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Establishing the presence and state of organic matter, including its possible biosignatures, in martian materials has been an elusive quest, despite limited reports of the existence of organic matter on Mars. We report the in situ detection of organic matter preserved in lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, Gale crater, by the Sample Analysis at Mars instrument suite onboard the Curiosity rover. Diverse pyrolysis products, including thiophenic, aromatic, and aliphatic compounds released at high temperatures (500° to 820°C), were directly detected by evolved gas analysis. Thiophenes were also observed by gas chromatography–mass spectrometry. Their presence suggests that sulfurization aided organic matter preservation. At least 50 nanomoles of organic carbon persists, probably as macromolecules containing 5% carbon as organic sulfur molecules.

The catalyst microstructure significantly impacts the corresponding hydrodesulfurization (HDS) performance. In this study, the carbon sponge (CMF) derived from melamine foam was used as support to prepare a series of pre-sulfurized CoMoS/CMF catalysts with different Co/Mo molar ratios using hydrothermal synthesis. The characterization results from SEM, TEM, XRD, and N 2 physisorption revealed that all catalysts exhibit the three-dimensional porous (3DP) structure, where the metal sulfides with uneven ravines coated the CMF framework. The optimized Co 2.0 MoS/CMF catalyst achieved 99.2% thiophene conversion at 1 MPa and 360 °C during HDS test. The interconnected pores facilitated the reactant/product diffusion in the catalyst. Moreover, the highly dispersed MoS 2 provided abundant active sites, leading to enhanced HDS activity. This study demonstrates the promise of CMF support for developing pre-sulfurized catalysts with enhanced HDS activity. Graphical Abstract

Two-dimensional (2D) semiconducting monolayers such as transition metal dichalcogenides (TMDs) are promising channel materials to extend Moore’s Law in advanced electronics. Synthetic TMD layers from chemical vapor deposition (CVD) are scalable for fabrication but notorious for their high defect densities. Therefore, innovative endeavors on growth reaction to enhance their quality are urgently needed. Here, we report that the hydroxide W species, an extremely pure vapor phase metal precursor form, is very efficient for sulfurization, leading to about one order of magnitude lower defect density compared to those from conventional CVD methods. The field-effect transistor (FET) devices based on the proposed growth reach a peak electron mobility ~200 cm 2 /Vs (~800 cm 2 /Vs) at room temperature (15 K), comparable to those from exfoliated flakes. The FET device with a channel length of 100 nm displays a high on-state current of ~400 µA/µm, encouraging the industrialization of 2D materials. Chemical vapor deposition enables the scalable production of 2D semiconductors, but the grown materials are usually affected by high defect densities. Here, the authors report a hydroxide vapour phase deposition method to synthesize wafer-scale monolayer WS 2 with reduced defect density and electrical properties comparable to those of exfoliated flakes.

Investigations of two-dimensional transition-metal chalcogenides (TMCs) have recently revealed interesting physical phenomena, including the quantum spin Hall effect 1 , 2 , valley polarization 3 , 4 and two-dimensional superconductivity 5 , suggesting potential applications for functional devices 6 – 10 . However, of the numerous compounds available, only a handful, such as Mo- and W-based TMCs, have been synthesized, typically via sulfurization 11 – 15 , selenization 16 , 17 and tellurization 18 of metals and metal compounds. Many TMCs are difficult to produce because of the high melting points of their metal and metal oxide precursors. Molten-salt-assisted methods have been used to produce ceramic powders at relatively low temperature 19 and this approach 20 was recently employed to facilitate the growth of monolayer WS 2 and WSe 2 . Here we demonstrate that molten-salt-assisted chemical vapour deposition can be broadly applied for the synthesis of a wide variety of two-dimensional (atomically thin) TMCs. We synthesized 47 compounds, including 32 binary compounds (based on the transition metals Ti, Zr, Hf, V, Nb, Ta, Mo, W, Re, Pt, Pd and Fe), 13 alloys (including 11 ternary, one quaternary and one quinary), and two heterostructured compounds. We elaborate how the salt decreases the melting point of the reactants and facilitates the formation of intermediate products, increasing the overall reaction rate. Most of the synthesized materials in our library are useful, as supported by evidence of superconductivity in our monolayer NbSe 2 and MoTe 2 samples 21 , 22 and of high mobilities in MoS 2 and ReS 2 . Although the quality of some of the materials still requires development, our work opens up opportunities for studying the properties and potential application of a wide variety of two-dimensional TMCs. Molten-salt-assisted chemical vapour deposition is used to synthesize a wide variety of two-dimensional transition-metal chalcogenides.

Hydrodesulfurization (HDS) is an essential process in clean fuel oil production, however, the huge challenge is the synthesis of the catalyst with plentiful active sites. Here, we have shown the design of few-layered, ultrashort Ni-Mo-S slabs dispersed on reduced graphene oxide (Ni-Mo-S/rGO-A) based on anchoring [PMo 12 O 40 ] 3− clusters and Ni 2+ on polyethyleneimine (PEI)-modified graphite oxide. Structural characterizations (transmission electron microscopy (TEM), X-ray absorption fine structure (XAFS), etc.) show that Ni-Mo-S slabs with predominant monolayer and partial substitution of edge Mo atoms by isolated Ni atoms have rich accessible edge Ni-Mo-S sites and high sulfurization degree. All virtues endow it with plentiful edge-active sites, and consequently, the enhanced performance for hydrodesulfurization of dibenzothiophene (DBT). The hydrodesulfurization proceeds via a more-favorable direct desulfurization (DDS) route with a reaction rate constant ( k HDS ) of 48.6 × 10 −7 mol·g −1 ·s −1 over Ni-Mo-S/rGO-A catalyst, which is 4.3 times greater than that over traditional Ni-Mo-S/Al 2 O 3 catalyst and at the forefront of reported catalysts.

Selectivity is a major parameter of the ISOL process. In order to avoid overloading downstream processes, purity control should be implemented as early as possible in the process chain from target material to the beam user delivery point [1]. In this work we present a novel approach for the development and production of SnS radioactive ion beams using the photofission production mode. The successful developments of the sulfur delivery system at ISOLDE and SPES, in the frame work of the BEAMLAB task of the ENSAR2 program, have triggered the beam time request for molecular tin (SnS) beams at the ALTO facility.The on-line radioactive SnS beam has already taken place and SnS molecules are well formed and released from the UCx target volume. The major observation is the purification of the tin beams by sulfurization. We note the antimony, main isobaric contaminant of tin isotopes, was fully suppressed and we got very pure SnS beams. Radioactive exotic isotopes 133Sn and 134Sn have well identified and released. Technical developments of the target-ion source production setup and selected results of these online measurements will be presented. The overall reached molecular production efficiency was 75%.

Sulfurization with sulfur vapor has been demonstrated to be useful for fabricating sputtered-multilayer MoS2 films with an approximately 4-nm thickness. With this process, sulfur vacancies in the sputtered MoS2 films were remarkably compensated, and MoO3 was simultaneously sulfurized. Eventually, carrier densities of the sulfurized MoS2 films were successfully reduced to 1.8 × 1016 cm−3 and electron mobilities were considerably enhanced to 25.2 cm2/V-s.

Rational construction of hierarchical multi-component materials with abundant heterostructure is evolving as a promising strategy to achieve excellent metal-organic frameworks (MOFs) based electromagnetic wave (EMW) absorbers. Herein, hierarchical heterostructure WS 2 /CoS 2 @carbonized cotton fiber (CCF) was fabricated using the ZIF-67 MOFs nanosheets anchored cotton fiber (ZIF-67@CF) as a precursor through the tungsten etching, sulfurization, and carbonization process. Apart from the synergetic effect of dielectric-magnetic dual-loss mechanism, the hierarchical heterostructure and multicomponent of WS 2 /CoS 2 @CCF also display improved impedance matching. Furthermore, numerous W-S-Co bands and heterojunction interfaces of heterogeneous WS 2 /CoS 2 are beneficial to promoting additional interfacial/dipole polarization loss and conductive loss, thereby enhancing the EMW attenuation performance. Based on the percolation theory, a good balance between impedance matching and EMW absorption capacity was achieved for the WS 2 /CoS 2 @CCF/paraffin composite with 20 wt.% filler loading, exhibiting strong EMW absorption capability with a minimum reflection loss (RL min ) value of −51.26 dB at 17.36 GHz with 2 mm thickness and a maximum effective absorption bandwidth (EAB max ) as wide as 6.72 GHz. Our research will provide new guidance for designing high-efficient MOFs derived EMW absorbers.

Massive amounts of low-grade tin middlings have been produced from tin tailings, in which arsenic and tin are worthy to be recycled. Owing to high sulfur content in these tin middlings, a novel self-sulfurization roasting was proposed to transform, separate and recover arsenic and tin in this research. There was no extra curing agent to be added, which decreased the formation of pollutant S-containing gas. The self-sulfurization process involved a two-stage roasting of reduction followed by sulfurization. First in reduction roasting, FeAsS decomposed to FeS and As and the As then transformed to As 4 (g) and As 4 S 4 (g), via which the arsenic was separated and recovered. The arsenic content in the first residue could be decreased to 0.72 wt.%. Accompanied with it, the FeS was firstly oxidized to Fe 1− x S and then to SO 2 (g) by the coexisted Fe 2 O 3 , and finally reduced and combined with the independent Fe 2 O 3 to form Fe 1− x S. In the followed sulfurization roasting, the Fe 1− x S sulfurized SnO 2 to SnS(g), due to which tin could be recovered and its content in the second residue decreased to 0.01 wt.%. This study provided an efficient method to separate and recover arsenic and tin from low-grade tin middlings.

The ability to tailor and enhance photoluminescence (PL) behavior in two-dimensional (2D) transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS 2 ) is significant for pursuing optoelectronic applications. To achieve this, it has been essential to obtain high-quality single-layer MoS 2 and fully explore its intrinsic PL performance. Here, we fabricate single-layer MoS 2 by a thermal vapor sulfurization method in which a pre-deposited molybdenum trioxide (MoO 3 ) thin film is sulfurized over a short period (for several minutes) to turn into MoS 2 . These as-grown MoS 2 crystals show quite strong PL, which is about one order of magnitude higher than that of chemical-vapor-deposited MoS 2 . Temperature- and power-dependent spectroscopy measurements disclose the apparent influence of sulfur (S) vacancies on the PL behavior and the noticeable free-to-bound exciton recombinations in the luminescence process. The fact that PL intensity of the sample in vacuum sharply lowered down relative to in air reveals that the high PL is facilitated by molecular adsorption on S vacancies in air. And multi-channel decay processes coupled with S vacancies are revealed in the time-resolved PL spectroscopy. In our work, single-layer MoS 2 with high PL is synthesized and its defect-induced PL features are analyzed, which is of great importance for developing advanced nano-electronics and optoelectronics based on 2D structures.