Molybdenum Disulfide Nanosheets Research Articles

Cobalt ferrite decoration of molybdenum disulfide nanosheets; development of a nanocomposite-mediated hyperthermia method

The aims were to characterize MoS2/CoFe2O4 nanocomposite and investigate its thermal therapy efficiency on cancerous (MCF-7) and normal (MCF-10A) human breast cells. Magnetic nanocomposites (MNCs) characterized by scanning/transmission electron microscopy (SEM/TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM) techniques. TEM and SEM techniques showed MoS2/CoFe2O4 MNCs had an average size of 17±4 nm with almost spherical morphology. Magnetic properties of MNC measured by VSM, which resulted in specific loss power (SLP) of 766.61 W/g at 300 K. Cytotoxicity of MoS2/CoFe2O4 nanocomposites in MCF-7 and MCF-10A cell lines remained insignificant until 48 hours, which confirms its biocompatibility. Low concentration (200 ug/mL) of MoS2/CoFe2O4 was exposed to the low-frequency alternative magnetic field (f = 150 kHz, H = 31.16 mT) in a way that delivery of thermal ablation via magnetic fluid hyperthermia (MFH) occurred exclusively in cancerous (MCF-7) cells.

Electrochemical exfoliation of molybdenum disulfide nanosheets for high-performance supercapacitors

Two-dimensional (2D) molybdenum disulfide (MoS2) nanomaterials have emerged as promising candidates for constructing excellent supercapacitors, but the lack of large-scale, efficient and low-cost methods for preparing MoS2 nanosheets severely hinders its practical application. This study demonstrates an accessible and efficient approach for electrochemical exfoliating bulk MoS2 into high-quality MoS2 nanosheets with size distribution in the range of 1–3 μm and a thickness of several nanometers in an easily available inorganic salt solution. Furthermore, we construct symmetric all-solid-state supercapacitors based on exfoliated MoS2 nanosheets. The 2D structure will provide stable channels to facilitate the intercalation/desorption of ions during charge and discharge, and to a certain extent can prevent deposition and agglomeration. Therefore, compared with the unexfoliated MoS2, as-prepared MoS2 nanosheets show great improvement in supercapacitor performance (the specific capacitance increases from the original 130 F g−1 to 215 F g−1 at 5 A g−1, for instance). In detail, the electrode possesses a specific capacitance of 285 F g−1 at a current density of 2 A g−1 and maintains the great capacitance retention of 83.8% at 8 A g−1. Moreover, the supercapacitor exhibits a high energy density of 136.8 Wh kg−1 at a power density of 2550 Wh kg−1. This work provides basic research on the preparation of 2D nanomaterials by electrochemical exfoliation.

High-yield preparation of molybdenum disulfide/polypyrrole hybrid nanomaterial with non-covalent interaction and its supercapacitor application

• High-yield of molybdenum disulfide (MoS 2 ) nanosheets could be prepared by simple grinding and sonochemical exfoliation. • Polypyrrole/MoS 2 (MPY) hybrid was synthesized via a chemical oxidative polymerization according to pyrrole content. • Non-covalent Mo–N bonding of MPY made it possible to have lowered interfacial resistance and improved surface conductivity. • MPY electrodes showed enhanced specific capacitance and electrochemical stability for pseudocapacitive behavior. Molybdenum disulfide (MoS 2 ) incorporated with a conducting polymer can be a promising nanomaterial for use as low-cost electrodes in supercapacitors. MoS 2 nanosheets are generally prepared by the high-pressure hydrothermal method, which has a few drawbacks such as low exfoliation yield, safety issues, and long-time processing. Herein, we report a simple and effective method for the high-yield (~72.5%) preparation of a MoS 2 /polypyrrole (MPY) hybrid nanomaterial via sonochemical exfoliation of ground bulk MoS 2 in a polar aprotic solvent and subsequent chemical oxidative polymerization of pyrrole (PY) onto the MoS 2 nanosheets. The strong non-covalent Mo–N bonding lowers the interfacial resistance, and the morphology of polypyrrole (PPY) can be easily controlled by varying the PY content. The MPY hybrid nanomaterial exhibited a maximum surface conductivity of 991 S sq., which is very high compared to that of pristine MoS 2 nanosheet (~3.6 × 10 –7 S sq.). When used in supercapacitors, the specific capacitance of the hybrid nanomaterial is 312 F g –1 . Thus, improved capacitance retention with increase in the scan rate and enhanced diffusion process during electrochemical reactions result in good supercapacitor performance, which is important for the mass production of energy-storage devices.

MoS2 nanosheets uniformly grown on polyphosphazene-derived carbon nanospheres for lithium-ion batteries

With the discovery and application of graphene, layered inorganic materials such as MoS2 has attracted increasing interest. However, the rational design of a novel electrode structure with a high capacity, fast charge/discharge rate, and long cycling lifetime remains a great challenge. Herein, we report a method of growing layered MoS2 nanosheets on polyphosphazene microspheres. The uniform polyphosphazene microspheres have a rich and uniform hydroxyl structure on the surface, which are effective as hard templates for the growth of two-dimensional MoS2 nanosheets. The uniform adsorption of the initial molybdenum disulfide nanosheets induced a uniform growth, hence a high stable electrochemical performance. Moreover, the obtained hollow carbon microspheres not only exhibited higher electrical conductivity, but also stronger the structural stability. The composites shows a high capacity (882 mAh•g−1) at a current density of 2 A•g−1 and a long cycle life of 1000 cycles with 85 % capacity retention as well. The composites might be a promising MoS2-based anode material for Li-ion battery applications.

Amphiphilic Rhamnolipid Molybdenum Disulfide Nanosheets for Oil Recovery

Much attention has been directed toward amphiphilic nanosheets in diverse applications owing to their remarkable properties. In this work, the rhamnolipid-molybdenum disulfide nanosheets, environme...

Improving Lithium‐Ion Diffusion Kinetics in Nano‐Si@C Anode Materials with Hierarchical MoS2 Decoration for High‐Performance Lithium‐Ion Batteries

AbstractA carbon layer on a silicon anode not only acts as a structural buffer to alleviate the tremendous volume expansion of silicon, but also enhances electrical conductivity. However, the carbon layer cannot improve the diffusion kinetics of Li+. Molybdenum disulfide (MoS2) nanosheets are introduced on the outermost layer of yolk‐shell silicon@carbon to design urchin‐like hierarchical anode materials, which is of great benefit in structural stability. By contrast with the yolk‐shell silicon@carbon structure, the diffusion coefficient of Li+ is improved, with 3.27 times greater performance during the delithiation processes and 2.04 times greater during the lithiation process with urchin‐like hierarchical structure, showing robust diffusion kinetics. Moreover, the MoS2 nanosheets are able to enhance the delithiation reversibility of Li15Si4 alloy formed during lithiation process. Because the MoS2 nanosheets promote the structural stability, delithiation reversibility, and diffusion kinetics of Li+ during lithiation/delithiation processes, the prepared hierarchical Si@C@MoS2 composites exhibit a high reversible specific capacity of 1025 mAh g−1 with a capacity retention of approximately 81 % after 400 cycles at a current density of 1000 mAh g−1, and the reversible specific capacity can reach 819 mAh g−1 even under a high rate of 5000 mA g−1.

The reinforcing role of 2D graphene analogue MoS2 nanosheets in multiscale carbon fibre composites: Improvement of interfacial adhesion

In this study, a novel scalable method based on hydrothermal-assisted ball milling was used to simultaneously synthesize and amino-functionalize molybdenum disulfide nanosheets with diaminodiphenyl sulfone (DDS-MoS2). This process resulted in the production of the functionalized nanosheets with a lateral dimension of ~600–900 nm and thickness of ~2–6 nm without requiring a lithium intercalation step. The inverse gas chromatography results revealed that total surface energies of the nanosheets significantly increased after DDS functionalization, making them highly compatible with epoxy resin. Epoxy nanocomposites containing 0.5 wt% of DDS-MoS2 nanosheets showed ~30% and ~28% increases in tensile and flexural strengths, respectively. Additionally, ~16% and ~12% enhancements in tensile and flexural modulus, respectively, were observed in these nanocomposites. The inclusion of DDS-MoS2/epoxy resin in carbon fibre composites led to the fabrication of multiscale nanocomposites with improved mechanical properties. In these multiscale nanocomposites, flexural modulus and strength were considerably improved by ~33.7% and ~29.5%, respectively. Compared to other two-dimensional nanomaterials, such as nanoclay and graphene derivatives, DDS-MoS2 nanosheets showed promising behaviour for both epoxy nanocomposites and multiscale carbon fibre nanocomposites. These achievements could be associated with the synergistic effect of DDS-MoS2 in both promoting the interfacial stress transfer and the energy dissipation through different crack retardation mechanisms.

Enhanced photocatalytic activity of plasmonic Au nanoparticles incorporated MoS2 nanosheets for degradation of organic dyes

In the present paper, we have investigated the effect of plasmonic gold nanoparticles (Au NPs) decoration on the photocatalytic efficiency of molybdenum disulfide (MoS2) nanosheets. The Au NPs are grown on the surfaces of chemically exfoliated MoS2 nanosheets by chemical reduction method with four different concentrations. The resulting Au-MoS2 nanostructures (NSs) are then characterized by X-ray diffractometer, Raman spectrometer, absorption spectrophotometer, field emission scanning electron microscopy, energy dispersive X-ray, and transmission electron microscopy (TEM). Sizes of the exfoliated MoS2 nanosheets are ~ 700 nm. In addition, the sizes of Au nanoparticles increase from 8.02 ± 2.03 nm to 9.81 ± 3.18 nm with the increase in concentrations of Au ions, as revealed by TEM imaging. Exfoliated MoS2 and Au-MoS2 NSs are used to study the photocatalytic degradation of organic dyes, methyl red (MR) and methylene blue (MB). Under UV–Visible light irradiation, pristine MoS2 shows photodegradation efficiencies in the range of 30.0% to 46.9% for MR, and 23.3% to 44.0% for MB, with varying exposure times of 30 to 120 min. However, Au-MoS2 NSs with the sets having maximum Au NPs concentrations, show enhanced degradation efficiencies from 70.2 to 96.7% for MR, and from 65.2 to 94.3% for MB. The degradation rate constants vary from − 0.5660 to − 1.5551 min−1 for MR dye, and vary from − 0.3587 to − 1.2614 min−1 for MB dye. The multi-fold enhancements of degradation efficiencies for both the dyes with Au-MoS2 NSs, can be attributed to the presence of Au NPs acting as charge trapping sites in the NSs. We believe this type of study could provide a way to battle the ill-effects of environmental degradation that pose a major threat to humans as well as biodiversity. This study can be further extended to other semiconducting materials in conjugation with two dimensional materials for photocatalytic treatment of polluted water.

Hydrophobic Two-Dimensional MoS2 Nanosheets Embedded in a Polyether Copolymer Block Amide (PEBA) Membrane for Recovering Pyridine from a Dilute Solution.

A two-dimensional molybdenum disulfide (MoS2) nanosheet, as a new type of inorganic material with high hydrophobicity and excellent physicochemical stability, holds great application potential in the preparation of a high separation performance organic–inorganic hybrid membrane. In this work, high hydrophobic MoS2 was embedded in hydrophobic polyether copolymer block amide (PEBA) to prepare PEBA/MoS2 organic–inorganic hybrid membranes. The structure, morphology, and hydrophobicity of the hybrid membrane were characterized by scanning electron microscopy, thermogravimetric analysis, contact angle goniometry, X-ray diffraction, infrared spectroscopy analysis, and atomic force microscopy. The effect of embedding of MoS2 on the swelling degree and pervaporation separation performance of the PEBA/MoS2 hybrid membrane was studied with a 1.0 wt % pyridine dilute solution. The results indicated that with increasing the MoS2 content, the separation factor of PEBA/MoS2 increased first and then decreased, while it showed a downward trend in the permeation flux. When the MoS2 content in the PEBA/MoS2 hybrid membrane was 10.0 wt %, the permeation flux was 83.4 g m–2 h–1 (decreased by 21.5% compared with the pure PEBA membrane), and the separation factor reached a maximum value of 11.11 (increased by 37.6% compared with the pure PEBA membrane). Meanwhile, the effects of feed temperature on the pervaporation separation performance of PEBA/MoS2 hybrid membranes were also studied. In addition, as the PEBA/MoS2 hybrid membrane has excellent thermal stability, it is expected to be a promising material for recovering pyridine from wastewater.

Fabrication of 3D structured composites of crumpled graphene, polyaniline and molybdenum disulfide nanosheets for high performance alkali metal ion storage

Recently, there is a growing concern for high performance energy storage devices in many applications where a lot of energy needs to be either stored or delivered. Here, we introduce a facile strategy to fabricate effectively combined 3D structured composites of crumpled graphene (CGR), polyaniline (PANI) and molybdenum disulfide (MoS2) for potential application to high performance alkali metal ion storage such as sodium and lithium ion storage. 2D graphene oxides, polyaniline, and physically exfoliated 2D MoS2 were combined to fabricate 3D structured CGR/PANI/MoS2 composites by aerosol self-assembly process and post heat treatment. Overall morphology of composites looked like crumpled paper ball with an average diameter of ~5 μm. MoS2 and PANI were attached on the surface of the graphene, which supported an accessible surface area and provided a path for electron transfer. Synergistic effect by the combination of the three functional materials resulted in outstanding electrochemical performance as sodium-ion storage in terms of storage capacity (328 F g−1 at 1 A g−1), good rate capability (282 F g−1 at 10 A g−1), and cycle performance (95%, after 1000 cycles). Even lithium-ion storage application, the CGR/PANI/MoS2 also delivered a high specific capacity of 470 mAh g−1 after 100 cycles.

In situ detection of plasma exosomal microRNA for lung cancer diagnosis using duplex-specific nuclease and MoS2 nanosheets.

MicroRNAs (miRNAs) encapsulated in tumor-derived exosomes are becoming ideal biomarkers for the early diagnosis and prognosis of lung cancer. However, the accuracy and sensitivity are often hampered by the extraction process of exosomal miRNA using traditional methods. Herein, this study developed a fluorogenic quantitative detection method for exosomal miRNA using the fluorescence quenching properties of molybdenum disulfide (MoS2) nanosheets and the enzyme-assisted signal amplification properties of duplex-specific nuclease (DSN). First, a fluorescently-labeled nucleic acid probe was used to hybridize the target miRNA to form a DNA/RNA hybrid structure. Under the action of the DSN, the DNA single strand in the DNA/RNA hybrid strand was selectively digested into smaller oligonucleotide fragments. At the same time, the released miRNA target triggers the next reaction cycle, so as to achieve signal amplification. Then, MoS2 was used to selectively quench the fluorescence of the undigested probe leaving the fluorescent signal of the fluorescently-labeled probe fragments. The fluorometric signals for miRNA-21 had a maximum excitation/emission wavelength of 488/518 nm. Most importantly, the biosensor was then applied for the accurate quantitative detection of miRNA-21 in exosome lysates extracted from human plasma and this method was able to successfully distinguish lung cancer patients from healthy people. This biosensor provides a simple, rapid, and a highly specific quantitative method for exosomal miRNA and has promising potential to be used in the early diagnosis of lung cancer.

The antibacterial activities of MoS2 nanosheets towards multi-drug resistant bacteria.

We demonstrated that molybdenum disulfide (MoS2) nanosheets can be an excellent solar disinfection agent for multi-drug resistant (MDR) bacteria with disinfection efficiencies >99.9999% in only 30 min. Distinct from other reactive oxygen species (ROS)-dependent photocatalysts, both ROS generation and size decrease contributed to the high antibacterial efficiencies of MoS2.

An ion-selective crown ether covalently grafted onto chemically exfoliated MoS2 as a biological fluid sensor.

We describe the basal plane functionalization of chemically exfoliated molybdenum disulfide (ce-MoS2) nanosheets with a benzo-15-crown-5 ether (B15C5), promoted by the chemistry of diazonium salts en route to the fabrication and electrochemical assessment of an ion-responsive electrode. The success of the chemical modification of ce-MoS2 nanosheets was investigated by infrared and Raman spectroscopy, and the amount of the incorporated crown ether was estimated by thermogravimetric analysis. Raman spatial mapping at on-resonance excitation allowed us to disclose the structural characteristics of the functionalized B15C5-MoS2 nanosheets and the impact of basal plane functionalization to the stabilization of the 1T phase of ce-MoS2. Morphological investigation of the B15C5-MoS2 hybrid was implemented by atomic force microscopy and high-resolution transmission electron microscopy. Furthermore, fast-Fourier-transform analysis and in situ energy dispersive X-ray spectroscopy revealed the crystal lattice of the modified nanosheets and the presence of crown-ether addends, respectively. Finally, B15C5-MoS2 electrodes were constructed and evaluated as ion-selective electrodes for sodium ions in aqueous solution and an artificial sweat matrix.

Facile synthesis of vacancy-induced 2H-MoS2 nanosheets and defect investigation for supercapacitor application.

In this paper, a 2D molybdenum disulfide (MoS2) nanosheet is prepared via a one-step hydrothermal method as electrode material for supercapacitors. Meanwhile, a series of MoS2−x nanostructures with sulfur vacancies have been successfully obtained in an Ar/H2 mixed atmosphere at different annealing temperatures. The prepared materials were characterized by XRD, HR-TEM, Raman and XPS to identify their morphology and crystal properties. MoS2−x assembled by interconnected nanosheets (MoS2−x-700) provides a maximum specific capacitance of 143.12 F g−1 at a current density of 1.0 A g−1 with 87.1% of initial capacitance reserved after 5000 cycles. The outstanding performance of the annealed MoS2−x nanosheets in sodium storage is mainly attributed to the synergistic effect of the unique interconnected structure and the abundant active vacancy generated by the sulfur vacancies. Atomic models of sulfur vacancy defects on the basal plane, Mo-edge and S-edge were established and the electronic properties of MoS2−x were further evaluated assisted by first principles theory. DFT calculation results show that sulfur vacancy defects can provide additional empty states near the Fermi level and induce unpaired electrons, thus increasing the carrier density and improving electrical conductivity. Our findings in this work provide experimental and theoretical evidence of improving the electrochemical performance of 2H-MoS2 nanosheets by annealing treatment.

A hybrid polyvinyl alcohol/molybdenum disulfide nanosheet hydrogel with light-triggered rapid self-healing capability.

A hybrid self-healing hydrogel (PM hydrogel), based on polyvinyl alcohol (PVA) and chemically exfoliated molybdenum disulfide (ce-MoS2) nanosheets, was prepared by a simple freeze-thaw method. Due to the excellent photothermal conversion properties of ce-MoS2 nanosheets, the PM hydrogel self-repaired rapidly under near infrared (NIR) light irradiation for only 3 min with a high healing efficiency of 91.8 ± 3.3%. The PVA content, ce-MoS2 nanosheet loading and light irradiation time played important roles in the self-healing performance. Additionally, the PM hydrogel also revealed good self-healing properties with a healing efficiency of 60.6 ± 3.6% after the cut surfaces were separated for 24 h. The present approach provides an effective strategy for fabricating fast light-triggered hydrogen-bond based self-healing systems. The as-prepared hybrid PM hydrogel has great potential as a soft biomaterial for long-term applications due to its biocompatibility and self-healing capability.

Fe doped MoS2/polypyrrole microtubes towards efficient peroxidase mimicking and colorimetric sensing application.

Molybdenum disulfide (MoS2) nanosheets have been found to exhibit intrinsic peroxidase-like activity that could be applied in colorimetric sensing platforms. However, their poor conductivity and few exposed edge sites often lead to poor catalytic activity, impeding the application of MoS2 nanosheets in enzyme-like catalysis. Here, a novel strategy was developed to selectively deposit Fe-doped MoS2 nanosheets on polypyrrole microtubes to obtain Fe-MoS2@PPy microtubes to address these issues. In the synthesized Fe-MoS2@PPy microtubes, PPy microtubes can not only be used as a conductive support to promote the electron transfer, but also greatly alleviate the aggregations of MoS2 nanosheets, and thus improve the enzyme-like activity. Meanwhile, additional active sites, formed by Fe doping, also endow the catalyst with excellent activity in enzyme-like catalysis. Notably, in the process of sulfidation, the dissolution, redistribution and diffusion result in the disappearance of MoO3@FeOOH cores and the formation of Fe doped MoS2 nanosheets, which significantly facilitate the deposition of Fe-doped MoS2 nanosheets on PPy microtubes. On the basis of the high peroxidase-like catalytic efficiency of the Fe-MoS2@PPy microtubes, a simple and convenient colorimetric strategy for the rapid and sensitive detection of L-cysteine has been developed. This strategy introduces both the PPy layer and Fe doping to increase the conductivity and the density of active sites of MoS2 nanosheets, thus enhancing the catalytic activity and stability. More importantly, Fe-MoS2@PPy microtubes could be used as a good support for loading other materials such as Au and Ag nanoparticles (NPs), forming ternary Fe-MoS2/Ag, Au@PPy nanotubes. This work offers an opportunity to develop low-cost and highly active MoS2-based nanocomposites for promising potential applications in electrochemical energy conversion and medical diagnostics.

Solvothermal synthesis of poly(acrylic acid) decorated magnetic molybdenum disulfide nanosheets for highly-efficient adsorption of cationic dyes from aqueous solutions.

Herein we report solvothermal synthesis of poly(acrylic acid) (PAA) decorated magnetic molybdenum disulfide nanosheets (MMoS2/PAA) for highly efficient adsorption of three cationic dyes of basic fuchsin (BF), methylene blue (MB), and crystal violet (CV) from aqueous solutions. The synthesized MMoS2/PAA was characterized by several techniques including transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), and dynamic light scattering (DLS). Due to the strong electrostatic interaction between cationic dyes and the anionic nanosheet surface, the obtained MMoS2/PAA showed ultrafast adsorption of BF, MB and CV within 2 min with high adsorption capacities of 886.1, 709.0, and 633.6 mg g−1, respectively, much higher than those materials reported recently. PAA molecules bound on the nanosheets played a crucial role in significantly enhancing the dye adsorption. The adsorption kinetics and isotherms of three dyes onto the MMoS2/PAA were well described by the pseudo-second-order kinetic and the Langmuir models. Moreover, the MMoS2/PAA also exhibited high removal efficiencies for various mixed-dye solutions. Besides, such a functional nanomaterial could be effectively recovered from dye solutions under an external magnetic field and reused for dye adsorption without compromising on its performance indicating it can serve as an excellent adsorbent for effective removal of a variety of cationic organic pollutants from industrial effluents.

Hybrid MoS2/g-C3N4-assisted LDI mass spectrometry for rapid detection of small molecules and polyethylene glycols and direct determinationof uric acid in complicated biological samples.

A novel matrix-assisted laser desorption/ionization time-of-flight mass spectrometric method (MALDI-TOF MS) for determination ofhighly sensitive small molecular compounds was developed based on molybdenum disulfide nanosheets hybridized with ultrathin graphitic carbon nitride (MoS2/g-C3N4) as the matrix. With this approach, the synergistic effects of MoS2 and g-C3N4 enhance the UV absorption of MoS2/g-C3N4, increase both desorption and ionization efficiency in LDI MS, and induce higher signal-to-noise ratio of analytes when compared with the bare MoS2 and g-C3N4 matrix in the determinationof amino acids, antibiotics, neutral oligosaccharides, uric acid, and polyethylene glycols (PEGs). The detection limits of these small molecular compounds are in the ranges0.1 to 10μgmL-1, 1*10-3 to 1.0μgmL-1, 1.0 to 10μgmL-1, and 2*10-4μgmL-1, respectively, and the polydispersity index of these PEGs is less than 1.02. Moreover, high salt tolera`nce and homogeneous deposition on the spot results in good reproducibility. The relative standard deviations (RSDs) of shot-to-shot and spot-to-spot (n = 15) of these compounds are less than 10.1% and 12.5%, respectively. With MoS2/g-C3N4, the uric acid in complicated biological samples can be directly determined in combination with LDI-TOF MS. We synthesized MoS2/g-C3N4 nanohybrid as an efficient matrix for MALDI-TOF MS analysis of small molecules as well as quantitative detection of uric acid in human urine.

A Current–Voltage Model for Double Schottky Barrier Devices

AbstractSchottky barriers (SBs) are often formed at the semiconductor/metal contacts and affect the electrical behavior of semiconductor devices. In particular, SBs are playing a major role in the investigation of the electrical properties of mono and 2D nanostructured materials, although their impact on the current–voltage characteristics is frequently neglected or misunderstood. In this work, a single equation is proposed to describe the current–voltage characteristics of two‐terminal semiconductor devices with Schottky contacts. The equation is applied to numerically simulate the electrical behavior for both ideal and nonideal SBs. The proposed model can be used to directly estimate the SB height and the ideality factor. It is applied to perfectly reproduce the experimental current–voltage characteristics of ultrathin molybdenum disulfide or tungsten diselenide nanosheets and tungsten disulfide nanotubes. The model constitutes a useful tool for the analysis and the extraction of relevant transport parameters in any two‐terminal device with Schottky contacts.

Gate‐Controlled Field Emission Current from MoS2 Nanosheets

AbstractMonolayer molybdenum disulfide (MoS2) nanosheets, obtained via chemical vapor deposition onto SiO2/Si substrates, are exploited to fabricate field‐effect transistors with n‐type conduction, high on/off ratio, steep subthreshold slope, and good mobility. The transistor channel conductance increases with the reducing air pressure due to oxygen and water desorption. Local field emission measurements from the edges of the MoS2 nanosheets are performed in high vacuum using a tip‐shaped anode. It is demonstrated that the voltage applied to the Si substrate back‐gate modulates the field emission current. Such a finding, that it is attributed to gate‐bias lowering of the MoS2 electron affinity, enables a new field‐effect transistor based on field emission.