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The broad applications of rechargeable batteries urge people to develop alternative energy storage devices with sustainable resources, high capacity, long cycling life, and wide-temperature operability. Aqueous proton batteries are considered as a state-of-the-art energy storage system due to their intrinsic safety and low cost. However, aqueous electrolytes have a low boiling point and narrow electrochemical stability window, limiting their applications in wide-temperature and high-energy batteries. Herein, a hybrid organic ionic liquid electrolyte with organic alkali 1-methyl-1,2,4-triazole (MTA) protonated by organic acid bis(trifluoromethysulfonyl)imide (HTFSI) as proton carriers and tetramethylene sulfone (TMS) as the solvent, noted as HTFSI-MTA-TMS, exhibited the stable electrochemical windows exceeding 5 V at -20 °C and 3.5 V at 80 °C. Benefiting from this electrolyte, the assembled MnO 2 -S//MoO 3 button proton full battery can display an operation voltage up to 1.8 V, energy density of 44.8 Wh kg -1 , and good cycling stability at room temperature when bis(trifluoromethanesulfonyl)imide manganese (II) salt (Mn(TFSI) 2 ) is introduced into the electrolyte, and run well in a wide-temperature range (-20 °C-60 °C). The work reveals the potential of organic acid-alkali coregulated electrolytes to meet the need of energy storage in a wide-temperature range and will advance the development of high-energy proton batteries., (© 2024 Wiley‐VCH GmbH.)

Intercalation of several elements (Ag, Bi, In, Mo, Os, Pd, Pt, Rh, Ru, Sb, and W) is used to chemically alter a wide range of properties of two-dimensional layered α-MoO 3 . Intercalation modifies acoustic phonons and elastic constants, as measured with Brillouin scattering. Intercalation alters electronic bandgaps, color, structure, Raman shifts, and electron binding energies. Optical chemochromism is demonstrated with intercalants changing the color of MoO 3 from transparent to brilliant blue (In, Mo, Os, and Ru) and orange (Ag). Correlations are investigated among material properties. There is evidence that in-plane longitudinal stiffness c 11 correlates with changes in the bandgap, while various Raman modes appear to be connected to a variety of properties, including shear modulus c 55 , Mo binding energies, lattice constants, and the preferred crystal structure of the intercalant. The results indicate a surprising degree of complexity, suggesting competition among multiple distinct mechanisms and interactions involving specific intercalant species.

Aqueous battery with nonflammable and instinctive safe properties has received great attention. However, issues related to Zn anode such as side reactions and rampant dendrite growth hinder the long-term circulation of AZMBs. Herein, an ultrathin(35 nm) MoO 3 coating is deposited on the Zn anode by means of vacuum vapor deposition for the first time. Due to the peculiar layer structure of MoO 3 , insertion of Zn 2+ in Zn x MoO 3 acts as Zn 2+ ion conductor, which regulates Zn 2+ deposition in an ordered manner. Additionally, the MoO 3 coating can also inhibit the hydrogen evolution and corrosion reactions at the interface. Therefore, both Zn//MoO 3 @Cu asymmetric battery and Zn symmetric battery cells manage to deliver satisfactory electrochemical performances. The symmetric cell assembled with MoO 3 @Zn shows a significant long cycle life of more than 1600 h at a current density of 2 mA cm -2 . Meanwhile, the MoO 3 @Zn//Cu asymmetric cell exhibits an ultrahigh Zn deposition/stripping efficiency of 99.82% after a stable cycling of 650 h at 2 mA cm -2 . This study proposes a concept of "zincophile Zn 2+ conductor regulation" to dictate Zn electrodeposition and broadens novel design of vacuum evaporation for nano MoO 3 modified Zn anodes., (© 2024 Wiley‐VCH GmbH.)

Aqueous rechargeable proton batteries are attractive due to the small ionic radius, light mass, and ultrafast diffusion kinetics of proton as charge carriers. However, the commonly used acidic electrolyte is usually very corrosive to the electrode material, which seriously affects the cycle life of the battery. Here, it is proposed that decreasing water activity and limiting proton concentration can effectively prevent side reactions of the MoO 3 anode such as corrosion and hydrogen precipitation by using a lean-water hydrogel electrolyte. The as-prepared polyacrylamide (PAAM)-poly2-acrylamide-2-methylpropanesulfonic acid (PAMPS)/MnSO 4 (PPM) hydrogel electrolyte not only has abundant hydrophilic groups that can form hydrogen bonds with free water and inhibit solvent-electrode interaction, but also has fixed anions that can maintain a certain interaction with protons. The assembled MoO 3 ||MnO 2 full battery can stably cycle over 500 times for ≈350 h with an unprecedented capacity retention of 100% even at a low current density of 0.5 A g -1 . This work gives a hint that limiting free water as well as proton concentration is important for the design of electrolytes or interfaces in aqueous proton batteries., (© 2024 Wiley‐VCH GmbH.)

MoO 3 thin film was fabricated on an indium tin oxide substrate using the physical vapor deposition technique. X-ray diffraction and scanning electron microscopy study to investigate surface morphology, grain size, and surface structure, which are critical for absorbing solar spectra in water splitting for hydrogen energy generation. Ultraviolet-visible spectroscopy was used to confirm the absorption of solar spectra and the percentage of transmittance. Fourier-transform infrared analysis provided the functional groups present in the deposited thin film. The Tauc plot was used to determine the thin-film band gap, which allowed for the analysis of charge carrier transitions from the conduction band to the valence band. Electrochemical impedance spectroscopy investigations confirmed the charge transfer processes to the counter electrode and electrolyte interfaces. The observed low curve for MoO 3 indicated low resistance and allowed efficient charge transfer. Linear sweep voltammetry analysis was used to measure photocurrent and solar light to hydrogen emission when the thin film was exposed to solar spectra. The thin film's observed hydrogen emission rate was 3731.74 mol g -1 h -1 , and the STH% of MoO 3 was found to be 0.345% at 0.8 V. These findings highlight the promising potential of MoO 3 as a material for hydrogen energy generation using solar light., (© 2024 John Wiley & Sons Ltd.)

A flexible asymmetric supercapacitor (ASC) is successfully developed by using the composite of MoO 3 and graphene oxide (GO) electrochemically deposited on carbon cloth (CC) (MoO 3 /rGO/CC) as the cathode, the MnO 2 deposited on CC (MnO 2 /CC) as the anode, and Na 2 SO 4 /polyvinyl alcohol (PVA) as the gel electrolyte. The results show that the introduction of the GO layer can remarkably increase the specific capacitance of MoO 3 from 282.7 F g -1 to 341.0 F g -1 . Furthermore, the combination of such good electrode materials and a neutral gel electrolyte renders the fabrication of high-performance ASC with a large operating potential difference of 1.6 V in a 0.5 mol L -1 Na 2 SO 4 solution of water. Furthermore, the ASCs exhibit excellent cycle ability and the capacitance can maintain 87% of its initial value after 6000 cycles. The fact that a light-emitting diode can be lit up by the ASCs indicates the device's potential applications as an energy storage device. The encouraging results demonstrate a promising application of the composite of MoO 3 and GO in energy storage devices.

Chemical tunability of the elastic constants of α-MoO 3 , a two-dimensional layered oxide, is demonstrated with mutability on the order of tens of GPa, simply by choice of a metal intercalant including Au, Cr, Fe, Ge, Mn, and Ni. Using Brillouin laser light scattering from confined acoustic phonons in nanometer-thick materials, the in-plane angular dispersion of the quantized acoustic phonon branches of 2D layered, intercalated MoO 3 is measured and used to determine the bulk modulus ( K ), Young's moduli ( E 11 , E 22 , and E 33 ), each of the nine independent elastic tensor elements ( c ij ), and the thickness. Intercalation of metals generally reduces the anisotropy in MoO 3 except in Ge-MoO 3 , for which the in-plane longitudinal elastic anisotropy is unaffected. Chemochromism from transparent white (MoO 3 and Fe-MoO 3 ) to near black (Ni-MoO 3 ) to brilliant dark blue (Ge-MoO 3 ) is demonstrated and is associated with a reduction in electronic band gap with intercalation and an increase in absorption >600 nm for some intercalants (Cr-, Ge-, and Mn-MoO 3 ).

The rational design of inexpensive metal electrocatalysts with exciting catalytic activity for overall water splitting (OWS) remains a significant challenge. Heterostructures of NiFe layered double hydroxides (NiFe-LDHs) with abundant oxygen defects and tunable electronic properties have garnered considerable attention. Here, a self-supporting heterostructured catalyst (named MoO 3 /NiFe-NF) is synthesized via a hydrothermal method to grow NiFe-LDH with oxygen vacancies (O V ) in situ on inexpensive nickel foam (NF). Subsequently, MoO 3 is anchored and grown on the surface of NiFe-LDH by electrodeposition. The obtained catalysts achieved outstanding oxygen/hydrogen evolution reaction (OER/HER, 212 mV/85 mV@10 mA cm -2 ) performance in 1 m KOH. Additionally, when MoO 3 /NiFe-NF is utilized as the cathode and anode in OWS, a current density of 10 mA cm -2 can be obtained as an ultralow battery voltage of 1.43 V, a significantly lower value compared to the commercial electrolyzer incorporating Pt/C and IrO 2 electrode materials. Finally, density functional theory (DFT) calculations and advanced spectroscopy technology are conducted to reveal the effects of heterojunctions and O V on the internal electronic structure of the electrical catalysts. Mainly, the present study provides a novel tactic for the rational design of remarkable, low-cost NiFe-LDH electrocatalysts with heterostructures for OWS., (© 2023 Wiley‐VCH GmbH.)

Nanostructures have been used for various biomedical applications due to their optical, antibacterial, magnetic, antioxidant, and biocompatible properties. Cancer is a prevalent disease that severely threatens human life and health. Thus, innovative and effective therapeutic approaches are urgently required for cancer. Photothermal therapy (PTT) is a promising approach to killing cancer cells. In this investigation, we developed a low-cost, simple, green technique to fabricate molybdenum trioxide nanostructures (MNs) using Opuntia ficus-indica mucilage as a template. Moreover, the MNs were functionalized with folic acid (FA) for cancer PTT. The X-ray diffractometer results revealed that the prepared MNs have an orthorhombic crystal phase. The transmission electron microscope image of MNs shows a flake shape with 20-150 nm diameter. The cytotoxicity of MNs and FA-conjugated MNs was studied in vitro. These cell viability assay results suggested that fabricated MoO 3 nanostructures reduced 25% of cell viability in MCF-7 cells, even at high doses. However, even with high-dose treatment, FA/MNs do not cause significant cell death. Acridine orange/ethidium bromide (AO/EB) staining revealed DNA and chromatin condensation in MCF-7 cells exposed to MNs. Overall, the in vitro study results suggested that FA/MNs have excellent biocompatibility, which applies to biomedical applications. MNs dispersion temperature gradually increases from 26 to 58°C under 808 nm laser irradiation. We found significant mortality rates after NIR irradiation in MNs- or FA/MNs-treated MCF-7 cells. These findings suggest that FA/MNs can be used as an effective photothermal agent to treat breast cancer., (© 2023 International Union of Biochemistry and Molecular Biology, Inc.)

MoS 2 is a two-dimensional layered transition metal dichalcogenide with unique electronic and optical properties. The fabrication of ultrathin MoS 2 is vitally important, since interlayer interactions in its ultrathin varieties will become thickness-dependent, providing thickness-governed tunability and diverse applications of those properties. Unlike with a number of studies that have reported detailed information on direct bandgap emission from MoS 2 monolayers, reliable experimental evidence for thickness-induced evolution or transformation of the indirect bandgap remains scarce. Here, the sulfurization of MoO 3 thin films with nominal thicknesses of 30 nm, 5 nm and 3 nm was performed. All sulfurized samples were examined at room temperature with spectroscopic ellipsometry and photoluminescence spectroscopy to obtain information about their dielectric function and edge emission spectra. This investigation unveiled an indirect-to-indirect crossover between the transitions, associated with two different Λ and K valleys of the MoS 2 conduction band, by thinning its thickness down to a few layers.

The development of bifunctional catalysts that facilitate both the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) in alkaline environment is crucial for realizing unitized regenerative anion-exchange membrane fuel cells. In this study, a novel strategy to modulate the electron density of MoO 3 through Ni doping (sample named Ni x Mo 1- x O 3 ) is reported. Ni is incorporated to replace Mo atoms in MoO 3 . Specifically, Ni x Mo 1- x O 3 is combined with optimal adsorption energy, along with MoO 2 /Mo 2 N hybrid with high conductivity. The resulting Ni x Mo 1- x O 3 supported on MoO 2 /Mo 2 N hybrid (sample named as Ni x Mo 1- x O 3 -H) exhibits excellent alkaline HER activity, with an overpotential of only 16 mV at 10 mA cm -2 and a Tafel slope of 54 mV dec -1 . In addition, the Ni x Mo 1- x O 3 -H demonstrates an ultrahigh HOR performance with a high exchange current density (3.852 mA cm -2 ). The catalyst's breakdown potential of 0.23 V indicates its ability to withstand higher voltages without breaking down. As evidenced by the results, this characteristic leads to improved stability. These results are higher than those of the other catalysts reported, which indicates that the electron density of MoO 3 can be effectively modulated through Ni doping, leading to excellent HER and HOR performance., (© 2023 Wiley-VCH GmbH.)

Layered molybdenum trioxide (MoO 3 ) is being investigated as a cathode material with high theoretical capacity and holds promise for aqueous secondary batteries. Unfortunately, the severe structural degradation of MoO 3 and insufficient intrinsic properties hinder its practical application. Herein, a Na + preintercalation strategy is reported as an effective method to construct cathodes with high performance for aqueous zinc/sodium batteries (AZSBs). Compared with pristine MoO 3 , the Na + preintercalated Na 0.25 MoO 3 cathode delivers a reversible capacity of 251.1 mAh g -1 at 1 A g -1 , achieves a capacity retention of 79.2% after 500 cycles, and exhibits a high rate capability (121.5 mAh g -1 at 20 A g -1 ), which is superior to that in most of the previous reports. Through the experimental measurements and density functional theory (DFT) calculations, the preintercalation method could shorten the forbidden band gap and modulate the electronic structure and hence effectively inhibit the structural collapse of MoO 3 microrods, induce reversible Na + insertion, and enhance the discharge potential. This work is of significance for further research on molybdenum-based compounds as cathode materials for aqueous secondary batteries.

Field-effect transistor-based biosensors have gained increasing interest due to their reactive surface to external stimuli and the adaptive feedback required for advanced sensing platforms in biohybrid neural interfaces. However, complex probing methods for surface functionalization remain a challenge that limits the industrial implementation of such devices. Herein, a simple, label-free biosensor based on molybdenum oxide (MoO 3 ) with dopamine-regulated plasticity is demonstrated. Dopamine oxidation facilitated locally at the channel surface initiates a charge transfer mechanism between the molecule and the oxide, altering the channel conductance and successfully emulating the tunable synaptic weight by neurotransmitter activity. The oxygen level of the channel is shown to heavily affect the device's electrochemical properties, shifting from a nonreactive metallic characteristic to highly responsive semiconducting behavior. Controllable responsivity is achieved by optimizing the channel's dimension, which allows the devices to operate in wide ranges of dopamine concentration, from 100 nM to sub-mM levels, with excellent selectivity compared with K + , Na + , and Ca 2+ .

In this work, copper nickel tin sulfide (Cu 2 NiSnS 4 ) as an encouraging alternative absorber for thin-film photovoltaic devices is explored. Here, the Cu 2 NiSnS 4 (CNTS) absorber-based heterojunction solar cell is designed through a two-stage theoretical approach using Solar Cell Capacitance Simulator in one-dimension (SCAPS-1D). Initially four different hole transport materials (MoO 3 , SnS, NiO x , and PEDOT.PSS) are incorporated at the back interface in experimentally configured Au/Cu 2 NiSnS 4 /ZnS/ZnO/ITO cell to boost the device outputs. The MoO 3 semiconductor is anticipated as a hole transport layer (HTL) in the heterojunction Ni/MoO 3 /Cu 2 NiSnS 4 /ZnS/ZnO/ITO solar configuration. It is revealed that an appropriate band alignment can be formed at MoO 3 /Cu 2 NiSnS 4 interface with less interfacial defects among other HTLs with CNTS absorber, thus improving the solar cell outputs. Efficiency is increased from 2.71% to 8.79% for the proposed CNTS-based solar cell. Further optimization is accomplished concerning thickness, defect states, and doping density of the various materials utilized in the heterojunction structure. Defect characteristics at the MoO 3 /Cu 2 NiSnS 4 and Cu 2 NiSnS 4 /ZnS interfaces are also evaluated and optimized to boost the conversion efficiency significantly. Moreover, the effects of operating temperature and rear electrode work function on the outputs of the designed solar device are studied. The aforesaid two-stage optimization yields efficiency of 12.46% with V OC of 1.23 V, J SC of 12.66 mA/cm 2 , and FF of 79.78%. Therefore, these findings will facilitate the scientific communities to further progress an economical and extremely efficient CNTS-based solar device with a promising MoO 3 HTL., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

A highly uniform spherical MoO 2 -MoO 3 /polypyrrole core-shell nanocomposite has been successfully synthesized as an optoelectronic photon sensing material, capable of detecting light in the UV, Vis, and IR domains. The nanocomposite is prepared through the oxidation of pyrrole using Na 2 MoO 4 , resulting in a uniform spherical morphology that has been confirmed by TEM, theoretical modeling, and SEM analyses. This morphology contributes to its promising optical behavior, characterized by a small bandgap of 1.36 eV. The optoelectronic photosensing capability of the nanocomposite has been evaluated across the UV, Vis, and IR spectra, demonstrating high efficiency. The photoresponsivity R values indicate the ability of the nanocomposite to generate hot electrons in response to incident photons. With an R value of 4.15 mA·W -1 at 440 nm, this optoelectronic device exhibits considerable promise for integration into an advanced technological apparatus. The detection (D) value of 9.30 × 10 8 Jones at 440 nm further confirms the high sensitivity in the Vis region. The excellent stability of the device can be attributed to the inherent MoO 2 -MoO 3 oxide and Ppy polymer materials. This stability has been demonstrated through reproducibility studies and current-voltage measurements under various optical conditions. The combination of stability, efficiency, and sensitivity makes this optoelectronic device well suited for light sensing applications in both industrial and commercial settings. Its promising performance opens up opportunities for advancements in various fields requiring accurate and reliable light detection.

Interfaces between functional layers in perovskite solar cells (PSCs) are of paramount importance in determining their efficiency and stability, but the interaction and stability of metal-hole conductor (HC) interfaces have received less attention. Here, we discover an intriguing transient behavior in devices which induces a profound efficiency fluctuation from 9 to 20% during the initial performance testing. Air exposure (e.g., oxygen and moisture) can significantly accelerate this nonequilibrium process and simultaneously enhance the device maximal efficiency. Structural analysis reveals that the chemical reaction between Ag and HC occurred during the metal deposition by thermal evaporation, leading to the formation of an insulating barrier layer at their interfaces, which results in a high charge-transport barrier and poor device performance. Accordingly, we propose a metal diffusion-associated barrier evolution mechanism to understand the metal/HC interfaces. To mitigate these detrimental effects, we strategically develop an interlayer strategy by introducing an ultrathin layer of molybdenum oxide (MoO 3 ) between Ag and HC, which is found to effectively suppress the interfacial reaction, yielding highly reliable PSCs with instant high efficiency. This work provides new insights into understanding the metal-organic interfaces, and the developed interlayer strategy can be generally applicable to engineer other interfaces in realizing efficient and stable contacts.

MoO 3 and MoO 2 systems have attracted particular attention for many widespread applications thanks to their electronic and optical peculiarities; from the crystallographic point of view, MoO 3 adopts a thermodynamically stable orthorhombic phase (α-MoO 3 ) belonging to the space group Pbmn , while MoO 2 assumes a monoclinic arrangement characterized by space group P 2 1 / c. In the present paper, we investigated the electronic and optical properties of both MoO 3 and MoO 2 by using Density Functional Theory calculations, in particular, the Meta Generalized Gradient Approximation (MGGA) SCAN functional together with the PseudoDojo pseudopotential, which were used for the first time to obtain a deeper insight into the nature of different Mo-O bonds in these materials. The calculated density of states, the band gap, and the band structure were confirmed and validated by comparison with already available experimental results, while the optical properties were validated by recording optical spectra. Furthermore, the calculated band-gap energy value for the orthorhombic MoO 3 showed the best match to the experimental value reported in the literature. All these findings suggest that the newly proposed theoretical techniques reproduce the experimental evidence of both MoO 2 and MoO 3 systems with high accuracy.

Ultrathin MoO 3 semiconductor nanostructures have garnered significant interest as a promising nanomaterial for transparent nano- and optoelectronics, owing to their exceptional reactivity. Due to the shortage of knowledge about the electronic and optoelectronic properties of MoO 3 / n -Si via an ALD system of few nanometers, we utilized the preparation of an ultrathin MoO 3 film at temperatures of 100, 150, 200, and 250 °C. The effect of the depositing temperatures on using bis(tbutylimido)bis(dimethylamino)molybdenum (VI) as a molybdenum source for highly stable UV photodetectors were reported. The ON-OFF and the photodetector dynamic behaviors of these samples under different applied voltages of 0, 0.5, 1, 2, 3, 4, and 5 V were collected. This study shows that the ultrasmooth and homogenous films of less than a 0.30 nm roughness deposited at 200 °C were used efficiently for high-performance UV photodetector behaviors with a high sheet carrier concentration of 7.6 × 10 10 cm -2 and external quantum efficiency of 1.72 × 10 11 . The electronic parameters were analyzed based on thermionic emission theory, where Cheung and Nord's methods were utilized to determine the photodetector electronic parameters, such as the ideality factor ( n ), barrier height (Φ 0 ), and series resistance (R s ). The n -factor values were higher in the low voltage region of the I-V diagram, potentially due to series resistance causing a voltage drop across the interfacial thin film and charge accumulation at the interface states between the MoO 3 and Si surfaces.

Spatial hindrance of lithium polysulfide (LiPS) diffusion by inserting a barrier interlayer has been deemed as an effective strategy to restrict the shuttle effect in lithium-sulfur batteries (LSBs). However, the extra interlayer without reversible capacity production inevitably reduces the actual energy density of the battery. Herein, a freestanding α-MoO 3 nanobelt interlayer with the decoration of TiN nanoparticles and carbon nanotubes (denoted as MCT) is established. To investigate the capacity compensation effect of the MCT during cell operations, X-ray absorption near-edge spectrometry is conducted. It is revealed that MoO 3 can sustain a reversible Li intercalation/deintercalation in a voltage range of 1.8-2.8 V, providing 180 mAh g -1 of extra capacity for compensating sulfur cathode. In addition, the adsorption of the lithiated α-MoO 3 toward LiPSs is further evaluated. By matching a high-loading sulfur cathode (3.0 mg cm -2 ), a superior capacity of 713.3 mAh g -1 can be retained after 100 cycles under the MCT assistance.

Hydrogen production as a source of clean energy is high in demand nowadays to avoid environmental issues originating from the use of conventional energy sources i.e., fossil fuels. In this work and for the first time, MoO 3 /S@g-C 3 N 4 nanocomposite is functionalized for hydrogen production. Sulfur@graphitic carbon nitride (S@g-C 3 N 4 )-based catalysis is prepared via thermal condensation of thiourea. The MoO 3 , S@g-C 3 N 4 , and MoO 3 /S@g-C 3 N 4 nanocomposites were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FESEM), STEM, and spectrophotometer. The lattice constant (a = 3.96, b = 13.92 Å) and the volume (203.4 Å 3 ) of MoO 3 /10%S@g-C 3 N 4 were found to be the highest compared with MoO 3 , MoO 3 /20-%S@g-C 3 N 4 , and MoO 3 /30%S@g-C 3 N 4 , and that led to highest band gap energy of 4.14 eV. The nanocomposite sample MoO 3 /10%S@g-C 3 N 4 showed a higher surface area (22 m 2 /g) and large pore volume (0.11 cm 3 /g). The average nanocrystal size and microstrain for MoO 3 /10%S@g-C 3 N 4 were found to be 23 nm and -0.042, respectively. The highest hydrogen production from NaBH 4 hydrolysis ~22,340 mL/g·min was obtained from MoO 3 /10%S@g-C 3 N 4 nanocomposites, while 18,421 mL/g·min was obtained from pure MoO 3 . Hydrogen production was increased when increasing the masses of MoO 3 /10%S@g-C 3 N 4 .

The growing demand for electricity has increased the interest of the researchers towards exploration of energy storing devices (ESDs). With the motif for developing electrochemical energy storage devices, this research work is focussed on the study of MoO 3 nanoparticles and its doping with chromium as an efficient electrode material for energy storage applications. The nanoparticles were synthesized by hydrothermal method and were examined by powder X-ray diffraction, which determined the thermodynamically stable orthorhombic phase of MoO 3 , and their morphologies were examined using scanning electron microscopy displaying flake-like structures. The typical vibrational bands of Mo-O were identified from Infra-red and Raman spectral analysis. The ultra violet diffuse reflectance spectra revealed the decrease in optical band gap after doping with chromium. The temperature dependent AC and DC conductivities were enhanced on doping. Electrochemical behaviour of the nanoparticles was probed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) measurements and galvanostatic charge-discharge (GCD) analysis for which specific capacitance ( C sp ) value of 334 Fg -1 was achieved for Cr-doped MoO 3 nanoparticles. The electrochemical performance of the sample was found to be increased after doping with Cr., Competing Interests: Conflict of interestThe authors declare no competing interests., (© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2022, Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.)

Metal oxides are commonly used in optoelectronic devices due to their transparency and excellent electrical conductivity. Based on its physical properties, each metal oxide serves as the foundation for a unique device. In this study, we opt to determine and assess the physical properties of MoO 3 metal oxide. Accordingly, the optical and electronic parameters of MoO 3 are evaluated using DFT (Density Functional Theory), and PBE and HSE06 functionals were mainly used in the calculation. It was found that the band structure of MoO 3 calculated using PBE and HSE06 exhibited indirect semiconductor properties with the same line quality. Its band gap was 3.027 eV in HSE06 and 2.12 eV in PBE. Electrons and holes had effective masses and mobilities of 0.06673, -0.10084, 3811.11 cm 2 V -1 s -1 and 1630.39 cm 2 V -1 s -1 , respectively. In addition, the simulation determined the dependence of the real and imaginary components of the complex refractive index and permittivity of MoO 3 on the wavelength of light, and a value of 58 corresponds to the relative permittivity. MoO 3 has a refractive index of between 1.5 and 3 in the visible spectrum, which can therefore be used as an anti-reflection layer for solar cells made from silicon. In addition, based on the semiconducting properties of MoO 3 , it was estimated that it could serve as an emitter layer for a solar cell containing silicon. In this work, we calculated the photoelectric parameters of the MoO3/Si heterojunction solar cell using Sentaurus TCAD (Technology Computing Aided Design). According to the obtained results, the efficiency of the MoO 3 /Si solar cell with a MoO 3 layer thickness of 100 nm and a Si layer thickness of 9 nm is 8.8%, which is 1.24% greater than the efficiency of a homojunction silicon-based solar cell of the same size. The greatest short-circuit current for a MoO 3 /Si heterojunction solar cell was observed at a MoO 3 layer thickness of 60 nm, which was determined by studying the dependency of the heterojunction short-circuit current on the thickness of the MoO 3 layer.

We propose that the crystallinity of two-dimensional (2D) materials is a crucial factor for achieving highly effective work function (WF) modification. A crystalline 2D MoO 3 monolayer enhances substrate WF up to 6.4 eV for thicknesses as low as 0.7 nm. Such a high WF makes 2D MoO 3 a great candidate for tuning properties of anode materials and for the future design of organic electronic devices, where accurate evaluation of the WF is crucial. We provide a detailed investigation of WF of 2D α-MoO 3 directly grown on highly ordered pyrolytic graphite, by means of Kelvin probe force microscopy (KPFM) and ultraviolet photoemission spectroscopy (UPS). This study underlines the importance of a controlled environment and the resulting crystallinity to achieve high WF in MoO 3 . UPS is proved to be suitable for determining higher WF attributed to 2D islands on a substrate with lower WF, yet only in particular cases of sufficient coverage. KPFM remains a method of choice for nanoscale investigations, especially when conducted under ultrahigh vacuum conditions. Our experimental results are supported by density functional theory calculations of electrostatic potential, which indicate that oxygen vacancies result in anisotropy of WF at the sides of the MoO 3 monolayer. These novel insights into the electronic properties of 2D-MoO 3 are promising for the design of electronic devices with high WF monolayer films, preserving the transparency and flexibility of the systems.

Two-dimensional van der Waals crystals (2D vdW) are recognized as one of the potential materials to solve the physical limits caused by size scaling. Here, vdW metal oxide MoO 3 is applied with the gate dielectric in a 2D field-effect transistor (FET). Due to its high dielectric constant and the good response of MoS 2 to visible light, we obtained a field effect transistor for photodetection. In general, the device exhibits a threshold voltage near 0 V, Ion/Ioff ratio of 10 5 , electron mobility about 85 cm 2 V -1 s -1 and a good response to visible light, the responsivity is near 5 A/W at low laser power, which shows that MoO 3 is a potential material as gate dielectric.

Topographic essential synthesis of nanomaterials by adjusting easy preparatory factors is an effective way to improve a variety of nanostructured materials. The SILAR technique is used to evaluate the manufacturing samples of MoO 3 , TiO 2 , and MoTiO 5 nanostructures. These nanostructures of MoO 3 , TiO 2 , and MoTiO 5 are used as electrode materials in photovoltaic systems. The link between photoelectrochemical characteristics and MoO 3 , TiO 2 , and MoTiO 5 nanostructures is studied in depth. The photoelectrochemical characteristics of MoO 3 , TiO 2 , and MoTiO 5 nanostructures are discovered to be highly dependent. At a 5mV/s scan rate, the photocurrent of MoO 3 , TiO 2 , and MoTiO 5 electrodes surged fast when sunlight was turned on, reaching values of 1.03 mA cm -2 , 1.68 mA cm -2 , and 14.20 mA cm -2 , respectively. As soon as the solar illumination was turned off, the photocurrent value dropped to zero. Photocurrent transitions showed a quick, homogeneous photocurrent counterpart; this suggested that charge transfer in these ingredients is speedy and possibly related to the crystal buildings of MoO 3 , TiO 2, and MoTiO 5 . MoTiO 5 nano-belt and nano-disc thin films have typical uses in the photoelectrochemical sector because they have the best photoresponse and stability., (© TÜBİTAK.)

By doping of MoO 3 to MoS 2-E , MoO 3 /MoS 2-E composite was produced to treat the antimony (Sb +5 ) from raw petrochemical industry wastewater. The effects of increasing MoO 3 /MoS 2-E composite concentrations (0.01, 0.06, 0.50, 1.20, and 6 mg/L), times (5 min, 10 min, 20 min, 60 min, 80 min), and simulated sun light powers (2, 15, and 26 mW/m 2 ) on the removal of Sb +5 was researched. According to X-ray diffraction (XRD), MoS 2-E exhibited a pure hexagonal structure with peaks at 2Ɵ data of 15.56, 33.78, 40.59, and 61.43 cm -1 while MoO 3 peaks showed similar configuration with the orthorhombic stage. X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical composition. After Sb +5 removal, the additional MoO 3 peaks were determined at 680, 967, and 997 cm -1 . XPS spectra showed that after an oxidation period, "MoS 2-E " was generated. Binding energy analysis showed that Mo 5+ ions were produced from the partial transformation of MoO 3. The MoO 3 exhibited a vertical stacking on the MoS 2-E . The filtered MoS 2-E graph and relevant fast Fourier transfer pictures showed octahedral phase containing a proton. Field emission scanning electron microscopy analysis results showed that nano MoO 3 exhibited a nanobelt structure. The maximum 10 mg/L Sb +5 removal was 93% at 1.20 mg/L MoO 3 /MoS 2-E composite concentration at pH = 9 after 20 min at 15 mW/m 2 simulated sunlight power via photoelectrocatalysis while the maximum Sb +5 removal via adsorption was detected as 80% for the same operational conditions in unilluminated conditions., (© TÜBİTAK.)

We explore a phase engineering strategy to improve the electrochemical performance of transition metal sulfides (TMSs) in anode materials for lithium-ion batteries (LIBs). A one-pot hydrothermal approach has been employed to synthesize MoS 2 nanostructures. MoS 2 and MoO 3 phases can be readily controlled by straightforward calcination in the (200-300) °C temperature range. An optimized temperature of 250 °C yields a phase-engineered MoO 3 @MoS 2 hybrid, while 200 and 300 °C produce single MoS 2 and MoO 3 phases. When tested in LIBs anode, the optimized MoO 3 @MoS 2 hybrid outperforms the pristine MoS 2 and MoO 3 counterparts. With above 99% Coulombic efficiency (CE), the hybrid anode retains its capacity of 564 mAh g -1 after 100 cycles, and maintains a capacity of 278 mAh g -1 at 700 mA g -1 current density. These favorable characteristics are attributed to the formation of MoO 3 passivation surface layer on MoS 2 and reactive interfaces between the two phases, which facilitate the Li-ion insertion/extraction, successively improving MoO 3 @MoS 2 anode performance.

Among transition metal oxides, MoO 3 is a promising material due to its layered structure and different oxidation states, making it suitable for different device applications. One of the methods used to grow MoO 3 is radio frequency magnetron sputtering (RFMS), which is the most compatible method in industry. However, obtaining nanostructures by RFMS for metal oxides is challenging because of compact morphology film formation. In this study, α-MoO 3 with vertical nanowalls is obtained by a two-step process; deposition of magnetron-sputtered MoS 2 vertical nanowalls and postoxidation of these structures without changing the morphology. In situ transmittance and electrical measurements are performed to control the oxidation process, which shed light on understanding the oxidation of MoS 2 nanowalls. The transition from MoS 2 to α-MoO 3 is investigated with partially oxidized MoS 2 /MoO 3 samples with different thicknesses. It is also concluded that oxidation starts from nanowalls perpendicular to the substrate and lasts with oxidation of basal planes. Four different thicknesses of α-MoO 3 nanowall samples are fabricated for H 2 gas sensors. Also, the effect of Pd deposition on the H 2 -sensing properties of sensors is deeply investigated. An outstanding response of 3.3 × 10 5 as well as the response and recovery times of 379 and 304 s, respectively, are achieved from the thinnest Pd-loaded sample. Also, the gas-sensing mechanism is explored by gasochromic measurements to investigate the sensor behaviors under the conditions of dry air and N 2 gas as the carrier gas.

A capacitance increase phenomenon is observed for MoO 3 electrodes synthesized via a sol-gel process in the presence of dopamine hydrochloride (Dopa HCl) as compared to α-MoO 3 electrodes in 5M ZnCl 2 aqueous electrolyte. The synthesis approach is based on a hydrogen peroxide-initiated sol-gel reaction to which the Dopa HCl is added. The powder precursor (Dopa) x MoO y , is isolated from the metastable gel using freeze-drying. Hydrothermal treatment (HT) of the precursor results in the formation of MoO 3 accompanied by carbonization of the organic molecules; designated as HT-MoO 3 /C. HT of the precipitate formed in the absence of dopamine in the reaction produced α-MoO 3 , which was used as a reference material in this study (α-MoO 3 -ref). Scanning electron microscopy (SEM) images show a nanobelt morphology for both HT-MoO 3 /C and α-MoO 3 -ref powders, but with distinct differences in the shape of the nanobelts. The presence of carbonaceous content in the structure of HT-MoO 3 /C is confirmed by FTIR and Raman spectroscopy measurements. X-ray diffraction (XRD) and Rietveld refinement analysis demonstrate the presence of α-MoO 3 and h-MoO 3 phases in the structure of HT-MoO 3 /C. The increased specific capacitance delivered by the HT-MoO 3 /C electrode as compared to the α-MoO 3 -ref electrode in 5M ZnCl 2 electrolyte in a -0.25-0.70 V vs. Ag/AgCl potential window triggered a more detailed study in an expanded potential window. In the 5M ZnCl 2 electrolyte at a scan rate of 2 mV s -1 , the HT-MoO 3 /C electrode shows a second cycle capacitance of 347.6 F g -1 . The higher electrochemical performance of the HT-MoO 3 /C electrode can be attributed to the presence of carbon in its structure, which can facilitate electron transport. Our study provides a new route for further development of metal oxides for energy storage applications., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Norouzi, Omo-Lamai, Alimohammadi, Averianov, Kuang, Yan, Wang, Stavitski, Leshchev, Takeuchi, Takeuchi, Marschilok, Bock and Pomerantseva.)

An HfC-doped molybdenum (Mo-Hf-C; MHC) alloy was prepared via a powder metallurgy process, including dry direct doping followed by ball-milling, cold-isotactic-pressing, and vacuum sintering. An oxidation comparison experiment was conducted, and the oxidation and volatilization behaviors were analyzed using the mass change, volatile generation rate, and morphology transformation. The results show that relatively uniform powder morphology can be obtained by the direct doping of carbide and high-energy ball milling. The oxidation of the MHC alloy at a lower temperature was characterized by the oxygen-absorption and a slight weight gain, while at a higher temperature and longer holding time, it was characterized by the mass volatile weight loss. A significant weight change appeared at 800 °C for 30 min with a weight loss rate of 4.8%. Surface oxidation products developed horizontally from ridged oxides at lower temperature stages to a flaky oxide layer at higher temperatures. The peeling of the oxide layer was the result of interfacial pore development, which led to exposure of the alloy matrix and further oxidation. Based on the oxidation and volatilization characteristics of HfC-doped MHC alloys, we conclude that the oxidation and volatilization of the MHC alloy conformed to the general law; however, the significant weight loss temperature, weight loss rate, volatilization temperature, and volatilization rate were improved compared with pure molybdenum and traditional molybdenum alloys, thus, indicating that the precipitation of the second phase HfC particles at the grain boundaries and within the grains can inhibit the oxidation and volatilization of matrix elements to a certain extent.

The intrinsic stability of the 5 V LiCoPO 4 -LiCo 2 P 3 O 10 thin-film (carbon-free) cathode material coated with MoO 3 thin layer is studied using a comprehensive synchrotron electron spectroscopy in situ approach combined with first-principle calculations. The atomic-molecular level study demonstrates fully reversible electronic properties of the cathode after the first electrochemical cycle. The polyanionic oxide is not involved in chemical reactions with the fluoroethylene-containing liquid electrolyte even when charged to 5.1 V vs Li + /Li. The high stability of the cathode is explained on the basis of the developed energy level model. In contrast, the chemical composition of the cathode-electrolyte interface evolves continuously by involving MoO 3 in the decomposition reaction with consequent leaching of oxide from the surface. The proposed mechanisms of chemical reactions are attributed to external electrolyte oxidation via charge transfer from the relevant electron level to the MoO 3 valence band state and internal electrolyte oxidation via proton transfer to the solvents. This study provides a deeper insight into the development of both a doping strategy to enhance the electronic conductivity of high-voltage cathode materials and an efficient surface coating against unfavorable interfacial chemical reactions.

In situ environmental transmission electron microscope (ETEM) could provide intuitive and solid proof for the local structure and chemical evolution of materials under practical working conditions. In particular, coupled with atmosphere and thermal field, the behavior of nano catalysts could be directly observed during the catalytic reaction. Through the change of lattice structure, it can directly correlate the relationship between the structure, size and properties of materials in the nanoscale, and further directly and accurately, which is of great guiding value for the study of catalysis mechanism and the optimization of catalysts. As an outstanding catalytic material in the application of methane reforming, molybdenum oxide (MoO 3 )-based materials and its deoxidation process were studied by in situ ETEM method. The corresponding microstructures and components evolution were analyzed by diffraction, high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectrum (EELS) techniques. MoO 3 had a good directional deoxidation process accompanied with the process of nanoparticles crushing and regrowth in hydrogen (H 2 ) and thermal field. However, in the absence of H 2 , the samples would exhibit different structural evolution.

Molybdenum-based materials have been intensively investigated for high-performance gas sensor applications. Particularly, molybdenum oxides and dichalcogenides nanostructures have been widely examined due to their tunable structural and physicochemical properties that meet sensor requirements. These materials have good durability, are naturally abundant, low cost, and have facile preparation, allowing scalable fabrication to fulfill the growing demand of susceptible sensor devices. Significant advances have been made in recent decades to design and fabricate various molybdenum oxides- and dichalcogenides-based sensing materials, though it is still challenging to achieve high performances. Therefore, many experimental and theoretical investigations have been devoted to exploring suitable approaches which can significantly enhance their gas sensing properties. This review comprehensively examines recent advanced strategies to improve the nanostructured molybdenum-based material performance for detecting harmful pollutants, dangerous gases, or even exhaled breath monitoring. The summary and future challenges to advance their gas sensing performances will also be presented., (© 2021. The Author(s).)

Two-dimensional (2D) van der Waals (vdW) heterostructures currently have attracted much attention in widespread research fields where semiconductor materials are key. With the aim of gaining insights into photocatalytic materials, we use density functional theory (DFT) calculations within the HSE06 functional to analyze the evolution of optoelectronic properties and high-frequency dielectric constant profiles of various 2D MoO 3- x S x /MoS 2 heterostructures modified by chemical and physical approaches. Although the MoO 3 /MoS 2 heterostructure is a type III heterojunction associated with a metallic character, we found that exchanging the terminal oxo atoms of the MoO 3- x S x single layer (SL) with sulfur enables shifting its CB position above the VB position of the MoS 2 SL. This trend gives rise to a type II heterojunction where the band gap and charge transfer within the two layers are driven continuously by the S concentration in the MoO 3- x S x SL. This fine-tuning leads to a versatile type II heterostructure proposed to provide a direct Z-scheme system valuable for photocatalytic water splitting.

In this work, the multilevel resistive random access memories (RRAMs) have been achieved by using the structure of Pt/MoO 3 /Hf/MoO 3 /Pt with four stable resistance states. The devices show good retention property of each state (>10 4 s) and large memory window (>10 4 ). The simulation and experimental study reveal that the resistive switching mechanism is ascribed to combination of the conductive filament in the stack of MoO 3 /Hf next to the top electrode and redox reaction at the interface of Hf/MoO 3 next to bottom electrode. The fitting results of current-voltage characteristics under low sweep voltage indicate that the conduction of HRSs is dominated by the Poole-Frenkel emission and that of LRS is governed by the Ohmic conduction. Based on the RRAM, the tunable high-pass filter (HPF) with configurable filtering characteristics has been realized. The gain-frequency characteristics of the programmable HPF show that the filter has high resolution and wide programming range, demonstrating the viability of the multilevel RRAMs for future spiking neural network and shrinking the programmable filters with low power consumption., (© 2021 IOP Publishing Ltd.)

It's highly significant to develop a novel catalyst, which can be active at a wide range of pH, for an effective photo-Fenton reaction. In this work, α-FeOOH-MoO 3 nanorod was prepared by a one-step hydrothermal method and applied in photo-Fenton degradation of organic pollutants. Benefit from the electron migration mechanism of Z-scheme and excellent photoelectric performance, the catalyst exhibited superior photo-Fenton activity in degradation of organic pollutants. In addition, the catalyst holds good stability after 5 recycles. These results demonstrated that this catalyst has wide application prospect in organic wastewater treatment., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report on the MoO 3 oxides and their derivatives on microscopic 2H MoS 2 flakes oxidized in air and high relative humidity at a moderate temperature range below 410 °C. We combine XPS and AFM measurements such as topography, friction, creation of nanoscale ripples and scratches on the MoS 2 flakes deposited on Si substrates. We detect MoO 3 oxides mostly by measuring selected nanomechanical properties of the MoO 3 layer, such as its compressive mechanical stress at the plastic yield. We discuss basal surface coverage of the single MoS 2 flakes by the MoO 3 oxides. We discuss conditions for appearance of all possible MoO 3 oxide derivatives, such as molybdenum(VI) hydroxyoxides and MoO 3 hydrates. Our findings agree with an expected mechanistic switch in thermal oxidation in water vapors vs. air.

Considering that two-dimensional (2D) molybdenum trioxide has acquired more attention in the last few years, it is relevant to speed up thickness identification of this material. We provide two fast and non-destructive methods to evaluate the thickness of MoO 3 flakes on SiO 2 /Si substrates. First, by means of quantitative analysis of the apparent color of the flakes in optical microscopy images, one can make a first approximation of the thickness with an uncertainty of ±3 nm. The second method is based on the fit of optical contrast spectra, acquired with micro-reflectance measurements, to a Fresnel law-based model that provides an accurate measurement of the flake thickness with ±2 nm of uncertainty.

As a typical n-type semiconductor, MoO 3 has been widely applied in the gas-detection field due to its competitive physicochemical properties and ecofriendly characteristics. Volatile organic compounds (VOCs) are harmful to the atmospheric environment and human life, so it is necessary to quickly identify the presence of VOCs in the air. This review briefly introduced the application progress of an MoO 3 -based sensor in VOCs detection. We mainly emphasized the optimization strategies of a high performance MoO 3 , which consists of morphology-controlled synthesis and electronic properties functional modification. Besides the general synthesis methods, its gas-sensing properties and mechanism were briefly discussed. In conclusion, the application status of MoO 3 in gas-sensing and the challenges still to be solved were summarized., (Copyright © 2020 Wang, Zhou, Peng, Xu and Zeng.)

Organic solar cells (OSCs) are promising renewable energy sources for replacing fossil fuels. The power conversion efficiency (PCE) of OSCs has increased based on tremendous effort in material and device engineering. Still, the stability of OSC, such as long lifetime, negative temperature coefficient, must be enhanced for commercialization. In this study, we investigated OSC performance at a high operating temperature near 300-420 K, which are typical temperature regions in photovoltaic applications, with a different hole-extraction layer (HEL). The metal oxide-based HEL, MoO 3 , exhibited stable operating properties with a PCE drop rate of -0.13%/°C, as compared to polymeric HEL, PEDOT:PSS (-0.20%/°C). This performance reduction of polymeric HEL originated from the degradation of the interface in contact with PEDOT:PSS, as compared to the robust inorganic metal oxide HEL.

In this work, we investigate the surface transfer doping process that is induced between hydrogen-terminated (100) diamond and the metal oxides, MoO 3 and V 2 O 5 , through simulation using a semi-empirical Density Functional Theory (DFT) method. DFT was used to calculate the band structure and charge transfer process between these oxide materials and hydrogen terminated diamond. Analysis of the band structures, density of states, Mulliken charges, adsorption energies and position of the Valence Band Minima (VBM) and Conduction Band Minima (CBM) energy levels shows that both oxides act as electron acceptors and inject holes into the diamond structure. Hence, those metal oxides can be described as p-type doping materials for the diamond. Additionally, our work suggests that by depositing appropriate metal oxides in an oxygen rich atmosphere or using metal oxides with high stochiometric ration between oxygen and metal atoms could lead to an increase of the charge transfer between the diamond and oxide, leading to enhanced surface transfer doping., Competing Interests: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Asymmetric supercapacitors (ASCs) are emerging as a new class of energy storage devices that could potentially meet the increasing power and energy demand for next-generation portable and flexible electronics. Yet, the energy density of ASC is severely limited by the low capacitance of the anode side, which commonly uses the carbon-based nanomaterials. Here, the demonstration of sulfur-doped MoO 3- x nanobelts (denoted as S-MoO 3- x ) as the anode for high-performance fiber-shaped ASC are reported. The Mo sites in MoO 3 are intentionally modulated at the atomic level through sulfur doping, where sulfur could be introduced into the MoO 6 octahedron to intrinsically tune the covalency character of bonds around Mo sites and thus boost the charge storage kinetics of S-MoO 3- x . Moreover, the oxygen defects are occurring along with sulfur-doping in MoO 3 , enabling efficient electron transport. As expected, the fiber-shaped S-MoO 3- x achieves outstanding capacitance with good rate capability and long cycling life. More impressively, the fiber-shaped ASC based on S-MoO 3- x anode delivers extremely high volumetric capacitance of 6.19 F cm -3 at 0.5 mA cm -1 , which makes it promising as one of the most attractive candidates of anode materials for high-performance fiber-shaped ASCs., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Lithium-sulfur (Li-S) batteries have been regarded as a promising candidate of secondary batteries to satisfy the enormous demand for electric vehicles and energy storage applications. However, Li-S batteries still suffer from severe capacity fading due to the shuttle effect of lithium polysulfides. Here, we develop a freestanding double-layer MoO 3 /carbon nanotube@S (FMC@S) membrane by hydrothermal and suction filtration strategy, without polymer binder and current collector substrate. FMC@S contains a polysulfide blocking layer and an active material layer. Except for S content, the two layers have the same components and are integrated together, so there is no distinct interface between the two layers, which can facilitate ion and electron transport. As a result, the FMC@S cathode delivers promising capacity retention and rate capability. The hierarchical integrated design provides a new strategy to develop high-performance flexible cathodes for Li-S batteries.

Being a metallic transition-metal dichalcogenide, monolayer vanadium diselenide (VSe 2 ) exhibits many novel properties, such as charge density waves and magnetism. Its interfaces with other materials can potentially be used in device applications as well as for manipulating its intrinsic properties. Here, we present a scanning tunneling microscopy and synchrotron-based X-ray photoemission spectroscopy study of the surface charge-transfer doping using efficient electron-withdrawing and electron-donating materials, that is, molybdenum trioxide (MoO 3 ) and potassium (K), on the molecular beam epitaxy-grown monolayer VSe 2 on highly oriented pyrolytic graphite (HOPG). We demonstrate that monolayer VSe 2 is immune to MoO 3 - and K-doping effects. However, at the monolayer edges where the local chemical reactivity is higher because of Se deficiency, MoO 3 is seen to react with VSe 2 to form molybdenum dioxide (MoO 2 ) and vanadium dioxide (VO 2 ). Compared to the obvious charge-transfer doping effects of MoO 3 and K on HOPG, the electronic structure of monolayer VSe 2 is barely perturbed. This is attributed to the large density of states at the Fermi level of monolayer VSe 2 carrying the metallic character. This work provides new insights into the chemical and electronic properties of monolayer VSe 2 , important for future VSe 2 -based electronic device design.

The development of noncontact humidity sensors with high sensitivity, rapid response, and a facile fabrication process is urgently desired for advanced noncontact human-machine interaction (HMI) applications. Here, a flexible and transparent humidity sensor based on MoO 3 nanosheets is developed with a low-cost and easily manufactured process. The designed humidity sensor exhibits ultrahigh sensitivity, fast response, great stability, and high selectivity, exceeding the state-of-the-art humidity sensors. Furthermore, a wearable moisture analysis system is assembled for real-time monitoring of ambient humidity and human breathing states. Benefiting from the sensitive and rapid response to fingertip humidity, the sensors are successfully applied to both a smart noncontact multistage switch and a novel flexible transparent noncontact screen for smart mobile devices, demonstrating the potential of the MoO 3 nanosheets-based humidity sensors in future HMI systems., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of ultralong (up to tens of micrometers) MoO 3 nanowire-based membranes were synthesized for the treatment of aqueous solutions containing the cationic dyes methylene blue (MB) and rhodamine B (RhB). This treatment method possesses extremely rapid and superhigh adsorbability (up to 521 and 321 mg/g for MB and RhB, respectively), as well excellent selective adsorption ability of cationic dyes with respect to the anionic dye methyl orange (MO). Moreover, the cationic dyes on the membrane can be desorbed easily, and reusability is good., Competing Interests: The authors declare no conflict of interest.

MoO 3 /V 2 O 5 hybrid nanobilayers are successfully prepared by the sol-gel method with a spin- coating technique followed by heat -treatment at 350 °C in order to achieve a good crystallinity. The composition, morphology, and microstructure of the nanobilayers are characterized by a scanning electron microscope (SEM) and X-ray diffractometer (XRD) that revealed the a grain size of around 20-30 nm, and belonging to the monoclinic phase. The samples show good reversibility in the cyclic voltammetry studies and exhibit an excellent response to the visible transmittance. The electrochromic (EC) window displayed an optical transmittance changes (Δ T ) of 22.65% and 31.4% at 550 and 700 nm, respectively, with the rapid response time of about 8.2 s for coloration and 6.3 s for bleaching. The advantages, such as large optical transmittance changes, rapid electrochromism control speed, and excellent cycle durability, demonstrated in the electrochromic cell proves the potential application of MoO 3 /V 2 O 5 hybrid nanobilayers in electrochromic devices.

Exploration of high-performance cathode materials for rechargeable aqueous Zn ion batteries (ZIBs) is highly desirable. The potential of molybdenum trioxide (MoO 3 ) in other electrochemical energy storage devices has been revealed but held understudied in ZIBs. Herein, a demonstration of orthorhombic MoO 3 as an ultrahigh-capacity cathode material in ZIBs is presented. The energy storage mechanism of the MoO 3 nanowires based on Zn 2+ intercalation/deintercalation and its electrochemical instability mechanism are particularly investigated and elucidated. The severe capacity decay of the MoO 3 nanowires during charging/discharging cycles arises from the dissolution and the structural collapse of MoO 3 in aqueous electrolyte. To this end, an effective strategy to stabilize MoO 3 nanowires by using a quasi-solid-state poly(vinyl alcohol)(PVA)/ZnCl 2 gel electrolyte to replace the aqueous electrolyte is developed. The capacity retention of the assembled ZIBs after 400 charge/discharge cycles at 6.0 A g -1 is significantly boosted, from 27.1% (in aqueous electrolyte) to 70.4% (in gel electrolyte). More remarkably, the stabilized quasi-solid-state ZIBs achieve an attracting areal capacity of 2.65 mAh cm -2 and a gravimetric capacity of 241.3 mAh g -1 at 0.4 A g -1 , outperforming most of recently reported ZIBs., Competing Interests: The authors declare no conflict of interest.

Molybdenum oxide (MoO₃) and Fe,Co-codoped MoO₃ thin films obtained by spray pyrolysis have been in-depth investigated to understand the effect of Co and Fe codoping on MoO₃ thin films. The effect of Fe and Co on the structural, morphological and optical properties of MoO₃ thin films have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray analysis (EDAX), optical and photoluminescence (PL) spectroscopy, and electropyroelectric methods. The XRD patterns demonstrated the formation of orthorhombic α-MoO₃ by spray pyrolysis. SEM characterization has shown an increase in roughness of MoO₃ thin films by Fe and Co doping. Optical reflectance and transmittance measurements have shown an increase in optical band gap with the increase in Fe and Co contents. Thermal conductivity and thermal diffusivity of Fe,Co-doped MoO₃ were 24.10⁻25.86 Wm -1 K -1 and 3.80 × 10 -6 ⁻5.15 × 10 -6 m²s -1 , respectively. MoO₃ thin films have shown PL emission. Doping MoO₃ with Fe and Co increases emission in the visible range due to an increase number of chemisorbed oxygen atoms. The photodegradation of an aqueous solution of methylene blue (MB) depended on the content of the codoping elements (Fe,Co). The results showed that a degradation efficiency of 90% was observed after 60 min for MoO₃: Fe 2%-Co 1%, while the degradation efficiency was about 35% for the undoped MoO₃ thin film.

In this study, the tribological behavior of lamellar MoO₃ as a lubricant additive was investigated under different concentrations, particle sizes, normal loads, velocity, and temperature. The friction and wear tests were performed using a tribometer and with a reciprocating motion. The results indicate that the friction-reducing ability and antiwear property of the base oil can be improved effectively with the addition of lamellar MoO₃. The 0.5 wt % and 0.1 wt % concentrations of MoO₃ yield the best antifriction and antiwear effects, respectively. The maximum friction and wear reduction is 19.8% and 55.9%, compared with that of the base oil. It is also found the MoO₃ additive can decrease the friction considerably under a high velocity and normal load, and increase the working temperature. The smaller the size of MoO₃, the better the friction-reducing effect the lamellar MoO₃ shows. The friction-reducing and antiwear mechanisms of lamellar MoO₃ were discussed.