The mining and leakage of molybdenum (Mo) can cause environmental contamination which has not been realized until recently. Bacteria that can mitigate Mo-contamination was enriched and isolated. The ...low temperature and different pH conditions were considered to analysis its feasibility in Northern China which suffers from a long time of low temperatures every year. The result showed that the removal rate of MoO.sub.4.sup.2- by Raoultella ornithinolytica A1 reached 30.46% at 25 °C and pH 7.0 in Luria-Bertani medium (LB). Meanwhile, A1 also showed some efficiency in the reduction of MoO.sub.4.sup.2- in low phosphate molybdate medium (LPM), which reached optimum at the MoO.sub.4.sup.2- concentration of 10 mM. The results of FTIR indicated that the cell wall performed an essential role in the MoO.sub.4.sup.2- removal process, which was illustrated by the distribution of Mo in A1 (Mo bound to cell wall accounted for 92.29% of the total MoO.sub.4.sup.2- removed). In addition, low temperature (10 °C) effect the removal rate of MoO.sub.4.sup.2- by - 8.38 to 11.66%, indicating the potential for the in-situ microbial remediation of Mo-contaminated environments in low temperature areas. Graphical abstract
Molybdenum disulfide (MoS2) is one of the compounds discussed nowadays due to its outstanding properties that allowed its usage in different applications. Its band gap and its distinctive structure ...make it a promising material to substitute graphene and other semiconductor devices. It has different applications in electronics especially sensors like optical sensors, biosensors, electrochemical biosensors that play an important role in the detection of various diseases’ like cancer and Alzheimer. It has a wide range of energy applications in batteries, solar cells, microwave, and Terahertz applications. It is a promising material on a nanoscale level, with favorable characteristics in spintronics and magnetoresistance. In this review, we will discuss MoS2 properties, structure and synthesis techniques with a focus on its applications and future challenges.
Many nanoscale biomaterials fail to reach the clinical trial stage due to a poor understanding of the fundamental principles of their in vivo behaviour. Here we describe the transport, transformation ...and bioavailability of MoS
nanomaterials through a combination of in vivo experiments and molecular dynamics simulations. We show that after intravenous injection molybdenum is significantly enriched in liver sinusoid and splenic red pulp. This biodistribution is mediated by protein coronas that spontaneously form in the blood, principally with apolipoprotein E. The biotransformation of MoS
leads to incorporation of molybdenum into molybdenum enzymes, which increases their specific activities in the liver, affecting its metabolism. Our findings reveal that nanomaterials undergo a protein corona-bridged transport-transformation-bioavailability chain in vivo, and suggest that nanomaterials consisting of essential trace elements may be converted into active biological molecules that organisms can exploit. Our results also indicate that the long-term biotransformation of nanomaterials may have an impact on liver metabolism.
The magnetoelectric (ME) effect, the phenomenon of inducing magnetization by application of an electric field or vice versa, holds great promise for magnetic sensing and switching applications. ...Studies of the ME effect have so far focused on the control of the electron spin degree of freedom (DOF) in materials such as multiferroics and conventional semiconductors. Here, we report a new form of the ME effect based on the valley DOF in two-dimensional Dirac materials. By breaking the three-fold rotational symmetry in single-layer MoS
via a uniaxial stress, we have demonstrated the pure electrical generation of valley magnetization in this material, and its direct imaging by Kerr rotation microscopy. The observed out-of-plane magnetization is independent of in-plane magnetic field, linearly proportional to the in-plane current density, and optimized when the current is orthogonal to the strain-induced piezoelectric field. These results are fully consistent with a theoretical model of valley magnetoelectricity driven by Berry curvature effects. Furthermore, the effect persists at room temperature, opening possibilities for practical valleytronic devices.
Water electrolysis has been considered as a sustainable way for producing renewable energy of hydrogen. However, this process requires a low-cost and high-efficient hydrogen evolution reaction (HER) ...catalyst to improve the overall reaction efficiency. Molybdenum (Mo)-based electrocatalysts are regarded as the promising candidates to replace the benchmark but expensive Pt-based HER catalysts, due to their high activity and stability in a wide pH range. In this review, we present a comprehensive and critical summary on the recent progress in the Mo-based electrodes for HER, including molybdenum alloys, molybdenum sulfides, molybdenum selenides, molybdenum carbides, molybdenum phosphides, molybdenum borides, molybdenum nitrides, and molybdenum oxides. Particular attention is mainly focused on the synthetic methods of Mo-based materials, the strategies for increasing the catalytic activity, and the relationship between structure/composition and electrocatalytic performance. Finally, the future development and perspectives of Mo-based electrocatalysts toward high HER performance are proposed.
Graphic abstract
MoS2 has emerged as a promising alternative electrocatalyst for the hydrogen evolution reaction (HER) due to high intrinsic per‐site activity on its edge sites and S‐vacancies. However, a significant ...challenge is the limited density of such sites. Reducing the size and layer number of MoS2 and vertically aligning them would be an effective way to enrich and expose such sites for HER. Herein, a facile self‐limited on‐site conversion strategy for synthesizing monolayer MoS2 in a couple of nanometers which are highly dispersed and vertically aligned on 3D porous carbon sheets is reported. It is discovered that the preformation of well‐dispersed MoO3 nanodots in 1–2 nm as limited source is the key for the fabrication of such an ultrasmall MoS2 monolayer. As indicated by X‐ray photoelectron spectroscopy and electron spin resonance data, these ultrasmall MoS2 monolayers are rich in accessible S‐edge sites and vacancies and the smaller MoS2 monolayers the more such sites they have, leading to enhanced electrocatalytic activity with a low overpotential of 126 mV at 10 mA cm−2 and 140 mV at 100 mA mg−1 for HER. This state‐of‐the‐art performance for MoS2 electrocatalysts enables the present strategy as a new avenue for exploring well‐dispersed ultrasmall nanomaterials as efficient catalysts.
An ultrasmall MoS2 monolayer well‐dispersed and vertically aligned on porous carbon is developed via a self‐limited on‐site fabrication strategy. It exhibits excellent and size‐dependent electrocatalytic performance for hydrogen evolution with an ultralow overpotential of 126 and 140 mV at 10 mV cm−2 and 100 mA mg−1, respectively.
The generation of hydrogen through water electrolysis is considered as a sustainable approach for future fuel production. Molybdenum (Mo)‐based compounds are reported as highly active and inexpensive ...alternatives to platinum‐based electrocatalysts for the hydrogen evolution reaction (HER). Currently, the major challenge for Mo‐based HER electrocatalysts lies in establishing new concepts of micro‐/nanostructure design to enhance the hydrogen evolution kinetics and realizing facile, large‐scale, and green fabrication processes. Here, a fast, scalable, and eco‐friendly metal‐organic coordination precursor–assisted strategy is reported for synthesizing novel hierarchically mesoporous Mo‐based carbon electrocatalysts for efficient hydrogen production. Benefiting from homogeneously distributed Mo‐based nanocrystallites/heterojunctions and uniform mesopores, the Mo‐based mesoporous electrocatalyst shows high hydrogen evolution activity and stability with a low overpotential of 222 mV at 100 mA cm−2 (Pt/C: 263 mV), ranging among the best non‐noble metal HER catalysts in alkaline condition. Overall, the discovery of using dopamine–molybdate coordination precursor with silica nanoparticles will not only create a new pathway for controllable synthesis of diverse kinds of micro‐/nanostructured Mo‐based catalysts, but also take a step toward the fast and scale‐up production of advanced mesoporous carbon electrodes for a broad range of applications.
Molybdenum (Mo)‐based nanocrystallites/heterojunctions and hierarchically mesoporous structured carbon spheres are synthesized by a facile and scalable templating approach using a metal‐organic precursor (dopamine–molybdate with silica nanoparticles). The Mo‐based mesoporous electrocatalyst shows superior hydrogen evolution activity and stability with a low overpotential of 222 mV at 100 mA cm−2 (Pt/C: 263 mV) in alkaline conditions.
A MoS2(1‐x)Px solid solution (x = 0 to 1) is formed by thermally annealing mixtures of MoS2 and red phosphorus. The effective and stable electrocatalyst for hydrogen evolution in acidic solution ...holds promise for replacing scarce and expensive platinum that is used in present catalyst systems. The high performance originates from the increased surface area and roughness of the solid solution.
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.
A photothermal nanoagent has been developed, namely degradable PEGylated molybdenum oxide, with strong near‐IR absorbance, high drug loading capability, and pH‐dependent degradation. It can be rapidly excreted from the body after intravenous injection and shows no appreciable in vivo toxicity. It also shows effective accumulation and retention in the tumor, which can then be eliminated by photothermal therapy treatment.
Robustly integrated electrodes constructed by well‐organized building blocks of active materials are appealing in versatile electrochemical systems. Herein, orderly oriented nanowire arrays (NWAs) of ...multiple molybdenum‐based compounds (MoXn, MoXn = MoP, MoS2, Mo2C, MoN, and MoO2) on carbon fiber paper (CFP) are generally fabricated by topotactic transformations from molybdenum‐containing precursor NWAs. Extensive structural characterizations reveal that these MoXn nanowires are composed of either closely interconnected nanoparticles or edge‐rich nanosheets. When being used as self‐supported electrodes, these MoXn NWAs/CFP exhibit excellent catalytic activities and stabilities toward hydrogen evolution reaction (HER) in pH‐universal electrolytes. Especially, the best‐performed MoP NWAs/CFP shows comparable or even superior HER performance over platinum benchmark, which holds great promises in HER‐related energy technologies. This work presents a simple yet effective approach toward general synthesis of self‐supported Mo‐based NWAs on CFP, which also possesses huge application prospects in other fields, such as supercapacitors, batteries, and sensors.
Nanowire arrays (NWAs) of MoP, MoS2, Mo2C, MoN, and MoO2 are generally synthesized through topotactic transformation from molybdenum‐containing precursor NWAs mounted on carbon fiber paper. Benefiting from the structural advantages, these self‐supported molybdenum‐based NWAs electrodes exhibit excellent electrocatalytic performance toward HER in pH‐universal electrolytes.
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