《科學》（20200724出版）一周論文導讀

編譯 | 未玖

Science, 24 July 2020, VOL 369, ISSUE 6502

《科學》2020年7月24日，第369卷，6502期

物理學Physics

Determining plasmonic hot-carrier energy distributions via single-molecule transport measurements

單分子輸運測量確定等離子體熱載流子能量分布

▲ 作者：Harsha Reddy, Kun Wang, Zhaxylyk Kudyshev, Linxiao Zhu, Shen Yan, Andrea Vezzoli, et al.

▲ 連結：

https://science.sciencemag.org/content/369/6502/423

▲ 摘要

通過等離子體衰變產生的等離子體納米結構中的熱載流子，在光催化等應用和避開帶隙限制的光電探測器中發揮關鍵作用。然而，到目前為止，對納米結構中熱載流子的穩態能量分布進行直接實驗量化仍頗具挑戰。

研究組提出了單分子結的輸運測量，通過在超薄金膜支撐表面等離子體激元和掃描探針尖端之間捕獲適當選擇的單分子，可對等離子體熱載流子分布進行量化。

研究結果表明，朗道阻尼是在強約束納米級系統產生熱載流子的主要物理機制。這項工作開發的技術可量化等離子體熱載流子在納米光子和等離子體器件中的分布。

▲ Abstract

Hot carriers in plasmonic nanostructures, generated via plasmon decay, play key roles in applications such as photocatalysis and in photodetectors that circumvent bandgap limitations. However, direct experimental quantification of steady-state energy distributions of hot carriers in nanostructures has so far been lacking. We present transport measurements from single-molecule junctions, created by trapping suitably chosen single molecules between an ultrathin gold film supporting surface plasmon polaritons and a scanning probe tip, that can provide quantification of plasmonic hot-carrier distributions. Our results show that Landau damping is the dominant physical mechanism of hot-carrier generation in nanoscale systems with strong confinement. The technique developed in this work will enable quantification of plasmonic hot-carrier distributions in nanophotonic and plasmonic devices.

Remote structuring of near-field landscapes

近場景觀的遠場構建

▲ 作者：Vincent Ginis, Marco Piccardo, Michele Tamagnone, Jinsheng Lu, Min Qiu, Simon Kheifets, et al.

▲ 連結：

https://science.sciencemag.org/content/369/6502/436

▲ 摘要

電磁近場可實現亞波長應用，例如近場顯微鏡和納米粒子操作。目前構造近場的方法依賴於光學天線理論，包括將傳播波局部轉換為受限近場模式的納米結構。

基於級聯模式轉換和不同傳播常數的對嚮導波幹擾，研究組提出了一種遠場而非局部近場塑性理論。他們演示了如何隨意構造近場的縱向和橫向變化，允許超越常規的倏逝場單調衰減分布。

研究組提供了一個實驗來驗證他們的理論。該方法適用於具有任意偏振態和模式輪廓的場，為近場的三維控制提供了一條新途徑。

▲ Abstract

The electromagnetic near field enables subwavelength applications such as near-field microscopy and nanoparticle manipulation. Present methods to structure the near field rely on optical antenna theory, involving nanostructures that locally convert propagating waves into confined near-field patterns. We developed a theory of remote rather than local near-field shaping, based on cascaded mode conversion and interference of counterpropagating guided waves with different propagation constants. We demonstrate how to structure at will the longitudinal and transverse variation of the near field, allowing for distributions beyond the conventional monotonic decay of the evanescent field. We provide an experimental realization that confirms our theory. Our method applies to fields with arbitrary polarization states and mode profiles, providing a path toward three-dimensional control of the near field.

化學Chemistry

Cooperative carbon capture and steam regeneration with tetraamine-appended metal–organic frameworks

四胺金屬有機框架協同碳捕獲與蒸汽再生

▲ 作者：Eugene J. Kim, Rebecca L. Siegelman, Henry Z. H. Jiang, Alexander C. Forse, Jung-Hoon Lee, Jeffrey D. Martell, et al.

▲ 連結：

https://science.sciencemag.org/content/369/6502/392

▲ 摘要

天然氣已成為美國主要的電力來源，從天然氣發電廠的煙道排放中有效去除二氧化碳（CO2）的技術可降低其碳強度。但由於煙道氣流中CO2分壓低，CO2的分離極具挑戰性。

從二胺金屬-有機框架的晶體結構中得到靈感，其表現出兩步協同CO2吸附，研究組報導了一系列保持協同性的穩固的四胺官能化框架，使得在天然氣煙道排放相關的極端條件下，捕獲CO2的效率極高。

四胺有序多金屬配位使材料具有非凡的穩定性，可用於模擬潮溼煙氣的吸附-解吸循環，並可使用低溫蒸汽進行再生，從而替代昂貴的壓力或溫度波動。

▲ Abstract

Natural gas has become the dominant source of electricity in the United States, and technologies capable of efficiently removing carbon dioxide (CO2) from the flue emissions of natural gas–fired power plants could reduce their carbon intensity. However, given the low partial pressure of CO2 in the flue stream, separation of CO2 is particularly challenging. Taking inspiration from the crystal structures of diamine-appended metal–organic frameworks exhibiting two-step cooperative CO2 adsorption, we report a family of robust tetraamine-functionalized frameworks that retain cooperativity, leading to the potential for exceptional efficiency in capturing CO2 under the extreme conditions relevant to natural gas flue emissions. The ordered, multimetal coordination of the tetraamines imparts the materials with extraordinary stability to adsorption-desorption cycling with simulated humid flue gas and enables regeneration using low-temperature steam in lieu of costly pressure or temperature swings.

材料學Materials Science

Ultrahigh-strength and ductile superlattice alloys with nanoscale disordered interfaces

具有納米級無序界面的超高強度韌性超晶格合金

▲ 作者：T. Yang, Y. L. Zhao, W. P. Li, C. Y. Yu, J. H. Luan, D. Y. Lin, et al.

▲ 連結：

https://science.sciencemag.org/content/369/6502/427

▲ 摘要

高溫下具有高強度的合金對包括航空航天在內的許多重要行業都至關重要。具有有序超晶格結構的合金在這方面頗具吸引力，但通常存在延展性差和晶粒粗化迅速的缺點。

研究組發現納米級無序界面可有效克服這些問題。界面無序是由多元素共偏析驅動的，可在相鄰的微米級超晶格晶粒之間形成獨特的納米層。該納米層充當可持續的延展性源，通過增強位錯活動性來防止脆性晶間斷裂。

研究組獲得的超晶格材料具有1.6吉帕的超高強度，在環境溫度下的拉伸延展性為25%。同時，研究組實現了可忽略的晶粒粗化，在高溫下具有特殊的抗軟化性能。設計相似的納米層可為進一步優化合金性能開闢一條新途徑。

▲ Abstract

Alloys that have high strengths at high temperatures are crucial for a variety of important industries including aerospace. Alloys with ordered superlattice structures are attractive for this purpose but generally suffer from poor ductility and rapid grain coarsening. We discovered that nanoscale disordered interfaces can effectively overcome these problems. Interfacial disordering is driven by multielement cosegregation that creates a distinctive nanolayer between adjacent micrometer-scale superlattice grains. This nanolayer acts as a sustainable ductilizing source, which prevents brittle intergranular fractures by enhancing dislocation mobilities. Our superlattice materials have ultrahigh strengths of 1.6 gigapascals with tensile ductilities of 25% at ambient temperature. Simultaneously, we achieved negligible grain coarsening with exceptional softening resistance at elevated temperatures. Designing similar nanolayers may open a pathway for further optimization of alloy properties.

Anomalous absorption of electromagnetic waves by 2D transition metal carbonitride Ti3CNTx (MXene)

二維過渡金屬碳氮化物Ti3CNTx（MXene）對電磁波的異常吸收

▲ 作者：Aamir Iqbal, Faisal Shahzad, Kanit Hantanasirisakul, Myung-Ki Kim, Jisung Kwon, Junpyo Hong, et al.

▲ 連結：

https://science.sciencemag.org/content/369/6502/446

▲ 摘要

為了保護電子電路和可攜式通信設備，消除設備和設備部件之間的串擾，需要輕質、超薄和柔性的電磁幹擾（EMI）屏蔽材料。

研究組展示了具有中等導電性的二維（2D）過渡金屬碳氮化物Ti3CNTx MXene與更具導電性的Ti3C2Tx或相同厚度的金屬箔相比，具有更高的屏蔽效果。Ti3CNTx的這種出色的屏蔽性能是通過熱退火實現的，這歸因於其分層類超材料結構中異常高的電磁波吸收率。

這些結果為設計高級EMI屏蔽材料提供了指導，但也強調了探索電磁波與2D材料相互作用背後的基本機制的必要性。

▲ Abstract

Lightweight, ultrathin, and flexible electromagnetic interference (EMI) shielding materials are needed to protect electronic circuits and portable telecommunication devices and to eliminate cross-talk between devices and device components. Here, we show that a two-dimensional (2D) transition metal carbonitride, Ti3CNTx MXene, with a moderate electrical conductivity, provides a higher shielding effectiveness compared with more conductive Ti3C2Tx or metal foils of the same thickness. This exceptional shielding performance of Ti3CNTx was achieved by thermal annealing and is attributed to an anomalously high absorption of electromagnetic waves in its layered, metamaterial-like structure. These results provide guidance for designing advanced EMI shielding materials but also highlight the need for exploring fundamental mechanisms behind interaction of electromagnetic waves with 2D materials.

考古學Archaeology

Genomic insights into the early peopling of the Caribbean

加勒比海早期人類的基因組學研究

▲ 作者：Kathrin Nägele, Cosimo Posth, Miren Iraeta Orbegozo, Yadira Chinique de Armas, Silvia Teresita Hernández Godoy, Ulises M. González Herrera, et al.

▲ 連結：

https://science.sciencemag.org/content/369/6502/456

▲ 摘要

加勒比海是美洲最後一批人類定居的地區之一，但是他們來自何方，以及到達島嶼的方式和時間仍不清楚。

研究組收集了93例古加勒比島民的全基因組數據，其日期可追溯到3200-400年前，找到了至少三次單獨擴散到該區域的證據，包括兩次早期擴散到西加勒比海，其中一次似乎與北美的輻射事件有關。隨後又從南美擴張。

研究組還檢測到早期定居者與南美新移民之間的基因差異，幾乎沒有混合跡象。研究結果加深了人們對加勒比海地區最初的人口分布以及美洲古代人類遷移的理解。

▲ Abstract

The Caribbean was one of the last regions of the Americas to be settled by humans, but where they came from and how and when they reached the islands remain unclear. We generated genome-wide data for 93 ancient Caribbean islanders dating between 3200 and 400 calibrated years before the present and found evidence of at least three separate dispersals into the region, including two early dispersals into the Western Caribbean, one of which seems connected to radiation events in North America. This was followed by a later expansion from South America. We also detected genetic differences between the early settlers and the newcomers from South America, with almost no evidence of admixture. Our results add to our understanding of the initial peopling of the Caribbean and the movements of Archaic Age peoples in the Americas.