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Enhancing photoluminescence (PL) in single-layer transition metal dichalcogenides has garnered significant interest, particularly for advancing high-performance 2D electronics and optoelectronics. The combination of surface engineering and contemporary growth methods has provided a platform for investigating optical signals. In this study, we present variations in PL and Raman signals of single-layer MoS2 flakes grown conformally using the glass-assisted CVD method on square-patterned surfaces with varying well depths. PL spectroscopy revealed a systematic and pronounced enhancement in intensities as the valley thickness decreased from 285 nm to 225 nm. Conversely, for the hill regions of the samples, the PL intensity initially increased with decreasing valley thickness and then decreased, despite the hill regions having a constant thickness of 300 nm. On the other hand, PL maps did not exhibit a systematic dependence of intensities on the hill-valley thickness distinction, contrary to expected results based on literature data for similar materials on flat surfaces. The origin of the intensity oscillations was attributed to possible mechanisms, including thickness-dependent interference and strain-related exciton funneling effects. Additionally, Raman measurements revealed irregular variations in intensity in hill regions, dependent on the thicknesses of the underlying SiO2 layers. Furthermore, we observed that the sizes of the flakes increased as the well depths of the underlying patterned surface decreased. This phenomenon might be attributed to alterations in the carrier gas flow pattern and varying temperature gradients between the hills and valleys. These results hold substantial potential to open new avenues for the integration of 2D transition metal dichalcogenides into on-chip electronic and optoelectronic devices.

Enhancing photoluminescence (PL) in single-layer transition metal dichalcogenides has garnered significant interest, particularly for advancing high-performance 2D electronics and optoelectronics. The combination of surface engineering and contemporary growth methods has provided a platform for investigating optical signals. In this study, we present variations in PL and Raman signals of single-layer MoS2 flakes grown conformally using the glass-assisted CVD method on squarepatterned surfaces with varying well depths. PL spectroscopy revealed a systematic and pronounced enhancement in intensities as the valley thickness decreased from 285 nm to 225 nm. Conversely, for the hill regions of the samples, the PL intensity initially increased with decreasing valley thickness and then decreased, despite the hill regions having a constant thickness of 300 nm. On the other hand, PL maps did not exhibit a systematic dependence of intensities on the hill-valley thickness distinction, contrary to expected results based on literature data for similar materials on flat surfaces. The origin of the intensity oscillations was attributed to possible mechanisms, including thickness-dependent interference and strain-related exciton funneling effects. Additionally, Raman measurements revealed irregular variations in intensity in hill regions, dependent on the thicknesses of the underlying SiO2 layers. Furthermore, we observed that the sizes of the flakes increased as the well depths of the underlying patterned surface decreased. This phenomenon might be attributed to alterations in the carrier gas flow pattern and varying temperature gradients between the hills and valleys. These results hold substantial potential to open new avenues for the integration of 2D transition metal dichalcogenides into onchip electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides are studied due to the possibility of creating nanoscale semiconductor devices, as well as fundamental issues of magnetic ordering. We researched the crystal structure and magnetic properties of niobium dichalcogenide Mn0.30NbS2. The results of the X-ray study showed the possible existence of an intermediate 23a0·23a0 structure between the “basic” superstructures. Also, two local maximums were found in the temperature dependence of the dynamic magnetic susceptibility. These features can indirectly confirm the presence of a transition superstructure and reflect the two-step nature of the magnetic ordering.

For the first time, an 93Nb NMR study of dichalcogenides CrxNbSe2 (x = 0.33, 0.5) in the paramagnetic state was performed. Analysis of the 93Nb NMR spectra revealed the presence in CrxNbSe2 of three magnetically nonequivalent niobium positions, whose immediate environment contains 0, 1, and 2 chromium ions, respectively. For each Nb position with a different number of chromium atoms in the immediate environment in CrxNbSe2 (x = 0.33, 0.5), the values of the components of the magnetic shift and electric field gradient tensors at the position of the niobium nuclei were determined. Evidence was obtained of the formation in Cr0.33NbSe2 of the ordering of chromium ion positions in the ab plane into a a0 × a0 superstructure. On the other hand, in Cr0.5NbSe2, no obvious indications of the formation of any superstructure of chromium ion positions were found. It has been established that the overlap of the 4d and 5s shells of niobium ions and the 3d orbitals of chromium leads to the appearance of a positive hyperfine field induced by the magnetic moments of chromium on Nb nuclei. From the temperature dependences of the shift and susceptibility in Cr0.5NbSe2, an estimate of these induced hyperfine fields is made. [ABSTRACT FROM AUTHOR]

The reactivity between bis(pyridin‐2‐yl)diselane oPy2Se2 and ditellane oPy2Te2 (L1 and L2, respectively; oPy=pyridyn‐2‐yl) and I2/Br2 is discussed. Single‐crystal structure analysis revealed that the reaction of L1 with I2 yielded [(HL1+)(I−)⋅5/2I2]∞ (1) in which monoprotonated cations HL1+ template a self‐assembled infinite pseudo‐cubic polyiodide 3D‐network, while the reaction with Br2 yielded the dibromide HoPySeIIBr2 (2). The oxidation of L2 with I2 and Br2 yielded the compounds HoPyTeIII2 (3) and HoPyTeIVBr4 (6), respectively, whose structures were elucidated by X‐ray diffraction analysis. FT‐Raman spectroscopy measurements are consistent with a 3c–4e description of all the X−Ch−X three‐body systems (Ch=Se, Te; X=Br, I) in compounds 2, 3, HoPyTeIIBr2 (5), and 6. The structural and spectroscopic observations are supported by extensive theoretical calculations carried out at the DFT level that were employed to study the electronic structure of the investigated compounds, the thermodynamic aspects of their formation, and the role of noncovalent σ‐hole halogen and chalcogen bonds in the X⋅⋅⋅X, X⋅⋅⋅Ch and Ch⋅⋅⋅Ch interactions evidenced structurally. [ABSTRACT FROM AUTHOR]

First‐principles calculations were carried out on the ZrSe2 compound, which has been of interest owing to its technologically important physical properties. The structural, electronic and optical properties of this compound were investigated under pressure through the plane wave pseudopotential approach within the framework of density functional theory. A comparison between the computed crystal structure parameters and the corresponding experimental counterparts shows a very good agreement between them. Fitting the pressure–volume data using the third‐order Birch–Murnaghan equation of state yielded a bulk modulus B0 = 38.17 GPa and a pressure derivative of bulk modulus = 8.2 for hexagonal ZrSe2. The relationship between the band structure and pressure is revealed. We calculated the total density of state (TDOS) under different pressures and partial density of state (PDOS) from 0 to 10 GPa. According to our calculations, metallization of hexagonal ZrSe2 is predicted to occur at around 10 GPa and pressure‐induced band‐gap engineering reveals the transformation of the indirect to direct band gap with increasing pressure. Furthermore, optical properties, such as the complex dielectric function, refractive index and reflectivity spectra of this compound, were studied for incident electromagnetic waves in an energy range up to 45 eV. The contributions to various transition peaks in the optical spectra are analyzed and discussed with the help of the energy‐dependent imaginary part of the dielectric function. [ABSTRACT FROM AUTHOR]

First‐principles calculations were carried out on the ZrSe2 compound, which has been of interest owing to its technologically important physical properties. The structural, electronic and optical properties of this compound were investigated under pressure through the plane wave pseudopotential approach within the framework of density functional theory. A comparison between the computed crystal structure parameters and the corresponding experimental counterparts shows a very good agreement between them. Fitting the pressure–volume data using the third‐order Birch–Murnaghan equation of state yielded a bulk modulus B0 = 38.17 GPa and a pressure derivative of bulk modulus = 8.2 for hexagonal ZrSe2. The relationship between the band structure and pressure is revealed. We calculated the total density of state (TDOS) under different pressures and partial density of state (PDOS) from 0 to 10 GPa. According to our calculations, metallization of hexagonal ZrSe2 is predicted to occur at around 10 GPa and pressure‐induced band‐gap engineering reveals the transformation of the indirect to direct band gap with increasing pressure. Furthermore, optical properties, such as the complex dielectric function, refractive index and reflectivity spectra of this compound, were studied for incident electromagnetic waves in an energy range up to 45 eV. The contributions to various transition peaks in the optical spectra are analyzed and discussed with the help of the energy‐dependent imaginary part of the dielectric function. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides are studied due to the possibility of creating nanoscale semiconductor devices, as well as fundamental issues of magnetic ordering. We researched the crystal structure and magnetic properties of niobium dichalcogenide Mn0.30NbS2. The results of the X-ray study showed the possible existence of an intermediate 2 3 a0·2 3 a0 structure between the "basic" superstructures. Also, two local maximums were found in the temperature dependence of the dynamic magnetic susceptibility. These features can indirectly confirm the presence of a transition superstructure and reflect the two-step nature of the magnetic ordering. [ABSTRACT FROM AUTHOR]

The first regioselective syntheses of 1,2-thiaselenane-4-amine (TSA4) and 1,2-thiaselenane-5-amine (TSA5) are developed. Both are redox motifs with high value in chemical biology that until now were hindered by tedious synthesis. An aziridine intermediate and a kinetically controlled S-acylation were leveraged for regioselective chalcogen installations. Short, fast sequences were optimised with just one or two chromatographic steps that cheaply deliver these motifs on scale for high throughput inhibitor screening, and thus provide a robust methodology for assembling other selenenyl sulfides. [ABSTRACT FROM AUTHOR]

The addition reaction of interelement compounds with heteroatom–heteroatom single bonds to unsaturated bonds under photoirradiation is an important method for the efficient and atom-economical construction of carbon–heteroatom bonds. However, in practice, the desired addition reaction is sometimes unable to proceed as expected due to the low efficiency of the desired addition reactions or the preferential polymerization of unsaturated compounds. In this study, by combining an interelement compound with homologous heteroatom compounds as a catalyst, we succeeded in suppressing the polymerization of the unsaturated compounds and in attaining a highly selective carbon–heteroatom bond formation through the desired addition reaction. In this paper, we have examined in detail whether such a "catalytic radical reaction" proceeds for unsaturated compounds and found that the dithiolation of some unsaturated compounds (i.e., vinylic ethers, styrenes, and isocyanides) could proceed with the assistance of (PhSe)2 under light. The developed methods in this study are expected to have strong implications in the fields of radical chemistry, heteroatom chemistry, synthetic organic chemistry, and catalyst chemistry as atom-economical methods for carbon–heteroatom bond formation. [ABSTRACT FROM AUTHOR]

We present a simple, fast, solvent-free, environmentally benign, one-pot technique to synthesize nanoflakes/nanoplatelets of transition metal dichalcogenides [i.e., molybdenum disulfide (MoS2), tungsten disulfide (WS2), and vanadium disulfide (VS2)]. In this technique, the precursor powder was prepared by simply mixing a transition metal source, a sulfur source, and multiwall carbon nanotubes (MWCNTs) in a mortar and pestle and heating in a microwave oven for 10 min under atmospheric conditions. MWCNTs were used as a microwave absorber. Microwaves interacted strongly with the precursor and induced localized arcing and plasma. Synthesized nanomaterials were studied using electron microscopy, X-ray and electron diffraction, Raman and photoelectron spectroscopy, and thermogravimetric analysis. The crystalline nanostructures were found to have mixed semiconducting and metallic phases. The as-synthesized MoS2, WS2, and VS2 showed impressive electrocatalytic activity for the hydrogen evolution reaction. MoS2 exhibited the lowest overpotential with a typical value of about 262 mV at a current density of 10 mA cm–2 and a Tafel slope of 84 mV dec–1, along with long-term stability. The proposed method is time- and energy-efficient and does not demand vacuum or a gaseous atmosphere, stringent temperature–pressure conditions, multiple steps or lengthy procedures, complex instrumentations, or expert manpower. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2) is the one which belong to the transition metal dichalcogenide system with analogue structure and was attracted to the world because of its use in a series of applications such as energy conversion, energy storage, environmental restoration and building strong sensors. The functional properties of MoS2 and graphene include high load transport, strong wear resistance, high mechanical strength and better friction. However, in comparison with graphene, MoS2's low cost, abundance, adjustable morphology and a tunable band gap are of advantage. In this analysis we concentrated mainly on recent changes to nanostructured MoS2 materials for the specific energy and its applications. Special emphasis has been placed on their applications in colour sensitized solar cells, super-capacitors, Li-ion cell battery, production of hydrogen with several reactions, photocatalysis of organic degradation, chemical / biological sensors, and gas sensors. Also, energy and environmental applications are important for the development of nanostructured MoS2. [ABSTRACT FROM AUTHOR]

The results of theoretical modeling from the first principles of atomic structure and properties of promising low-dimensional structures from semiconductors, performed for the past five years at the Center of Nanoelectronics and Novel Materials of Belarusian state university of informatics and radioelectronics, are summarized. The discovered principal new properties of two-dimensional structures from dichalcogenides of refractory metals and semiconductor silicides, one-dimensional structures of silicon, А3В5 semiconductors and semiconductor metal oxides, and zero-dimensional structures of carbon - nanodiamonds - are presented.

An impact of positions of Te atoms substituting W atoms in two-dimensional WS2/WSe2 heterostructures on their electronic properties is investigated by theoretical simulation. The substitution of W by Te tends to reduce the energy band gap and can lead to metallic properties depending on the impurity position and concentration. [ABSTRACT FROM AUTHOR]

In the presence of Cs 2 CO 3 and I 2, the coupling reaction of dialkyl phosphites with dichalcogenides (S, Se and Te) proceeds efficiently and completes in several minutes under mild conditions, affording the corresponding chalcogenophosphates in moderate to good yields. This fast and transition metal-free procedure provides a general method for the preparation of chalcogenophosphates. [ABSTRACT FROM AUTHOR]

New nanocomposites based on transition metal dichalcogenides, MoWCoS and MoWCuS, were synthesized through one step hydrothermal method. X-ray diffraction (XRD) and energy dispersive X-ray (EDX) techniques as well as field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images confirmed the synthesis of nanocomposites. For investigation of hydrogen evolution reaction (HER) properties of new nanocomposites, linear sweep voltammetry (LSV) was applied for this purpose. According to the results of similar previous works, the prepared nanocomposites showed promising HER properties as low overpotential equal to 41.4 mV/dec for MoWCoS hybridized with reduced graphene (G) and a little higher one equal to 49 mV/dec for MoWCuS hybridized with reduced graphene. Based on obtained Tafel slopes 38 and 53 mV/dec for MoWCoS/G and MoWCuS/G, respectively, the “Heyrovsky-Volmer” mechanism was suggested for the new HER three component nanocatalysts as the first effort to this purpose. [ABSTRACT FROM AUTHOR]

Core level spectra, generated by monochromatic Al Kα x-rays for a commercial, powdered tungsten disulfide (WS2) specimen, have been recorded and presented. The x-ray photoelectron spectra of WS2 obtained include a survey scan, high-resolution spectra of W 4f, S 2p, S 2s, W 4d, W 4p, O 1s, W 4s, S LMM, and the valence band. Quantitative analysis has been achieved using a two-parameter Tougaard background and line shapes indicated for fitting; using these methods a surface composition of WS2 is found. [ABSTRACT FROM AUTHOR]

Two-dimensional semiconductors provide excellent electrostatic control that is critical for scaled nodes. However, due to their lower dimensionality, contact resistance can be a limiting factor for performance of devices based on these materials. In this letter, we examine the intrinsic limits to contact resistance in 2-D semiconductors based on their band structure. It is found that for large enough doping concentration, contact resistance as outlined in the International Technology Road-map for Semiconductors road-map for high performance transistors can indeed be achieved. [ABSTRACT FROM AUTHOR]

Understanding the catalytic mechanism of highly active two-dimensional electrocatalysts is crucial to their rational design. Herein, we reveal the element dependence of the reactivity of two-dimensional metal dichalcogenide sheets for electrocatalytic CO 2 reduction. We found that tin(IV) disulfide (SnS 2 ) and molybdenum(IV) disulfide (MoS 2 ) sheets exhibited Faradaic efficiencies of 63.3% and ∼0%, respectively, for formic acid. Scanning electrochemical cell microscopy and theoretical calculations were used to identify the catalytically active sites of SnS 2 as terraces and edges. Owing to the effective utilization of the entire surface area, SnS 2 can effectively accelerate catalytic reactions. This finding provides a direction for material research in two-dimensional electrocatalysts for energy-efficient chemical production from electrochemical CO 2 reduction, as well as for other energy devices.

Excitons in atomically thin semiconductors necessarily lie close to a surface, and therefore their properties are expected to be strongly influenced by the surrounding dielectric environment. However, systematic studies exploring this role are challenging, in part because the most readily accessible exciton parameterthe exciton's optical transition energyis largely unaffected by the surrounding medium. Here we show that the role of the dielectric environment is revealed through its systematic influence on the size of the exciton, which can be directly measured via the diamagnetic shift of the exciton transition in high magnetic fields. Using exfoliated WSe2 monolayers affixed to single-mode optical fibers, we tune the surrounding dielectric environment by encapsulating the flakes with different materials and perform polarized low-temperature magneto-absorption studies to 65 T. The systematic increase of the exciton's size with dielectric screening, and concurrent reduction in binding energy (also inferred from these measurements), is quantitatively compared with leading theoretical models. These results demonstrate how exciton properties can be tuned in future 2D optoelectronic devices. [ABSTRACT FROM AUTHOR]

Hexapod-like two dimensional transition metal dichalcogenide nickel diselenide (NiSe 2 ) structures was synthesized by a facile hydrothermal approach and investigated its electrochemical performance as a supercapacitor electrode for the first time. The obtained material was characterized by XRD, XPS and TEM analysis. The results confirmed the presence of orthorhombic phase of NiSe 2 in the synthesized hexapod-like NiSe 2 structures. The fabricated NiSe 2 electrode on graphite foil exhibited a specific capacitance of 75 F g −1 with good cyclic retention of 94% at a current density of 1 mA cm −2 after 5000 charge-discharge cycles. Our results indicate that the synthesized hexapod-like NiSe 2 structures hold as a promising candidate for the supercapacitor applications. [ABSTRACT FROM AUTHOR]

With the lateral coplanar heterojunctions of two-dimensional monolayer materials turning into reality, the quantitative understanding of their electronic, electrostatic, doping, and scaling properties becomes imperative. In contrast to traditional bulk 3D junctions where carrier equilibrium is reached through local charge redistribution, a highly nonlocalized charge transfer (trailing off as 1/x away from the interface) is present in lateral 2D junctions, increasing the junction size considerably. The depletion width scales as p-1, while the differential capacitance varies very little with the doping level p. The properties of lateral 2D junctions are further quantified through numerical analysis of realistic materials, with graphene, MoS2, and their hybrid serving as examples. Careful analysis of the built-in potential profile shows strong reduction of Fermi level pinning, suggesting better control of the barrier in 2D metal-semiconductor junctions. [ABSTRACT FROM AUTHOR]

We report on specific heat and magnetotransport measurements performed on superconducting Cu 10 % TiSe 2 single crystals. We show that superconductivity persists in transport measurements up to magnetic fields H R well above the upper critical field H c 2 deduced from the calorimetric measurements. Surprisingly this “surface” superconductivity is present for all magnetic field orientations, either parallel or perpendicular to the layers. For H ‖ ab , the temperature dependence of the H R / H c 2 ratio can be well reproduced by solving the Ginzburg–Landau equations in presence of a surface layer with reduced superconducting properties. Unexpectedly this temperature dependence does not depend on the field orientation. [ABSTRACT FROM AUTHOR]

We report a systematic study of coherent spin precession and spin dephasing in electron-doped monolayer MoS2. Using time-resolved Kerr rotation spectroscopy and applied in-plane magnetic fields, a nanosecond time scale Larmor spin precession signal commensurate with g-factor |g0| ≃ 1.86 is observed in several different MoS2 samples grown by chemical vapor deposition. The dephasing rate of this oscillatory signal increases linearly with magnetic field, suggesting that the coherence arises from a subensemble of localized electron spins having an inhomogeneously broadened distribution of g-factors, g0 + Δg. In contrast to g0, Δg is sample-dependent and ranges from 0.042 to 0.115. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide is a layered transition-metal dichalcogenide semiconductor that is attracting renewed attention for its potential use in future nanoscale electronics, optoelectronics, catalysis, tribology, and other fields. In all of these cases, the interaction between MoS and various transition metals is very important. In this work we survey the thermodynamics of the metal-Mo-S systems and the anticipated reaction products from transition metals and MoS. We examined over 200 references on the reactions between transitions metals (M) and MoS, compiled thermodynamic data, and used the thermodynamic data to predict M-Mo-S ternary phase diagrams for systems without experimentally determined diagrams. Where possible, experimental literature on the interactions between metals and MoS was used to corroborate our predicted diagrams and stable reaction products. Both the previously reported and newly predicted M-Mo-S phase diagrams fall into three categories. In the first category, the metal is in thermodynamic equilibrium with MoS. In another, there is a driving force for the metal to reduce MoS, with tie lines to sulfides of the contact metal dominating the phase diagram. In a final category, there is a very stable solid solution or ternary phase that dominates the phase diagram. Better understanding of the phase equilibria in the M-Mo-S systems will aid research on the use of MoS in a variety of fields. [ABSTRACT FROM AUTHOR]

Full-band ballistic quantum transport calculations were used to study the screening effects in ultrashort-channel few-layer MoS2 transistors. A large density of states resulted in small screening lengths while inhibiting direct source-to-drain tunneling. Short-channel effects were observed even for the structurally confined 2-D transistors resulting in degraded electrostatic control. Electron confinement effects were also observed in the OFF-state in multilayered devices. [ABSTRACT FROM AUTHOR]

We report substantial improvements and modulation in the photocurrent (PC) and photoluminescence (PL) spectra of monolayer MoS recorded under electrostatic and ionic liquid gating conditions. The photocurrent and photoluminescence spectra show good agreement with a dominant peak at 1.85 eV. The magnitude of the photoluminescence can be increased 300% by ionic liquid gating due to the passivation of surface states and trapped charges that act as recombination centers. The photocurrent also doubles when passivated by the ionic liquid. Interestingly, a significant shift of the PL peak position is observed under electrostatic (14 meV) and ionic liquid (30 meV) gating, as a result of passivation. The ionic liquid provides significant screening without any externally applied voltage, indicating that these surface recombination centers have net charge. The acute sensitivity of monolayer MoS to ionic liquid gating and passivation arises because of its high surface-to-volume ratio, which makes it especially sensitive to trapped charge and surface states. These results reveal that, in order for efficient optoelectronic devices to be made from monolayer MoS, some passivation strategy must be employed to mitigate the issues associated with surface recombination. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Zirconium diselenide (ZrSe) is one of many members of the layer-structured transition-metal dichalcogenide family. The structure of these materials features a weakly bonded van der Waals gap between covalently bonded CdI-type atomic layers that may host a wide range of intercalants. Intercalation can profoundly affect the structural, thermal, and electronic properties of such materials. While the thermoelectric potential of layer-structured transition-metal dichalcogenides has been formerly studied by several groups, to our best knowledge, neither the thermoelectric properties of ZrSe nor the impact of intercalation on its thermoelectric properties have been reported (specifically, the full evaluation of the dimensionless figure of merit, ZT, which includes the thermal conductivity). In this proof-of-principle study, ZrSe single crystals have been synthesized using an iodine-assisted vapor transport method, followed by a wet-chemistry lithium intercalation process. The results of resistivity, thermopower, and thermal conductivity measurements between 10 K and 300 K show that Li intercalation induced additional charge carriers and structural disorder that favorably affected the thermoelectric properties of the material. As a result, a dimensionless figure of merit ZT ≈ 0.26 has been attained at room temperature in a Li-intercalated sample, representing nearly a factor of three improvement compared with the pristine sample. These improvements, along with the abundance, relatively low toxicity, and low cost of such materials, merit further thermoelectric investigations of intercalated zirconium diselenide, especially in conjunction with a substitutional doping approach. [ABSTRACT FROM AUTHOR]

A previously unreported compound, Ag0.79VS2, has been synthesized; its structure and elementary properties are reported. Ag0.79VS2 crystallizes in two forms, designated as the α and β, related to the 1s-InTaS2 structure. Single crystal x-ray diffraction shows the α form to have a single layer hexagonal structure with a unit cell of 3.213(3)Å×7.809(6)Å, consisting of layers of edge-shared VS6 triangular prisms separated by layers of Ag. The β form is similar but has an supercell in the basal plane, yielding a unit cell of 5.573(5)Å×7.822(6)Å. Both forms have disordered and displaced silver in the basal plane, but the β form has partial ordering of its silver sublattice and in-plane vanadium trimers. Resistivity measurements show metallic temperature dependence with an unusual hysteresis between 210K and 130K. Magnetic susceptibility measurements show Pauli Paramagnetic behavior. The Seebeck coefficient at 300K is 42µV/K. [ABSTRACT FROM AUTHOR]

Abstract: Vinylic selenides and tellurides are useful synthetic intermediates for preparation of vinylic compounds and carbonyl compounds. Herein we report highly selective perfluoroalkylselenation and -telluration of terminal alkynes by using heteroatom mixed systems, i.e., (PhSe)2/RfI and (PhTe)2/RfI, upon photoirradiation. When the reaction of aromatic alkynes and conjugated enynes with diphenyl diselenide and perfluoroalkyl iodide is conducted in benzotrifluoride (BTF) as solvent upon irradiation with a xenon lamp through Pyrex (hν >300 nm), novel perfluoroalkylselenation of the alkynes takes place regio- and stereoselectively to give 1-(perfluoroalkyl)-2-(phenylseleno)alkenes in good yields. Similar procedure can be applied to photoinduced perfluoroalkyltelluration of aromatic alkynes, and perfluoroalkyl and phenyltelluro groups are introduced to the terminal and internal positions of alkynes regio- and stereoselectively. Since perfluoroalkyl (fluorous) groups make it possible to isolate the products easily by fluorous/organic/aqueous extraction technique, the obtained perfluoroalkylselenation and -telluration products are promising as synthetic intermediates. [Copyright &y& Elsevier]

We report the first synthesis of magnetic one-dimensional transition metal dichalcogenides. Pure and Mn-doped tantalum disulfide nanotapes were synthesized using a catalyst-free single-step growth process. The sample yield of nanostructures was nearly 100 %. The nanotapes were composed of a number of smaller nanowires which appear to be open-ended nanotubes. The smaller nanowires have diameters ranging from about 30 to 300 nm. The Mn dopants were incorporated within intercalation sites between TaS layers. Interactions between these dopant ions induced low temperature magnetic phase transitions similar to those seen in macroscopic MnTaS compounds. The magnetic properties do not exactly correspond to their bulk counterparts, as exemplified by a higher than expected ferromagnetic transition temperature in 1D nanostructures. This indicates the magnetic properties are likely influenced by quantum size effects. The simplicity of this one-step synthesis method should allow for this technique to be extended to other dichalcogenide systems and/or magnetic dopants, opening up a new class of 1D magnetic nanostructures. [ABSTRACT FROM AUTHOR]

Molybdenum/tungsten dichalcogenides constitute a well-defined family of compounds which crystallize in a layer-type structure. These compounds have properties tailored for use as storage electrodes in rechargeable photoelectrochemical solar energy storage cells. These compounds find a wide range of applications in the field of catalysis and as lubricants at high temperatures and pressures. Among IV-VI semiconducting compounds, (Mo/W)Se2-layered compound dichalcogenides exhibit a hexagonal structure. The basic structural unit of such a compound is a sandwich of three planes: one plane of transition metal atoms between two halogen atoms. These sandwich-type structures are only loosely bound together through weak Van der Waals forces, and therefore, extremely anisotropic physical properties result. The material properties of the layered semiconductors, molybdenum diselenide (MoSe2), tungsten diselenide (WSe2) and molybdenum tungsten diselenide (MoxW1 - xSe2), are prepared by different methods and presented in this review. [ABSTRACT FROM AUTHOR]

Abstract: A method for creating a patterned array of sub-micron crystals on the surface of a doped layered dichalcogenide using a scanning electron microscope has been developed. Exposing the surface of copper doped TiSe2 to iodine vapor induces sub-micron CuI crystals to form upon the surface. The copper ions diffuse to the surface from within the crystal to react with the iodine vapor, with larger crystals forming at higher temperatures. The amount and size of the crystals formed in a given area could be controlled by first exposing of portions of the surface to electron radiation within the microscope. Increasing the radiation exposure results in the formation of fewer and smaller CuI crystallites, and it is possible to completely prevent their formation using large exposures. It appears that the electron beam creates a thin barrier that limits the diffusion of copper ions to the surface. The system is sufficiently inert that exposing the surface to air for a few hours has no significant effect. The resultant surface features can be arranged with a lateral resolution limited mainly by the size of the features themselves. [ABSTRACT FROM AUTHOR]

Aberration-corrected high-resolution transmission electron microscopy (HRTEM) has been applied to resolve the atomic structure of a complex layered crystal, (PbS)1.14NbS2, which comprises a high density of incommensurate interfaces. The strong suppression of image delocalization and the favourable contrast transfer under negative Cs imaging (NCSI) conditions have been exploited for obtaining HRTEM images which directly reveal the projected crystal structure and allow to study lattice imperfections, like stacking disorder and layer undulations, with atomic scale resolution. The advantages of aberration-corrected HRTEM over conventional HRTEM are demonstrated by direct comparison of experimental images and computer simulations. [ABSTRACT FROM AUTHOR]

Abstract: A copper-catalyzed synthesis of β-haloalkenyl sulfides or selenides was carried out by addition of dichalcogenides and tetrabutylammonium halides to internal alkynes. The present reaction anti- and regio-selectively afforded the corresponding alkenyl chalocogenides, and took advantage of both organochalcogenide-groups on dichalcogenide. Furthermore, the reaction under oxygen atmosphere could employ thiols. The use of the procedure could easily synthesize (Z)-tamoxifen from diphenyl acetylene in three steps. [Copyright &y& Elsevier]

Quantifying the activity of key cellular redox players is crucial for understanding physiological homeostasis, and for targeting their perturbed states in pathologies including cancer and inflammatory diseases. However, cellularly-selective probes for oxidoreductase turnover are sorely lacking. We rationally developed the first probes that selectively target the mammalian selenoprotein thioredoxin reductase (TrxR), using a cyclic selenenylsulfide oriented to harness TrxR's unique selenolthiol chemistry while resisting the cellular monothiol background. Lead probe RX1 had excellent TrxR1-selective performance in cells, cross-validated by knockout, selenium starvation, knock-in, and chemical inhibitors. Its background-free fluorogenicity enabled us to perform the first quantitative high-throughput live cell screen for TrxR1 inhibitors, which indicated that tempered S N Ar electrophiles may be more selective TrxR drugs than the classical electrophiles used hitherto. The RX1 design thus sets the stage for in vivo imaging of the activity of this key oxidoreductase in health and disease, and can also drive TrxR1-inhibitor drug design., Competing Interests: DECLARATION OF INTERESTS L.Z., J.G.F., and O.T.-S. are inventors on patent application EP21167187.0 covering compound structures reported in this paper. The authors declare no competing financial interests.

Molybdenum disulphide (MoS 2) is a transition metal dichalcogenide most widely studied as a heterogeneous catalyst due to its outstanding structural and physicochemical properties. Today, 2D layered MoS 2 has gained much attention due to its variety of environmental remediation applications, production of cleaner fuels, and energy storage. MoS 2 is a structural analogue of graphene and has similar properties, like greater surface area, a good charge carrying capacity, and higher mechanical strength. Therefore, MoS 2 can be easily coupled with graphene to further enhancing its catalytic efficiencies. Moreover, MoS 2 is less costly, highly abundant, has better light absorption capacity and adjustable bandgap than graphene. Most of the recent advancements in structural and synthesis techniques for improving catalytic properties of MoS 2 for various applications like photodegradation of dyes and organic compounds, hydrogen production, dye-sensitized solar cells, electrochemical capacitors, hydrodesulfurization, chemical and biological sensors, and gas sensors are discussed in this paper. Future prospective and research topics for the development of MoS 2 based composites are also discussed. [Display omitted] • MoS 2 is a structural analogue of graphene. • Various applications of MoS 2 as a heterogeneous catalyst has been discussed. • MoS 2 /graphene shows excellent supercapacitor applications. • Recent developments in 2D MoS 2 heterogeneous catalyst are discussed. • Drawbacks and advantages of MoS 2 based co-catalysts are summarized. [ABSTRACT FROM AUTHOR]

• First ferrocene decorated tetrahedral Ag(I) core was described among phosphor-1,1 dithiolate stabilized silver(I) clusters. • Homoleptic polymeric and tetrahedral Ag(I) (ferrocenyl dithiophosphonate) complexes reported. • Two heterobimetallic Ag(I) ferrocenyl dithiophosphonates complexes were structurally characterized. • Cyclic voltammetry proves negligible electrostatic factor via a single wave for all peripheral ferrocene moieties. Silver(I) ferrocenyl dithiophosphonato [Ag{S 2 P(O i Pr)Fc}] n I , [Fc = Fe(η5-C 5 H 4)(η5-C 5 H 4)] 1D polymer was yielded via a ligand exchange reaction between silver nanocluster [Ag 21 (S 2 P(OiPr 2) 12)]PF 6 and monoanionic [S 2 P(O i Pr)Fc]¯ ligand. As per molecular stoichiometry of 1 , a direct reaction between [Ag(CH 3 CN) 4 ]PF 6 and [S 2 P(O i Pr)Fc]− was performed in methanol solvent and surprisingly, generate a tetrahedral Ag 4 {S 2 P(O i Pr)Fc} 4 2 cluster instead of 1. Both (1 and 2) clusters are the novel example of homoleptic Ag(I) complexes supported by ferrocenyl dithiophosphonates. Molecular structure of these clusters was unequivocally established by single crystal X-ray crystallographic analyses and supported by the ESI-MS, and 1H and 31P NMR spectroscopy. Structural elucidations reveal that compound 1 has subsequently Ag 2 S 2 square plane and Ag 2 S 4 P 2 twisted boat units to build a long chain 1D polymer. The cluster 2 exhibits with a tetrahedral Ag(I) core framed by four [S 2 P(O i Pr)Fc]− ligands. interstingly, the [S 2 P(O i Pr)Fc]− ligand display a trimetallic triconnective (η3; µ 1, µ 2) bonding pattern in both molecules. The electrochemical behaviours of both compounds (1 and 2) were studied by using cyclic voltammetry, which shows a single wave for all the peripheral ferrocenes and implies negligible electrostatic factor between all ferrocene moieties. [ABSTRACT FROM AUTHOR]