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2024年12月31日，《科学》（20220506出版）一周论文导读2022-05-08 20:00·科学网编译 | 李言Science, 6 MAY 2022, VOLUME 376 ISSUE 6593《科学》2022年5月6日，第376卷，6593期化学ChemistryThe state of zinc in methanol synthesis over a Zn/ZnO/Cu(211) model catalystZn/ZnO/Cu(211)模型催化剂在甲醇合成中锌的状态▲ PETER AMANN, BERNHARD KL?TZER, DAVID DEGERMAN et al.▲ 链接：https://www.science.org/doi/10.1126/science.abj7747▲ 摘要：在二氧化碳/一氧化碳(CO2/CO)加氢过程中，锌-铜(Zn-Cu)催化剂中锌(Zn)的活性化学状态分为氧化锌纳米粒子、金属锌或锌-铜表面合金。我们利用180—500毫巴的x射线光电子能谱，探测了在Zn/ZnO/Cu(211)上二氧化碳/一氧化碳加氢过程中锌和反应中间体的性质。在这个过程中，温度足够高使得反应可以迅速翻转，从而产生一个几乎不受吸附的表面。通过调整掠入射率，可以实现表面灵敏或整体灵敏。二氧化碳加氢时，氧化锌优先以团簇或纳米颗粒的形式出现，而纯一氧化碳中，锌-铜表面合金更为突出。结果表明，一氧化碳作为活性相在锌-铜表面合金的形成过程中具有特殊的作用，对CO2还原为甲醇特别有效。▲ Abstract：The active chemical state of zinc (Zn) in a zinc-copper (Zn-Cu) catalyst during carbon dioxide/carbon monoxide (CO2/CO) hydrogenation has been debated to be Zn oxide (ZnO) nanoparticles, metallic Zn, or a Zn-Cu surface alloy. We used x-ray photoelectron spectroscopy at 180 to 500 millibar to probe the nature of Zn and reaction intermediates during CO2/CO hydrogenation over Zn/ZnO/Cu(211), where the temperature is sufficiently high for the reaction to rapidly turn over, thus creating an almost adsorbate-free surface. Tuning of the grazing incidence angle makes it possible to achieve either surface or bulk sensitivity. Hydrogenation of CO2 gives preference to ZnO in the form of clusters or nanoparticles, whereas in pure CO a surface Zn-Cu alloy becomes more prominent. The results reveal a specific role of CO in the formation of the Zn-Cu surface alloy as an active phase that facilitates efficient CO2methanol synthesis.Highly efficient catalytic production of oximes from ketones using in situ–generated H2O2原位合成过氧化氢实现尼龙单体的高效合成▲ 作者：RICHARD J. LEWIS, KENJI UEURAXI LIU, YUKIMASA FUKUTA et al.▲ 链接：https://www.science.org/doi/10.1126/science.abl4822▲ 摘要：我们证明，负载的金-钯(AuPd)合金纳米粒子与钛硅酸盐-1 (TS-1)催化剂结合，可以根据需要原位产生H2O2，产生选择性>95%的环己酮肟，可与当前的工业方式相媲美。我们还证明了几个其他的简单酮的氨肟化。我们的方法消除了运输和储存高浓度H2O2的需要，间接实现了大量的环境和经济成本节约。这种方法可以为目前依赖预先形成的H2O2和TS-1组合的多种化学转化提供替代方式，同时允许相当大的工艺强化。▲ Abstract：We demonstrate that by using supported gold-palladium (AuPd) alloyed nanoparticles in conjunction with a titanium silicate-1 (TS-1) catalyst, H2O2 can be generated in situ as needed, producing cyclohexanone oxime with >95% selectivity, comparable to the current industrial route. The ammoximation of several additional simple ketones is also demonstrated. Our approach eliminates the need to transport and store highly concentrated, stabilized H2O2, potentially achieving substantial environmental and economic savings. This approach could form the basis of an alternative route to numerous chemical transformations that are currently dependent on a combination of preformed H2O2and TS-1, while allowing for considerable process intensification.物理PhysicsTunable and state-preserving frequency conversion of single photons in hydrogen氢中单个光子的可调谐和状态保持的频率转换▲ 作者：R. TYUMENEV, J. HAMMER, N. Y. JOLY et al.▲ 链接：https://www.science.org/doi/10.1126/science.abn1434▲ 摘要：在现代量子技术中，保持频率转换后的量子光学态的光子统计是量子网络可行实现的关键，这通常需要在不同光谱区域工作的几个子系统接口。目前的大多数方法只能提供非常小的频移和有限的可调谐性，同时受到来自所使用材料的高插入损耗和拉曼噪声的影响。在此，我们介绍一种利用充氢反共振反射光子晶体光纤实现保持量子相关频率转换的方法。由受激拉曼散射产生的瞬态光学声子可使纠缠对的空闲光子进行125太赫兹的频率转换，效率高达70%。这种分子调制过程保持了量子相关性，使其在量子信息中的应用非常理想。▲ Abstract：In modern quantum technologies, preservation of the photon statistics of quantum optical states upon frequency conversion holds the key to the viable implementation of quantum networks, which often require interfacing of several subsystems operating in widely different spectral regions. Most current approaches offer only very small frequency shifts and limited tunability, while suffering from high insertion loss and Raman noise originating in the materials used. We introduce a route to quantum-correlation–preserving frequency conversion using hydrogen-filled antiresonant-reflecting photonic crystal fibers. Transient optical phonons generated by stimulated Raman scattering enable selective frequency up-conversion by 125 terahertz of the idler photon of an entangled pair, with efficiencies up to 70%. This threshold-less molecular modulation process preserves quantum correlations, making it ideal for applications in quantum information.材料科学Materials ScienceEmergent ferroelectricity in subnanometer binary oxide films on silicon硅上集成的亚纳米二元氧化物薄膜中的铁电性▲ 作者：SURAJ S. CHEEMA, NIRMAAN SHANKER, HANG-LIN HSU et al.▲ 链接：https://www.science.org/doi/10.1126/science.abm8642▲ 摘要：电压可切换电偶极子的临界尺寸限制对节能电子器件有着广泛的影响，强调了在降维下稳定铁电序的重要性。在此，我们报告硅上集成二氧化锆薄膜中与厚度相关的反铁电-铁电相变反应。超薄二氧化锆（通常是一种顺电材料）中出现的铁电性和迟滞极化开关，能在薄膜厚度低至5埃时依旧持续。这种利用三维中心对称材料沉积到二维厚度极限的方法，特别是在这种具有非常规铁电尺寸效应的结构系统模型中，为电子技术提供了巨大的前景。这一点可由硅上集成原子尺度非易失性铁电存储器证明。此外，它还表明隐藏的电子现象可以在广泛的简单二元材料中实现。▲ Abstract：The critical size limit of voltage-switchable electric dipoles has extensive implications for energy-efficient electronics, underlying the importance of ferroelectric order stabilized at reduced dimensionality. We report on the thickness-dependent antiferroelectric-to-ferroelectric phase transition in zirconium dioxide (ZrO2) thin films on silicon. The emergent ferroelectricity and hysteretic polarization switching in ultrathin ZrO2, conventionally a paraelectric material, notably persists down to a film thickness of 5 angstroms, the fluorite-structure unit-cell size. This approach to exploit three-dimensional centrosymmetric materials deposited down to the two-dimensional thickness limit, particularly within this model fluorite-structure system that possesses unconventional ferroelectric size effects, offers substantial promise for electronics, demonstrated by proof-of-principle atomic-scale nonvolatile ferroelectric memory on silicon. Additionally, it is also indicative of hidden electronic phenomena that are achievable across a wide class of simple binary materials.地球科学Earth ScienceA dynamic saline groundwater system mapped beneath an Antarctic ice stream南极冰流下动态的含盐地下水系统▲ 作者：CHLOE D. GUSTAFSON, KERRY KEY, MATTHEW R. SIEGFRIED et al.▲ 链接：https://www.science.org/doi/10.1126/science.abm3301▲ 摘要：南极洲快速流动的冰流对冰盖造成耗损，然而其速度受冰下水系统的影响。目前对这些水流系统的了解仅限于靠近冰床界面的浅层部分，但也有假设认为更深的地下水也可能影响冰流。在此，我们使用了南极西部惠兰斯冰流的地球磁场和被动地震数据，对深层亚冰流地下水进行了首次观测。我们的数据显示，在一个超过1公里厚的沉积盆地中有比已知的冰下系统大一个数量级的地下水。垂直盐度梯度数据表明，深层的古海水与上方的现代融水之间存在交换。我们的研究结果为影响冰流和冰下生物地球化学过程的冰下水系统提供了新的限制条件。▲ Abstract：Antarctica’s fast-flowing ice streams drain the ice sheet, with their velocity modulated by subglacial water systems. Current knowledge of these water systems is limited to the shallow portions near the ice-bed interface, but hypothesized deeper groundwater could also influence ice streaming. Here, we use magnetotelluric and passive seismic data from Whillans Ice Stream, West Antarctica, to provide the first observations of deep sub–ice stream groundwater. Our data reveal a volume of groundwater within a >1-kilometer-thick sedimentary basin that is more than an order of magnitude larger than the known subglacial system. A vertical salinity gradient indicates exchange between paleo seawater at depth and contemporary basal meltwater above. Our results provide new constraints for subglacial water systems that affect ice streaming and subglacial biogeochemical processes.A stronger role for long-term moisture change than for CO2 in determining tropical woody vegetation change长期水分变化在决定热带木本植被变化方面比二氧化碳的作用更大▲ 作者：WILLIAM D. GOSLING, CHARLOTTE S. MILLER, TIMOTHY M. SHANAHAN et al.▲ 链接：https://www.science.org/doi/10.1126/science.abg4618▲ 摘要：有人认为，人为CO2 (eCO2) 浓度的升高会通过增加营养物质带动热带生态系统内的木本覆盖。eCO2 的影响被置于地球系统模型中评估，尽管长期评估仍然具有挑战性。在此，我们通过对加纳Bosumtwi湖此前的环境变化数据与全球数据的耦合，探讨了过去50万年间西非植被变化的6个驱动因素（水分有效性、火灾、哺乳动物食草动物密度、温度、温度季节性变化、CO2）的相关性。水分有效性和火灾是影响林分覆盖度的主要因素，而CO2 的影响较小。我们的研究结果表明，预测模型中eCO2 效应对热带植被的作用必须被重新考虑。▲ Abstract：Anthropogenically elevated CO2 (eCO2) concentrations have been suggested to increase woody cover within tropical ecosystems through fertilization. The effect of eCO2 is built into Earth system models, although testing the relationship over long periods remains challenging. Here, we explore the relative importance of six drivers of vegetation change in western Africa over the past ~500,000 years (moisture availability, fire activity, mammalian herbivore density, temperature, temperature seasonality, CO2) by coupling past environmental change data from Lake Bosumtwi (Ghana) with global data. We found that moisture availability and fire activity were the most important factors in determining woody cover, whereas the effect of CO2 was small. Our findings suggest that the role of eCO2 effects on tropical vegetation in predictive models must be reconsidered.
《JAPONENSIS水多多》动漫在线观看- 全集日本动漫- 5G...
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