Molybdenum metal and commonly encountered molybdenum compounds

Molybdenum is widely distributed in nature. It is found in the minerals molybdenite,MoS2 which is the major ore of molybdenum, wulfenite, ferrimolybdate, jordisite, and powellite. Most molybdenum compounds are derived from molybdenum trioxide which is prepared by roasting molybdenum disulfide ores in air. Commonly used molybdenum-oxygen compounds are molybdenum trioxide, MoO3, sodium molybdate, Na2MoO4.2H2O, ammonium dimolybdate, (NH4)2 Mo2O7, and ammonium heptamolybdate, (NH4)6Mo7O24.4H2O.

Molybdenum is used mainly as an alloying element in steel, cast iron, and superalloys and in the electronics industries.

Leichtfried, G., in Ullmann's Encyclopedia of Industrial Chemistry ,5th ed. 1990, A16 , 668.

Molybdenum trioxide and molybdenum-oxygen compounds are added to steel and corrosion-resistant alloys. They are used in industrial catalysts, corrosion inhibitors, pigments, glass, ceramics, and enamels, flame retardant for polyester and polyvinyl chloride resins, as crop nutrients in agriculture, and as reagents in chemical analyses.

Vukasovich, M. S., in Ullmann's Encyclopedia of Industrial Chemistry ,5th ed., 1990, A16 , 682.

Molybdenum-sulfur compounds are used in lubrication to reduce friction and wear: molybdenum disulfide as a dry or suspended lubricant and molybdenum-sulfur complexes as soluble oil additives.

Mitchell, P. C. H., Wear , 1984, 100 , 281.

Other molybdenum compounds which find some application, for example, in the electronics industries and in chemical vapour deposition, are molybdenum pentachloride and molybdenum hexacarbonyl.

Environmental release of molybdenum compounds from industrial activities can occur in air (stack emissions), water (liquid effluents), or solid wastes (sludge): see Industrial and Environmental Exposure of Humans to Molybdenum.


Separation and purification of Tc-99m from Mo-99 produced by electron linear accelerator

The medical radionuclide Mo-99 was produced by the Mo-100(gamma,n) reaction using bremsstrahlung photons generated by an electron linear accelerator. The amount of Mo-99 produced was compared to that predicted by calculation using the particles and heavy ion transport code system. From the Mo-99 produced, highly pure Tc-99m was separated using the so-called technetium master milker, and the chemical yield of Tc-99m was 83-99 %. The installation of a new complex using this method and the electron linear accelerator with the preferable specification was suggested, and a possibility to supply the demand of Tc-99m was discussed and shown.

Sekimoto, S., Tatenuma, K., Suzuki, Y., Tsuguchi, A., Tanaka, A., Tadokoro, T., Kani, Y., Morikawa, Y., Yamamoto, A., and Ohtsuki, T.,Separation and purification of Tc-99m from Mo-99 produced by electron linear accelerator, Journal of Radioanalytical and Nuclear Chemistry, 2017, 311, 1361-1366.



Mo-99 Tc-99m

Evaluation of the radionuclidic product profiles of natural molybdenum irradiated using linear accelerator and nuclear reactor technology

The objective of this study was to compare the radionuclidic product profiles of the primary source Mo-99-sodium molybdate ((MoO4)-Mo-992-) solution obtained after dissolution of nuclear reactor-irradiated sintered molybdenum discs with the profiles obtained for linear accelerator-irradiated discs. Radionuclidic analysis was performed by high-purity germanium gamma-ray spectrometry. Samples were analyzed at multiple time points and radioactivity levels in order to observe short lived and low activity radionuclidic long-lived impurities. Results obtained showed that the radionuclidic profiles from the two technologies are consistent between samples, and are unique for either production technology.

Grigoryan, M., Fitzpatrick, J., and Mangera, K.,Evaluation of the radionuclidic product profiles of natural molybdenum irradiated using linear accelerator and nuclear reactor technology, Journal of Radioanalytical and Nuclear Chemistry, 2016, 310, 1195-1199.


Cellular responses of osteoblast-like cells to 17 elemental metals

Elemental metals have been widely used to alloy metallic orthopedic implants. However, there is still insufficient research data elucidating the cell responses of osteoblastic cells to alloying elemental metals, which impedes the development of new metallic implant materials. In this study, the cellular responses of osteoblast-like cells (SaOS2) to 17 pure alloying elemental metals, that is, titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), manganese (Mn), iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), silicon (Si), and tin (Sn) were comparatively investigated in vitro. Cellular responses including intracellular total protein synthesis and collagen content, cell adhesion, cell proliferation, and alkaline phosphatase (ALP) activity on these elemental metals were systematically assessed and compared. It was found that these elemental metals could be categorized into three groups based on the cellular functions on them. Group 1, including Ti, Zr, Hf, Nb, Ta, Cr, Ru, and Si, showed excellent cell proliferation and varied ALP activity for SaOS2 cells. Cells exposed to Group 2, including Mo and Sn, although initially attached and grew, did not proliferate over time. In contrast, Group 3, including V, Mn, Fe, Co, Ni, Cu, and Zn, showed severe cytotoxicity toward SaOS2 cells. It is vital to consider the cell responses to the elemental metals when designing a new metallic implant material and the findings of this study provide insights into the biological performance of the elemental metals. (c) 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2016.

Zhang, D., Wong, C. S., Wen, C., and Li, Y.,Cellular responses of osteoblast-like cells to 17 elemental metals, Journal of biomedical materials research. Part A, 2016.


Quantitative in vivo biocompatibility of new ultralow-nickel cobalt-chromium-molybdenum alloys

Nickel (Ni) eluted from metallic biomaterials is widely accepted as a major cause of allergies and inflammation. To improve the safety of cobalt-chromium-molybdenum (Co-Cr-Mo) alloy implants, new ultralow-Ni Co-Cr-Mo alloys with and without zirconium (Zr) have been developed, with Ni contents of less than 0.01%. In the present study, we investigated the biocompatibility of these new alloys in vivo by subcutaneously implanting pure Ni, conventional Co-Cr-Mo, ultralow-Ni Co-Cr-Mo, and ultralow-Ni Co-Cr-Mo with Zr wires into the dorsal sides of mice. After 3 and 7 days, tissues around the wire were excised, and inflammation; the expression of IL-1beta, IL-6, and TNF-alpha; and Ni, Co, Cr, and Mo ion release were analyzed using histological analyses, qRT-PCR, and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Significantly larger amounts of Ni eluted from pure Ni wires than from the other wires, and the degree of inflammation depended on the amount of eluted Ni. Although no significant differences in inflammatory reactions were identified among new alloys and conventional Co-Cr-Mo alloys in histological and qRT-PCR analyses, ICP-MS analysis revealed that Ni ion elution from ultralow-Ni Co-Cr-Mo alloys with and without Zr was significantly lower than from conventional Co-Cr-Mo alloys. Our study, suggests that the present ultralow-Ni Co-Cr-Mo alloys with and without Zr have greater safety and utility than conventional Co-Cr-Mo alloys. (c) 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1505-1513, 2016.

Sonofuchi, K., Hagiwara, Y., Koizumi, Y., Chiba, A., Kawano, M., Nakayama, M., Ogasawara, K., Yabe, Y., and Itoi, E.,Quantitative in vivo biocompatibility of new ultralow-nickel cobalt-chromium-molybdenum alloys, Journal of orthopaedic research : official publication of the Orthopaedic Research Society, 2016, 34, 1505-13.


The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, that are manufactured, imported or used in different products (substances or articles) are identified and proven safe for humans and the environment. Metals and alloys need hence to be investigated on their extent of released metals (bioaccessibility) in biologically relevant environments. Read-across from available studies may be used for similar materials. This study investigates the release of molybdenum and iron from powder particles of molybdenum metal (Mo), a ferromolybdenum alloy (FeMo), an iron metal powder (Fe), MoO2, and MoO3 in different synthetic body fluids of pH ranging from 1.5 to 7.4 and of different composition. Spectroscopic tools and cyclic voltammetry have been employed to characterize surface oxides, microscopy, light scattering and nitrogen absorption for particle characterization, and atomic absorption spectroscopy to quantify released amounts of metals. The release of molybdenum from the Mo powder generally increased with pH and was influenced by the fluid composition. The mixed iron and molybdenum surface oxide of the FeMo powder acted as a barrier both at acidic and weakly alkaline conditions. These findings underline the importance of the surface oxide characteristics for the bioaccessibility of metal alloys.

Morsdorf, A.,Wallinder, I. O.,and Hedberg, Y.,Bioaccessibility of micron-sized powder particles of molybdenum metal, iron metal, molybdenum oxides and ferromolybdenum - Importance of surface oxides, Regul Toxicol Pharmacol, 2015.

A perspective on molybdenum biocompatibility and antimicrobial activity for applications in implants

The use of biomaterials has become routine in dentistry, reconstructive surgery of the locomotor system, treatment of congenital, traumatic and tumor situations, and knee or hip arthroplasty. The main issue related to metal biomaterials is the systemic release of metal ions and the related biological risks. When placed in contact with a living organism, they must meet a set of criteria: they must be biocompatible and biofunctional, as well as have the ability to produce a specific biological response at the surface, leading to the formation of a bond between the material and the receiving tissue and a surface texture which allows cell adhesion and bone growth; they must also provide adequate structure and mechanical strength, without causing adverse reactions in the surrounding physiological environment; they must not cause oncogenic effects; they must be easy to manipulate during surgery; and they must be amenable to visible imaging and sterilization.

The ability to use biomaterials is linked to the degree of biocompatibility and biofunctionality which in turn, are dependent on their physicochemical and mechanical properties, macroscopic and microscopic configuration, and the biological environment where they are deployed.

Metal alloys, particularly stainless steel, cobalt, molybdenum, chromium alloys, and titanium-based alloys find wide application in orthopedics for making joint replacement prostheses, systems for external or internal fixation of bone fractures, surgical correction of degenerative conditions, or in the composition of staples, screws, and wires. Any synthetic biomaterial can replace or restore the function of body tissues while maintaining a continuous or intermittent contact with the fluid. When in contact with the fluid, it is essential that materials be biocompatible, so they do not produce adverse biological responses or induce systemic effects. Thus, they must not be toxic, carcinogenic, mutagenic, or antigenic. Bioactive materials with antibacterial properties are also of significant medical interest. Materials exhibiting good antimicrobial activity that minimize the formation of biofilm without the risk of promoting the development of resistant microorganisms are desirable. In this respect, this review briefly summarizes the recent successes of this metal as a biocompatible material with antibacterial activity for biomedical applications.

Ribeiro, A. M., Flores-Sahagun, T. H. S., and Paredes, R. C.,A perspective on molybdenum biocompatibility and antimicrobial activity for applications in implants, Journal of Materials Science, 2016, 51, 2806-2816.

Thermodynamic properties

Thermodynamic properties for calcium molybdate, molybdenum tri-oxide and aqueous molybdate ion

The thermodynamic properties for CaMoO4(cr), MoO3(cr) and MoO42- (aq) were investigated. CaMoO4(cr) is the one of the host crystals of the yellow phases which are known as hygroscopic harmful phases in the nuclear fuel glasses. MoO3(cr) is the main component of the host crystals. MoO42- (aq) is the aqueous ion present in underground water after dissolution of the yellow phases. The standard molar entropies, Delta S-T(0)m degrees, at 298.15 K for CaMoO4(cr) and MoO3(cr) were determined by measuring their isobaric heat capacities, C degrees(p,m), from 2 K. Their standard Gibbs energies of formation, Delta(f)G(m)degrees, were determined by combining the Delta(T)(0) S-m degrees data with the reference data of the standard enthalpies of formation, Delta H-f(m)degrees. The standard electrochemical potential, E degrees, of MoO42- (aq) was determined from the thermodynamic cycle on the basis of thermodynamic properties obtained for CaMoO4(cr) and MoO3(cr). The unknown standard Gibbs energies of solution, Delta(sln)G(m)degrees, at 298.15 K for the actinide molybdates ThMo2O8(cr) and UMoO6(cr) were predicted from the presently obtained thermodynamic data for CaMoO4(cr), MoO3(cr) and MoO42 (aq). The obtained thermodynamic values are as follows: Delta(T)(0) S-m degrees (CaMoO4(cr), 298.15 K)/(J K (1) mol (1)) = 122.23 +/- 1.22. Delta(T)(0) S-m degrees(MoO3(cr), 298.15 K)/(J K (1) mol (1)) = 75.43 +/- 0.75. Delta(T)(0) S-m degrees (MoO42 (aq), 298.15 K)/(J K (1) mol (1)) = 32.25 +/- 4.41. Delta(f)G(m)degrees (CaMoO4(cr), 298.15 K)/(kJ mol (1)) = -1437.78 +/- 1.11. Delta(f)G(m)degrees (MoO3(cr), 298.15 K)/(kJ mol (1)) = -667.20 +/- 0.63. Delta(f)G(m)degrees(MoO42 (aq), 298.15 K)/(kJ mol (1)) = -836.61 +/- 1.02. E degrees (MoO42 (aq), 298.15 K)/V = 4.34 +/- 0.01. Delta(sln)G(m)degrees (ThMo2O8(cr), 298.15 K)/(kJ mol (1)) = 184.84 +/- 42.48. Delta(sln)G(m)degrees (UMoO6(cr), 298.15 K)/(kJ mol (1)) = 68.33 +/- 34.47. The present obtained data are expected to be useful for geo-chemical simulation of diffusion of radioactive elements through underground water. (C) 2017 Elsevier Ltd.

Morishita, M., Kinoshita, Y., Houshiyama, H., Nozaki, A., and Yamamoto, H.,Thermodynamic properties for calcium molybdate, molybdenum tri-oxide and aqueous molybdate ion, Journal of Chemical Thermodynamics, 2017, 114, 30-43.


High efficient and selective removal of Pb2+ through formation of lead molybdate on alpha-MoO3 porous nanosheets array

2D hand-like structured alpha-MoO3 porous nanosheets were grown in-situ onto a capillary by a simple hydrothermal route, on which titanium dioxide seed layer was sol-dip-coated in advance. The alpha-MoO3 porous nanosheets array exhibits an exceptional lead ion uptake capacity up to 1450.0mg.g-1, and can effectively reduce Pb2+ concentration from 20mg.L-1 to a low level of smaller than 3mug.L-1, well below the acceptable limits in drinking water standards (10mug.L-1) and can efficiently remove 99.9% lead ion within a few minutes at room temperature. Furthermore, alpha-MoO3 porous nanosheets array also has high selectivity toward Pb2+ better than Cu2+, Zn2+, Cr3+ and Cd2+. The mechanism for adsorption was discussed according to the results of Zeta potential, IR, XPS and XRD analyses. The excellent removal performance of the array to Pb2+ is resulted from the electrostatic adsorption interaction and the formation of new species lead molybdate.

Wu, Y., Cheng, X., Zhang, X., Xu, Y., Gao, S., Zhao, H., and Huo, L.,High efficient and selective removal of Pb2+ through formation of lead molybdate on alpha-MoO3 porous nanosheets array, J Colloid Interface Sci, 2017, 491, 80-88.


Aqueous synthesis of molybdenum trioxide (h-MoO3, alpha-MoO3 H2O and h-/alpha-MoO3 composites) and their photochromic properties study

Molybdenum trioxide (h-MoO3, alpha-MoO3 H2O and h-/alpha-MoO3 composites) were prepared by a simple method in aqueous solution at 90-95 degrees C, without using autoclave or other complex equipment. The synthetic conditions for different phases of MoO3 were studied. The ratio of MoO42-:H+ and reaction temperature play important roles for the crystal phases of MoO3. By changing the amount of H+ ions, the samples can be controlled as h-MoO3 microrods or alpha-MoO3 H2O microbelts. h-/alpha-MoO3 composites in homogeneous structure were obtained at higher temperatures. The study on the transformation process of h-MoO3 ->alpha-MoO3 H2O ->alpha-MoO3 would be helpful in designing functional MoO3 materials. The h-MoO3 microrods and h-/alpha-MoO3 composites showed good photochromic behavior under sunlight irradiation. (C) 2016 Elsevier B.V. All rights reserved.

Song, Y. H., Zhao, Y., Huang, Z. F., and Zhao, J. Z.,Aqueous synthesis of molybdenum trioxide (h-MoO3, alpha-MoO3·H2O and h-/alpha-MoO3 composites) and their photochromic properties study, Journal of Alloys and Compounds, 2017, 693, 1290-1296.

Hydrogen reduction of molybdenum oxide at room temperature

The color changes in chemo- and photochromic MoO3 used in sensors and in organic photovoltaic (OPV) cells can be traced back to intercalated hydrogen atoms stemming either from gaseous hydrogen dissociated at catalytic surfaces or from photocatalytically split water. In applications, the reversibility of the process is of utmost importance, and deterioration of the layer functionality due to side reactions is a critical challenge. Using the membrane approach for high-pressure XPS, we are able to follow the hydrogen reduction of MoO3 thin films using atomic hydrogen in a water free environment. Hydrogen intercalates into MoO3 forming HxMoO3, which slowly decomposes into MoO2 +1/2 H2O as evidenced by the fast reduction of Mo6+ into Mo5+ states and slow but simultaneous formation of Mo4+ states. We measure the decrease in oxygen/metal ratio in the thin film explaining the limited reversibility of hydrogen sensors based on transition metal oxides. The results also enlighten the recent debate on the mechanism of the high temperature hydrogen reduction of bulk molybdenum oxide. The specific mechanism is a result of the balance between the reduction by hydrogen and water formation, desorption of water as well as nucleation and growth of new phases.

Borgschulte, A., Sambalova, O., Delmelle, R., Jenatsch, S., Hany, R., and Nuesch, F.,Hydrogen reduction of molybdenum oxide at room temperature, Sci Rep, 2017, 7, 40761.


Highly selective and sensitive response of 30.5 % of sprayed molybdenum trioxide (MoO3) nanobelts for nitrogen dioxide (NO2) gas detection

The molybdenum trioxide (MoO3) thin films have been successfully deposited onto the glass substrates using chemical spray pyrolysis (CSP) deposition technique at various substrate temperatures ranging from 300 degrees C to 450 degrees C with an interval of 50 degrees C. The effect of substrate temperature on the structural, morphological, optical and gas sensing properties of MoO3 thin films has been thoroughly investigated. X-ray diffraction analysis reveals that all the films have an orthorhombic crystal structure and are polycrystalline in nature. FE-SEM micrographs depict the formation of nanobelts-like morphology. AFM study reveals that the RMS surface roughness of MoO3 thin films increases from 8.6nm to 12nm with increase in substrate temperature from 300 degrees C to 400 degrees C and then decreases to 11.5nm for substrate temperature of 450 degrees C. Optical results show that the band gap of MoO3 thin films decreases from 3.92eV to 3.44eV. The selectivity studies show that the gas response of various gases varies as NH3222S2. Moreover, typical MoO3 film deposited at substrate temperature of 400 degrees C is highly selective and sensitive for detection of NO2 gas in comparison with other gases. The maximum response of 30.5 % is obtained towards 100ppm NO2 gas concentration at an operating temperature of 200 degrees C with response and recovery times of 20s and 160s, respectively. Finally, NO2 gas sensing mechanism model based on the chemisorption process is discussed.

Mane, A. A., Suryawanshi, M. P., Kim, J. H., and Moholkar, A. V.,Highly selective and sensitive response of 30.5 % of sprayed molybdenum trioxide (MoO3) nanobelts for nitrogen dioxide (NO2) gas detection, Journal of colloid and interface science, 2016, 483, 220-31.

Molybdenum Oxide Nanoparticles as Antimicrobial Agents

Molybdenum oxide nanoparticles were prepared by electrochemical reduction method using tetra ethyl ammonium bromide as structure directing agent in an organic medium tetrahydrofuran/acetonitrile in 4:1 ratio and at current density 14 mA/cm(2). The synthesized molybdenum oxide nanoparticles were characterized by using ultra violet-visible spectroscopy, infra red spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscope analysis techniques. The nanoparticles were tested for antibacterial activity against human pathogens like gram negative Escherichia coli, Salmonella typhi and gram positive Staphylococcus aureus, Bacillus subtilis strains, which showed excellent antibacterial properties.

Dighore, N., Jadhav, S., Anandgaonker, P., Gaikwad, S., and Rajbhoj, A.,Molybdenum Oxide Nanoparticles as Antimicrobial Agents, Journal of Cluster Science, 2017, 28, 109-118.


Cellulose acetate based composites with antimicrobial properties from embedded molybdenum trioxide particles

The objective of this research is to develop novel cellulose acetate (biopolymer) composite materials with an excellent antimicrobial activity by embedding molybdenum trioxide particles with unique high specific surface area.

High surface area molybdenum trioxide particles were prepared from freshly precipitated molybdenum trioxide dihydrate (MoO3 x2H2 O) and subsequent calcination at 340 degrees C under H2 /N2 gas.

Microbiological evaluation against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were performed applying a roll-on test and excellent antimicrobial activities were determined for composites with embedded anhydrous molybdenum trioxide with a high specific surface area.

Cellulose acetate composites comprising MoO3 particles can eliminate three harmful bacteria as a result of the release of protons from the material and surface enlargement of the molybdenum trioxide particles.

The findings support a proposed antimicrobial mechanism based on local acidity increase due to large specific surface areas. This article is protected by copyright. All rights reserved.

Shafaei, S., Dorrstein, J., Guggenbichler, J. P., and Zollfrank, C.,Cellulose acetate based composites with antimicrobial properties from embedded molybdenum trioxide particles, Letters in applied microbiology, 2016.



The crystallographic structure and morphology of redox active transition metal oxides have a pronounced effect on their electrochemical properties. In this work, h-MoO3 nanostructures with three distinct morphologies, i.e., pyramidal nanorod, prismatic nanorod and hexagonal nanoplate, were synthesized by a facile solvothermal method. The morphologies of h-MoO3 nanostructures were tailored by a controlled amount of hexamethylenetetramine. An enhanced specific capacitance about 230 F g(-1) at an applied current density of 0.25 A g(-1) was achieved in h-MoO3 pyramidal nanorods. Electrochemical studies confirmed that the h-MoO3 pyramidal nanorods exhibit superior charge-storage ability. This improved performance can be ascribed to the coexistence of its well exposed crystallographic planes with abundant active sites, i.e., hexagonal window (HW), trigonal cavity (TC) and four-coordinated square window (SW). The mechanism of charge-storage is likely facilitated by the vehicle mechanism of proton transportation due to the availability of the vehicles, i.e., NH4(+) and H2O. The promising, distinct and unexploited features of h-MoO3 nanostructures reveal a strong candidate for pseudocapacitive electrode materials.

Kumar, V., Wang, X., and Lee, P. S.,Formation of hexagonal-molybdenum trioxide (h-MoO3) nanostructures and their pseudocapacitive behavior, Nanoscale, 2015, 7, 11777.


Influence of calcination temperature on the structural and photochromic properties of nanocrystalline MoO3

Nanocrystalline metastable hexagonal and thermodynamically stable orthorhombic MoO3were successfully synthesized by precipitation, and calcined at various temperatures in the range 200-500 degrees C.

The influence of calcination temperature on crystal structure, crystallite size, thermal properties, morphology, optical properties, and photochromic properties was determined.

The 432 degrees C phase transformation temperature of hexagonal flower-like MoO3to an orthorhombic platelet structure was determined.

The band gap energy of MoO3 varied from 3.13 to 3.20 eV, depending on calcination temperature.

The photochromic properties were determined with UV irradiation and CIE Lab colour system. The hexagonal MoO3 from low temperature calcination had an about seven-fold photochromic efficiency relative to orthorhombic MoO3.

Jittiarporn, P., Sikong, L., Kooptarnond, K., and Taweepreda, W.,INFLUENCE OF CALCINATION TEMPERATURE ON THE STRUCTURAL AND PHOTOCHROMIC PROPERTIES OF NANOCRYSTALLINE MoO3, Digest Journal of Nanomaterials and Biostructures, 2015, 10, 1237-1248.


Band energy control of molybdenum oxide by surface hydration

The application of oxide buffer layers for improved carrier extraction is ubiquitous in organic electronics. However, the performance is highly susceptible to processing conditions. Notably, the interface stability and electronic structure is extremely sensitive to the uptake of ambient water.

In this study we use density functional theory calculations to asses the effects of adsorbed water on the electronic structure of MoOx, in the context of polymer-fullerene solar cells based on PCDTBT. We obtain excellent agreement with experimental values of the ionization potential for pristine MoO3 (010). We find that IP and EA values can vary by as much as 2.5 eV depending on the oxidation state of the surface and that adsorbed water can either increase or decrease the IP and EA depending on the concentration of surface water. (C) 2015 AIP Publishing LLC.

Butler, K. T., Crespo-Otero, R., Buckeridge, J., Scanlon, D. O., Bovill, E., Lidzey, D., and Walsh, A.,Band energy control of molybdenum oxide by surface hydration, Applied Physics Letters, 2015, 107.

Oxygen deficiency in MoO3 polycrystalline nanowires and nanotubes

We report on the synthesis of polycrystalline molybdenum oxide (MoO3) nanowires via oxidation of molybdenum-sulfur-iodine (Mo6S2I8) nanowires. This unique synthesis route results in an interesting morphology comprising porous nanowires and nanotubes.

We found the nanowires to have the orthorhombic MoO3 structure. The structure is slightly oxygen deficient which results in the appearance of a new resonant Raman band (1004 cm-1) and paramagnetic defects (Mo5+) of both the point and crystallographic shear plane nature. (C) 2015 Elsevier B.V. All rights reserved.

Varlec, A., Arcon, D., Skapin, S. D., and Remskar, M.,Oxygen deficiency in MoO3 polycrystalline nanowires and nanotubes, Materials Chemistry and Physics, 2016, 170, 154-161.

Probing edge-activated resonant Raman scattering from mechanically exfoliated 2D MoO3 nanolayers

We report spatially resolved vibrational analysis of mechanically exfoliated single-crystalline alpha-MoO3 nanolayers.

Raman scattering from alpha-MoO3 was enhanced predominantly at the outside edges of the nanolayers. The enhanced Raman scattering at the edges was attributed primarily to the enhanced resonant Raman effect caused by a high density of oxygen vacancies localized at the edges.

The localized vacancy sites corresponded to a non-stoichiometric phase of MoO3, which would provide reactive sites with high catalytic activity.

Yano, T. A., Yoshida, K., Hayamizu, Y., Hayashi, T., Ohuchi, F., and Hara, M.,Probing edge-activated resonant Raman scattering from mechanically exfoliated 2D MoO3 nanolayers, 2d Materials, 2015, 2.

Nanoscale Insights into the Hydrogenation Process of Layered alpha-MoO3

The hydrogenation process of the layered alpha-MoO3 crystal was investigated on a nanoscale.

At low hydrogen concentration, the hydrogenation can lead to formation of HxMoO3 without breaking the MoO3 atomic flat surface. For hydrogenation with high hydrogen concentration, hydrogen atoms accumulated along the < 101 > direction on the MoO3, which induced the formation of oxygen vacancy line defects. The injected hydrogen atoms acted as electron donors to increase electrical conductivity of the MoO3.

Near-field optical measurements indicated that both of the HxMoO3 and oxygen vacancies were responsible for the coloration of the hydrogenated MoO3, with the latter contributing dominantly.

On the other hand, diffusion of hydrogen atoms from the surface into the body of the MoO3 will encounter a surface diffusion energy barrier, which was for the first time measured to be around 80 meV. The energy barrier also sets an upper limit for the amount of hydrogen atoms that can be bound locally inside the MoO3 via hydrogenation.

We believe that our findings has provided a clear picture of the hydrogenation mechanisms in layered transition-metal oxides, which will be helpful for control of their optoelectronic properties via hydrogenation.

Xie, W. G., Su, M. Z., Zheng, Z. B., Wang, Y., Gong, L., Xie, F. Y., Zhang, W. H., Luo, Z., Luo, J. Y., Liu, P. Y., Xu, N. S., Deng, S. Z., Chen, H. J., and Chen, J.,Nanoscale Insights into the Hydrogenation Process of Layered alpha-MoO3, Acs Nano, 2016, 10, 1662-1670.

A theoretical study of stability and vacancy replenishing of MoO3(010) surfaces in oxygen atmosphere

Oxygen vacancies on transition metal oxide surfaces are catalytically very important. The stability, shape and replenishing process of the vacancies are critical to understanding reactions happening on the surfaces.

In this paper we investigate the stability of various defective MoO3 (0 1 0) surfaces and examine the influence of environmental oxygen on the stability as well as the active sites for the replenishing process.

Our calculations reveal that the line oxygen defect along a (asymmetric oxygen) direction is thermodynamically most favorable at higher defect concentration whereas point defect surfaces are unfavorable. Under normal experimental conditions the perfect surface dominates the MoO3 (0 1 0).

We show that for stoichiometric surfaces of any oxides (A(x)O(y)) the formation energy per vacancy controls the favorable defect shape (line or point defects). Calculations indicate that O-2 can dissociate readily on the surfaces that double vacancies share one Mo atom. The replenishing process of the oxygen vacancies through O-2 dissociation most likely occurs on the double-vacancy containing one terminal and one asymmetrical oxygen vacancies. (C) 2015 Elsevier B.V. All rights reserved.

Lei, Y. H., and Chen, Z. X.,A theoretical study of stability and vacancy replenishing of MoO3(010) surfaces in oxygen atmosphere, Applied Surface Science, 2016, 361, 107-113.

Facile synthesis of a green metastable MoO3 for the selective oxidation of methanol to formaldehyde

Metastable MoO3 was successfully synthesized by a chemical transformation of alpha-MoO3 and characterized by TG-DSC, BET, XRD and Raman spectroscopy. The prepared material was highly active and selective to formaldehyde formation from methanol over a wide range of reaction temperatures. The formaldehyde selectivity can reach up to 99 % at about 98 % methanol conversion. The stability of the prepared catalysts was also investigated.

Phuong, P. T. T., Duy, N. P. H., Tai, V. T., Huan, N. M., Phuc, N. H. H., and Loc, L. C.,Facile synthesis of a green metastable MoO3 for the selective oxidation of methanol to formaldehyde, Reaction Kinetics Mechanisms and Catalysis, 2016, 117, 161-171.

Isoprenoid Alcohols are Susceptible to Oxidation with Singlet Oxygen and Hydroxyl Radicals

Isoprenoids, as common constituents of all living cells, are exposed to oxidative agents-reactive oxygen species, for example, singlet oxygen or hydroxyl radicals. Despite this fact, products of oxidation of polyisoprenoids have never been characterized.

In this study, chemical oxidation of isoprenoid alcohols (Prenol-2 and -10) was performed using singlet oxygen (generated in the presence of hydrogen peroxide/molybdate or upon photochemical reaction in the presence of porphyrin), oxygen (formed upon hydrogen peroxide dismutation) or hydroxyl radical (generated by the hydrogen peroxide/sonication, UV/titanium dioxide or UV/hydrogen peroxide) systems.

The structure of the obtained products, hydroxy-, peroxy- and heterocyclic derivatives, was studied with the aid of mass spectrometry (MS) and nuclear magnetic resonance (NMR) methods. Furthermore, mass spectrometry with electrospray ionization appeared to be a useful analytical tool to detect the products of oxidation of isoprenoids (ESI-MS analysis), as well as to establish their structure on the basis of the fragmentation spectra of selected ions (ESI-MS/MS analysis). Taken together, susceptibility of polyisoprenoid alcohols to various oxidizing agents was shown for the first time.

Komaszylo Nee Siedlecka, J., Kania, M., Masnyk, M., Cmoch, P., Lozinska, I., Czarnocki, Z., Skorupinska-Tudek, K., Danikiewicz, W., and Swiezewska, E.,Isoprenoid Alcohols are Susceptible to Oxidation with Singlet Oxygen and Hydroxyl Radicals, Lipids, 2016, 51, 229-44.

Degradable Molybdenum Oxide Nanosheets with Rapid Clearance and Efficient Tumor Homing Capabilities as a Therapeutic Nanoplatform

Molybdenum oxide (MoOx) nanosheets with high near-infrared (NIR) absorbance and pH-dependent oxidative degradation properties were synthesized, functionalized with polyethylene glycol (PEG), and then used as a degradable photothermal agent and drug carrier.

The nanosheets, which are relatively stable under acidic pH, could be degraded at physiological pH. Therefore, MoOx-PEG distributed in organs upon intravenous injection would be rapidly degraded and excreted without apparent in vivo toxicity. MoOx-PEG shows efficient accumulation in tumors, the acidic pH of which then leads to longer tumor retention of those nanosheets.

Along with the capability of acting as a photothermal agent for effective tumor ablation, MoOx-PEG can load therapeutic molecules with high efficiencies.

This concept of inorganic theranostic nanoagent should be relatively stable in tumors to allow imaging and treatment, while being readily degradable in normal organs to enable rapid excretion and avoid long-term retention/toxicity.

Song, G., Hao, J., Liang, C., Liu, T., Gao, M., Cheng, L., Hu, J., and Liu, Z.,Degradable Molybdenum Oxide Nanosheets with Rapid Clearance and Efficient Tumor Homing Capabilities as a Therapeutic Nanoplatform, Angewandte Chemie (International ed. in English), 2016, 55, 2122-6.



beta-Ag2MoO4 microcrystals: Characterization, antibacterial properties and modulation analysis of antibiotic activity

This study reports the antibacterial properties and modulation analysis of antibiotic activity by beta-Ag2MoO4 microcrystals as well as their structural and vibrational characterization.

The silver molybdate was obtained by the conventional hydrothermal method, and the structural, vibrational and morphological properties of the sample were determined using X-ray diffraction, Raman spectroscopy and scanning electron microscopy images. beta-Ag2MoO4 microcrystals obtained show spinel-type cubic structure (Fd-3m) with irregular shapes.

The evaluation of antibacterial and modulatory-antibiotic activity was performed using the microdilution method to determine the Minimum Inhibitory Concentration (MIC) of the beta-Ag2MoO4 and antibiotics alone and associated with the silver molybdate.

The beta-Ag2MoO4 modulates the antibiotic activity against all bacteria assayed in a synergistic (as the norfloxacin and gentamicin against S. aureus and gentamicin against E. coli) or an antagonistic form (as the norfloxacin against E.coli and P. aeruginosa).

The reversion of antibiotic resistance by combinations with Ag2MoO4 could be a novel strategy to combat infections caused by multiple drug resistance (MDR) pathogens.

Our results indicate that these silver molybdates present a clinically relevant antibacterial activity and enhanced the antibiotic activity of some antibiotics against MDR strain of S. aureus and E. coli, being an interesting alternative to combat antibiotic-resistant bacterial infectious agents.

Moura, J. V., Freitas, T. S., Cruz, R. P., Pereira, R. L., Silva, A. R., Santos, A. T., da Silva, J. H., Luz-Lima, C., Freire, P. T., and Coutinho, H. D.,beta-Ag2MoO4 microcrystals: Characterization, antibacterial properties and modulation analysis of antibiotic activity, Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie, 2017, 86, 242-247.

Novel application of simple molybdates: Catalytic hydrolysis of an organophosphate neurotoxin under mild aqueous conditions

A novel protocol for hydrolyzing phosphonothioate neurotoxins has been developed that uses a readily available, inexpensive and non-toxic molybdate (MoO42-). The target organophosphate is O,S-diethylphenyl phosphonothioate (1), a model compound that has served as an analog of the chemical warfare agent VX. Molybdate-mediated hydrolysis of 1 proceeds at room temperature (pH similar to 7.5) and yields a relatively safe phosphonate product through P-S specific scission. This is the first report of utilizing the molybdateMoO42- , to degrade an organophosphate neurotoxin with turnover. A ΔS  of 81.5 J/mol.K (-19.5 cal/mol.K) indicates a bimolecular process, and O-18-labeling studies show no oxygen exchange of 1 throughout the hydrolysis by MoO42- (aq). We hypothesize primarily the monomeric molybdate is the active species at pH 7.5 where a S(N)2(P) mechanism takes place. Density functional theory methods suggest the molybdate oxoanion serves as the nucleophile to attack phosphonothioate 1 to form a molybdate-phosphonate anhydride that subsequently hydrolyzes to the starting molybdate and phenylethyl phosphonate. (C) 2017 Elsevier B.V. All rights reserved.

Kuo, L. Y., Dill, K. M., Shari'ati, Y. A., Bright, E. K., and McCormick, T.,Novel application of simple molybdates: Catalytic hydrolysis of an organophosphate neurotoxin under mild aqueous conditions, Inorganica Chimica Acta, 2017, 466, 1-7.


A new polymeric biocide polyhexamethylene guanidine (PHMG) molybdate has been synthesized. The obtained cationic polymer has limited water solubility of 0.015 g/100mL and is insoluble in paint solvents. The results of acute toxicity studies indicate moderate toxicity of PHMG molybdate, which has a median lethal dose at 48 h of 0.7 mg/L for Daphnia magna and at 96 h of 17 mg/L for Danio rerio (zebrafish) freshwater model organisms. Commercial ship paint was then modified by the addition of a low concentration of polymeric biocide 5% (w/w). The painted steel panels were kept in Dnipro River water for the evaluation of the dynamics of fouling biomass. After 129-d exposure, Bryozoa dominated in biofouling of tested substrates, forming 86% (649 g/m(2)) of the total biomass on control panel surfaces. However, considerably lower Bryozoa fouling biomass (15 g/m(2)) was detected for coatings containing PHMG molybdate. Dreissenidae mollusks were found to form 88% (2182 g/m(2)) of the fouling biomass on the control substrates after 228 d of exposure, whereas coatings containing PHMG molybdate showed a much lower biomass value of 23.6 g/m(2). The leaching rate of PHMG molybdate in water was found to be similar to rates for conventional booster biocides ranging from 5.7 mg/cm(2)/d at the initial stage to 2.2mg/cm(2)/d at steady state. (C) 2017 SETAC

Protasov, A., Bardeau, J. F., Morozovskaya, I., Boretska, M., Cherniavska, T., Petrus, L., Tarasyuk, O., Metelytsia, L., Kopernyk, I., Kalashnikova, L., Dzhuzha, O., and Rogalsky, S.,NEW PROMISING ANTIFOULING AGENT BASED ON POLYMERIC BIOCIDE POLYHEXAMETHYLENE GUANIDINE MOLYBDATE, Environmental toxicology and chemistry, 2017, 36, 2543-2551.


Redox and ligand binding reactivity in iron and chromium -substituted polyoxometalates

Using UV-vis and EPR (electron paramagnetic resonance) spectroscopy, iron- and chromium- substituted polyoxometalates were shown to undergo controlled reduction, involving the iron and chromium as well as the molybdenum/tungsten framework; furthermore, reoxidation was also shown to be possible with molecular oxygen or hydrogen peroxide in a cycle reminiscent of iron-containing enzymes. The influence of pH, ligands and/or potential redox agents such as imidazole, thiocyanate, thiosulfate, mercaptoethanol and ascorbate were examined.

Kakes, M., Cioloboc, D., Tomsa, A. R., Silaghi-Dumitrescu, R., and Damian, G.,REDOX AND LIGAND BINDING REACTIVITY IN IRON AND CHROMIUM -SUBSTITUTED POLYOXOMETALATES, Revue Roumaine De Chimie, 2015, 60, 707-720.

Quantitative measurement of Bronsted acidity by TPD of ammonia on H3 PMo12O40 and its Cs1 salt, in bulk and supported on SBA-15

The method for acidity measurement through temperature programmed desorption (TPD) of ammonia was adapted for simultaneous TG/DTG-DTA analysis of the H-3[PMo12O40] and its Cs acid salts, in bulk and supported on SBA-15 support. The desorption of NH3 consists of the NH3 and H2O release in steps as a result of temperature increase. The last step corresponds to expelling of NH3 by decomposition of species strong bonded like the ammonium cation, simultaneously with constitutive water, within the 300-600 A degrees C range. The MS analysis showed that the oxidation of ammonia to N2O and NO during desorption had occurred simultaneously with reduction of Mo6+. The reoxidation of samples with air in all cases was done finally. In order to separate the water release (water formed by condensation of hydroxyl groups belonging to SBA-15) from the ammonia desorption for supported samples, a TPD of H2O was done for every sample. In the case of pure compounds, the mass loss corresponding to the last stage of desorption (after correction with the mass loss as a result of reduction, equal with the mass increase owing to the reoxidation) gives the amounts of NH3 and constitutive water, which correspond stoichiometrically with the Bronsted acidity. The subtraction of mass loss for TPD of water from the corrected mass loss for TPD of ammonia and water (because of the mass loss as a result of the reduction) gives the amount of NH3 corresponding stoichiometrically with the Bronsted acidity. The acidic strength was estimated on the basis of the temperatures for the DTG peaks.

Sasca, V. Z., Popa, A., and Verdes, O.,Quantitative measurement of Bronsted acidity by TPD of ammonia on H-3 PMo12O40 and its Cs1 salt, in bulk and supported on SBA-15, Journal of Thermal Analysis and Calorimetry, 2016, 123, 557-569.


Time-of-flight neutron powder diffraction data have been collected from Na2MoO4 and Na2WO4 to a resolution of sin (theta)/lambda = 1.25 A(-1), which is substanti-ally better than the previous analyses using Mo Kalpha X-rays, providing roughly triple the number of measured reflections with respect to the previous studies [Okada et al. (1974 ). Acta Cryst. B30, 1872-1873; Bramnik & Ehrenberg (2004 ). Z. Anorg. Allg. Chem. 630, 1336-1341]. The unit-cell parameters are in excellent agreement with literature data [Swanson et al. (1962 ). NBS Monograph No. 25, sect. 1, pp. 46-47] and the structural parameters for the molybdate agree very well with those of Bramnik & Ehrenberg (2004 ). However, the tungstate structure refinement of Okada et al. (1974 ) stands apart as being conspicuously inaccurate, giving significantly longer W-O distances, 1.819 (8) A, and shorter Na-O distances, 2.378 (8) A, than are reported here or in other simple tungstates. As such, this work represents an order-of-magnitude improvement in precision for sodium molybdate and an equally substantial improvement in both accuracy and precision for sodium tungstate. Both compounds adopt the spinel structure type. The Na(+) ions have site symmetry .-3m and are in octa-hedral coordination while the transition metal atoms have site symmetry -43m and are in tetra-hedral coordination.

Fortes, A. D.,Crystal structures of spinel-type Na2MoO4 and Na2WO4 revisited using neutron powder diffraction, Acta Crystallogr E Crystallogr Commun, 2015, 71, 592.

Sodium molybdate - solubility

Determination and modelling for the solubility of Na2MoO4.2H2O in the (Na+ + MoO42- + SO42-) system

The solubility of Na2MoO4.2H2O in ( Na+ + MoO42- + SO42-) system was carried out using a dynamic method within the temperature range from 293.15 K to 343.15 K. The new model was established via regression of the published and the determined values to predict the solubility.

From the results, the solubility of sodium molybdate increases with the temperature increase, however, it decreases with the increasing concentration of sodium sulfate. The Pitzer parameters and the solubility product constant of sodium sulfate and sodium molybdate in aqueous solution were obtained using the literature data. The solubilities of the sodium molybdate in the sodium sulfate solution as well as the thermodynamic parameters were calculated based on the experimental values obtained. The new model was also applied to estimate the solubility of the sodium molybdate under various conditions. The calculated values agree well with the experiment results. (C) 2015 Published by Elsevier Ltd.

Ning, P. G., Xu, W. F., Cao, H. B., Lin, X., and Xu, H. B.,Determination and modeling for the solubility of Na2MoO4.2H2O in the (Na+ + MoO42- + SO42-) system, Journal of Chemical Thermodynamics, 2016, 94, 67-73.


Molybdenum disulfide Biosensor

Dual-mode electrochemical analysis of microRNA-21 using gold nanoparticle-decorated MoS2 nanosheet

The detection of microRNA plays an important role in early cancer diagnosis. Herein, a dual-mode electronic biosensor was developed for microRNA-21 (miRNA-21) detection based on gold nanoparticle-decorated MoS2 nanosheet (AuNPs@MoS2). A classical DNA "sandwich" structure was employed to construct MoS2-based electrochemical sensor, including capture DNA, target miRNA-21 and DNA-modified nanoprobe. [Fe(CN)6]3-/4- and [Ru(NH3)6]3+ were selected as electrochemical indicators to monitor the preparation process and evaluate the performance of MoS2-based electrochemical biosensor by electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV), respectively. Such MoS2-based biosensor exhibited excellent performance for miRNA-21 detection in the range from 10 fM to 1nM with detection limit of 0.78fM and 0.45fM for DPV and EIS technique, respectively. Furthermore, the proposed MoS2-based biosensor displayed high selectivity and stability, which could be used to determine miRNA-21 in human serum samples with satisfactory results. All data suggested that such MoS2-based nanocomposite may be a potential candidate for biosensing ranging from nucleic acid to protein detection.

Su, S., Cao, W., Liu, W., Lu, Z., Zhu, D., Chao, J., Weng, L., Wang, L., Fan, C., and Wang, L.,Dual-mode electrochemical analysis of microRNA-21 using gold nanopart icle-decorated MoS2 nanosheet, Biosensors & bioelectronics, 2017, 94, 552-559.


Molybdenum Sulfide: A Bioinspired Electrocatalyst for Dissimilatory Ammonia Synthesis with Geoelectrical Current

Abiotic reduction of nitrate/nitrite to ammonia in ancient ocean environments is essential for prebiotic chemical evolution and the early evolution of cellular metabolisms. Although Fe-bearing minerals have been extensively studied as reductants, the incompatibility of these reactions with the paleo-oceanic chemical conditions would have contributed only to low conversion rates. A recent model of prebiotic synthesis driven by geoelectricity suggests that less-abundant transition metals might have played a role in ammonia synthesis. Herein, we report that the electrochemical reduction of nitrate/nitrite to ammonia is effectively catalyzed by molybdenum sulfide over a wide pH range (pH 3-11). The pH dependence of the onset potential of the denitrification current indicates that this superior activity is due to the ability to induce concerted proton electron transfer (CPET), contributing to a turnover frequency comparable to those of the extant Mo dependent nitrate reductases. In a manner similar to biological dissimilatory denitrification, molybdenum sulfide catalyzes nitrite reduction to ammonia through NO and N2O intermediates, as revealed by online differential electrochemical mass spectroscopy. These findings demonstrate that molybdenum sulfide functions as a new family of bioinspired electrochemical denitrification catalysts and suggest that molybdenum, the indispensable element in extant denitrification enzymes, likely played an essential role in prebiotic ammonia synthesis with the continuous supply of geoelectrical current.

Li, Y., Yamaguchi, A., Yamamoto, M., Taka, K., and Nakamura, R.,Molybdenum Sulfide: A Bioinspired Electrocatalyst for Dissimilatory Ammonia Synthesis with Geoelectrical Current, Journal of Physical Chemistry C, 2017, 121, 2154-2164.

Structural influence of proteins upon adsorption to MoS2 nanomaterials: comparison of MoS2 force field parameters

Molybdenum disulfide (MoS2) has recently emerged as a promising nanomaterial in a wide range of applications due to its unique and impressive properties. For example, MoS2 has gained attention in the biomedical field because of its ability to act as an antibacterial and anticancer agent. However, the potential influence of this exciting nanomaterial on bioMolecules is yet to be extensively studied. Molecular dynamics (MD) simulations are invaluable tools in the examination of protein interactions with nanomaterials such as MoS2. Previous protein MD studies have employed MoS2 force field parameters which were developed to accurately Model bulk crystal structures and thermal heat transport but may not necessarily be amendable to its properties at the interface with bioMolecules. By adopting a newly developed MoS2 force field, which was designed to better capture its interaction with water and proteins, we have examined the changes in protein structures between the original and refitted MoS2 force field parameters of three representative proteins, polyalanine (alpha-helix), YAP65 WW-domains (beta-sheet), and HP35 (globular protein) when adsorbed onto MoS2 nanomaterials. We find that the original force field, with much larger van der Waals (vdW) contributions, resulted in More dramatic protein structural damage than the refitted parameters. Importantly, some denaturation of the protein tertiary structure and the local secondary structure persisted with the refitted force field albeit overall less severe MoS2 denaturation capacity was found. This work suggests that the denaturation ability of MoS2 to the protein structure is not as dire as previously reported and provides noteworthy findings on the dynamic interactions of proteins with this emergent material.

Gu, Z., De Luna, P., Yang, Z., and Zhou, R.,Structural influence of proteins upon adsorption to MoS2 nanomaterials: comparison of MoS2 force field parameters, Physical Chemistry Chemical Physics, 2017, 19, 3039-3045.

Two-dimensional MoS2: A promising building block for biosensors

Recently, two-dimensional (2D) layered nanomaterials have trigged intensive interest due to the intriguing physicochemical properties that stem from a quantum size effect connected with their ultra-thin structure. In particular, 2D molybdenum disulfide (MoS2), as an emerging class of stable inorganic graphene analogs with intrinsic finite bandgap, would possibly complement or even surpass graphene in electronics and optoelectronics fields. In this review, we first discuss the historical development of ultrathin 2D nanomaterials. Then, we are concerned with 2D MoS2 including its structure-property relationships, synthesis methods, characterization for the layer thickness, and biosensor applications over the past five years. Thereinto, we are highlighting recent advances in 2D MoS2-based biosensors, especially emphasize the preparation of sensing elements, roles of 2D MoS2, and assay strategies. Finally, on the basis of the current achievements on 2D MoS2 and other ultrathin layered nanomaterials, perspectives on the challenges and opportunities for the exploration of 2D MoS2-based biosensors are put forward.

Gan, X., Zhao, H., and Quan, X.,Two-dimensional MoS2: A promising building block for biosensors, Biosensors & bioelectronics, 2017, 89, 56-71.

MoS2 nanoparticle

Electrochemical H2O2 biosensor composed of myoglobin on MoS2 nanoparticle-graphene oxide hybrid structure

In this research, the electrochemical biosensor composed of myoglobin (Mb) on molybdenum disulfide nanoparticles (MoS2 NP) encapsulated with graphene oxide (GO) was fabricated for the detection of hydrogen peroxide (H2O2). Hybrid structure composed of MoS2 NP and GO (GO@MoS2) was fabricated for the first time to enhance the electrochemical signal of the biosensor. As a sensing material, Mb was introduced to fabricate the biosensor for H2O2 detection. Formation and immobilization of GO@MoS2 was confirmed by transmission electron microscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, and scanning tunneling microscopy. Immobilization of Mb, and electrochemical property of biosensor were investigated by cyclic voltammetry and amperometric i-t measurements. Fabricated biosensor showed the electrochemical signal enhanced redox current as -1.86muA at an oxidation potential and 1.95muA at a reduction potential that were enhanced relative to those of electrode prepared without GO@MoS2. Also, this biosensor showed the reproducibility of electrochemical signal, and retained the property until 9 days from fabrication. Upon addition of H2O2, the biosensor showed enhanced amperometric response current with selectivity relative to that of the biosensor prepared without GO@MoS2. This novel hybrid material-based biosensor can suggest a milestone in the development of a highly sensitive detecting platform for biosensor fabrication with highly sensitive detection of target molecules other than H2O2.

Yoon, J., Lee, T., Bapurao, G. B., Jo, J., Oh, B. K., and Choi, J. W.,Electrochemical H2O2 biosensor composed of myoglobin on MoS2 nanoparticle-graphene oxide hybrid structure, Biosensors & bioelectronics, 2016.


2D molybdenum disulfide graphene oxide

Antibacterial Activities of Graphene Oxide-Molybdenum Disulfide Nanocomposite Films

Two-dimensional (2D) nanomaterials, such as graphene-based materials and transition metal dichalcogenide (TMD) nanosheets, are promising materials for biomedical applications owing to their remarkable cytocompatibility and physicochemical properties.

On the basis of their potent antibacterial properties, 2D materials have potential as antibacterial films, wherein the 2D nanosheets are immobilized on the surface and the bacteria may contact with the basal planes of 2D nanosheets dominantly rather than contact with the sharp edges of nanosheets.

To address these points, in this study, we prepared an effective antibacterial surface consisting of representative 2D materials, i.e., graphene oxide (GO) and molybdenum disulfide (MoS2), formed into nanosheets on a transparent substrate for real device applications.

The antimicrobial properties of the GO-MoS2 nanocomposite surface toward the Gram-negative bacteria Escherichia coli were investigated, and the GO-MoS2 nanocomposite exhibited enhanced antimicrobial effects with increased glutathione oxidation capacity and partial conductivity.

Furthermore, direct imaging of continuous morphological destruction in the individual bacterial cells having contacts with the GO-MoS2 nanocomposite surface was characterized by holotomographic (HT) microscopy, which could be used to detect the refractive index (RI) distribution of each voxel in bacterial cell and reconstruct the three-dimensional (3D) mapping images of bacteria. In this regard, the decreases in both the volume (67.2%) and the dry mass (78.8%) of bacterial cells that came in contact with the surface for 80 min were quantitatively measured, and releasing of intracellular components mediated by membrane and oxidative stress was observed.

Our findings provided new insights into the antibacterial properties of 2D nanocomposite film with label-free tracing of bacterial cell which improve our understanding of antimicrobial activities and opened a window for the 2D nanocomposite as a practical antibacterial film in biomedical applications.

Kim, T. I., Kwon, B., Yoon, J., Park, I. J., Bang, G. S., Park, Y., Seo, Y. S., and Choi, S. Y.,Antibacterial Activities of Graphene Oxide-Molybdenum Disulfide Nanocomposite Films, ACS Appl Mater Interfaces, 2017.


Versatile molybdenum disulfide based antibacterial composites for in vitro enhanced sterilization and in vivo focal infection therapy

Biologically, MoS2-based nanostructures have been intensely applied for the photothermal therapy of cancer, but rarely for antibacterial uses. In this contribution, a multifunctional chitosan (CS) functionalized magnetic MoS2 (abbreviated to CFM) was constructed to nonspecifically combat bacterial infection by integrating bacterial conjugation and enrichment, and NIR-triggered photothermal sterilization. Owing to the abundant introduced amino groups, the CFM complex offers a significantly enhanced conjugation efficiency without obvious specificity towards both Gram-positive and -negative bacteria compared to amino-free magnetic MoS2. The magnetic properties of CFM obtained from iron oxide facilitate the enrichment of a CFM-bacteria conjugate, improving the photothermal efficiency of CFM as a photothermal antibacterial agent. Specifically, after being trapped together with bacteria cells, CFM shows an enhanced in vitro photothermal sterilization ability. In vivo S. aureus-induced abscess treatment studies show faster healing when CFM is used as subcutaneous nano-localized heating sources with the assistance of an external magnet to concentrate the CFM-bacteria conjugate. This work establishes an innovative solution and a novel antimicrobial agent for combating bacterial infections without the use of antibiotics, which may open a new area of application and research for MoS2-based nanostructures.

Zhang, W., Shi, S., Wang, Y., Yu, S., Zhu, W., Zhang, X., Zhang, D., Yang, B., Wang, X., and Wang, J.,Versatile molybdenum disulfide based antibacterial composites for in vitro enhanced sterilization and in vivo focal infection therapy, Nanoscale, 2016, 8, 11642-8.


Functionalized Nano-MoS2 with Peroxidase Catalytic and Near-Infrared Photothermal Activities for Safe and Synergetic Wound Antibacterial Applications

We have developed a biocompatible antibacterial system based on polyethylene glycol functionalized molybdenum disulfide nanoflowers (PEG-MoS2 NFs). The PEG-MoS2 NFs have high near-infrared (NIR) absorption and peroxidase-like activity, which can efficiently catalyze decomposition of low concentration of H2O2 to generate hydroxyl radicals (.OH). The conversion of H2O2 into .OH can avoid the toxicity of high concentration of H2O2 and the .OH has higher antibacterial activity, making resistant bacteria more vulnerable and wounds more easily cured.

The PEG-MoS2 NFs combine the catalysis with NIR photothermal effect, providing a rapid and effective killing outcome in vitro for Gram-negative ampicillin resistant Escherichia coli (Ampr E. coli) and Gram-positive endospore-forming Bacillus subtilis (B. subtilis) as compared to catalytic treatment or photothermal therapy (PTT) alone.

Wound healing results indicate that the synergy antibacterial system could be conveniently used for wound disinfection in vivo.

Interestingly, glutathione (GSH) oxidation can be accelerated due to the 808 nm irradiation induced hyperthermia at the presence of PEG-MoS2 NFs proved by X-ray near-edge absorption spectra and X-ray spectroscopy.

The accelerated GSH oxidation can result in bacterial death more easily. A mechanism based on .OH-enhanced PTT is proposed to explain the antibacterial process.

Yin, W., Yu, J., Lv, F., Yan, L., Zheng, L. R., Gu, Z., and Zhao, Y.,Functionalized Nano-MoS2 with Peroxidase Catalytic and Near-Infrared Photothermal Activities for Safe and Synergetic Wound Antibacterial Applications, ACS nano, 2016, 10, 11000-11011.