編譯 | 未玖
Science , 5 JAN 2024, VOL 383, ISSUE 6678
【科學】 2024年1月5日，第383卷，6678期
物理學 Physics
De Haas–van Alphen spectroscopy and magnetic breakdown in moiré graphene
莫爾石墨烯中德哈斯-範艾爾芬光譜學和磁擊穿
▲ 作者：Matan Bocarsly, Matan Uzan, Indranil Roy, Sameer Grover, Jiewen Xiao, Zhiyu Dong, et al.
▲ 連結：
https://www.science.org/doi/10.1126/science.adp499
▲ 摘要：
源自電子回旋軌域量子化的量子振蕩可用於對電子能帶和交互作用的靈敏診斷。
研究組報道了莫爾石墨烯中由德哈斯-範艾爾芬效應引起的熱力學磁化振蕩的奈米級成像。利用探針超導量子幹涉裝置（SQUID）在與六方氮化硼軸向對齊的伯納爾雙層石墨烯晶體中進行掃描，他們發現了在弱磁場下每電子振幅高達500波耳磁子的較大磁化震蕩，頻率低得出乎意料，並且對超晶格填充分數高度敏感。
這些振蕩使人們能夠重建復雜的能帶結構，揭示出由極小動量隙分開的多個重疊費米面的窄莫爾帶。研究組確定了顛覆教科書的昂薩格費米面和規則振蕩集，這標誌著由相幹磁擊穿引起的寬頻粒子-電洞疊加態的形成。
▲ 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.
材料科學 Materials Science
Supramolecular assembly of blue and green halide perovskites with near-unity photoluminescence
具有近100%光致發光的藍綠光鹵化物鈣鈦礦的超分子組裝
▲ 作者：Cheng Zhu, Jianbo Jin, Zhen Wang, Zhenpeng Xu, Maria C. Folgueras, Yuxin Jiang, et al.
▲ 連結：
https://www.science.org/doi/10.1126/science.adi4196
▲ 摘要：
金屬鹵化物離子八面體是鹵化物鈣鈦礦的光電單元，冠醚輔助的超分子組裝法可將各種離子八面體組裝為可調的對稱性結構。
研究組用鹵化鉿（Hf）和鹵化鋯（Zr）八面體簇的超分子組裝證明了近100%光致發光量子產率（PLQY）藍光和綠光發射。(18C6@K)2HfBr6粉末呈現近100% PLQY（96.2%）的藍光發射，(18C6@K)2ZrCl4Br2粉末呈現PLQY為82.7%的綠光發射。
這些高發射性粉末的特點是可在低溫溶液合成條件下簡易合成，在環境條件、溶液可加工的半導體油墨中保持高PLQY，可用於具有高空間分辨率的薄膜顯視器和發射性三維打印架構。
▲ 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
嵌段共聚物中熱動力穩定的「管道工噩夢」結構
▲ 作者：Hojun Lee, Sangwoo Kwon, Jaemin Min, Seon-Mi Jin, Jun Ho Hwang, Eunji Lee, et al.
▲ 連結：
https://www.science.org/doi/10.1126/science.adh0483
▲ 摘要：
嵌段共聚物自組裝提供了從球體、圓柱體到網路的各種奈米結構，在奈米尺度上對效能和功能進行了精細控制。然而，創造高堆積受挫、熱力學穩定的網路結構仍頗具挑戰。
研究組報道了一種利用端基和連線體化學從二嵌段共聚物中獲取不同網路結構（如螺旋相、金剛石相和原始相）的方法。聚合物鏈末端（「管道工噩夢」結構）中間堆積對於骨架聚集（螺旋相）的穩定性歸因於端-端交互作用的強度和曲率初始形狀之間的交互作用。
該研究實作了從嵌段共聚物中開發客製網路結構，為嵌段共聚物在奈米技術中的套用提供了一個重要平台。
▲ 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
脫鋁β沸石逆轉奧斯特瓦爾德熟化助力持久銅奈米顆粒催化劑
▲ 作者：Lujie Liu, Jiaye Lu, Yahui Yang, Wolfgang Ruettinger, Xinhua Gao, Ming Wang, et al.
▲ 連結：
https://www.science.org/doi/10.1126/science.adj1962
▲ 摘要：
銅基奈米顆粒催化劑在工業上得到了廣泛套用，但銅奈米顆粒在化學氣氛中容易燒結成較大的銅粒子，失真催化劑效能。
研究組使用脫鋁β沸石來負載銅奈米顆粒（Cu/β-deAl），並表明這些顆粒在200℃的甲醇蒸氣中變小，直徑從約5.6奈米減小至約2.4奈米，這與一般的燒結現象相反。研究發現了一個逆向熟化過程，即由甲醇啟用的可遷移銅位點被矽烷醇「巢」捕獲，巢中的銅物種可作為小奈米顆粒形成的新成核位點。
這一特性逆轉了常規燒結過程，產生了可工業套用的負載銅奈米顆粒進行草酸二甲酯加氫的穩健催化劑。
▲ 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.
化學 Chemistry
Direct propylene epoxidation via water activation over Pd-Pt electrocatalysts
透過水活化在Pd-Pt電催化劑上直接環氧化丙烯
▲ 作者：Minju Chung, Joseph H. Maalouf, Jason S. Adams, Chenyu Jiang, Yuriy Román-Leshkov & Karthish Manthiram
▲ 連結：
https://www.science.org/doi/10.1126/science.adp355
▲ 摘要：
透過水氧化中間體直接電化學環氧化丙烯為現有涉及危險氯或過氧化物試劑的路線提供了一種永續的替代策略。
研究組報道了一種氧化鈀-鉑合金催化劑（PdPtOx/C），在環境溫度和壓力、50 mA/cm2的電流下，丙烯環氧化的法拉第效率達到66±5%。將鉑嵌入到氧化鈀晶體結構中可穩定氧化鉑物種，從而提高催化劑效能。反應動力學表明PdPtOx/C的環氧化反應透過金屬結合過氧中間體的親電攻擊進行。
該研究證明了一種在無介質情況下，選擇性地從水中電化學轉移氧原子以進行不同氧化反應的有效策略。
▲ 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
鈷光催化烯烴和胺合成醯胺
▲ 作者：Mason S. Faculak, Alexander M. Veatch & Erik J. Alexanian
▲ 連結：
https://www.science.org/doi/10.1126/science.adk2312
▲ 摘要：
烯烴和胺原料的催化偶聯方法在合成化學中具有重要套用價值。烯烴和胺的直接羰基化偶聯有望作為一種完美的原子經濟性方法來合成醯胺，但通用策略仍不成熟。
研究組報道了在溫和條件和光促低壓下，未改性廉價羰基鈷催化的烯烴氫胺基羰基化反應。反應後添加矽烷實作了順序鈷催化醯胺還原，構成了正式的烯烴氫氨甲基化。這些方法在烯烴和胺組分中表現出高化學選擇性和高區域選擇性的傑出範圍，即使在沒有溶劑的情況下也能有效進行。
透過羰基配體的光解作用形成氫鈷以在溫和條件下實作催化活性，這解決了催化領域長期存在的難題。
▲ 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.
