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The catalytic activities of the dispersed NixW(1−x)S2 catalysts were investigated for hydrocracking (HCK) of vacuum residue (VR) at 693 K, 9.5 MPa H2 with the same amount of catalyst loading of 0.113 mmol as a metal basis. The catalysts were prepared in situ in the reaction using nickel acetylacetonate and tungsten hexacarbonyl as Ni and W precursors, respectively. Structural properties of the dispersed catalysts were characterized by extended X-ray absorption fine structure and transmission electron microscopy, which confirmed the formation of a well-dispersed NixW(1−x)S2 phase in the size range 8–10 nm. Moreover, it was demonstrated that the bimetallic metal sulfides of NixW(1−x)S2 feature promotional activity in the VR HCK, showing higher turnover frequency values and less coke formation in VR HCK than monometal sulfides.

Syntheses of transition-metal dichalcogenides (TMDs) using colloidal-chemistry approaches are gaining significant interest in recent years, as these methods enable the morphology and properties of the nanocrystals to be tuned for targeted applications. In this work, by only varying the ligand used during synthesis, we synthesized nanoflowers with oleic acid (OA) and 1T' phase dominated WSe2 nanosheets with oleylamine (OLA). WSe2 nanocrystals show slower rate of formation for the metastable 1T' phase. Surface chemistry analyses of the synthesized nanocrystals by solution NMR establish that neither of the ligands bind strongly to the surface of nanocrystals but are in a dynamic coordination with the WSe2 surface. A further examination of the coordination of tungsten hexacarbonyl (W(CO)(6)) with the respective ligands confirms that W(CO)(6) decomposes in OA, losing its octahedral symmetry, which leads to fast reactivity in the flask. In contrast to this, W(CO)(6) reacts with OLA to form a new complex, which leads to slower reactivity and crystallization of the synthesized nanocrystals in the octahedral 1T' phase. These insights into the influence of precursor-ligand chemistry on reaction outcome and the peculiar surface chemistry of colloidal TMD nanocrystals will be instrumental in developing future colloidal TMD nanocrystals.

Using a metalorganic chemical vapor deposition (MOCVD) technique and a tungsten hexacarbonyl W(CO)6 as a precursor, a stable and continuous coating consisting of nonstoichiometric WC1-x nanoparticles with sizes from 10 to 30 nm on the surface of multi-walled carbon nanotubes (CNTs) was obtained. The resulting hybrid WC1-x/CNTs structures had a developed surface morphology, which contributed to a more complete realization of the potential of the physical and mechanical properties of CNTs when used as reinforcement in composite materials. Comparative assessment of aluminum matrix nanocomposites AA5049 + 5 wt% CNTs and AA5049 + 5 wt% WC1-x/CNTs obtained by high energy ball milling and subsequent hot consolidation at 450°С shows that the WC1-x ceramic coating on the carbon nanotubes surface acts as a barrier layer at the interface, preventing the Al4C3 in situ formation at the matrix/CNT boundary. Coating of carbon nanotubes with WC1-x nanoparticles leads to a significant increase in the physical and mechanical properties of aluminum matrix nanocomposites, in particular, to an increase in the compressive strength from 810 ± 8 MPa to 893 ± 7 MPa, fracture deformation from 3.7% to 4.9%, Young's modulus from 102 ± 6 GPa to 110 ± 4 GPa, and microhardness from 152 ± 6 HV to 176 ± 8 HV in comparison with using of CNTs in the as-synthesized state.

The reaction of digallane [(dpp-bian)Ga—Ga(dpp-bian)] (1) (dpp-bian is 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene dianion) with chromium or tungsten hexacarbonyl affords the complexes [(dpp-bian)Ga—Cr(CO)5] (2) and [(dpp-bian)Ga—W(CO)5] (3), respectively, containing the neutral radical [(dpp-bian)Ga:]. In both cases, temperature-dependent solvation of the gallium center was observed in a tetrahydrofuran solution. The recrystallization of compound 2 from pyridine gave the new complex [(dpp-bian)(Py)Ga—Cr(CO)5] (4). New compounds 2–4 were characterized by EPR and IR spectroscopy and elemental analysis. The molecular structures of complexes 2–4 were established by single-crystal X-ray diffraction.

The volatile synthetic products of photochemical vapor generation (PVG) of Os(IV) and W(VI) have been confirmed by GC-MS. Osmium tetroxide has been identified as the species generated from an oxidizing medium of dilute nitric acid, and tungsten hexacarbonyl is produced during PVG from a reducing medium of formic acid. Attempts to ascertain the PVG products of Os and Ru generated in high yield from reducing media (i.e., acetic and formic acids, respectively in the presence of metal sensitizers) were unsuccessful, possibly due to their instability or reactivity with the GC support, and thus remain to be identified using more direct approaches such as Direct Analysis in Real Time (DART)-MS. The mass spectra for OsO₄ and W(CO)₆, reported here for the first time, serve to aid the further development/refinement of mechanistic models for PVG.

—A one-pot synthesis of dispersed platinum-tungsten composites has been developed. Initially, using tungsten hexacarbonyl as a precursor in solution in supercritical CO2 in the presence of oxygen as an oxidizer promoting thermal decomposition of the precursor, dispersed particles of tungsten oxide with a grain size of about 100 nm and an aggregate size of 200–500 nm have been synthesized. Then, these dispersed particles have been used as a substrate for the subsequent deposition of platinum nanoparticles, which includes two stages: (1) forming a film of an organometallic precursor by deposition from a solution in supercritical CO2 and (2) thermal decomposition of the precursor. Two types of platinum precursors, the dimethyl(1,5-cyclooctadiene)platinum and platinum hexafluoroacetylacetonate, which are both soluble in supercritical CO2, are typically used in the practice of similar studies. The size of the platinum nanoparticles formed using the former and latter precursors are 2.3 ± 0.7 nm and 3.5 ± 0.8 nm, respectively. The composites obtained are characterized by a relatively narrow size distribution of the noble metal nanoparticles and their uniform distribution over the surface of the particles of the dispersed carrier. Such materials may be of interest for (electro)catalysis tasks.

This paper studied the feasibility of a new solution-processed method to manufacture black tungsten nanostructures by laser conversion of tungsten hexacarbonyl precursor on the Inconel 625 substrate under argon atmosphere at ambient pressure. The results show that sublimation of the precursor can be prevented if the decomposition temperature (&gt, 170 °C) is achieved using the laser heating method. Three different laser powers from 60–400 W were used to investigate the role of laser parameters on the conversion. It was found that lower laser power of 60 W resulted in a mixture of unconverted precursor and converted tungsten. Higher laser powers &gt, 200 W resulted in α-W (BCC) in one step without further heat treatment. Different oxygen concentrations from 0.5 ppm to 21 vol% were used in the laser canister to investigate the effect of oxygen concentration on the conversion. It was found that the hard vacuum (&gt, 10−4 torr) or hydrogen is not necessary to obtain α-W (BCC). The solar absorptance varied from 63–97%, depending on the amount of precursor deposited on the substrate and oxygen content in the laser canister. This solution-based laser conversion of tungsten precursor is a scalable method to manufacture tungsten coatings for high-temperature applications.

Vibration-cavity polaritons, which are produced by strong coupling between an optical cavity and a molecular vibration, can modify chemical reaction rates and branching ratios. However the observed effects are poorly understood. To gain insight into how these polaritons might alter molecular processes, we used ultrafast pump-probe and two-dimensional infrared spectroscopies to characterize polariton excited state dynamics. Our earlier studies on vibration-cavity polaritons with tungsten hexacarbonyl demonstrated that much of the response is due to so-called reservoir or uncoupled excited state absorption as well as polariton contraction. In recent studies, we have used 2D IR and spectrally filtered pump-probe studies on the nitroprusside anion in methanol to determine the transition frequencies and dynamics of polariton excited states allowing us to extract polariton dephasing timescales as well as incoherent polariton population which at a significantly longer timescale.

Saturable absorption, in which optical absorption decreases as the incident intensity increases, is commonly utilized in the visible and near-infrared for laser applications. In the mid-infrared, m...

UV photodissociation of tungsten hexacarbonyl W(CO)6 has been studied in the molecular beam conditions using time-of-flight mass spectrometry and velocity map imaging. Irradiation of W(CO)6 by puls...

The effect of precursor on the properties of nanosized sulfide catalysts prepared by the in situ decomposition of nickel–tungsten compounds is studied. Precursors are nickel-thiotungsten complexes [(Ph)3S]2Ni(WS4)2 in the hydrocarbon feedstock, [BMPip]2Ni(WS4)2 in the hydrocarbon feedstock and ionic liquid, and tungsten hexacarbonyl in the hydrocarbon feedstock; oil-soluble salt nickel(II) 2-ethyl hexanoate is used as a source of nickel. The synthesized catalysts are investigated by electron microscopy methods, X-ray powder diffraction, and X-ray photoelectron spectroscopy. Diffusion and chemical reactions in nanosystems are described by the methods of extended irreversible thermodynamics based on a postulate according to which additional variables are time derivatives of usual thermodynamic variables. It is shown that, as the size of nanoparticles decreases, the velocities of diffusion and oxidation chemical reaction in catalyst domains decline; as a result, the content of oxygen in the sample prepared in the hydrocarbon feedstock is lower than that in the sample prepared in the ionic liquid.

Electrochemically active nanocrystalline tungsten oxide was synthesized in supercritical carbon dioxide from tungsten hexacarbonyl at 150 °C and 400 bar in the presence of oxygen (partial pressure of 15 bar). The supercritical fluid is a solvent for the precursor (i.e., this is a sc solvothermal synthesis route), whereas the admixed gaseous oxygen serves as an oxidizer, promoting thermal decomposition of the precursor. During the substrate-free synthesis, 200–500 nm aggregates are formed. They consist of smaller grains having the size of about 100 nm. Therefore, a certain structural hierarchy is detected. The electrochemical activity of the as-synthesized particulate material is pronouncedly increasing during both potential cycling and exposure in an aqueous aerated electrolyte. After such a hydration/oxidation process, the electrochemical response of the material shows rather fast and reversible recharging of the entire tungsten-containing phase. This is an indication of facilitated proton transport in bulk of the tungsten oxide phase synthesized in the supercritical carbon dioxide with subsequent hydration/oxidation. Quite differently, the material synthesized at the same temperature only in compressed oxygen (partial pressure of 15 bar) without any presence of supercritical carbon dioxide is highly crystalline one. It does not demonstrate any significant electrochemical rechargeability; neither is the response improving with hydration/oxidation.

New hybrid materials based on multiwalled carbon nanotubes (MWCNTs) with a nonstoichiometric tungsten carbide coating (WC1 –x/MWCNTs) were synthesized by metalorganic chemical vapor deposition with tungsten hexacarbonyl used as a precursor. The mass ratio of precursors was varied to obtain nonstoichiometric tungsten carbide coatings of different morphologies ranging from spatially separated nanoparticles to a uniform ~300-nm-thick coating with a granular structure.

We report nanostructured tungsten oxide (WO) cauliflowers for the first time that are fabricated onto silica glass substrate at 400 °C by aerosol assisted chemical vapor deposition using tungsten hexacarbonyl and multiwalled CNTs in toluene. The deposited films are characterized by Scanning electron microscopy, Energy dispersive x-ray spectroscopy, X-ray diffractometry, Fourier transform infrared and UV–VIS spectroscopy and four-point probe for microstructural, optical and electrical properties. Surface morphology exhibits the growth of nanocauliflowers followed by the aggregation of spherical nanoparticles with high angle grain boundaries. Structural information reveals the transformation of triclinic to tetragonal phase with preferential switching from (0 2 0) to (0 0 1) plane having signatures of W-O-W symmetric vibration between (700cm -1 and 900 cm −1 , somewhat perturbed by the addition of doping. In additions, films show inconsistent variation in electrical resistivity (15–10 9 ) Ω-cm due to agglomeration of MWCNTs at grain boundaries and appearance of “nanocracks” due to ionic radii mismatch of tungsten and CNTs at higher doping ratios. Black color films present decrease in optical transmittance for range of 300–400 nm attributed to trapping sites and defects generated due to incorporation of multiwalled CNTs. The splitting of Fermi level as a result of incorporation of MWCNTs caused the increase of band gap energy in range of 3.18 eV, useful in tungsten oxide based new material system which can act as the light harvesting material and energy storage simultaneously.

The 2D transition metal dichalcogenide (TMDC) tungsten disulfide (WS2) has attracted great interest due to its unique properties and prospects for future (opto)electronics. However, compared to molybdenum disulfide (MoS2), the development of a reproducible and scalable deposition process for 2D WS2 has not advanced very far yet. Here, we report on the systematic investigation of 2D WS2 growth on hydrogen (H2)-desorbed sapphire (0001) substrates using a hydrogen sulfide (H2S)-free metal-organic vapor phase epitaxy (MOVPE) process in a commercial AIXTRON planetary hot-wall reactor in 10 × 2” configuration. Tungsten hexacarbonyl (WCO, 99.9 %) and di-tert-butyl sulfide (DTBS, 99.9999 %) were used as MO sources, nitrogen (N2) was selected as carrier gas for the deposition processes (standard growth time 10 h). In an initial study, the impact of growth temperature on nucleation and growth was investigated and an optimal value of 820 °C was found. The influence of the WCO flow on lateral growth was investigated. The aim was to maximize the edge length of triangular crystals as well as the total surface coverage. Extending gradually the growth time up to 20 h at optimized WCO flow conditions yields fully coalesced WS2 samples without parasitic carbon-related Raman peaks and with only sparse bilayer nucleation. After substrate removal, a fully coalesced WS2 film was implemented into a light-emitting device showing intense red electroluminescence (EL).

Flexible electrochromic organo-tungsten-iron oxide (WFexOyCz) films are rapidly deposited onto flexible (60 Ω/□ polyethylene terephthalate/indium tin oxide; PET/ITO) substrates by a low temperature-atmospheric pressure-plasma polymerization method with an atmospheric pressure plasma jet (APPJ) for a short exposed duration of 48 s. The precursor vapors of tungsten hexacarbonyl [W(CO)6] and biscyclopentadienyl iron [ferrocene; Fe(C5H5)2] are mixed with O2 gases at various gas flow rates, injected into air plasma jet and sprayed onto PET/ITO substrates at room temperature (~23 °C) and at atmospheric pressure (1.013 × 105 Pa). Flexible electrochromic WFexOyCz films are synthesized with a specific addition of oxygen gases with superior lithium electrochromic properties as demonstrated by a potential sweep alternating between −1 V and 2 V at a scan rate of 40 mV/s in a 1 M LiClO4-propylene carbonate electrolyte. With amorphous WFexOyCz films produced with an APPJ by adding oxygen gases at a specific flow rate of 0.5 sccm, a high value in oxygen deficiency up to 0.189 allows more Li+ ions to intercalate into and deintercalate out of the film. Significant coloration and bleaching are proven by the high values in optical transmittance modulation (ΔT) of up to 70.3%, optical density (ΔOD) up to 0.77 and color efficiency (η) up to 61.3 cm2/C, at a wavelength of 800 nm, respectively.

We report on a new hybrid heterojunction gas-sensitive device by combining a molecular material with a metal oxide. WO3 was synthesised via an aerosol-assisted chemical vapour deposition technique from a tungsten hexacarbonyl precursor. Onto an inorganic film, LuPc2 was vacuum evaporated. The morphology of the WO3–LuPc2 hybrid films is dominated by the morphological features of the tungsten oxide film, as shown by scanning electron microscopy and atomic force microscopy. Raman spectroscopy of the device confirms the presence of both materials. The non-linear I–V characteristics demonstrate the existence of an energy barrier at the interface between the inorganic and molecular materials. The interfacial phenomenon was confirmed by means of impedance spectroscopy. Finally, the positive response to ammonia confirms the n-type nature of the charge carriers responsible for the transport properties through the device, in accordance with the n-type conductivity of WO3. This response is fully reversible whatever the relative humidity value in the range 10–70% rh. Even though the current is shifted when the relative humidity decreases, ammonia sensitivity remains almost unchanged (2.5 nA ppm−1) for rh ranging from 30 to 50%. It is worth noting that the present device operates at room temperature with excellent reversibility and stability, showing the lowest limit of detection for ammonia ever reported for this device architecture (250 ppb).

Tungsten disulfide (WS2) thin films are grown on several types of substrates by plasma-enhanced atomic layer deposition (PEALD) technique using tungsten hexacarbonyl [W(CO)6] and H2S plasma at a relatively low temperature of 350 °C. The method delivers polycrystalline WS2 film with (0 0 2) preferential growth and the high quality films could be successfully grown with as low as 30 ALD cycles (corresponding to ∼3 nm of thickness). Density functional theory (DFT) calculation results reveal that both adsorption of W(CO)6 and removal of CO ligand would be facilitated by usage of H2S plasma by generating the different defect sites on the basal plane. The typical self-limiting film growth (growth rate of ∼0.1 nm/cycle), characteristic of ideal ALD, is clearly observed with both the precursor and reactant pulsing time. X-ray diffractometry (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Rutherford backscattering spectrometry (RBS) are performed in details to study the as-grown WS2 film on Si/SiO2 substrate. The analysis results confirm the formation of polycrystalline film, with high purity and well-defined stoichiometry. The as-deposited WS2 films are then explored as an electrode in the field of energy generation as well as energy storage. The films are uniformly and conformally grown on high surface-area 3 dimensional Ni-foam that show excellent activity towards hydrogen evolution reaction (HER). Significantly low overpotential of ∼280 mV is observed at a high operational current density of 100 mA cm−2 during HER in acid electrolyte. In addition, the as-grown films on stainless steel substrate also reveal the stable electrochemical performances in Na-ion battery as an anode with reasonably high areal capacity of ∼44.5 μAh cm−2 at the end of 50 charge-discharge cycles.

We report that the Ni nanocrystals with rod-like and cubic shapes can be prepared in organic solution with the aid of tungsten hexacarbonyl at a relatively low reaction temperature of 150 °C. The prepared Ni nanorods have a fivefold twinned structure with an average diameter of about 11 nm and length varying from several tens of nanometers to 150 nm whereas the obtained Ni nanocubes have an average size of about 19.2 nm. Magnetic measurements indicate that the as-prepared Ni crystals exhibit typical room-temperature ferromagnetic properties. The synthetic strategy revealed in this study provides useful guidelines for the preparation of non-spherical Ni nanocrystals.

Re–W nanoparticles are deposited onto multiwalled carbon nanotubes by the metal organic chemical vapor deposition technique. A mixture of dirhenium decacarbonyl and tungsten hexacarbonyl is used as a precursor. Nanoparticles of hybrid materials are studied by scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray phase analysis. It is found that in a wide range of ratios of the precursors (dirhenium decacarbonyl and tungsten hexacarbonyl), the crystalline component is a Re–W phase, and the morphology of the nanoparticles is the same as that of the nanodendrites.

Tungsten disulfide (WS2) films were grown on c-plane sapphire in a cold-wall gas-source chemical vapor deposition system to ascertain the effect of the chalcogen precursor on the film growth and properties. Tungsten hexacarbonyl (W(CO)6) was used as the tungsten source, and hydrogen sulfide (H2S) and diethyl sulfide (DES-(C2H5)2S) were the chalcogen sources. The film deposition was studied at different temperatures and chalcogen-to-metal ratios to understand the effect of each chalcogen precursor on the film growth rate, thickness, coverage, photoluminescence, and stoichiometry. Larger lateral growth was observed in films grown with H2S than DES. The reduced lateral growth with DES can be attributed to carbon contamination, which also quenches the photoluminescence. Thermodynamic calculations agreed well with the experimental observations, suggesting formation of WS2 with both sulfur precursors and additional formation of carbon when deposition is done using DES.

Tungsten- and nickel-containing coatings have been produced on the surface of synthetic diamond crystals by rotary chemical vapor deposition (RCVD) using tungsten hexacarbonyl, W(CO)6, and nickelocene, Ni(C5H5)2, as gaseous precursors. The thickness, composition, and morphology of the coatings have been shown to depend on the RCVD process duration and reactant concentrations in the vapor phase. The synthetic diamond microcrystals with tungsten- and nickel-containing coatings have been used to produce copper–diamond heat-conducting composites. Powder mixtures containing 50 vol % diamond with a particle size of 50, 100, or 200 μm have been consolidated by spark plasma sintering or hot pressing. It has been shown that the highest relative density (97%) and thermal conductivity (340 W/(m K)) are offered by the composites produced by spark plasma sintering using tungsten carbide-coated 50-μm diamond crystals.

An investigation has been taken on enhancing lithium electrochromic performances of mixed organotungsten oxide (WOyCz)/organotitanium oxide (TiOyCz) films, co-synthesized onto 60 Ω/square flexible polyethylene terephthalate (PET)/indium tin oxide (ITO) substrates by a low temperature plasma polymerization method at various mixed concentrations of precursors tungsten hexacarbonyl W(CO)6 and titanium n-butoxide Ti(C4H9O)4. The plasma polymerized-organo‑tungsten‑titanium oxides (WTixOyCz) films possess notable electrochromic performances while switch tested by a potential sweep from −1 V to 1 V at a scan rate of 50 mV/s and from 1 V to −1 V at a scan rate of −50 mV/s for 200 cycles of reversible Li+ ion intercalation and de-intercalation in a 1 M LiClO4-PC electrolyte, still after bended 360o around a 2.5 cm diameter rod for 1000 cycles. Optical modulation (ΔT) of 74.8% for WOyCz films at a wavelength of 850 nm is appreciably progressed of up to 82.7% for WTixOyCz films as co-deposited by a low temperature plasma polymerization method.

The reaction of the three-mercury anticrown (o-C6F4Hg)3 (1) with tungsten hexacarbonyl in CH2Cl2 at 20 °C in the dark affords the complex {[(o-C6F4Hg)3]2[W(CO)6]} (2) containing two anticrown molecules per W(CO)6 molecule. According to the X-ray diffraction data, two carbonyl groups of W(CO)6 are involved in the formation of 2, each of these carbonyl groups being coordinated via the oxygen atom to a single mercury center of one of the two molecules 1. The formation of the complex is accompanied by a shift of ν(CO) bands in the IR spectrum with respect to the corresponding bands of the starting W(CO)6.

A phenanthroline-based ligand L1 ((((1,10-phenanthrolin-5-yl)imino)methyl)-6-methoxyphenol) was synthesized and reacted with chromium, molybdenum, and tungsten hexacarbonyl to form ultraviolet (UV) activable photoCORMs C1, M1, and T1, respectively. All compounds were characterized via IR, 1H-NMR, 13C-NMR, and CHN elemental analyses, and the X-ray crystal structures of L1 and M1 were determined. The half-life of the photoCORMs decreased with an increasing concentration and the rate of CO release increased in the order of T1

The hydrodearomatization and hydrodesulfurization of the coking resin fraction (below 360°C) in the presence of in situ synthesized Ni–W–S catalysts are studied using tungsten hexacarbonyl W(CO)6 and nickel(II) 2-ethylhexanoate Ni(C7H15COO)2 oil-soluble salts at a molar ratio of W: Ni = 1: 2 as precursors for the Ni–W–S catalysts. The resulting catalysts are characterized by transmission electron microscopy; the formation of agglomerates of nanoparticles with an average diameter of 100–200 nm is shown. The optimum temperature for the hydrotreating of the coking resin (380°C) is determined.