Molybdenum Ions Research Articles

Glutathione‐Induced In Situ Michael Addition between Nanoparticles for Pyroptosis and Immunotherapy

AbstractMost tumor treatments will fail when ignoring competition and cooperation between each cancer cell and its microenvironment. Inspired by game theory, therapeutic agents can be introduced to compete for intracellular molecules to disrupt the cooperation between molecules and cells. Biomineralized oxidized (−)‐epigallocatechin‐3‐o‐gallate (EGCG)–molybdenum ion coordination nanoparticles were prepared for disrupting redox equilibria and simultaneously reacting with intracellular GSH in a Michael addition to form large aggregates that can mechanically disrupt endosomal and plasma membranes, stimulating pyroptosis and anti‐tumor immunological responses for versatile inhibition of different types of tumors. This design disrupts the cooperation between molecules and between cancer and immune cells, achieving an optimal payoff in competition and cooperation in cancer therapy.

Inspired by Game Theory: Glutathione-induced in Situ Michael Addition between Nanoparticles for Pyroptosis and Immunotherapy.

As its complexity and genetic instability, most tumor treatments will fail when ignoring competition and cooperation between each cancer cell and its microenvironment. Inspired by game theory, therapeutic agents can be introduced to compete for intracellular molecules to disrupt the cooperation between molecules and cells. Here, we prepare biomineralized oxidized (-)-epigallocatechin-3-o-gallate (EGCG)-molybdenum ion coordination nanoparticles for disrupting redox equilibrium and simultaneously reacting with intracellular GSH via Michael addition to form large aggregations that can mechanically disrupt endosomal and plasma membrane, stimulating pyroptosis and anti-tumor immunological responses for versatile inhibition of different types of tumors. This design disrupts the cooperation between molecules and between cancer and immune cells, gaining optimal payoff in competition and cooperation in cancer therapy.

Mixed-valence molybdenum ion incorporated graphitic carbon nitride with high photocatalytic H2 evolution activity

The graphitic carbon nitride (CN) incorporated with mixed-valence molybdenum ion has been prepared via in-situ copolymerization to improve the photocatalytic H2 evolution performance. The introduced Mo species existed in mixed valence of Mo4+ and Mo2+ state and its content could be tuned by simply adjusting amount of added MoCl5 in the preparation procedure. The incorporated mixed-valence Mo ions contributed to narrowed band gap, increased electron density and elevated electron motion kinetics, resulting in extended visible light response, promoted separation and transportation of photoexcited charge carriers. The obtained CN–Mo photocatalyst with an optimal content of Mo ions (0.41 wt%) exhibited a robust H2 production activity up to 1.44 mmol h−1 g−1, 18 times higher than that of pristine counterpart.

Кинетика растворения триоксида молибдена в щелочной среде

The paper presents experimental study results of the MoO3 powder samples dissolution kinetics in the aqueous ammonia solution at various pH concentrations and values. Molybdenum ions concentration in the filtrate samples was determined spectrophotometrically. Kinetic characteristics were obtained, and kinetic parameters (specific dissolution rate, reaction order with respect to the H+ ion) were calculated. It was established that the dissolution rate was increasing in the ammonia solution concentration range of 0.02--1.26 mol/l, and with the growing pH it passed through the maximum. Taking into account the acid-base equilibria constants, the dissolution process was simulated, and its stage-by-stage nature was established. Fractional reaction order with respect to the H+ ions calculated from the curves plotted in the α--t/t0.5 coordinates (affine transformation method) indicated the adsorption mechanism of dissolution. It was shown that the MoO3 dissolution proceeded with formation of the intermediate adsorption complexes. Due to the HMoO4- low concentration in the MoO3 concentration within the studied pH range by the surface-active particle, on which groups of ions were adsorbed, the MoO4- could be considered. The results obtained are an addition to the data possessed on the molybdenum oxide phase and other transitional metals behavior. They could be applied in the practical applications associated with dissolving molybdenum in the alkaline electrolytes

Synthetic Access to a Framework-Stabilized and Fully Sulfided Analogue of an Anderson Polyoxometalate that is Catalytically Competent for Reduction Reactions

Polyoxometalates (POMs) featuring 7, 12, 18, or more redox-accessible transition metal ions are ubiquitous as selective catalysts, especially for oxidation reactions. The corresponding synthetic and catalytic chemistry of stable, discrete, capping-ligand-free polythiometalates (PTMs), which could be especially attractive for reduction reactions, is much less well developed. Among the challenges are the propensity of PTMs to agglomerate and the tendency for agglomeration to block reactant access of catalyst active sites. Nevertheless, the pervasive presence of transition metal sulfur clusters metalloenzymes or cofactors that catalyze reduction reactions and the justifiable proliferation of studies of two-dimensional (2D) metal-chalcogenides as reduction catalysts point to the promise of well-defined and controllable PTMs as reduction catalysts. Here, we report the fabrication of agglomeration-immune, reactant-accessible, capping-ligand-free CoIIMo6IVS24n- clusters as periodic arrays in a water-stable, hierarchically porous Zr-metal-organic framework (MOF; NU1K) by first installing a disk-like Anderson polyoxometalate, CoIIIMo6VIO24m-, in size-matched micropores where the siting is established via difference electron density (DED) X-ray diffraction (XRD) experiments. Flowing H2S, while heating, reduces molybdenum(VI) ions to Mo(IV) and quantitatively replaces oxygen anions with sulfur anions (S2-, HS-, S22-). DED maps show that MOF-templated POM-to-PTM conversion leaves clusters individually isolated in open-channel-connected micropores. The structure of the immobilized cluster as determined, in part, by X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS) analysis, and pair distribution function (PDF) analysis of total X-ray scattering agrees well with the theoretically simulated structure. PTM@MOF displays both electrocatalytic and photocatalytic competency for hydrogen evolution. Nevertheless, the initially installed PTM appears to be a precatalyst, gaining competency only after the loss of ∼3 to 6 sulfurs and exposure to hydride-forming metal ions.

Ultrafine Co-Mo oxide nanocrystals embedded in hierarchical N-doped carbon microflowers for high-performance lithium-ion batteries

Constructing hierarchical architecture consisting of low-dimensional building blocks is attracting attention as an efficient strategy for achieving high electrochemical performance for lithium-ion batteries (LIBs). Herein, convenient synthesis of Co-Mo oxide composites embedded in a hierarchical N-doped carbon microflower (Co-Mo oxide/NC) is demonstrated. The Co-Mo/polydopamine (PDA) precursor prepared by the spontaneous coordination between the metal ion and dopamine can be easily transformed into Co-Mo oxide/NC by a two-step thermal annealing process. The as-obtained hierarchical microflowers have the advantages of hierarchical structured electrode materials, such as increased contact area with the electrolyte, abundant ion storage sites, and high electrical conductivity. Concurrently, the synergistic effect between molybdenum and cobalt ions can improve the electrochemical performance. Consequently, the hierarchical microflowers as LIB anode materials exhibit a high reversible specific capacity of 1115 mA h g−1 at 1.0 A g−1 after 200 cycles and superior rate performance with a capacity of 577 mA h g−1 at 30.0 A g−1. Moreover, in the long-term cycling stability at a high current density (10.0 A g−1), the electrode shows excellent cycling stability with a capacity of 508 mA h g−1 for 500 cycles. The present study reveals the importance of designing hierarchical structured materials to enhance electrochemical energy storage applications.

Electrical conductivity and corrosion resistance of Mo/Ti/Mn-based composite conversion films on AZ91D magnesium alloy

In this reported study, conductive composite conversion films on an AZ91D magnesium alloy were prepared by adding Ga3+ to a deposition solution that contained molybdenum, titanium and manganese ions. The Ga3+ significantly improved the conductivity and corrosion resistance of the resulting films. The electrical contact resistance (ECR) of the Molybdenum/Titanium/Manganese (MTM) film decreased from 0.436 Ω/in2 to 0.106 Ω/in2 at 200 psi when Ga3+ was added to form the Molybdenum-Titanium-Manganese-Gallium (MTMG) film. In addition, the polarization resistance of the Ga3+ amended film increased from 633.1 Ω·cm2 to 1930.835 Ω·cm2, MTMG showed obvious passivation behavior. The Ga3+ doping appeared to increase the carrier concentration and narrow the band gap of the semiconductor film. The N-type semiconductor carrier concentration increased from 2.11 × 1019 cm−3 to 7.052 × 1019 cm−3 in the MTMG film vs the MTM film. The P-type semiconductor carrier concentration in the MTMG film increased from 2.727 × 1018 cm−3 to 3.480 × 1019 cm−3 compared to the MTM film. The MTM band gap decreased from 2.916 eV to 2.714 eV in the MTMG film, which was attributed to the cross-doping of Ga3+ with transition metals in the MTMG material. The MTMG film had a three-layer structure, which preferentially formed a thin film on the β-phase and subsequently grew layer by layer.

Construction of an optical sensor for molybdenum determination based on a new ionophore immobilized on a polymer membrane

ObjectivesIn this study, a new optical chemical sensor to assess molybdenum ion by incorporation of 1-(2-benzothiazolylazo)-2-hydroxy-3-naphthoic acid (BTAHN), dibutylphthalate (DBP) and sodium tetraphenylborate (NaTPB) to the plasticized poly vinyl chloride (PVC) matrices were prepared. MethodsWhen DBP was added to the membrane, the ionophore's tendency to act as a chromoionophore was greatly increased. Great stability, reproducibility, extended life time, and respectable selectivity for Mo6+ ion assessment throughout a wide number of transition, lanthanides, and heavy metals were all advantages of the accomplished sensor. ResultsAt optimum compositions and investigational circumstances, the sensor response was linear cross range of 8.5 × 10−8 to 4.4 × 10−5 mol/L. Sensor detection and quantification limits realistic on the definition that the sample amount results in a signal equal to the blank signal plus three and ten times of its standard deviation were establish to be 2.5 × 10−8 and 8.3 × 10−8 mol/L. The sensor reaction time (characterized as the time it required for the absorbance value to reach 95 %) was 3.0–5.0 min. ConclusionsThe achieved optical sensor was successfully applied to assess Mo6+ ion content in water, food, plant, and environmental samples.

Boosting the electrical and charge transfer properties of TiO2 by the effect of Mo doped and rGO nanocomposite

The full-scale potential of the solar cell was limited due to its poor transport properties. The low mobility of charge carriers in the electron extraction layers can be overcome via engineering the materials with doping and composition with carbon-based materials. In the present work, we investigate the charge transport properties of TiO2 lattice by doping with Molybdenum ions and by composting with rGO. Different mole concentration of Mo-doped TiO2 was synthesized by the solvothermal method. The structural, optical, electrical and charge transport properties of Molybdenum doped TiO2 were analysed. In particular, 2 mol% of Mo-doped TiO2 lattice exhibited better charge transfer behaviour than the pure TiO2. Integrating this with rGO improved the carrier mobility and electrical conductivity by many folds. The EIS analysis confirmed the fast charge transition, and the time-resolved photoluminescence analysis revealed the long-lived nature of charge carriers in the conduction band. The conductive nature of the rGO sheets reduced the charge transfer resistance in Mo-doped TiO2/rGO composite by 9-fold compared to the pure TiO2, thus making it a better candidate for the electron transport layer.

MoaE Is Involved in Response to Oxidative Stress in Deinococcus radiodurans.

Molybdenum ions are covalently bound to molybdenum pterin (MPT) to produce molybdenum cofactor (Moco), a compound essential for the catalytic activity of molybdenum enzymes, which is involved in a variety of biological functions. MoaE is the large subunit of MPT synthase and plays a key role in Moco synthesis. Here, we investigated the function of MoaE in Deinococcus radiodurans (DrMoaE) in vitro and in vivo, demonstrating that the protein contributed to the extreme resistance of D. radiodurans. The crystal structure of DrMoaE was determined by 1.9 Å resolution. DrMoaE was shown to be a dimer and the dimerization disappeared after Arg110 had been mutated. The deletion of drmoaE resulted in sensitivity to DNA damage stress and a slower growth rate in D. radiodurans. The increase in drmoaE transcript levels the and accumulation of intracellular reactive oxygen species levels under oxidative stress suggested that it was involved in the antioxidant process in D. radiodurans. In addition, treatment with the base analog 6-hydroxyaminopurine decreased survival and increased intracellular mutation rates in drmoaE deletion mutant strains. Our results reveal that MoaE plays a role in response to external stress mainly through oxidative stress resistance mechanisms in D. radiodurans.

Renal Clearable Mo-Based Polyoxometalate Nanoclusters: A Promising Radioprotectant against Ionizing Irradiation.

In response to diffused ionizing radiation damage throughout the body caused by nuclear leaks and inaccurate radiotherapy, radioprotectants with considerable free radical scavenging capacities, along with negligible adverse effects, are highly regarded. Herein, unlike being performed as toxic chemotherapeutic drug candidates, molybdenum-based polyoxometalate nanoclusters (Mo-POM NCs) were developed as a non-toxic potent radioprotectant with impressive free radical scavenging capacities for ionizing radiation protection. In comparison to the clinically used radioprotectant drug amifostine (AM), the as-prepared Mo-POM NCs exhibited effective shielding capacity by virtue of their antioxidant properties resulting from a valence shift of molybdenum ions, alleviating not only ionizing radiation-induced DNA damage but also disruption of the radiation-sensitive hematopoietic system. More encouragingly, without trouble with long-term retention in the body, ultra-small sized Mo-POM NCs prepared by the mimetic Folin-Ciocalteu assay can be removed from the body through the renal-urinary pathway and the hepato-enteral excretory system after completing the mission of radiation protection. This work broadened the biological applications of metal-based POM chemotherapeutic drugs to act as a neozoic radioprotectant.

Characterization of ion release from a novel biomaterial, Molybdenum-47.5Rhenium, in physiologic environments

BACKGROUND CONTEXTMetals from spinal implants are released into surrounding tissues by various mechanisms. Metal ion release has been associated with clinical implant failure, osteolysis, and remote site accumulation with adverse events. Significant corrosion and associated metal ion release has been described with currently used spinal implant alloys. A novel metal alloy, Molybdenum-47.5Rhenium alloy (MoRe®), was approved for use in medical implants in 2019 by the FDA. PURPOSETo evaluate the metal ion release profile of MoRe alloy after immersion in both a stable physiologic, as well as in an inflammatory environment. STUDY DESIGNIn vitro study. METHODSThe ion release profile of the MoRe alloy was comprehensively evaluated in-vitro after prolonged immersion in physiologic and inflammatory environments. Ion concentration analyses were then conducted using inductively coupled plasma-mass spectrometry (ICP-MS) methods. Comparative testing of titanium (Ti-6Al-4V) and cobalt chromium (Co-28Cr-6Mo) was also performed. RESULTSUnder baseline physiologic conditions, the MoRe alloy demonstrates very low molybdenum and rhenium ion release rates throughout the 30-day test period. During the first time interval (day 0–1), low levels of molybdenum and rhenium ions are detected (<0.3 μg/cm2 day) followed by a rapid reduction in the ion release rates to <0.05 μg/cm2 day during the second time interval (days 1–3) followed by a further reduction to very low steady-state rates <0.01 μg/cm2 day during the third time interval (days 3–7), which were maintained through 30 days. In the inflammatory condition (H2O2 solution), there was a transient increase in the release of molybdenum and rhenium ions, followed by a return to baseline ion release rates (days 2–4), with a further reduction to low steady-state rates of ∼0.01 μg/cm2 day (days 4–8). The measured molybdenum and rhenium ion release rates in both steady state (<0.01 μg/cm2 day), and inflammatory environments (0.01 μg/cm2 day) were far below the established FDA-permitted daily exposure (PDE) of 1,900 μg/cm2 day for molybdenum and 4,400 μg/cm2 day for rhenium. In contrast, titanium and cobalt chromium approached or exceeded their established PDE values in an inflammatory environment. CONCLUSIONSThe novel biomaterial MoRe demonstrated a lower metal ion release profile in both a physiologic and inflammatory environment and was well below the established PDE. Comparative testing of the cobalt-chromium and titanium alloys found higher levels of ion release in the inflammatory environment that exceeded the PDE for cobalt and vanadium.

Excellent upconversion luminescence intensity in Er3+/Yb3+/Mo4+ triple-doped BiTa7O19 phosphors

BiTa7O19:Er3+/Yb3+/Mo4+ phosphors with excellent upconversion luminescence (UCL) intensity were synthesized by high temperature solid state method. The crystal structure, grain morphology and valence states of molybdenum ions were determined by X-ray diffraction (XRD), field emission scan electronic microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) technologies, respectively, and the UCL properties were studied by spectroscopy under 980 nm laser excitation. The green UCL intensity of BiTa7O19:0.1Er3+/0.4Yb3+/0.4Mo4+ is 1.66 times higher than that of commercial NaYF4:Er3+/Yb3+ under 980 nm laser excitation with 18.09 W/cm2. The UCL intensity of BiTa7O19:Er3+/Yb3+ phosphors increased first and then decreased with the increase of 980 nm laser excitation power density (0.38–56.69 W/cm2), while the UCL intensity of BiTa7O19:Er3+/Yb3+/Mo4+ phosphors can keep increasing with the increase of excitation power density. Based upon the luminescence intensity ratio (LIR) technique, the maximum absolute sensitivity (SA) is 0.01046 K−1 at 401 K. The experiment proved that BiTa7O19:Er3+/Yb3+/Mo4+ phosphors had strong acid and alkali resistance compared with NaYF4:Er3+/Yb3+. It indicates that BiTa7O19:Er3+/Yb3+/Mo4+ can replace NaYF4:Er3+/Yb3+ to be applied as luminescence imaging and temperature sensors in complex environments under high 980 nm laser excitation power density.

Crystallization kinetics and structural studies of Li1.25Al0.5Ge1.5P2.75Mo0.25O12 (LAGPM) glass/glass-ceramics based solid state electrolyte

The crystallization kinetics and structural behaviour of Li1.25Al0.5Ge1.5P2.75Mo0.25O12 (LAGPM) glass/glass-ceramics system have been investigated. Glass was prepared by melting the calcined initial charges at 1450 °C using conventional quenching technique. From model free crystallization kinetics, the value of activation energy obtained was 165 kJ mol−1. The nature of nucleation and the dimension of growth of the NASICON crystal were estimated from the kinetics parameters. This glass was converted to glass-ceramics using suitable heat schedule as per DTA data. X-ray diffraction analysis confirmed the formation of desired NASICON phase along with AlPO4 as minor phase. Raman spectroscopy and EXAFS studies showed that molybdenum ions moved to the desired tetrahedral sites in glass-ceramic. The dimension of the crystal growth was clearly seen in SEM image of LAGPM glass-ceramics sample. Impedance spectroscopy was carried out to evaluate the dc ionic conductivity (σdc) of LAGPM glass-ceramics based solid electrolyte. The value of σdc evaluated from the Nyquist plot was found as ∼4.64 × 10−4 S.cm−1 at room temperature.

Photochromism of TiO2 Nanoparticles Doped with Molybdenum Ions: Neutral Color Change from Colorless to Black via Gray.

Transition metal oxide nanoparticles have been extensively studied for the development of smart windows which are expected to be a promising technology to save energy in buildings. However, most of them turn blue under UV irradiation. Since the blue coloration affects the color of objects through the windows, the development of materials with a neutral color which hardly disturbs the view is more beneficial. In this work, we prepared a colorless-transparent TiO2 colloidal solution containing Mo6+ ions (Mo-TiO2), which turns black via gray in a nitrogen atmosphere under UV irradiation. An absorption peak was observed at 535 nm, which increased with an increase in the UV irradiation time and reached a constant value (Absmax). The Absmax value increased linearly with an increase in the Mo doping amount. We demonstrated that the photochromic behavior of the Mo-TiO2 nanoparticles is completely different from that of pure MoO3 or the mixture of MoO3 and TiO2. In addition, we performed a kinetic study to elucidate the mechanism and found that the coloration rate at the initial stage decreased with an increase in Mo doping amount. Based on the kinetic analysis, the following results are obtained: a color center is formed at a deeper energy level than the Mo dopant level; the number of the color center depends on the Mo doping amount, and the color center traps the photogenerated electrons more rapidly when it is isolated. The black color was bleached by purging the air in the solution. In particular, the gray state which is observed as a transient color is promising for the development of smart windows to shield the sunlight while allowing a clear and undistorted view.

An Important Role of the Type VI Secretion System of Pseudomonas aeruginosa Regulated by Dnr in Response to Anaerobic Environments.

The type VI secretion system (T6SS) is capable of secreting a variety of metal-binding proteins involved in metal ion uptake, and it mediates an active metal ion transport system that contributes to competition between bacteria. Pseudomonas aeruginosa H2-T6SS can increase molybdenum ion acquisition and enhance bacterial survival advantage by promoting the secretion of the molybdate-binding protein ModA, in which the expression of H2-T6SS core genes hcp2, hsiA2, and clpV2 is activated by anaerobic conditions and are all regulated by the global regulator Anr. Here, we report the regulation of T6SS by Dnr, a dedicated dissimilatory nitrate respiration regulator in P. aeruginosa. Of the three distinct T6SS loci carried by P. aeruginosa, only the anaerobic expression of H2-T6SS was activated by Dnr; H1-T6SS or H3-T6SS did not respond to anaerobically induced activation. We also demonstrated that Dnr promotes the anaerobic secretion of ModA, which acts as a potential substrate for H2-T6SS, providing an advantage not only for the anaerobic growth of bacteria but also for functional competition. Overall, this study elucidates the important role played by Dnr in mediating the anaerobic expression of T6SS in P. aeruginosa, indicating that the functional advantage of H2-T6SS in response to anaerobic induction may be a conditional environmental adaptation. It also extends our understanding of the function of Dnr as a specific regulator of dissimilatory nitrate respiration. IMPORTANCE The type VI secretion system (T6SS) plays an important role in bacterial competition by mediating the transport of active metal ions. Pseudomonas aeruginosa carries three distinct T6SS loci (H1-, H2-, and H3-T6SS). The H2-T6SS promotes the secretion of the molybdate-binding protein ModA for the acquisition of molybdenum ions to adapt to anaerobic survival. Here, we report that the specialized dissimilatory nitrate respiration regulator Dnr in P. aeruginosa controls the anaerobic expression of H2-T6SS and that this regulation is essential for ModA protein secretion, anaerobic growth, and bacterial competition. This study elucidates the regulatory mechanism of Dnr on H2-T6SS in P. aeruginosa, revealing an important role played by H2-T6SS in adapting to an anaerobic environment.

Optimized Solid-State Synthesis of Sr2Fe1.5Mo0.5O6−δ Perovskite: Implications for Efficient Synthesis of Mo-Containing SOFC Electrodes

Sr2Fe1.5Mo0.5O6−δ (SFMO) perovskite has been considered as a promising anode candidate for solid oxide fuel cells. However, the significant inconsistency in the conductivity properties of SFMO perovskite has been reported in the literature through various synthesis procedures, highlighting the necessity of a standard and unified synthesis process. In this work, we propose an optimized solid-state synthesis process of SFMO perovskite based on the thermal properties of the precursors. Our TG analysis indicates that the evaporation of MoO3 during sintering over 752 °C may affect the synthesis of the expected SFMO perovskite. The presence of Fe2O3 has a trap effect on MoO3, based on the TG analysis of the binary mixture. A cubically structured SFMO perovskite without a secondary phase is obtained from the as-proposed stepwise sintering program while an impurity phase of SrMoO4 is observed when adopting a direct sintering program. The as-synthesized SFMO perovskite exhibits high stability in a reducing atmosphere, which is attributed to the self-adjustment of the overall valence states of molybdenum ions and iron ions. Many pure cubically structured perovskites have been successfully synthesized using the as-proposed solid-state synthesis process, suggesting its universality for the synthesis of other Mo-containing SOFC perovskite electrodes.

Surface ion with Mo, Ti and Al for steel studies

Modification of metals by a surface treatment is one of the first problems of modern mate- rials science. The use of ion-plasma technologies for a modification of initial specimens, in particular, by ion implantation, for this purpose can be considered a promising solution. We study the microstructure, phase and elemental compositions, wetting forces, and electrical properties of steel with implanted ions of titanium, aluminum, and molybdenum. The results obtained by means of XRD, XPS, optical microscopy, and laboratory experiments show sig- nificant differences between the treated and untreated specimens. The modification of metal by ion implantation causes changes in the wettability and electrical characteristics and indicates the prospects of this technology for mechanical engineering, chemical, food, pharmaceutical industries, for the construction of structures and vehicles, including their work under severe atmospheric conditions.

Crystal structure and microwave dielectric characteristics of ixiolite ceramics with molybdenum ion modification and tri-layered structure

The ZnTi1−xMoxNb2O8 (0.000 ≤ x ≤ 0.060) microwave dielectric ceramics were prepared through traditional solid-state reaction. Mo4+ substitution for Ti4+ can markedly improve the microwave dielectric characteristics of ZnTiNb2O8 system. In the microstructures investigation, a suitable degree of Mo4+ substitution was shown to be useful for creating uniform grain size and minimizing dielectric loss. Raman spectroscopy and complex chemical bond theory analyses demonstrate that the bond ionicity of NbO bond is the intrinsic component influencing the εr value. The lattice energy of NbO bond, bond valence of Cation-O bond, and the FWHM of Raman spectra were the primary determinants of Q×f value. The τf value is mostly determined by variations in NbO bond energy and the bond valence of Cation-O bond. When x = 0.010, ZnTi0.990Mo0.010Nb2O8 ceramics exhibit excellent microwave dielectric characteristics: εr = 33.91, Q×f = 64,136 GHz, and τf = − 50.57 ppm/°C. Furthermore, in order to improve the temperature coefficient of resonant frequency (τf values close to zero) for the ZnTi0.990Mo0.010Nb2O8 ceramics, the TiO2 and laminated co-firing technique were used to adjust the comprehensive microwave dielectric characteristics of the ZnTiNb2O8 system. When the mass fraction of the TiO2 layer reaches 0.03 wt% after sintering at 1150 °C, the tri-layer structural ZTMN-0.03TO-ZTMN ceramics obtain outstanding microwave dielectric characteristics: εr = 41.52, Q×f = 50,827 GHz, and τf = − 2.59 ppm/°C, and these characteristics make them potential for usage in 5G communications.

On the Electronic Structure of 2H-MoS2: Correlating DFT Calculations and In-Situ Mechanical Bending on TEM.

We present a systematic density functional theory study to determine the electronic structure of bending 2H-MoS2 layers up to 75° using information from in-situ nanoindentation TEM observations. The results from HOMO/LUMO and density of states plots indicate a metallic transition from the typical semiconducting phase, near Fermi energy level (EF) as a function of bending, which can mainly occur due to bending curvatures inducing a stretching and contracting of sulfur-sulfur chemical bonds located mostly over basal (001)-plane; furthermore, molybdenum ions play a major role in such transitions due to reallocation of their metallic d-character orbitals and the creation of “free electrons”, possibly having an overlap between Mo-dx2-y2 and Modz2 orbitals. This research on the metallic transition of 2H-MoS2 allows us to understand the high catalytic activity for MoS2 nanostructures as extensively reported in the literature.