Search Results (24)

Within this study, the influence of particles of different types, natures, and sizes on the mechanical and corrosion resistance of pigmented systems containing spherical zinc was studied. For this study, prominent representatives from the group of transition metal dichalcogenides (MoS₂, WS₂), layered transition metal oxides (MoO₃, WO₃), and other semiconductor materials (ZnS and ZnO) were used. The layered ultra-thin structure of these particles was predisposed to provide enhanced mechanical and anti-corrosion performance. The mechanical properties of the studied coatings were tested using standardized mechanical tests, while the anti-corrosion performance of these coatings was studied using standardized cyclic corrosion tests and the linear polarization electrochemical technique. The results of the experimental techniques bring completely original knowledge about the action of these pigments in paint systems pigmented with zinc. The results of experimental techniques have shown enhancement and an increase in both mechanical and anti-corrosion performance when using these special types of inorganic pigments. In particular, with organic coatings pigmented with MoO₃, there was an increase in mechanical resistance mainly due to its morphology and layered structure. In addition, a significant enhancement of the anti-corrosion efficiency was noted for this type of organic coating due to the enhancement of individual types of action mechanisms typical and proven for zinc-pigmented systems. These original findings can be used in the search for possibilities to reduce the zinc content in zinc-pigmented organic coatings. This partial replacement of zinc particles leads not only to a reduction in the zinc content in the system but also to a significant strengthening of the mechanical resistance and an increase in the corrosion efficiency of the system. Full article

The detection of trimethylamine (TMA) is critically important due to its toxic and flammable nature, which poses significant risks to human health and the environment. However, achieving high response, rapid kinetics, selectivity, and low operating temperatures in TMA sensing remains challenging. In this study, WS₂/WO₃ nanohybrids with flower-like hierarchical structures were synthesized via an in situ sulfurization process, utilizing varying amounts of thioacetamide to control the sulfurization state of WO₃. These novel hierarchical WS₂/WO₃ nanohybrids exhibit remarkable selectivity towards TMA, as well as rapid response and recovery characteristics. Specially, the optimal WS₂/WO₃ sensor, composed of 5% WS₂/WO₃ nanohybrids, demonstrates exceptional TMA sensing performance, including a high response (19.45 at 10 ppm), good repeatability, reliable long-term stability, and a low theoretical detection limit (15.96 ppb). The superior sensing capabilities of the WS₂/WO₃ nanohybrids are attributed to the formation of p-n heterojunctions at the interface, the unique hierarchical structures, and the catalytic activity of WS₂. Overall, this work provides a straightforward and versatile approach for synthesizing multifunctional nanomaterials by combining metal oxide micro-flowers with transition metal dichalcogenide nanoflakes for applications in monitoring TMA in complex environments. Full article

The microstructures and structures of modified Al₂O₃/IF-WS₂ coatings prepared on aluminum substrates are studied. Amorphous Al₂O₃ oxide coatings are obtained on EN AW 5251 aluminum alloy using the electrooxidation process. The quality of the IF-WS₂ nanopowder is of great importance in the process of its introduction into the nanopores of the Al₂O₃ oxide coating. Commercial nanopowder tends to agglomerate, and without appropriate pretreatment, it is difficult to introduce it into the nanopores of the coating. To improve the degree of fragmentation of the IF-WS₂ nanopowder, an experiment was carried out to distribute the nanopowder in the presence of strong ultrasounds, and new conditions for introducing the powder into the nanopores were used. A two-level design of experiment (DOE) was used. The SEM examination made it possible to conclude that Method A contributed to a more even distribution of nanoparticles in the microstructure of Al₂O₃ coatings. GIXD analyses showed the presence of WO₃ derived from the IF-WS₂ modifier next to crystal structures derived from aluminum and WS₂. Modification of coatings using Method A resulted in surfaces with lower contact angles measured with polar liquids and higher surface free energy compared to Method B. Full article

Two-dimensional (2D) vertical van der Waals heterostructures (vdWHs) show great potential across various applications. However, synthesizing large-scale structures poses challenges owing to the intricate growth parameters, forming unexpected hybrid film structures. Thus, precision in synthesis and thorough structural analysis are essential aspects. In this study, we successfully synthesized large-scale structured 2D transition metal dichalcogenides (TMDs) via chemical vapor deposition using metal oxide (WO₃ and MoO₃) thin films and a diluted H₂S precursor, individual MoS₂, WS₂ films and various MoS₂/WS₂ hybrid films (Type I: Mo_xW_1−xS₂ alloy; Type II: MoS₂/WS₂ vdWH; Type III: MoS₂ dots/WS₂). Structural analyses, including optical microscopy, Raman spectroscopy, transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy, and cross-sectional imaging revealed that the A_1g and E_2g modes of WS₂ and MoS₂ were sensitive to structural variations, enabling hybrid structure differentiation. Type II showed minimal changes in the MoS_2′s A_1g mode, while Types I and III exhibited a ~2.8 cm⁻¹ blue shift. Furthermore, the A_1g mode of WS₂ in Type I displayed a 1.4 cm⁻¹ red shift. These variations agreed with the TEM-observed microstructural features, demonstrating strain effects on the MoS₂–WS₂ interfaces. Our study provides insights into the structural features of diverse hybrid TMD materials, facilitating their differentiation through Raman spectroscopy. Full article

The synthesis, characterization and biological activity of tungstenocenes with varying biologically active (O,O–), (S,O–) and (N,O–) chelates are described. Complexes were characterized by ¹H and ¹³C NMR, elemental analysis, ESI-mass spectrometry, FT-IR spectroscopy and X-ray diffraction analysis. The aqueous stability was studied by UV/Vis spectroscopy and the W^IV to W^V process by cyclic voltammetry. The cytotoxicity was determined by the MTT assay in A549, CH1/PA-1 and SW480 cancer cells as well as in IMR-90 human fibroblasts. Extensive biological evaluation was performed in three other human cancer cell lines (HCT116, HT29 and MCF-7) in monolayer and multicellular tumor spheroid cultures to better understand the mode of action. Lead compounds showed promising in vitro anticancer activity in all cancer cell lines. Further studies yielded important insights into apoptosis induction, ROS generation, different patterns in metal distribution (detected by LA-ICP-TOF-MS), changes in KI67 (proliferation marker) expression and DNA interactions. The results based on qualitative and quantitative research designs show that complexes containing (S,O–) chelates are more active than their (O,O–) and (N,O–) counterparts. The most striking results in spheroid models are the high antiproliferative capacity and the different distribution pattern of two complexes differing only in a W–S or W–O bond. Full article

The study investigates the two different underlying ablation mechanisms of WS₂ processed by femtosecond (fs) laser with different fluences. With increasing fluence, the saturable expansion of craters and the transformation of three distinct crater morphologies are found. The material response and the transfer and deposition of laser energy are tracked by using a plasma model based on the classical single rate equation model and the Drude model. The results of the numerical simulation and time-resolved transient reflectivity reveal the two different ablation mechanisms, which are coulomb explosion and phase explosion. The mechanism of material removal is distinguished by the critical threshold of 0.85 J/cm². In addition, the internal ablation region exhibits a high concentration of defects and WO₃ according to the results of Raman spectra, X-ray photoelectron spectra, and morphology-dependent photoluminescence mapping. Due to the high concentration with high fluence, the device of WS₂/Si p-n junction exhibits a 2.6 times enhancement on the current under forward bias. The findings would be of value to engineer structures to tailor the optoelectronic response of WS₂ and to develop potential future optoelectronic devices. Full article

Tungsten disulfide (WS₂) was prepared from W metal and WO₃ by ion beam sputtering and sulfurization in a different number of layers, including monolayer, bilayer, six-layer, and nine-layer. To obtain better crystallinity, the nine-layer of WS₂ was also prepared from W metal and sulfurized in a furnace at different temperatures (800, 850, 900, and 950 °C). X-ray diffraction revealed that WS₂ has a 2-H crystal structure and the crystallinity improved with increasing sulfurization temperature, while the crystallinity of WS₂ sulfurized from WO₃ (WS₂-WO₃) is better than that sulfurized from W-metal (WS₂-W). Raman spectra show that the full-width at half maximum (FWHM) of WS₂-WO₃ is narrower than that of WS₂-W. We demonstrate that high-quality monocrystalline WS₂ thin films can be prepared at wafer scale by sulfurization of WO₃. The photoluminescence of the WS₂ monolayer is strongly enhanced and centered at 1.98 eV. The transmittance of the WS₂ monolayer exceeds 80%, and the measured band gap is 1.9 eV, as shown by ultraviolet-visible-infrared spectroscopy. Full article

In this study, four kinds of nanoparticles, graphite, WS₂, Fe₃O₄, and TiN, were used as lubricating additives for steel/copper friction pairs to solve the problem of welding contact tube wear with non-copper-coated solid wire at high temperature. The single and composite nanoparticles have excellent dispersion stability in absolute ethanol under the action of the compound surfactant NaSTA + OA + PVP (i.e., sodium stearate, oleic acid, and polyvinylpyrrolidone). The tribological test results showed that the maximum decrement, with reference to the average coefficient of friction and wear volumes, were measured with nanoparticle concentration in 1:1:1 ratio at 300 °C. Compared with dry friction, the average friction coefficient and wear volume are reduced by 74.3% and 84.8%, respectively, which may be attributed to the formation of a stable tribo-film mainly composed of C–O, Fe₂O₃, WO₃, TiO₂, TiN_xO_y composite on the worn surface. Therefore, it is considered that the combined lubrication effects of the ball-bearing effect, repairing of worn surfaces, and the tribo-film resulted in the lowest friction and wear. Full article

This study focuses on the synthesis, characterization, and evaluation of the performance of core shell nanostructure adsorbent for hydrogen sulfide (H₂S) capture. Commercial coconut shell activated carbon (CAC) and commercial mixed gas of 5000 ppm H₂S balanced N₂ were used. With different preparation techniques, the CAC was modified by core shell impregnation with zinc oxide (ZnO), titanium oxide (TiO₂), potassium hydroxide (KOH), and zinc acetate (ZnAC₂). The core structure was prepared with CAC impregnated by single chemical and double chemical labelled with ZnAC₂-CAC (single chemical), ZnAC₂/KOH-CAC, ZnAC₂/ZnO-CAC, and ZnAC₂/TiO₂-CAC. Then, the prepared core was layered either with KOH, TiO₂, NH₃, or TEOS for the shell. The synthesized adsorbents were characterized in physical and chemical characterization through scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) analyzers. Operation of the adsorber column takes place at ambient temperature, with absolute pressure at 1.5 bar. The H₂S gas was fed into the column at 5.5 L/min and the loaded adsorbents were 150 g. The performance of synthesized adsorbent was analyzed through the adsorbent’s capability in capturing H₂S gas. Based on the results, ZnAc₂/ZnO/CAC_WOS shows a better adsorption capacity with 1.17 mg H₂S/g and a 53% increment compared to raw CAC. However, the degradation of the adsorbents was higher compared to ZnAc₂/ZnO/CAC_OS and to ZnAc₂/ZnO/CAC_WS ZnAc₂/ZnO/CAC_OS. The presence of silica as a shell has potentially increased the adsorbent’s stability in several cycles of adsorption-desorption. Full article

A one-step colloidal synthesis of hierarchical nanoflowers of WS₂ is reported. The nanoflowers were used to fabricate a chemical sensor for the detection of ammonia vapors at room temperature. The gas sensing performance of the WS₂ nanoflowers was measured using an in-house custom-made gas chamber. SEM analysis revealed that the nanoflowers were made up of petals and that the nanoflowers self-assembled to form hierarchical structures. Meanwhile, TEM showed the exposed edges of the petals that make up the nanoflower. A band gap of 1.98 eV confirmed a transition from indirect-to-direct band gap as well as a reduction in the number of layers of the WS₂ nanoflowers. The formation of WS₂ was confirmed by XPS and XRD with traces of the oxide phase, WO₃. XPS analysis also confirmed the successful capping of the nanoflowers. The WS₂ nanoflowers exhibited a good response and selectivity for ammonia. Full article

This paper presents a methodology to quantify oxidizing and reducing gases using n-type and p-type chemiresistive sensors, respectively. Low temperature sensor heating with pulsed UV or visible light modulation is used together with the application of the fast Fourier transform (FFT) to extract sensor response features. These features are further processed via principal component analysis (PCA) and principal component regression (PCR) for achieving gas discrimination and building concentration prediction models with R² values up to 98% and RMSE values as low as 5% for the total gas concentration range studied. UV and visible light were used to study the influence of the light wavelength in the prediction model performance. We demonstrate that n-type and p-type sensors need to be used together for achieving good quantification of oxidizing and reducing species, respectively, since the semiconductor type defines the prediction model’s effectiveness towards an oxidizing or reducing gas. The presented method reduces considerably the total time needed to quantify the gas concentration compared with the results obtained in a previous work. The use of visible light LEDs for performing pulsed light modulation enhances system performance and considerably reduces cost in comparison to previously reported UV light-based approaches. Full article

Inorganic fullerene-like tungsten disulfide particles have been proved to have good anti-friction and anti-wear properties as lubricating materials. As far as we know, however, when it is used as a lubricant additive, its behavior and action mechanism in the friction process are rarely studied. Herein, IF–WS₂ particles were synthesized by a Chemical Vapor Deposition (CVD) method. The effect of IF–WS₂ particle concentrations in the PAO6 oil on the tribological behaviors was investigated with a four-ball wear machine at both 75 and 100 °C. Additionally, the analyzed morphology and composition of nanomaterials and worn surfaces were analyzed by Scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The friction behavior in actual working conditions was studied by a wear testing machine. The experimental results show that compared with the original PAO6 oil, at a dispersion of 0.25 wt% in PAO6 oil, the IF–WS₂ particles showed the best performance in terms of coefficient of friction, wear scar diameter and wear mass, which significantly reduced by 27%, 43% and 87%, respectively. At the same time, in the process of friction, it was found that IF–WS₂ particles accumulated in the depressions to fill the scratches, and adsorption films and chemical films, including FeS₂, WS₂ and WO₃, were formed on the worn surfaces to avoid the direct contact among the friction pairs more effectively, resulting in the improved anti-wear performances. Additionally, the addition of IF–WS₂ particles effectively delayed the rise of lubricating oil temperature. In addition, dispersant span 80 can effectively improve the dispersion and stability of IF–WS₂ in PAO6. This work provides us for understanding the effective lubrication mechanism of IF–WS₂ particles in more detail and having a new acknowledge of the comprehensive performance of IF–WS₂/PAO6 oil. Full article

Transition metal chalcogenides have been widely studied as a promising electrocatalyst for the hydrogen evolution reaction (HER) in acidic conditions. Among various transition metal chalcogenides, tungsten disulfide (WS₂) is a distinguishable candidate due to abundant active sites and good electrical properties. Herein, we report a facile and selective synthetic method to synthesize WS₂ with an intriguing two-dimensional nanostructure by using cysteine (C₃H₇NO₂S) as a chemical agent. In addition, nitrogen can be incorporated during chemical synthesis from cysteine, which may be helpful for enhancing the HER. The electrocatalytic activity of N-doped WS₂ exhibits a promising HER in acidic conditions, which are not only higher than W₁₈O₄₉ nanowires and hex-WO₃ nanowires, but also comparable to the benchmark Pt/C. Moreover, excellent electrocatalytic stability is also demonstrated for acidic HER during long-term tests, thus highlighting its potential use of practical applications as an electrolyzer. Full article

Electrocatalysts featuring robust structure, excellent catalytic activity and strong stability are highly desirable, but challenging. The rapid development of two-dimensional transition metal chalcogenide (such as WO₃, MoS₂ and WS₂) nanostructures offers a hopeful strategy to increase the active edge sites and expedite the efficiency of electronic transport for hydrogen evolution reaction. Herein, we report a distinctive strategy to construct two-dimensional MoS₂@dWO₃ heterostructure nanosheets by in situ wet etching. Synthesized oxygen-incorporated MoS₂-was loaded on the surface of defective WO₃ square nanoframes with abundant oxygen vacancies. The resulting nanocomposite exhibits a low overpotential of 191 mV at 10 mA cm⁻² and a very low Tafel slope of 42 mV dec⁻¹ toward hydrogen evolution reaction. The long-term cyclic voltammetry cycling of 5000 cycles and more than 80,000 s chronoamperometry tests promises its outstanding stability. The intimate and large interfacial contact between MoS₂ and WO₃, favoring the charge transfer and electron–hole separation by the synergy of defective WO₃ and oxygen-incorporated MoS₂, is believed the decisive factor for improving the electrocatalytic efficiency of the nanocomposite. Moreover, the defective WO₃ nanoframes with plentiful oxygen vacancies could serve as an anisotropic substrate to promote charge transport and oxygen incorporation into the interface of MoS₂. This work provides a unique methodology for designing and constructing excellently heterostructure electrocatalysts for hydrogen evolution reaction. Full article

Establishing the metabolism pathway of the drug undergoing the hepatic biotransformation pathway is one of the most important aspects in the preclinical discovery process since the presence of toxic or reactive metabolites may result in drug withdrawal from the market. In this study, we present the structural elucidation of six, not described yet, metabolites of an antipsychotic molecule: molindone. The elucidation of metabolites was supported with a novel photocatalytical approach with the use of WO₃ and WS₂ assisted photochemical reactions. An UHPLC-ESI-Q-TOF combined system was used for the registration of all obtained metabolite profiles as well as to record the high resolution fragmentation spectra of the observed transformation products. As a reference in the in vitro metabolism simulation method, the incubation with human liver microsomes was used. Chemometric comparison of the obtained profiles pointed out the use of the WO₃ approach as being more convenient in the field of drug metabolism studies. Moreover, the photocatalysis was used in the direction of the main drug metabolite synthesis in order to further isolation and characterization. Full article