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General synthesis of two-dimensional van der Waals heterostructure arrays 期刊论文
NATURE, 2020: 368-+
作者:  Bloch, Joel S.;  Pesciullesi, Giorgio;  Boilevin, Jeremy;  Nosol, Kamil;  Irobalieva, Rossitza N.;  Darbre, Tamis;  Aebi, Markus;  Kossiakoff, Anthony A.;  Reymond, Jean-Louis;  Locher, Kaspar P.
收藏  |  浏览/下载:63/0  |  提交时间:2020/07/03

Two-dimensional van der Waals heterostructures (vdWHs) have attracted considerable interest(1-4). However, most vdWHs reported so far are created by an arduous micromechanical exfoliation and manual restacking process(5), which-although versatile for proof-of-concept demonstrations(6-16) and fundamental studies(17-30)-is clearly not scalable for practical technologies. Here we report a general synthetic strategy for two-dimensional vdWH arrays between metallic transition-metal dichalcogenides (m-TMDs) and semiconducting TMDs (s-TMDs). By selectively patterning nucleation sites on monolayer or bilayer s-TMDs, we precisely control the nucleation and growth of diverse m-TMDs with designable periodic arrangements and tunable lateral dimensions at the predesignated spatial locations, producing a series of vdWH arrays, including VSe2/WSe2, NiTe2/WSe2, CoTe2/WSe2, NbTe2/WSe2, VS2/WSe2, VSe2/MoS2 and VSe2/WS2. Systematic scanning transmission electron microscopy studies reveal nearly ideal vdW interfaces with widely tunable moire superlattices. With the atomically clean vdW interface, we further show that the m-TMDs function as highly reliable synthetic vdW contacts for the underlying WSe2 with excellent device performance and yield, delivering a high ON-current density of up to 900 microamperes per micrometre in bilayer WSe2 transistors. This general synthesis of diverse two-dimensional vdWH arrays provides a versatile material platform for exploring exotic physics and promises a scalable pathway to high-performance devices.


A general strategy for the synthesis of two-dimensional van der Waals heterostructure arrays is used to produce high-performance electronic devices, showing the potential of this scalable approach for practical technologies.


  
Synthesis of rare sugar isomers through site-selective epimerization 期刊论文
NATURE, 2020: 403-+
作者:  Jackson, Hartland W.;  Fischer, Jana R.;  Zanotelli, Vito R. T.;  Ali, H. Raza;  Mechera, Robert;  Soysal, Savas D.;  Moch, Holger;  Muenst, Simone;  Varga, Zsuzsanna;  Weber, Walter P.;  Bodenmiller, Bernd
收藏  |  浏览/下载:15/0  |  提交时间:2020/07/03

Glycans have diverse physiological functions, ranging from energy storage and structural integrity to cell signalling and the regulation of intracellular processes(1). Although biomass-derived carbohydrates (such as d-glucose, d-xylose and d-galactose) are extracted on commercial scales, and serve as renewable chemical feedstocks and building blocks(2,3), there are hundreds of distinct monosaccharides that typically cannot be isolated from their natural sources and must instead be prepared through multistep chemical or enzymatic syntheses(4,5). These '  rare'  sugars feature prominently in bioactive natural products and pharmaceuticals, including antiviral, antibacterial, anticancer and cardiac drugs(6,7). Here we report the preparation of rare sugar isomers directly from biomass carbohydrates through site-selective epimerization reactions. Mechanistic studies establish that these reactions proceed under kinetic control, through sequential steps of hydrogen-atom abstraction and hydrogen-atom donation mediated by two distinct catalysts. This synthetic strategy provides concise and potentially extensive access to this valuable class of natural compounds.


Various rare sugars that cannot be isolated from natural sources are synthesized using light-driven epimerization, a process which may find application in other synthetic scenarios.