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Investigation of Surface Plasmon Resonance (SPR) in MoS2- and WS2-Protected Titanium Side-Polished Optical Fiber as a Humidity Sensor
摘要： In this paper, we report the effects of a side-polished fiber (SPF) coated with titanium (Ti) films in different thicknesses, namely 5 nm, 13 nm, and 36 nm, protected by a thin layer of transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2), which provide ultra-sensitive sensor-based surface plasmon resonance (SPR) covering from the visible to mid-infrared region. The SPF deposited with Ti exhibits strong evanescent field interaction with the MoS2 and WS2, and good optical absorption, hence resulting in high-sensitivity performance. Incremental increases in the thickness of the Ti layer contribute to the enhancement of the intensity of transmission with redshift and broad spectra. The findings show that the optimum thickness of Ti with 36 nm combined with MoS2 causes weak redshifts of the longitudinal localized surface plasmon resonance (LSPR) mode, while the same thickness of Ti with WS2 causes large blueshifts. The redshifts are possibly due to a reduced plasmon-coupling effect with the excitonic region of MoS2. The observed blueshifts of the LSPR peak position are possibly due to surface modification between WS2 and Ti. Changing the relative humidity from 58% to 88% only elicited a response in Ti/MoS2. Thus, MoS2 shows more sensitivity on 36-nm thickness of Ti compared with WS2. Therefore, the proposed fiber-optic sensor with integration of 2D materials is capable of measuring humidity in any environment.
关键词： tungsten disulfide (WS2),side-polished fiber (SPF),molybdenum disulfide (MoS2)
更新于2025-11-28 14:23:57
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Molybdenum Disulfide Catalytic Coatings via Atomic Layer Deposition for Solar Hydrogen Production from Copper Gallium Diselenide Photocathodes
摘要： We demonstrate that applying atomic layer deposition-derived molybdenum disulfide (MoS2) catalytic coatings on copper gallium diselenide (CGSe) thin film absorbers can lead to efficient wide band gap photocathodes for photoelectrochemical hydrogen production. We have prepared a device that is free of precious metals, employing a CGSe absorber and a cadmium sulfide (CdS) buffer layer, a titanium dioxide (TiO2) interfacial layer, and a MoS2 catalytic layer. The resulting MoS2/TiO2/CdS/CGSe photocathode exhibits a photocurrent onset of +0.53 V vs RHE and a saturation photocurrent density of ?10 mA cm?2, with stable operation for >5 h in acidic electrolyte. Spectroscopic investigations of this device architecture indicate that overlayer degradation occurs inhomogeneously, ultimately exposing the underlying CGSe absorber.
关键词： hydrogen evolution,molybdenum disulfide,photoelectrochemical water splitting,atomic layer deposition,copper gallium diselenide
更新于2025-11-19 16:56:35
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Controllable Synthesis of One-dimensional MoO3/MoS2 Hybrid Composites with their Enhanced Efficient Electromagnetic Wave Absorption Properties
摘要： One-dimensional MoO3/MoS2 hybrid composites were synthesized via hydrothermal synthesis; and the flexible MoO3/MoS2/PVDF nanocomposites were also controllable prepared by combining the composites with polyvinylidene fluoride (PVDF) matrix. The MoO3/MoS2/PVDF hybrids with low filler content (20 wt%) exhibited distinct microwave absorption properties in the range of 2 - 18 GHz. The minimum reflection loss can reach -38.5 dB at 8.7 GHz, and the reflection loss was less than -10 dB in the frequency range from 3.03 to 11.02 GHz with an absorber thickness of 2.0 - 5.0 mm. The MoO3/MoS2/PVDF nanocomposites exhibited better absorption properties than pure MoO3 and MoS2. The possible microwave absorbing mechanism was also discussed in detail.
关键词： microwave absorption,one-dimension,nanocomposites,Molybdenum disulfide,Molybdenum oxide
更新于2025-09-23 15:23:52
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Band Alignment of MoTe <sub/>2</sub> /MoS <sub/>2</sub> Nanocomposite Films for Enhanced Nonlinear Optical Performance
摘要： Band alignment is a key issue for the optoelectronics based on 2D layered transition metal dichalcogenides (TMDs) heterostructures. Herein, band alignment of MoTe2/MoS2 mixed heterostructure is measured with high-resolution X-ray photoelectron spectroscopy. The MoTe2/MoS2 heterostructure belongs to type-II heterostructure with the conduction band offset of 0.46 eV and the valence band offset of 0.9 eV. The stronger saturable absorption is observed in MoTe2/MoS2 heterostructure film compared with that of pure MoTe2 and MoS2 nanofilms at the same condition. An energy-level model combined with Runge–Kutta algorithm is used to understand the enhancement mechanism. It is found that the interlayer transition from MoTe2/MoS2 heterojunction plays an important role in the nonlinear optical enhancement. Meanwhile, band structure of MoTe2/MoS2 heterostructure is calculated by the first principles. The contributions of the MoTe2 and MoS2 to the heterojunction are almost equal and the valence band maximum and conduction band minimum exist in MoTe2 and MoS2 separately. This structure can form the interlayer carriers easily. The results suggest that the band alignment of TMDs paves the way for the type-II heterostructure for enhanced nonlinear response in the development of optical modulator, ultrafast laser mode lockers, saturable absorbers, and optical switches.
关键词： molybdenum disulfide (MoS2),band alignment,saturable absorption,heterostructure,molybdenum telluride (MoTe2)
更新于2025-09-23 15:23:52
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2D Material-Based Vertical Double Heterojunction Bipolar Transistors with High Current Amplification
摘要： The heterojunction bipolar transistor (HBT) differs from the classical homojunction bipolar junction transistor in that each emitter-base-collector layer is composed of a different semiconductor material. 2D material (2DM)-based heterojunctions have attracted attention because of their wide range of fundamental physical and electrical properties. Moreover, strain-free heterostructures formed by van der Waals interaction allows true bandgap engineering regardless of the lattice constant mismatch. These characteristics make it possible to fabricate high-performance heterojunction devices such as HBTs, which have been difficult to implement in conventional epitaxy. Herein, NPN double HBTs (DHBTs) are constructed from vertically stacked 2DMs (n-MoS2/p-WSe2/n-MoS2) using dry transfer technique. The formation of the two P–N junctions, base-emitter, and base-collector junctions, in DHBTs, was experimentally observed. These NPN DHBTs composed of 2DMs showed excellent electrical characteristics with highly amplified current modulation. These results are expected to extend the application field of heterojunction electronic devices based on various 2DMs.
关键词： 2D materials,tungsten diselenide,P–N junction,heterojunction bipolar transistor,molybdenum disulfide
更新于2025-09-23 15:23:52
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Ultra-sensitive surface plasmon resonance biosensor based on MoS2–graphene hybrid nanostructure with silver metal layer
摘要： The optical biosensors based on the plasmonic technology are an important research item in the field of biophotonics. The graphene–molybdenum disulfide (MoS2) based hybrid structures are very effective in designing and fabricating of the sensitive optical biosensors. In this paper, we propose a nanostructure Ag/MoS2/graphene as an optical biosensor with high performance and sensitivity. The proposed configuration for this surface plasmon resonance (SPR) optical biosensor is Kretschmann. Herein, the enhancement of sensitivity for the proposed SPR optical biosensor is investigated in different states. By determining of the numbers of MoS2 layer and the thickness of the metal layer, we increased the sensitivity of the proposed biosensor. The maximum sensitivity ~ 190°/RIU is achieved. For this ultra-sensitive SPR biosensor with maximum sensitivity, the numbers of MoS2 and graphene layer is 2 and the resonance wavelength is determined 680 nm.
关键词： Surface plasmon resonance,Molybdenum disulfide,Biosensor,Sensitivity,Graphene
更新于2025-09-23 15:23:52
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Hierarchical MoS2-Based Onion-Flower-like Nanostructures with and without Seedpods via Hydrothermal Route Exhibiting Low Turn-on Field Emission
摘要： Herein, we report facile hydrothermal synthesis of hierarchical MoS2 -based nanomorphs (displaying onion-flower-like features) with the primary focus on field-emitter applications. The synthesized nanostructures were characterized physicochemically to understand their basic structural and morphological features. Interesting nanoscale morphological evolution of onion-flower-like MoS2—from plain nanoflowers to those containing seedpods—is observed with the change in hydrothermal reaction time from 9 h to 21 h. Peculiarly, MoS2 nanomorphs with only onion-flower-like morphology displayed lower turn-on field value of 3.7 V/μm as compared to 4.2 V/μm for the nanoflowers containing seedpod-like particles. This might be attributed to the possibility of an easy electron conduction path available for the petals in plain nanoflowers, which may be impeded by the seedpod-like particles in the latter case.
关键词： Molybdenum disulfide,hierarchical nanostructures,field emission,hydrothermal
更新于2025-09-23 15:23:52
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Effect of Electron Irradiation on the Transport and Field Emission Properties of Few-Layer MoS <sub/>2</sub> Field-Effect Transistors
摘要： Electrical characterization of few-layer MoS2 based field effect transistors with Ti/Au electrodes is performed in the vacuum chamber of a scanning electron microscope in order to study the effects of electron beam irradiation on the transport properties of the device. A negative threshold voltage shift and a carrier mobility enhancement is observed and explained in terms of positive charges trapped in the SiO2 gate oxide, during the irradiation. The transistor channel current is increased up to three order of magnitudes after the exposure to an irradiation dose of 100e-/nm2. Finally, a complete field emission characterization of the MoS2 flake, achieving emission stability for several hours and a minimum turn-on field of ≈ 20 V/μm with a field enhancement factor of about 500 at anode-cathode distance of ~1.5 μm, demonstrates the suitability of few-layer MoS2 as two-dimensional emitting surface for cold-cathode applications.
关键词： electron beam irradiation,2D materials,field emission,molybdenum disulfide,field effect transistors
更新于2025-09-23 15:23:52
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Optical Imaging of Charges with Atomically Thin Molybdenum Disulfide
摘要： Mapping local surface charge distribution is critical to the understanding of various surface processes and also allows the detection of molecules binding to the surface. We show here that the optical absorption of monolayer MoS2 is highly sensitive to charge and demonstrate optical imaging of local surface charge distribution with this atomically thin material. We validate the imaging principle and perform charge sensitivity calibration with an electrochemical gate. We further show that binding of charged molecules to the atomically thin material leads to a large change in the image contrast, allowing determination of the charge of the adsorbed molecules. This capability opens possibilities for characterizing impurities and defects in two dimensional materials and for label-free optical detection and charge analysis of molecules.
关键词： electrochemical gate,monolayer molybdenum disulfide,protein binding,local charge imaging,charged impurities
更新于2025-09-23 15:23:52
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Probing the origin of lateral heterogeneities in synthetic monolayer molybdenum disulfide
摘要： Synthetic two-dimensional (2D) materials provide an opportunity to realize large-scale applications in next generation electronic and optoelectronic devices. One of the biggest challenges of synthetic 2D materials is the lateral heterogeneity such as non-uniform strain, composition and defect density. The electronic and optical properties are found to be not uniform in many cases, even within a single crystalline domain, potentially limiting synthetic 2D materials in advanced devices. In this work, we probe the origin of the widely observed lateral heterogeneities in synthetic monolayer MoS2. Epitaxial single crystalline domains (~10 μm) are optically homogeneous and uniform with 0.3~0.4% tensile strain, while misoriented domains (>20 μm) exhibit distinct photoluminescence (PL) emissions from the center to the edge, along with released strain at the center. Temperature-dependent Raman and PL mapping reveals that the center of non-epitaxial domains exhibits an enhanced PL due to increased defect density. Combining experiment and DFT, we hypothesize that two growth mechanisms, solid-solid and vapor-solid growth, may be responsible for the lateral heterogeneities. Density function theory (DFT) calculations suggest that oxygen defects can readily lead the loss of epitaxy, consistent with our observation of a MoOx core-shell structure that only exists in misoriented domains.
关键词： molybdenum disulfide,2D materials,heterogeneities
更新于2025-09-23 15:23:52