MoS2 Layers Research Articles

Atom-Vacancy-Defect-Derived Electric Hysteresis Loops and Stochastic Low-Frequency Noises in Few-Atom Layer MoS2.

Atom-vacancy-defects present in various materials yield numerous interesting physical phenomena, even obstructing high performance in some cases. On the other hand, their valuable applications to novel devices, such as nitrogen vacancy centers in diamond for quantum bits, have gathered significant attention. In particular, these tendencies become more substantial in two-dimensional (2D) (atomically) thin van der Waals layers. However, correlations with various kinds of atom defects are still under exploration. Herein, we find the stochastic behaviors of large hysteresis loops with strong photoresponse in the static electrical properties in few-atom layer semiconductors, molybdenum disulfide (MoS2). The temperature dependence and transmission electron microscopy reveal that they arise from pairs of two neighboring in-plane S-vacancy defects, which predominantly present only around the interface at the MoS2 flake/substrate, with activation energies ∼0.35 eV. The low-frequency (f) (LF) noise measurements clarify a high f shift in the two 1/f2-dependent regimes, implying stochastic behaviors of electric charges through the S-vacancy pairs with high-speed charge(spin) transitions across low kinetic energy barriers between narrow discrete states. The shallow energy sates are formed from the highly uniform S-vacancy pairs interacting with Mo atoms, which act like quantum dots. The observed stochastic operation holds promise for various application, particularly for probabilistic neuromorphic computation in artificial intelligence.

2D sheets of MoSe2 for waveguide based second harmonic generation

Two-dimensional transition metal dichalcogenides show a strong second-order nonlinear response, which can only be exploited if the interaction between light and 2D material is maximized as it happens in waveguiding structures. Such an approach also allows the addition of a second order nonlinear response to linear integrated optics components by just placing a sheet of transition metal dichalcogenides material on top. Here, we analyze the second harmonic generation in MoSe2 sheets combined with silicon nitride ridge and thin-film waveguides for both modal phase matching and quasi-phase-matching. The calculated second harmonic generation efficiency is comparable with that in lithium niobate waveguides and can further be enhanced by increasing the number of MoSe2 layers on top of the waveguides. This also holds true for flux correlated photons generated by spontaneous parametric down conversion as we show by quantitative analysis.

Synergistic effects of CNT-bridged dual-phase MoS2 on MXene as a ternary hybrid electrode for rapid sensing of chloramphenicol in aqueous media

The fabrication of a hybridized electrochemical sensor denoted CNT/MoS2/MXene for chloramphenicol (CAP) detection is described based on growing MoS2 nanoflakes on stacked Ti3C2Tx MXene and bridging the structure obtained with carbon nanotubes (CNTs). Herein, we introduce an acid-etched stacked Ti3C2Tx MXene as an interlayered structure to accommodate solvothermally grown layered MoS2 and a bridged CNT network for the efficient electrocatalytic sensing of CAP. The successful growth of MoS2 on the MXene surface prevented restacking of layered MXene and increased conductivity. Interconnected CNTs over the MoS2 nanoflake array served as an electron transport highway, accelerating the electron transport pathway and maintaining the structural stability of the MXene/MoS2 heterostructure. Morphologically, CNT/MoS2/MXene was found to have a functionalized multilayered structure and to have a greater electron transfer rate, and a larger electrochemically active surface area than the binary feature. Modifying the surface area of MXene with MoS2 and CNTs synergistically enhanced the transportation of kinetic barrier electrons and well-defined the redox cycle in the ferricyanide system. Further, the electrochemical detection of CAP using a CNT/MoS2/MXene electrode by cyclic voltammetry (CV) produced greater electrochemical responses than bare GCE, MXene, CNT-MoS2, and MoS2-MXene. In addition, scanning rates, the effects of different concentrations, and pH electrolyte tests showed that the GCE-CNT/MoS2/MXene electrode was suitable for the electrochemical sensing of CAP. Amperometric response, as determined by i-t profiles, showed the CNT/MoS2/MXene electrode had superior electrochemical sensing performance for CAP detection, a wide linear range (8 to 152 nM), a remarkably low detection limit (0.32 nM), a high sensitivity of 14.22 μA nM−1cm−2, and superior stability (96 % activity retention after four weeks). The synergistic effect of the ternary three-dimensional assembly with CNT bridging over hierarchical MoS2/MXene increased surface-active sites and electron transportation rates and enhanced CAP detection performance. Moreover, the proposed sensor demonstrated high selectivity and satisfactory recovery for milk, eye drops, and pork.

Optimization of Selenization Condition for Efficiency CIGSe Solar Cells Based on Postselenization of CuInGa Precursors.

The degree of selenization of the CIGSe absorbers is controlled by regulating the parameters of the selenization reaction. The structure, element distribution, phase composition of the CIGSe absorbers, and the performances of the solar cells with different selenization degrees are studied. Insufficient selenization will lead to residual Cu2Se phase on the surface and insufficient Na diffusion, which will affect the VCu+ on the surface and the recombination at the front interface. However, excessive selenization will make the MoSe2 layer thicken at the back interface of the CIGSe/Mo, resulting in the increase of the series resistance and the enhancement of the recombination at the back interface. The appropriate selenization degree is conducive to inhibiting the recombination at the front and back interfaces. Improved device performances can be obtained by optimizing the selenization degree of the absorbers.

Efficient photocatalytic degradation of chloramphenicol from contaminated water over rGO@MoS2 nanocomposites

Antibiotics-based effluents pose a severe threat to the natural ecosystem by acting as reservoirs for the growth of drug-resistant bacteria if untreated. Herein, a facile and scalable approach was developed to engineer photocatalysts associating reduced graphene oxide (rGO) and molybdenum disulfide (rGO@MoS2) that were used for the degradation of chloramphenicol (CAP) from contaminated water under UV-light. The hydrothermally produced rGO@MoS2 catalysts contain CO, COH, and COC functional groups that contribute to the binding of CAP onto their surface. The rGO surface modification with MoS2 layers offers a high surface area for light absorption. Results show that the rGO@MoS2 catalyst (1:1 w/w) exhibits the highest degradation efficiency (DE) of 86 % within 180 min of light exposure at neutral pH. Further, the kinetic modelling studies for CAP degradation by rGO@MoS2 1:1 showed high linearity with pseudo-first order kinetics (R2 ∼ 0.9). The isotherm modelling studies correspond to Langmuir isotherm (R2 ∼ 0.99), suggesting monolayer-type interaction of CAP with the photocatalyst surface during photodegradation. Furthermore, the mechanism of degradation elucidated using scavenging experiments showed the involvement of both holes (h+) and electrons (e−) that contribute to the degradation of CAP by generating reactive oxygen species (ROS) like OH● and O2●− radicals. The applicability of the rGO@MoS2 photocatalyst towards the degradation of CAP was tested in Ganga water, wherein a similar ∼86 % CAP removal was observed. Furthermore, the photocatalyst was found to be stable and could be reused five times. Overall, these findings demonstrate the usefulness of the rGO@MoS2 1:1 composite as an efficient photocatalyst that can be used for the degradation of harmful organic pollutants from water bodies to provide a safer and cleaner environment.

Vertically growth of MoS2 nanosheets on g-C3N4 towards enhanced electrocatalytic performance

MoS2 nanosheets were vertically grown in S-doped graphitic carbon nitride (g-C3N4) nanosheets to enhance electrochemical performance. Dicyandiamide was used as a precursor while sodium molybdate and thioacetamide were as additives, and sulfur was introduced into the carbon lattice of thin-layered g-C3N4 by a two-step thermal polymerization. S-g-C3N4/MoS2 (SCN/MoS2) heterojunctions were then created by a solvothermal synthesis. Subsequently, the electrochemical performance of the heterojunctions was explored. The result suggested that the surface of S-g-C3N4 nanosheets load on uniformly arranged layered MoS2 possession revealed the smallest Tafel slope of 77.2 mV dec−1. After 1000 cycles, no significant change was observed for the linear sweep voltammetry curves. The SCN/MoS2 heterojunction revealed a specific capacity of 588 F g−1 after being assembled into an asymmetric supercapacitor. Superior thin g-C3N4 nanosheets and constituting a composite with strong interfacial electronic coupling with MoS2, doping with heteroatomic elements, and changing the surface structure of g-C3N4 enhanced the charge transfer kinetics and improved the electrochemical performance.

Pulse Duration Dependent Formation of Laser‐Induced Periodic Surface Structures in Atomic Layer Deposited MoS2

AbstractIn this paper, the formation of laser‐induced periodic surface structures (LIPSS) on atomic‐layer deposited MoS2 layers are studied experimentally. The process parameters (laser fluence and the pulse overlap) corresponding to formation of low‐ and high‐spatial frequency LIPSS as well as ablation and modification of the layers are identified for different pulse durations in the range from 0.2 to 10 ps. The role of the temperature accumulation is evaluated by changing the repetition rate from 0.2 to 2 MHz. The negative accumulation effect, i.e., the ablation of the layers becomes more difficult at higher laser pulse overlaps, is also observed. A simple model explaining the transition between different types of the LIPSS and the decrease of the ablation efficiency with the pulse overlap is suggested.

Mechanisms of Defect-Mediated Memristive Behavior in MoS2 Monolayer.

The switching dynamics of a Au∥VS2@MoS2 atomristor is explored by first-principles computations of the atomic-configuration energy and electron transport. It is found that external bias can reduce the energy barrier between the two (high- and low-) conduction states, to achieve nonvolatile resistive switching. We find that the force acting on the switching atom is a combination of electrostatic force (while its charge is induced both electrostatically and chemically) and also by electron-wind, whose effect may hinder the writing process at larger bias. The analysis uncovers how the writing and reading processes of the atomristor depend on several factors: (i) atomic structure details of the Au tip; (ii) the space-gap distance between the tip and MoS2 layer; and (iii) tip metal choice. The fundamental understanding of switching events provides useful guidance for memristor design and possible limitations.

Direct Photo‐Crosslinking Patterning for High‐Performance 0D–2D Hybrid Photodetectors

AbstractHigh‐performance 0D–2D hybrid photodetectors integrated with a crosslinker for direct pattering of quantum dots on the large‐scale synthesized MoS2 layer are reported. In the patterned hybrid structure, QD layers are patterned with a resolution of up to 2 µm, ensuring high precision. Enhanced charge transfer from QDs to 2D materials is confirmed using PL quenching, TR‐PL, and UPS analysis. As a result, the QD/2D hybrid photodetectors with crosslinker‐assisted direct patterning demonstrated a remarkable photoresponsivity of ≈105 A W−1 and a specific detectivity of over 1011 Jones, attributed to the difference in built‐in potential. The crosslinker patterning of QDs opens up potential applications for the photodetectors in highly integrated image sensors and can be further extended to high‐resolution display industries, eliminating unnecessary fabrication processes.

Facile synthesis of Bi2ZnB2O7-MoS2nanocomposite for photodetector and photocatalytic Rhodamine B dye degradation application.

In this research, the visible light active performance of Bi2ZnB2O7(BBZO) was significantly enhanced through the formation of a composite with few layer MoS2. The resultant MoS2@BBZO catalyst was employed in both photocatalysis and photodetector applications. Comprehensive structural and morphological analyses of the MoS2@BBZO catalyst were conducted using x-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy. The estimated band gaps of BBZO and the composite were found to be 2.8 eV and 1.74 eV, respectively. Rhodamine B degradation studies demonstrated that the catalyst achieved 75% degradation within 30 min. Additionally, the photodetector application was investigated, revealing rapid photo-switching capabilities and an increased photocurrent.

Large tunneling photo-thermoelectric voltage using cyclotron resonance in bilayer graphene/MoS2/monolayer graphene van der Waals tunnel junction

A tunnel junction using graphene in quantum Hall states (QHS) recently demonstrated the tunneling photo-thermoelectric effect (TPTE), generating a photovoltage under mid-infrared irradiation. Here, we investigate TPTE in a bilayer graphene (BLG)/6-layer MoS2/monolayer graphene (MLG) tunnel junction. The MoS2 layer facilitated the tuning of the resistance-area product RA of the tunnel junction with the gate voltage, which was challenging with the previously used h-BN barrier. The photovoltage responsivity R v due to TPTE increased with increasing RA, and achieved a maximum responsivity R v of 2.5 × 106 V W−1 at T = 2 K, which was substantially higher than earlier reports. In a device exhibiting high R v and RA, TPTE voltage was generated when the MLG was in the QHS, in contrast to the low R v and RA device, where TPTE voltage appeared at the boundary between the QHS and non-QHS. These findings provide insights into the TPTE effect for exploring the mid-infrared properties of 2D materials.

MoS2@Hydrochar nanocomposites with cost-effective fluid turbulent eddies induced piezoelectric catalytic peroxymonosulfate utilization efficiency for water polluted dye degradation

Piezoelectric materials can induce strain due to the fluid turbulent force produced during fluid shaking, which may be used to activate peroxymonosulfate (PMS). In this study, the effective interfacial interaction of few-odd-numbered layered MoS2 nanosheets and hydrochar (HC) nanocomposites as the piezoelectric material was used in a hydrodynamics energy-driven piezoelectric catalytic PMS activation process (piezo-PMS activation process) for Eriochrome Black T dye degradation. The results showed that Black T dye was efficiently degraded with an efficiency of 99.23 % within 15 min and a pseudo-first-order rate constant of 3.10 min−1 in the MoS2@HC-(6.5:3.5)/PMS/Shaking system. To clearly see the influence of hydraulic gradient (G) value, the hydrodynamics energy-driven piezo-PMS activation process for Black T dye degradation was performed at different shaking frequencies. The results indicated an optimal G value of (14.106 s−1) for Black T dye degradation. Notably, the MoS2@HC-(6.5:3.5)/ PMS/Shaking system produced the lowest EE/O value (34.05 kWhm−3 order−1), resulting in energy savings over 127 times of HC and 9 times of MoS2. Furthermore, piezoelectrochemical measurements of MoS2@HC-(6.5:3.5) indicated that these superior performances primarily resulted from the synergistic effects of MoS2 and HC. This led to a stronger piezoelectric response with effective piezo-generated charge separation, which in turn improved the efficiency of producing reactive species. Combining the scavenger test, FT-IR, and zeta potential analysis, we determined that •OH and SO4•− played a major role, while O2•− and 1O2 played a secondary role in Black T dye degradation. The steady-state concentrations of [•OH]ss, and [SO4•−]ss were 14.52 × 10−14 M and 20.00 × 10−14 M, respectively in the fluid turbulent force driven piezo-PMS activation process. Furthermore, a plausible degradation pathway of Black T dye was proposed based on the assessment of carbon number reduction, the mean oxidation number of organic carbon (MOC) and the predicted TOC/color index.

Introducing 2D layered WS2 and MoS2 as an active catalyst to enhance the hydrogen storage properties of MgH2

The current work describes how 2D layered materials, such as MoS2 and WS2, might improve the de/re-hydrogenation kinetics of MgH2. In the presence of WS2 catalyst, desorption of MgH2 begins at 277 °C, with a hydrogen storage capacity of 5.95 wt%, while the onset desorption temperature of MgH2 catalyzed by MoS2 is 330 °C. In just 1.3 min at 300 °C under 13 atm hydrogen pressure, the MgH2-WS2 absorbed approximately 3.72 wt% of hydrogen, and in 20 min at 300 °C under 1 atm hydrogen pressure, it desorbed around ∼5.57 wt% of hydrogen. To ensure the cyclic stability up to 25 cycles of de/re-hydrogenation of the catalyzed MgH2, a continuously 25 cycles of dehydrogenation (under 1 atm hydrogen pressure at 300 °C) and rehydrogenation (under 13 atm hydrogen pressure at 300 °C) were carried out. As a result, MgH2-WS2 exhibits superior cyclic stability than MgH2–MoS2. In addition, with the de/re-hydrogenation kinetics, MgH2-WS2 has a lower reaction activation energy (∼117 kJ/mol) than to other catalyzed and pristine samples. Conversely, the thermodynamical parameters, specifically the change in enthalpy of MgH2, are unaffected by addition of these layered WS2 and MoS2 catalysts.

Significant Enhancement in THz Emission and Piezoelectricity in Atomically Thin Nb-Doped MoS2.

A significantly enhanced THz radiation generation from femtosecond photoexcited MoS2 layers due to Nb-doping is reported here. Different microscopic mechanisms involved in the THz photocurrent generation vary in their relative contributions in the two cases of photoexcitation, i.e., above and below the electronic bandgap of the layers. For a moderate Nb-doping level of just ∼0.05%, we have observed a multifold enhancement in the THz emission for the case of the above bandgap excitation, which is, though, nearly 1.5 times for the case of the below bandgap excitation of the monolayer MoS2. Alongside the difference in THz generation efficiency, the THz pulse polarity is also reversed at the above bandgap excitation of the Nb-doped layers, consequent to the reversed surface depletion field. Except for a slightly smaller difference in the THz enhancement factor, all the observations are reproducible in the bilayers as well to imply a weaker inversion symmetry and reduced screening of the surface depletion field due to Nb-doping. Furthermore, we employed pristine MoS2 and Nb-doped MoS2 monolayers to fabricate piezoelectric nanogenerator devices. Like enhancement in the ultrafast THz emission, the piezoelectric performance of the nanogenerator, fabricated with the Nb-doped MoS2 monolayer is also increased by a similar factor.

Tuning the Schottky barrier height in single- and bi-layer graphene-inserted MoS2/metal contacts

First-principle calculations based on density functional theory are employed to investigate the impact of graphene insertion on the electronic properties and Schottky barrier of MoS2/metals (Mg, Al, In, Cu, Ag, Au, Pd, Ti, and Sc) without deteriorating the intrinsic properties of the MoS2 layer. The results reveal that the charge transfer mainly occurs at the interface between the graphene and metal layers, with smaller transfer at the interface between bi-layer garphene or between graphene and MoS2. And the tunneling barrier exists at the interface between graphene and MoS2, which hinders electron injection from graphene to MoS2. Importantly, the Schottky barrier height (ΦSB,N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Phi_{{\ ext{SB,N}}}$$\\end{document}) decreases upon graphene insertion into MoS2/metal contacts. Specifically, for single-layer graphene, the ΦSB,N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Phi_{{\ ext{SB,N}}}$$\\end{document} of MoS2 contacted with Mg, In, Sc, and Ti are − 0.116 eV, − 0.116 eV, − 0.014 eV, and − 0.116 eV, respectively. Furthermore, with bilayer graphene, when by inserting bi-layer graphene, the negative n-type Schottky barrier of − 0.086 eV, − 0.114 eV, − 0.059 eV, − 0.008 eV, and − 0.0636 eV are observed for MoS2 contacted with the respective metals, respectively. These findings provide a practical guidance for developing and designing high-performance transition metal dichalcogenide nanoelectronic devices.

In Situ Studies on the Influence of Surface Symmetry on the Growth of MoSe2 Monolayer on Sapphire Using Reflectance Anisotropy Spectroscopy and Differential Reflectance Spectroscopy

The surface symmetry of the substrate plays an important role in the epitaxial high-quality growth of 2D materials; however, in-depth and in situ studies on these materials during growth are still limited due to the lack of effective in situ monitoring approaches. In this work, taking the growth of MoSe2 as an example, the distinct growth processes on Al2O3 (112¯0) and Al2O3 (0001) are revealed by parallel monitoring using in situ reflectance anisotropy spectroscopy (RAS) and differential reflectance spectroscopy (DRS), respectively, highlighting the dominant role of the surface symmetry. In our previous study, we found that the RAS signal of MoSe2 grown on Al2O3 (112¯0) initially increased and decreased ultimately to the magnitude of bare Al2O3 (112¯0) when the first layer of MoSe2 was fully merged, which is herein verified by the complementary DRS measurement that is directly related to the film coverage. Consequently, the changing rate of reflectance anisotropy (RA) intensity at 2.5 eV is well matched with the dynamic changes in differential reflectance (DR) intensity. Moreover, the surface-dominated uniform orientation of MoSe2 islands at various stages determined by RAS was further investigated by low-energy electron diffraction (LEED) and atomic force microscopy (AFM). By contrast, the RAS signal of MoSe2 grown on Al2O3 (0001) remains at zero during the whole growth, implying that the discontinuous MoSe2 islands have no preferential orientations. This work demonstrates that the combination of in situ RAS and DRS can provide valuable insights into the growth of unidirectional aligned islands and help optimize the fabrication process for single-crystal transition metal dichalcogenide (TMDC) monolayers.

Antifriction characteristics of the magnetron sputtered MoS2 coating of ITER blanket module bolted joints in high vacuum at elevated temperature [formula omitted] =250 °C

The high values of bolt preload force Fa = 90–1200 kN created by the ITER remote handling system can be achieved by using dry coating lubricants such as magnetron sputtering film MoS2 or WS2. An expression was determined to estimate the contact pressure based on the number thread turns and the width of the thread contact area in fastened assemblies that used the Spiralock technology. This study investigated the tribological aspects of the magnetron sputtering MoS2 coating at different thicknesses hc = 6.4–21 μm, contact pressures pa = 20–1200 MPa against the spherical pin (austenitic stainless steel 316L(N)-IG) at elevated temperatures of T = 250 °C in vacuum pv = 10−2–10−3 Pa. Friction data for “humid” and “dry” rectangular specimens with MoS2 coating were obtained and compared. With an increase in the thickness of the coating from 6.4 μm to 21 μm, we obtained a distinct stabilization the friction coefficient of the low friction coating for each given regime of wear that diminished from 0.09 ± 0.010 to 0.05 ± 0.005. The wear mechanism of the “layered MoS2 coating/metal substrate” tribosystem resulted in significant plastic deformation along the sliding direction of the MoS2 solid lubricant as well as microgrooving and microploughing of the coating by the asperities of the flat contact spot of the spherical pin. Regardless of the type of bolted pair alloys used, we concluded that it is necessary to deposit a low friction coating on both the internal and external threads of the ITER blanket module bolted joints that use the Spiralock technology.

Characterization of MoS2:Nb sputtered thin films. An application as hole transport layer in Cu2ZnSnS4/Si tandem solar cells

MoS2:Nb films deposited by radio-frequency magnetron sputtering are investigated in view of their application in infrared (IR)-transparent contacts for tandem photovoltaic devices.This material is already known to give a good electrical contact with p-type chalcogenide semiconductors, which are typically grown onto opaque molybdenum metallic contacts and a MoS2 layer spontaneously forms at the back interface during the on-top semiconductor growth. Our study explores a different approach, which involves the direct growth of IR-transparent MoS2:Nb films via sputtering inside complete photovoltaic devices, like Cu2ZnSnS4 (CZTS)-based single junction solar cells and CZTS/Si tandem devices. Films deposited at different sputtering pressures are compared by analysing their microstructure, morphology, chemical composition, optical and electrical properties. The effects of post-deposition sulfurization treatments are also investigated. We find that MoS2:Nb films deposited at around 0.1 Pa exhibit compactness but show a notable sulfur deficit ([S]/[Mo]≈1.4), a significant sub-bandgap optical absorptance and lack of crystallinity. Increasing the Ar pressure to 1 Pa raises the [S]/[Mo] ratio to 2.2, yielding crystalline films with good IR-transparency, although with a porous morphology. Despite 0.5 wt% Nb-doping of the sputtering target, the as-deposited films demonstrate n-type conductivity likely due to uncontrolled impurities and intrinsic defects. Ultraviolet Photoemission Spectroscopy measurements suggest that films’ work function higher than 5 eV can be obtained with a post-deposition sulfurization, making these materials suitable as Hole Transport Layer in photovoltaic applications. A similar increase in work function is expected in the CZTS/MoS2 junctions, since the sputtered MoS2:Nb films undergo a sulfurization process needed to obtain the overlying polycrystalline CZTS absorber.CZTS solar cells produced with sputtered MoS2 and Transparent Conductive Oxides contacts on glass substrates, despite plagued by severe adhesion problems, show the potentiality to give efficiencies comparable to reference devices with standard Mo back contact. Fabrication of CZTS/Si tandem devices on textured silicon bottom cells yields a maximum efficiency of 4.4 %, primarily hindered by the low quality of the CZTS film on textured substrates. Nonetheless, optoelectronic characterizations based on both spectrophotometric and quantum efficiency measurements confirm a good IR transparency of the MoS2-based intermediate contacts and the desired electrical behaviour.

Investigation into the role of MoS2 in the composite of Cu-Cu2O/MoS2 in catalytic aerobic oxidation of benzylic alcohols

Cuprous oxide (Cu2O), as a common transition metal semiconductor material, has found extensive applications and research in the field of catalysis due to its unique physicochemical properties. To improve its catalytic performance, introducing carriers to form composite materials with Cu2O has proven to be a promising strategy for enhancing its stability, activity, and selectivity. In this study, we introduced MoS2 to form a composite material with Cu-Cu2O, investigating the impact of MoS2 on the activity of Cu-Cu2O in selective alcohol oxidation. The results demonstrate a significant improvement in the catalytic activity of Cu-Cu2O upon the introduction of MoS2. Further investigations substantiate the close correlation between the enhanced activity of Cu-Cu2O and the interaction with thin layered MoS2 flakes. The quantity of the thin layered MoS2 is small but its impact on the catalytic activity is significant. It induces changes in the band and electronic structures of Cu-Cu2O, and the changes facilitate the activation of O2 and electron transfer in the oxidation, and thus promote the catalysis.

Understanding the Influence of Carbon Interlayers on Material Removal and Tribochemical Evolution in Multilayer Coatings Through In-Situ Analysis

The carbon interlayers in the multilayer coatings can improve the load-bearing capacity and oxidation resistance, promote the layer-by-layer wear mechanism, and extend the lifespan of the multilayer coating, which is crucial to improving their tribological properties. To investigate the role of C interlayers in the competitive relationship between tribochemistry and material removal in multilayer coatings, this study comprehensively examines the tribological behavior of single layer MoS2 and multilayer MoS2/C coatings through in-situ tribotests and nanoscratch tests. Key findings reveal that the C interlayers enhance the tribological behavior by reducing the oxidation rate of MoS2, improving the load distribution, and delaying the onset of coating failure. Specifically, the single layer MoS2 coating demonstrated a lifespan of 55,000 cycles, whereas the multilayer MoS2/C coating achieved 80,000 cycles, reflecting a 45% enhancement. The critical load increased from 8 mN to 18 mN, indicating a 125% improvement in removal resistance. The presence of C layers results in a more stable and enduring tribofilm, which leads to reduced friction and wear. This study underscores the importance of in-situ analysis by combining nanoscratch with Raman mapping to elucidate the complex tribological behavior of coatings. These insights are crucial for designing efficient, wear-resistant, low-friction multilayer coatings for diverse industrial applications.