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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 MoS2 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 MoS2 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.Understanding the in vivo biotransformation of nanomaterials used for biomedical applications might shed light on their long-term effects and safety. Here the authors show that molybdenum derived from nanomaterials is mainly transported in the liver, in a corona-mediated process, and is incorporated in molybdoenzymes, with an effect on liver metabolism.

Monolayer transition metal dichalcogenides (TMDs) have become essential two-dimensional materials for their perspectives in engineering next-generation electronics. For related applications, the controlled growth of large-area uniform monolayer TMDs is crucial, while it remains challenging. Herein, we report the direct synthesis of 6-inch uniform monolayer molybdenum disulfide on the solid soda-lime glass, through a designed face-to-face metal-precursor supply route in a facile chemical vapor deposition process. We find that the highly uniform monolayer film, with the composite domains possessing an edge length larger than 400 µm, can be achieved within a quite short time of 8 min. This highly efficient growth is proven to be facilitated by sodium catalysts that are homogenously distributed in glass, according to our experimental facts and density functional theory calculations. This work provides insights into the batch production of highly uniform TMD films on the functional glass substrate with the advantages of low cost, easily transferrable, and compatible with direct applications. Growth of large-area monolayer transition metal dichalcogenides is critical for their application but remains challenging. Here Yang et al. report rapid chemical vapor deposition of 6-inch monolayer molybdenum disulfide by sufficiently uniformly supplying the precursors and catalysts.

Catalysis of the reduction of nitrogen to ammonia under mild conditions by a tris(phosphine)borane-supported iron complex indicates that a single iron site may be capable of stabilizing the various N x H y intermediates generated during catalytic ammonia formation. In search of an easy fix for nitrogen Industrial nitrogen fixation is performed on a vast scale by the Haber–Bosch process, which uses a solid-state iron catalyst at very high temperatures and pressures. Synthetic chemists have searched for decades for small metal-containing complexes to catalyse the transformation of nitrogen into ammonia in less extreme conditions, taking their lead from the nitrogenases found in plants and bacteria. To that end Jonas Peters and colleagues describe a tris(phosphine)borane-supported iron complex that catalyses the reduction of nitrogen into ammonia under mild conditions with reasonable efficiency. This suggests that a single iron site is sufficient for mediating nitrogen fixation, in line with recent biochemical and spectroscopic data that point to iron rather than the molybdenum also present in the FeMo cofactor or nitrogenase as the site of nitrogen binding and activation. The reduction of nitrogen (N 2 ) to ammonia (NH 3 ) is a requisite transformation for life 1 . Although it is widely appreciated that the iron-rich cofactors of nitrogenase enzymes facilitate this transformation 2 , 3 , 4 , 5 , how they do so remains poorly understood. A central element of debate has been the exact site or sites of N 2 coordination and reduction 6 , 7 . In synthetic inorganic chemistry, an early emphasis was placed on molybdenum 8 because it was thought to be an essential element of nitrogenases 3 and because it had been established that well-defined molybdenum model complexes could mediate the stoichiometric conversion of N 2 to NH 3 (ref. 9 ). This chemical transformation can be performed in a catalytic fashion by two well-defined molecular systems that feature molybdenum centres 10 , 11 . However, it is now thought that iron is the only transition metal essential to all nitrogenases 3 , and recent biochemical and spectroscopic data have implicated iron instead of molybdenum as the site of N 2 binding in the FeMo-cofactor 12 . Here we describe a tris(phosphine)borane-supported iron complex that catalyses the reduction of N 2 to NH 3 under mild conditions, and in which more than 40 per cent of the proton and reducing equivalents are delivered to N 2 . Our results indicate that a single iron site may be capable of stabilizing the various N x H y intermediates generated during catalytic NH 3 formation. Geometric tunability at iron imparted by a flexible iron–boron interaction in our model system seems to be important for efficient catalysis 13 , 14 , 15 . We propose that the interstitial carbon atom recently assigned in the nitrogenase cofactor may have a similar role 16 , 17 , perhaps by enabling a single iron site to mediate the enzymatic catalysis through a flexible iron–carbon interaction 18 .

The Fe–S clusters of nitrogenases carry out the life-sustaining conversion of N2 to NH3. Although progress continues to be made in modelling the structural features of nitrogenase cofactors, no synthetic Fe–S cluster has been shown to form a well-defined coordination complex with N2. Here we report that embedding an [MoFe3S4] cluster in a protective ligand environment enables N2 binding at Fe. The bridging [MoFe3S4]2(μ-η1:η1-N2) complex thus prepared features a substantially weakened N–N bond despite the relatively high formal oxidation states of the metal centres. Substitution of one of the [MoFe3S4] cubanes with an electropositive Ti metalloradical induces additional charge transfer to the N2 ligand with generation of Fe–N multiple-bond character. Structural and spectroscopic analyses demonstrate that N2 activation is accompanied by shortened Fe–S distances and charge transfer from each Fe site, including those not directly bound to N2. These findings indicate that covalent interactions within the cluster play a critical role in N2 binding and activation.Although iron–sulfur cofactors are known to carry out biological nitrogen fixation, how these clusters bind dinitrogen remains poorly understood. Now, a dinitrogen complex of a synthetic iron–sulfur cluster has been characterized, and electronic cooperation in the cluster has been shown to result in strong N–N bond activation.

Graphene has attracted considerable interest for future electronics, but the absence of a bandgap limits its direct applicability in transistors and logic devices. Recently, other layered materials such as molybdenum disulphide (MoS 2 ) have been investigated to address this challenge. Here, we report the vertical integration of multi-heterostructures of layered materials for the fabrication of a new generation of vertical field-effect transistors (VFETs) with a room temperature on–off ratio > 10 3 and a high current density of up to 5,000 A cm −2 . An n-channel VFET is created by sandwiching few-layer MoS 2 as the semiconducting channel between a monolayer graphene sheet and a metal thin film. This approach offers a general strategy for the vertical integration of p- and n-channel transistors for high-performance logic applications. As an example, we demonstrate a complementary inverter with a larger-than-unity voltage gain by vertically stacking graphene, Bi 2 Sr 2 Co 2 O 8 (p-channel), graphene, MoS 2 (n-channel) and a metal thin film in sequence. The ability to simultaneously achieve a high on–off ratio, a high current density and a logic function in such vertically stacked multi-heterostructures can open up possibilities for three-dimensional integration in future electronics. Graphene has attracted considerable interest for future electronics, but the absence of a bandgap limits its direct applicability in transistors and logic devices. It is now shown that vertical integration with MoS 2 and other layered materials enables the fabrication of vertical field-effect transistors with large on/off ratios and high current densities as well as complementary inverters with larger-than-unity voltage gain.

The optimization of the enzyme-like catalytic selectivity of nanozymes for specific reactive oxygen species (ROS)-related applications is significant, and meanwhile the real-time monitoring of ROS is really crucial for tracking the therapeutic process. Herein, we present a mild oxidation valence-engineering strategy to modulate the valence states of Mo in Pluronic F127-coated MoO 3-x nanozymes (denoted as MF-x, x: oxidation time) in a controlled manner aiming to improve their specificity of H 2 O 2 -associated catalytic reactions for specific therapy and monitoring of ROS-related diseases. Experimentally, MF-0 (Mo average valence 4.64) and MF-10 (Mo average valence 5.68) exhibit exclusively optimal catalase (CAT)- or peroxidase (POD)-like activity, respectively. Density functional theory (DFT) calculations verify the most favorable reaction path for both MF-0- and MF-10-catalyzed reaction processes based on free energy diagram and electronic structure analysis, disclosing the mechanism of the H 2 O 2 activation pathway on the Mo-based nanozymes. Furthermore, MF-0 poses a strong potential in acute kidney injury (AKI) treatment, achieving excellent therapeutic outcomes in vitro and in vivo. Notably, the ROS-responsive photoacoustic imaging (PAI) signal of MF-0 during treatment guarantees real-time monitoring of the therapeutic effect and post-cure assessment in vivo, providing a highly desirable non-invasive diagnostic approach for ROS-related diseases. Nanozymes can mimic the activity of natural enzymes but are limited by poor reaction selectivity due to the lack of enzyme-like molecular recognition units as in natural enzymes. Here, the authors present a mild oxidation valence-engineering strategy to modulate the valence states of Mo in Pluronic F127-coated MoO 3-x nanozymes and show they can exhibit exclusive catalase- or peroxidase-like activities.

Layered materials of graphene and MoS 2 , for example, have recently emerged as an exciting material system for future electronics and optoelectronics. Vertical integration of layered materials can enable the design of novel electronic and photonic devices. Here, we report highly efficient photocurrent generation from vertical heterostructures of layered materials. We show that vertically stacked graphene–MoS 2 –graphene and graphene–MoS 2 –metal junctions can be created with a broad junction area for efficient photon harvesting. The weak electrostatic screening effect of graphene allows the integration of single or dual gates under and/or above the vertical heterostructure to tune the band slope and photocurrent generation. We demonstrate that the amplitude and polarity of the photocurrent in the gated vertical heterostructures can be readily modulated by the electric field of an external gate to achieve a maximum external quantum efficiency of 55% and internal quantum efficiency up to 85%. Our study establishes a method to control photocarrier generation, separation and transport processes using an external electric field. Efficient photocurrent generation, which can be tuned by the electric field of a gate to reach both high external and internal quantum efficiencies, is shown to occur in vertical heterostructures comprising graphene, MoS 2 and metals.

The reduction of N 2 by iron and molybdenum complexes is a rapidly moving field. This Perspective discusses the key advances in the past two years. The recent discovery of carbide at the centre of the iron-molybdenum cofactor of nitrogenase is also described, along with the most compelling areas for continued research. The reduction of gaseous nitrogen is a challenge for industrial, biological and synthetic chemists. Major goals include understanding the formation of ammonia for agriculture, and forming N–C and N–Si bonds for the synthesis of fine chemicals. The iron–molybdenum active site of the enzyme nitrogenase has inspired chemists to explore iron and molybdenum complexes in transformations related to N 2 reduction. This area of research has gained significant momentum, and the past two years have witnessed a number of significant advances in synthetic Fe–N 2 and Mo–N 2 chemistry. Furthermore, the identities of all atoms in the iron–molybdenum cofactor of nitrogenase have finally been elucidated, and the discovery of a carbide has generated new questions and targets for coordination chemists. This Perspective summarizes the recent work on iron and molydenum complexes, and highlights the opportunities for continued research.

The synthesis of transition metal–dinitrogen complexes and the stoichiometric transformation of their coordinated dinitrogen into ammonia and hydrazine have been the subject of considerable research, with a view to achieving nitrogen fixation under ambient conditions. Since a single example in 2003, no examples have been reported of the catalytic conversion of dinitrogen into ammonia under ambient conditions. The dimolybdenum–dinitrogen complex bearing PNP pincer ligands was found to work as an effective catalyst for the formation of ammonia from dinitrogen, with 23 equiv. of ammonia being produced with the catalyst (12 equiv. of ammonia are produced based on the molybdenum atom of the catalyst). This is another successful example of the catalytic and direct conversion of dinitrogen into ammonia under ambient reaction conditions. We believe that the results described in this Article provide valuable information with which to develop a more effective nitrogen-fixation system under mild reaction conditions. Nitrogen fixing is an extremely energy-consuming industrial process so there is much effort underway to develop better catalytic methods. Now, a dimolybdenum–dinitrogen complex bearing a PNP pincer ligand has been found to work as an effective catalyst for the formation of ammonia from dinitrogen.