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Tungstates and molybdates possessing the scheelite- and wolframite-type (if present) structures hold a significant functional value. Their high-pressure phase diagrams are very complicated and controversial, and even some parts have not been characterized yet. In this study, we investigate the sequence of pressure driven structural phase transitions up to 100 GPa in these tungstate and molybdate families via first-principles structure predictions. Based on our structural predictions, it is possible for isostructural tungstates and molybdates to exhibit a phase transition sequence that is either similar or identical. Examples of these compounds are CaWO4, CaMoO4, and CdMoO4, in addition to EuWO4 and EuMoO4. However, the phase transition sequences of some tungstates and molybdates, especially those with different divalent cations, display noteworthy variations, revealing the intricate influence of ionic radii and electronic properties on crystal configurations. To obtain a deeper understanding of the high-pressure phase transition behavior of tungstates and molybdates, we analyze the high-pressure phase diagrams of MgWO4, SrWO4, and CaMoO4, representative examples of wolframite-type tungstate, scheelite-type tungstate, and scheelite-type molybdate, respectively, using x-ray powder diffraction. Our x-ray diffraction experiments and structure predictions consistently verify that the orthorhombic Cmca phase is a high-pressure phase of SrWO4. Structural configurations and mechanical properties of these predicted structures are discussed, and electronic properties are given. This study could have important implications for the fields of seismology and geophysics, as well as the utilization of these materials in various capacities, such as photocatalysts, photoanodes, and phosphors. [ABSTRACT FROM AUTHOR]

A set of Eu3+-doped molybdates, Y2−xEuxMo3O12 (x = 0.04; 0.16; 0.2; 0.4; 0.8; 1; 1.6; 2), was synthesized using a solid-state technique and their properties studied as a function of Eu3+ concentration. X-ray diffraction showed that the replacement of Y3+ with larger Eu3+ resulted in a transformation from orthorhombic (low doping concentrations) through tetragonal (high doping concentrations), reaching monoclinic structure for full replacement in Eu2Mo3O12. The intensity of typical Eu3+ red emission slightly increases in the orthorhombic structure then rises significantly with dopant concentration and has the highest value for the tetragonal Y2Mo3O12:80mol% Eu3+. Further, the complete substitution of Y3+ with Eu3+ in the case of monoclinic Eu2Mo3O12 leads to decreased emission intensity. Lifetime follows a similar trend; it is lower in the orthorhombic structure, reaching slightly higher values for the tetragonal structure and showing a strong decrease for monoclinic Eu2Mo3O12. Temperature-sensing properties of the sample with the highest red Eu3+ emission, Y2Mo3O12:80mol% Eu3+, were analyzed by the luminescence intensity ratio method. For the first time, the peak-sharpening algorithm was employed to separate overlapping peaks in luminescence thermometry, in contrast to the peak deconvolution method. The Sr (relative sensitivity) value of 2.8 % K−1 was obtained at room temperature. [ABSTRACT FROM AUTHOR]

The continuous inflammatory response in diabetic skin wounds leads to excessive production of reactive oxygen species, which cause a vicious circle of long-term inflammation. In the therapeutic research of metal nanoenzymes for healing diabetic ulcers, it still faces the challenges in poor nanoenzymes activity and low-efficient therapeutic efficiency. Herein, ultrasmall oxygen-deficient MoO3−X quantum dots were fabricated and employed as nanoenzymes for healing fiabetic ulcers. After PEGylation, PEGylated MoO3−X quantum dots (MoO3−X/PEG) with oxygen vacancies exhibits excellent photothermal, peroxidase/catalase-like activities. In addition, these MoO3−X/PEG showed superior properties in scavenging H2O2 and effectively inhibiting the scavenging of reactive oxygen species. More importantly, such an oxygen-defected MoO3−X/PEG had obvious antibacterial and skin repairing effects on alleviating hypoxia and excessive oxidative stress even in a mouse model of diabetic ulcers, inhibiting proinflammatory cytokines and significantly accelerating the healing of infected wounds, which shows great application potential for promoting wound healing. This work highlights that the developed oxygen defected molybdenum oxide compounds capable of peroxidase-like and catalase-like activities show great application potential for healing diabetes wound. [ABSTRACT FROM AUTHOR]

On the basis of previous work, this paper systematically investigates the influence parameters and leaching kinetics of the ammonia leaching process of molybdenum calcine obtained by microwave roasting. The conditions of the ammonia leaching process of calcined molybdenum were optimized by changing the parameters of ammonia concentration, solid–liquid ratio, and leaching temperature. The results show that, when the concentration of ammonia was 25%, the mass of calcined molybdenum and the volume of ammonia were 1/2 g/ml, the leaching temperature was 75°C, and the leaching time was 60 min, the leaching efficiency of molybdenum can reach 91.74%, and the content of ammonium molybdate in the leaching product was 97.23 wt.%. In the leaching process, MoO3 in the solid phase is dissolved by ammonia to form ammonium molybdate, which conforms to the shrinking core model. The activation energy of the reaction is 57.8 kJ/mol and the rate control step is determined by the mixed model of chemical reaction and product layer diffusion. The apparent rate equation is expressed as: 1 3 ln 1 - x + 1 - x - 1 3 - 1 = 14.97 ω ammonia 2.004 (L / S) - 2.44 e - 57800 RT t . [ABSTRACT FROM AUTHOR]

Electrochemical nitrate reduction (NO3−RR) has been recognized as a promising strategy for sustainable ammonia (NH3) production due to its environmental friendliness and economical nature. However, the NO3−RR reaction involves an eight-electron coupled proton transfer process with many by-products and low Faraday efficiency. In this work, a molybdenum oxide (MoOx)-decorated titanium dioxide nanotube on Ti foil (Mo/TiO2) was prepared by means of an electrodeposition and calcination process. The structure of MoOx can be controlled by regulating the concentration of molybdate during the electrodeposition process, which can further influence the electron transfer from Ti to Mo atoms, and enhance the binding energy of intermediate species in NO3−RR. The optimized Mo/TiO2-M with more Mo(IV) sites exhibited a better activity for NO3−RR. The Mo/TiO2-M electrode delivered a NH3 yield of 5.18 mg h−1 cm−2 at −1.7 V vs. Ag/AgCl, and exhibited a Faraday efficiency of 88.05% at −1.4 V vs. Ag/AgCl. In addition, the cycling test demonstrated that the Mo/TiO2-M electrode possessed a good stability. This work not only provides an attractive electrode material, but also offers new insights into the rational design of catalysts for NO3−RR. [ABSTRACT FROM AUTHOR]

Wearing appropriate personal protective equipment (PPE) for spraying pesticides is one of the methods to reduce dermal exposure to toxic pesticides. The main issues with such PPEs are comfortability and durable functionality. These issues were addressed by developing a bi-layer fabric treated with functionalized iron molybdate (Fe2(MoO4)3) nanoparticles (NPs). Three structures of bi-layer fabrics were developed to get the most comfortable fabric one with an upper layer of cotton (1*1 woven) and an underlayer of polyester (3/1 twill weave). The Fe2(MoO4)3 NPs were synthesized and functionalized with two silanes, i.e., Octadecyltrimethoxysilane and 1,2 Bis(triethoxysilyl)ethane. Fourier transform-infrared spectroscopy and thermogravimetric analysis were done to confirm the binding of silanes with NPs. Functionalized Fe2(MoO4)3 NPs were coated on selected fabric by dip-dry coating, and surface topography was assessed by Scanning Electron Microscopy (SEM). The water contact angle of 151° was exhibited by modified fabric. The photocatalysis of Benzoepin (C9H6Cl6O3S) by Fe2(MoO4)3 NPs under visible light was 75%. The UPF values obtained were 55 and 50 before and after washing, respectively. The developed superhydrophobic fabric could be efficiently used for durable pesticide-resistant clothing because the pesticide would not be adsorbed/absorbed by the fabric. If absorbed it could be possibly degraded by Fe2(MoO4)3 NPs rescuing the wearer from the hazardous effects of pesticides as well as UV rays. [ABSTRACT FROM AUTHOR]

The binary heterostructured semiconducting visible light photocatalyst of the iron-doped graphitic carbon nitride/bismuth molybdate (Fe-g-C3N4/Bi2MoO6) composite was prepared by coupling with Fe-doped g-C3N4 and Bi2MoO6 particles. In the present study, a comparison of structural characteristics, optical properties, and photocatalytic degradation efficiency and activity between Fe-doped g-C3N4 particles, Bi2MoO6 particles, and Fe-g-C3N4/Bi2MoO6 composite was investigated. The results of X-ray diffraction (XRD) examination indicate that the hydrothermal Bi2MoO6 particles have a single orthorhombic phase and Fourier transform infrared (FTIR) spectroscopy analysis confirms the formation of Fe-doped g-C3N4. The optical bandgaps of the Fe-doped g-C3N4 and Bi2MoO6 particles are 2.74 and 2.73 eV, respectively, as estimated from the Taut plots obtained from UV-Vis diffuse reflectance spectroscopy (DRS) spectra. This characteristic indicates that the two semiconductor materials are suitable for absorbing visible light. The transmission electron microscopy (TEM) micrograph reveals the formation of the heterojunction Fe-g-C3N4/Bi2MoO6 composite. The results of photocatalytic degradation revealed that the developed Fe-g-C3N4/Bi2MoO6 composite photocatalyst exhibited significantly better photodegradation performance than the other two single semiconductor photocatalysts. This property can be attributed to the heterostructured nanostructure, which could effectively prevent the recombination of photogenerated carriers (electron–hole pairs) and enhance photocatalytic activity. Furthermore, cycling test showed that the Fe-g-C3N4/Bi2MoO6 heterostructured photocatalyst exhibited good reproducibility and stability for organic dye photodegradation. [ABSTRACT FROM AUTHOR]

Coarse colorless single crystals of lithium lutetium bis[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetragonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry ...) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015). Dalton Trans. 44, 18078–18089.] all atoms were refined with anisotropic displacement parameters. [ABSTRACT FROM AUTHOR]

The rational construction and design of nanostructured materials have a significant impact on the fabrication of high-performance electrode materials, which have attracted considerable interest in an effort to enhance the reliability and efficiency of energy storage devices. In this study, the α-ZnMoO4 nanoparticles were successfully prepared by facile hydrothermal method and the influence of various hydrothermal reaction times on structural, morphological, optical and electrochemical properties were studied. XRD analysis illustrated that α-ZnMoO4 nanoparticles exhibited anorthic crystal structure and the average crystallite size was 42 nm. FESEM images changed from a cubic structure to plate-like structures depending on reaction times. HRTEM analysis revealed that prepared sample showed a plate-like structure and the SAED pattern exhibited a polycrystalline nature. The FTIR spectrum confirmed the presence of vibrational molecules in α-ZnMoO4 nanoparticles. The BET and XPS measurements showed the α-ZnMoO4 nanoparticles were mesoporous and had Zn2+ and Mo6+ oxidation states, respectively. From UV–Visible spectra, a better spectral selectivity region was observed at higher reaction times, and the bandgap values were decreased from 2.73 to 2.48 eV. In photocatalytic studies, RhB dye was used as an organic pollutant and achieved a degradation efficiency of 85 % at an optimized reaction time of 24 h. For electrochemical performances, the prepared electrode material showed maximum specific capacitance values of 165 F g−1 and 110 F g−1 for cyclic voltammetry and galvanoststic charge-discharge analysis, respectively. [ABSTRACT FROM AUTHOR]

Mild steel corrosion is a significant challenge in oil and gas exploitation. Inhibitors are frequently employed to minimize the corrosive impact on mild steel. Mixing corrosion inhibitors is an effective method in reducing the dosage of toxic compounds and expanding the potential applications of inhibitors in NaCl solutions. Herein, a mixed corrosion inhibitor composed of imidazoline (IM), sodium molybdate, and sodium dodecylbenzenesulfonate (SDBS) for mild steel in a 3.5 wt% NaCl solution are investigated by orthogonal experimental design and electrochemical measurement. The imidazoline compound was synthesized and identified using Fourier transform infrared (FTIR) spectroscopy. The inhibitory effect is improved by higher concentrations of sodium molybdate and is further enhanced with the addition of 10 mg/L of SDBS. The electrochemical impedance spectroscopy indicates that the combination of IM (100 mg/L), sodium molybdate (50 mg/L), and SDBS (100 mg/L) results in excellent performance with electrochemical impedance (1.8 kohm·cm2). The mild steel surfaces after electrochemical measurement were analyzed using scanning electron microscopy (SEM). The information can contribute to the development of corrosion inhibitors with high performance or to understand the influence of mixing inhibitors on corrosion processes of mild steels. [ABSTRACT FROM AUTHOR]

Coarse colorless single crystals of lithium lutetium bis[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetragonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry ...) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015). Dalton Trans. 44, 18078–18089.] all atoms were refined with anisotropic displacement parameters. [ABSTRACT FROM AUTHOR]

The exceptional electronic structure of rare earth molybdates renders them highly suitable for applications in photocatalysis and photoluminescence. However, currently available methods for preparing rare earth molybdates suffer from drawbacks such as inefficient yields, prolonged synthesis duration and high sintering temperatures. Here we present a novel molten salt method that facilitates rapid and high-throughput preparation of rare earth molybdate materials. This method achieved a yield of 99% for the synthesis of rare earth molybdate within a 5 h duration. An investigation into the structural and morphological characteristics of synthetic rare earth molybdate was conducted. The photocatalytic activity of Nd 6 MoO 12 and Ln 2 MoO 6 (Ln = La, Nd, Sm, Eu, and Gd) for Methylene blue degradation demonstrates their effective functional applications in the field of photocatalysis. The fluorescence properties of Sm3+/Eu3+-doped Gd 2 MoO 6 demonstrate their potential applications in white light emitting diodes. These studies provide a new path to realize the synthesis of rare earth molybdate functional materials in a rapid and high-throughput manner. [Display omitted] [ABSTRACT FROM AUTHOR]

We developed a rapid method of total phosphorus (TP) determination in fresh water by optimizing the volumes and concentrations of the oxidant (potassium persulfate), reductant (ascorbic acid), and colorant (molybdate + antimony potassium tartrate). Instead of a UV spectrophotometer, as used in the national standard method (GB 11893-89), we used the iMark Microplate Absorbance Reader to measure the absorbance. The principle of TP determination was identical to that of the national standard method as the water sample was digested under a neutral condition and phosphorus was oxidized to orthophosphate and colored to measure absorbance. In the developed method, we adjusted the volumes of the oxidant and reductant to 80 µL and 0.1 g/mL, respectively, and the concentration of the colorant to 31.00 + 0.32 mol/mL. The water samples collected from Lake Taihu in Maoming, Guangdong, China, were used in the experiment. The feasibility and applicability of the developed method were validated by determining TP in freshwater samples. The results showed that the developed method has excellent accuracy and precision compared with the national standard method. In addition, the national standard method was simplified in terms of the digestion and determination of TP, whereby the volume of chemical reagents and the determination time were reduced. The efficiency of TP determination was improved such that the developed method can be used for monitoring water quality to prevent environmental problems. [ABSTRACT FROM AUTHOR]

Coarse colorless single crystals of lithium lutetium bis[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetragonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry 4) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015). Dalton Trans. 44, 18078-18089.] all atoms were refined with anisotropic displacement parameters. [ABSTRACT FROM AUTHOR]

There have been few reports on the characterization of molybdate and tungstate species in pure water using ESI–MS. Hexameric molybdate anions were reported to be unstable in neutral solution, but to exist in acidic solutions. The monomolybdate anion was found to be stable in pure aqueous solution in the form of [HMoO4]−. Monomeric tungstate was observed as [WO4]2− and [HWO4]− in acidic solution. At low pH, [Mo4O13]2−, [HMo4O13]− and [HW3O10]− were the main molecular species observed. At high pH, hydrolyzed [HMoO4]− and [HWO4]− were detected by mass spectometer. When silicic acid was added to the molybdate solution, [SiMo12O40]4− and [HSiMo12O40]3− were formed from the tetrameric molybdate anion. In addition, monomeric, trimeric, hexameric, heptameric, undecameric and dodecameric polyoxomolybdates were detected in the supernatant solution by ESI mass spectrometry. When silicic acid was added to a tungstate solution, [HSiW12O40]3−, composed of the trimeric tungstate anion was detected. In addition, two pentameric polyoxotungstates as well as tetrameric, hexameric and heptameric polyoxotungstates were present in the supernatant solution, while no monomer or dimer was detected. [ABSTRACT FROM AUTHOR]

Coarse colorless single crystals of lithium lutetium bis[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetragonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry 4) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015). Dalton Trans. 44, 18078-18089.] all atoms were refined with anisotropic displacement parameters. [ABSTRACT FROM AUTHOR]

Rare-earth molybdenum-containing oxides of the nominal composition LixNd Mo3O (x = 0, 0.05, 0.15, 0.25) with a fluorite-related structure have been obtained for the first time as single crystals grown from flux and by solid-phase synthesis in air in the form of polycrystalline samples. The new phases are characterized using X-ray diffraction analysis, simultaneous thermal analysis, and impedance spectroscopy. X-ray diffraction analysis showed that lithium atoms are localized near the positions of rare-earth cations. The chemical formula of the investigated single crystal is Li0.216Nd4.784Mo3O . The low lithium content did not affect significantly the ability of the studied phases to dissociative absorption of water but led to a decrease in the total conductivity of LixNd Mo3O lithium ceramics. [ABSTRACT FROM AUTHOR]

Identifying and quantifying accessible nutrients in the soil are critical in agriculture since plants require particular amounts of micro and macronutrients to grow successfully. However, there is no well-defined method for quantifying macronutrients in the field at present. In this work, chitosan and chitosan-molybdate membranes were deposited onto stainless steel (SS) and carbon (C) substrates and evaluated as promising candidates for the quantification of phosphorous species available in cultivated soil. The membranes were morphologically and structurally studied by atomic force microscopy and infrared spectroscopy to determine their appearance, roughness, and chemical conformation. Electrochemical impedance spectroscopy was the electrochemical tool used to evaluate the quantification capacity of phosphorus species of the membrane-based electrodes; it was found that the chitosan-molybdate membranes deposited onto the SS/C interface presented the best performance when the electrodes change in charge transfer resistance and chemical capacitance were measured as a function of the concentration of phosphorus species available in a synthetic sample. Thus, based on the presented results, chitosan biosensors have shown the capability of attracting ionic species, which contributes to the minimization of preference zones on the surface of a sensing electrode. [ABSTRACT FROM AUTHOR]

Structural, optical and photoluminescent properties of La2−xPrx(MoO4)3 phosphors with different doping concentrations of Pr3+, synthesized by conventional solid-state and solution combustion routes were studied. X-ray diffraction studies of compounds synthesized through conventional solid-state ceramic route confirm that all samples crystallized in monoclinic La2(MoO4)3 structure with c2/c space group, while combustion synthesized compounds show the existence of two different crystal environments. Analysis of UV–visible diffuse reflectance spectra (DRS) shows characteristics of absorption bands in blue and red regions for Pr3+ substituted La2(MoO4)3 samples, synthesized by both methods. The calculated band gap from the DR spectrum showed an inverse dependence with Pr3+ doping concentration for solid-state synthesized La2−xPrx(MoO4)3 samples, while for combustion synthesized La2−xPrx(MoO4)3 compounds the variation of band gap with concentration is not monotonous. The photoluminescence emission spectrum of blue excited La2−xPrx(MoO4)3 phosphors synthesized by both routes showed similar multicoloured emission bands. Maximum emission intensity was observed for Pr3+ concentration of x = 0.05 in both synthesis methods. The exchange interaction between nearest activator ions leads to concentration quenching of luminescence for solid-state synthesized La2−xPrx(MoO4)3 compounds and dipole–dipole interaction for combustion synthesized La2−xPrx(MoO4)3 compounds. The average emission colour of the blue excited La2−xPrx(MoO4)3 phosphors lies in the yellow–orange region. The CCT values lie in the warm light region and the luminescence lifetime of 8 µs for red emission peak showed promising applications requiring fast switching response. [ABSTRACT FROM AUTHOR]

Rare-earth molybdenum-containing oxides of the nominal composition LixNd Mo3O (x = 0, 0.05, 0.15, 0.25) with a fluorite-related structure have been obtained for the first time as single crystals grown from flux and by solid-phase synthesis in air in the form of polycrystalline samples. The new phases are characterized using X-ray diffraction analysis, simultaneous thermal analysis, and impedance spectroscopy. X-ray diffraction analysis showed that lithium atoms are localized near the positions of rare-earth cations. The chemical formula of the investigated single crystal is Li0.216Nd4.784Mo3O . The low lithium content did not affect significantly the ability of the studied phases to dissociative absorption of water but led to a decrease in the total conductivity of LixNd Mo3O lithium ceramics. [ABSTRACT FROM AUTHOR]

Coarse colorless single crystals of lithium lutetium bis[orthomolybdate(VI)], LiLu[MoO4]2, were obtained as a by-product from a reaction aimed at lithium derivatives of lutetium molybdate. The title compound crystallizes in the scheelite structure type (tetragonal, space group I41/a) with two formula units per unit cell. The Wyckoff position 4b (site symmetry \overline{4}) comprises a mixed occupancy of Li+ and Lu3+ cations in a 1:1 ratio. In comparison with a previous powder X-ray study [Cheng et al. (2015). Dalton Trans. 44, 18078–18089.] all atoms were refined with anisotropic displacement parameters.

This article discusses the preparation of radiopure lithium carbonate powder for low-background research, specifically for the AMoRE-II experiment. The desired radiopurity for the lithium powder is specified, and commercially available powders were found to be unsuitable. A special purification technology was developed to remove contamination from the powder. The article provides details on the analysis results, decontamination efficiency, and purification methods used. The authors are continuing to explore new purification methods to achieve the desired purity for crystal synthesis. The paper was reviewed by researchers from Brookhaven National Laboratory in the United States and Gazi University in Turkey, and edited by a researcher from University College London in the United Kingdom. [Extracted from the article]

In the last few decades, nanoparticles have been a prominent topic in various fields, particularly in agriculture, due to their unique physicochemical properties. Herein, molybdenum copper lindgrenite Cu3(MoO4)2(OH)2 (CM) nanoflakes (NFs) are synthesized by a one-step reaction involving α-MoO3 and CuCO3⋅Cu(OH)2⋅xH2O solution at low temperature for large scale industrial production and developed as an effective antifungal agent for the oilseed rape. This synthetic method demonstrates great potential for industrial applications. Infrared spectroscopy and X-ray diffraction (XRD) results reveal that CM samples exhibit a pure monoclinic structure. TG and DSC results show the thermal stable properties. It can undergo a phase transition form copper molybdate (Cu3Mo2O9) at about 300 °C. Then Cu3Mo2O9 nanoparticles decompose into at CuO and MoO3 at 791 °C. The morphology of CM powder is mainly composed of uniformly distributed parallelogram-shaped nanoflakes with an average thickness of about 30 nm. Moreover, the binding energy of CM NFs is measured to be 2.8 eV. To assess the antifungal properties of these materials, both laboratory and outdoor experiments are conducted. In the pour plate test, the minimum inhibitory concentration (MIC) of CM NFs against Sclerotinia sclerotiorum (S. sclerotiorum) is determined to be 100 ppm, and the zone of inhibiting S. sclerotiorum is 14 mm. When the concentration is above 100 nm, the change rate of the hyphae circle slows down a little and begins to decrease until to 200 ppm. According to the aforementioned findings, the antifungal effects of a nano CM NFs solution are assessed at different concentrations (0 ppm (clear water), 40 ppm, and 80 ppm) on the growth of oilseed rape in an outdoor setting. The results indicate that the application of CM NFs led to significant inhibition of S. sclerotiorum. Specifically, when the nano CM solution was sprayed once at the initial flowering stage at a concentration of 80 ppm, S. sclerotiorum growth was inhibited by approximately 34%. Similarly, when the solution was sprayed once at the initial flowering stage and once at the rape pod stage, using a concentration of 40 ppm, a similar level of inhibition was achieved. These outcomes show that CM NFs possess the ability to bind with more metal ions due to their larger specific surface area. Additionally, their semiconductor physical properties enable the generation of reactive oxygen species (ROS). Therefore, CM NFs hold great potential for widespread application in antifungal products. [ABSTRACT FROM AUTHOR]

Thermal behavior of vergasovaite, ideally Cu3O(SO4)(MoO4), and its synthetic analog has been studied by high-temperature single-crystal X-ray diffraction in the temperature range of 300–1100 K. According to EMPA results, the empirical formulas are (Cu2.36Zn0.61)Σ2.97O[(Mo0.91S0.08V0.04)Σ1.03O4](SO4) for vergasovaite and Cu2.97O[(Mo0.92S0.09)Σ1.01O4](SO4) for its synthetic analog. The mineral is stable up to 950 ± 15 K; at 975 K, the unit-cell parameters and volume increase abruptly due to topotactic transformation of vergasovaite to cupromolybdite, Cu3O(MoO4)2. The transformation is accompanied by loss of sulfur (and excess copper) without destruction of the crystal. The thermal expansion of the vergasovaite structure is strongly anisotropic, being minimal along the [O2Cu6]8+ chains comprised of vertex-sharing OCu4 tetrahedra. This peculiar thermal behavior can be explained by the anisotropy of bond-length evolution in the Cu1O6 and Cu3O6 octahedra and the flexibility of the S-O-Cu and Mo-O-Cu bond angles. Synthetic Zn- and V-free analogs demonstrate negative thermal expansion at 425–625 K and melt at as low temperature as 700 K with no indication of transformation or recrystallization at least below 1200 K. The topotactic transformation observed in vergasovaite may have important implications for the design of novel materials and for understanding the alteration processes of copper minerals. [ABSTRACT FROM AUTHOR]

Novel Raman crystals can significantly help to expand the available laser wavelength bands and effectively promote the development of laser technology. Bismuth molybdate and tungstate mixed crystals, Bi2Mo2.6W0.4O12 (BMO), with a scheelite crystal structure, are found to have superior Raman gain characteristics. Large-sized single crystals of BMO with dimensions up to 83 mm × 65 mm × 55 mm were sucessfully grown in the Bi2O3–MoO3 hybrid-flux solutions by the top-seeded solution growth (TSSG) method. Spontaneous polarized Raman spectra of BMO crystals were systematically measured and analyzed based on microvibrations of the composing Raman active ionic groups. Through comparison, it was found that BMO crystals had a large Raman gain coefficient, 1.1 times that of the mostly used YVO4 crystals. Besides, under the pump of a 1064 nm laser, a first-order Raman laser at 1176 nm, and dual-wavelength of both first-order and second-order at 1315 nm, were achieved under the Y(ZZ)Y and Y(XX)Y configurations, respectively. A maximum output power of 1.12 mW, corresponding to an optical-to-optical conversion efficiency of 15.6%, was successfully achieved. This work provides systematic analysis of the polarized Raman spectra of BMO crystals and reveals their great application prospects as novel Raman laser crystals. [ABSTRACT FROM AUTHOR]

Tartrazine (TRZ) is a synthetic food dye considered noxious to human health and a toxic environmental contaminant owing to the presence of a harmful azo group (–N＝ N–) in its chemical structure. The global necessity to prevent food contamination has led scientific researchers to develop disposable sensing platforms. This study aims to integrate nanotechnology with electrochemistry to fabricate a disposable screen-printed carbon electrode (SPCE) with a nanocomposite composed of gadolinium molybdate (Gd2MoO6) nanoflowers decorated on an enmeshed matrix of acid-functionalized carbon nanofibers (f-CNF). The hierarchal arrangement of distinct components in the nanocomposite is promoted by synergism through the formation of a hybrid heterojunction. This heterojunction in the electrode modifier activates the electrode to sense TRZ with a remarkable limit of detection (0.8 nmol L−1) and quantification (2 nmol L−1) over a broad linear range of 0.025 μM to 216.45 μM. Furthermore, the functional sensing ability of the proposed sensor was analyzed in various commercial food products. [ABSTRACT FROM AUTHOR]

The title compound dipotassium gadolinium(III) phosphate(V) molybdate(VI), K2Gd(PO4)(MoO4), was synthesized from a high-temperature melt starting from GdF3 as a source of gadolinium. Its structure is isotypic with other MI2MIII(MVIO4)(PO4) compounds, where MI = Na, K or Cs, and MIII = rareearth cation, MVI = Mo orW. The three-dimensional framework is built up from [Gd(PO4)(MoO4)] anionic sheets, which are organized by adhesion of [GdPO4] layers and [MoO4] tetrahedra stacked above and below these layers. The interstitial space is occupied by K cations having eightfold oxygen coordination. The polyhedron of GdO8 was estimated to be a triangular dodecahedron by the continuous shape measurement method. [ABSTRACT FROM AUTHOR]

The title compound dipotassium gadolinium(III) phosphate(V) molybdate(VI), K2Gd(PO4)(MoO4), was synthesized from a high-temperature melt starting from GdF3 as a source of gadolinium. Its structure is isotypic with other MI2MIII(MVIO4)(PO4) compounds, where MI = Na, K or Cs, and MIII = rareearth cation, MVI = Mo orW. The three-dimensional framework is built up from [Gd(PO4)(MoO4)] anionic sheets, which are organized by adhesion of [GdPO4] layers and [MoO4] tetrahedra stacked above and below these layers. The interstitial space is occupied by K cations having eightfold oxygen coordination. The polyhedron of GdO8 was estimated to be a triangular dodecahedron by the continuous shape measurement method. [ABSTRACT FROM AUTHOR]

By targeted introduction of 6-nitrobenzimidazole into polymolybdate, two new polymolybdate-based copper-organic complexes were successfully synthesized, namely {Cu2(6-nbm)4[β-Mo8O26](H2O)2}·(6-nbm)2·4H2O (1) and H2{Cu2(6-nbm)4[TeMo6O24](H2O)4}·(6-nbm)2·4H2O (2) (6-nbm = 6-nitrobenzimidazole), and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy and powder X-ray diffraction (PXRD). Complexes 1 and 2 are both one-dimensional (1D) chain structures, in which 6-nbm hangs on the 1D chain in a monodentate coordination mode, appearing with a butterfly-like configuration. Complexes 1 and 2 both display bifunctional electrocatalytic activity toward the reduction of KNO2, as well as the oxidation of ascorbic acid (AA). The title complexes, used to prepare bulk-modified carbon paste electrodes (1–CPE and 2–CPE), can be used as electrochemical sensors, which show lower detection limit, good selectivity and anti-interference ability. In addition, the carbon cloth-based electrode modified with complex 1 (1–CC) exhibits ideal capacitance and long-term cycle stability, indicating that complex 1 can be a potential candidate for a pseudocapacitive material. In addition, complexes 1 and 2 show catalytic activity for the CO2 reduction reaction. [ABSTRACT FROM AUTHOR]

Olefins are important feedstocks in the production of fuels and many useful chemicals. Herein, cobalt molybdate (CoMoO4) was first synthesized by an environmentally friendly evaporation method and it exhibited excellent catalytic performance for the production of olefins by the selective hydrodeoxygenation (HDO) of ketones that can be derived from lignocellulose. On the basis of the characterization results, the excellent catalytic performance of CoMoO4 was attributed to its larger specific surface area, better pore structure, higher oxygen vacancy (or Mo5+ species) concentration, higher acid strength and higher concentration of acid sites. Under the optimized reaction conditions, 4-heptanone was almost completely converted to heptene, and a high carbon yield of heptene (96%) was achieved over a CoMoO4 catalyst with a Co/Mo atomic ratio of 0.8 (denoted as CoMoO4-0.8). The CoMoO4 catalyst is also active for the selective HDO of other lignocellulosic ketones (such as acetone, butanone, 2-pentanone, 3-pentanone, cyclopentanone, cyclohexanone, 5-nonanone and acetophenone) to their corresponding olefins. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) represent crucial intermediates in the formation of insoluble metal oxides from soluble metal ions, however, the rapid hydrolysis‐condensation kinetics of MoVI or WVI makes the direct characterization of coexisted molecular species in a given medium extremely difficult. Silver nanoclusters have shown versatile capacity to encapsulate diverse POMs, which provides an alternative scene to appreciate landscape of POMs in atomic precision. Here, we report a thiacalix[4]arene protected silver nanocluster (Ag72b) that simultaneously encapsulates three kinds of molybdates (MoO42−, Mo6O228− and Mo7O258−) in situ transformed from classic Lindqvist Mo6O192−, providing more deep understanding on the structural diversity and condensation growth route of POMs in solution. Ag72b is the first silver nanocluster trapping so many kinds of molybdates, which in turn exert collective template effect to aggregate silver atoms into a nanocluster. The post‐reaction of Ag72b with AgOAc or PhCOOAg produces a discrete Ag24 nanocluster (Ag24a) or an Ag28 nanocluster based 1D chain structure (Ag28a), respectively. Moreover, the post‐synthesized Ag28a can be utilized as potential ignition material for further application. This work not only provides an important model for unlocking dynamic features of POMs at atom‐precise level but also pioneers a promising approach to synthesize silver nanoclusters from known to unknown. [ABSTRACT FROM AUTHOR]

The synthesis of ammonia via electrochemical nitrogen reduction reaction (NRR) provides an attractive alternative approach to the traditional Haber-Bosch process. In this regard, a one-step hydrothermal method was adopted to synthesize a bimetallic oxide， ferric molybdate (Fe 2 (MoO 4) 3), coated with carbon black on the surface (denoted as Fe 2 (MoO 4) 3 /C). The carbon black coating minimizes aggregation of Fe 2 (MoO 4) 3 , leading to increased electrochemical active sites for NRR. Additionally, this coating improves the electrical conductivity of Fe 2 (MoO 4) 3 thereby accelerating electron transfer between carbon black and Fe 2 (MoO 4) 3 , which is beneficial to charge transfer and enlarge the electrochemical active surface areas. At a potential of −0.4 V RHE (vs. reversible hydrogen electrode, RHE), the ammonia yield achieved was up to 51.76 μg h−1 mg cat −1, with a Faradaic efficiency of 90.63% at −0.35V RHE. Impressively, this electrocatalyst exhibited excellent cycle stability and durability. Fe 2 (MoO 4) 3 /C electrocatalyst was prepared via a one-step hydrothermal method and demonstrated to be a highly efficient non-noble metal catalyst towards electrocatalytic NRR. The obtained Fe 2 (MoO 4) 3 /C gives an NH 3 yield rate of 51.76 μg h−1 mg cat −1 at −0.4 V RHE and FE of 90.63% at −0.35 V RHE in 0.1 M Na 2 SO 4 solution, which is much higher than that of the contrast Fe 2 (MoO 4) 3 sample. [Display omitted] • Fe 2 (MoO 4) 3 /C composite electrocatalyst is reasonably designed and synthesized. • Fe 2 (MoO 4) 3 /C shows excellent stability for electrocatalytic nitrogen reduction in 0.1 M Na 2 SO 4 electrolyte. • The excellent NRR activities of Fe 2 (MoO 4) 3 /C own to the enhanced electron transfer and enlarged ECSA. [ABSTRACT FROM AUTHOR]

This research investigates the hydrometallurgical processing of molybdenum middlings extracted from copper-molybdenum ore in the Shatyrkul-Zhaysan cluster in Kazakhstan. A molybdenum intermediate obtained after selective flotation of the copper-molybdenum concentrate was used, with a recovery of 0.07%, a molybdenum content of 22.23% and an extraction of 74.91%. The mineralogical analysis shows molybdenite and chalcopyrite as the main minerals. In experiments, atmospheric leaching with nitric acid in single-stage and two-stage countercurrent processes was investigated to optimize molybdenum extraction and reduce acid consumption. The optimum conditions obtained were: 300 g/L nitric acid, 100 g/L sulfuric acid, 90°C temperature and 2 hours leaching time in the single-stage leaching, which extracted 98.8% molybdenum. The two-stage leaching under optimized conditions allows the extraction of 94.3% molybdenum in solutions with lower residual acidity (0.89 g-eq/L) and redox potential (550 mV) without reducing the extraction of valuable component. Molybdenum extraction reaches 94.3% in the subsequent solvent extraction stage from two-stage leaching solutions. The final product, calcium molybdate with a molybdenum content of 46.83%, meets commercial grade specifications. This research demonstrates an effective process for hydrometallurgical production of commercial grade calcium molybdenite from copper-molybdenum ore, with high molybdenum recovery, reduced acid consumption through two-stage leaching, and minimal hazardous discharges. [ABSTRACT FROM AUTHOR]

Cerium molybdate and aluminum molybdate were synthesized by precipitation at controlled pH. The inhibitory properties of these solids on the corrosion process of aluminum in near‐neutral aqueous NaCl solutions were studied. Potentiodynamic polarization curves showed that both molybdates act as mixed‐type inhibitors. This is due to molybdate anion acts as an anodic inhibitor, while the trivalent cations Ce(III) and Al(III) have an inhibitory effect on the cathodic reaction. Linear polarization tests demonstrated a large increase in polarization resistance when these solids are added, resulting in an inhibition efficiency of 97% in both cases. Scanning electron microscopy and X‐ray energy dispersive microanalysis of the exposed surfaces revealed the formation of compact protective films rich in Mo and with no detectable Cl levels. [ABSTRACT FROM AUTHOR]

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The influence of the charge treatment by ultrahigh dilution (UHD) technology on oxide single crystals grown by the Czochralski technique was studied for monoclinic MgMoO4 crystals doped by 1 at. % of Nd3+ ions. The series of 10 Nd:MgMoO4 crystals was grown from the charges that were subjected to UHD treatment, as well as from the charges treated with two types of control or with no special treatment at all. The grown crystals were studied by X-ray powder diffraction analysis, inductively coupled plasma atomic emission spectroscopy, mass-spectrometry, optical absorption, emission spectroscopy and luminescence kinetic analysis. We found that: (i) wetting of MgO + MoO3 mixture by a water-ethanol solution before calcining leads to some enrichment of the mixture with MoO3, whereas the wetting of the charge after the calcining leads to some enrichment of it with MgO; (ii) congruent melting composition of MgMoO4 crystal is in the field of some MoO3 excess; (iii) the solid-phase solubility of the excess MoO3 in MgMoO4 probably does not depend on temperature, whereas the solid-phase solubility of the excess MgO in MgMoO4 crystal depends on temperature. We suggest that the corresponding solidus line passes through the range of retrograde solubility; (iv) the crystals grown within this range are characterized by the enhanced Nd3+ segregation coefficient between the crystal and the melt (approximately 0.006 versus 0.004); (v) unit cell parameters of MgMoO4 crystal with the excess of MoO3 are larger than those of the crystal of the stoichiometric composition and of the crystal with the excess of MgO; (vi) the shapes of the optical absorption and luminescence spectra of Nd:MgMoO4 crystal do not depend on the charge treatment; (vii) luminescence decay kinetics are single-exponential for all the studied crystals, the luminescence decay time being different for the crystals grown from the charges that underwent different types of treatment; (viii) the luminescence intensity of Nd:MgMoO4 crystal grown from the charge that underwent UHD treatment before calcining (solid-phase synthesis) is reduced by an order of magnitude in comparison with the other studied crystals. [ABSTRACT FROM AUTHOR]

This paper reviews not the largest, but at the same time quite an interesting, group of natural and synthetic uranyl molybdate compounds. Nowadays, nine minerals of U and Mo are known, but the crystal structures have only been reported for five of them. Almost an order of magnitude more (69) synthetic compounds are known. A significant discrepancy in the topological types for natural and synthetic phases is shown, which is most likely due to elevated temperatures of laboratory experiments (up to 1000 °C), while natural phases apparently grow at significantly lower temperatures. At the same time, the prevalence of dense topologies (with edge-sharing interpolyhedral linkage) among natural phases can be noted, which is fully consistent with other recently considered mineral groups. Uranyl molybdates demonstrate several similarities with compounds of other U-bearing groups; however, even topological matches do not lead to the appearance of completely isotypic compounds. Structural complexity calculations confirm, in general, crystal chemical observations. Considering the prevalence of dense structures in which coordination polyhedra of uranium and molybdenum are connected through common edges as well as framework architectures, one can expect a less significant influence of interlayer species on the formation of the crystal structure than the main U-bearing complexes. The more structural complexity of the uranyl molybdate units, the more complex of the entire crystal structure is. In addition, there is a tendency for complexity to increase with increasing density of the complex; the simplest structures are vertex-shared, while the complexity increases with the appearance of common edges. [ABSTRACT FROM AUTHOR]

A set of Eu3+-doped molybdates, Y2−xEuxMo3O12 (x = 0.04; 0.16; 0.2; 0.4; 0.8; 1; 1.6; 2), was synthesized using a solid-state technique and their properties studied as a function of Eu3+ concentration. X-ray diffraction showed that the replacement of Y3+ with larger Eu3+ resulted in a transformation from orthorhombic (low doping concentrations) through tetragonal (high doping concentrations), reaching monoclinic structure for full replacement in Eu2Mo3O12. The intensity of typical Eu3+ red emission slightly increases in the orthorhombic structure then rises significantly with dopant concentration and has the highest value for the tetragonal Y2Mo3O12:80mol% Eu3+. Further, the complete substitution of Y3+ with Eu3+ in the case of monoclinic Eu2Mo3O12 leads to decreased emission intensity. Lifetime follows a similar trend; it is lower in the orthorhombic structure, reaching slightly higher values for the tetragonal structure and showing a strong decrease for monoclinic Eu2Mo3O12. Temperature-sensing properties of the sample with the highest red Eu3+ emission, Y2Mo3O12:80mol% Eu3+, were analyzed by the luminescence intensity ratio method. For the first time, the peak-sharpening algorithm was employed to separate overlapping peaks in luminescence thermometry, in contrast to the peak deconvolution method. The Sr (relative sensitivity) value of 2.8 % K−1 was obtained at room temperature.

Cs2Mo2O7 ⋅ CsI is obtained as a member of the series Cs2Mo2O7 ⋅ CsX with X=Cl, Br, and I from the synthesis of Cs2MoO4 with MoO3 and CsX. At room temperature, the compounds crystallize in the space group P63/mmc with the dimolybdate, [Mo2O7]2−, in a linear and eclipsed conformation. Low temperature Raman spectroscopy and low temperature X‐ray diffraction were used to investigate the effect of the ∞2{CsX} ${_\infty ^2 \{ {\rm{CsX}}\} }$ hetero‐honeycomb lattice on the bridging angle of the dimolybdate. For X=Cl, a phase transition occurs below 150 K (P63/mmc → Cmcm). The phase transition relates to a lock‐in that involves bending of the (Mo−O−Mo) bridge. For the Pearson softer iodide compound, no phase transition is observed down to 4 K; thus, the linear configuration remains stable. Specific heat data and their evaluation in terms of phonon contributions are given. [ABSTRACT FROM AUTHOR]

A simple citric acid (CA)‐ammonium molybdate co‐impregnation method was applied to prepare the Mo‐based MCM‐49 catalyst to ameliorate the dispersion of metallic Mo for methane dehydro‐aromatization reaction (MDA). The newly prepared catalyst has higher crystallinity and maintains the original morphology of zeolite, which proves that the addition of citric acid will not destroy the basic structure of the catalyst. Based on H2‐TPR, UV‐vis, NH3‐TPD and XPS characterization results, it can be corroborated that the introduction of citric acid changes the coordination state of Mo element. Brønsted acid sites can stabilize the monomeric Mo oxide species by increasing MoOx migration into the MCM‐49 zeolite pores channel after calcination, which may affect the distribution of active sites MoCx and thus improve MDA catalytic activity. The experimental results show that the Mo‐based MCM‐49 catalyst with nCA : nMo ratios of 1.0 has higher methane conversion (14.5 %) and aromatics yield (9.8 %). The combination of XPS, TG and Raman tests of the spent catalyst confirms that the newly synthesized catalysts produce less carbon deposition, thus improving the catalytic durability during the MDA reaction. [ABSTRACT FROM AUTHOR]

A mixed metal oxide, ZnMoO 4 has been prepared by the conventional solid-state reaction method, with the help of hydrothermally synthesized solvents of ZnO and MoO 3. The phase purity and surface morphology of the precursors of ZnO and MoO 3 are resolved with the Rietveld refinement and scanning electronic microscopy studies. Structural, morphological, and vibrational modes characterizations associated with the unit cell information of ZnMoO 4 are explained by Rietveld's refined technique of XRD, SEM, and Raman studies, respectively. The anode solvent ZnMoO 4 is subjected to cyclic voltammetry analysis. Hence, the electrochemical impedance spectroscopy (EIS) measurements are recorded between 3.0 and 0.01 V at a scan rate of 0.5 mV s−1 for ZnMoO 4 electrodes as an anode material in LIBs. Here, it has been noticed that the hexagonal-like ZnMoO 4 has high capacity and reasonable cycle stability compared with ordinary ZnMoO 4. An anomalous change in permittivity and tangent loss at T θ =750K in temperature dependent dielectric studies confirm phase transition due to the transformation of molecular groups, MoO 4 (low temperature) triclinic phase into molecular groups, MoO 6 (high temperature) monoclinic phase. The temperature and frequency dependent AC-conductivity at different intervals reveal mechanisms associated with different temperature regions. This study provides an in-depth understanding of the electrical and electrochemical activities of zinc molybdate anode materials in novel applications. [ABSTRACT FROM AUTHOR]

The molybdate-incorporated hydrotalcite-type α-Ni(OH)2 catalysts were prepared by the post-synthesis method. The synthesized catalyst was thoroughly studied using several physicochemical characterization methods. The catalytic activity of the material was studied on biomass model compounds such as anisole hydrotreating and the oxidation of iso-eugenol. The catalyst shows a significant conversion for the anisole hydrotreating in vapour phase conditions, yielding a steady-state conversion of 30% even after 10 h of time-on-stream (TOS). The primary product was benzene, with other products, viz., methyl anisole, methylcyclohexane, and toluene, as minor components. The catalyst also has the potential for iso-eugenol oxidation and shows 76.1% conversion with 75.5% selectivity for vanillin at 100 °C, 5 h. Molybdate-incorporated hydrotalcite-type α-Ni(OH)2 catalysts have the potential for oxidation of iso-eugenol to vanillin in the presence of an oxidant in a liquid phase and hydro-deoxygenation in the vapour phase under a hydrogen atmosphere. [ABSTRACT FROM AUTHOR]

This review provides an analysis of prior research on the oxidation of organic compounds with oxygen as an oxidant in the presence of transition-metal molybdates. The reaction mechanisms suggested for the oxidation of various classes of organic substrates, methods for the synthesis and modification of molybdates, and promising industrial applications of molybdate catalysts are discussed. [ABSTRACT FROM AUTHOR]

A new compound NH4Co2OH(MoO4)2⋅H2O was prepared by precipitation of aqueous solutions of cobalt nitrate and ammonium heptamolybdate at pH = 7.5. The crystal structure was identified by X-ray powder diffraction (XRPD) and Rietveld refinement as a known polymorph of layered molybdates (Φ y) with general formula AT 2OH(MoO4)2⋅H2O (A = NH4+, Na+, K+ and T = Zn2+, Co2+, Cu2+, Ni2+) and refined from a model based on that structure. The lattice parameters were refined with R- 3 space group (148) a = 6.1014(2) Å, b = 6.1014(2) Å, c = 21.826(1) Å, α = 90°, β = 90°, and γ = 120°. [ABSTRACT FROM AUTHOR]

An efficient methodology has been developed for the synthesis of 3,3‐di(indolyl)oxindoles and bis(indolyl)methanes under mild conditions. The efficient condensation reaction of indoles with isatin and aldehyde led to the corresponding derivatives in the presence of silver molybdate (Ag‐PMo12) nanocomposite and aqueous medium. In addition, the silver‐doped catalytic system enables the one‐pot formation of diindolyl derivatives with excellent yields, short reaction times and under environmental benign conditions. [ABSTRACT FROM AUTHOR]

Multistage mass spectrometry experiments, isotope labelling and DFT calculations were used to explore whether selective decarbonylation of formic acid could be mediated by molybdate anions [(MoO3)x(OH)]− (x = 1 and 2) via a formal catalytic cycle involving two steps. In step 1, both molybdate anions undergo gas-phase ion-molecule reactions (IMR) with formic acid to produce the coordinated formates [(MoO3)x(O2CH)]− and H2O. In step 2, both coordinated formates [(MoO3)x(O2CH)]− undergo decarbonylation under collision-induced dissociation (CID) conditions to reform the molybdate anions [(MoO3)x(OH)]− (x = 1 and 2), thus closing a formal catalytic cycle. In the case of [MoO3(O2CH)]− an additional decarboxylation channel also occurs to yield [MoO3(H)]−, which is unreactive towards formic acid. The reaction between [Mo18O3(18OH)]− and formic acid gives rise to [Mo18O3(O2CH)]− highlighting that ligand substitution occurs without 18O/16O exchange between the coordinated 18OH ligand and HC16O2H. The reaction between [(MoO3)x(OD)]− (x = 1 and 2) and DCO2H initially produces [(MoO3)x(OH)]− (x = 1 and 2), indicating that D/H exchange occurs. DFT calculations were carried out to investigate the reaction mechanisms and energetics associated with both steps of the formal catalytic cycle and to better understand the competition between decarbonylation and decarboxylation, which is crucial in developing a selective catalyst. The CO and CO2 loss channels from the monomolybdate anion [MoO3(O2CH)]− have similar barrier heights which is in agreement with experimental results where both fragmentation channels are observed. In contrast, the dimolybdate anion is more selective, since the decarbonylation pathway of [(MoO3)2(O2CH)]− is both kinetically and thermodynamically favoured, which agrees with experimental observations where the CO loss channel is solely observed. [ABSTRACT FROM AUTHOR]

Klebsiella pneumoniae , a facultative anaerobe, relies on acquiring molybdenum to sustain growth in anaerobic conditions, a crucial factor for the pathogen to establish infections within host environments. Molybdenum plays a critical role in pathogenesis as it forms an essential component of cofactors for molybdoenzymes. K. pneumoniae utilizes the ABC (ATP-Binding-Cassette) transporter encoded by the modABC operon for uptake of the group VI elements molybdenum and tungsten. In this study, we determined the X-ray crystal structures of both the molybdenum-free and molybdenum-bound substrate-binding protein (SBP) ModA from Klebsiella pneumoniae to 2.00 Å and 1.77 Å resolution respectively. ModA crystallizes in the space group P222 with a single monomer in one asymmetric unit. The purified protein remained soluble and specifically bound molybdate and tungstate with K d values of 6.3 nM and 5.2 nM, respectively. Tungstate competes with molybdate by binding to ModA, resulting in enhanced antimicrobial activity. These data provide a starting point for structural and functional analyses of molybdate transport in K. pneumoniae. • We determined the 2.0 Å crystal structure of K. pneumoniae ModA. • A molybdate-bound structure reveals the residues required for binding molybdenum. • Molybdate and tungstate bind with similarly high affinity to ModA. • ModA is a potential target for therapeutic intervention using tungstate. [ABSTRACT FROM AUTHOR]

BaMoO4 was obtained via facile mechanochemical synthesis at room temperature and a solid-state reaction. An evaluation of the phase composition and structural and optical properties of BaMoO4 was conducted. The influence of different milling speeds on the preparation of BaMoO4 was explored. A shorter reaction time for the phase formation of BaMoO4 was achieved using a milling speed of 850 rpm. A milling speed of 500 rpm led to partial amorphization of the initial reagents and to prolongation of the synthesis time of up to 3 h of milling time. Solid-state synthesis was performed via heat treatment at 900 °C for 15 h. X-ray diffraction analysis (XRD), infrared (IR) and UV diffuse reflectance (UV-Vis) and photoluminescence (PL) spectroscopy were carried out to characterize the samples. Independently of the method of preparation, the obtained samples had tetragonal symmetry. The average crystallite sizes of all samples, calculated using Scherrer's formula, were in the range of 240 to 1540 Å. IR spectroscopy showed that more distorted structural MoO4 units were formed when the compound was synthesized via a solid-state reaction. The optical band gap energy of the obtained materials was found to decrease from 4.50 to 4.30 eV with increasing crystallite sizes. Green- and blue-light emissions were observed for BaMoO4 phases under excitation wavelengths of 330 and 488 nm. It was established that the intensity of the PL peaks depends on two factors: the symmetry of MoO4 units and the crystallite sizes. [ABSTRACT FROM AUTHOR]

Nano-sized composite ion-exchanger can be applied as an electrochemically switchable ion-exchanger for waste water treatment, especially in the separation of heavy metal ions from the polluted aquatic system. Advanced polyaniline/Ti(IV) iodomolybdate nanocomposite ion-exchanger have been synthesized by in-situ chemical oxidation polymerization shows better ion-exchange capacity than individual inorganic counterpart. The physico-chemical characterization was done by FT-IR, XRD, simultaneous TGA-DTA, SEM, HR-TEM and electrochemical impedance studies. According to impedance/dielectrical study, it has high resistivity in the low-frequency region. The distribution studies and binary separation revealed that the ion-exchange material is highly selective for Pb2+, which is a most important environmental pollutant. Thus, PANI/TIM nanocomposite ion-exchanger can be used for Pb(II) ion-selective membrane for the treatment of aquatic pollutants in future. [ABSTRACT FROM AUTHOR]