《自然》一周（20230420）论文导读
2023/4/23 20:13:52 科学网

     编译 | 冯维维

     Nature, 20 April 2023，Volume 616 Issue 7957

     《自然》2023年4月20日，第616卷，7957期

    

     物理学Physics

     Successful kinetic impact into an asteroid for planetary defence

     成功动力撞击小行星以保护地球

     ▲ 作者：R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Nancy L. Chabot, Andrew S. Rivkin, Andrew F. Cheng, Elena Y. Adams, Harrison F. Agrusa, Elisabeth D. Abel, Amy L. Alford, Erik I. Asphaug, Justin A. Atchison, Andrew R. Badger, Paul Baki, Ronald-L. Ballouz, Dmitriy L. Bekker, Julie Bellerose, Shyam Bhaskaran, Bonnie J. Buratti, Saverio Cambioni, Michelle H. Chen, Steven R. Chesley, George Chiu, Gareth S. Collins, Yun Zhang

     ▲ 链接：

     https://www.nature.com/articles/s41586-023-05810-5

     ▲ 摘要：

     尽管科学家认为至少在下个世纪内并未有已知小行星会对地球构成威胁，但近地小行星的目录仍不完整，其撞击会造成区域性破坏。科学家已经提出若干种方法，可通过使小行星偏转或破坏小行星潜在地防止小行星撞击地球。动能撞击技术试验被确定为与小行星减缓有关的最优先空间任务。

     美国宇航局(NASA)的双小行星重定向测试(DART)任务是对动能撞击技术的全面测试。这次任务的目标小行星是Dimorphos，它是S型双星近地小行星(65803)Didymos的第二个成员。选择这个双星小行星系统是为了使地面望远镜能够量化由DART航天器撞击引起的小行星偏转。

     虽然过去已有任务利用撞击器研究小天体的特性，但早期任务并未计划使目标偏转，也没有实现可测量的偏转。研究者报告了DART航天器对Dimorphos的自主动力学撞击，并重建了撞击事件，包括导致撞击的时间线，DART撞击地点的位置和性质，以及Dimorphos的大小和形状。

     DART航天器与Dimorphos的成功撞击以及由此导致的Dimorphos轨道的变化表明，动能撞击技术是一种可行的技术，可在必要时潜在地保护地球。

     ▲ Abstract：

     Although no known asteroid poses a threat to Earth for at least the next century, the catalogue of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation. Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid. A test of kinetic impact technology was identified as the highest-priority space mission related to asteroid mitigation. NASA’s Double Asteroid Redirection Test (DART) mission is a full-scale test of kinetic impact technology. The mission’s target asteroid was Dimorphos, the secondary member of the S-type binary near-Earth asteroid (65803) Didymos. This binary asteroid system was chosen to enable ground-based telescopes to quantify the asteroid deflection caused by the impact of the DART spacecraft. Although past missions have utilized impactors to investigate the properties of small bodies, those earlier missions were not intended to deflect their targets and did not achieve measurable deflections. Here we report the DART spacecraft’s autonomous kinetic impact into Dimorphos and reconstruct the impact event, including the timeline leading to impact, the location and nature of the DART impact site, and the size and shape of Dimorphos. The successful impact of the DART spacecraft with Dimorphos and the resulting change in the orbit of Dimorphos demonstrates that kinetic impactor technology is a viable technique to potentially defend Earth if necessary.

     Ballistic two-dimensional InSe transistors

     弹道二维硒化铟晶体管

     ▲ 作者：Jianfeng Jiang, Lin Xu, Chenguang Qiu & Lian-Mao Peng

     ▲ 链接：

     https://www.nature.com/articles/s41586-023-05819-w

     ▲ 摘要：

     国际器件和系统路线图(IRDS)预测，对于硅基金属氧化物半导体场效应晶体管(FET)，栅极长度的缩放将停止在12纳米，最终电源电压将不会降低到低于0.6 V。这定义了硅基芯片在缩放过程结束时的最终集成密度和功耗。近年来，具有原子级厚度的二维层状半导体已被探索作为支持进一步小型化和集成电子的潜在通道材料。然而，到目前为止，还没有二维半导体表现出可以超越最先进的硅FET的性能。

     研究者报道了一种以高热速度的二维硒化铟(InSe)作为通道材料的场效应管，对标业界IRDS所预测的硅基器件发展路线图，弹道二维硒化铟晶体管打破了4个硅基终极“红墙”。

     首先，二维硒化铟晶体管沟长缩小至10纳米，超越硅基极限12纳米，器件关态特性超过英特尔商用10纳米节点的硅基最优FinFET晶体管。其次，工作电压可降到0.5伏，超越2031年预计的硅基极限0.6伏。再次，门延时缩短到0.32皮秒，相当于硅基极限(1.26皮秒)的1/4。最后，功耗延迟积缩减到4.32 ×10^-29焦秒/微米，比硅基极限低一个量级。

     ▲ Abstract：

     The International Roadmap for Devices and Systems (IRDS) forecasts that, for silicon-based metal–oxide–semiconductor (MOS) field-effect transistors (FETs), the scaling of the gate length will stop at 12?nm and the ultimate supply voltage will not decrease to less than 0.6?V. This defines the final integration density and power consumption at the end of the scaling process for silicon-based chips. In recent years, two-dimensional (2D) layered semiconductors with atom-scale thicknesses have been explored as potential channel materials to support further miniaturization and integrated electronics. However, so far, no 2D semiconductor-based FETs have exhibited performances that can surpass state-of-the-art silicon FETs. Here we report a FET with 2D indium selenide (InSe) with high thermal velocity as channel material that operates at 0.5?V and achieves record high transconductance of 6?mS?μm?1 and a room-temperature ballistic ratio in the saturation region of 83%, surpassing those of any reported silicon FETs. An yttrium-doping-induced phase-transition method is developed for making ohmic contacts with InSe and the InSe FET is scaled down to 10?nm in channel length. Our InSe FETs can effectively suppress short-channel effects with a low subthreshold swing (SS) of 75?mV per decade and drain-induced barrier lowering (DIBL) of 22?mV?V?1. Furthermore, low contact resistance of 62?Ω?μm is reliably extracted in 10-nm ballistic InSe FETs, leading to a smaller intrinsic delay and much lower energy-delay product (EDP) than the predicted silicon limit.

     Quantum-well states at the surface of a heavy-fermion superconductor

     重费米子超导体表面的量子阱态

     ▲ 作者：Edwin Herrera, Isabel Guillamón, Víctor Barrena, William J. Herrera, Jose Augusto Galvis, Alfredo Levy Yeyati, Ján Rusz, Peter M. Oppeneer, Georg Knebel, Jean Pascal Brison, Jacques Flouquet, Dai Aoki & Hermann Suderow

     ▲ 链接：

     https://www.nature.com/articles/s41586-023-05830-1

     ▲ 摘要：

     在简单的宽带金属如铜(Cu)或银(Ag)中，表面的二维电子态经常被观察到。纳米尺度上的封闭几何结构(如表面阶地)的限制，导致表面能带形成量子化的能级，与体电子能带的连续能量依赖形成鲜明对比。它们的能级分离通常是数百兆电子伏。

     在一类特殊的材料中，强电子相关性导致了所谓的重费米子，其带宽大大减少，并且具有奇异的大块基态。然而，二维重费米子(2DHF)的量子阱态仍然难以观测，因为它们的能量分离很小。

     研究者使用毫开尔文扫描隧道显微镜(STM)研究了重费米子超导体URu2Si2在U端表面的原子平坦梯级，它在温度17.5 K以下表现出神秘的隐藏秩序(HO)状态。研究者观察到由5f个电子组成的2DHF，其有效质量是自由电子质量的17倍。DHF形成量子化态，以meV的几分之一隔开，其能级宽度由与相关体态的相互作用决定。

     阶地之间台阶的边缘状态沿两个平面内方向之一出现，表明表面的电子对称性破坏。研究提出了一条在强相关量子材料中实现量子阱态的新途径，并探索了这些量子阱如何与电子环境相连接。

     ▲ Abstract：

     Two-dimensional electronic states at surfaces are often observed in simple wide-band metals such as Cu or Ag. Confinement by closed geometries at the nanometre scale, such as surface terraces, leads to quantized energy levels formed from the surface band, in stark contrast to the continuous energy dependence of bulk electron bands. Their energy-level separation is typically hundreds of meV. In a distinct class of materials, strong electronic correlations lead to so-called heavy fermions with a strongly reduced bandwidth and exotic bulk ground states. Quantum-well states in two-dimensional heavy fermions (2DHFs) remain, however, notoriously difficult to observe because of their tiny energy separation. Here we use millikelvin scanning tunnelling microscopy (STM) to study atomically flat terraces on U-terminated surfaces of the heavy-fermion superconductor URu2Si2, which exhibits a mysterious hidden-order (HO) state below 17.5?K. We observe 2DHFs made of 5f electrons with an effective mass 17 times the free electron mass. The 2DHFs form quantized states separated by a fraction of a meV and their level width is set by the interaction with correlated bulk states. Edge states on steps between terraces appear along one of the two in-plane directions, suggesting electronic symmetry breaking at the surface. Our results propose a new route to realize quantum-well states in strongly correlated quantum materials and to explore how these connect to the electronic environment.

     化学Chemistry

     Selective methane oxidation by molecular iron catalysts in aqueous medium

     在水介质中分子铁催化剂选择性氧化甲烷

     ▲ 作者：Hiroto Fujisaki, Tomoya Ishizuka, Hiroaki Kotani, Yoshihito Shiota, Kazunari Yoshizawa & Takahiko Kojima

     ▲ 链接：

     https://www.nature.com/articles/s41586-023-05821-2

     ▲ 摘要：

     使用天然气作为化学原料需要有效地氧化组成烷烃，主要是甲烷。目前的工业流程使用高温高压下的蒸汽重整来产生气体混合物，然后进一步转化为甲醇等产品。分子铂催化剂也被用于将甲烷转化为甲醇，但由于过度氧化，它们的选择性通常很低——初始氧化产物往往比甲烷本身更容易氧化。

     本研究表明，具有疏水腔的N-杂环碳连接FeII配合物从水溶液中捕获疏水甲烷底物，并在Fe中心氧化后释放亲水性甲醇产物回溶液中。研究发现，增加疏水空腔的大小可以增强这种效应，在3小时的甲烷氧化反应中，周转数为5.0×10²，甲醇选择性为83%。如果能够克服在水介质中处理甲烷所产生的传输限制，这种捕获和释放策略为利用天然丰富的烷烃资源提供了一种有效的选择途径。

     ▲ Abstract：

     Using natural gas as chemical feedstock requires efficient oxidation of the constituent alkanes—and primarily methane. The current industrial process uses steam reforming at high temperatures and pressures to generate a gas mixture that is then further converted into products such as methanol. Molecular Pt catalysts have also been used to convert methane to methanol8, but their selectivity is generally low owing to overoxidation—the initial oxidation products tend to be easier to oxidize than methane itself. Here we show that N-heterocyclic carbene-ligated FeII complexes with a hydrophobic cavity capture hydrophobic methane substrate from an aqueous solution and, after oxidation by the Fe centre, release a hydrophilic methanol product back into the solution. We find that increasing the size of the hydrophobic cavities enhances this effect, giving a turnover number of 5.0?×?10² and a methanol selectivity of 83% during a 3-h methane oxidation reaction. If the transport limitations arising from the processing of methane in an aqueous medium can be overcome, this catch-and-release strategy provides an efficient and selective approach to using naturally abundant alkane resources.

     Ultrafiltration separation of Am(VI)-polyoxometalate from lanthanides

     多金属氧酸盐与镧系元素的超滤分离

     ▲ 作者：Hailong Zhang, Ao Li, Kai Li, Zhipeng Wang, Xiaocheng Xu, Yaxing Wang, Matthew V. Sheridan, Han-Shi Hu, Chao Xu, Evgeny V. Alekseev, Zhenyi Zhang, Pu Yan, Kecheng Cao, Zhifang Chai, Thomas E. Albrecht-Sch?nzart & Shuao Wang

     ▲ 链接：

     https://www.nature.com/articles/s41586-023-05840-z

     ▲ 摘要：

     乏燃料中镧系元素的分离对核能的可持续发展具有重要意义。这项任务极具挑战性，因为热力学稳定的Am(III)和Ln(III)离子具有几乎相同的离子半径和配位化学。

     作者报道了一个纳米尺度的多金属氧酸盐(POM)簇，其空位位点与六价锕系元素(²³⁸U, ²³⁷Np, ²⁴²Pu和 ²⁴³Am)在硝酸介质中的三价镧系元素选择性配位相容。研究者表示，这个团簇是迄今为止在水介质中观察到的最稳定的Am(VI)物质。

     超滤技术将纳米级Am(VI)-POM簇从水合镧系离子中分离出来，利用市售的细孔膜，实现了一种高效、快速、不涉及任何有机成分、能量输入最少的镅/镧系离子一次性分离策略。

     ▲ Abstract：

     Partitioning of americium from lanthanides (Ln) present in used nuclear fuel plays a key role in the sustainable development of nuclear energy. This task is extremely challenging because thermodynamically stable Am(III) and Ln(III) ions have nearly identical ionic radii and coordination chemistry. Oxidization of Am(III) to Am(VI) produces AmO2²⁺ ions distinct with Ln(III) ions, which has the potential to facilitate separations in principle. However, the rapid reduction of Am(VI) back to Am(III) by radiolysis products and organic reagents required for the traditional separation protocols including solvent and solid extractions hampers practical redox-based separations. Herein, we report a nanoscale polyoxometalate (POM) cluster with a vacancy site compatible with the selective coordination of hexavalent actinides (²³⁸U, ²³⁷Np, ²⁴²Pu and ²⁴³Am) over trivalent lanthanides in nitric acid media. To our knowledge, this cluster is the most stable Am(VI) species in aqueous media observed so far. Ultrafiltration-based separation of nanoscale Am(VI)-POM clusters from hydrated lanthanide ions by commercially available, fine-pored membranes enables the development of a once-through americium/lanthanide separation strategy that is highly efficient and rapid, does not involve any organic components and requires minimal energy input.

     Depolymerization of plastics by means of electrified spatiotemporal heating

     用电热时空加热法解聚塑料

     ▲ 作者：Qi Dong, Aditya Dilip Lele, Xinpeng Zhao, Shuke Li, Sichao Cheng, Yueqing Wang, Mingjin Cui, Miao Guo, Alexandra H. Brozena, Ying Lin, Tangyuan Li, Lin Xu, Aileen Qi, Ioannis G. Kevrekidis, Jianguo Mei, Xuejun Pan, Dongxia Liu, Yiguang Ju & Liangbing Hu

     ▲ 链接：

     https://www.nature.com/articles/s41586-023-05845-8

     ▲ 摘要：

     解聚是一种很有前途的策略，可以将废塑料回收成组成单体，用于随后的再聚合。然而，许多商品塑料不能选择性地解聚使用传统的热化学方法，因为难以控制的反应过程和途径。虽然催化剂可以提高选择性，但它们的性能容易下降。

     作者提出了一种无催化剂，非平衡的热化学解聚方法，可以通过热解从商品塑料聚丙烯(PP)和聚对苯二甲酸乙酯(PET)中生成单体。这种选择性解聚过程通过两个特征来实现：(1)空间温度梯度和(2)时间加热剖面。用这种方法将PP和PET解聚成单体，产率分别为36%和43%左右。总的来说，这种电气化时空加热方法可能为全球塑料垃圾问题提供解决方案。

     ▲ Abstract：

     Depolymerization is a promising strategy for recycling waste plastic into constituent monomers for subsequent repolymerization1. However, many commodity plastics cannot be selectively depolymerized using conventional thermochemical approaches, as it is difficult to control the reaction progress and pathway. Although catalysts can improve the selectivity, they are susceptible to performance degradation2. Here we present a catalyst-free, far-from-equilibrium thermochemical depolymerization method that can generate monomers from commodity plastics (polypropylene (PP) and poly(ethylene terephthalate) (PET)) by means of pyrolysis. This selective depolymerization process is realized by two features: (1) a spatial temperature gradient and (2) a temporal heating profile. Using this approach, we depolymerized PP and PET to their monomers with yields of about 36% and about 43%, respectively. Overall, this electrified spatiotemporal heating (STH) approach potentially offers a solution to the global plastic waste problem.

     编辑 | 方圆

     排版 | 郭刚

    

    

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