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Top-down liquid-phase exfoliation (LPE) and bottom-up hot-injection synthesis are scalable methods to produce Generally thought off as two entirely different fields, we show that similar stabilization mechanisms apply to colloids of molybdenum disulfide (MoS2) produced by both methods. By screening the colloidal stability of MoS2 produced in a hot-injection synthesis in a wide range of solvents, we observe that colloidal stability can be understood based on solution thermodynamics, wherein matching the solubility parameter of solvent and nanomaterial maximizes colloidal stability. Identical to MoS2 produced through LPE, optimal solvents to disperse MoS2 produced from the bottom-up have similar solubility parameters of approximate to 22 MPa1/2 and include aromatic solvents with polar functionalities, such as o-dichlorobenzene, and polar aprotic solvents, such as N,N-dimethylformamide. We further complemented our findings by nuclear magnetic resonance (NMR) spectrscopy, highlighting that organic surfactants, such as oleylamine and oleic acid, have a minimal affinity toward the nanocrystal surface and engage in a highly dynamic adsorption/desorption equilibrium. We thus conclude that hot injection yields MoS2 colloids with comparable surfaces as those produced by LPE. These similarities might offer the prospect of using established procedures developed for LPE nanomaterials to postprocess colloidally synthesized dispersions of 2D colloids as processable inks.

International audience; Hybrid van der Waals heterostructures made of 2D materials and organic molecules exploit the high sensitivity of 2D materials to all interfacial modifications and the inherent versatility of the organic compounds. In this study, we are interested in the quinoidal zwitterion/MoS 2 hybrid system in which organic crystals are grown by epitaxy on the MoS 2 surface and reorganize in another polymorph after thermal annealing. By means of field-effect transistor measurements recorded in situ all along the process, atomic force microscopy and density functional theory calculations we demonstrate that the charge transfer between quinoidal zwitterions and MoS 2 strongly depends on the conformation of the molecular film. Remarkably, both the field effect mobility and the current modulation depth of the transistors remain unchanged which opens up promising prospects for efficient devices based on this hybrid system. We also show that MoS 2 transistors enable fast and accurate detection of structural modifications that occur during phases transitions of the organic layer. This work highlights that MoS 2 transistors are remarkable tools for on-chip detection of molecular events occurring at the nanoscale, which paves the way for the investigation of other dynamical systems.

Large-area nanopore drilling is a major bottleneck in state-of-the-art nanoporous 2D membrane fabrication protocols. In addition, high-quality structural and statistical descriptions of as-fabricated porous membranes are key to predicting the corresponding membrane-wide permeation properties. In this work, we investigate Xe-ion focused ion beam as a tool for scalable, large-area nanopore fabrication on atomically thin, free-standing molybdenum disulfide. The presented irradiation protocol enables designing ultrathin membranes with tunable porosity and pore dimensions, along with spatial uniformity across large-area substrates. Fabricated nanoporous membranes are then characterized using scanning transmission electron microscopy imaging, and the observed nanopore geometries are analyzed through a pore-edge detection and analysis script. We further demonstrate that the obtained structural and statistical data can be readily passed on to computational and analytical tools to predict the permeation properties at both individual pore and membrane-wide scales. As an example, membranes featuring angstrom-scale pores are investigated in terms of their emerging water and ion flow properties through extensive all-atom molecular dynamics simulations. We believe that the combination of experimental and analytical approaches presented here will yield accurate physics-based property estimates and thus potentially enable a true function-by-design approach to fabrication for applications such as osmotic power generation and desalination/filtration.

The science and engineering of two-dimensional materials (2DMs), in particular, of 2D semiconductors, is advancing at a thriving pace. It is well known that these delicate few-atoms thick materials can be damaged during the processing toward their integration into final devices. Thermal scanning probe lithography (t-SPL) is a gentle alternative to the typically used electron beam lithography to fabricate these devices avoiding the use of electrons, which are well known to deteriorate the 2DMs' properties. Here, t-SPL is used for the fabrication of MoS2-based field effect transistors (FETs). In particular, the use of t-SPL is demonstrated for the first time for the fabrication of edge-contact MoS2 FETs, combining the hot-tip patterning and Ar+ milling to etch the 2DM. To avoid contamination of the contact interface by atmospheric gas molecules, etching and metal deposition are performed without breaking the vacuum conditions in between. With this process, edge-contact MoS2 FETs are successfully fabricated and characterized. On/off ratios up to 108 and 109 are obtained at room temperature in air and vacuum, respectively, i.e., comparable with the best values reported in the literature., The authors thank the Center of Micro/Nanotechnology (CMi) of EPFL. We also thank Sadegh Kamaei, Teodor Rosca, and Prof. A. M. Ionescu for their help with the electrical measurement set-up and access to their instruments. This work received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Program (Project “MEMS 4.0”, ERC-2016-ADG, grant agreement no. 742685)., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

We report on transport measurements in monolayer MoS2 devices, close to the bottom of the conduction band edge. These devices were annealed in situ before electrical measurements. This allows us to obtain good ohmic contacts at low temperatures, and to measure precisely the conductivity and mobility via four-probe measurements. The measured effective mobility up to μeff = 180 cm2/Vs is among the largest obtained in CVD-grown MoS2 monolayer devices. These measurements show that electronic transport is of the insulating type for σ≤ 1.4e2/h and n ≤ 1.7×1012 cm-2, and a crossover to a metallic regime is observed above those values. In the insulating regime, thermally activated transport dominates at high temperature (T > 100 K). At lower temperatures, conductivity is driven by Efros-Schklovkii variable range hopping in all measured devices, with a universal and constant hopping prefactor, that is a clear indication that hopping is not phonon-mediated. At higher carrier density, and high temperature, the conductivity is well modeled by the Boltzmann equation for a non-interacting Fermi gas, taking into account both phonon and impurity scatterings. Finally, even if this apparent metal-insulator transition can be explained by phonon-related phenomena at high temperature, the possibility of a genuine 2D MIT cannot be ruled out, as we can observe a clear power-law diverging localization length close to the transition, and a one-parameter scaling can be realized.

Charge transport plays a crucial role in manifold potential applications of two-dimensional materials, including field effect transistors, solar cells, and transparent conductors. At most operating temperatures, charge transport is hindered by scattering of carriers by lattice vibrations. Assessing the intrinsic phonon-limited carrier mobility is thus of paramount importance to identify promising candidates for next-generation devices. Here we provide a framework to efficiently compute the drift and Hall carrier mobility of two-dimensional materials through the Boltzmann transport equation by relying on a Fourier-Wannier interpolation. Building on a recent formulation of long-range contributions to dynamical matrices and phonon dispersions [Phys. Rev. X 11, 041027 (2021)], we extend the approach to electron-phonon coupling including the effect of dynamical dipoles and quadrupoles. We identify an unprecedented contribution associated with the Berry connection that is crucial to preserve the Wannier-gauge covariance of the theory. This contribution is not specific to 2D crystals, but also concerns the 3D case, as we demonstrate via an application to bulk SrO. We showcase our method on a wide selection of relevant monolayers ranging from SnS2 to MoS2, graphene, BN, InSe, and phosphorene. We also discover a non-trivial temperature evolution of the Hall hole mobility in InSe whereby the mobility increases with temperature above 150 K due to the mexican-hat electronic structure of the InSe valence bands. Overall, we find that dynamical quadrupoles are essential and can impact the carrier mobility in excess of 75%., 31 pages and 16 figures

International audience; The development of non-enzymatic sensors is a challenge which requires, on the one hand, careful design of the sensing materials with respect to the chosen analyte, and on the other hand, suitable device architectures. In this work, we propose single-layer molybdenum disulfide (MoS 2) decorated with sub-nanometer Pt clusters as the sensing platform for the detection of cortisol. The aim is to assess the suitability of such a sensing platform for the development of wearable and portable cortisol sensors. For this study, we performed multi-scale computer simulations at the materials level up to device scale. First, ab initio simulations within the framework of density functional theory (DFT) allowed us to gain insights into the interaction, at the atomic level, between the analyte (cortisol) and the sensing platform (MoS 2 /Pt). Then, by carrying out technology computer-aided design (TCAD) simulations, we were able to consider a device architecture and investigate its performance as cortisol sensor. Following our multi-scale simulation strategy, we were able to assess the proposed field-effect transistor (FET) sensor, whose channel is made of Pt-decorated MoS 2. The sensing mechanism relies on the chemiresistive response of the device to the adsorption of cortisol on the channel, which leads to a charge transfer from the analyte to the substrate and, consequently, to the measurable shift in the gate voltage threshold of the FET. Our findings suggest that both the choice of the sensing materials and the proposed FET architecture are suitable for detecting cortisol by non-enzymatic means, as we predict a maximum theoretical gate voltage shift of 780 mV in ideal conditions. We may expect our results to provide the necessary basis to develop highly sensitive non-enzymatic cortisol sensors based on 2D materials decorated with Pt nanoclusters.

Synthesis and characterization of MoS2 nanoflower by using conventional hydrothermal route. The reaction is carried out at 160oC for 12 hours by taking 1:2 proportion of citric acid and ammonium molybdate by adding 2.36 gm of thioacetamide. The obtained powder is characterized by using X-ray Diffractogram and Scanning Electron Microscopy. X-ray Diffractogram reveals that MoS2 shows hexagonal crystal structure. Field Emission Scanning Electron Microscopy shows nanoflower type structure. Chemical analysis using Energy Dispersive Spectra (EDS) indicates the presence of Mo & S.

Transition metal dichalcogenides layered nano-crystals are emerging as promising candidates for next-generation optoelectronic and quantum devices. In such systems, the interaction between excitonic states and atomic vibrations is crucial for many fundamental properties, such as carrier mobilities, quantum coherence loss, and heat dissipation. In particular, to fully exploit their valley-selective excitations, one has to understand the many-body exciton physics of zone-edge states. So far, theoretical and experimental studies have mainly focused on the exciton–phonon dynamics in high-energy direct excitons involving zone-center phonons. Here, ultrafast electron diffraction and ab initio calculations are used to investigate the many-body structural dynamics following nearly- resonant excitation of low-energy indirect excitons in MoS2. By exploiting the large momentum carried by scattered electrons, the excitation of in-plane K- and Q- phonon modes are identified with E′ symmetry as key for the stabilization of indirect excitons generated via near-infrared light at 1.55 eV, and light is shed on the role of phonon anharmonicity and the ensuing structural evolution of the MoS2 crystal lattice. The results highlight the strong selectivity of phononic excitations directly associated with the specific indirect- exciton nature of the wavelength-dependent electronic transitions triggered in the system.

Owing to the tremendous energy storage capacity of two-dimensional transition metal carbides (MXenes), they have been efficiently utilized as a promising candidate in the field of super-capacitors. The energy storage capacity of MXenes can be further enhanced using metal dopants. Herein, we have reported the synthesis of pristine and nickel doped niobium-carbide (Nb2C) MXenes, their computational and electrochemical properties. Upon introduction of nickel (Ni) the TDOS increases and a continuous DOS pattern is observed which indicates coupling between Ni and pristine MXene. The alterations in the DOS, predominantly in the nearby region of the Fermi level are profitable for our electrochemical applications. Additionally, the Ni-doped sample shows a significant capacitive performance of 666.67 F g-1 which can be attributed to the additional active sites generated by doping with Ni. It is worth noting that doped MXenes exhibited a capacitance retention of 81% up to 10 000 cycles. The current study unveils the opportunities of using MXenes with different metal dopants and hypothesize on their performance for energy storage devices Owing to the tremendous energy storage capacity of two-dimensional transition metal carbides (MXenes), they have been efficiently utilized as a promising candidate in the field of super-capacitors. The energy storage capacity of MXenes can be further enhanced using metal dopants. Herein, we have reported the synthesis of pristine and nickel doped niobium-carbide (Nb2C) MXenes, their computational and electrochemical properties. Upon introduction of nickel (Ni) the TDOS increases and a continuous DOS pattern is observed which indicates coupling between Ni and pristine MXene. The alterations in the DOS, predominantly in the nearby region of the Fermi level are profitable for our electrochemical applications. Additionally, the Ni-doped sample shows a significant capacitive performance of 666.67 F g-1 which can be attributed to the additional active sites generated by doping with Ni. It is worth noting that doped MXenes exhibited a capacitance retention of 81% up to 10 000 cycles. The current study unveils the opportunities of using MXenes with different metal dopants and hypothesize on their performance for energy storage devices

A novel hybrid material consisted of carbon covered Fe3O4 nanoparticles and MoS2 nanoflower (FCM) was designed and prepared by micelle-assisted hydrothermal methods. Multiple techniques, including X-Ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize it. The results show that FCM has a flower-like morphology with a 330 nm Fe3O4 core as well as 70 nm highly crystalline MoS2 shell. FCM is superparamagnetic with a saturation magnetization of 35 emu g−1. Then hydrocracking of Canadian bitumen residue (CBR) was applied to estimate its catalytic activity. The results show that FCM exhibits superior catalytic hydrocracking activity compared to bulk MoS2 and commercial oil-dispersed Mo(CO)6 by the same Mo loading. Further measurement by elemental analysis, XPS and XRD reveals that the MoS2 nanoflower with abundant catalytic active sites and covered carbon layer with anti-coke ability donate to the superior upgrading performance. Besides, the catalysts can be easily recovered by the external magnetic field. This work provides a novel kind magnetic nanocatalyst which is potential for slurry-phase hydrocracking applications.

Friction and high temperatures greatly affect machining efficiency when machining superalloy materials. Nanoparticles with high thermal conductivity and lubricity are preferred for increase lubricant performance. Nanofluids prepared with nanoparticles not only reduce environmental concerns but also positively affect the machining efficiency in the sustainable manufacturing process. However, some nanoparticles added in mono form stand out with their thermal conductivity and some nanoparticles with their lubricating performance. For this reason, the lubrication performance of hybrid nanofluids prepared with nanoparticles with different superior properties is a matter of interest. In this study, the machining performance of Inconel X-750 superalloy was investigated by using hexagonal boron nitride (hBN), graphite (Grpt), and MoS2 nanoparticles with different shapes and properties. For this purpose, the milling experiments were performed under three different hybrid nanofluid (hBN/Grpt, hBN/MoS2, and Grpt/MoS2) conditions, at three different cutting speeds (30, 45, and 60 m/min), and three different feed rates (0.05, 0.10, and 0.15 mm/rev). Cutting force, cutting temperature, surface roughness/topography, tool wear, and tool life were selected as machining performance criteria. According to the results obtained from the experiments, it was understood that the hBN/Grpt hybrid nanofluid outperformed hBN/MoS2 and Grpt/MoS2 conditions in all performance criteria. hBN/Grpt hybrid nanofluid achieved 36.17% and 6.08% improvement in tool life compared to Grpt/MoS2 and hBN/MoS2 nanofluids, respectively. Duzce University (Turkey) Research FundDuzce University [2017.07.04.593] The authors wish to thank the Duzce University (Turkey) Research Fund for their financial support of this experimental study (Project Number: 2017.07.04.593). WOS:000696326900006 2-s2.0-85114105505

The nitrogen reduction reaction (NRR) has become an ideal alternative to the Haber‐Bosch process, as NRR possesses, among others, the advantage of operating under ambient conditions and saving energy consumption. The key to efficient NRR is to find a suitable electrocatalyst, which helps to break the strong N≡N bond and improves the reaction selectivity. Molybdenum disulfide (MoS2) as an emerging layered two‐dimensional material has attracted a mass of attention in various fields. In this minireview, we summarize the optimization strategies of MoS2‐based catalysts which have been developed to improve the weak NRR activity of primitive MoS2. Some theoretical predictions have also been summarized, which can provide direction for optimizing NRR activity of future MoS2‐based materials. Finally, an outlook about the optimization of MoS2‐based catalysts used in electrochemical N2 fixation are given.

MATLAB and Verolig-A codes

A sustainable future demands a successful transition from a carbon-energy dependent economy towards renewable energy schemes, many of which ultimately rely on the development of efficient electrocatalysis that either converts chemical energy into electricity or uses electrons to produce chemical energy. In general, electrocatalysis studies focus on the interactions (e.g., electron transfer) between the catalyst surface and the reaction intermediates. However, the role of electron spin, as an intrinsic property of electrons, has commonly been overlooked. Recently, controlling the electron spin polarization at the catalyst’s surface demonstrated the great potential of boosting both reaction activity and product selectivity. Molecule-induced electron spin polarization inspired by the chiral-induced spin selectivity (CISS) effect has started to have a remarkable impact in electrocatalysis. In this compact review, we summarize the latest studies that use molecule-induced electron spin polarization to enhance catalytic performance. We focus on the reactions essential to the so-called hydrogen economy, and discuss the feasibility and limitations of this effect. Finally, we share our perspective regarding the more impactful future applications.

İki boyutlu (2B) malzemeler, bu malzemelerin ürettiği cihazların yüksek performans göstermesi nedeniyle birçok araştırmacının ilgisini çekmiştir. 2B malzeme elde etmek için solüsyon tabanlı kimyasal sentez, kimyasal buhar biriktirme (KBB), moleküler ışın epitaksisi, atomik katman biriktirme, darbeli lazer biriktirme (DLB) gibi işlemler sırasında saatler gerektiren farklı üretim yöntemleri bulunmaktadır. 2B yapılar elde edildikten sonra, kusurları da dahil olmak üzere özellikleri farklı karakterizasyon araçları ile ortaya çıkarılmalıdır. Karakterizasyon süreci de üretim süreci gibi zaman ve uzmanlık gerektirir. Bu açıdan, üretilen örneklerin pratik ve hızlı sınıflandırılması için Evrişimli Sinir Ağları (ESA) gibi derin öğrenme yöntemleri bir çözüm olabilir. Ancak, yukarıda bahsedilen uzun deneysel süreçler nedeniyle araştırma laboratuvarlarının çoğunda yeterli sayıda örnek bulunmamaktadır. Bu çalışmada, farklı elektronik uygulamalarda yüksek potansiyele sahip, yaygın olarak çalışılan bir 2B yarı iletken olan MoS2'nin yapay olarak oluşturulmuş görüntülerini kullanan bir CNN algoritmasının performansı sunulmaktadır. Normal ve kusurlu MoS2 pullarını içeren sentetik optik mikroskobik görüntüler, Fresnel Denklemleri kullanılarak farklı malzemeler üzerine gelen ışığın yoğunlukları ile oluşturulur. Normal ve kusurlu örnekleri tespit etmek için derin bir CNN algoritması oluşturulmuştur. Doğruluk ölçümlerinin sonuçları, CNN'nin gelecekte yeterli sayıda gerçek görüntü ile iki boyutlu malzemelerin karakterizasyonu için kullanılabileceğini göstermiştir.

International audience; Two-dimensional (2D) van der Waals (vdW) heterostructures currently have attracted much attention in widespread research fields where semiconductor materials are key. With the aim of gaining insights into photocatalytic materials, we use density functional theory (DFT) calculations within the HSE06 functional to analyze the evolution of optoelectronic properties and high-frequency dielectric constant profiles of various 2D MoO3–xSx/MoS2 heterostructures modified by chemical and physical approaches. Although the MoO3/MoS2 heterostructure is a type III heterojunction associated with a metallic character, we found that exchanging the terminal oxo atoms of the MoO3–xSx single layer (SL) with sulfur enables shifting its CB position above the VB position of the MoS2 SL. This trend gives rise to a type II heterojunction where the band gap and charge transfer within the two layers are driven continuously by the S concentration in the MoO3–xSx SL. This fine-tuning leads to a versatile type II heterostructure proposed to provide a direct Z-scheme system valuable for photocatalytic water splitting.

Indirect absorption extended below the direct transition edge and increase in carrier lifetime derived from Rashba spin–orbit coupling may advance theoptoelectronicapplications of metalhalideperovskites. Spin-orbit coupling in halide perovskites is due to the presence of heavy elements in their structure. However, when these materials lack an inversion symmetry, for example by the application of strain, spin–orbit coupling becomes odd in the electron’s momentum giving rise to a splitting in the electronic energy bands. Here we report on the observation of a large Rashba splitting of 117 meV at room temperature, as predicted by relativistic first-principles calculations, in halide perovskitesingle crystalsthrough a facile compositional engineering approach. Partial substitution oforganic cationsbyrubidiumin single crystals induces significant indirect absorption and dual peakphotoluminescenceas a result of a large Rashba splitting. We measured circularly polarized photoluminescence and magneto-photoluminescence in perovskite films printed by single crystals as well as magneto-electroluminescence and magneto-photocurrent in spin-LEDs based on perovskite single crystals. They indicated significant spin-momentum locking due to the large Rashba effect. A hybrid perovskite single crystalphotodetectorachieved record figures of merit, including detectivity of more than 1.3 × 1018Jones which represents a three orders of magnitude improvement compared to the to date record. These findings show that facile compositional engineering of perovskite single crystals holds great promise for further advancing the optoelectronic properties of existing materials.

Covalent functionalization of two‐dimensional molybdenum disulfide (2D MoS2) holds great promise in developing robust organic‐MoS2 hybrid structures. Herein, for the first time, we demonstrate an approach to building up a bisfunctionalized MoS2 hybrid structure through successively reacting activated MoS2 with alkyl iodide and aryl diazonium salts. This approach can be utilized to modify both colloidal and substrate supported MoS2 nanosheets. We have discovered that compared to the adducts formed through the reactions of MoS2 with diazonium salts, those formed through the reactions of MoS2 with alkyl iodides display higher reactivity towards further reactions with electrophiles. We are convinced that our systematic study on the formation and reactivity of covalently functionalized MoS2 hybrids will provide some practical guidance on multi‐angle tailoring of the properties of 2D MoS2 for various potential applications., For the first time, we demonstrate an approach to building up a bisfunctionalized MoS2 hybrid structure through successively treating activated MoS2 with alkyl iodide and aryl diazonium salt. This approach can be used to modify both colloidal and substrate‐supported MoS2 nanosheets.

Two-dimensional materials, such as transition-metal dichalcogenides (TMDs), are attractive candidates for sensing applications due to their high surface-to-volume ratio, chemically active edges, and good electrical properties. However, their electrical response to humidity is still under debate and experimental reports remain inconclusive. For instance, in different studies, the impedance of MoS2-based sensors has been found to either decrease or increase with increasing humidity, compromising the use of MoS2 for humidity sensing. In this work, we focus on understanding the interaction between water and TMDs. We fabricated and studied humidity sensors based on MoS2 and WS2 coated with copper chloride and silver nitrate. The devices exhibited high chemical stability and excellent humidity sensing performance in relative humidity between 4 and 80%, with response and recovery times of 2 and 40 s, respectively. We have systematically investigated the humidity response of the materials as a function of the type and amount of induced metal salt and observed the reverse action of sensing mechanisms. This phenomenon is explained based on a detailed structural analysis of the samples considering the Grotthuss mechanism in the presence of charge trapping, which was represented by an appropriate lumped-element model. Our findings open up a possibility to tune the electrical response in a facile manner and without compromising the high performance of the sensor. They offer an insight into the time-dependent performance and aging of the TMD-based sensing devices., The Catalan Institute of Nanoscience and Nanotechnology (ICN2) is funded by the CERCA program/Generalitat de Catalunya and is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706). We acknowledge support from the EU Project Nanosmart (H2020 ICT-07-2018) and ICN2 members acknowledge the Spanish MINECO project SIP (PGC2018-101743-B-I00). P.X. acknowledges support by a PhD fellowship from the EU Marie Skłodowska-Curie COFUND PREBIST project (Grant Agreement No. 754558).

The present study was done to investigate and compare the photocatalytic and antibacterial activity of two in situ Manganese doped ternary nanocomposites. The dual ternary hybrid systems comprised Mn-doped Ag2WO4 coupled with MoS2-GO and Mn-doped MoS2 coupled with Ag2WO4-GO. Both hierarchical alternate Mn-doped ternary heterojunctions formed efficient plasmonic catalysts for wastewater treatment. The novel nanocomposites were well-characterized using XRD, FTIR, SEM-EDS, HR-TEM, XPS, UV-VIS DRS, and PL techniques confirming the successful insertion of Mn+2 ions in respective host substrates. The bandgap of the ternary nanocomposites evaluated by the tauc plot showed them visible light-active nanocomposites. The photocatalytic ability of both Mn-doped coupled nanocomposites was investigated against the dye methylene blue. Both ternary nanocomposites showed excellent sunlight harvesting ability for dye degradation in 60 min. The maximum catalytic efficiency of both photocatalysts was obtained at a solution pH value of 8, photocatalyst dose and oxidant dose of 30 mg/100 mL and 1 mM for Mn-Ag2WO4/MoS2-GO, 50 mg/100 mL, 3 mM for Mn-MoS2/Ag2WO4-GO keeping IDC of 10 ppm for all photocatalysts. The nanocomposites showed excellent photocatalytic stability after five successive cycles. The response surface methodology was used as a statistical tool for the evaluation of the photocatalytic response of several interacting parameters for dye degradation by ternary composites. The antibacterial activity was determined by the inactivation of gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria by support-based doped ternary hybrids. 2023 Elsevier Ltd This research was funded by the Higher Education Commission (HEC), Pakistan, under Indigenous 5000 Ph.D. Fellowship with student PIN "pin # 518-121977-2PS5-032 (50043428)". Scopus

The use of enzyme-based biosensors for the detection and quantification of analytes of interest such as contaminants of emerging concern, including over-the-counter medication, provides an attractive alternative compared to more established techniques. However, their direct application to real environmental matrices is still under investigation due to the various drawbacks in their implementation. Here, we report the development of bioelectrodes using laccase enzymes immobilized onto carbon paper electrodes modified with nanostructured molybdenum disulfide (MoS2). The laccase enzymes were two isoforms (LacI and LacII) produced and purified from the fungus Pycnoporus sanguineus CS43 that is native to Mexico. A commercial purified enzyme from the fungus Trametes versicolor (TvL) was also evaluated to compare their performance. The developed bioelectrodes were used in the biosensing of acetaminophen, a drug widely used to relieve fever and pain, and of which there is recent concern about its effect on the environment after its final disposal. The use of MoS2 as a transducer modifier was evaluated, and it was found that the best detection was achieved using a concentration of 1 mg/mL. Moreover, it was found that the laccase with the best biosensing efficiency was LacII, which achieved an LOD of 0.2 µM and a sensitivity of 0.108 µA/µM cm2 in the buffer matrix. Moreover, the performance of the bioelectrodes in a composite groundwater sample from Northeast Mexico was analyzed, achieving an LOD of 0.5 µM and a sensitivity of 0.015 µA/µM cm2. The LOD values found are among the lowest reported for biosensors based on the use of oxidoreductase enzymes, while the sensitivity is the highest currently reported.

In this work, we have synthesized BaWO4–MoS2 nanocomposites by the simple co-precipitation method and investigated their photocatalytic activities with Rhodamine-B as a test contaminant. The BaWO4/MoS2 photocatalyst was characterized by X-ray diffraction (XRD), Energy dispersive X-ray analysis (EDAX), Fourier Transform Infra-Red spectroscopy (FT-IR), and Scanning Electron Microscopy (SEM) and Brunauer–Emmett–Teller (B.E.T) techniques. The optical properties were investigated using the UV-Vis-DRS spectroscopy and a clear red shift has been observed in the bandgap energy of the synthesized BaWO4– MoS2. The nanocomposites exhibit a flower-like morphology with the required elemental composition of Ba, W, O, Mo and S. The photocatalytic activity of the BaWO4–MoS2 nanocomposites (75 mg) for dye (20 μM) removal is 95% upon a solar light exposure in 80 min. The photocatalytic reactions were found to obey the pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. The repeatability of photocatalytic activity was also studied. Studies on antimicrobial activity reveal that the nanoparticles possess inhibition activity against staphylococcus aureus, pseudomonas aeruginosa and Candida albicans.

Two-dimensional (2D) nanomaterials have attracted interest from the scientific community due to their unique properties. The production of these materials has been carried out by diverse methodologies, the liquid phase exfoliation being the most promising one due to its simplicity and potential scalability. The use of several stabilizers allows to obtain dispersions of these 2D nanomaterials in solvents with low boiling points. Herein we describe a general exfoliation method for different 2D materials employing a biphasic water/dichloromethane system and two different (poly)aromatic hydrocarbons (PAHs). This method allows us to obtain dispersions of the exfoliated 2D materials with high concentrations in the organic solvent. Due to the low boiling point of dichloromethane, and therefore its easy removal, the obtained dispersions can be employed as additives for different composites. We corroborate that the exfoliation efficiency is improved due to the π–π and van der Waals interactions between the PAHs and the layers of the 2D materials.

Made available in DSpace on 2021-06-25T11:10:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Here we present the study of supercapacitors based on molybdenum disulfide and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (MoS2/PEDOT:PSS) composite electrodes deposited by spray-coating. To produce the MoS2/PEDOT:PSS composite ink, dispersions of hydrothermally synthesized MoS2 and PEDOT:PSS were mixed in different weight proportions. Electrodes containing only PEDOT:PSS and MoS2 were also fabricated for comparison. The composite films were deposited by transferring the as-prepared inks to an airbrush coupled to a modified 3D printer base with in-line displacement. The films were characterized in terms of the scanning electron microscope (SEM), Raman spectroscopy, and sheet resistance. The electrochemical properties of supercapacitors were evaluated by cyclic voltammetry (CV), galvanostatic charge/discharges (GCD) techniques, impedance spectroscopy (IS), and their correlated parameters. The maximum specific capacitance of the MoS2-based supercapacitor was estimated to be 145.9 F g−1 at 1 mV s−1, while the 3:1 MoS2/PEDOT:PSS weight ratio supercapacitor exhibited a specific capacitance of 131.1 F g−1. Despite the slightly lower CSP, the 3:1 device provided a better overall performance, with a remarkably higher energy density of 11.2 Wh kg−1 and a maximum power density of 1020 W kg−1. It also displayed better long-term cycle stability, retaining 92% of its initial capacitance after 1000 CV cycles (against 54% of MoS2 devices). In summary, we demonstrated the study and production of a high-performance supercapacitor with spray-deposited MoS2/PEDOT:PSS composite electrodes, in which the production can be easily scalable for mass production and practical applications. School of Technology and Sciences São Paulo State University (UNESP) School of Technology and Sciences São Paulo State University (UNESP) FAPESP: 2018/02604-4

Herein, we quantitatively analyze the evolution of the subgap density of states (DOSs) for multilayered molybdenum disulfide (m-MoS2) field effect transistors (FETs) with bilayered SiNx/SiOx gate dielectrics under positive bias stress (PBS) and negative bias stress (NBS) by using optical charge-pumping capacitance-voltage spectroscopy. To decouple external gas ambient effects on device instability, hydrophobic fluoropolymers (cyclized transparent optical polymer; CYTOP) are employed for m-MoS2 FETs followed by the evaluation of subgap-DOSs in the devices for the respective PBS (or NBS). Through extraction of subgap-DOSs and their deconvolution with an analytical model of acceptor (or donor)-like states, it is shown that the device instability is closely correlated with state transitions of DOSs, corresponding to shallow (or midgap) levels for monosulfur vacancy (VS) (or disulfur vacancy ( $\text{V}_{\mathrm {S2}}$ )). Moreover, after PBS, the initial states of VS(0) (or $\text{H}_{\mathrm {S2}}$ (0)) transit toward VS (−1) (or $\text{H}_{\mathrm {S2}}(-1$ )) via electron trapping, whereas the transition toward VS (0) and $\text{H}_{\mathrm {S2}}$ (+1) during NBS is assessed from the initial $\text{V}_{\mathrm {S}}(-1$ ) and $\text{H}_{\mathrm {S2}}$ (0) states. Furthermore, technology computer-aided design (TCAD) simulation based on the extracted DOSs properly replicates the measured I-V characteristics of m-MoS2 FETs with (and without) CYTOP encapsulation. In this study, subgap-DOS characterization via optical charge pumping and validation of the quantitative evolution of subgap-DOSs suggest that this platform can be potentially beneficial for an in-depth understanding of the origins of device instability for transition metal dichalcogenide (MX2)-based FETs, where M is a transition metal and X is a chalcogenide.

A phenomenological model, accounting for interface states at metal-semiconductor contacts, is proposed to explain particular gate-bias-dependent kinking in I-V characteristics sometimes observed in MoS2 FETs. The effect is studied in double-gate FETs by varying top-gate voltage (VTG) and bottom-gate voltage (VBG), with the MoS2 semiconductor layer overlying source/drain (S/D) metal contacts in contact regions. The kink in ID-VTG characteristics is observed for small negative VBG but not for large negative VBG. The model divides the FET into S/D and channel regions, with bias-dependent S/D resistance (RSD) and channel resistance (RCHAN), and with S/D regions having an additional interface state distribution (additional to any interface states associated with semiconductor/dielectric interfaces in the channel region) due to an imperfect metal-semiconductor interface where MoS2 overlies S/D metal. The additional interface states are modeled as a Gaussian distribution of acceptor-like states in the upper region of the semiconductor bandgap. When RSD ≥ RCHAN (VBG less negative), filling of these acceptor-like states as VTG increases creates a kink in ID-VTG characteristics since RSD is a major component of overall resistance limiting drain current, ID. Conversely, when RSD << RCHAN (VBG more negative), filling of these acceptor-like states as VTG increases does not create an ID-VTG kink since RSD is not the major component of resistance limiting ID. The model highlights 1) metal-semiconductor interface states need to be accounted for when modeling MoS2 FETs, and 2) importance of forming metal-semiconductor interfaces with low interface state density to avoid I-V kinks which are detrimental for analog applications.

Oxygen is important in maintaining a clean and reliable water environment. Designing heterojunction photocatalysts that can evolve oxygen from water splitting through an artificial Z-scheme pathway is a promising strategy for solving environmental problems. In this study, flower-like MoS2 nanostructures were fabricated via a simple hydrothermal process, and the electrostatic-based assembly ion-exchange method was used to construct a tandem Ag3PO4/MoS2/g-C3N4 (AMC) heterojunction. The as-synthesized photocatalyst exhibited significant improvements in harvesting visible light and transporting charge carriers. Moreover, the catalyst that was similar to the Z-scheme with intimate interface contact exhibited a strong oxygen evolution performance. The oxygen evolution activity of the optimal AMC-10 catalyst was approximately 11 times that of the pristine Ag3PO4. The results indicated that addition of a small amount of the flower-like MoS2 could significantly enhance the efficiency of oxygen evolution by the heterojunction. The findings in this study provide an alternative pathway for rationally designing efficient oxygen-evolving photocatalysts in order to improve the quality of water and rehabilitate the water environment.

For lithium–sulfur batteries, 3D cathodes might be of interest for containing the active material and trapping the polysulfides during cycling, owing to their binder-free and freestanding features. In this work, the MoS2 grown on the 3D structured Carbon Cloth (CC@MoS2) is firstly used to fabricate the Li–S battery and the sulfur loading can be freely tuned by adjusting thermal annealing time at 200 °C. A two-step melt-diffusion strategy is reported for fabrication of cathodes, which involves in melting and diffusion of sulfur covered by CC@MoS2 composites instead of dissolution of sulfur in the toxic organic solvents. Compared with the non-polar carbon cloth, the CC@MoS2 composites exhibit better adsorption capacity for polysulfides due to more edge active sites, which could effectively facilitate polysulfide redox kinetics. The SEM images of the CC@MoS2 cathode after 300 cycles show that MoS2 can still maintain the nanosheet morphology. After 300 cycles at 0.5 C, the CC@MoS2 cathodes loaded with 2 mg sulfur exhibit a better reversible capacity of 698 mA h g−1 compared with CC@MoS2 loaded with 1 mg sulfur (604 mA h g−1) and CC@MoS2 loaded with 4 mg sulfur (420 mA h g−1). This work proposes an environmentally friendly method to fabricate the lithium–sulfur battery cathode material and the sulfur loading can be freely adjusted.

Van der Waals heterostructures have attracted increasing interest, owing to the combined benefits of their constituents. These hybrid nanostructures can be realized via epitaxial growth, which offers a promising approach for the controlled synthesis of the desired crystal phase and the interface between van der Waals layers. Here, the epitaxial growth of a continuous molybdenum disulfide (MoS2) film on large-area graphene, which was directly grown on a sapphire substrate, is reported. Interestingly, the grain size of MoS2 grown on graphene increases, whereas that of MoS2 grown on SiO2 decreases with an increasing amount of hydrogen in the chemical vapor deposition reactor. In addition, to achieve the same quality, MoS2 grown on graphene requires a much lower growth temperature (400 °C) than that grown on SiO2 (580 °C). The MoS2/graphene heterostructure that was epitaxially grown on a transparent platform was investigated to explore its photosensing properties and was found to exhibit inverse photoresponse with highly uniform photoresponsivity in the photodetector pixels fabricated across a full wafer. The MoS2/graphene heterostructure exhibited ultrahigh photoresponsivity (4.3 × 104 A W–1) upon exposure to visible light of a wide range of wavelengths, confirming the growth of a high-quality MoS2/graphene heterostructure with a clean interface.

openaire: EC/H2020/720964/EU//npSCOPE Two-dimensional (2D) materials with nanometer-size holes are promising systems for DNA sequencing, water purification, and molecule selection/separation. However, controllable creation of holes with uniform sizes and shapes is still a challenge, especially when the 2D material consists of several atomic layers as, e.g., MoS2, the archetypical transition metal dichalcogenide. We use analytical potential molecular dynamics simulations to study the response of 2D MoS2 to cluster irradiation. We model both freestanding and supported sheets and assess the amount of damage created in MoS2 by the impacts of noble gas clusters in a wide range of cluster energies and incident angles. We show that cluster irradiation can be used to produce uniform holes in 2D MoS2 with the diameter being dependent on cluster size and energy. Energetic clusters can also be used to displace sulfur atoms preferentially from either top or bottom layers of S atoms in MoS2 and also clean the surface of MoS2 sheets from adsorbents. Our results for MoS2, which should be relevant to other 2D transition metal dichalcogenides, suggest new routes toward cluster beam engineering of devices based on 2D inorganic materials.

Polyindole (PIn) has attracted extensive interest as promising energy storage materials owing to fairly good thermal stability, high redox activity and stability, however, it is challenging to prepare high-quality PIn in neutral solvents by electrochemical method. Herein, a simple route, based on MoS2 nanosheets as electrolytes, has been developed for the electrochemical preparation of PIn/MoS2 nanocomposite in acetonitrile solution. Due to the coordination interaction between indole and MoS2, the onset oxidation potential of indole in this medium was reduced to 0.5 V from 0.75 V determined in acetonitrile/LiClO4. The morphologies and structures of as-obtained PIn/MoS2 nanocomposite were characterized using SEM, TEM, XRD, Raman and XPS. The results of thermal analysis indicated that the PIn/MoS2 nanocomposite had an improved thermal stability relative to PIn and MoS2 nanosheets. Moreover, the specific capacitance of PIn/MoS2 nanocomposite was 8.3 times higher than that of PIn prepared acetonitrile/LiClO4. To the best of our knowledge, this is the first report on the high-efficiency electrodeposition of PIn/MoS2 nanocomposite in MoS2-based acetonitrile solution, which will be a promising candidate as a high efficient electrode material in the application of supercapacitors.

The variation of the electronic structure normal to 1D defects in quasi-freestanding MoS$_2$, grown by molecular beam epitaxy, is investigated through high resolution scanning tunneling spectroscopy at $5$K. Strong upwards bending of valence and conduction bands towards the line defects is found for the 4|4E mirror twin boundary and island edges, but not for the 4|4P mirror twin boundary. Quantized energy levels in the valence band are observed wherever upwards band bending takes place. Focusing on the common 4|4E mirror twin boundary, density functional theory calculations give an estimate of its charging, which agrees well with electrostatic modeling. We show that the line charge can also be assessed from the filling of the boundary-localized electronic band, whereby we provide a measurement of the theoretically predicted quantized polarization charge at MoS$_2$ mirror twin boundaries. These calculations elucidate the origin of band bending and charging at these 1D defects in MoS$_2$. The 4|4E mirror twin boundary not only impairs charge transport of electrons and holes due to band bending, but holes are additionally subject to a potential barrier, which is inferred from the independence of the quantized energy landscape on either side of the boundary.

openaire: EC/H2020/820423/EU//S2QUIP | openaire: EC/H2020/834742/EU//ATOP Monolayer transition-metal dichalcogenides show strong optical nonlinearity with great potential for various emerging applications. Here we demonstrate the gate-tunable interband resonant four-wave mixing and sum-frequency generation in monolayer MoS2. Up to 80% modulation depth in four-wave mixing is achieved when the generated signal is resonant with the A exciton at room temperature, corresponding to an effective third-order optical nonlinearity |χ(3)eff| tuning from (∼12.0 to 5.45) × 10-18 m2/V2. The tunability of the effective second-order optical nonlinearity |χ(2)eff| at 440 nm C-exciton resonance wavelength is also demonstrated from (∼11.6 to 7.40) × 10-9 m/V with sum-frequency generation. Such a large tunability in optical nonlinearities arises from the strong excitonic charging effect in monolayer transition-metal dichalcogenides, which allows for the electrical control of the interband excitonic transitions and thus nonlinear optical responses for future on-chip nonlinear optoelectronics.

Two dimensional materials offer a path forward for smaller and more efficient devices. Their optical and electronic properties give way to beat the limits set in place by Moore's Law. Plasmon are the collective oscillations of electrons and can confine light to dimensions much smaller than its wavelength. In this work we explore the plasmonic properties of MoS2, a representational candidate from a family of 2D materials known as transition metal dichalcogenides. High resolution electron microscopy and spectroscopy provide insights in the plasmonic properties of MoS2 down to an atomic scale. Experimental results show the relationship between plasmons and interband transitions in the electron energy loss spectrum. Density functional theory provides a theoretical support for the experimental findings and provides commentary on the fundamental underlying physics., Comment: 16 pages, 5 figures, Electron Microscopy Analysis Group (EMAG) special issue

Recently, transition metal dichalcogenides (TMDs) have gained great attention owing to their remarkable properties. The electronic structure of TMDs can be modified by substitutional doping, which could give rise to novel and exciting properties. In this study, a strategy is presented for controlled vanadium (V) doping of MoS2, in which V doped MoS2 films with good uniformity are prepared by thermal sulfurization of V-Mo alloy films deposited using co-sputtering. The V incorporation in MoS2 induces p type doping, which enhances the electrical conductivity of MoS2 by a factor of 35-40. Such doping strategy and consequent conductivity improvement may be useful in many applications such as catalysis, nanoelectronics and optoelectronics.

Rotary actuator is a device responsible for the precise rotation of sensitive instruments such as antennas. Requirements for its precision and stiffness are extremely high. Actuators used in the space environment have to work for long period, under extreme condition and without possibility of repair or replacement. One of the main components responsible for its proper function are bearings. They precisely support shafts, and usually operate in a very small angular range with many repetitions. Selection of the proper bearing design and also the lubrication of the bearing can have significant effect on the performance and life of the entire satellite. Purpose of this study was to select and test suitable lubricant to support operation of such bearing. Sets of bearings lubricated by Rheolube 2000 and MoS2 PVD film were tested in thermal vacuum chamber under small angle oscillatory motion with the same start and end position for every cycle. Torque and bearing noise was evaluated during the tests and bearings were inspected. Rheolube 2000 was selected as the best lubricant for the described conditions because of the acceptable torque, lower bearing noise and easier manipulation during assembly and testing. However, both options proved to be applicable.

The MoS2 photodetector on different substrates stacked via van der Waals force has been explored extensively because of its great potential in optoelectronics. Here, we integrate multilayer MoS2 on monocrystalline SiC substrate though direct chemical vapor deposition. The MoS2 film on SiC substrate shows high quality and thermal stability, in which the full width at half-maximum and first-order temperature coefficient for the E 2 g 1 $E_{2g}^1$ Raman mode are 4.6 cm−1 and −0.01382 cm−1/K, respectively. The fabricated photodetector exhibits excellent performance in the UV and visible regions, including an extremely low dark current of ~1 nA at a bias of 20 V and a low noise equivalent of 10−13–10−15 W/Hz1/2. The maximum responsivity of the MoS2/SiC photodetector is 5.7 A/W with the incident light power of 4.35 μW at 365 nm (UV light). Furthermore, the maximum photoconductive gain, noise equivalent power, and normalized detectivity for the fabricated detector under 365 nm illumination are 79.8, 7.08 × 10−15 W/Hz1/2, and 3.07 × 1010 Jonesat, respectively. We thus demonstrate the possibility for integrating high-performance photodetectors array based on MoS2/SiC via direct chemical vapor growth.

Weaker Fermi level pinning (FLP) at the Schottky barriers of 2D semiconductors is electrically desirable as this would allow a minimizing of contact resistances, which presently limit device performances. Existing contacts on MoS2 have a strong FLP with a small pinning factor of only ∼0.1. Here, we show that Moire interfaces can stabilize physisorptive sites at the Schottky barriers with a much weaker interaction without significantly lengthening the bonds. This increases the pinning factor up to ∼0.37 and greatly reduces the n-type Schottky barrier height to ∼0.2 eV for certain metals such as In and Ag, which can have physisorptive sites. This then accounts for the low contact resistance of these metals as seen experimentally. Such physisorptive interfaces can be extended to similar systems to better control SBHs in highly scaled 2D devices.

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Nos últimos anos, pesquisadores buscaram compilar estudos sobre os efeitos da texturização em ferramentas de corte. Nota-se uma clara convergência entre as conclusões, todavia, existem ainda parâmetros cujos resultados divergem drasticamente entre os autores. Uma das possíveis causas de resultados tão divergentes consiste na diferença entre as propriedades dos materiais estudados por cada pesquisador. Logo, os efeitos das texturas nos materiais estudados em menor número na literatura acabam sendo mascarados, como é o caso do alumínio, um material que apesar de ser amplamente utilizado nas indústrias, corresponde à apenas 16 % dos materiais estudados nos últimos 5 anos. A aplicação de ferramentas texturizadas na usinagem do alumínio aliada a uma ferramenta de alta resistência como o PCD torna-se altamente viável, pois nesta combinação não há desgaste significante, ao contrário da maioria dos casos em que há um desgaste rápido na ferramenta que consome a textura em um pequeno percurso de usinagem, diminuindo ou anulando seu efeito. Assim, este trabalho realizou testes de torneamento da liga de Alumínio 2011-T4, com ferramentas de PCD com diferentes tipos de texturas (canais paralelos e perpendiculares à aresta principal de corte), variando-se a condição de lubrificação (seco e com aplicação de MoS2) e a velocidade de corte. Testes com ferramentas sem texturas (lisas) também foram conduzidos para comparação. As texturas foram usinadas por laser femtossegundos de Ti:safira, variando-se a direção, profundidade e largura dos canais. Os parâmetros considerados nos experimentos foram força de corte, temperatura de usinagem, rugosidade das superfícies usinadas e morfologia dos cavacos. Foram observadas as condições favoráveis à produção da textura e o comportamento das mesmas durante o torneamento. As texturas beneficiam a quebra do cavaco e consequentemente a dissipação do calor gerado. A presença de lubrificante evitou o empastamento de material dentro das texturas, reduzindo o atrito, portanto o MoS2 favoreceu o corte em relação à redução das forças e temperaturas, porém não houve aprimoramento em relação à rugosidade da peça. Também foi constado que as texturas exerceram grande influência na força de avanço, mas esta é apenas uma pequena parcela da força de usinagem, assim, a pequena influência na força de corte foi o que determinou o resultado final na força de usinagem. As texturas perpendiculares à aresta de corte com lubrificante foram as que apresentaram os melhores resultados em relação às ferramentas sem textura: a textura com dimensões menores reduziu a força de usinagem em mais de 7 %, e a temperatura em 9 %, enquanto a textura de dimensões maiores reduziu a rugosidade Ra da peça em 49 %. In recent years, researchers have tried to compile studies on the effects of texturing on cutting tools. There is a clear convergence of the conclusions, however, there are still parameters whose results drastically diverge among the authors. One of the possible causes of such divergent results is the difference between the properties of the materials studied by each researcher. Therefore, the effects of textures on materials studied in smaller numbers in the literature end up being masked, as is the case of aluminum, a material that, despite being widely used in industries, corresponds to only 16% of the materials studied in the last 5 years. The application of textured tools in aluminum machining combined with a high-strength tool such as PCD becomes highly viable, because in this combination there is no significant tool wear, unlike in most cases where there is rapid tool wear that consumes the texture in a short machining path, nullifying its effect. Thus, this work carried out turning tests in 2011-T4 aluminum alloy with PCD tools with different types of texture (parallel and perpendicular channels to the main cutting edge), varying the lubri-cooling condition (dry and with the addition of MoS2) and cutting speed. Tests with non-textured tools were also performed for comparisons. The textures were machined by a femtoseconds Ti:sapphire laser, varying the direction, depth and width of the channels. The output parameters considered in the experiments were the cutting forces, cutting temperature, workpiece surface roughness and chip morphology. Favorable conditions for texture production and their behavior during turning were observed. The textures helped to break the chips and consequently the dissipation of the heat generated. The presence of lubricant avoided the material clogging inside the textures, reducing friction, so the MoS2 favored the cut in relation to the reduction of forces and temperatures, however there was no improvement in relation to the roughness of the piece. It was observed that textures have a large influence on the feed force, but this component was only a small percentage of the machining force, and therefore the small influence on the cutting force was what determined the final result in the machining force. Textures with channels perpendicular to the main cutting edge with lubricant showed the best results when compared to non-textured tools: the textures with smaller dimensions reduced the machining force by more than 7 %, and the temperature by 9 %, while the textures with larger dimensions reduced the surface roughness parameter Ra by 49 %. Keywords: Laser texturing, PCD tools, Aluminum 2011-T4 alloy, MoS2. Dissertação (Mestrado)

Potassium-ion batteries (PIBs) have aroused a large amount of interest recently due to the plentiful potassium resource, which may show cost benefits over lithium-ion batteries (LIBs). However, the huge volume expansion induced by the intercalation of large-sized potassium ions and the intrinsic sluggish kinetics of the anode hamper the application of PIBs. Herein, by rational design, nano-roses assembled from petals with a MoS2/monolayer carbon (C-MoS2) sandwiched structure were successfully synthesized. The interlayer distance of ultrathin C-MoS2 was expanded from original MoS2 of 6.2 to 9.6 Å due to the formation of the MoS2-carbon inter overlapped superstructure. This unique structure efficiently alleviates the mechanical strain, prevents the aggregation of MoS2, creates more active sites, facilitates electron transport, and enhances the specific capacity and K+ diffusion kinetics. As a result, the prepared C-MoS2-1 anode delivers a high reversible specific capacity (437 mAh g−1 at 0.1 A g−1) and satisfying rate performance (123 mAh g−1 at 6.4 A g−1). Therefore, this work provides new insights into the design of high-performance anode materials of PIBs.

The electrocatalytic hydrogen evolution activity of transition metal sulfide heterojunctions are significantly increased when compared with that of a single component, but the mechanism behind the performance enhancement and the preparation of catalysts with specific morphologies still need to be explored. Here, we prepared a Co9S8/MoS2 heterojunction with microsphere morphology consisting of thin nanosheets using a facile two-step method. There is electron transfer between the Co9S8 and MoS2 of the heterojunction, thus realizing the redistribution of charge. After the formation of the heterojunction, the density of states near the Fermi surface increases, the d-band center of the transition metal moves downward, and the adsorption of both water molecules and hydrogen by the catalyst are optimized. As a result, the overpotential of Co9S8/MoS2 is superior to that of most relevant electrocatalysts reported in the literature. This work provides insight into the synergistic mechanisms of heterojunctions and their morphological regulation.

We report on the facile and scalable catalytic conversion of natural graphite and MoS2 minerals into α-MoO3 nanoribbons incorporated into hexagonal MoS2 and graphene nanosheets, and evaluate the structural, morphological and electrochemical performances of the hybrid nanostructured material obtained. Mechanochemical treatment of raw materials, followed by catalytic molten salt treatment leads to the formation of nanostructures with promising electrochemical performances. We examined the effect of processing temperature on the electrochemical performance of the products. At 1100 °C, an excellent Li-ion storage capacity of 773.5 mAh g−1 is obtained after 180 cycles, considerably greater than that of MoS2 (176.8 mAh g−1). The enhanced capacity and the rate performance of this electrode are attributed to the well-integrated components, characterized by the formation of interfacial molybdenum oxycarbide layer during the synthesis process, contributing to the reduced electrical/electrochemical resistance of the sample. This unique morphology promotes the charge and ions transfer through the reduction of the Li-ion diffusion coefficient (1.2 × 10−18 cm2 s−1), enhancing the pseudocapacitive performance of the electrode; 59.3% at the scan rate of 0.5 mV s−1. This article provides a green and low-cost route to convert highly available natural graphite and MoS2 minerals into nanostructured hybrid materials with promising Li-ion storage performance.

Lubricants are essential to machinery life, as they play a crucial role in controlling and diminishing the friction and wear between moving parts when operated under extreme conditions. To this end, due to tight environmental conditions, manufacturers are looking for alternative solid lubricants to be dispersed in base liquid lubricants. MoS2 and graphene are solid lubricants that provide low frictional properties and high thermal stability in both oxidizing and non-oxidizing environments. This research offers a new lubricant with improved thermal conductivity that combines the synergistic effect of graphene and MoS2 in a blend of vegetable oil (peanut) and naphthenic oil. The ratio of peanut oil and naphthenic oil varies from 1:3–3:1. A fixed composition of 4.34 wt.% palm oil methyl ester (POME) is added to enhance the anti-wear property further. Graphene and MoS2 concentrations varied between 1:2–5:2, respectively. This nanoparticle additive oil blend is physically mixed using a water bath sonication for 4 h. The stability of the blend lubricant dispersed with MoS2 and graphene is studied using a UV-Vis spectrophotometer for 25 days. The effect of various concentrations of graphene, MoS2, peanut oil, and naphthenic oil on the thermal conductivity of the nanolubricant is also studied as a function of temperature (25 °C–55 °C). Artificial neural network models were used for the parametric investigation of the nanolubricant. It is found that the stability of the formulated nanolubricant increased with peanut oil composition above 25 wt.%. The results show that the 3:1 blend ratio showed higher stability for hybrid MoS2-based lubricants. Similarly, the highest thermal conductivity is observed for 100 wt.% naphthenic oil with a 1:2 ratio of graphene–MoS2 at 55 °C.

Among the transitional metal dichalcogenides (TMDCs), molybdenum disulfide (MoS2) is considered an outstanding candidate for biosensing applications due to its high absorptivity and amenability to ionic current measurements. Dielectric metasurfaces have also emerged as a powerful platform for novel optical biosensing due to their low optical losses and strong near-field enhancements. Once functionalized with TMDCs, dielectric metasurfaces can also provide strong photon–exciton interactions. Here, we theoretically integrated a single layer of MoS2 into a CMOS-compatible asymmetric dielectric metasurface composed of TiO2 meta-atoms with a broken in-plane inversion symmetry on an SiO2 substrate. We numerically show that the designed MoS2-integrated metasurface can function as a high-figure-of-merit (FoM=137.5RIU−1) van der Waals-based biosensor due to the support of quasi-bound states in the continuum. Moreover, owing to the critical coupling of the magnetic dipole resonances of the metasurface and the A exciton of the single layer of MoS2, one can achieve a 55% enhanced excitonic absorption by this two-port system. Therefore, the proposed design can function as an effective biosensor and is also practical for enhanced excitonic absorption and emission applications.

Herein, a full spectrum-induced hybrid structure consisting of one-dimensional nickel titanate (NiTiO3) nanofibers (NFs) decorated by petal-like molybdenum disulfide (MoS2) particles was designed through a facile hydrothermal method. The key parameters for tailoring the morphology and chemical, surface, and interfacial properties of the heterostructure were identified for efficient and selective conversion of CO2 into valuable chemicals. Introducing MoS2 layers onto NiTiO3 NFs provided superior CO2 conversion with significantly higher yields. The optimized hybrid structure produced CO and CH4 yields of 130 and 55 μmol g−1 h−1, respectively, which are 3.8- and 3.6-times higher than those from pristine NiTiO3 nanofibers (34 and 15 μmol g−1 h−1, respectively) and 3.6- and 5.5-times higher than those from pristine MoS2 (37 and 10 μmol g−1 h−1, respectively). This improved performance was attributed to efficient absorption of a wider spectrum of light and efficient transfer of electrons across the heterojunction. Effective charge separation and reduced charge carrier recombination were confirmed by photoluminescence and impedance measurements. The performance may also be partly due to enhanced hydrophobicity of the hierarchical surfaces due to MoS2 growth. This strategy contributes to the rational design of perovskite-based photocatalysts for CO2 reduction.

We demonstrate a graphene–MoS2 architecture integrating multiple field-effect transistors (FETs), and we independently probe and correlate the conducting properties of van der Waals coupled graphene–MoS2 contacts with those of the MoS2 channels. Devices are fabricated starting from high-quality single-crystal monolayers grown by chemical vapor deposition. The heterojunction was investigated by scanning Raman and photoluminescence spectroscopies. Moreover, transconductance curves of MoS2 are compared with the current–voltage characteristics of graphene contact stripes, revealing a significant suppression of transport on the n-side of the transconductance curve. On the basis of ab initio modeling, the effect is understood in terms of trapping by sulfur vacancies, which counterintuitively depends on the field effect, even though the graphene contact layer is positioned between the backgate and the MoS2 channel.

This dataset contains the following structures, that are used in: K. Almeida, K.L. Chagoya, A. Felix, T. Jiang, D. Le, T.B. Rawal, P.E. Evans, M. Wurch, K. Yamaguchi, P.A. Dowben, L. Bartels, T.S. Rahman, and R.G. Blair, "Methanol carbonylation to acetaldehyde on Au particles supported by single-layer MoS2 grown on silica," Journal of Physics: Condensed Matter (2021). DOI:10.1088/1361-648X/ac40ad 1. Au13-MoS2.extxyz 2. CO.extxyz 3. H2.extxyz 4. CH3.extxyz 5. CH3CO.extxyz 6. CH3CHO.extxyz 7. CH3+CO_CH3CO_IS.extxyz 8. CH3+CO_CH3CO_TS.extxyz 9. CH3+CO_CH3CO_FS.extxyz 10. CH3CO+H_CH3CHO_IS.extxyz 11. CH3CO+H_CH3CHO_TS.extxyz 12. CH3CO+H_CH3CHO_FS.extxyz #File format All data ara written in extxyz, which includes coordinates of atoms, dimension of supercell, force components acting on each atom, total energy. Instruction on reading the data can be found at https://wiki.fysik.dtu.dk/ase/ase/io/formatoptions.html#extxyz #Other files get_energy.py: reproducing computational data reported in the paper. POTCAR: Potential files used in the calculations. &nbsp

Hierarchically two-dimensional (2D) heteroarchitecture with ultrafine MoS2 nanosheets vertically patterned on graphene is developed by using a facile solvothermal method. It is revealed that the strong interfacial interaction between acidic Mo precursors and graphene oxides allows for uniform and tight alignment of edge-oriented MoS2 nanosheets on planar graphene. The unique sheet-on-sheet architecture is of grand advantage in synergistically utilizing the highly conductive graphene and the electroactive MoS2, thus rendering boosted reaction kinetics and robust structural integrity for energy storage. Consequently, the heterostructured MoS2@graphene exhibits impressive Li/Na-ion storage properties, including high-capacity delivery and superior rate/cycling capability. The present study will provide a positive impetus on rational design of 2D metal sulfide/graphene composites as advanced electrode materials for high-efficient alkali–metal ion storage.