Mo-O Bond Research Articles

Theoretical study on the application of the largest aluminum-pyrazole ring in electrochemical nitrogen reduction reaction

Electrochemical nitrogen reduction reaction (NRR) is a mild and sustainable method for ammonia synthesis. Therefore, developing high activity, selectivity, and economic efficiency catalysts with considering the synergistic effects between catalysts and carriers to design novel structural models is very important. Considering the non-noble metal NRR catalyst, Mo3, we tried to find a suitable carrier which is stable and economical. Herein, we used the largest atomically precise aluminum-pyrazole ring (AlOC-69) to date (diameter up to 2.3 nm). The larger ring cavities and the presence of abundant hydroxy groups make AlOC-69 an ideal molecular carrier model and provide a basis for studying its structure-activity relationship. The formation energy (−0.76 eV) and stable Mo-O bonds indicate that Mo3 can be stabilized on the Al10O10 surface. Additionally, N2 has fully activated due to the strong interaction between the p-orbital of N and the d-orbital of Mo. The low limiting potential (−0.28 V) emerges that Mo3@Al10O10 has ideal catalytic activity and selectivity. This research provides a promising catalyst model and an understanding of its catalytic process at the atomic level, providing a new approach for the co-design of catalyst and carrier in NRR.

In situ highly dispersed loading of molybdenum dioxide with oxygen vacancies on N-doped graphene for enhanced oxidative desulfurization of fuel oil

Herein, molybdenum dioxide (MoO2) nanoparticles with a particle size of 1.78 nm was uniformly anchored on nitrogen-doped reduced graphene oxide (NrGO) with strong electron-donating effect by in situ annealing of the precursor composed of polyaniline-modified graphene oxide (PANI/GO) and ammonium molybdate. The as-prepared MoO2/NrGO catalyst at 800 °C showed the excellent oxidative desulfurization (ODS) activity and reusability. In the presence of H2O2, the DBT removal over MoO2/NrGO-800 could reach 99.8 % within 10 min at 60 °C, and it was almost still retained even after 8 cycles. The outstanding ODS performance is importantly ascribed to the following aspects. The electron transfer from electron-rich NrGO to MoO2 could not only weaken Mo-O bonds and improve the small size and dispersion of MoO2, resulting in more oxygen vacancies and exposed active sites, but also reduce the leaching of active sites due to the induced electronstatic interaction. Oxygen vacancies intrinsiclly facilitate the generation of active oxygen intermediates. Radical scavenger experiments and electron paramagnetic resonance (EPR) revealed that during the DBT oxidation over MoO2/NrGO-800, •OH radicals are the major active species, and electron transfer is still an important step.

Catalytic performance and mechanism of bismuth molybdate nanosheets decorated with platinum nanoparticles for formaldehyde decomposition at room temperature

Catalytic oxidation at room temperature is considered as a promising strategy for removal of formaldehyde (HCHO), a widely occurring indoor air pollutant. A series of Bi2MoO6 nanosheets were prepared via one-step hydrothermal synthesis in this study, followed by decoration with Pt nanoparticles (NPs). The catalyst with Bi2MoO6 support prepared at 180 °C exhibited high and stable activity in catalytic oxidation of HCHO at room temperature. The excellent catalytic performance was attributed to its large specific area and pore volume, high level of surface active oxygen species, high content of metallic Pt NPs, and abundant oxygen vacancies. The good synergy and interaction between Pt and Bi2MoO6 promoted electron transfer, and facilitated the adsorption and oxidation of HCHO. The electronic interaction between Pt NPs and Bi2MoO6 accelerated the activation of oxygen species due to weakening of the surface BiO or MoO bonds adjacent to Pt NPs. Infrared spectra indicated that dioxymethylene and formate species were the main intermediates of HCHO oxidation. Density functional theory calculations showed that the dehydrogenation of HCO2, with an energy barrier of 282.1 kJ/mol, was the rate-determining step in catalytic oxidation process. This study provides new insights on the construction of high-efficiency catalysts for indoor formaldehyde removal.

Incorporation of polyoxometalate in La-BTC metal-organic frameworks for fast and selective removal of methylene blue dyes in water

This study prepares Mo-doped, particulate La-BTC metal-organic frameworks (Mo/La-BTC MOFs) using polyoxometalate over a broad Mo atomic fraction (fMo) from 0 to 0.9, and examines their selective adsorption against methylene-blue (MB) dyes in water. An increased Mo concentration up to 0.61 ​at% results in the Mo/La-BTC MOFs when fMo was increased to 0.9. Raman spectroscopy reveals an enhanced MoO bond intensity. The Mo/La-BTC MOFs show a linearly dependent MB adsorption uptake with the increasing fMo; to which, the MOF particles remove up to 75% of MB in water within only 1 ​min when using an initial MB concentration of 5 ​× ​10−6 ​M. This is in significant contrast with virtually zero removal against methyl-orange dyes. Our results indicate that the selective dye-removal capability depends solely on the [PMo12O40]3- complex as active sites on the La-BTC scaffold, and the MB adsorption remains effective over a broad pH range (3–10).

Enabling deep conversion reactions by weakening molybdenum-oxygen bonds through K+ pre-intercalation

Conversion-type transition metal oxides (TMOs) anodes with fascinating high theoretical capacities are considered potential candidates for high-energy-density alkali-ion batteries. However, the tremendous advantages of conversion reaction are yet to be fully exploited due to sluggish reaction kinetics and unfavorable thermodynamics. This is especially in the case of non-layered TMOs, where high ion intercalation energy and ion diffusion barriers compared to layered TMOs impede subsequent conversion reaction, while thermodynamically stable metal-oxide bonds with high bond energies prevent efficient cleavage. This work selects MoO2 as a typical non-layered anode of lithium-ion batteries and demonstrates that pre-intercalating K+ ions in MoO2 crystal can decrease the intercalation energy, enhance the diffusion kinetics, and weaken Mo-O bonds to efficiently facilitate conversion reactions by the the density functional theory calculations and experiments. K+ pre-intercalated MoO2 can deliver a higher reversible discharge specific capacity (989 mAh g−1) than the pristine MoO2 sample (720 mAh g−1) at 0.2 A g−1 after 100 cycles. This work provides a novel and crucial method to realize the functionality of non-layered TMOs based anodes and offers a potentially universal optimization strategy toward high-capacity alkali-ion batteries.

Flotation assessment and adsorption mechanism of wulfenite with three anionic collectors

ABSTRACT Wulfenite is a useful mineral containing both lead and molybdenum. Although the Mo theoretical content of wulfenite is too low to meet the sales requirement, how to pre-concentrate the wulfenite more efficiently and economically becomes increasingly important for subsequent leaching process. Using sodium oleate (NaOL), benzohydroxamic acid (BHA) and sodium dodecyl sulfonate (SDS) as collector, the flotation behavior of wulfenite has been investigated by micro-flotation tests, and the adsorption capacity of the three collectors on wulfenite has been measured and listed as below: NaOL (pH = 9.5) > SDS (pH = 6.5) > BHA (pH = 7.5). According to the frontier orbital theory analysis, when the collector ions act on the {112} surface of wulfenite, the effective mass of NaOL is the lowest, followed by SDS and BHA. Moreover, the molecular dynamics simulation of the three collector ions on wulfenite {112} surface reveals that the two adjacent outermost molybdenum atoms of wulfenite have strong adsorption due to the fracture of the original Mo-O bonds and could easily react with the single-bond oxygen atom outside the polar groups of the three collectors. Comparing the adsorption energy, NaOL has the best adsorption performance to wulfenite {112} surface, during which the O-Mo1 distance and O-Mo2 distance are both below 2.5 Å. By associations of the simulation results with flotation tests, when the feed contains 0.14% Mo, using NaOL as collector, a rough molybdenum concentrate with molybdenum grade of 17.25% and molybdenum recovery of 86.32% has been obtained by conventional flotation tests, which provide theoretical guidance and practical evidence to promote the wulfenite flotation performance.

Oxygen vacancy and Van der Waals heterojunction modulated interfacial chemical bond over Mo2C/Bi4O5Br2 for boosting photocatalytic CO2 reduction

The establishment of heterojunctions between phase interfaces is an important strategy to enhance catalytic activity, but the behavior of charge transfer and exciton dissociation is unsharpness and significant. Here, a Van der Waals heterojunction (VDWH) of Mo2C/Bi4O5Br2 composite with oxygen vacancies (BM) was synthesized via a facile method. Various experimental results and density functional theory calculations demonstrated that the compact VDWH and unsaturated oxygen vacancy induced interfacial Mo-O bonds to modulate surface electronic structure. Consequently, the electron extracted from the exciton formed a strong internal electric field, which boosted the dissociation of the excitons and charge transfer via the electron transfer channel of the Mo-O bond. Therefore, the BM shows excellent CO2 reduction performance (1277.4 µmol g−1 h−1) and stability without using sacrificial agents and cocatalysts, which is about 6 times of Mo2C/Bi4O5Br2. This work not only gives deep insights into charge separation in VWDH and oxygen vacancy but also provides an efficient photocatalyst for efficient green energy conversion.

In-situ growth of MoO2@N doped carbon on Mo2C-MXene for superior lithium storage

Molybdenum dioxide (MoO2) with high theoretical capacity and low cost has triggered extensive interest as a renowned anode for lithium ion batteries (LIBs). However, the sluggish diffusion kinetics and severe capacity decay obstructed its practical application. Herein, hierarchical spherical Mo2C-MXene@MoO2@C was fabricated through a self-assembly and carbonization strategy. DFT calculations and experimental results revealed that the incorporation of metallic Mo2C-MXene and carbon into MoO2 not only modulated the charge distribution and weakened Mo-O bond of MoO2, but also promoted the adsorption of Li+ on MoO2 and lowered the migration energy barrier for Li+, thereby accelerating the electrochemical kinetics, inducing a strong diffusion-controlled charge storage behavior and improving the electrochemical reversibility. In addition, the introduction of MXene reinforced the structural integrity of MoO2 during ion insertion and extraction, which ameliorated the electrochemical stability. Beneficiating from the above synergistic effect, the optimized Mo2C-MXene@MoO2@C delivered remarkable cycling capacity (854.5 mAh g−1 after 500 cycles at 0.5 A g−1) and superior rate capacity (644.4 mAh g−1 at 1 A g−1) for lithium storage. This work disclosed the charge storage mechanism of MoO2 and provided new guidance for the rational design of novel electrode materials for secondary batteries.

Theoretical study on the extraction behaviors of MoO22+ with organophosphorous extractants

99Mo is the parent isotope of 99mTc, which is commonly used in nuclear medicine, so the studies on the extraction of 99Mo have been attracted extensive attention. There are some experimental investigations about the extraction of Mo(VI) using the organophosphorous extractants including O-donor Cyanex 272 (HLa) and S-donor Cyanex 301 (HLb). We explored the coordination and complexing nature of Mo(VI) with HLa and HLb using scalar relativistic density functional theory. The electrostatic potentials and frontier molecular orbitals of HLa and HLb show that the former has stronger nucleophilic ability compared to the latter. All the MoO22+ complexes with HLa and HLb are tetra-coordinated structures. The values of Wiberg bond indices (WBIs) indicate that the Mo-S bonds have more covalency than Mo-O bonds. The energy decomposition analysis reveals that the interaction between MoO22+ ion with HLa is stronger than that with HLb, which is also supported by the thermodynamic energy. The thermodynamic energy indicates that [MoO2(H2O)2(NO3)]+ is the dominant initial species and reaction [MoO2(H2O)2(NO3)]++HL → [MoO2L(NO3)] + H++2H2O is the most preferred in the extraction process. This work elucidates the electronic structures and complexing nature of MoO22+ with Cyanex 272 and Cyanex 301 ligands and provides the useful theoretical information on designing acidic phosphorous extractants of MoO22+.

Bond characteristics and microwave dielectric properties of (Mn1/3Sb2/3)4+ doped molybdate based low-temperature sintering ceramics

Ce2[Zr1−x(Mn1/3Sb2/3)x]3(MoO4)9 (x = 0.1–1.0) ceramics were prepared by a conventional solid-state method. (Mn1/3Sb2/3)4+ ions occupied the Zr-site, and Ce2[Zr1−x(Mn1/3Sb2/3)x]3(MoO4)9 solid solution was obtained. With x value increased, the εr decreased from 10.47 (x = 0.02) to 10.10 (x = 0.10), which was affected by bond ionicity of Zr/(Mn1/3Sb2/3)1O4 bond. The Q·f value first increased and then decreased, which was controlled by varying packing fraction, relative density, and lattice energy (CeO bond). The thermal expansion coefficient and bond energy of MoO bond were associated with τf value. Besides, infrared reflection spectrum suggested that the properties were primarily derived from the absorption of phonon in the infrared range. Outstanding microwave dielectric properties of Ce2[Zr0.92(Mn1/3Sb2/3)0.08]3(MoO4)9 ceramics were obtained when sintered at 700 °C: εr = 10.29, Q·f = 91,981 GHz and τf = −9.81 ppm/°C.

Effects of film thickness and annealing temperature on the properties of molybdenum carbide films prepared using pulsed direct-current magnetron sputtering

Molybdenum carbide (Mo2C) films were prepared using pulsed direct-current (DC) magnetron sputtering. The effects of film thickness on the phase structure, surface morphology, and optical constants of the films were examined using X-ray diffraction (XRD), atomic force microscopy, and extreme ultraviolet reflectivity. XRD analysis showed that the as-sputtered films with thicknesses between 30 nm and 150 nm were almost amorphous. New phase α-MoC1-x with the (111), (200), (220), (311), and (222) crystal planes appeared in films with thicknesses between 200 nm and 400 nm. The phase transition and chemical composition of the Mo2C films treated using vacuum heat treatment were analyzed in detail. For 150 nm-thick films, the as-deposited as well as the 600 °C-annealed films were amorphous. The phase structures of the 150 nm-thick film annealed at 700 °C, 750 °C, and 800 °C were orthogonal Mo2C (α–Mo2C), multiphase structure (β–Mo2C, monoclinic MoO2, and cubic Mo2N), and monoclinic MoO2, respectively. X-ray photoelectron spectrometry revealed that the Mo-Mo bonds of the films transformed into Mo-C, Mo-O, and Mo-N bonds under 750 ℃-annealing, further confirming the formation of a multiphase structure after annealing. Thus, film thickness and annealing temperature considerably influence the properties of Mo2C films.

Rietveld Refinement, Morphology, and Optical and Photoluminescence Properties of a β-Ag1.94Cu0.06MoO4 Solid Solution.

Corner-truncated cubic β-Ag1.94Cu0.06MoO4 microcrystals were synthesized using the hydrothermal method. These were investigated by X-ray diffraction, confirming obtention of the spinel structure Fd3̅m. Through Raman spectroscopy are confirmed all modes for the point group of Oh7. The Egap shows a decrease of the band gap from 3.20 to 3.07 eV, with reduction of the conduction band occurring from -0.20 eV (β-Ag2MoO4) to -0.13 eV (β-Ag1.94Cu0.06MoO4), suggesting a p-type behavior for the Cu2+ ion. The field-emission scanning electron microscopy images confirm the morphological changes for β-Ag2MoO4, where potato-like microcrystals were found. Meanwhile, corner-truncated cubic microcrystals for β-Ag1.94Cu0.06MoO4. The photoluminescence (PL) spectrum confirms the increase in the PL emission for β-Ag1.94Cu0.06MoO4, with suppression of the deep defects occurring in the structure caused by oxygen and silver atoms. In contrast, the green region is intensified because of distortions of the Ag-O and Mo-O bonds. Therefore, the β-Ag1.94Cu0.06MoO4 solid solution has PL emission with CCT (4510 K) and CIE coordinates (x = 0.372 and y = 0.433), which could be interesting properties for applications as light-emitting diodes.

Synthesis and structure of a pyridine-stabilized silanone molybdenum complex and its reactions with PMe3 and acetone.

Silanones (OSiR2) are highly reactive species that readily convert to oligomeric siloxane (O-SiR2)n. The coordination of silanones to transition metal fragments to afford silanone-coordinated complexes is a reliable silanone stabilization method. Herein, a pyridine-stabilized silanone molybdenum complex Cp*(OC)2Mo{OSiMes2(py)}(SiMe3) (2b, Cp*: η5-C5Me5, Mes: 2,4,6-Me3C6H2, and py: pyridine) was synthesized by reacting the silyl(silylene) complex Cp*(OC)2Mo(SiMes2)(SiMe3) (4b) with pyridine-N-oxide in pyridine. X-ray crystal structure analysis revealed that the geometry of complex 2b is similar to those of the previously synthesized DMAP-stabilized analogue Cp*(OC)2Mo{OSiMes2(DMAP)}(SiMe3) (2a, DMAP: 4-(dimethylamino)pyridine). The SiO and Mo-O bond distances in 2b are similar to those observed in 2a, but the N-Si coordination bond of 2b is slightly longer (approximately 0.05 Å) than that of 2a, indicating weaker pyridine coordination than that of DMAP. The reaction of 2a with excess PMe3 in C6D6 at room temperature for 28 h afforded Cp*(OC)2Mo(PMe3)(SiMe3) (5c) in a 43% NMR yield. In contrast, reacting 2b with excess PMe3 in C6D6 at room temperature for 9 h afforded 5c and the five-membered metallacyclic carbene complex Cp*(OC)Mo(C(SiMe3)OSiMes2O)(PMe3) (6) in 10% and 41% NMR yields, respectively. The reactions of pyridine-stabilized silanone complexes Cp*(OC)2M(OSiMes2(py))(SiMe3) (M = Mo (2b) and W (1b)) with acetone proceeded via pyridine elimination, coordination of acetone to the Si center in the silanone ligand, and elimination of HSiMe3 to give Cp*(OC)2M{OSiMes2OC(Me)CH2} (M = Mo (8) and W (9)) in high yields.

Synthesis and Structure-Activity Characterization of a Single-Site MoO2 Catalytic Center Anchored on Reduced Graphene Oxide.

Molecularly derived single-site heterogeneous catalysts can bridge the understanding and performance gaps between conventional homogeneous and heterogeneous catalysis, guiding the rational design of next-generation catalysts. While impressive advances have been made with well-defined oxide supports, the structural complexity of other supports and the nature of the grafted surface species present an intriguing challenge. In this study, single-site Mo(═O)2 species grafted onto reduced graphene oxide (rGO/MoO2) are characterized by XPS, DRIFTS, powder XRD, N2 physisorption, NH3-TPD, aqueous contact angle, active site poisoning assay, Mo EXAFS, model compound single-crystal XRD, DFT, and catalytic performance. NH3-TPD reveals that the anchored MoO2 moiety is not strongly acidic, while Mo 3d5/2 XPS assigns the oxidation state as Mo(VI), and XRD shows little rGO periodicity change on MoO2 grafting. Contact angle analysis shows that MoO2 grafting consumes rGO surface polar groups, yielding a more hydrophobic surface. The rGO/MoO2 DRIFTS assigns features at 959 and 927 cm-1 to the symmetric and antisymmetric Mo═O stretching modes, respectively, of an isolated cis-(O═Mo═O) moiety, in agreement with DFT computation. Moreover, the Mo EXAFS rGO/MoO2 structural data are consistent with isolated (C-O)2-Mo(═O)2 species having two Mo═O bonds and two Mo-O bonds at distances of 1.69(3) and 1.90(3) Å, respectively. rGO/MoO2 is also more active than the previously reported AC/MoO2 catalyst, with reductive carbonyl coupling TOFs approaching 1.81 × 103 h-1. rGO/MoO2 is environmentally robust and multiply recyclable with 69 ± 2% of the Mo sites catalytically significant. Overall, rGO/MoO2 is a structurally well-defined and versatile single-site Mo(VI) dioxo heterogeneous catalytic system.

Interface engineering: Synergism between S-scheme heterojunctions and Mo-O bonds for promote photocatalytic hydrogen evolution

Simple high-temperature calcination and hydrothermal methods were followed to synthesize CeO2 and Mo-S, respectively. The efficient photocatalytic hydrogen evolution activity exhibited by the composite catalysts can be attributed to the edge active sites in Mo-S. The Mo-O bonds formed between CeO2 and Mo-S could further accelerate the processes of separation and migration of electrons between the catalyst interfaces. The hybrid catalyst 10%-CeO2/Mo-S exhibiting the best hydrogen generation ability (4.3 mmol h−1g−1) was obtained by optimizing the content of CeO2 in CeO2/Mo-S. Analysis of the PL spectral profile and photocurrent response recorded for the system revealed that 10%-COMS exhibited excellent photogenerated carrier separation ability. Analysis of the LSV and EIS curves revealed that 10%-COMS exhibited the optimal hydrogen production potential. The charge migration resistance provided by the systems was lower than the charge migration resistance provided by CeO2 and Mo-S. The synergism between the S-scheme heterojunctions and the Mo-O bonds helped accelerate the separation and migration of photo-induced carriers at the catalyst interfaces. The introduction of covalent bonds in the S-scheme heterojunctions and the results presented herein can potentially help develop a new method to realize photocatalytic hydrogen evolution.

Impact of algal extracellular polymeric substances on the environmental fate and risk of molybdenum disulfide in aqueous media

Molybdenum disulfide (MoS2) poses great potential in water treatment as a popular transition metal dichalcogenide, arousing considerable concern regarding its fates and risk in aquatic environments. This study revealed that the interplay with extracellular polymeric substances (EPS) of freshwater algae significantly changed the properties and toxicity of MoS2 to aquatic fish. The predominant binding of aromatic compounds, polysaccharides, and carboxyl-rich proteins in EPS on the 1T polymorph of MoS2 via hydrophilic effects and the preferential adsorption of carboxylic groups contributed to morphological alterations, structural disorders (band gap and phase alterations), and the attenuated aggregation of MoS2 in aqueous solutions. Electron charge transfer and n-π* interactions with EPS decreased the catalytic activity of MoS2 by inhibiting its capability of generating reactive intermediates. The dissolution of MoS2 slowed down after interacting with EPS (from 0.089 to 0.045 mg/L per day) owing to rapid initial oxidation (i.e., forming Mo-O bond) and carbon grafting. Notably, the morphological and structural alterations after EPS binding alleviated the toxicity (e.g., malformation and oxidative stress) of MoS2 to infantile zebrafish. Our findings provide insights into the environmental fate and risk of MoS2 by ubiquitous EPS in natural waters, serving as valuable information while developing water treatment processes accordingly.

Adsorption Characteristics and Mechanism of Calcium Ions on Different Molybdenite Surfaces via Experiments and DFT Simulations

Calcium ions are common in flotation process water, and have a significant effect on the molybdenite floatability, making separation of molybdenite from other minerals more difficult. Therefore, to improve the separation selectivity, the research of how calcium ions affect the molybdenite surface properties is of great significance. In this study, various methods including flotation tests, contact angle measurements, batch adsorption tests and Density Functional Theory (DFT) simulations were carried out to understand the adsorption characteristics and mechanism. Results of the contact angle measurements showed that the inhibition effects of calcium ions on molybdenite flotation kinetics were mostly attributed to the decrease of the edge surface hydrophobicity, as the contact angle of the edge surface decreased more than the face surface after treatment with calcium ions. While fitting the results of batch adsorption tests with adsorption kinetics and isotherm models, it was found that the Lagergen pseudo-first-order equation and the Freundlich isotherm model nicely follow the experimental trend. Moreover, DFT calculation results indicated that both Ca2+ and CaOH+ preferentially adsorb on the molybdenite (100) surface, particularly the edge surface, which was consistent with the contact angle results. Ca2+ adsorbed on the Mo-top site on the S-(100) surface by forming Ca-S bonds, transferring electrons from Ca 3d orbitals to S 3p orbitals. CaOH+ adsorbed on the S-top site of Mo-(100) surface by forming a strong covalent Mo-O bond and S-Ca bond. The results provide a basis for understanding and improving the separation effect of molybdenite from other minerals in the presence of calcium ions.

Photochromic response of the PLD-grown nanostructured MoO3 thin films

We have studied the PLD-grown nanostructured MoO3 thin film for its photochromic performance. MoO3 nanostructures were grown at room-temperature using PLD technique and subsequently annealed at 573 K. The annealedMoO3 films are then characterized by Raman spectroscopic study. The Raman spectra showed two strong peaks at 819 and 994 cm−1 due to the vibrations of the O-Mo6+-O and Mo6+-O bonds, respectively. Here, the peak at 994 cm−1 is ascribed to the terminal oxygen stretching mode for orthorhombic MoO3. Here, LASER power dependence on the Raman spectroscopic study was also done. Notably, the Raman peak is found to shift to low-frequency with increasing LASER power, most likely due to the coloration process which is attributed to variation in the Mo-O bond strengths and bond length in the nanocrystalline MoO3. The CAFM studies on the grown MoO3 nanostructures with LASER-ON and –OFF conditions were carried out at the various DC bias voltages from 10 V to −10 V. This study reveals that the MoO3 NS exhibits enhanced photochromic response. That is, with the LASER-ON, the Mo5+ states are generated due to the reduction of the Mo6+ states with induced electron incorporation by the LASER. The reduction leads to the transition from the Mo6+ to Mo5+, which obviously seen in the Raman data. As a consequence, the PLD-grown MoO3 nanostructures show a photochromic behavior.

In-situ growth of graphene quantum dots modified MoS2 membrane on tubular ceramic substrate with high permeability for both water and organic solvent

Molybdenum disulfide (MoS2) is widely used in membrane separation because of its outstanding chemical and structural stability. In this study, MoS2 nanosheets were in-situ grown on a tubular ceramic substrate through one-step hydrothermal synthesis with the graphene quantum dots (GQDs) incorporated in the precursor solution. The growth of the MoS2 nanosheets was inhibited due to the combination with GQDs through the Mo-O bond. Therefore, the number of transport channels in the MoS2/GQDs composite membrane were increased to improve the permeability. The results indicated that the MoS2/GQDs composite membrane have excellent permeances for both the aqueous solution and organic solvent. Moreover, the MoS2/GQDs composite membrane can be continuously operated in cross-flow filtration device for 100 h because the in-situ hydrothermal method has greatly improved the stability of membrane. The results indicated that the MoS2/GQDs composite membrane exhibits great potential in nanofiltration.

Synthesis, spectroscopic characterization and quantum chemical studies of a dioxomolybdenum(VI) complex with an N,S-substituted pyridoxal thiosemicarbazone

The new compounds Pyridoxal N-allyl-S-methylthiosemicarbazone (L) and the dioxomolybdenum(VI) complex [MoO2(L)CH3OH] have been synthesized and characterized by elemental analysis, UV–Vis, FT-IR, Raman and 1H NMR spectra, and also by the single crystal X-ray diffraction technique. Single crystals of the cis-dioxomolybdenum(VI) complex were obtained by evaporating its methanol solution. According to the single-crystal X-ray diffraction investigation, the molybdenum atom in the complex is in a distorted octahedral coordination. The sixth coordination site is occupied by the oxygen atom of a methanol solvent molecule. The methanol coordination between the oxygen and molybdenum atoms is the weakest bond, with a MoO bond length of 2.355 Å. The geometries and vibrational spectra of the pyridoxal thiosemicarbazone (L) and its complex are explained by quantum chemical calculations.