Tungsten Disulfide Research Articles

(Invited) Synthesis and Application of 1D vdW Heterostructures Based on Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWCNTs) with diverse optical and electronic properties (metallic or semiconducting) depending on chiral indices (n, m) have been the key nanomaterials in advanced applications [1,2]. Even though a mixture of metallic and semiconducting SWCNT can be used for bulk and film-form applications such as batteries and solar cells [3], the controlled growth of (n, m) or the sorting of (n, m) is essential for electronics applications such as field effect transistors (FET) [4]. On the other hand, the controlled modulation of properties can also be possible either by employing the inner space of the SWCNTs to encapsulate various materials or by externally wrapping the SWCNT template with additional atomic layers [5]. Here, I mainly discuss the latter case as a one-dimensional (1D) van der Waals (vdW) heterostructure based on SWCNT [6]. We have demonstrated the atomically precise one-dimensional (1D) van der Waals (vdW) heterostructure -- SWCNTs, boron nitride nanotubes (BNNTs), and molybdenum disulfide (MoS2) sequentially wrapped in radial direction -- by chemical vapor deposition in 2020 [6]. One of the obvious extensions of this work is the use of BNNT-SWCNT [7], which have superior semiconductor properties such as field effect transistors [8,9]. We have developed various characterization techniques for BNNT-SWCNT for the growth optimization and quality control of BNNT in various kinds of SWCNT [10-12]. Yet another extension is the various kinds of transition metal dichalcogenides (TMD) nanotubes. We have optimized CVD conditions for various metal dichalcogenides such as tungsten disulfide (WS2), niobium disulfide (NbS2), and molybdenum diselenide (MoSe2) so far in addition to the original MoS2. Here, we further broaden the concept of 1D vdW heterostructure by combining 2 transition metal species. By setting WS2 growth right after the MoS2 growth, we can observe the axial junction of the outermost tube, MoS2 - WS2. The junction is atomically smooth within a few nanometers. On the other hand, by setting the 2 transition metal species at the same CVD time, we can observe {WxMo(1-x)}S2 alloy nanotube. Both axial junction and alloy nanotubes are preferentially monolayers.Part of this work was supported by JSPS KAKENHI Grant Numbers JP23H00174, JP23H05443 and by JST, CREST Grant Number JPMJCR20B5, Japan.

A WS2/CNF Nanocomposite for Electrochemical Sensing Applications

Successful environmental monitoring is crucial to safeguarding humans and the natural world. The presence of antibiotics in aquatic environments has become a pressing global concern, posing potential risks to both ecosystems and public health. Extensive use of antibiotics in medical treatment and agriculture has led to their release into water bodies through various pathways, contributing to water contamination. Detecting and monitoring antibiotic residues in water is crucial to understanding the extent of contamination and mitigating its adverse effects. Furthermore, the escalating concern over pharmaceutical contaminants in the environment has prompted significant research efforts towards the development of advanced sensing technologies.Recently, 2D materials have emerged as promising candidates for environmental sensing, due to their unique properties and potential applications. Transition-metal dichalcogenides or TMDs, are two-dimensional (2D) materials comprising of MX2, with M a transition metal atom e.g. Mo, W etc. and X, a chalcogen atom S, Se or Te1. The M atoms are sandwiched between two layers of X atoms with robust in-plane covalent bonds, and weak van der Waals forces between the planes. Among the TMDs, tungsten disulfide (WS2) exhibits outstanding properties, such as high electronic conductivity, large capacitance, high surface area, and chemical stability. This study explores the promising characteristics of WS2 and its synergistic potential of combining it with carbon materials to develop hybrid structures2. Carbon nanofibers (CNFs) exhibit exceptional properties that make them promising candidates for sensor applications. With their large surface area, and excellent electrical conductivity, CNFs offer a unique platform for the development of sensitive and selective sensors. In addition, CNFs versatility allows for functionalization, enhancing their chemical properties and facilitating tailored interactions with target analytes. Furthermore, owing to these notable properties, carbon nanofibers complement WS2 in the development of innovative sensor structures. Here, WS2 was combined with functionalized carbon nanofibers, to create a composite structure that was employed to detect ornidazole (ORZ), an antibiotic drug.Ornidazole, belonging to the nitroimidazole class of antibiotics, is commonly employed in the treatment of various genitourinary tract and protozoal infections3. Beyond the immediate therapeutic benefits, antibiotics such as ornidazole can persist in the environment, posing long-term risks. Moreover, excess ORZ in the environment has potential mutagenic & carcinogenic effects, and can lead to the development of antibiotic resistant pathogens. In this study, the WS2 /CNF nanocomposite was synthesized using hydrothermal synthesis and subsequently dispersed in ethanol and water, and then drop casted on a glassy carbon electrode. Prior to synthesis, the CNFs were functionalized using a low cost, environmental friendly method, thus enhancing their chemical properties. Herein, the resulting WS2/CNF composite demonstrates its efficacy in detecting ornidazole (ORZ), and shows excellent potential for the development of electrochemical sensors. Overall, the work here aims to underscore the continuous development of electrochemical sensor technology, emphasizing its pivotal role in addressing the growing challenges associated with drug contamination in the environment.(1) Manzeli, S.; Ovchinnikov, D.; Pasquier, D.; Yazyev, O. V.; Kis, A. 2D Transition Metal Dichalcogenides. Nature Reviews Materials. 2017. https://doi.org/10.1038/natrevmats.2017.33.(2) Santos, B. G.; Gonçalves, J. M.; Rocha, D. P.; Higino, G. S.; Yadav, T. P.; Pedrotti, J. J.; Ajayan, P. M.; Angnes, L. Electrochemical Sensor for Isoniazid Detection by Using a WS2/CNTs Nanocomposite. Sensors and Actuators Reports 2022, 4. https://doi.org/10.1016/j.snr.2021.100073.(3) Koventhan, C.; Vinothkumar, V.; Chen, S. M. Development of an Electrochemical Sensor Based on a Cobalt Oxide/Tin Oxide Composite for Determination of Antibiotic Drug Ornidazole. New Journal of Chemistry 2021, 45 (28). https://doi.org/10.1039/d1nj01345a

Tuning Van Der Waals Heterostructure of WS2/SrTiO3 Via in Situ Transmission Electron Microscopy

Monolayer two-dimensional (2D) materials have been widely researched and discussed in recent years, while multi-layers have received comparatively less attention. Nowadays, combining different materials to create heterostructures has become mainstream. In semiconductor industry, heterostructure can form devices such as lasers, light-emitting diodes, fast transistors and so on. Heterostructures can create well electronic properties by combining two different materials together. Therefore, heterostructures become a great tool to manipulate the electronic structures. In traditional heterostructures, the interfaces between two different materials are formed by covalent bonds, hence it requires similar lattice constants and structures. On the other hand, novel van der Waal heterostructures (vdW-heterostructure), formed by 2D materials, do not require the same strict similarity as traditional ones. VdW-heterostructures, which create 3D structures through van der Waals forces, provide a new perspective. In this study, we created a vdW-heterostructures by stacking tungsten disulfide (WS2) with single-crystal strontium titanate, SrTiO3 (STO), shown in Figure 1a,b. The crystalline atomic-layer WS2 and STO were synthesized by chemical vapor deposition (CVD) and pulsed laser deposition (PLD), respectively. They are analyzed by high-resolution transmission electron microscope (HRTEM) shown in Figure 1c-h. Once the vdW-heterostructures are formed, we conducted in situ heating by TEM. Through the advanced in situ technique, we observed the change of the twisted stacking angle by heating the vdW-heterostructure. Ultimately, the lattices will shift and rotate, minimizing the free energy, so that the vdW-heterostructure will be aligned and formed epitaxially. In addition, we utilized atomic resolution scanning transmission electron microscope (STEM) to identify the stacking images and the moiré pattern of the vdW-heterostructure. During the rotation, we can observed different moiré patterns by various twisted stacking angles. These different moiré patterns can produce different electrical properties, which can be applied to advanced semiconductor devices. Keywords: high-resolution TEM/STEM, in situ heating, 2D materials, van der Waal heterostructures, moiré pattern Figure 1. The vdW-heterostructure of STO/WS2. a) The diagram showing that the formation process of WS2/STO vdW-heterostructures which have different twisted stacking angles. b) The low-magnification SEM image showing that the single crystal STO thin film is transferred onto the TEM heating chips. The circles in the middle are the observation windows for transmission electrons. c-e) HRTEM images. f-g) Diffraction patterns of HRTEM. c,f) Single crystal STO thin film with d-spacing (1−10) = 0.284 nm. d,g) Monolayer single crystal WS2 with d-spacing (−110) = 0.274 nm. e,h) WS2(red)/STO(yellow) vdW-heterostructure with stacking angle 3.6°. Figure 1

Meso-level surface modification of Hastelloy C276 by WS2 powder mixed electrical discharge alloying process through micro-EDM setup

The present research provides a rigid, wear-resistant lubricating localized layer on Hastelloy C276 (HC 276) surface at meso level by tungsten disulphide (WS2) powder suspended electrical discharge alloying (EDA) process through micro-electrical discharge machining (μ-EDM) setup. The performance characteristics of the coated surface were evaluated in terms of material deposition rate (MDR), surface morphology, surface roughness (Ra, Rz and Rq), recast layer thickness (RLT), compositional analysis, micro-hardness & indentation depth, wear test and water contact angle analysis. Maximum MDR has been achieved at 15 g/L WS2 concentration and 80 V of gap voltage whereas The RLT varies from 6.87 μm to 18.91 μm and is enhanced with the increase in WS2 concentration. The critical surface characterization confirms higher WS2 concentration reduces the crater dimensions and the presence of micro-cracks and micro-voids on the coated surface. The surface roughness has been increased with the gap voltage and capacitance, whereas higher WS2 concentration provides lower surface roughness. X-Ray diffraction analysis (XRD) confirms the presence of hard and wear resistance phases like WC, WO3, ZnO, and MoO2 on the coated surface. Energy-Dispersive X-Ray Spectroscopy (EDS) analysis along with elemental mapping justifies tool, dielectric materials, and powder particles migration on the coated surface. The micro-hardness of the coated surface (402 HV to 1166 HV) is enhanced by 3–4 times compared to the base material (299 HV) whereas the indentation depth has been reduced with the rise in WS2 concentration and lies within the RLT of the coated surface. The wear rate of the WS2 coated surface is drastically reduced compared to the base material with a lower value of coefficient of friction (COF). The coated surface became hydrophobic in nature with a contact angle of 109.6° compared to the hydrophilic base HC 276.

Spray coating of 2D materials in the production of antifouling membranes for membrane distillation

Membrane surface coatings with 2D materials have been shown to exhibit antifouling properties for water-treatment applications; however, synthesis methods currently based on vacuum filtration are not easily scalable. This study describes a scalable method for coating membranes with a range of 2D materials including graphene oxide (GO), hexagonal boron nitride (hBN), molybdenum disulphide (MoS2) and tungsten disulphide (WS2). Isopropyl alcohol solutions containing each class of the 2D flakes were spray-coated onto commercial polyvinylidene fluoride (PVDF) using a pyrolyser. The nanomaterials were secured with polydopamine (PDA) as a crosslinker in a method that could easily be integrated into a scalable roll-to-roll process. Changes in morphology, surface roughness, hydrophobicity, mechanical durability and chemical composition were evaluated using scanning electron microscopy, atomic force microscopy, contact angle, tensile strength measurements and Fourier-transform infrared spectroscopy. The 2D nanomaterials-coated membranes were tested in membrane distillation (MD) experiments over 72 h and compared to pristine PVDF and PDA/PVDF membranes. Salt rejection and MD performance stability were evaluated using feedwaters with high concentrations of humic acid (150 ppm) and paraffin oil (200 ppm) simulating simple organic wastewater from oil and gas extraction. The flux decline ratio was measured in terms of percentage permeate loss per hour (%/h), to allow for future comparisons with studies with different experimental times. The pristine PVDF membrane failed after 10 h by pore-wetting due to fouling while the PDA/PVDF membrane had the largest flux decline ratio (0.3 %/h). The membranes coated with GO and hBN had flux decline ratios orders of magnitude lower (0.0021 ± 0.005 and 0.028 ± 0.01 %/h, respectively). All membranes had a high salt rejection (>99.9 %). The GO-coated membrane was the only membrane type that was able to treat both surfactant-containing and foulant-containing feedwaters. The improved performance is attributed to the decrease in both surface roughness and hydrophobicity, which reduces the adsorption of foulants onto the membrane surface. This work shows a facile, scalable method to overcome fouling limitations in MD.

Impact of wrinkle orientation on the nanotribological properties of chemical vapor deposited TMD monolayers using AFM

Structural defects in two-dimensional (2D) materials are ubiquitous and can influence their physical and chemical properties. The presence of structural defects in single atom thick 2D materials such as graphene is detrimental to the tribological properties and is well documented; however, their effects on various other 2D materials such as transition metal dichalcogenides (TMDs) remain largely unexplored. Here, we report the role of wrinkles’ orientation on the nanoscale tribological behavior of the chemical vapor deposited (CVD) tungsten disulfide (WS2) monolayers. Our molecular dynamics (MD) simulations reveal the underlying atomistic mechanism which indicates the presence of wrinkles exhibiting various orientations, and maximum damage occurred when the tip moved at a 45-degree angle to the wrinkle. This underscores the significant influence of wrinkles’ orientation on the wear behavior of WS2 monolayers.

Investigating novel perovskites of lead-free flexible solar cell CH3NH3BiI3 and their photovoltaic performance with efficiency over 26%

Perovskite solar cells are increasing attention due to their unique characteristics in the field of photovoltaic technology. Lead-based perovskite solar cells are particularly notable for their high efficiency. However, their commercial production is limited because of the use of lead-based absorbers. As a result, research has shifted towards exploring lead-free alternatives in the realm of perovskite materials. This study utilizes SCAPS-1D simulation software to optimize the performance of a lead-free flexible solar cell. Lead (Pb), a group 14 element, is proposed to be replaced by bismuth (Bi), a group 15 element. We investigate how the selection of configurations for the Electron Transport Layer (ETL), Hole Transport Layer (HTL), and absorber layer impacts solar cell performance. This study represents a comprehensive examination of this material. The device optimization involves using a fluorine-doped tin oxide (FTO) substrate, cadmium sulfide (CdS), tungsten disulfide (WS2), titanium dioxide (TiO2), and fullerene (C60) as ETL components, methyl ammonium bismuth iodide (CH3NH3BiI3) as the absorber, molybdenum disulfide (MoS2) as the HTL, and platinum (Pt) as the electrode. In addition to optimizing ETL and HTL configurations, this study explores the effects of various factors such as absorber, ETL, and HTL thickness, shunt and series resistance, temperature variations, Mott-Schottky behavior, capacitance, recombination, generation rates, J-V characteristics, and quantum energy. The results show that the solar cell configuration using FTO/CdS/CH3NH3BiI3/MoS2/Pt achieves an efficiency of 26.60 %, a current density (JSC) of 32.02 mA/cm2, an open circuit voltage (VOC) of 0.974 V, and a fill factor (FF) of 85.24 %. This represents a significant improvement compared to previous research. This detailed simulation analysis enables researchers to develop cost-effective and highly efficient perovskite solar cells (PSCs), driving advancements in solar technology.

Giant nonlinear optical wave mixing in a van der Waals correlated insulator.

Optical nonlinearities are one of the most fascinating properties of two-dimensional (2D) materials. While tremendous efforts have been made to find and optimize the second-order optical nonlinearity in enormous 2D materials, opportunities to explore higher-order ones are elusive because of the much lower efficiency. Here, we report the giant high odd-order optical nonlinearities in centrosymmetric correlated van der Waals insulator manganese phosphorus triselenide. When illuminated by two near-infrared femtosecond lasers, the sample generates a series of profound four- and six-wave mixing outputs. The near-infrared third-order nonlinear susceptibility reaches near the highest record values of 2D materials. Comparative measurements to other prototypical nonlinear optical materials [lithium niobate, gallium(II) selenide, and tungsten disulfide] reveal its extraordinary wave mixing efficiency. The wave mixing processes are further used for nonlinear optical waveguide with multicolor emission. Our work highlights the promising prospect for future research of the nonlinear light-matter interactions in the correlated 2D system and for potential nonlinear photonic applications.

Wafer scale WS2 based ultrafast photosensing and memory computing devices for neuromorphic computing

Integration of optical sensors with memristors can establish the bridge between photosensing and memory devices for Internet of Things (IoT) based applications. This paper presents the realization of integrated sensing and computing memory (ISCM) devices using tungsten disulfide (WS2) and their application for neuromorphic computing. The ISCM device fabrication process is scalable as microfabrication steps followed on 2″ wafer, ISCM device testing and image classification for neuromorphic computing. The photosensing/memory tests were conducted using electrical and optical stimulations (broadband spectrum). The fabricated photosensing device offers a higher responsivity (8 A W−1), higher detectivity (2.85 × 1011 Jones) and fast response speed (80.2/78.3 μs) at 950 nm. The memory device has shown a set/reset time of 51.6/73.5 μs respectively. Further, the repeatability, stability and reproducibility tests were conducted by stimulating the device with different modulating frequencies. The frequency modulation tests confirm that the ISCM devices are stable and perfect candidate for real-time IoT applications. Moreover, the device’s potentiation and depression results were used for image classification with the accuracy of 98.27%. These demonstrated device’s test results provide possibilities to fabricate the smart sensors with integrated functionalities.

Exploring synthesis and annealing influence on WS2 (tungsten disulfide): Structural, morphological, optical, and magnetic profiles

The resurgence of interest in Transition Metal Dichalcogenides (TMDCs) stems from their remarkable magnetic and optical properties, reminiscent of graphene. TMDCs like MoS2, MoSe2, WS2, and WSe2 exhibit substantial bandgaps that shift from indirect to direct in single layers. This characteristic enables diverse applications such as solar cells, transistors, photodetectors, and electroluminescent devices, without the direct use of graphene. In this study, polycrystalline WS2 powder was synthesized via the solid-state reaction method. We systematically investigated the structural, morphological, optical, and magnetic properties concerning the synthesized WS2 and its variants annealed at different temperatures. Through X-ray powder diffraction (XRD) analysis, we confirmed the hexagonal structure of the as-synthesized compound, with a space group of P 63/mmc. Interestingly, no structural transitions were observed in the annealed samples. Morphological examination revealed a plate-like structure across all samples. The determination of the optical bandgap was facilitated by UV-DRS absorption spectrum analysis. Our findings showcased the ferromagnetic behavior of the synthesized WS2, corroborated by magnetic measurements and electron paramagnetic resonance (EPR) analysis. These insights contribute to a deeper understanding of TMDCs and pave the way for their tailored utilization in advanced technological applications.

Novel application of carbon nanotube electrodes for electrochemical detection of amino acids in athlete’s biological samples

Understanding different physiological processes and spotting any health problems, especially in athletes, depend on tracking the quantities of amino acids in biological samples. This study looked at the creation of a unique electrochemical sensor for the sensitive and targeted identification of the necessary amino acid methionine in biological materials. Based on a modified glassy carbon electrode (GCE) surface, the sensor incorporated a tungsten disulfide (WS2) and carbon nanotube (CNT) nanocomposite. The improved electrical conductivity and catalytic activity of this material combination towards methionine oxidation led to its selection. The sensor that was created showed remarkable selectivity for methionine over other amino acids, along with a wide linear range of 5–1475 μM and a low detection limit of 10 nM. A relative standard deviation of 3.62 % was obtained across ten consecutive measurements, confirming the sensor's repeatability. The practical use of the CNTs-WS2/GCE sensor was verified by the detection of MTN in human blood serum, urine, and food samples. The recovery values ranged from 93.00 % to 99.40 %, and the relative standard deviation was less than 4.71 %. Based on these findings, we believe that our new CNTs-WS2/GCE sensor holds great potential for quick and precise methionine identification in biological samples from athletes.

A strategy of forming sandwich electrodes based on graphene and two-dimensional transition metal dichalcogenides as supercapacitors to avoid gas evolution

Two-dimensional (2D) materials such as transition metal dichalcogenides (TMDC) are well-recognized as excellent electrode materials for energy storage applications due to the ion intercalation characteristic. However, gas evolution is central to the problems that limit the potential window of these materials in the energy storage context. This is because the TMDC can behave as an electrocatalyst, especially in an acid environment. Herein, a novel design of electrode materials for avoiding gas evolution in supercapacitor devices was formed using the sandwich configuration between graphene (GP) and TMDC. A family of transition metal dichalcogenide (TMDC) materials e.g., molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2), tungsten disulfide (WS2), and tungsten diselenide (WSe2) including GP was constructed as a layer-by-layer electrode materials, like a “sandwich”. In this work, we provide a straightforward method for creating GP/TMDCs/GP free-standing electrodes that have the necessary properties, such as large surface area and high conductivity for electrolyte diffusion. The GP sandwich on both sides of the electrode can diminish the gas evolution of TMDCs in acidic conditions. This makes the sandwiched electrodes perform a wider electrochemical window up to 1.0 V, in 1.0 M H2SO4. Note that the gas evolution e.g. hydrogen typically occurs at about −0.35 V (onset). Compared with conventional GP/activated carbon, the specific capacitances of “sandwich” GP/MoS2/GP, GP/MoSe2/GP, GP/WS2/GP, and GP/WSe2/GP devices are improved by 7.4, 6.2, 14.8, and 17.3 %, respectively. The findings also indicate that the developed sandwich electrode may be a suitable choice for the creation of future large energy storage systems with a high intercalation capacitance in layered materials.

Excitonic van der Waals Metasurfaces for Resonant Wavefront Shaping at Deep Subwavelength Thickness Scale.

Dielectric phase gradient metasurfaces have emerged as promising candidates to shrink bulky optical elements to subwavelength thickness scale based on dielectric meta-atoms. These meta-atoms strongly interact with light, thus offering excellent phase manipulation of incident light. However, to fulfill 2π phase control using meta-atoms, the metasurface thickness, to date, is limited to the order of 102 nm. Here, we present the thickness scaling down of phase gradient metasurfaces to <λ/20 by using excitonic van der Waals metasurfaces. High-refractive-index enabled by exciton resonances and symmetry-breaking nanostructures in the patterned layered tungsten disulfide (WS2) corporately enable quasibound states in the continuum in WS2 metasurfaces, which consequently yield complete phase regulation of 2π with the thickness down to 35 nm. To illustrate the concept, we have experimentally demonstrated beam steering, focusing, and holographic display using WS2 metasurfaces. We envision our results unveiling new venues for ultimate thin phase gradient metasurfaces.

Designing and simulating of new highly efficient ultra-thin CIGS solar cell device structure: Plan to minimize cost per watt price

This research paper examines the execution of ultra-thin solar cells made from chalcopyrite copper indium gallium diselenide (CIGS). The study presents a new CIGS heterojunction solar cell structure, which includes a Cd-free tungsten disulfide (WS2) buffer layer and poly (3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT: PSS) passivation layer. The performance of the solar cell is raised by a back surface field (BSF). A highly recombining rear surface is kept away from minority carriers by a field created by further strong doping at the back. The structure is Ni/PEDOT:PSS/CIGS/WS2/ZnO/Al and has been estimated numerically using the Opto-electrical stimulation of semiconductor layers simulator SCAPS-1D. A high efficiency with a Back surface passivated layer of 25.70 % with Voc of 0.81 V, Jsc of 39.33 mA/cm2, and FF of 79.89 % and without passivated layer efficiency of 17.58 % with Voc of 0.73 V, Jsc of 32.18 mA/cm2, and FF of 74.78 % is found for the intended CIGS-based solar cell with WS2 buffer. The interface between CIGS and WS2 forms a band structure that resembles spikes. This structure is crucial in enhancing the outputs by reducing carrier recombination. The optimal thicknesses for the buffer and CIGS absorber layers are 0.02 μm and 0.2 μm, respectively. These findings help reduce the cost per watt of the solar cell. Fabrication at a mass production scale, minimizing the thickness will have a significant impact on reducing cost.

THE MECHANICALLY ACTIVATED COMPOSITES BASED ON TUNGSTEN DISULFIDE: SYNTHESIS AND PROPERTIES

In this work, the physicochemical properties of mechano-activated composites (hereinafter referred to as the mechanocomposites) obtained by mechanical activation of commercial tungsten disulfide powder in a planetary mill were studied. Mechanical activation was carried out for 2, 4 and 8 h, but this work presents the results for the last two experiments. The acceleration of the grinding media was controlled through frequency adjustment; a frequency value of 15.5 Hz, according to calculations, corresponds to an acceleration of the grinding media of 50 m/s2 or 5G. The material of the balls from which the grinding balls are made is stainless steel. Due to the relatively low acceleration values, the problem of contamination of the sample with stainless steel components does not occur as a result of surface erosion that occurs when the balls collide with each other and with the walls of the grinding bowl. Mechanical activation was carried out in an inert argon environment, since these were preliminary studies and therefore there was a need to minimize the environmental parameters taken into account. However, the oxidation process will occur during the process of discharging the sample from the grinding bowl of the planetary mill. The resulting mechanocomposites are precursors for the synthesis of monocomponent catalysts for the processing of heavy oil residue. For this purpose, it is necessary to obtain mechanocomposites containing tungsten trioxide and tungsten disulfide. The results of an experimental study of the influence, mainly, of the duration of mechanical activation on the production of tungsten mechanocomposites are presented. The resulting compounds were characterized by X-ray phase analysis (XRD), IR spectroscopy, scanning electron microscopy (SEM), thermogravimetry (TGA) and simultaneous thermal analysis (STA). For citation: Akimov Al.S., Zhirov N.A., Sudarev E.A., Akimov A.S. The mechanically activated composites based on tungsten disulfide: synthesis and properties. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 36-43. DOI: 10.6060/ivkkt.20246708.2t.

Investigating improvement in the performance of WS2 absorber layer based thin film solar cell with a hole transport layer of Indium Telluride

In this work, Tungsten Disulfide (WS2) is used as absorber layer with Indium Telluride (In2Te3) as hole transport layer and a comparison is made between the devices without and with hole transport layer. Analysis is carried out by varying thickness of WS2, Acceptor concentration of WS2, Interface defects, Temperature, Surface recombination velocities, Series and Shunt Resistances. It is observed that by introducing hole transport layer of Indium Telluride, carrier recombination losses can be restricted and the power conversion efficiency of proposed solar cell can be raised significantly. The efficiency of Tungsten Disulfide absorber layer based solar cell is 23.13% when hole transport layer is not inserted, whereas by incorporating a hole transport layer of Indium Telluride, it is increased to 25.37%. SCAPS-1D is used for simulation of the model.

Cost-efficient and ultrasensitive sensor for electrochemical detection and cytotoxicity assessment of tetracyclines

The uncontrolled overuse of tetracyclines (TCs) has contributed to a significant rise in the levels of not only antibiotic residues in the environmental but also drug- and multidrug-resistant bacteria, necessitating a convenient, sensitive, and rapid assay for the quantitative determination and health risk assessment of TCs. This study presents the development of a nanocomposite sensor which integrates hydroxylated multiwalled carbon nanotubes (MWCNTs-OH), tungsten disulfide quantum dots (WS2QDs), and prussian blue (PB). This sensor was capable of measuring the concentrations of tetracycline (TC), oxytetracycline (OTC), doxycycline (DC), and tigecycline (TEC) at levels ranging from 0.10 to 125.00 μM, with detection limits of 0.010, 0.015, 0.020, and 0.060 μM, respectively (S/N = 3). The excellent electrochemical performance enabled the sensor to measure TC concentrations in real water samples. Importantly, the sensor was also used to evaluate the cytotoxicity of TCs on human hepatocarcinoma (HepG2) cells. The 48 h half-inhibitory concentrations (IC50) for TC, OTC, DC, and TEC were 344.91 μM, 365.14 μM, 349.59 μM, and 604.66 μM, respectively, indicating that TC was the most cytotoxic. The sensing platform described herein not only facilitates the quantitative determination of TCs but also allows for the assessment of their cytotoxicity in the water environment, which greatly simplifies the comprehensive evaluation process and reduces the cost, thus holding great promise for TCs testing.

Toward Scalable Electrochemical Exfoliation of Molybdenum Disulfide Powder through an Accessible Electrode Design.

Cathodic electrochemical intercalation/exfoliation of transition metal dichalcogenides (TMDs) with bulky tetraalkylammonium-based cations is gaining popularity as it avoids the semiconducting (2H) to metallic (1T) phase transformation in TMDs like molybdenum disulfide (MoS2) and, generally, produces sheets with a larger aspect ratio - important for achieving conformal sheet-to-sheet contact in optoelectronic devices. Large single crystals are typically used as the precursor, but these are expensive, often inaccessible, and result in limited quantities of material. In this paper, a 3D-printable electrochemical cell capable of intercalating gram-scale quantities of commercially available TMD powders is presented. By incorporating a reference electrode in the cell and physically restraining the powder with a spring-loaded mechanism, the system can probe the intercalation electrochemistry, for example, determining the onset of intercalation to be near -2.5V versus the ferrocene redox couple. While the extent of intercalation depends on precursor quantity and reaction time, a high yield of exfoliated product can be obtained exhibiting average aspect ratios as high as 49 ± 44 similar to values obtained by crystal intercalation. The intercalation and exfoliation of a wide variety of pelletized commercial powders including molybdenum diselenide (MoSe2), tungsten diselenide (WSe2), tungsten disulfide (WS2), and graphitic carbon nitride (gCN) are also demonstrated.

Recent Excellent Optoelectronic Applications Based on Two-Dimensional WS2 Nanomaterials: A Review.

Tungsten disulfide (WS2) is a promising material with excellent electrical, magnetic, optical, and mechanical properties. It is regarded as a key candidate for the development of optoelectronic devices due to its high carrier mobility, high absorption coefficient, large exciton binding energy, polarized light emission, high surface-to-volume ratio, and tunable band gap. These properties contribute to its excellent photoluminescence and high anisotropy. These characteristics render WS2 an advantageous material for applications in light-emitting devices, memristors, and numerous other devices. This article primarily reviews the most recent advancements in the field of optoelectronic devices based on two-dimensional (2D) nano-WS2. A variety of advanced devices have been considered, including light-emitting diodes (LEDs), sensors, field-effect transistors (FETs), photodetectors, field emission devices, and non-volatile memory. This review provides a guide for improving the application of 2D WS2 through improved methods, such as introducing defects and doping processes. Moreover, it is of great significance for the development of transition-metal oxides in optoelectronic applications.

Development and characterization of ZIF-8/WS2 composites for NH3 detection at room temperature

This study successfully synthesized zeolitic imidazolate frameworks-8 (ZIF-8) particles and tungsten disulfide (WS2) nanosheets, forming ZIF-8/WS2 composites via a layer-by-layer filtration adsorption method. The morphological and structural characterization results revealed that ZIF-8 particles and WS2 nanosheets effectively combine under filtration to form a hierarchical film structure. Room temperature ammonia (NH3) detection results indicated that the ZIF-8/WS2 composites-based gas sensor, due to the high specific surface area (1458 m2/g) and strong gas adsorption capability of ZIF-8, exhibits response intensity to NH3 that is 4.98 times higher than that of pure WS2 nanosheets. Additionally, it demonstrated stable response and recovery curves with short response/recovery times (113.5 ± 3.9 s/115.0 ± 1.9 s). This work provides valuable insights and inspiration for the construction of composite materials involving 2D TMDs and the enhancement of their room-temperature gas sensing performance.