Science, 19 AUG 2022, VOL 377, ISSUE 6608
《科学》2022年8月19日，第377卷，6608期
化学Chemistry
Low-temperature mineralization of perfluorocarboxylic acids
全氟羧酸的低温矿化
▲ 作者：BRITTANY TRANG, YULI LI, XIAO-SONG XUE et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abm8868
▲ 摘要：
全氟化合物（PFAS）是水资源中存在的持久性、生物累积性污染物，对人类健康有害。虽然目前的PFAS破坏策略采用非选择性破坏机制，但我们发现，全氟烷基羧酸（PFCAs）可以通过氢氧化钠介导的脱氟途径矿化。
PFCA在极性非质子溶剂中脱羧，产生在24小时内降解为氟离子（78 ~100%）的活性全氟烷基离子中间体。含碳中间体和其产物与通常提出的单碳链缩短机制不一致，我们通过计算确定了与许多实验结果一致的路径。
我们还观察到了支链全氟烷基醚羧酸的降解，并可能扩展到降解其他PFAS类物质，同时激活它们的极性头基。
▲ Abstract：
Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative pollutants found in water resources at concentrations harmful to human health. Whereas current PFAS destruction strategies use nonselective destruction mechanisms, we found that perfluoroalkyl carboxylic acids (PFCAs) could be mineralized through a sodium hydroxide–mediated defluorination pathway. PFCA decarboxylation in polar aprotic solvents produced reactive perfluoroalkyl ion intermediates that degraded to fluoride ions (78 to ~100%) within 24 hours. The carbon-containing intermediates and products were inconsistent with oft-proposed one-carbon-chain shortening mechanisms, and we instead computationally identified pathways consistent with many experiments. Degradation was also observed for branched perfluoroalkyl ether carboxylic acids and might be extended to degrade other PFAS classes as methods to activate their polar headgroups are identified.
Structures of the nitrogenase complex prepared under catalytic turnover conditions
催化周转条件下制备的固氮酶复合物结构
▲ 作者：HANNAH L. RUTLEDGE, BRIAN D. COOK, HOANG P. M. NGUYEN et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abq7641
▲ 摘要：
酶氮化酶偶联三磷酸腺苷（ATP）水解多电子还原大气二氮成氨。尽管有广泛的研究，ATP依赖的能量转导和氮气还原的机制细节还不清楚，需要新的策略来监测催化作用期间的结构动力学。
在此，我们报告了在酶周转条件下制备的固氮酶复合物的冷冻电子显微镜结构。我们观察到，不对称性支配着固氮酶机制的所有方面，包括ATP水解、蛋白-蛋白相互作用和催化。催化铁钼辅因子附近的构型变化与酶的核苷酸水解状态相关。
▲ Abstract：
The enzyme nitrogenase couples adenosine triphosphate (ATP) hydrolysis to the multielectron reduction of atmospheric dinitrogen into ammonia. Despite extensive research, the mechanistic details of ATP-dependent energy transduction and dinitrogen reduction by nitrogenase are not well understood, requiring new strategies to monitor its structural dynamics during catalytic action. Here, we report cryo–electron microscopy structures of the nitrogenase complex prepared under enzymatic turnover conditions. We observe that asymmetry governs all aspects of the nitrogenase mechanism, including ATP hydrolysis, protein-protein interactions, and catalysis. Conformational changes near the catalytic iron-molybdenum cofactor are correlated with the nucleotide-hydrolysis state of the enzyme.
材料科学Material Science
Flexible thermoelectrics based on ductile semiconductors
基于延展性半导体的柔性热电器件
▲ 作者：QINGYU YANG, SHIQI YANG, PENGFEI QIU et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abq0682
▲ 摘要：
柔性热电为开发便携式和可持续的柔性电源提供了不同的解决方案。硫化银基延性半导体的发现推动了柔性热电器件潜力的转变，但缺乏良好的p型延性热电材料限制了传统跨平面π形柔性器件的制造。
我们报告了一系列基于AgCu(Se,S,Te)伪三元固溶体中的成分-性能相图的p型韧性热电材料，与其他柔性热电材料相比，具有较高的优点值（在300开尔文时为0.45，340开尔文下为0.68）。
我们进一步展示了薄而灵活的π形器件，其最大归一化功率密度可达30 μW cm−2 K−2。这种输出有望在可穿戴电子产品中使用柔性热电体。
▲ Abstract：
Flexible thermoelectrics provide a different solution for developing portable and sustainable flexible power supplies. The discovery of silver sulfide–based ductile semiconductors has driven a shift in the potential for flexible thermoelectrics, but the lack of good p-type ductile thermoelectric materials has restricted the reality of fabricating conventional cross-plane π-shaped flexible devices. We report a series of high-performance p-type ductile thermoelectric materials based on the composition-performance phase diagram in AgCu(Se,S,Te) pseudoternary solid solutions, with high figure-of-merit values (0.45 at 300 kelvin and 0.68 at 340 kelvin) compared with other flexible thermoelectric materials. We further demonstrate thin and flexible π-shaped devices with a maximum normalized power density that reaches 30 μWcm−2 K−2. This output is promising for the use of flexible thermoelectrics in wearable electronics.
Chip-less wireless electronic skins by remote epitaxial freestanding compound semiconductors
利用远程外延独立化合物半导体实现无芯片无线电子皮肤
▲ 作者：YEONGIN KIM, JUN MIN SUH, JIHO SHINYUNPENG LIU et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abn7325
▲ 摘要：
最近在柔性和可拉伸电子产品方面的进展推动了基于电子皮肤（e-skin）的健康监测平台的增多。传统的无线电子皮肤依赖于刚性的集成电路芯片，这不仅损害了整体的灵活性，同时也会消耗相当大的电力。基于电感电容谐振器的无芯片无线电子皮肤受限于灵敏度较低的机械传感器。
我们报告一种基于独立式超薄单晶压电氮化镓薄膜表面声波传感器的无晶片无线电子皮肤。这种基于表面声波的电子皮肤可以提供对应变、紫外线和汗水中的离子浓度的高灵敏度、低功率的长期监测。
我们示范了为期一周的脉搏检测。这些结果展示了无线健康监测设备可以提供低廉、通用、低耗能及高灵敏度服务的途径。
▲ Abstract：
Recent advances in flexible and stretchable electronics have led to a surge of electronic skin (e-skin)–based health monitoring platforms. Conventional wireless e-skins rely on rigid integrated circuit chips that compromise the overall flexibility and consume considerable power. Chip-less wireless e-skins based on inductor-capacitor resonators are limited to mechanical sensors with low sensitivities. We report a chip-less wireless e-skin based on surface acoustic wave sensors made of freestanding ultrathin single-crystalline piezoelectric gallium nitride membranes. Surface acoustic wave–based e-skin offers highly sensitive, low-power, and long-term sensing of strain, ultraviolet light, and ion concentrations in sweat. We demonstrate weeklong monitoring of pulse. These results present routes to inexpensive and versatile low-power, high-sensitivity platforms for wireless health monitoring devices.
Nanocrystals with metastable high-pressure phases under ambient conditions
环境条件下具有亚稳态高压相的纳米晶体
▲ 作者：TIANYUAN XIAO, YASUTAKA NAGAOKA, XIRUI WANG et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abq7684
▲ 摘要：
在由硒化镉、硫化镉或两者都包含的纳米球或纳米棒组成的明确模型系统中，研究了岩盐相的环境亚稳性，其组成、初始晶相、颗粒结构、形状、表面功能化和它们组合的有序水平的函数。我们的实验表明，这些纳米晶体系统在岩盐到锌闪锌矿的固相转变中表现出配体可调整的可逆性。
利用颗粒间烧结技术在相变过程中制造动力学势垒，以可控的方式产生环境压力亚稳的岩盐结构。这些发现提出了转换屏障工程的一般规则，这对下一代材料的合理设计很有用。
▲ Abstract：
The ambient metastability of the rock-salt phase in well-defined model systems comprising nanospheres or nanorods of cadmium selenide, cadmium sulfide, or both was investigated as a function of composition, initial crystal phase, particle structure, shape, surface functionalization, and ordering level of their assemblies. Our experiments show that these nanocrystal systems exhibit ligand-tailorable reversibility in the rock salt–to–zinc blende solid-phase transformation. Interparticle sintering was used to engineer kinetic barriers in the phase transformation to produce ambient-pressure metastable rock-salt structures in a controllable manner. Interconnected nanocrystal networks were identified as an essential structure that hosted metastable high-energy phases at ambient conditions. These findings suggest general rules for transformation-barrier engineering that are useful in the rational design of next-generation materials.
物理学Physics
Tweezer-programmable 2D quantum walks in a Hubbard-regime lattice
在哈伯德区晶格中的镊子可编程二维量子行走
▲ 作者：AARON W. YOUNG, WILLIAM J. ECKNER, NATHAN SCHINE et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abo0608
▲ 摘要：
量子行走为设计量子算法提供了一个既直观又通用的框架。为了利用这些量子行走的计算能力，能够以编程的方式修改行走产生的图像的同时保持一致性，就变得尤为重要。
我们通过将光镊提供的快速、可编程控制与可伸缩、均匀的光学晶格环境相结合来实现这一点。利用这些工具，我们研究了单原子在正方形晶格上的连续时间量子行走，并利用这些行走执行空间搜索的原理证明演示。
当扩展到更多的粒子时，展示的能力可以扩展到研究量子信息科学中的许多问题，包括使用更大的、连接增加的图像来执行更有效的空间检索。
▲ Abstract：
Quantum walks provide a framework for designing quantum algorithms that is both intuitive and universal. To leverage the computational power of these walks, it is important to be able to programmably modify the graph a walker traverses while maintaining coherence. We do this by combining the fast, programmable control provided by optical tweezers with the scalable, homogeneous environment of an optical lattice. With these tools we study continuous-time quantum walks of single atoms on a square lattice and perform proof-of-principle demonstrations of spatial search with these walks. When scaled to more particles, the capabilities demonstrated can be extended to study a variety of problems in quantum information science, including performing more effective versions of spatial search using a larger graph with increased connectivity.
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