Pure MoS2 Research Articles

Componential and molecular-weight-dependent effects of natural organic matter on the colloidal behavior, transformation, and toxicity of MoS2 nanoflakes

The potential widespread applications in water processing have rendered the necessity for investigations of the fate and hazard of molybdenum disulfide (MoS2) nanosheets. Herein, it was found that humic acid (HA) had better performances toward stabilizing pure 2H phase MoS2 and chemical-exfoliated MoS2 (ce-MoS2) in electrolyte solutions than fulvic acid (FA), and molecular weight (MW)-dependent manners were disclosed due to steric repulsions. Compared with darkness, the extent to which the aggregation and sedimentation of ce-MoS2 facilitated by visible light irradiation was greater in the presence of HA and FA fractions, likely due to the introduction of stronger plasmonic dipole-dipole interaction and Van der Waals attraction forces. HA-triggered structural disintegration of nanosheets was performed after irradiation and it was observed to be more significant with the increase in MWs, whereas the MW-dependent dissolution of MoS2 caused by FA was much quicker than that by HA owing to the higher generation of singlet oxygen. Moreover, FA lowered the bioavailability of MoS2 and relieved its toxicity to zebrafish more effectively than HA. Our findings boost the insights into the effects of organic molecules on the fates and hazards of MoS2, providing guidance for the MoS2-based nanotechnological development on environment.

Construction of UiO-66-NH2 decorated by MoS2 QDs as photocatalyst for rapid and effective visible-light driven Cr(VI) reduction

The photoactive metal-organic frameworks (MOFs) are good candidates for photocatalysts, but the quick electron-hole pairs recombination has greatly restricted the photocatalytic ability of MOFs. To improve the photoactivity of MOFs, MOFs-based composite materials have been extensively studied. Here, we successfully integrated MoS2 quantum dots (QDs) with UiO-66-NH2 for the first time under hydrothermal conditions. The as-prepared MoS2 QDs/UiO-66-NH2 (MS-U) had good visible light response ability (absorption edge at 445 nm), and charge separation and transfer ability, which lays the foundation for the photocatalytic Cr(VI) reduction. Photocatalytic studies revealed that MoS2 QDs-5/UiO-66-NH2 (MS-U-5) had superior Cr(VI) reduction activity than pure MoS2 QDs and UiO-66-NH2. MS-U-5 could remove 98% Cr(VI) at pH= 2 with visible light irradiation for 20 min, which is the fastest visible light driven Cr(VI) reduction rate among the reported MOFs-based composite photocatalysts without the presence of any cocatalysts or scavengers as far as we know. Importantly, MS-U-5 could be reused at least three times. In the end, the possible electron transfer path and mechanism of Cr(VI) reduction was also investigated.

Epitaxial growth of bilayer MoS2/MoSe2 heterostructure with high-responsivity enhanced by photogating effect

Van der Waals (vdW) semiconductors heterostructure based on transition metal dichalcogenides (TMDs) is a promising candidate for two-dimensional (2D) ultra-thin optoelectronic devices due to the strongly interlayer coupling and efficient carrier separation. However, the directly epitaxial growth of 2D TMDs vdW heterostructures with a clean interface and high photoresponsivity still remains a challenging. In this work, the epitaxial growth of bilayer MoS2/MoSe2 vdW heterostructure with atomic-layer clean interface is prepared via an iodine-assisted growth strategy. The electrical properties and optoelectronic characterization proves that the heterostructure device presents an enhanced photoresponsivity of 680 A/W, indicting the 21.25 times higher compared with pure MoS2, which benefited from the photogating effect formed by the localized electrons in this heterostructure. This study offers a well reference for the controlled growth of the TMDs vdW heterostructure, and the achieved heterostructure will prove promising applications in future integrated optoelectronic devices and systems.

Highly Efficient Photocatalysts: Polyoxometalate Synthons Enable Tailored CdS-MoS2 Morphologies and Enhanced H2 Evolution.

The development of photocatalysts toward highly efficient H2 evolution reactions is a feasible strategy to achieve the effective conversion of solar energy and meet the increasing demand for new energy. To this end, we prepared two different CdS-MoS2 photocatalysts with unique morphologies ranging from hexagonal prisms to tetragonal nanotubes by carefully tuning polyoxometalate synthons. These two photocatalysts, namely, CdS-MoS2-1 and CdS-MoS2-2, both exhibited remarkable photocatalytic efficiency in H2 generation, among which CdS-MoS2-2 showed superior performance. In fact, the best catalytic hydrogen desorption rate of CdS-MoS2-2 is as high as 1815.5 μmol g-1 h-1. Such performance is superior to twice that of single CdS and almost four times that of pure MoS2. This obvious enhancement can be accredited to the highly open nanotube morphology and highly dispersed heterometallic composition of CdS-MoS2-2, which represents an excellent example of the highest noble-metal-free H2 evolution photocatalysts reported so far. Taken together, these findings suggest that the development of highly dispersed heterometallic catalysts is an auspicious route to realize highly efficient conversion of solar energy and that CdS-MoS2-2 represents a major advance in this field.

Eco-friendly sustainable machining with MoS2-based solid lubricant

Machining is one of the basic and inevitable operations in the manufacturing industry. The machining performance is estimated based on various parameters like cutting forces, surface roughness, tool–chip interface temperature, and specific energy. In the traditional approach, cutting fluids are greatly utilized to dissipate the generated heat during machining, but their utilization causes a threat to nature and human being’s health. Therefore, there emerges a necessity to determine user-friendly, sustainable, and eco-friendly substitutes for traditional cutting fluids. The field of advanced tribology has proposed the usage of solid lubricants due to their inherent properties, such as excellent tribological performance, reduced machining zone temperature due to lowered friction, and enhanced tool life. Therefore, in the present study, pure MoS2 and composite MoS2–TiO2 solid lubricants have been employed in the milling process of AISI 52100 steel with HSS end mill cutter. The machining was carried out in different conditions such as uncoated tool without use of lubricant, uncoated tool with use of lubricant, coated tool without use of lubricant, and coated tool with use of lubricant that were employed to analyze their effect on machining performance. The experimental results showed substantial improvement regarding reduced cutting forces, reduced temperature at tool–chip interface, improved surface finish, and average tool wear with the application of solid lubricants. Among the various lubricating conditions, composite MoS2–TiO2-coated tool with composite MoS2–TiO2 lubricant exhibits excellent machining performance.

CVD Synthesis of MoS2 Using a Direct MoO2 Precursor: A Study on the Effects of Growth Temperature on Precursor Diffusion and Morphology Evolutions.

In this study, the influence of growth temperature variation on the synthesis of MoS2 using a direct MoO2 precursor was investigated. The research showed that the growth temperature had a strong impact on the resulting morphologies. Below 650 °C, no nucleation or growth of MoS2 occurred. The optimal growth temperature for producing continuous MoS2 films without intermediate-state formation was approximately 760 °C. However, when the growth temperatures exceeded 800 °C, a transition from pure MoS2 to predominantly intermediate states was observed. This was attributed to enhanced diffusion of the precursor at higher temperatures, which reduced the local S:Mo ratio. The diffusion equation was analyzed, showing how the diffusion coefficient, diffusion length, and concentration gradients varied with temperature, consistent with the experimental observations. This study also investigated the impact of increasing the MoO2 precursor amount, resulting in the formation of multilayer MoS2 domains at the outermost growth zones. These findings provide valuable insights into the growth criteria for the effective synthesis of clean and large-area MoS2, thereby facilitating its application in semiconductors and related industries.

Enhanced thermoelectric performance of MoS2-Bi2S3 nanocomposites via low energy carrier filtering effect

Layered MoS2 (Molybdenum disulphide), an important transition metal dichalcogenide for energy conversion application due to intrinsic low thermal conduction and attractive functional properties. Here, we report on the hydrothermally prepared MoS2/Bi2S3 nanocomposites for mid-temperature thermoelectric applications. X-ray photo electron Spectroscopy reveals the change in fermi level of nanocomposites with Bi incorporation and oxidation states of the elements. High-Resolution Transmission Electron Microscope (HR-TEM) clearly indicates the formation of MoS2 nanosheets and Bi2S3 nano wires with the presence of interfaces. The interfacial effect greatly improved the thermoelectric power factor of 900 nW/mK2, which is nearly 8 times higher than pure MoS2.

Need for complementary techniques for reliable characterization of MoS2-like layers

The observation of characteristic A1g and E2g1 peaks, at around 408 and 382 cm−1, respectively, in Raman spectroscopy is considered the evidence of 2H-structured MoS2, probably the most extensively studied transition-metal dichalcogenide. Here, using a combination of x-ray diffraction, x-ray photoelectron spectroscopy, and resonant Raman spectroscopy, we show that the detection of A1g and E2g1 modes in Raman spectra alone may not necessarily imply the presence of MoS2. A series of Mo–S films, ≈ 20-nm-thick, are grown on single-crystalline Al2O3(0001) substrates at 1073 K as a function of H2S partial pressure, pH2S (= 0, 0.01%, 0.1%, and 1% of total pressure) via ultra-high vacuum dc magnetron sputtering of a Mo target in 20 m Torr (2.67 Pa) Ar/H2S gas mixtures. In pure Ar discharges and with pH2S up to 0.1%, i.e., pH2S ≤ 2.67 × 10−3 Pa, we obtain body centered cubic (bcc), 110-textured films with lattice parameter a increasing from 0.3148 nm (in pure Ar) to 0.3151 nm (at pH2S = 2.67 × 10−4 Pa), and 0.3170 nm (at pH2S = 2.67 × 10−3 Pa), which we attribute to increased incorporation of S in the Mo lattice. With 1% H2S, i.e., pH2S = 2.67 × 10−2 Pa, we obtain 000l oriented 2H-structured MoS2.0±0.1 layers. Raman spectra of the thin films grown using 0.1% (and 1%) H2S show peaks at around 412 (408) and 380 cm−1 (382 cm−1), which could be interpreted as A1g and E2g1 Raman modes for 2H-MoS2. By comparing the Raman spectra of MoS2.0±0.1 and Mo:S thin films, we identify differences in A1g and E2g1 peak positions and intensities of defect-sensitive peaks relative to the A1g peaks that can help distinguish pure MoS2 from non-stoichiometric MoS2−x and multiphase Mo:S materials.

Molybdenum disulfide/carbon multilayer films achieve ultra‐low wear in vacuum

Although diamond‐like carbon (DLC) films are known for their low friction and wear properties in atmospheric environments, they commonly experience failure in vacuum environments. On the other hand, MoS2 exhibits a low friction coefficient under vacuum conditions, but its columnar structure limits its load‐bearing capacity and results in high wear rates. In this study, we prepared MoS2/DLC multilayer films using a high‐power impulse magnetron sputtering (HIPIMS) technique and examined the composition, bonding structure, mechanical properties, and frictional wear of the resulting films. The study findings revealed that the multilayer film exhibits a significantly low coefficient of friction (0.04), particularly in vacuum conditions (5 × 10−3 Pa). Remarkably, compared to the pure MoS2 film, the wear rate of the multilayer film is reduced by two orders of magnitude, wear rate as low as 3.6 × 10−9 mm3/Nm. Additionally, the DLC component enhances the hardness and reduces the wear rate of the multilayer film. Furthermore, the use of nanometer thickness (17 nm) allows for the incorporation of more MoS2 and DLC layers, which promotes the formation of graphene bands and further reduces the friction coefficient and wear rate. Our findings open new avenues for the application of MoS2 and DLC in vacuum environments.

Vacancy engineering of MoS2−X @NCNTs for efficient storage of zinc ions

Zinc-ion batteries are receiving interest due to their high level of safety and eco-friendliness. However, the sluggish diffusion kinetics of zinc ions in the electrode limit its practical application. In this paper, rapid Zn2+ diffusion in the MoS2−X @NCNTs cathode is achieved by utilizing the S vacancies generated under a H2/Ar atmosphere and N-doped carbon nanotubes (NCNTs) derived from the pyrolysis of polyethylene and melamine. The presence of S vacancies significantly reduces the diffusion barrier of Zn2+, thereby promoting the transport of Zn2+ ions. MoS2−X @NCNTs cathode demonstrates an impressive discharge specific capacity of 220 mAh g−1 (0.1 A g−1) and a remarkable reversible capacity of 173 mAh g−1 (3 A g−1). Furthermore, the reduced adsorption energy of MoS2−X nanosheets leads to Zn2+ tending to preferentially insert S vacancies, resulting in a larger capacity than pure MoS2. This work realizes efficient storage of Zn2+ in 2D disulfides through carbon frameworks and S vacancies. In addition, flexible zinc batteries with MoS2−X @NCNTs cathodes have promising applications in wearable devices.

Microwave radiation method for rapid synthesis of Nb2O5@MoS2 as high-performance supercapacitor electrode materials

Microwave irradiation was used to create Nb2O5/MoS2 nanocomposites. The composite was self-assembled from flaky MoS2 and Nb2O5 nanotubes, according to structural and performance studies. Cyclic voltammetry, the timed potential method, and electrochemical impedance spectroscopy were employed to investigate the electrochemical properties. The specific capacitance of Nb2O5/MoS2 nanocomposites (628 F/g) was greater than that of pure Nb2O5 nanoparticles (183 F/g) and MoS2 at a current density of 1 A/g (125 F/g). Cyclic properties confirmed that the nanocomposites had higher cyclic stability, with a capacitance retention rate of 90.6 % after 5000 cycles. Dynamic analysis revealed that large conductive networks ensured Nb2O5/MoS2 electrochemical performance. The specific capacitance of the Nb2O5/MoS2 composite has increased, allowing efficient transport of ions and charges across the electrode surface with electrolytes. According to electrochemical studies, Nb2O5/MoS2 nanocomposites have the potential to be effective electrodes for high-performance supercapacitor applications.

Hydrothermal Synthesis of MoS2/SnS2 Photocatalysts with Heterogeneous Structures Enhances Photocatalytic Activity.

The use of solar photocatalysts to degrade organic pollutants is not only the most promising and efficient strategy to solve pollution problems today but also helps to alleviate the energy crisis. In this work, MoS2/SnS2 heterogeneous structure catalysts were prepared by a facile hydrothermal method, and the microstructures and morphologies of these catalysts were investigated using XRD, SEM, TEM, BET, XPS and EIS. Eventually, the optimal synthesis conditions of the catalysts were obtained as 180 °C for 14 h, with the molar ratio of molybdenum to tin atoms being 2:1 and the acidity and alkalinity of the solution adjusted by hydrochloric acid. TEM images of the composite catalysts synthesized under these conditions clearly show that the lamellar SnS2 grows on the surface of MoS2 at a smaller size; high-resolution TEM images show lattice stripe distances of 0.68 nm and 0.30 nm for the (002) plane of MoS2 and the (100) plane of SnS2, respectively. Thus, in terms of microstructure, it is confirmed that the MoS2 and SnS2 in the composite catalyst form a tight heterogeneous structure. The degradation efficiency of the best composite catalyst for methylene blue (MB) was 83.0%, which was 8.3 times higher than that of pure MoS2 and 16.6 times higher than that of pure SnS2. After four cycles, the degradation efficiency of the catalyst was 74.7%, indicating a relatively stable catalytic performance. The increase in activity could be attributed to the improved visible light absorption, the increase in active sites introduced at the exposed edges of MoS2 nanoparticles and the construction of heterojunctions opening up photogenerated carrier transfer pathways and effective charge separation and transfer. This unique heterostructure photocatalyst not only has excellent photocatalytic performance but also has good cycling stability, which provides a simple, convenient and low-cost method for the photocatalytic degradation of organic pollutants.

Compaction of Hydrophobic Molybdenum Disulfide Coatings for Promoting Tribological Behaviors on Engineering Steel

Ambient environment has a crucial effect on the lubrication performance of molybdenum disulfide (MoS2) coatings. In this work, we fabricated porous MoS2 coatings via a facile optimized aerosol-assisted chemical vapor deposition (AACVD) method. It is found that the obtained MoS2 coating demonstrates outstanding antifriction and antiwear lubrication performance with the coefficient of friction (COF) and wear rate as low as 0.035 and 3.4 × 10–7 mm3/Nm in lower humidity (15 ± 5)%, respectively, which is comparable to the lubrication ability of pure MoS2 in vacuum. In addition, the hydrophobic property of porous MoS2 coatings is suitable for infusing lubrication oil to achieve stable solid–liquid lubrication in higher humidity (85 ± 2)%. The composite lubrication system shows excellent tribological behavior in both dry and wet environments, which will alleviate the sensitivity of the MoS2 coating to the environment and ensure the service life of the engineering steel in complex industrial backgrounds.

Self-templated growth of heterogeneous hollow Cu2-xS@1T-MoS2 microcubes with superior electromagnetic wave absorption

With the proliferation of the use of wireless communication technologies, lightweight, easily fabricated EMW absorbers are in great demand for commercial and stealth applications. In this paper, well-defined Cu2O microcubes were successfully transformed into Cu9S5@MoS2 hollow microboxes by a facile hydrothermal process through a template-directed in situ vulcanization/complexation synergistic reaction. The MoS2 nanosheets loaded on the microboxes exhibited a high 1T phase ratio. Compared to pure MoS2 nanosheets, Cu9S5@MoS2 is advantageous in building conducting networks and interfacial polarization due to its good structure. The composite of Cu9S5@MoS2 with paraffin showed good EMW absorption performance at 40 wt%. By adjusting the MoS2 loading, the attenuation and impedance coefficients can be further optimized, with an optimized RLmin of −52.2 dB at 2.1 mm and an EAB of 4.7 GHz.

Ultrathin MoS2 nanosheet-wrapped Fe3O4 nanocrystals synergistically activate peroxymonosulfate for enhanced removal of organic pollutants

In peroxides-based advanced oxidation technologies (AOPs) using Fe-based catalysts, the low efficiency of Fe-ions cycling hinders their industrial applications. Recently, MoS2 has been validated to be a promising co-catalyst that can effectively promote the dynamic cycling of Fe-ions during the reaction. However, the activities of the reported MoS2-loaded Fe-based catalysts still decreased significantly after 3–5 cycling reactions, so it is necessary to develop a catalyst with high activity and stability. A series of MoS2 @Fe3O4-x (MF-x) catalysts were successfully constructed to trigger peroxymonosulfate (PMS) to eliminate the refractory organics. Ultrathin MoS2 nanosheets (∼ 5.7 nm) were uniformly and firmly coated on the surface of Fe3O4 nanoparticles via Fe–S bridging interaction. Pure MoS2 made little contribution to the climbazole (CBZ) degradation. Compared to the Fe3O4/PMS system, the adsorption and degradation efficiencies of the CBZ by MF-x/PMS system were improved by 7.5 and 4 times, respectively. The FeII/FeIII and MoIV/MoVI redox cycles on the MF-x surface could interact and work in synergy during the catalytic activation of PMS to degrade pollutants. MF-0.23 was an effective and stable catalyst for application over a wide pH range (2.0–9.8). Moreover, it efficiently dealt with other representative refractory contaminants with different pKa values, such as fluconazole (FZ), phenol, and rhodamine B (RhB). The primary active free radicals in MF-0.23/PMS system were detected to be O2•– and SO4•–. Specifically, the generated O2•– not only participated in the degradation of contaminants but also contributed to the MoIV regeneration. With outstanding catalytic activity, broad applicability, excellent reusability, and long-term stability, the MoS2 nanosheet-wrapped Fe3O4 nanocrystals should be an ideal heterogeneous catalyst for PMS-based AOPs.

Growth of 2D MoS2 and MoSe2 layers for photodetector application

We have grown a few layers MoS2 and MoSe2 on Si (100) substrates using a chemical vapor deposition (CVD) technique at different approaches and growth temperatures. Structural, surface morphology and electronic properties were investigated by Raman spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy (XPS). The MoS2 thin films were grown using three-zone CVD system by employing the MoO3 and sulfur powder precursors. We have obtained characteristics E12g and A1g Raman modes of MoS2 peaks and the separation between these two modes revealed the formation of a 2-monolayer of MoS2 on Si (100) substrate. The triangular morphology of MoS2 layer with a thickness of ∼1.4 nm i.e. nearly 2-monolayer was deduced by atomic force microscopy. Similarly, a few layers of MoSe2 were grown on Si (100) by selenization of Mo-coated Si (100) and 2H-MoSe2 characteristics Raman peaks were obtained. The XPS analysis revealed the formation of pure MoS2 and MoSe2 thin films on Si (100) substrates. The two-dimensional materials on Si (100) can be used for broadband photodetector applications.

Modulating MoS2 nanostructure by vanadium incorporation for high-efficiency hydrogen evolution reaction

In this work, we reported a facile approach to fabricate molybdenum sulfide (MoS2) electrocatalyst with the introduction of vanadium(V) for improved catalytic performance. The morphology of prepared samples can be characterizated by SEM observation. The XRD and XPS spectra further reveal that the proper amount of vanadium introduction can effectively prompt the increase of crystallinity and formation of edge-terminated structure in MoS2 nanostructure. The experimental results display that the morphology of MoS2 can be modulated by various amounts of V incorporation. The conductivity of prepared samples is increased by incorporating a certain amount of graphene. MoS2 nanostructure with 20% V incorporation shows excellent catalytic performance, and the corresponding mechanism is also discussed. The electrochemical performance of 20%V-MoS2 can be further improved by the introduction of appropriate graphene. Compared with pure MoS2 samples, 20%V-MoS2/Graphene7.5 shows a small resistance and excellent cycling stability in the acidic electrolyte, as well as the overpotential at 10 mA decreases from 213 mV to 168 mV.

Chitosan induced synthesis of few-layer MoS2/Fe-doped biochar and its dual applications in Cr(VI) removal

The removal of Cr(VI) from wastewater still faces many challenges. This study reports on chitosan-induced synthesis of few-layer MoS2/Fe-doped biochar (Mo-Fe0.5-CS) with dual applications in Cr(VI) removal. Using chitosan as a soft template, the MoS2 in the composite had only about 3 layers with an interlayer spacing greater than that of pure MoS2, while Fe was embedded in the carbon skeleton in the form of 6-coordination with O/N. The Mo-Fe0.5-CS composite showed high affinity for Cr(VI), with rapid adsorption reaching 100% removal within 15 min for a single solution of Cr(VI). It follows the Langmuir isotherm model with a maximum adsorption capacity of up to 180 mg/g. Furthermore, the Mo-Fe0.5-CS composite demonstrated catalytic activity for Fenton-like reactions, which allowed for the simultaneous removal of organic pollutants and Cr(VI). In a mixture solution of Cr(VI) and Acid Red 73 (AR73), the removal efficiencies using Mo-Fe0.5-CS and H2O2 in 30 min were 99.7% and 96.6%, respectively. The MoS2 acted as a cocatalyst to improve the reduction of Fe(III), and the catalysis of Cr(VI) also contributed to the removal of AR73 to a certain extent. Even at pH 10, the system was effective due to the 1O2 produced in the reaction and the acidic microenvironment constructed by unsaturated S atoms. These findings provide insights into the effective removal and utilization of Cr(VI) in wastewater treatment.

Interlayer texturing for improving the tribological property in vacuum of highly crystallized molybdenum disulfide film

The work reports on the morphologies and the tribological properties of MoS2 films deposited onto the as-deposited or textured TiN and WC interlayers. The closed-field unbalanced magnetron sputtered MoS2 film exhibited dense structure without obvious voids or columnar morphology. Meanwhile, plenty of MoS2 nanowires or nanorods were grown on the film surface. With the laser-textured TiN or WC interlayer introduced, both the textured TiN/MoS2 film and WC/MoS2 film exhibited a long lubricating life higher than 8.0 × 105 sliding cycles, much higher than that for the un-textured films or pure MoS2 film.

Hydrothermally Synthesized Ag@MoS2 Composite for Enhanced Photocatalytic Hydrogen Production

Photocatalytic hydrogen production is a green, cost-effective, simple, and pollution-free technology for the supply of clean energy, which plays an important role in alleviating the fossil fuel crisis caused by exponentially grown energy consumption. Therefore, designing highly visible-light-active novel photocatalyst materials for photocatalytic hydrogen production is a promising task. The production efficiency of photocatalyst can be improved by using noble metals, which are useful for the effective transfer of charge carriers. This study highlights the synergistic effect of the noble co-catalyst Ag on MoS2 during the investigation of photocatalytic hydrogen production. The hydrothermal method was used for the preparation of an Ag-MoS2 composite, and their structural and morphological characterizations were carried out using different physiochemical characterization techniques. The Ag-MoS2 composite shows an enhanced visible light absorption capacity and photocatalytic hydrogen production rate, as compared to that of pure MoS2, which proves that Ag nanoparticles (NPs) can act as efficient co-catalyst materials for photocatalytic hydrogen production with an improved rate of hydrogen production. Along with this, a possible working mechanism was proposed for visible-light-driven photocatalytic hydrogen production using the Ag@MoS2 composite.