Multi-Layered MoS2-Loads
摘要： Herein, GaN driver FETs with a high energy bandgap are employed in photosensitive inverters to eliminate light-shield layers (LSLs). This configuration exhibits full-swing characteristics of photosensitive inverters comprised of multi-layered MoS2 FETs loads in photosensitive pseudo-depletion mode. The GaN FETs provide both high current drivability and excellent photo-leakage immunity under visible light (Eg~3.1 eV). This allows the photosensitive inverters to be successfully operational without LSLs. The relative degradation (%) of voltage gain for photosensitive inverters with GaN drivers from dark to blue light exposure is improved from 67.7% to 53.0 %, as compared to previously reported MoS2 inverters with LSLs.
关键词： light-shield layers (LSLs),GaN FETs,photosensitive inverters,MoS2 FETs,biosensors,low noise margin
更新于2025-09-09 09:28:46
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Molybdenum Disulfid: Differentiating Polymorphs in Molybdenum Disulfide via Electron Microscopy (Adv. Mater. 47/2018)
摘要： The presence of rich polymorphs and stacking polytypes in molybdenum disulfide (MoS2) endows it with a diverse range of properties. This has stimulated a lot of interest in the unique properties associated with each polymorph. In article number 1802397, Kian Ping Loh and co-workers discuss the use of electron microscopy for identifying the atomic structures of several important polymorphs in MoS2 and establishing the correlation between structure and properties.
关键词： polymorphs,electron microscopy,stacking polytypes,molybdenum disulfide,MoS2
更新于2025-09-09 09:28:46
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CTAB-assisted synthesis of dissilient hollow spherical MoS2 for efficient hydrogen evolution
摘要： Dissilient hollow spherical MoS2 was prepared by one-step hydrothermal method using cetyltrimethyl ammonium bromide (CTAB) as a surfactant. The structure and morphology of the prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The addition of CTAB plays an important role in controlling the morphology of MoS2. As the amount of CTAB was increased, the morphology of MoS2 changed from flake to hollow sphere and finally broked up. Compared with MoS2 without CTAB and closed hollow spherical MoS2, the dissilient hollow spherical MoS2 showed better electrochemical performance in the hydrogen evolution reaction (HER) and good stability after 1000 cycles. We attribute this improvement to large specific surface area and many catalytic active sites of the dissilient hollow spheres. In general, the optimized catalyst exhibited an onset overpotential of 159 mV, a low Tafel slope of 65 mV dec-1, and relatively good stability.
关键词： HER,Dissilient,MoS2,CTAB,Hollow sphere
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE International Conference on Electron Devices and Solid State Circuits (EDSSC) - Shenzhen (2018.6.6-2018.6.8)] 2018 IEEE International Conference on Electron Devices and Solid State Circuits (EDSSC) - Carrier Injection Mechanism of Metal-MoS<inf>2</inf> Ohmic Contact in MoS<inf>2</inf> FETs
摘要： In order to enhance the carrier injection of MoS2 field effect transistors (FETs,) understanding the injection mechanism of metal-MoS2 contacts is essential. In this work, MoS2 (FETs) with Ti and Sc electrodes were fabricated and characterized, respectively. The carrier injection mechanism was studied from the perspective of the tunneling models. With the narrower barrier width, the Sc-MoS2 contact shows a different injection mechanism from that of Ti-MoS2, making Sc a promising improvement as MoS2 FETs electrodes.
关键词： Ohmic contact,MoS2,tunneling,field effect transistor (FET)
更新于2025-09-09 09:28:46