编译 | 未玖
Science, 5 JAN 2024, VOL 383, ISSUE 6678
《科学》2024年1月5日，第383卷，6678期
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物理学Physics
De Haas–van Alphen spectroscopy and magnetic breakdown in moiré graphene
莫尔石墨烯中德哈斯-范阿尔芬光谱学和磁击穿
▲ 作者：Matan Bocarsly, Matan Uzan, Indranil Roy, Sameer Grover, Jiewen Xiao, Zhiyu Dong, et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adh3499
▲ 摘要：
源自电子回旋轨道量子化的量子振荡可用于对电子能带和相互作用的灵敏诊断。
研究组报道了莫尔石墨烯中由德哈斯-范阿尔芬效应引起的热力学磁化振荡的纳米级成像。利用探针超导量子干涉装置（SQUID）在与六方氮化硼轴向对齐的伯纳尔双层石墨烯晶体中进行扫描，他们发现了在弱磁场下每电子振幅高达500玻尔磁子的较大磁化震荡，频率低得出乎意料，并且对超晶格填充分数高度敏感。
这些振荡使人们能够重建复杂的能带结构，揭示出由极小动量隙分开的多个重叠费米面的窄莫尔带。研究组确定了颠覆教科书的昂萨格费米面和规则振荡集，这标志着由相干磁击穿引起的宽带粒子-空穴叠加态的形成。
▲ Abstract：
Quantum oscillations originating from the quantization of electron cyclotron orbits provide sensitive diagnostics of electron bands and interactions. We report on nanoscale imaging of the thermodynamic magnetization oscillations caused by the de Haas–van Alphen effect in moiré graphene. Scanning by means of superconducting quantum interference device (SQUID)–on-tip in Bernal bilayer graphene crystal axis-aligned to hexagonal boron nitride reveals large magnetization oscillations with amplitudes reaching 500 Bohr magneton per electron in weak magnetic fields, unexpectedly low frequencies, and high sensitivity to superlattice filling fraction. The oscillations allow us to reconstruct the complex band structure, revealing narrow moiré bands with multiple overlapping Fermi surfaces separated by unusually small momentum gaps. We identified sets of oscillations that violate the textbook Onsager Fermi surface sum rule, signaling formation of broad-band particle-hole superposition states induced by coherent magnetic breakdown.
材料科学Materials Science
Supramolecular assembly of blue and green halide perovskites with near-unity photoluminescence
具有近100%光致发光的蓝绿光卤化物钙钛矿的超分子组装
▲ 作者：Cheng Zhu, Jianbo Jin, Zhen Wang, Zhenpeng Xu, Maria C. Folgueras, Yuxin Jiang, et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adi4196
▲ 摘要：
金属卤化物离子八面体是卤化物钙钛矿的光电单元，冠醚辅助的超分子组装法可将各种离子八面体组装为可调的对称性结构。
研究组用卤化铪（Hf）和卤化锆（Zr）八面体簇的超分子组装证明了近100%光致发光量子产率（PLQY）蓝光和绿光发射。(18C6@K)2HfBr6粉末呈现近100% PLQY（96.2%）的蓝光发射，(18C6@K)2ZrCl4Br2粉末呈现PLQY为82.7%的绿光发射。
这些高发射性粉末的特点是可在低温溶液合成条件下简易合成，在环境条件、溶液可加工的半导体油墨中保持高PLQY，可用于具有高空间分辨率的薄膜显示器和发射性三维打印架构。
▲ Abstract：
The metal-halide ionic octahedron is the optoelectronic unit for halide perovskites, and a crown ether–assisted supramolecular assembly approach can pack various ionic octahedra into tunable symmetries. In this work, we demonstrate near-unity photoluminescence quantum yield (PLQY) blue and green emission with the supramolecular assembly of hafnium (Hf) and zirconium (Zr) halide octahedral clusters. (18C6@K)2HfBr6 powders showed blue emission with a near-unity PLQY (96.2%), and green emission was also achieved with (18C6@K)2ZrCl4Br2 powders at a PLQY of 82.7%. These highly emissive powders feature facile low-temperature solution-based synthesis conditions and maintain high PLQY in solution-processable semiconductor inks under ambient conditions, and they were used in thin-film displays and emissive three-dimensional–printed architectures that exhibited high spatial resolution.
Thermodynamically stable plumber’s nightmare structures in block copolymers
嵌段共聚物中热动力稳定的“管道工噩梦”结构
▲ 作者：Hojun Lee, Sangwoo Kwon, Jaemin Min, Seon-Mi Jin, Jun Ho Hwang, Eunji Lee, et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adh0483
▲ 摘要：
嵌段共聚物自组装提供了从球体、圆柱体到网络的各种纳米结构，在纳米尺度上对性能和功能进行了精细控制。然而，创造高堆积受挫、热力学稳定的网络结构仍颇具挑战。
研究组报道了一种利用端基和连接体化学从二嵌段共聚物中获取不同网络结构（如螺旋相、金刚石相和原始相）的方法。聚合物链末端（“管道工噩梦”结构）中间堆积对于骨架聚集（螺旋相）的稳定性归因于端-端相互作用的强度和曲率初始形状之间的相互作用。
该研究实现了从嵌段共聚物中开发定制网络结构，为嵌段共聚物在纳米技术中的应用提供了一个重要平台。
▲ Abstract：
Block copolymer self-assembly affords diverse nanostructures, spanning from spheres and cylinders to networks, offering meticulous control over properties and functionalities at the nanoscale. However, creating thermodynamically stable network structures with high packing frustration remains a challenge. In this study, we report a methodology to access diverse network structures such as gyroid, diamond, and primitive phases from diblock copolymers using end group and linker chemistry. The stability of the medial packing of polymer chain ends (plumber’s nightmare structure) over skeletal aggregation (gyroid) is attributed to the interplay between the strength of the end-end interactions and the initial shape of the curvature. Our study establishes an approach to develop tailored network structures from block copolymers, providing an important platform for using block copolymers in nanotechnology applications.
Dealuminated Beta zeolite reverses Ostwald ripening for durable copper nanoparticle catalysts
脱铝β沸石逆转奥斯特瓦尔德熟化助力持久铜纳米颗粒催化剂
▲ 作者：Lujie Liu, Jiaye Lu, Yahui Yang, Wolfgang Ruettinger, Xinhua Gao, Ming Wang, et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adj1962
▲ 摘要：
铜基纳米颗粒催化剂在工业上得到了广泛应用，但铜纳米颗粒在化学气氛中容易烧结成较大的铜粒子，有损催化剂性能。
研究组使用脱铝β沸石来负载铜纳米颗粒（Cu/β-deAl），并表明这些颗粒在200℃的甲醇蒸气中变小，直径从约5.6纳米减小至约2.4纳米，这与一般的烧结现象相反。研究发现了一个逆向熟化过程，即由甲醇激活的可迁移铜位点被硅烷醇“巢”捕获，巢中的铜物种可作为小纳米颗粒形成的新成核位点。
这一特性逆转了常规烧结过程，产生了可工业应用的负载铜纳米颗粒进行草酸二甲酯加氢的稳健催化剂。
▲ Abstract：
Copper nanoparticle–based catalysts have been extensively applied in industry, but the nanoparticles tend to sinter into larger ones in the chemical atmospheres, which is detrimental to catalyst performance. In this work, we used dealuminated Beta zeolite to support copper nanoparticles (Cu/Beta-deAl) and showed that these particles become smaller in methanol vapor at 200°C, decreasing from ~5.6 to ~2.4 nanometers in diameter, which is opposite to the general sintering phenomenon. A reverse ripening process was discovered, whereby migratable copper sites activated by methanol were trapped by silanol nests and the copper species in the nests acted as new nucleation sites for the formation of small nanoparticles. This feature reversed the general sintering channel, resulting in robust catalysts for dimethyl oxalate hydrogenation performed with supported copper nanoparticles for use in industry.
化学Chemistry
Direct propylene epoxidation via water activation over Pd-Pt electrocatalysts
通过水活化在Pd-Pt电催化剂上直接环氧化丙烯
▲ 作者：Minju Chung, Joseph H. Maalouf, Jason S. Adams, Chenyu Jiang, Yuriy Román-Leshkov & Karthish Manthiram
▲ 链接：
https://www.science.org/doi/10.1126/science.adh4355
▲ 摘要：
通过水氧化中间体直接电化学环氧化丙烯为现有涉及危险氯或过氧化物试剂的路线提供了一种可持续的替代策略。
研究组报道了一种氧化钯-铂合金催化剂（PdPtOx/C），在环境温度和压力、50 mA/cm2的电流下，丙烯环氧化的法拉第效率达到66±5%。将铂嵌入到氧化钯晶体结构中可稳定氧化铂物种，从而提高催化剂性能。反应动力学表明PdPtOx/C的环氧化反应通过金属结合过氧中间体的亲电攻击进行。
该研究证明了一种在无介质情况下，选择性地从水中电化学转移氧原子以进行不同氧化反应的有效策略。
▲ Abstract：
Direct electrochemical propylene epoxidation by means of water-oxidation intermediates presents a sustainable alternative to existing routes that involve hazardous chlorine or peroxide reagents. We report an oxidized palladium-platinum alloy catalyst (PdPtOx/C), which reaches a Faradaic efficiency of 66 ± 5% toward propylene epoxidation at 50 milliamperes per square centimeter at ambient temperature and pressure. Embedding platinum into the palladium oxide crystal structure stabilized oxidized platinum species, resulting in improved catalyst performance. The reaction kinetics suggest that epoxidation on PdPtOx/C proceeds through electrophilic attack by metal-bound peroxo intermediates. This work demonstrates an effective strategy for selective electrochemical oxygen-atom transfer from water, without mediators, for diverse oxygenation reactions.
Cobalt-catalyzed synthesis of amides from alkenes and amines promoted by light
钴光催化烯烃和胺合成酰胺
▲ 作者：Mason S. Faculak, Alexander M. Veatch & Erik J. Alexanian
▲ 链接：
https://www.science.org/doi/10.1126/science.adk2312
▲ 摘要：
烯烃和胺原料的催化偶联方法在合成化学中具有重要应用价值。烯烃和胺的直接羰基化偶联有望作为一种完美的原子经济性方法来合成酰胺，但通用策略仍不成熟。
研究组报道了在温和条件和光促低压下，未改性廉价羰基钴催化的烯烃氢氨基羰基化反应。反应后添加硅烷实现了顺序钴催化酰胺还原，构成了正式的烯烃氢氨甲基化。这些方法在烯烃和胺组分中表现出高化学选择性和高区域选择性的杰出范围，即使在没有溶剂的情况下也能有效进行。
通过羰基配体的光解作用形成氢钴以在温和条件下实现催化活性，这解决了催化领域长期存在的难题。
▲ Abstract：
Catalytic methods to couple alkene and amine feedstocks are valuable in synthetic chemistry. The direct carbonylative coupling of alkenes and amines holds promise as a perfectly atom-economical approach to amide synthesis, but general methods remain underdeveloped. Herein, we report an alkene hydroaminocarbonylation catalyzed by unmodified, inexpensive cobalt carbonyl under mild conditions and low pressure promoted by light. Silane addition after the reaction enables sequential cobalt-catalyzed amide reduction, constituting a formal alkene hydroaminomethylation. These methods exhibit exceptional scope across both alkene and amine components with high chemo- and regioselectivity and proceed efficiently even in the absence of solvent. The formation of a hydridocobalt through photodissociation of a carbonyl ligand is proposed to enable catalytic activity under mild conditions, which addresses a long-standing challenge in catalysis.
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