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1. Evidence for late winter biogeochemical connectivity in permafrost soils

   https://doi.org/10.1038/s43247-023-00740-6  

   Hirst, Catherine; Monhonval, Arthur; Mauclet, Elisabeth; Thomas, Maxime; Villani, Maëlle; Ledman, Justin; Schuur, Edward_A G; Opfergelt, Sophie (December 2023, Communications Earth & Environment)

   Abstract The permafrost active layer is a key supplier of soil organic carbon and mineral nutrients to Arctic rivers. In the active layer, sites of soil-water exchange are locations for organic carbon and nutrient mobilization. Previously these sites were considered as connected during summer months and isolated during winter months. Whether soil pore waters in active layer soils are connected during shoulder seasons is poorly understood. In this study, exceptionally heavy silicon isotope compositions in soil pore waters show that during late winter, there is no connection between isolated pockets of soil pore water in soils with a shallow active layer. However, lighter silicon isotope compositions in soil pore waters reveal that soils are biogeochemically connected for longer than previously considered in soils with a deeper active layer. We show that an additional 21% of the 0–1 m soil organic carbon stock is exposed to soil - water exchange. This marks a hot moment during a dormant season, and an engine for organic carbon transport from active layer soils. Our findings mark the starting point to locate earlier pathways for biogeochemical connectivity, which need to be urgently monitored to quantify the seasonal flux of organic carbon released from permafrost soils. 

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2. Liquid-phase bottom-up synthesis of graphene nanoribbons

   https://doi.org/10.1039/c9qm00519f  

   Yoon, Ki-Young; Dong, Guangbin (January 2020, Materials Chemistry Frontiers)

   null (Ed.)

   Graphene nanoribbons (GNRs) – an emerging family of carbon-based semiconductors – can be precisely synthesised from small molecules such as benzene derivatives through bottom-up approaches. This review outlines a summary of the development of bottom-up synthesis of GNRs in liquid phase. The strategies are classified based on edge structures and widths of the materials, which are the crucial factors for properties of GNRs. In addition, views on challenges in the field and the future outlook are also provided. 

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3. Crystal engineering of alkylethynyl fluoroanthradithiophenes

   https://doi.org/10.1039/D1ME00158B  

   Thorley, Karl J.; Dremann, Derek; Iqbal, Hamna F.; Parkin, Sean R.; Jurchescu, Oana D.; Anthony, John E. (January 2022, Molecular Systems Design & Engineering)

   Fluoroanthradithiophenes are well known organic semiconductors, where alkynyl substituents featuring silicon and germanium exhibit hole mobilities in excess of 5 cm 2 V −1 s −1 . A key feature to achieve these performance levels is the 2-dimensional brickwork packing of triethylsilyl and triethylgermyl side chains, which direct solid-state packing, increase molecular stability, and increase solution processability for cheap and large scale fabrication. We have recently reported side chains utilising carbon in place of the other group 14 atoms, resulting in less favourable 1-dimensional molecular packing. Here we present the synthesis of new derivatives which adopt 2-D brickwork packing without the use of silicon or germanium to determine substituent effects on charge carrier mobility. 

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4. Metal‐Free Allylic C−H Amination of Vinylsilanes and Vinylboronates using Silicon or Boron as a Regioselectivity Switch

   https://doi.org/10.1002/anie.202210109  

   Maloney, T. Parker; Berman, Janna L.; Michael, Forrest E. (October 2022, Angewandte Chemie International Edition)

   Abstract Vinylsilanes and vinylboronates are common building blocks for organic synthesis, but direct functionalization of these species without the participation of either the C=C or C−Si/B bonds is rare. Herein, we report a metal‐free allylic C−H amination reaction of these vinylmetalloid species that installs a new C−N bond without competing transmetallation or alkene addition. In this transformation, the silicon or boron substituent inverts the usual regioselectivity, directing amination to the site distal to that group. Subsequent cross‐coupling or demetallation allows access to complementary regioisomeric products. Density Functional Theory computations revealed that the observed regioselectivity is due to a subtle combination of electronic and counterintuitive steric factors that favor initial attack of selenium at the silicon‐bearing carbon atom. 

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5. Effect of Humidity on Friction and Wear—A Critical Review

   https://doi.org/10.3390/lubricants6030074  

   Chen, Zhe; He, Xin; Xiao, Chen; Kim, Seong (September 2018, Lubricants)

   The friction and wear behavior of materials are not intrinsic properties, but extrinsic properties; in other words, they can drastically vary depending on test and environmental conditions. In ambient air, humidity is one such extrinsic parameter. This paper reviews the effects of humidity on macro- and nano-scale friction and wear of various types of materials. The materials included in this review are graphite and graphene, diamond-like carbon (DLC) films, ultrananocrystalline diamond (UNCD), transition metal dichalcogenides (TMDs), hexagonal boron nitride (h-BN), boric acid, silicon, silicon oxide, silicates, advanced ceramics, and metals. Details of underlying mechanisms governing friction and wear behaviors vary depending on materials and humidity; nonetheless, a comparison of various material cases revealed an overarching trend. Tribochemical reactions between the tribo-materials and the adsorbed water molecules play significant roles; such reactions can occur at defect sites in the case of two-dimensionally layered materials and carbon-based materials, or even on low energy surfaces in the case of metals and oxide materials. It is extremely important to consider the effects of adsorbed water layer thickness and structure for a full understanding of tribological properties of materials in ambient air. 

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