Tungsten Disulfide Research Articles

Numerical investigation into impact of halide perovskite material on the optical performance of prism-loaded hybrid surface plasmon resonance biosensor: A strategy to increase sensitivity

The technology of surface plasmon resonance (SPR) is widely recognized and valued for its ability to rapidly and sensitively investigate biomolecular interactivities in real-time. Herein, we numerically investigate the collective influence of metal/ transition metal dichalcogenide (TMDC)/halide perovskite (HP)/2D carbon (C) and phosphorus (P) allotropes on the functionality of an SPR biosensor deploying Kretschmann configuration. The incident light wavelength is held constant at 633 nm, and radiative properties of the hybrid structure are determined using the attenuated total reflection and transfer matrix techniques. Crucial performance metrics such as quality factor (QF), figure of merit (FoM), sensitivity, and detection accuracy are calculated. The comparison is conducted and evaluated against the current literature using performance outcomes in terms of several prisms such as BK7, BAK1, BAF10, SF5, SF10, SF11, 2S2G, CaF2, and CsF, several TMDCs such as WS2, MoS2, WSe2, MoSe2, and PtSe2, several HPs such as CsPbI3, KSnI3, CsSnI3, and FASnI3, and 2D C/P allotropes such as Graphene, MXene, Black phosphorene (BP), and Blue phosphorene (BlueP) in order to search optimum parameters, and then we implement the best one in each layer of this biosensor design. It is noticed that the SPR heterostructure based on BAK1 prism, plasmonic metal Ag, tungsten disulfide (WS2) TMDC, formamidinium tin iodide (FASnI3) HP and 2D BP exhibits outstanding performance with regard to sensor performance characteristics. The observed FoM and sensitivity are 48.2/RIU and 402°/RIU, respectively. The investigation of the electric field distribution within this biosensor along the normal to the interface is also conducted using the finite difference time domain (FDTD) approach to demonstrate the unique contribution of FASnI3. The findings presented in this study are anticipated to play a key role in the improvement of plasmonic resonance-based biosensing domains like DNA hybridization or formalin detection by employing halide perovskite as an additional layer in SPR biosensors.

NIR-triggered letrozole delivery system based on tungsten disulfide nanosheet-coated thermo-responsive polymer: optimization by response surface methodology

NIR-triggered letrozole delivery system based on tungsten disulfide nanosheet-coated thermo-responsive polymer: optimization by response surface methodology

Layer-Dependent Sensing Performance of WS2-Based Gas Sensors.

Two-dimensional (2D) materials, such as tungsten disulfide (WS2), have attracted considerable attention for their potential in gas sensing applications, primarily due to their distinctive electrical properties and layer-dependent characteristics. This research explores the impact of the number of WS2 layers on the ability to detect gases by examining the layer-dependent sensing performance of WS2-based gas sensors. We fabricated gas sensors based on WS2 in both monolayer and multilayer configurations and methodically evaluated their response to various gases, including NO2, CO, NH3, and CH4 at room temperature and 50 degrees Celsius. In contrast to the monolayer counterpart, the multilayer WS2 sensor exhibits enhanced gas sensing performance at higher temperatures. Furthermore, a comprehensive gas monitoring system was constructed employing these WS2-based sensors, integrated with additional electronic components. To facilitate user access to data and receive alerts, sensor data were transmitted to a cloud-based platform for processing and storage. This investigation not only advances our understanding of 2D WS2-based gas sensors but also underscores the importance of layer engineering in tailoring their sensing capabilities for diverse applications. Additionally, the development of a gas monitoring system employing 2D WS2 within this study holds significant promise for future implementation in intelligent, efficient, and cost-effective sensor technologies.

Design and optimization of WS2 based high performance double absorber solar cell

Ultra-thin flexible photovoltaic materials for solar cells, like transition metal di-chalcogenides (TMDCs), hold significant promise due to their advantageous properties in photon absorption and electronic transport, being composed of atomically thin 2D layered semiconductor materials. An essential 2D-layered substance, tungsten Disulfide (WS2), classified as a TMDC, has garnered substantial attention due to its notable chemical and physical characteristics. This work presents a novel method for getting good photovoltaic results using WS2 solar cells. The suggested configuration ‘Al/FTO/SnS2/WS2/CuO/Ni’ comprises two absorber layers, which involves incorporating CuO as a supplementary absorber layer and SnS2 as the buffer layer. Several metals with varying work functions were investigated one at a time, therefore, Al and Ni were chosen for the front as well as back contact in order to produce a low resistance metal-semiconductor (M-S) interface. Additionally, aluminum (Al) and nickel (Ni), are commonly used due to their well-understood properties such as conductivity and thermal stability. Subsequently, an analysis was conducted to determine the effects of important influencing factors, such as operating temperature, layer thickness, defects density, and doping density of the absorber and buffer layers. The power conversion efficiency (PCE) was achieved approximately 30%, accompanied by an open circuit voltage (VOC) of 1.02 V, a short circuit current (JSC) of 34.35 mA cm−2, and a fill factor (FF) of 87.27%. This improvement was achieved by utilizing an Al/FTO/SnS2/WS2/CuO/Ni heterostructure. In comparison, the reference cell without CuO (single absorber) had a PCE of 21.74%, VOC of 0.88 V, JSC of 28.6 mA cm−2, and FF of 86.23%. The results obtained from an extensive numerical analysis and demonstrate the immense potential of the SnS2/WS2/CuO heterostructure, indicating a promising direction for the manufacturing of photovoltaic and photonic devices based on WS2-TMDCs. This study provides a systematic roadmap for the fabrication process as well as realization of low-cost high efficiency solar cell.

Spectroscopy of monolayer and multilayer tungsten disulfide under high pressure

Recently exfoliated monolayer and multilayered transition metal dichalcogenides have gathered significant interest based on their tunable bandgap and extremely high carrier mobility. We have investigated the Raman and photoluminescence spectra of monolayer and multilayer WS2 as a function of pressure. The Raman-inactive mode B1u, which is activated by structural disorder, was revealed at 6.7 GPa in monolayers, at 8.0 GPa in bilayers, and at 13.7 GPa in multilayers, respectively. With the enhancement of pressure-induced interlayer interaction, the crystal phase transition due to layer sliding like 2Hc to 2Ha occurs at 14.8 and 18.7 GPa in bilayers and multilayers, as evidenced by the split of E12g and B1u. The electronic phase transition of the monolayer is supposed to be a direct K-K bandgap changing to an indirect Λ-K bandgap at 2.6 GPa. These observations contribute to a better understanding of the impact of interlayer interactions on the modulation of WS2 energy bands and structure, as well as fundamental studies of two-dimensional layered materials, which can inform the development of device applications.

2D material platform for overcoming the amplitude–phase tradeoff in ring resonators

Compact and high-speed electro-optic phase modulators play a vital role in various large-scale applications including optical computing, quantum and neural networks, and optical communication links. Conventional electro-refractive phase modulators such as silicon (Si), III-V and graphene on Si suffer from a fundamental tradeoff between device length and optical loss that limits their scaling capabilities. High-finesse ring resonators have been traditionally used as compact intensity modulators, but their use for phase modulation has been limited due to the high insertion loss associated with the phase shift. Here, we show that high-finesse resonators can achieve a strong phase shift with low insertion loss by simultaneous modulation of the real and imaginary parts of the refractive index, to the same extent, i.e., ΔnΔk∼1. To implement this strategy, we demonstrate an active hybrid platform that combines a low-loss SiN ring resonator with 2D materials such as graphene and transition metal dichalcogenide [tungsten disulphide (WSe2)], which induces a strong change in the imaginary and real parts of the index. Our platform consisting of a 25 µm long Gr-Al2O3-WSe2 capacitor embedded on a SiN ring of 50 µm radius (∼8% ring coverage) achieves a continuous phase shift of (0.46±0.05)π radians with an insertion loss (IL) of 3.18±0.20 dB and a transmission modulation (ΔTRing) of 1.72±0.15dB at a probe wavelength (λ p ) of 1646.18 nm. We find that our Gr-Al2O3-WSe2 capacitor exhibits a phase modulation efficiency (Vπ2⋅L) of 0.530±0.016V⋅cm and can support an electro-optic bandwidth of 14.9±0.1GHz. We further show that our platform can achieve a phase shift of π radians with an IL of 5 dB and a minimum ΔT of 0.046 dB. We demonstrate the broadband nature of the binary phase response, by measuring a phase shift of (1.00±0.10)π radians, with an IL of 5.20±0.31dB and a minimal ΔTRing of 0.015±0.006dB for resonances spanning from 1564 to 1650 nm. This SiN–2D hybrid platform provides the design for compact and high-speed reconfigurable circuits with graphene and transition metal dichalcogenide (TMD) monolayers that can enable large-scale photonic systems.

The Effect of Pyranine and MoS2 Content on the Optical Properties of Polyacrylamide-MoS2 Composite Gels

The most favorable members of the class of two-dimensional (2D) materials, molybdenum sulfide (MoS2), graphene, and tungsten disulfide (WS2) have become a thriving research frontier for many applications, ranging from catalysis to optoelectronic devices, due to their superior electronic behavior and mechanical properties. Making a new, smart, hydrogel when incorporating MoS2 into basic hydrogels can change their optical, electronic, and mechanical properties. In this work, MoS2-doped polyacrylamide (PAAm) gels were prepared via the free radical crosslinking copolymerization technique at room temperature without pyranine which is often used for crosslinking PAAm. The optical properties of PAAm-MoS2 composite gels were investigated, and they were analyzed using ultraviolet (UV) and fluorescence spectroscopy. The absorbance was measured before and after diffusion of MoS2-doped PAAm, and after the release of pyranine in and out of the composite gel, respectively. The shift of the absorption edge toward shorter wavelengths was seen when the quantity of MoS2 in the PAAm composite gels was decreased. The constituents included in the polymer composites exhibited notable photon energy absorption within the visible and ultraviolet spectra. This absorption phenomenon induced electron transitions to states of elevated energy. Parameters, such as refractive index and extinction coefficient, were analyzed with respect to the content of MoS2. When the MoS2 amount was increased in the gels, the percentage of reflectance increased. The extinction coefficient increased at longer wavelength and it decreased in the UV range, the shorter wavelength region. The results suggested that MoS2-doped PAAm composite gels show promising optoelectronic properties for developing optoelectronic devices.

Comparative study on various morphologies of WS2 for electrochemical hydrogen evolution reaction

Nowadays, the advancement of cost-effective and efficient electrocatalysts holds significant importance in facilitating the progress of high-performance electrochemical hydrogen evolution reaction (HER). Tungsten disulfides (WS2) are well recognized as highly promising electrocatalysts for HER due to their exceptional catalytic performance, outstanding stability, and comparatively affordable price. In this study, we used ammonium metatungstate hydrate and thioacetamide as precursors to fabricate WS2 nanoflowers (NFs) by hydrothermal method, whereas WS2-flakes were prepared from ammonium tetrathiotungstate through the thermolysis technique. These structures were evaluated for HER electrocatalytic activity in acidic media. The results revealed that WS2-NFs exhibit higher catalytic activity than WS2-flakes, with an overpotential of 325 mV to obtain a current density of 10 mA cm−2 and a Tafel slope of 92.3 mV dec−1. This performance was attributed to the larger electrochemically active surface area of WS2-NFs compared to WS2-flakes materials. The results of this study could bring the basis for further studies on the synthesis of WS2-based catalytic materials for HER.
 ® 2023 Journal of Science and Technology - NTTU

Interaction of graphene and WS2 with neutrophils and mesenchymal stem cells: implications for peripheral nerve regeneration.

Graphene and bidimensional (2D) materials have been widely used in nerve conduits to boost peripheral nerve regeneration. Nevertheless, the experimental and commercial variability in graphene-based materials generates graphene forms with different structures and properties that can trigger entirely diverse biological responses from all the players involved in nerve repair. Herein, we focus on the graphene and tungsten disulfide (WS2) interaction with non-neuronal cell types involved in nerve tissue regeneration. We synthesize highly crystalline graphene and WS2 with scalable techniques such as thermal decomposition and chemical vapor deposition. The materials were able to trigger the activation of a neutrophil human model promoting Neutrophil Extracellular Traps (NETs) production, particularly under basal conditions, although neutrophils were not able to degrade graphene. Of note is that pristine graphene acts as a repellent for the NET adhesion, a beneficial property for nerve conduit long-term applications. Mesenchymal stem cells (MSCs) have been proposed as a promising strategy for nerve regeneration in combination with a conduit. Thus, the interaction of graphene with MSCs was also investigated, and reduced viability was observed only on specific graphene substrates. Overall, the results confirm the possibility of regulating the cell response by varying graphene properties and selecting the most suitable graphene forms.

Cu9S5-nanowire-pinned-WS2 sheets on hollow cubic carbon for synergistic promotion in K-ion battery performance

Cu9S5-nanowire-pinned-WS2 sheets on a hollow cubic carbon multi-level composite structure exhibits a high capacity (406 mA h g−1 after 150 cycles at 200 mA g−1) and excellent rate performance (246 mA h g−1 at 20 A g−1) as an anode material of PIBs.

Influence of Band Alignment, Electric Field, Layer Thickness, Temperature, Series Resistance, and Shunt Resistance on Lead-Free Double Perovskite Solar Cells with Spiro-OMeTAD: A SCAPS-1D Simulation Study

Investigating the photovoltaic (PV) performance of lead-free double perovskite solar cells (DPSCs) with a structure comprising a fluorine-doped tin oxide (FTO) substrate, tungsten disulfide (WS2) as the electron transport layer (ETL), inorganic-lead free and non-toxic double perovskite La2NiMnO6 absorber, Spiro-OMeTAD as the hole transport layer (HTL), and gold (Au) electrode using the SCAPS-1D framework is crucial for optimizing their efficiency. Despite significant progress in DPSCs, there remains a research gap in understanding the fundamental mechanisms underlying their performance, particularly in optimizing material properties and device architectures for enhanced efficiency. This study focuses on optimizing the device architecture by investigating the impact of band alignment, electric field, layer thickness, temperature, series resistance, and shunt resistance on enhancing DPSC performance. Achieving an power conversion efficiency (PCE) of 18.51% with detailed analysis of the DPSCs highlights the key factors influencing their efficiency. These findings contribute valuable insights into enhancing the performance of DPSCs, advancing their potential for widespread adoption in solar energy conversion.

Enhancing the stretchability of two-dimensional materials through kirigami: a molecular dynamics study on tungsten disulfide.

In recent years, the 'kirigami' technique has gained significant attention for creating meta-structures and meta-materials with exceptional characteristics, such as unprecedented stretchability. These properties, not typically inherent in the original materials or structures, present new opportunities for applications in stretchable and wearable electronics. However, despite its scientific and practical significance, the application of kirigami patterning on a monolayer of tungsten disulfide (WS2), an emerging two-dimensional (2D) material with exceptional mechanical, electronic, and optical properties, has remained unexplored. This study utilizes molecular dynamics (MD) simulations to investigate the mechanical properties of monolayer WS2 with rectangular kirigami cuts. We find that, under tensile loading, the WS2 based kirigami structure exhibits a notable increase in tensile strain and a decrease in tensile strength, thus demonstrating the effectiveness of the kirigami cutting technique in enhancing the stretchability of monolayer WS2. Additionally, increasing the overlap ratio enhances the stretchability of the structure, allowing for tailored high strength or high strain requirements. Furthermore, our observations reveal that increasing the density of cuts and reducing the length-to-width ratio of the kirigami nanosheet further improve the fracture strain, thereby enhancing the overall stretchability of the proposed kirigami patterned structure of WS2.

A fluorescence aptamer sensor utilizing WS2 nanosheets for sensitive detection of patulin: enhanced specificity and wide applicability.

A tungsten disulfide (WS2) nanosheet-based aptamer sensor was developed to detect patulin (PAT). The 5'-end of the PAT aptamer was modified with a cyanine 3 (Cy3) fluorophore, which self-assembled on WS2 nanosheets. The interaction between the Cy3 fluorophore at the 5'-end of the PAT aptamer and the WS2 nanosheets resulted in reduced fluorescence (FL) intensity due to fluorescence resonance energy transfer (FRET). The introduction of PAT into this sensing system led to hybridization with the PAT aptamer, forming a G-quadruplex/PAT complex with low affinity for the WS2 nanosheet surface. This hybridization increased the distance between the Cy3 fluorophore and the WS2 nanosheets, inhibiting FRET and producing a strong FL signal. Under optimal experimental conditions, the FL intensity of the sensing system demonstrated an excellent linear correlation with PAT concentrations ranging from 0.5 to 40.0 ng mL-1, and it achieved a detection limit (S/N = 3) of 0.23 ng mL-1. This sensing system offers enhanced specificity for PAT detection and has the potential for broad application in detecting other toxins by substituting the sequence of the recognition aptamer.

Determination and investigation of defect domains in multi-shape monolayer tungsten disulfide.

Single-layer tungsten disulfide (WS2) is among the most widely investigated two-dimensional materials. Synthesizing it over large areas would enable the exploitation of its appealing optical and electronic properties in industrial applications. However, defects of different nature, concentration and distribution profoundly affect the optical as well as the electronic properties of this crystal. Controlling the defect density distribution can be an effective way to tailor the local dielectric environment and therefore the electronic properties of the system. In this work we investigate the defects in single-layer WS2, grown in different shapes by liquid phase chemical vapor deposition, where the concentration of certain defect species can be controlled by the growth conditions. The properties of the material are surveyed by means of optical spectroscopy, photoelectron spectroscopy and Kelvin probe force microscopy. We determine the chemical nature of the defects and study their influence on the optical and electronic properties of WS2. This work contributes to the understanding of the microscopic nature of the intrinsic defects in WS2, helping the development of defect-based technologies which rely on the control and engineering of defects in dielectric 2D crystals.

First-principles calculations on monolayer WX2 (X = S, Se) as an effective drug delivery carrier for anti-tuberculosis drugs.

Tuberculosis (TB) remains a major global health concern, necessitating the exploration of novel drug delivery systems to combat the challenges posed by conventional approaches. We investigated the potential of monolayer transition metal dichalcogenides (TMDs) as an innovative platform for efficient and targeted delivery of antituberculosis drugs. Specifically, the electronic and optical properties of prominent TB drugs, isoniazid (INH) and pyrazinamide (PZA), adsorbed on tungsten diselenide (WSe2) and tungsten disulfide (WS2) monolayers were studied using first-principles calculations based on density functional theory (DFT). The investigation revealed that the band gaps of WSe2 and WS2 monolayers remain unaltered upon adsorption of PZA or INH, with negative adsorption energy indicating stable physisorption. We explored different vertical and horizontal configurations, and the horizontal ones were more stable. When INH and PZA drugs were horizontally adsorbed together on WSe2, the most stable configuration was found with an adsorption energy of -2.35 eV. Moreover, the adsorbed drugs could be readily released by light within the visible or near-infrared (NIR) wavelength range. This opened up possibilities for their potential application in photothermal therapy, harnessing the unique properties of these 2D materials. The comprehensive analysis of the band structures and density of states provides valuable insights into how the drug molecules contributed to the conduction and valence bands. The optical responses of anti-TB drugs adsorbed in 2D WSe2 and WS2 were similar to those of pristine 2D WSe2 and WS2. We demonstrated the temperature-dependent release mechanism of our 2D WSe2 and WS2 drug complexes, confirming the feasibility of releasing the discussed anti-tuberculosis drugs by generating heat through photothermal therapy. These findings hold significant promise for developing innovative drug delivery systems that have enhanced efficacy for targeted and low-toxic TB treatment.

Utilizing machine learning to enhance performance of thin-film solar cells based on Sb2(S x Se1-x )3: investigating the influence of material properties.

Antimony chalcogenides (Sb2(S x Se1-x )3) have drawn attention as a potential semiconducting substance for heterojunction photovoltaic (PV) devices due to the remarkable optoelectronic properties and wide range of bandgaps spanning from 1.1 to 1.7 eV. In this investigation, SCAPS-1D simulation software is employed to design an earth abundant, non-toxic, and cost-effective antimony sulfide-selenide (Sb2(S,Se)3)-based thin-film solar cell (TFSC), where tungsten disulfide (WS2) and cuprous oxide (Cu2O) are used as an electron transport layer (ETL) and hole transport layer (HTL), respectively. The PV performance parameters such as power conversion efficiency, open-circuit voltage (V oc), short-circuit current (J sc), and fill factor (FF) are assessed through adjustments in material properties including thickness, acceptor concentration, bulk defect density of the absorber, defect state of absorber/ETL and HTL/absorber interfaces, operating temperature, work function of the rear electrode, and cell resistances. This analysis aims to validate their collective impact on the overall efficiency of the designed Ni/Cu2O/Sb2(S,Se)3/WS2/FTO/Al TFSC. The optimized physical parameters for the Sb2(S,Se)3 TFSC lead to impressive PV outputs with an efficiency of 30.18%, V oc of 1.02 V, J sc of 33.65 mA cm-2, and FF of 87.59%. Furthermore, an artificial neural network (ANN) machine learning (ML) algorithm predicts the optimal PCE by considering five semiconductor parameters: absorber layer thickness, bandgap, electron affinity, electron mobility, and hole mobility. This model, which has an approximate correlation coefficient (R 2) of 0.999, is able to predict the data with precision. This numerical analysis provides valuable data for the fabrication of an environmentally friendly, economical, and incredibly non-toxic efficient heterojunction TFSC.

Asymmetric contact-induced selective doping of CVD-grown bilayer WS2 and its application in high-performance photodetection with an ultralow dark current.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are excellent candidates for high-performance optoelectronics due to their high carrier mobility, air stability and strong optical absorption. However, photodetectors made with monolayer TMDs often exhibit a high dark current, and thus, there is a scope for further improvement. Herein, we developed a 2D bilayer tungsten disulfide (WS2) based photodetector (PD) with asymmetric contacts that exhibits an exceptionally low dark current and high specific detectivity. High-quality and large-area monolayer and bilayer WS2 flakes were synthesized using a thermal chemical vapor deposition system. Compared to conventional symmetric contact electrodes, utilizing metal electrodes with higher and lower work functions relative to bilayer WS2 aids in achieving asymmetric lateral doping in the WS2 flakes. This doping asymmetry was confirmed through the photoluminescence spectral profile and Raman mapping analysis. With the asymmetric contacts on bilayer WS2, we find evidence of selective doping of electrons and holes near the Ti and Au contacts, respectively, while the WS2 region away from the contacts remains intrinsic. When compared with the symmetric contact case, the dark current in the WS2 PD with asymmetric (Au, Ti) contact decreases by an order of magnitude under reverse bias with a concomitant increase in the photocurrent, resulting in an improved on/off ratio of ∼105 and overall improved device performance under identical illumination conditions. We explained this improved performance based on the energy band alignment showing a unidirectional charge flow under light illumination. Our results indicate that the planar device structure and compatibility with current nanofabrication technologies can facilitate its integration into advanced chips for futuristic low-power optoelectronic and nanophotonic applications.

Strain engineering of the mechanical properties of two-dimensional WS2.

Tuning the physical properties of two-dimensional (2D) materials is crucial for their successful integration into advanced applications. While strain engineering demonstrated an efficient means to modulate the electrical and optical properties of 2D materials, tuning their mechanical properties has not been carried out. Here we applied compressive strain through the buckling metrology to 2D tungsten disulfide (WS2), which demonstrated mechanical softening manifested by the reduction of its effective Young's modulus. Raman modes analysis of the strained WS2 also showed strain-dependent vibrational modes softening and revealed its Grüneisen parameter (γ E2g = 0.29) and its shear deformation potential (β E2g = 0.56) - both are similar to the values of other 2D materials. In parallel, we conducted a molecular dynamic simulation that confirmed the validity of continuum mechanics modeling in the nanoscale and revealed that due to sequential atomic-scale buckling events in compressed WS2, it shows a mechanical softening. Therefore, by tuning the mechanical properties of WS2 we shed light on its fundamental physics, thus making it an attractive candidate material for high-end applications, such as tunable sensors and flexible optoelectronic devices.

Theoretical study on the nucleation control of WS<sub>2 </sub>on Au(111) surfaces

Two-dimensional tungsten disulfide (WS<sub>2</sub>), as a semiconductor material with unique layer-dependent electronic and optoelectronic characteristics, demonstrates a promising application prospect in the field of optoelectronic devices. The fabrication of wafer-scale monolayer WS<sub>2</sub> films is currently a critical challenge that propels their application in advanced transistors and integrated circuits. Chemical vapor deposition (CVD) is a feasible technique for fabricating large-area, high-quality monolayer WS<sub>2</sub> films, yet the complexity of its growth process results in low growth efficiency and inconsistent film quality of WS<sub>2</sub> .In order to guide experimental efforts to diminish grain boundaries in WS<sub>2</sub> ,thereby improving film quality to enhance electronic performance and mechanical stability, this study investigates the nucleation mechanisms of WS<sub>2</sub> during CVD growth through first-principles theoretical calculations. By considering chemical potential as a crucial variable, we analyze the growth energy curves of WS<sub>2</sub> under diverse experimental conditions. Our findings demonstrate that modulating the temperature or pressure of the tungsten and sulfur precursors can decisively influence the nucleation rate of WS<sub>2</sub>. Notably, the nucleation rate reaches a peak at a tungsten source temperature of 1250 K, while an increase in sulfur source temperature or a decrease in pressure can suppress the nucleation rate, thereby enhancing the crystallinity and uniformity of monolayer WS<sub>2</sub>. These insights not only furnish a robust theoretical foundation for experimentally fine-tuning the nucleation rate as needed but also provide strategic guidance for optimizing experimental parameters to refine the crystallinity and uniformity of monolayer WS<sub>2</sub> films. Such advancements are expected to accelerate the deployment of WS<sub>2</sub> materials in a range of high-performance electronic devices, marking a significant stride in the field of materials science and industrial applications.

Tunable spectral properties of PVB/WS2 impregnated fabrics in VIS, IR and RF part of the EMS

The application of nanomodified polymer impregnation on knitted polyester fabrics was studied to improve camouflage characteristics in VIS, IR, and RF domains to enhance multispectral camouflage protection. Nanoparticles of tungsten disulfide (WS2) were dispersed in an ethanol solution of poly (vinyl butyral) (PVB) and applied as a thin impregnation on polyester fabrics already dyed in camouflage shades. A reference sample impregnated only with PVB, without WS2, was also prepared in the same way. Parallel to the impregnated fabrics, a neat knitted polyester textile sample was submitted to all the examination methods. Diffuse reflection, specular gloss, and color coordinates were measured for all the samples. Moreover, the samples were observed using IR thermography in medium and long-wavelength infrared parts of the electromagnetic spectrum. The best suppression (≥20%) in the IR range of EMS was achieved for the dark green shade sample by applying PVB alone and/or adding PVB/ WS2. RF domain measurement analysis of how impregnated fabrics influence effective Radar Cross Section (RCS), K band radar was used, with the measurements done in terrain conditions. The decrease of the mean RCS value between 11% and 41% was achieved. The obtained results indicate that the addition of WS2 has a positive effect on the observed characteristics and that there is a possibility of using this newly impregnated knitwear in the wider area of the EMS as a camouflage material.