Two-Dimensional MoS2 Nanosheets Derived from Cathodic Exfoliation for Lithium Storage Applications.

The preparation of 2H-phase MoS2 thin nanosheets by electrochemical delamination remains a challenge, despite numerous efforts in this direction. In this work, by choosing appropriate intercalating cations for cathodic delamination, the insertion process was facilitated, leading to a higher degree of exfoliation while maintaining the original 2H-phase of the starting bulk MoS2 material. Specifically, trimethylalkylammonium cations were tested as electrolytes, outperforming their bulkier tetraalkylammonium counterparts, which have been the focus of past studies. The performance of novel electrochemically derived 2H-phase MoS2 nanosheets as electrode material for electrochemical energy storage in lithium-ion batteries was investigated. The lower thickness and thus higher flexibility of cathodically exfoliated MoS2 promoted better electrochemical performance compared to liquid-phase and ultrasonically assisted exfoliated MoS2, both in terms of capacity (447 vs. 371 mA·h·g-1 at 0.2 A·g-1) and rate capability (30% vs. 8% capacity retained when the current density was increased from 0.2 A·g-1 to 5 A·g-1), as well as cycle life (44% vs. 17% capacity retention at 0.2 A·g-1 after 580 cycles). Overall, the present work provides a convenient route for obtaining MoS2 thin nanosheets for their advantageous use as anode material for lithium storage.

Understanding how junction resistances impact the conduction mechanism in nano-networks.

Networks of nanowires, nanotubes, and nanosheets are important for many applications in printed electronics. However, the network conductivity and mobility are usually limited by the resistance between the particles, often referred to as the junction resistance. Minimising the junction resistance has proven to be challenging, partly because it is difficult to measure. Here, we develop a simple model for electrical conduction in networks of 1D or 2D nanomaterials that allows us to extract junction and nanoparticle resistances from particle-size-dependent DC network resistivity data. We find junction resistances in porous networks to scale with nanoparticle resistivity and vary from 5 Ω for silver nanosheets to 24 GΩ for WS2 nanosheets. Moreover, our model allows junction and nanoparticle resistances to be obtained simultaneously from AC impedance spectra of semiconducting nanosheet networks. Through our model, we use the impedance data to directly link the high mobility of aligned networks of electrochemically exfoliated MoS2 nanosheets (≈ 7 cm2 V-1 s-1) to low junction resistances of ∼2.3 MΩ. Temperature-dependent impedance measurements also allow us to comprehensively investigate transport mechanisms within the network and quantitatively differentiate intra-nanosheet phonon-limited bandlike transport from inter-nanosheet hopping.

Documenting the de-identification process of clinical and imaging data for AI for health imaging projects.

Artificial intelligence (AI) is revolutionizing the field of medical imaging, holding the potential to shift medicine from a reactive "sick-care" approach to a proactive focus on healthcare and prevention. The successful development of AI in this domain relies on access to large, comprehensive, and standardized real-world datasets that accurately represent diverse populations and diseases. However, images and data are sensitive, and as such, before using them in any way the data needs to be modified to protect the privacy of the patients. This paper explores the approaches in the domain of five EU projects working on the creation of ethically compliant and GDPR-regulated European medical imaging platforms, focused on cancer-related data. It presents the individual approaches to the de-identification of imaging data, and describes the problems and the solutions adopted in each case. Further, lessons learned are provided, enabling future projects to optimally handle the problem of data de-identification. CRITICAL RELEVANCE STATEMENT: This paper presents key approaches from five flagship EU projects for the de-identification of imaging and clinical data offering valuable insights and guidelines in the domain. KEY POINTS: ΑΙ models for health imaging require access to large amounts of data. Access to large imaging datasets requires an appropriate de-identification process. This paper provides de-identification guidelines from the AI for health imaging (AI4HI) projects.

Quantitative analysis of printed nanostructured networks using high-resolution 3D FIB-SEM nanotomography.

Networks of solution-processed nanomaterials are becoming increasingly important across applications in electronics, sensing and energy storage/generation. Although the physical properties of these devices are often completely dominated by network morphology, the network structure itself remains difficult to interrogate. Here, we utilise focused ion beam - scanning electron microscopy nanotomography (FIB-SEM-NT) to quantitatively characterise the morphology of printed nanostructured networks and their devices using nanometre-resolution 3D images. The influence of nanosheet/nanowire size on network structure in printed films of graphene, WS2 and silver nanosheets (AgNSs), as well as networks of silver nanowires (AgNWs), is investigated. We present a comprehensive toolkit to extract morphological characteristics including network porosity, tortuosity, specific surface area, pore dimensions and nanosheet orientation, which we link to network resistivity. By extending this technique to interrogate the structure and interfaces within printed vertical heterostacks, we demonstrate the potential of this technique for device characterisation and optimisation.

Mechanical Properties of Conducting Printed Nanosheet Network Thin Films Under Uniaxial Compression.

Thin film networks of solution processed nanosheets show remarkable promise for use in a broad range of applications including strain sensors, energy storage, printed devices, textile electronics, and more. While it is known that their electronic properties rely heavily on their morphology, little is known of their mechanical nature, a glaring omission given the effect mechanical deformation has on the morphology of porous systems and the promise of mechanical post processing for tailored properties. Here, this work employs a recent advance in thin film mechanical testing called the Layer Compression Test to perform the first in situ analysis of printed nanosheet network compression. Due to the well-defined deformation geometry of this unique test, this work is able to explore the out-of-plane elastic, plastic, and creep deformation in these systems, extracting properties of elastic modulus, plastic yield, viscoelasticity, tensile failure and sheet bending vs. slippage under both out of plane uniaxial compression and tension. This work characterizes these for a range of networks of differing porosities and sheet sizes, for low and high compression, as well as the effect of chemical cross linking. This work explores graphene and MoS2 networks, from which the results can be extended to printed nanosheet networks as a whole.

Solution-Processed Heterojunction Photodiodes Based on WSe2 Nanosheet Networks.

Solution-processed photodetectors incorporating liquid-phase-exfoliated transition metal dichalcogenide nanosheets are widely reported. However, previous studies mainly focus on the fabrication of photoconductors, rather than photodiodes which tend to be based on heterojunctions and are harder to fabricate. Especially, there are rare reports on introducing commonly used transport layers into heterojunctions based on nanosheet networks. In this study, a reliable solution-processing method is reported to fabricate heterojunction diodes with tungsten selenide (WSe2 ) nanosheets as the optical absorbing material and PEDOT: PSS and ZnO as injection/transport-layer materials. By varying the transport layer combinations, the obtained heterojunctions show rectification ratios of up to ≈104 at ±1 V in the dark, without relying on heavily doped silicon substrates. Upon illumination, the heterojunction can be operated in both photoconductor and photodiode modes and displays self-powered behaviors at zero bias.

NbSe2 Nanosheets/Nanorolls Obtained via Fast and Direct Aqueous Electrochemical Exfoliation for High-Capacity Lithium Storage.

Layered transition-metal dichalcogenides (LTMDs) in two-dimensional (2D) form are attractive for electrochemical energy storage, but research efforts in this realm have so far largely focused on the best-known members of such a family of materials, mainly MoS2, MoSe2, and WS2. To exploit the potential of further, currently less-studied 2D LTMDs, targeted methods for their production, preferably by cost-effective and sustainable means, as well as control over their nanomorphology, are highly desirable. Here, we report a quick and straightforward route for the preparation of 2D NbSe2 and other metallic 2D LTMDs that relies on delaminating their bulk parent solid under aqueous cathodic conditions. Unlike typical electrochemical exfoliation methods for 2D materials, which generally require an additional processing step (e.g., sonication) to complete delamination, the present electrolytic strategy yielded directly exfoliated nano-objects in a very short time (1-2 min) and with significant yields (∼16 wt %). Moreover, the dominant morphology of the exfoliated 2D NbSe2 products could be tuned between rolled-up nanosheets (nanorolls) and unfolded nanosheets, depending on the solvent where the nano-objects were dispersed (water or isopropanol). This rather unusual delamination behavior of NbSe2 was explored and concluded to occur via a redox mechanism that involves some degree of hydrolytic oxidation of the material triggered by the cathodic treatment. The delamination strategy could be extended to other metallic LTMDs, such as NbS2 and VSe2. When tested toward electrochemical lithium storage, electrodes based on the exfoliated NbSe2 products delivered very high capacity values, up to 750-800 mA h g-1 at 0.5 A g-1, where the positive effect of the nanoroll morphology, associated to increased accessibility of the lithium storage sites, was made apparent. Overall, these results are expected to expand the availability of fit-for-purpose 2D LTMDs by resorting to simple and expeditious production strategies of low environmental impact.

High-Mobility Flexible Transistors with Low-Temperature Solution-Processed Tungsten Dichalcogenides.

The investigation of high-mobility two-dimensional (2D) flakes beyond molybdenum disulfide (MoS2) will be necessary to create a library of high-mobility solution-processed networks that conform to substrates and remain functional over thousands of bending cycles. Here we report electrochemical exfoliation of large-aspect-ratio (>100) semiconducting flakes of tungsten diselenide (WSe2) and tungsten disulfide (WS2) as well as MoS2 as a comparison. We use Langmuir-Schaefer coating to achieve highly aligned and conformal flake networks, with minimal mesoporosity (∼2-5%), at low processing temperatures (120 °C) and without acid treatments. This allows us to fabricate electrochemical transistors in ambient air, achieving average mobilities of µMoS2 ≈ 11 cm2 V-1 s-1, µWS2 ≈ 9 cm2 V-1 s-1, and µWSe2 ≈ 2 cm2 V-1 s-1 with a current on/off ratios of Ion/Ioff ≈ 2.6 × 103, 3.4 × 103, and 4.2 × 104 for MoS2, WS2, and WSe2, respectively. Moreover, our transistors display threshold voltages near ∼0.4 V with subthreshold slopes as low as 182 mV/dec, which are essential factors in maintaining power efficiency and represent a 1 order of magnitude improvement in the state of the art. Furthermore, the performance of our WSe2 transistors is maintained on polyethylene terephthalate (PET) even after 1000 bending cycles at 1% strain.

Solution processed, vertically stacked hetero-structured diodes based on liquid-exfoliated WS2 nanosheets: from electrode-limited to bulk-limited behavior.

Vertically stacked metal-semiconductor-metal heterostructures, based on liquid-processed nanomaterials, hold great potential for various printed electronic applications. Here we describe the fabrication of such devices by spray-coating semiconducting tungsten disulfide (WS2) nanosheets onto indium tin oxide (ITO) bottom electrodes, followed by spraying single-walled carbon nanotubes (SWNTs) as the top electrode. Depending on the formulation of the SWNTs ink, we could fabricate either Ohmic or Schottky contacts at the WS2/SWNTs interface. Using isopropanol-dispersed SWNTs led to Ohmic contacts and bulk-limited devices, characterized by out-of-plane conductivities of ∼10-4 S m-1. However, when aqueous SWNTs inks were used, rectification was observed, due to the formation of a doping-induced Schottky barrier at the WS2/SWNTs interface. For thin WS2 layers, such devices were characterized by a barrier height of ∼0.56 eV. However, increasing the WS2 film thickness led to increased series resistance, leading to a change-over from electrode-limited to bulk-limited behavior at a transition thickness of ∼2.6 µm. This work demonstrates that Ohmic/Schottky behavior is tunable and lays the foundation for fabricating large-area 2D nanosheet-based solution-deposited devices and stacks.

Influence of the properties of different graphene-based nanomaterials dispersed in polycaprolactone membranes on astrocytic differentiation.

Composites of polymer and graphene-based nanomaterials (GBNs) combine easy processing onto porous 3D membrane geometries due to the polymer and cellular differentiation stimuli due to GBNs fillers. Aiming to step forward to the clinical application of polymer/GBNs composites, this study performs a systematic and detailed comparative analysis of the influence of the properties of four different GBNs: (i) graphene oxide obtained from graphite chemically processes (GO); (ii) reduced graphene oxide (rGO); (iii) multilayered graphene produced by mechanical exfoliation method (Gmec); and (iv) low-oxidized graphene via anodic exfoliation (Ganodic); dispersed in polycaprolactone (PCL) porous membranes to induce astrocytic differentiation. PCL/GBN flat membranes were fabricated by phase inversion technique and broadly characterized in morphology and topography, chemical structure, hydrophilicity, protein adsorption, and electrical properties. Cellular assays with rat C6 glioma cells, as model for cell-specific astrocytes, were performed. Remarkably, low GBN loading (0.67 wt%) caused an important difference in the response of the C6 differentiation among PCL/GBN membranes. PCL/rGO and PCL/GO membranes presented the highest biomolecule markers for astrocyte differentiation. Our results pointed to the chemical structural defects in rGO and GO nanomaterials and the protein adsorption mechanisms as the most plausible cause conferring distinctive properties to PCL/GBN membranes for the promotion of astrocytic differentiation. Overall, our systematic comparative study provides generalizable conclusions and new evidences to discern the role of GBNs features for future research on 3D PCL/graphene composite hollow fiber membranes for in vitro neural models.

A Simple and Expeditious Route to Phosphate-Functionalized, Water-Processable Graphene for Capacitive Energy Storage.

Phosphate-functionalized carbon-based nanomaterials have attracted significant attention in recent years owing to their outstanding behavior in electrochemical energy-storage devices. In this work, we report a simple approach to obtain phosphate-functionalized graphene (PFG) via anodic exfoliation of graphite at room temperature with a high yield. The graphene nanosheets were obtained via anodic exfoliation of graphite foil using aqueous solutions of H3PO4 or Na3PO4 in the dual role of phosphate sources and electrolytes, and the underlying exfoliation/functionalization mechanisms are proposed. The effect of electrolyte concentration was studied, as low concentrations do not lead to a favorable graphite exfoliation and high concentrations produce fast graphite expansion but poor layer-by-layer delamination. The optimal concentrations are 0.25 M H3PO4 and 0.05 M Na3PO4, which also exhibited the highest phosphorus contents of 2.2 and 1.4 at. %, respectively. Furthermore, when PFG-acid at 0.25 M and PFG-salt at 0.05 M were tested as an electrode material for capacitive energy storage in a three-electrode cell, they achieved a competitive performance of ∼375 F/g (540 F/cm3) and 356 F/g (500 F/cm3), respectively. Finally, devices made up of symmetric electrode cells obtained using PFG-acid at 0.25 M possess energy and power densities up to 17.6 Wh·kg-1 (25.3 Wh·L-1) and 10,200 W/kg; meanwhile, PFG-salt at 0.05 M achieved values of 14.9 Wh·kg-1 (21.3 Wh·L-1) and 9400 W/kg, with 98 and 99% of capacitance retention after 10,000 cycles, respectively. The methodology proposed here also promotes a circular-synthesis process to successfully achieve a more sustainable and greener energy-storage device.

Comparative venomics and preclinical efficacy evaluation of a monospecific Hemachatus antivenom towards sub-Saharan Africa cobra venoms.

Cobras are the most medically important elapid snakes in Africa. The African genera Naja and Hemachatus include snakes with neurotoxic and cytotoxic venoms, with shared biochemical, toxinological and antigenic characteristics. We have studied the antigenic cross-reactivity of four sub-Saharan Africa cobra venoms against an experimental monospecific Hemachatus haemachatus antivenom through comparative proteomics, preclinical assessment of neutralization, and third generation antivenomics. The venoms of H. haemachatus, N. annulifera, N. mossambica and N. nigricollis share an overall qualitative family toxin composition but depart in their proportions of three-finger toxin (3FTxs) classes, phospholipases A2 (PLA2s), snake venom metalloproteinases (SVMPs), and cysteine-rich secretory proteins (CRISPs). A monospecific anti-Hemachatus antivenom produced by Costa Rican Instituto Clodomiro Picado neutralized the lethal activity of the homologous and heterologous neuro/cytotoxic (H. haemachatus) and cyto/cardiotoxic (N. mossambica and N. nigricollis) venoms of the three spitting cobras sampled, while it was ineffective against the lethal and toxic activities of the neurotoxic venom of the non-spitting snouted cobra N. annulifera. The ability of the anti-Hemachatus-ICP antivenom to neutralize toxic (dermonecrotic and anticoagulant) and enzymatic (PLA2) activities of spitting cobra venoms suggested a closer kinship of H. haemachatus and Naja subgenus Afrocobra spitting cobras than to Naja subgenus Uraeus neurotoxic taxa. These results were confirmed by third generation antivenomics. BIOLOGICAL SIGNIFICANCE: African Naja species represent the most widespread medically important elapid snakes across Africa. To gain deeper insight into the spectrum of medically relevant toxins, we compared the proteome of three spitting cobras (Hemachatus haemachatus, Naja mossambica and N. nigricollis) and one non-spitting cobra (N. annulifera). Three finger toxins and phospholipases A2 are the two major protein families among the venoms analyzed. The development of antivenoms of broad species coverage is an urgent need in sub-Saharan Africa. An equine antivenom raised against H. haemachatus venom showed cross-reactivity with the venoms of H. haemachatus, N. mossambica and N. nigricollis, while having poor recognition of the venom of N. annulifera. This immunological information provides clues for the design of optimum venom mixtures for the preparation of broad spectrum antivenoms.

Boosting the Performance of Graphene Cathodes in Na-O2 Batteries by Exploiting the Multifunctional Character of Small Biomolecules.

Graphene aerogels derived from a biomolecule-assisted aqueous electrochemical exfoliation route are explored as cathode materials in sodium-oxygen (Na-O2 ) batteries. To this end, the natural nucleotide adenosine monophosphate (AMP) is used in the multiple roles of exfoliating electrolyte, aqueous dispersant, and functionalizing agent to access high quality, electrocatalytically active graphene nanosheets in colloidal suspension (bioinks). The surface phenomena occurring on the electrochemically derived graphene cathode is thoroughly studied to understand and optimize its electrochemical performance, where a cooperative effect between the nitrogen atoms and phosphates from the AMP molecules is demonstrated. Moreover, the role of the nitrogen atoms in the adenine nucleobase of AMP and short-chain phosphate is unraveled. Significantly, the use of such cathodes with a proper amount of AMP molecules adsorbed on the graphene nanosheets delivers a discharge capacity as high as 9.6 mAh cm-2 and performs almost 100 cycles with a considerably reduced cell overpotential and a coulombic efficiency of ≈97% at high current density (0.2 mA cm-2 ). This study opens a path toward the development of environmentally friendly air cathodes by the use of natural nucleotides which offers a great opportunity to explore and manufacture bioinspired cathodes for metal-oxygen batteries.

High Performance Na-O2 Batteries and Printed Microsupercapacitors Based on Water-Processable, Biomolecule-Assisted Anodic Graphene.

Integrated approaches that expedite the production and processing of graphene into useful structures and devices, particularly through simple and environmentally friendly strategies, are highly desirable in the efforts to implement this two-dimensional material in state-of-the-art electrochemical energy storage technologies. Here, we introduce natural nucleotides (e.g., adenosine monophosphate) as bifunctional agents for the electrochemical exfoliation and dispersion of graphene nanosheets in water. Acting both as exfoliating electrolytes and colloidal stabilizers, these biomolecules facilitated access to aqueous graphene bio-inks that could be readily processed into aerogels and inkjet-printed interdigitated patterns. Na-O2 batteries assembled with the graphene-derived aerogels as the cathode and a glyme-based electrolyte exhibited a full discharge capacity of ∼3.8 mAh cm-2 at a current density of 0.2 mA cm-2. Moreover, shallow cycling experiments (0.5 mAh cm-2) boasted a capacity retention of 94% after 50 cycles, which outperformed the cycle life of prior graphene-based cathodes for this type of battery. The positive effect of the nucleotide-adsorbed nanosheets on the battery performance is discussed and related to the presence of the phosphate group in these biomolecules. Microsupercapacitors made from the interdigitated graphene patterns as the electrodes also displayed a competitive performance, affording areal and volumetric energy densities of 0.03 µWh cm-2 and 1.2 mWh cm-3 at power densities of 0.003 mW cm-2 and 0.1 W cm-3, respectively. Taken together, by offering a green and straightforward route to different types of functional graphene-based materials, the present results are expected to ease the development of novel energy storage technologies that exploit the attractions of graphene.

Aqueous Cathodic Exfoliation Strategy toward Solution-Processable and Phase-Preserved MoS2 Nanosheets for Energy Storage and Catalytic Applications.

The production of MoS2 nanosheets by electrochemical exfoliation routes holds great promise as a means to access this two-dimensional material in large quantities for different practical applications. However, the use of electrolytes based on synthetic organic salts and solvents, as well as issues related to the unwanted oxidation and/or phase transformation of the exfoliated nanosheets, constitute significant obstacles that hinder the industrial adoption of the electrochemical approach. Here, we introduce a safe and sustainable method for the cathodic delamination of MoS2 that makes use of aqueous solutions of very simple and widely available salts, mainly KCl, as the electrolyte. Combined with an appropriate biomolecule-based solvent transfer protocol, such an electrolytic exfoliation route is shown to afford colloidally dispersed, oxide-free, and phase-preserved MoS2 nanosheets of high structural quality in considerable yields. The mechanisms behind the efficient aqueous delamination of the bulk MoS2 cathode are also discussed and rationalized on the basis of the penetration of hydrated cations from the electrolyte between its layers and the immediate reduction of the accompanying water molecules. An asymmetric supercapacitor assembled with a cathodic MoS2 nanosheet-single walled carbon nanotube hybrid as the positive electrode and activated carbon as the negative electrode delivered energy densities (e.g., 26 W h kg-1 at 750 W kg-1 in 6 M KOH) that were competitive with those of other MoS2-based asymmetric devices. When used as a catalyst for the reduction of nitroarenes, the present cathodically exfoliated nanosheets exhibited one of the highest activities reported so far with MoS2 nanostructures, the origin of which is accounted for as well. Overall, by facilitating access to this two-dimensional material through a particularly simple, efficient, and cost-effective technique, these results should expedite the practical implementation of MoS2 nanosheets in energy storage, catalysis, and beyond.

Aqueous Exfoliation of Transition Metal Dichalcogenides Assisted by DNA/RNA Nucleotides: Catalytically Active and Biocompatible Nanosheets Stabilized by Acid-Base Interactions.

The exfoliation and colloidal stabilization of layered transition metal dichalcogenides (TMDs) in an aqueous medium using functional biomolecules as dispersing agents have a number of potential benefits toward the production and practical use of the corresponding two-dimensional materials, but such a strategy has so far remained underexplored. Here, we report that DNA and RNA nucleotides are highly efficient dispersants in the preparation of stable aqueous suspensions of MoS2 and other TMD nanosheets at significant concentrations (up to 5-10 mg mL-1). Unlike the case of common surfactants, for which adsorption on 2D materials is generally based on weak dispersive forces, the exceptional colloidal stability of the TMD flakes was shown to rely on the presence of relatively strong, specific interactions of Lewis acid-base type between the DNA/RNA nucleotide molecules and the flakes. Moreover, the nucleotide-stabilized MoS2 nanosheets were shown to be efficient catalysts in the reduction of nitroarenes (4-nitrophenol and 4-nitroaniline), thus constituting an attractive alternative to the use of expensive heterogeneous catalysts based on noble metals, and exhibited an electrocatalytic activity toward the hydrogen evolution reaction that was not impaired by the possible presence of nucleotide molecules adsorbed on their active sites. The biocompatibility of these materials was also demonstrated on the basis of cell proliferation and viability assays. Overall, the present work opens new vistas on the colloidal stabilization of 2D materials based on specific interactions that could be useful toward different practical applications.

Impact of Covalent Functionalization on the Aqueous Processability, Catalytic Activity, and Biocompatibility of Chemically Exfoliated MoS2 Nanosheets.

Chemically exfoliated MoS2 (ce-MoS2) has emerged in recent years as an attractive two-dimensional material for use in relevant technological applications, but fully exploiting its potential and versatility will most probably require the deployment of appropriate chemical modification strategies. Here, we demonstrate that extensive covalent functionalization of ce-MoS2 nanosheets with acetic acid groups (∼0.4 groups grafted per MoS2 unit) based on the organoiodide chemistry brings a number of benefits in terms of their processability and functionality. Specifically, the acetic acid-functionalized nanosheets were furnished with long-term (>6 months) colloidal stability in aqueous medium at relatively high concentrations, exhibited a markedly improved temporal retention of catalytic activity toward the reduction of nitroarenes, and could be more effectively coupled with silver nanoparticles to form hybrid nanostructures. Furthermore, in vitro cell proliferation tests carried out with murine fibroblasts suggested that the chemical derivatization had a positive effect on the biocompatibility of ce-MoS2. A hydrothermal annealing procedure was also implemented to promote the structural conversion of the functionalized nanosheets from the 1T phase that was induced during the chemical exfoliation step to the original 2H phase of the starting bulk material, while retaining at the same time the aqueous colloidal stability afforded by the presence of the acetic acid groups. Overall, by highlighting the benefits of this type of chemical derivatization, the present work should contribute to strengthen the position of ce-MoS2 as a two-dimensional material of significant practical utility.

Chemically exfoliated MoS2 nanosheets as an efficient catalyst for reduction reactions in the aqueous phase.

Chemically exfoliated MoS2 (ce-MoS2) nanosheets that incorporate a large fraction of metallic 1T phase have been recently shown to possess a high electrocatalytic activity in the hydrogen evolution reaction, but the potential of this two-dimensional material as a catalyst has otherwise remained mostly uncharted. Here, we demonstrate that ce-MoS2 nanosheets are efficient catalysts for a number of model reduction reactions (namely, those of 4-nitrophenol, 4-nitroaniline, methyl orange, and [Fe(CN)6](3-)) carried out in aqueous medium using NaBH4 as a reductant. The performance of the nanosheets in these reactions is found to be comparable to that of many noble metal-based catalysts. The possible reaction pathways involving ce-MoS2 as a catalyst are also discussed and investigated. Overall, the present results expand the scope of this two-dimensional material as a competitive, inexpensive, and earth-abundant catalyst.