每日短讯：《自然》（20230105出版）一周论文导读

编译 | 冯维维

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Nature, 5 January 2023, Volume 613 Issue 7942

《自然》2023年1月5日，第613卷，第7942期

物理学Physics

Intracluster light is already abundant at redshift beyond unity

超过统一的红移时星团内光已很充足

▲ 作者：Hyungjin Joo & M. James Jee

▲ 链接：

https://www.nature.com/articles/s41586-022-05396-4

▲ 摘要：

星团内光（ICL）是来自恒星的漫射光，这些恒星的引力并非束缚在单个成员星系上，而是束缚在星团的光晕上。作者报道了基于深红外成像数据对1≲z≲2的10个星系团的ICL研究。与主流理论相反，该研究发现ICL在z≳1已经很丰富，平均ICL分数约为17%。

此外，团簇质量与ICL分数以及ICL颜色与团簇中心半径之间均无显著相关性。研究结果表明，逐渐剥离不再是ICL形成的主要机制。相反，研究支持这样一种情况，即主要的ICL的产生与最亮的星系团的形成和增长和/或通过预处理过的杂散恒星的吸积发生。

▲ Abstract：

Intracluster light (ICL) is diffuse light from stars that are gravitationally bound not to individual member galaxies, but to the halo of galaxy clusters. Here we report an ICL study of ten galaxy clusters at 1 ≲ z ≲ 2 based on deep infrared imaging data. Contrary to the leading theories, our study finds that ICL is already abundant at z ≳ 1, with a mean ICL fraction of approximately 17%. Moreover, no significant correlation between cluster mass and ICL fraction or between ICL colour and cluster-centric radius is observed. Our findings suggest that gradual stripping can no longer be the dominant mechanism of ICL formation. Instead, our study supports the scenario wherein the dominant ICL production occurs in tandem with the formation and growth of the brightest cluster galaxies and/or through the accretion of preprocessed stray stars.

Photonic flatband resonances for free-electron radiation

自由电子辐射的光子平带共振

▲ 作者：Yi Yang, Charles Roques-Carmes, Steven E. Kooi, Haoning Tang, Justin Beroz, Eric Mazur, Ido

▲ 链接：

https://www.nature.com/articles/s41586-022-05387-5

▲ 摘要：

平带已成为当代凝聚态物理学和光子学的基石。在电子学中，平带具有相当的能量带宽和库仑相互作用，导致了诸如分数量子霍尔效应和最近在魔角系统中的现象。在光子学中，它们可以实现包括慢光和激光在内的特性。值得注意的是，平带在两个系统中都支持超准直——无衍射波包传播。

尽管如此，平带从未被证明会影响自由电子和光子之间的核心相互作用。它们之间的相互作用对自由电子激光、显微镜和光谱学以及粒子加速器至关重要，但事实上，其相互作用受到了局域电子和扩展光子之间维度不匹配的限制。

作者从理论上揭示了光子平带可以克服这种不匹配，从而显著地促进它们的相互作用。研究者在硅光子晶体板中的绝缘体上设计了平带共振，通过调整其轨迹和速度控制和增强相关的自由电子辐射。他们观察到平带增强的特征，从传统的衍射使史密斯-珀塞尔辐射记录了一个二级增加。

这种增强使自由电子辐射的极化成形和通过电子束测量的光子带的表征成为可能。作者表示，该研究结果支持使用平板带作为强光-电子相互作用的试验台，特别是与高效和紧凑的自由电子光源和加速器相关。

▲ Abstract：

Flatbands have become a cornerstone of contemporary condensed-matter physics and photonics. In electronics, flatbands entail comparable energy bandwidth and Coulomb interaction, leading to correlated phenomena such as the fractional quantum Hall effect and recently those in magic-angle systems. In photonics, they enable properties including slow light and lasing. Notably, flatbands support supercollimation—diffractionless wavepacket propagation—in both systems. Despite these intense parallel efforts, flatbands have never been shown to affect the core interaction between free electrons and photons. Their interaction, pivotal for free-electron lasers, microscopy and spectroscopy, and particle accelerators, is, in fact, limited by a dimensionality mismatch between localized electrons and extended photons. Here we reveal theoretically that photonic flatbands can overcome this mismatch and thus remarkably boost their interaction. We design flatband resonances in a silicon-on-insulator photonic crystal slab to control and enhance the associated free-electron radiation by tuning their trajectory and velocity. We observe signatures of flatband enhancement, recording a two-order increase from the conventional diffraction-enabled Smith–Purcell radiation. The enhancement enables polarization shaping of free-electron radiation and characterization of photonic bands through electron-beam measurements. Our results support the use of flatbands as test beds for strong light–electron interaction, particularly relevant for efficient and compact free-electron light sources and accelerators.

化学Chemistry

Hydroxamic acid pre-adsorption raises the efficiency of cosensitized solar cells

羟肟酸预吸附提高共敏化太阳能电池效率

▲ 作者：Yameng Ren, Dan Zhang, Jiajia Suo, Yiming Cao, Felix T. Eickemeyer, Nick Vlachopoulos, Shaik M. Zakeeruddin, Anders Hagfeldt & Michael Grätzel

▲ 链接：

https://www.nature.com/articles/s41586-022-05460-z

▲ 摘要：

染料敏化太阳能电池（DSCs）通过将光敏剂与电解质或固体电荷传输材料吸附在纳米介孔二氧化钛（TiO2）薄膜表面，将光转化为电。它们具有许多特点，包括透明、多色和低成本制造，可被部署在玻璃幕墙、天窗和温室中。

近年来，敏化剂、氧化还原介质和器件结构的发展提高了DSC的性能，特别是在环境光条件下。为了进一步提高其效率，关键是控制染料分子在TiO2表面的组装，以促进电荷的产生。

作者报道了在TiO2表面预吸附一层羟肟酸衍生物的路线，以改善两种新设计的共吸附增敏剂的染料分子包装和光伏性能，这些增敏剂在整个可见区域定量地收集光。在1.5全球模拟阳光的标准空气质量下，性能最佳的共敏化太阳能电池表现出15.2%的功率转换效率，并表现出长期运行稳定性（500小时）。

具有较大有源面积（2.8 cm2）的器件在较宽的环境光强度范围内表现出28.4%至30.2%的功率转换效率，并且具有较高的稳定性。该发现为方便地获得高性能DSC铺平了道路，并为使用环境光作为能源的低功耗电子设备的电源和电池替代品提供了广阔的应用前景。

▲ Abstract：

Dye-sensitized solar cells (DSCs) convert light into electricity by using photosensitizers adsorbed on the surface of nanocrystalline mesoporous titanium dioxide (TiO2) films along with electrolytes or solid charge-transport materials. They possess many features including transparency, multicolour and low-cost fabrication, and are being deployed in glass facades, skylights and greenhouses. Recent development of sensitizers, redox mediators and device structures has improved the performance of DSCs, particularly under ambient light conditions. To further enhance their efficiency, it is pivotal to control the assembly of dye molecules on the surface of TiO2to favour charge generation. Here we report a route of pre-adsorbing a monolayer of a hydroxamic acid derivative on the surface of TiO2to improve the dye molecular packing and photovoltaic performance of two newly designed co-adsorbed sensitizers that harvest light quantitatively across the entire visible domain. The best performing cosensitized solar cells exhibited a power conversion efficiency of 15.2% (which has been independently confirmed) under a standard air mass of 1.5 global simulated sunlight, and showed long-term operational stability (500 h). Devices with a larger active area of 2.8 cm2exhibited a power conversion efficiency of 28.4% to 30.2% over a wide range of ambient light intensities, along with high stability. Our findings pave the way for facile access to high-performance DSCs and offer promising prospects for applications as power supplies and battery replacements for low-power electronic devices that use ambient light as their energy source.

Solar-to-hydrogen efficiency of more than 9% in photocatalytic water splitting

光催化裂解水的太阳能制氢效率超过9%

▲ 作者：Peng Zhou, Ishtiaque Ahmed Navid, Yongjin Ma, Yixin Xiao, Ping Wang, Zhengwei Ye, Baowen Zhou, Kai Sun & Zetian Mi

▲ 链接：

https://www.nature.com/articles/s41586-022-05399-1

▲ 摘要：

用阳光和水生产氢燃料，是实现碳中和最有希望的途径之一。一些太阳能制氢方法，例如光电化学水分解，通常需要腐蚀性电解质，限制了其性能稳定性和环境可持续性。另外，清洁的氢可以直接从阳光和水中通过光催化水分解产生。

然而，光催化水分解的太阳能制氢（STH）效率一直很低。作者开发了一种策略，使用纯水、聚光太阳能和氮化铟镓光催化剂，实现了9.2%的高效率。

这一策略的成功源于在最佳反应温度（约70摄氏度）下操作，促进氢-氧正向进化和抑制氢-氧反向重组的协同效应，这可以通过收集太阳光中先前浪费的红外光直接实现。

此外，这种依赖温度的策略也使得从广泛使用的自来水和海水中获得约7%的STH效率，在太阳能容量为257瓦的大规模光催化水分解系统中获得6.2%的STH效率。该研究提供了一种利用自然太阳光和水高效生产氢燃料的实用方法，克服了太阳能制氢的效率瓶颈。

▲ Abstract：

Production of hydrogen fuel from sunlight and water, two of the most abundant natural resources on Earth, offers one of the most promising pathways for carbon neutrality. Some solar hydrogen production approaches, for example, photoelectrochemical water splitting, often require corrosive electrolyte, limiting their performance stability and environmental sustainability. Alternatively, clean hydrogen can be produced directly from sunlight and water by photocatalytic water splitting. The solar-to-hydrogen (STH) efficiency of photocatalytic water splitting, however, has remained very low. Here we have developed a strategy to achieve a high STH efficiency of 9.2 per cent using pure water, concentrated solar light and an indium gallium nitride photocatalyst. The success of this strategy originates from the synergistic effects of promoting forward hydrogen–oxygen evolution and inhibiting the reverse hydrogen–oxygen recombination by operating at an optimal reaction temperature (about 70 degrees Celsius), which can be directly achieved by harvesting the previously wasted infrared light in sunlight. Moreover, this temperature-dependent strategy also leads to an STH efficiency of about 7 per cent from widely available tap water and sea water and an STH efficiency of 6.2 per cent in a large-scale photocatalytic water-splitting system with a natural solar light capacity of 257 watts. Our study offers a practical approach to produce hydrogen fuel efficiently from natural solar light and water, overcoming the efficiency bottleneck of solar hydrogen production.

地球物理学Geophysics

Neogene burial of organic carbon in the global ocean

全球海洋中有机碳的新近纪埋藏

▲ 作者：Ziye Li, Yi Ge Zhang, Mark Torres & Benjamin J. W. Mills

▲ 链接：

https://www.nature.com/articles/s41586-022-05413-6

▲ 摘要：

埋在海洋沉积物中的有机碳是大气二氧化碳的净汇和氧气的来源。在整个地球地质历史中，有机碳埋藏率通常是通过利用无机碳和有机碳之间的质量平衡来确定的，两者都具有不同的碳同位素值（δ13C）。

然而，这种方法具有很大的不确定性因而变得复杂，并且未用有机碳积累数据进行过测试。作者报告了一种“自下而上”的方法，用于计算有机碳掩埋率，该方法独立于质量平衡计算。

研究者利用全球分布的81个地点的数据建立了新近纪（约2300万年~300万年前）有机碳埋藏的历史。研究结果表明有机碳埋藏的时空变异性比以前估计的要大。从全球看，中新世早期和上新世埋藏率较高，中新世中期埋藏率最低，后一时期有机质-碳酸盐埋藏率最低。

这与早期将中新世中期碳酸盐13C富集值解释为大量有机碳埋藏（即蒙特雷假说）的工作相反。暖中新世中期有机碳埋藏抑制可能与细菌对有机质的温度依赖性降解有关，表明有机碳循环对过去全球变暖起到了正反馈作用。

▲ Abstract：

Organic carbon buried in marine sediment serves as a net sink for atmospheric carbon dioxide and a source of oxygen. The rate of organic carbon burial through geologic history is conventionally established by using the mass balance between inorganic and organic carbon, each with distinct carbon isotopic values (δ13C). This method is complicated by large uncertainties, however, and has not been tested with organic carbon accumulation data5. Here we report a ‘bottom-up’ approach for calculating the rate of organic carbon burial that is independent from mass balance calculations. We use data from 81 globally distributed sites to establish the history of organic carbon burial during the Neogene (roughly 23–3 Ma). Our results show larger spatiotemporal variability of organic carbon burial than previously estimated. Globally, the burial rate is high towards the early Miocene and Pliocene and lowest during the mid-Miocene, with the latter period characterized by the lowest ratio of organic-to-carbonate burial rates. This is in contrast to earlier work that interpreted enriched carbonate 13C values of the mid-Miocene as massive organic carbon burial (that is, the Monterey Hypothesis). Suppressed organic carbon burial during the warm mid-Miocene is probably related to temperature-dependent bacterial degradation of organic matter, suggesting that the organic carbon cycle acted as positive feedback of past global warming.

Extreme redox variations in a superdeep diamond from a subducted slab

来自俯冲板块的超深钻石极端氧化还原变化

▲ 作者：Fabrizio Nestola, Margo E. Regier, Robert W. Luth, D. Graham Pearson, Thomas Stachel, Catherine McCammon, Michelle D. Wenz, Steven D. Jacobsen, Chiara Anzolini, Luca Bindi & Jeffrey W. Harris

▲ 链接：

https://www.nature.com/articles/s41586-022-05392-8

▲ 摘要：

富挥发分俯冲板块的引入可能在局部产生较大的氧化还原梯度，影响相稳定性、元素分配和挥发分形态。作者研究了几内亚坎坎钻石包裹体中记录的深层地幔氧化还原条件。顽火辉石、铁方石和一种独特的富镁橄榄石包裹体表明，它是在660公里地震间断区附近高度变化的氧化还原条件下形成的。

作者提出了过渡区-下地幔边界暖板底部的脱水、再水化和脱水模型。在一个皱褶的板块中，由于脱水而释放出的流体，受到来自下地幔的加热的驱动，上升到板块较冷的内部，水在那里被隔离在新的含水矿物中。剩余流体随后的分馏产生极低的还原条件，形成Mg端元环木岩。

这种分馏液也析出主金刚石。在持续加热的情况下，钻石周围的板坯中的菱木矿形成了桥晶石和铁方石，当钻石在加热板坯脱水产生的含水流体中生长时，它们被困住。

▲ Abstract：

The introduction of volatile-rich subducting slabs to the mantle may locally generate large redox gradients, affecting phase stability, element partitioning and volatile speciation1. Here we investigate the redox conditions of the deep mantle recorded in inclusions in a diamond from Kankan, Guinea. Enstatite (former bridgmanite), ferropericlase and a uniquely Mg-rich olivine (Mg# 99.9) inclusion indicate formation in highly variable redox conditions near the 660 km seismic discontinuity. We propose a model involving dehydration, rehydration and dehydration in the underside of a warming slab at the transition zone–lower mantle boundary. Fluid liberated by dehydration in a crumpled slab, driven by heating from the lower mantle, ascends into the cooler interior of the slab, where the H2O is sequestered in new hydrous minerals. Consequent fractionation of the remaining fluid produces extremely reducing conditions, forming Mg-end-member ringwoodite. This fractionating fluid also precipitates the host diamond. With continued heating, ringwoodite in the slab surrounding the diamond forms bridgmanite and ferropericlase, which is trapped as the diamond grows in hydrous fluids produced by dehydration of the warming slab.

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