Perovskites cover silicon textures Nat. Mater. (IF 39.737) Pub Date : 2018-06-11 Anita Ho-Baillie
Perovskites cover silicon textures Perovskites cover silicon textures, Published online: 11 June 2018; doi:10.1038/s41563-018-0122-5 A two-step deposition method has been developed that enables the conformal coating of textured surfaces with perovskite films. This allows the realization of perovskite/silicon tandem solar cells with increased short-circuit current density.
Therapeutic luminal coating of the intestine Nat. Mater. (IF 39.737) Pub Date : 2018-06-11 Yuhan Lee, Tara E. Deelman, Keyue Chen, Dawn S. Y. Lin, Ali Tavakkoli, Jeffrey M. Karp
The gastrointestinal tract is the site of most drug delivery and therapeutic interventions for the management and treatment of numerous diseases. However, selective access to its mucosa, especially in the small bowel, is challenging. Here we develop an orally administered gut-coating formulation that provides a transient coating of the bowel. Through a materials screening campaign, we identified a sucrose octasulfate aluminium complex and further engineered the pH-dependent material into a complex coacervate formulation linked via pH-independent electrostatic interaction, which allowed an effective transient physical coating on the gastrointestinal mucosa, independent of gastric acid exposure. We tested the therapeutic values of this technology in two settings. Oral administration of this gut-coating formulation modulated the nutrient contact with bowel mucosa, which lowered the glucose responses in rodent models indicating a potential therapeutic utility in diabetes. Furthermore, the formulation protected biological agents from gastric acid exposure and degradation, which enabled oral delivery to the small bowel mucosa.
Reversible adsorption of nitrogen dioxide within a robust porous metal–organic framework Nat. Mater. (IF 39.737) Pub Date : 2018-06-11 Xue Han, Harry G. W. Godfrey, Lydia Briggs, Andrew J. Davies, Yongqiang Cheng, Luke L. Daemen, Alena M. Sheveleva, Floriana Tuna, Eric J. L. McInnes, Junliang Sun, Christina Drathen, Michael W. George, Anibal J. Ramirez-Cuesta, K. Mark Thomas, Sihai Yang, Martin Schröder
Nitrogen dioxide (NO2) is a major air pollutant causing significant environmental1,2 and health problems3,4. We report reversible adsorption of NO2 in a robust metal–organic framework. Under ambient conditions, MFM-300(Al) exhibits a reversible NO2 isotherm uptake of 14.1 mmol g−1, and, more importantly, exceptional selective removal of low-concentration NO2 (5,000 to <1 ppm) from gas mixtures. Complementary experiments reveal five types of supramolecular interaction that cooperatively bind both NO2 and N2O4 molecules within MFM-300(Al). We find that the in situ equilibrium 2NO2 ↔ N2O4 within the pores is pressure-independent, whereas ex situ this equilibrium is an exemplary pressure-dependent first-order process. The coexistence of helical monomer–dimer chains of NO2 in MFM-300(Al) could provide a foundation for the fundamental understanding of the chemical properties of guest molecules within porous hosts. This work may pave the way for the development of future capture and conversion technologies.
Still plenty to explore Nat. Mater. (IF 39.737) Pub Date : 2018-06-11 Brian Gleeson
Still plenty to explore Still plenty to explore, Published online: 11 June 2018; doi:10.1038/s41563-018-0119-0 Advanced characterization and modelling techniques provide unique insights into oxidant transport processes in growing scales of high-temperature alloys and alloy design for improving their degradation resistance in harsh environments.
Homochiral porous nanosheets for enantiomer sieving Nat. Mater. (IF 39.737) Pub Date : 2018-06-11 Bo Sun, Yongju Kim, Yanqiu Wang, Huaxin Wang, Jehan Kim, Xin Liu, Myongsoo Lee
Protein pores are highly specific in binding to chiral substrates and in catalysing stereospecific reactions, because their active pockets are asymmetric and stereoselective1,2. Chiral binding materials from molecular-level pores with high specificity have not been achieved because of problems with pore deformation and blocking3. A promising solution is the self-assembly of single sheets where all pores are exposed to the environment, for example as metal–organic frameworks4, polymers5,6 or non-covalent aromatic networks7,8,9,10, but, typically, the pores are distant from the internal cavities with chirality. Here, we report the synthesis of homochiral porous nanosheets achieved by the 2D self-assembly of non-chiral macrocycles, with open/closed pore switching. Pore chirality is spontaneously induced by a twisted stack of dimeric macrocycles. The porous 2D structures can serve as enantiomer sieving membranes that exclusively capture a single enantiomer in a racemic mixture solution, with uptake capacity greater than 96%. Moreover, the entrapped guests inside the pores can be pumped out by pore closing triggered by external stimuli. This strategy could provide new opportunities for controlled molecule release, as well as for artificial cells.
Interplay of water and reactive elements in oxidation of alumina-forming alloys Nat. Mater. (IF 39.737) Pub Date : 2018-06-11 N. Mortazavi, C. Geers, M. Esmaily, V. Babic, M. Sattari, K. Lindgren, P. Malmberg, B. Jönsson, M. Halvarsson, J. E. Svensson, I. Panas, L. G. Johansson
High-temperature alloys are crucial to many important technologies that underpin our civilization. All these materials rely on forming an external oxide layer (scale) for corrosion protection. Despite decades of research on oxide scale growth, many open questions remain, including the crucial role of the so-called reactive elements and water. Here, we reveal the hitherto unknown interplay between reactive elements and water during alumina scale growth, causing a metastable ‘messy’ nano-structured alumina layer to form. We propose that reactive-element-decorated, hydroxylated interfaces between alumina nanograins enable water to access an inner cathode in the bottom of the scale, at odds with the established scale growth scenario. As evidence, hydride-nanodomains and reactive element/hydrogen (deuterium) co-variation are observed in the alumina scale. The defect-rich alumina subsequently recrystallizes to form a protective scale. First-principles modelling is also performed to validate the RE effect. Our findings open up promising avenues in oxidation research and suggest ways to improve alloy properties.
Re-entrant charge order in overdoped (Bi,Pb)2.12Sr1.88CuO6+δ outside the pseudogap regime Nat. Mater. (IF 39.737) Pub Date : 2018-06-11 Y. Y. Peng, R. Fumagalli, Y. Ding, M. Minola, S. Caprara, D. Betto, M. Bluschke, G. M. De Luca, K. Kummer, E. Lefrançois, M. Salluzzo, H. Suzuki, M. Le Tacon, X. J. Zhou, N. B. Brookes, B. Keimer, L. Braicovich, M. Grilli, G. Ghiringhelli
In the underdoped regime, the cuprate high-temperature superconductors exhibit a host of unusual collective phenomena, including unconventional spin and charge density modulations, Fermi surface reconstructions, and a pseudogap in various physical observables. Conversely, overdoped cuprates are generally regarded as conventional Fermi liquids possessing no collective electronic order. In partial contradiction to this widely held picture, we report resonant X-ray scattering measurements revealing incommensurate charge order reflections for overdoped (Bi,Pb)2.12Sr1.88CuO6+δ (Bi2201), with correlation lengths of 40–60 lattice units, that persist up to temperatures of at least 250 K. The value of the charge order wavevector decreases with doping, in line with the extrapolation of the trend previously observed in underdoped Bi2201. In overdoped materials, however, charge order coexists with a single, unreconstructed Fermi surface without nesting or pseudogap features. The discovery of re-entrant charge order in Bi2201 thus calls for investigations in other cuprate families and for a reconsideration of theories that posit an essential relationship between these phenomena.
Fully textured monolithic perovskite/silicon tandem solar cells with 25.2% power conversion efficiency Nat. Mater. (IF 39.737) Pub Date : 2018-06-11 Florent Sahli, Jérémie Werner, Brett A. Kamino, Matthias Bräuninger, Raphaël Monnard, Bertrand Paviet-Salomon, Loris Barraud, Laura Ding, Juan J. Diaz Leon, Davide Sacchetto, Gianluca Cattaneo, Matthieu Despeisse, Mathieu Boccard, Sylvain Nicolay, Quentin Jeangros, Bjoern Niesen, Christophe Ballif
Tandem devices combining perovskite and silicon solar cells are promising candidates to achieve power conversion efficiencies above 30% at reasonable costs. State-of-the-art monolithic two-terminal perovskite/silicon tandem devices have so far featured silicon bottom cells that are polished on their front side to be compatible with the perovskite fabrication process. This concession leads to higher potential production costs, higher reflection losses and non-ideal light trapping. To tackle this issue, we developed a top cell deposition process that achieves the conformal growth of multiple compounds with controlled optoelectronic properties directly on the micrometre-sized pyramids of textured monocrystalline silicon. Tandem devices featuring a silicon heterojunction cell and a nanocrystalline silicon recombination junction demonstrate a certified steady-state efficiency of 25.2%. Our optical design yields a current density of 19.5 mA cm−2 thanks to the silicon pyramidal texture and suggests a path for the realization of 30% monolithic perovskite/silicon tandem devices.
Reducing localization Nat. Mater. (IF 39.737) Pub Date : A. Alec Talin, François Léonard
Reducing localizationReducing localization, Published online: 04 June 2018; doi:10.1038/s41563-018-0103-8By inserting potassium into a 3D metal–organic framework band delocalization occurs, enabling mobilities and conductivities similar to organic polymers.
Electron delocalization and charge mobility as a function of reduction in a metal–organic framework Nat. Mater. (IF 39.737) Pub Date : Michael L. Aubrey, Brian M. Wiers, Sean C. Andrews, Tsuneaki Sakurai, Sebastian E. Reyes-Lillo, Samia M. Hamed, Chung-Jui Yu, Lucy E. Darago, Jarad A. Mason, Jin-Ook Baeg, Fernande Grandjean, Gary J. Long, Shu Seki, Jeffrey B. Neaton, Peidong Yang, Jeffrey R. Long
Electron delocalization and charge mobility as a function of reduction in a metal–organic frameworkElectron delocalization and charge mobility as a function of reduction in a metal–organic framework, Published online: 04 June 2018; doi:10.1038/s41563-018-0098-1A conducting metal–organic framework with charge delocalization by reductive potassium insertion is demonstrated. Integration into a field-effect transistor shows similar mobilities to semiconductors, with a mobility estimated to be at least 0.84 cm2 V–1 s–1.
Terahertz-light quantum tuning of a metastable emergent phase hidden by superconductivity Nat. Mater. (IF 39.737) Pub Date : 2018-06-04 X. Yang, C. Vaswani, C. Sundahl, M. Mootz, P. Gagel, L. Luo, J. H. Kang, P. P. Orth, I. E. Perakis, C. B. Eom, J. Wang
‘Sudden’ quantum quench and prethermalization have become a cross-cutting theme for discovering emergent states of matter1,2,3,4. Yet this remains challenging in electron matter5,6,7,8,9, especially superconductors10,11,12,13,14. The grand question of what is hidden underneath superconductivity (SC)15 appears universal, but poorly understood. Here we reveal a long-lived gapless quantum phase of prethermalized quasiparticles (QPs) after a single-cycle terahertz (THz) quench of a Nb3Sn SC gap. Its conductivity spectra is characterized by a sharp coherent peak and a vanishing scattering rate that decreases almost linearly towards zero frequency, which is most pronounced around the full depletion of the condensate and absent for a high-frequency pump. Above a critical pump threshold, such a QP phase with coherent transport and memory persists as an unusual prethermalization plateau, without relaxation to normal and SC thermal states for an order of magnitude longer than the QP recombination and thermalization times. Switching to this metastable ‘quantum QP fluid’ signals non-thermal quench of coupled SC and charge-density-wave (CDW)-like orders and hints quantum control beneath the SC.
Local immunomodulation with Fas ligand-engineered biomaterials achieves allogeneic islet graft acceptance Nat. Mater. (IF 39.737) Pub Date : 2018-06-04 Devon M. Headen, Kyle B. Woodward, María M. Coronel, Pradeep Shrestha, Jessica D. Weaver, Hong Zhao, Min Tan, Michael D. Hunckler, William S. Bowen, Christopher T. Johnson, Lonnie Shea, Esma S. Yolcu, Andrés J. García, Haval Shirwan
Islet transplantation is a promising therapy for type 1 diabetes. However, chronic immunosuppression to control rejection of allogeneic islets induces morbidities and impairs islet function. T effector cells are responsible for islet allograft rejection and express Fas death receptors following activation, becoming sensitive to Fas-mediated apoptosis. Here, we report that localized immunomodulation using microgels presenting an apoptotic form of the Fas ligand with streptavidin (SA-FasL) results in prolonged survival of allogeneic islet grafts in diabetic mice. A short course of rapamycin treatment boosted the immunomodulatory efficacy of SA-FasL microgels, resulting in acceptance and function of allografts over 200 days. Survivors generated normal systemic responses to donor antigens, implying immune privilege of the graft, and had increased CD4+CD25+FoxP3+ T regulatory cells in the graft and draining lymph nodes. Deletion of T regulatory cells resulted in acute rejection of established islet allografts. This localized immunomodulatory biomaterial-enabled approach may provide an alternative to chronic immunosuppression for clinical islet transplantation.
Electrifying model catalysts for understanding electrocatalytic reactions in liquid electrolytes Nat. Mater. (IF 39.737) Pub Date : 2018-06-04 Firas Faisal, Corinna Stumm, Manon Bertram, Fabian Waidhas, Yaroslava Lykhach, Serhiy Cherevko, Feifei Xiang, Maximilian Ammon, Mykhailo Vorokhta, Břetislav Šmíd, Tomáš Skála, Nataliya Tsud, Armin Neitzel, Klára Beranová, Kevin C. Prince, Simon Geiger, Olga Kasian, Tobias Wähler, Ralf Schuster, M. Alexander Schneider, Vladimír Matolín, Karl J. J. Mayrhofer, Olaf Brummel, Jörg Libuda
Electrocatalysis is at the heart of our future transition to a renewable energy system. Most energy storage and conversion technologies for renewables rely on electrocatalytic processes and, with increasing availability of cheap electrical energy from renewables, chemical production will witness electrification in the near future1,2,3. However, our fundamental understanding of electrocatalysis lags behind the field of classical heterogeneous catalysis that has been the dominating chemical technology for a long time. Here, we describe a new strategy to advance fundamental studies on electrocatalytic materials. We propose to ‘electrify’ complex oxide-based model catalysts made by surface science methods to explore electrocatalytic reactions in liquid electrolytes. We demonstrate the feasibility of this concept by transferring an atomically defined platinum/cobalt oxide model catalyst into the electrochemical environment while preserving its atomic surface structure. Using this approach, we explore particle size effects and identify hitherto unknown metal–support interactions that stabilize oxidized platinum at the nanoparticle interface. The metal–support interactions open a new synergistic reaction pathway that involves both metallic and oxidized platinum. Our results illustrate the potential of the concept, which makes available a systematic approach to build atomically defined model electrodes for fundamental electrocatalytic studies.
Author Correction: Room-temperature ductile inorganic semiconductor Nat. Mater. (IF 39.737) Pub Date : 2018-05-30 Xun Shi, Hongyi Chen, Feng Hao, Ruiheng Liu, Tuo Wang, Pengfei Qiu, Ulrich Burkhardt, Yuri Grin, Lidong Chen
Author Correction: Room-temperature ductile inorganic semiconductor Author Correction: Room-temperature ductile inorganic semiconductor, Published online: 30 May 2018; doi:10.1038/s41563-018-0111-8 Author Correction: Room-temperature ductile inorganic semiconductor
Significant Dzyaloshinskii–Moriya interaction at graphene–ferromagnet interfaces due to the Rashba effect Nat. Mater. (IF 39.737) Pub Date : 2018-05-28 Hongxin Yang, Gong Chen, Alexandre A. C. Cotta, Alpha T. N’Diaye, Sergey A. Nikolaev, Edmar A. Soares, Waldemar A. A. Macedo, Kai Liu, Andreas K. Schmid, Albert Fert, Mairbek Chshiev
The possibility of utilizing the rich spin-dependent properties of graphene has attracted much attention in the pursuit of spintronics advances. The promise of high-speed and low-energy-consumption devices motivates the search for layered structures that stabilize chiral spin textures such as topologically protected skyrmions. Here we demonstrate that chiral spin textures are induced at graphene/ferromagnetic metal interfaces. Graphene is a weak spin–orbit coupling material and is generally not expected to induce a sufficient Dzyaloshinskii–Moriya interaction to affect magnetic chirality. We demonstrate that indeed graphene does induce a type of Dzyaloshinskii–Moriya interaction due to the Rashba effect. First-principles calculations and experiments using spin-polarized electron microscopy show that this graphene-induced Dzyaloshinskii–Moriya interaction can have a similar magnitude to that at interfaces with heavy metals. This work paves a path towards two-dimensional-material-based spin–orbitronics.
Spin colossal magnetoresistance in an antiferromagnetic insulator Nat. Mater. (IF 39.737) Pub Date : 2018-05-28 Zhiyong Qiu, Dazhi Hou, Joseph Barker, Kei Yamamoto, Olena Gomonay, Eiji Saitoh
Colossal magnetoresistance (CMR) refers to a large change in electrical conductivity induced by a magnetic field in the vicinity of a metal–insulator transition and has inspired extensive studies for decades1,2. Here we demonstrate an analogous spin effect near the Néel temperature, TN = 296 K, of the antiferromagnetic insulator Cr2O3. Using a yttrium iron garnet YIG/Cr2O3/Pt trilayer, we injected a spin current from the YIG into the Cr2O3 layer and collected, via the inverse spin Hall effect, the spin signal transmitted into the heavy metal Pt. We observed a two orders of magnitude difference in the transmitted spin current within 14 K of the Néel temperature. This transition between spin conducting and non-conducting states was also modulated by a magnetic field in isothermal conditions. This effect, which we term spin colossal magnetoresistance (SCMR), has the potential to simplify the design of fundamental spintronics components, for instance, by enabling the realization of spin-current switches or spin-current-based memories.
Self-assembled highly ordered acid layers in precisely sulfonated polyethylene produce efficient proton transport Nat. Mater. (IF 39.737) Pub Date : 2018-05-28 Edward B. Trigg, Taylor W. Gaines, Manuel Maréchal, Demi E. Moed, Patrice Rannou, Kenneth B. Wagener, Mark J. Stevens, Karen I. Winey
Recent advances in polymer synthesis have allowed remarkable control over chain microstructure and conformation. Capitalizing on such developments, here we create well-controlled chain folding in sulfonated polyethylene, leading to highly uniform hydrated acid layers of subnanometre thickness with high proton conductivity. The linear polyethylene contains sulfonic acid groups pendant to precisely every twenty-first carbon atom that induce tight chain folds to form the hydrated layers, while the methylene segments crystallize. The proton conductivity is on par with Nafion 117, the benchmark for fuel cell membranes. We demonstrate that well-controlled hairpin chain folding can be utilized for proton conductivity within a crystalline polymer structure, and we project that this structure could be adapted for ion transport. This layered polyethylene-based structure is an innovative and versatile design paradigm for functional polymer membranes, opening doors to efficient and selective transport of other ions and small molecules on appropriate selection of functional groups.
Holstein polaron in a valley-degenerate two-dimensional semiconductor Nat. Mater. (IF 39.737) Pub Date : 2018-05-28 Mingu Kang, Sung Won Jung, Woo Jong Shin, Yeongsup Sohn, Sae Hee Ryu, Timur K. Kim, Moritz Hoesch, Keun Su Kim
Two-dimensional (2D) crystals have emerged as a class of materials with tunable carrier density1. Carrier doping to 2D semiconductors can be used to modulate many-body interactions2 and to explore novel composite particles. The Holstein polaron is a small composite particle of an electron that carries a cloud of self-induced lattice deformation (or phonons)3,4,5, which has been proposed to play a key role in high-temperature superconductivity6 and carrier mobility in devices7. Here we report the discovery of Holstein polarons in a surface-doped layered semiconductor, MoS2, in which a puzzling 2D superconducting dome with the critical temperature of 12 K was found recently8,9,10,11. Using a high-resolution band mapping of charge carriers, we found strong band renormalizations collectively identified as a hitherto unobserved spectral function of Holstein polarons12,13,14,15,16,17,18. The short-range nature of electron–phonon (e–ph) coupling in MoS2 can be explained by its valley degeneracy, which enables strong intervalley coupling mediated by acoustic phonons. The coupling strength is found to increase gradually along the superconducting dome up to the intermediate regime, which suggests a bipolaronic pairing in the 2D superconductivity.
Rejuvenating zinc batteries Nat. Mater. (IF 39.737) Pub Date : 2018-05-23 Enyuan Hu, Xiao-Qing Yang
Rejuvenating zinc batteries Rejuvenating zinc batteries, Published online: 23 May 2018; doi:10.1038/s41563-018-0090-9 By using high-concentration salt in electrolyte, water is replaced in the zinc solvation-sheath and a zinc anode is developed with high reversibility and stability
Tailor-made currents Nat. Mater. (IF 39.737) Pub Date : 2018-05-23 Frank Freimuth
Tailor-made currents Tailor-made currents, Published online: 23 May 2018; doi:10.1038/s41563-018-0086-5 Spin currents in magnetic trilayers exhibit an unexpected spin polarization that facilitates current-induced switching of magnetization.
Dendritic cells in cancer immunotherapy Nat. Mater. (IF 39.737) Pub Date : 2018-05-23 Camille M. Le Gall, Jorieke Weiden, Loek J. Eggermont, Carl G. Figdor
Dendritic cells in cancer immunotherapy Dendritic cells in cancer immunotherapy, Published online: 23 May 2018; doi:10.1038/s41563-018-0093-6 Camille M. Le Gall, Jorieke Weiden, Loek J. Eggermont and Carl G. Figdor provide an overview of immunotherapeutics for cancer treatment that harness dendritic cells, their challenges in clinical use, and approaches employed to enhance their recruitment and activation to promote effective anti-tumour immunity.
Material aid for vaccines Nat. Mater. (IF 39.737) Pub Date : 2018-05-23 Darrell Irvine
Material aid for vaccines Material aid for vaccines, Published online: 23 May 2018; doi:10.1038/s41563-018-0089-2 Darrell Irvine provides an overview of the recent advances in materials science that have enabled the use of innovative natural and synthetic compounds in vaccine development capable of regulating the potency and safety of new vaccines progressing towards the clinic.
Adoptive T cell cancer therapy Nat. Mater. (IF 39.737) Pub Date : 2018-05-23 Karine N. Dzhandzhugazyan, Per Guldberg, Alexei F. Kirkin
Adoptive T cell cancer therapy Adoptive T cell cancer therapy, Published online: 23 May 2018; doi:10.1038/s41563-018-0094-5 Tumour heterogeneity and off-target toxicity are current challenges of cancer immunotherapy. Karine Dzhandzhugazyan, Per Guldberg and Alexei Kirkin discuss how epigenetic induction of tumour antigens in antigen-presenting cells may form the basis for multi-target therapies.
Cells and materials in immunotherapy Nat. Mater. (IF 39.737) Pub Date : 2018-05-23
Cells and materials in immunotherapy Cells and materials in immunotherapy, Published online: 23 May 2018; doi:10.1038/s41563-018-0102-9 As the interaction of the immune system with the tumour microenvironment becomes increasingly understood, more evidence indicates how immunotherapy can be employed to better eliminate cancers.
Dual-function injectable angiogenic biomaterial for the repair of brain tissue following stroke Nat. Mater. (IF 39.737) Pub Date : 2018-05-21 Lina R. Nih, Shiva Gojgini, S. Thomas Carmichael, Tatiana Segura
Stroke is the primary cause of disability due to the brain's limited ability to regenerate damaged tissue. After stroke, an increased inflammatory and immune response coupled with severely limited angiogenesis and neuronal growth results in a stroke cavity devoid of normal brain tissue. In the adult, therapeutic angiogenic materials have been used to repair ischaemic tissues through the formation of vascular networks. However, whether a therapeutic angiogenic material can regenerate brain tissue and promote neural repair is poorly understood. Here we show that the delivery of an engineered immune-modulating angiogenic biomaterial directly to the stroke cavity promotes tissue formation de novo, and results in axonal networks along thee generated blood vessels. This regenerated tissue produces functional recovery through the established axonal networks. Thus, this biomaterials approach generates a vascularized network of regenerated functional neuronal connections within previously dead tissue and lays the groundwork for the use of angiogenic materials to repair other neurologically diseased tissues.
Designing natural and synthetic immune tissues Nat. Mater. (IF 39.737) Pub Date : 2018-05-21 Emily A. Gosselin, Haleigh B. Eppler, Jonathan S. Bromberg, Christopher M. Jewell
Vaccines and immunotherapies have provided enormous improvements for public health, but there are fundamental disconnects between where most studies are performed—in cell culture and animal models—and the ultimate application in humans. Engineering immune tissues and organs, such as bone marrow, thymus, lymph nodes and spleen, could be instrumental in overcoming these hurdles. Fundamentally, designed immune tissues could serve as in vitro tools to more accurately study human immune function and disease, while immune tissues engineered for implantation as next-generation vaccines or immunotherapies could enable direct, on-demand control over generation and regulation of immune function. In this Review, we discuss recent interdisciplinary strategies that are merging materials science and immunology to create engineered immune tissues in vitro and in vivo. We also highlight the hurdles facing these approaches and the need for comparison to existing clinical options, relevant animal models, and other emerging technologies.
An autonomously electrically self-healing liquid metal–elastomer composite for robust soft-matter robotics and electronics Nat. Mater. (IF 39.737) Pub Date : 2018-05-21 Eric J. Markvicka, Michael D. Bartlett, Xiaonan Huang, Carmel Majidi
Large-area stretchable electronics are critical for progress in wearable computing, soft robotics and inflatable structures. Recent efforts have focused on engineering electronics from soft materials—elastomers, polyelectrolyte gels and liquid metal. While these materials enable elastic compliance and deformability, they are vulnerable to tearing, puncture and other mechanical damage modes that cause electrical failure. Here, we introduce a material architecture for soft and highly deformable circuit interconnects that are electromechanically stable under typical loading conditions, while exhibiting uncompromising resilience to mechanical damage. The material is composed of liquid metal droplets suspended in a soft elastomer; when damaged, the droplets rupture to form new connections with neighbours and re-route electrical signals without interruption. Since self-healing occurs spontaneously, these materials do not require manual repair or external heat. We demonstrate this unprecedented electronic robustness in a self-repairing digital counter and self-healing soft robotic quadruped that continue to function after significant damage.
Mechanics-guided embryonic patterning of neuroectoderm tissue from human pluripotent stem cells Nat. Mater. (IF 39.737) Pub Date : 2018-05-21 Xufeng Xue, Yubing Sun, Agnes M. Resto-Irizarry, Ye Yuan, Koh Meng Aw Yong, Yi Zheng, Shinuo Weng, Yue Shao, Yimin Chai, Lorenz Studer, Jianping Fu
Classic embryological studies have successfully applied genetics and cell biology principles to understand embryonic development. However, it remains unresolved how mechanics, as an integral driver of development, is involved in controlling tissue-scale cell fate patterning. Here we report a micropatterned human pluripotent stem (hPS)-cell-based neuroectoderm developmental model, in which pre-patterned geometrical confinement induces emergent patterning of neuroepithelial and neural plate border cells, mimicking neuroectoderm regionalization during early neurulation in vivo. In this hPS-cell-based neuroectoderm patterning model, two tissue-scale morphogenetic signals—cell shape and cytoskeletal contractile force—instruct neuroepithelial/neural plate border patterning via BMP-SMAD signalling. We further show that ectopic mechanical activation and exogenous BMP signalling modulation are sufficient to perturb neuroepithelial/neural plate border patterning. This study provides a useful microengineered, hPS-cell-based model with which to understand the biomechanical principles that guide neuroectoderm patterning and hence to study neural development and disease.
The role of metal/oxide interfaces for long-range metal particle activation during CO oxidation Nat. Mater. (IF 39.737) Pub Date : 2018-05-14 Yuri Suchorski, Sergey M. Kozlov, Ivan Bespalov, Martin Datler, Diana Vogel, Zuzana Budinska, Konstantin M. Neyman, Günther Rupprechter
The role of metal/oxide interfaces for long-range metal particle activation during CO oxidation The role of metal/oxide interfaces for long-range metal particle activation during CO oxidation, Published online: 14 May 2018; doi:10.1038/s41563-018-0080-y Electron microscopy and modelling are used to study CO oxidation on oxide-supported Pd. The perimeter of the metal/oxide interface is shown to affect CO tolerance of the entire particle, demonstrating a long-range effect over micrometre length scales.
Electron–phonon interaction in efficient perovskite blue emitters Nat. Mater. (IF 39.737) Pub Date : 2018-05-14 Xiwen Gong, Oleksandr Voznyy, Ankit Jain, Wenjia Liu, Randy Sabatini, Zachary Piontkowski, Grant Walters, Golam Bappi, Sergiy Nokhrin, Oleksandr Bushuyev, Mingjian Yuan, Riccardo Comin, David McCamant, Shana O. Kelley, Edward H. Sargent
Low-dimensional perovskites have—in view of their high radiative recombination rates—shown great promise in achieving high luminescence brightness and colour saturation. Here we investigate the effect of electron–phonon interactions on the luminescence of single crystals of two-dimensional perovskites, showing that reducing these interactions can lead to bright blue emission in two-dimensional perovskites. Resonance Raman spectra and deformation potential analysis show that strong electron–phonon interactions result in fast non-radiative decay, and that this lowers the photoluminescence quantum yield (PLQY). Neutron scattering, solid-state NMR measurements of spin–lattice relaxation, density functional theory simulations and experimental atomic displacement measurements reveal that molecular motion is slowest, and rigidity greatest, in the brightest emitter. By varying the molecular configuration of the ligands, we show that a PLQY up to 79% and linewidth of 20 nm can be reached by controlling crystal rigidity and electron–phonon interactions. Designing crystal structures with electron–phonon interactions in mind offers a previously underexplored avenue to improve optoelectronic materials' performance.
Materials challenges for the Starshot lightsail Nat. Mater. (IF 39.737) Pub Date : 2018-05-07 Harry A. Atwater, Artur R. Davoyan, Ognjen Ilic, Deep Jariwala, Michelle C. Sherrott, Cora M. Went, William S. Whitney, Joeson Wong
Materials challenges for the Starshot lightsail Materials challenges for the Starshot lightsail, Published online: 07 May 2018; doi:10.1038/s41563-018-0075-8 This Perspective explores the optical, mechanical and thermal properties required to successfully design an ultralight spacecraft that can reach Proxima Centauri b, which is the goal of the Starshot Breakthrough Initiative.
Atomic origins of water-vapour-promoted alloy oxidation Nat. Mater. (IF 39.737) Pub Date : 2018-05-07 Langli Luo, Mao Su, Pengfei Yan, Lianfeng Zou, Daniel K. Schreiber, Donald R. Baer, Zihua Zhu, Guangwen Zhou, Yanting Wang, Stephen M. Bruemmer, Zhijie Xu, Chongmin Wang
The presence of water vapour, intentional or unavoidable, is crucial to many materials applications, such as in steam generators, turbine engines, fuel cells, catalysts and corrosion1,2,3,4. Phenomenologically, water vapour has been noted to accelerate oxidation of metals and alloys5,6. However, the atomistic mechanisms behind such oxidation remain elusive. Through direct in situ atomic-scale transmission electron microscopy observations and density functional theory calculations, we reveal that water-vapour-enhanced oxidation of a nickel–chromium alloy is associated with proton-dissolution-promoted formation, migration, and clustering of both cation and anion vacancies. Protons derived from water dissociation can occupy interstitial positions in the oxide lattice, consequently lowering vacancy formation energy and decreasing the diffusion barrier of both cations and anions, which leads to enhanced oxidation in moist environments at elevated temperatures. This work provides insights into water-vapour-enhanced alloy oxidation and has significant implications in other material and chemical processes involving water vapour, such as corrosion, heterogeneous catalysis and ionic conduction.
An unusual continuous paramagnetic-limited superconducting phase transition in 2D NbSe 2 Nat. Mater. (IF 39.737) Pub Date : 2018-04-30 Egon Sohn, Xiaoxiang Xi, Wen-Yu He, Shengwei Jiang, Zefang Wang, Kaifei Kang, Ju-Hyun Park, Helmuth Berger, László Forró, Kam Tuen Law, Jie Shan, Kin Fai Mak
Time reversal and spatial inversion are two key symmetries for conventional Bardeen–Cooper–Schrieffer (BCS) superconductivity1. Breaking inversion symmetry can lead to mixed-parity Cooper pairing and unconventional superconducting properties1,2,3,4,5. Two-dimensional (2D) NbSe2 has emerged as a new non-centrosymmetric superconductor with the unique out-of-plane or Ising spin–orbit coupling (SOC)6,7,8,9. Here we report the observation of an unusual continuous paramagnetic-limited superconductor–normal metal transition in 2D NbSe2. Using tunelling spectroscopy under high in-plane magnetic fields, we observe a continuous closing of the superconducting gap at the upper critical field at low temperatures, in stark contrast to the abrupt first-order transition observed in BCS thin-film superconductors10,11,12. The paramagnetic-limited continuous transition arises from a large spin susceptibility of the superconducting phase due to the Ising SOC. The result is further supported by self-consistent mean-field calculations based on the ab initio band structure of 2D NbSe2. Our findings establish 2D NbSe2 as a promising platform to explore novel spin-dependent superconducting phenomena and device concepts1, such as equal-spin Andreev reflection13 and topological superconductivity14,15,16.
Motorizing fibres with geometric zero-energy modes Nat. Mater. (IF 39.737) Pub Date : 2018-04-30 Arthur Baumann, Antoni Sánchez-Ferrer, Leandro Jacomine, Philippe Martinoty, Vincent Le Houerou, Falko Ziebert, Igor M. Kulić
Responsive materials1,2,3 have been used to generate structures with built-in complex geometries4,5,6, linear actuators7,8,9 and microswimmers10,11,12. These results suggest that complex, fully functional machines composed solely from shape-changing materials might be possible13. Nonetheless, to accomplish rotary motion in these materials still relies on the classical wheel and axle motifs. Here we explore geometric zero-energy modes to elicit rotary motion in elastic materials in the absence of a rigid wheel travelling around an axle. We show that prestrained polymer fibres closed into rings exhibit self-actuation and continuous motion when placed between two heat baths due to elastic deformations that arise from rotational-symmetry breaking around the rod's axis. Our findings illustrate a simple but robust model to create active motion in mechanically prestrained objects.
The influence of the Rashba effect Nat. Mater. (IF 39.737) Pub Date : 2018-04-23 Samuel D. Stranks, Paulina Plochocka
The influence of the Rashba effect The influence of the Rashba effect, Published online: 23 April 2018; doi:10.1038/s41563-018-0067-8 Heavy atoms and crystal or inversion symmetry breaking may promote Rashba effects in halide perovskites. Sam Stranks and Paulina Plochocka propose experiments to assess the existence of these effects and their implications on the photophysics of perovskites.
Gas vesicles as collapsible MRI contrast agents Nat. Mater. (IF 39.737) Pub Date : 2018-04-23 Jeff W. M. Bulte
Gas vesicles as collapsible MRI contrast agents Gas vesicles as collapsible MRI contrast agents, Published online: 23 April 2018; doi:10.1038/s41563-018-0073-x Microbial gas vesicles have been developed for use as MRI contrast agents whose contrast can be inactivated by applying ultrasound waves to collapse the vesicles.
At the flick of a switch Nat. Mater. (IF 39.737) Pub Date : 2018-04-23 Ajit Srivastava
At the flick of a switch At the flick of a switch, Published online: 23 April 2018; doi:10.1038/s41563-018-0064-y Voltage control of recently discovered two-dimensional magnets has been demonstrated, highlighting their potential for low-power data storage.
Present status and future prospects of perovskite photovoltaics Nat. Mater. (IF 39.737) Pub Date : 2018-04-23 Henry J. Snaith
Present status and future prospects of perovskite photovoltaics Present status and future prospects of perovskite photovoltaics, Published online: 23 April 2018; doi:10.1038/s41563-018-0071-z Solar cells based on metal halide perovskites continue to approach their theoretical performance limits thanks to worldwide research efforts. Mastering the materials properties and addressing stability may allow this technology to bring profound transformations to the electric power generation industry.
Ferroelectric large polarons Nat. Mater. (IF 39.737) Pub Date : 2018-04-23 Kiyoshi Miyata, X.-Y. Zhu
Ferroelectric large polarons Ferroelectric large polarons, Published online: 23 April 2018; doi:10.1038/s41563-018-0068-7 Kiyoshi Miyata and X.-Y. Zhu analyse the ferroelectric-like dielectric response of lead halide perovskites in the terahertz region and discuss the potential role of polar nanodomains in accounting for the defect tolerance and low recombination rates of these materials.
Vapour–liquid–solid growth of monolayer MoS2 nanoribbons Nat. Mater. (IF 39.737) Pub Date : 2018-04-23 Shisheng Li, Yung-Chang Lin, Wen Zhao, Jing Wu, Zhuo Wang, Zehua Hu, Youde Shen, Dai-Ming Tang, Junyong Wang, Qi Zhang, Hai Zhu, Leiqiang Chu, Weijie Zhao, Chang Liu, Zhipei Sun, Takaaki Taniguchi, Minoru Osada, Wei Chen, Qing-Hua Xu, Andrew Thye Shen Wee, Kazu Suenaga, Feng Ding, Goki Eda
Chemical vapour deposition of two-dimensional materials typically involves the conversion of vapour precursors to solid products in a vapour–solid–solid mode. Here, we report the vapour–liquid–solid growth of monolayer MoS2, yielding highly crystalline ribbons with a width of few tens to thousands of nanometres. This vapour–liquid–solid growth is triggered by the reaction between MoO3 and NaCl, which results in the formation of molten Na–Mo–O droplets. These droplets mediate the growth of MoS2 ribbons in the ‘crawling mode’ when saturated with sulfur. The locally well-defined orientations of the ribbons reveal the regular horizontal motion of the droplets during growth. Using atomic-resolution scanning transmission electron microscopy and second harmonic generation microscopy, we show that the ribbons are grown homoepitaxially on monolayer MoS2 with predominantly 2H- or 3R-type stacking. Our findings highlight the prospects for the controlled growth of atomically thin nanostructure arrays for nanoelectronic devices and the development of unique mixed-dimensional structures.
Highly reversible zinc metal anode for aqueous batteries Nat. Mater. (IF 39.737) Pub Date : 2018-04-16 Fei Wang, Oleg Borodin, Tao Gao, Xiulin Fan, Wei Sun, Fudong Han, Antonio Faraone, Joseph A Dura, Kang Xu, Chunsheng Wang
Metallic zinc (Zn) has been regarded as an ideal anode material for aqueous batteries because of its high theoretical capacity (820 mA h g–1), low potential (−0.762 V versus the standard hydrogen electrode), high abundance, low toxicity and intrinsic safety. However, aqueous Zn chemistry persistently suffers from irreversibility issues, as exemplified by its low coulombic efficiency (CE) and dendrite growth during plating/ stripping, and sustained water consumption. In this work, we demonstrate that an aqueous electrolyte based on Zn and lithium salts at high concentrations is a very effective way to address these issues. This unique electrolyte not only enables dendrite-free Zn plating/stripping at nearly 100% CE, but also retains water in the open atmosphere, which makes hermetic cell configurations optional. These merits bring unprecedented flexibility and reversibility to Zn batteries using either LiMn2O4 or O2 cathodes—the former deliver 180 W h kg–1 while retaining 80% capacity for >4,000 cycles, and the latter deliver 300 W h kg–1 (1,000 W h kg–1 based on the cathode) for >200 cycles.
Enhanced spin pumping into superconductors provides evidence for superconducting pure spin currents Nat. Mater. (IF 39.737) Pub Date : 2018-04-16 Kun-Rok Jeon, Chiara Ciccarelli, Andrew J. Ferguson, Hidekazu Kurebayashi, Lesley F. Cohen, Xavier Montiel, Matthias Eschrig, Jason W. A. Robinson, Mark G. Blamire
Unlike conventional spin-singlet Cooper pairs, spin-triplet pairs can carry spin1,2. Triplet supercurrents were discovered in Josephson junctions with metallic ferromagnet spacers, where spin transport can occur only within the ferromagnet and in conjunction with a charge current. Ferromagnetic resonance injects a pure spin current from a precessing ferromagnet into adjacent non-magnetic materials3,4. For spin-singlet pairing, the ferromagnetic resonance spin pumping efficiency decreases below the critical temperature (Tc) of a coupled superconductor5,6. Here we present ferromagnetic resonance experiments in which spin sink layers with strong spin–orbit coupling are added to the superconductor. Our results show that the induced spin currents, rather than being suppressed, are substantially larger in the superconducting state compared with the normal state; although further work is required to establish the details of the spin transport process, we show that this cannot be mediated by quasiparticles and is most likely a triplet pure spin supercurrent.
Hole trap formation in polymer light-emitting diodes under current stress Nat. Mater. (IF 39.737) Pub Date : 2018-04-16 Quan Niu, Roland Rohloff, Gert-Jan A. H. Wetzelaer, Paul W. M. Blom, N. Irina Crăciun
Polymer light-emitting diodes (PLEDs) are attractive for use in large-area displays and lighting panels, but their limited stability under current stress impedes commercialization. In spite of large efforts over the last two decades a fundamental understanding of the degradation mechanisms has not been accomplished. Here we demonstrate that the voltage drift of a PLED driven at constant current is caused by the formation of hole traps, which leads to additional non-radiative recombination between free electrons and trapped holes. The observed trap formation rate is consistent with exciton-free hole interactions as the main mechanism behind PLED degradation, enabling us to unify the degradation behaviour of various poly(p-phenylene) derivatives. The knowledge that hole trap formation is the cause of PLED degradation means that we can suppress the negative effect of hole traps on voltage and efficiency by blending the light-emitting polymer with a large-bandgap semiconductor. Owing to trap-dilution these blended PLEDs show unprecedented stability.
Pyroelectric energy conversion with large energy and power density in relaxor ferroelectric thin films Nat. Mater. (IF 39.737) Pub Date : 2018-04-16 Shishir Pandya, Joshua Wilbur, Jieun Kim, Ran Gao, Arvind Dasgupta, Chris Dames, Lane W. Martin
The need for efficient energy utilization is driving research into ways to harvest ubiquitous waste heat. Here, we explore pyroelectric energy conversion from low-grade thermal sources that exploits strong field- and temperature-induced polarization susceptibilities in the relaxor ferroelectric 0.68Pb(Mg1/3Nb2/3)O3–0.32PbTiO3. Electric-field-driven enhancement of the pyroelectric response (as large as −550 μC m−2 K−1) and suppression of the dielectric response (by 72%) yield substantial figures of merit for pyroelectric energy conversion. Field- and temperature-dependent pyroelectric measurements highlight the role of polarization rotation and field-induced polarization in mediating these effects. Solid-state, thin-film devices that convert low-grade heat into electrical energy are demonstrated using pyroelectric Ericsson cycles, and optimized to yield maximum energy density, power density and efficiency of 1.06 J cm−3, 526 W cm−3 and 19% of Carnot, respectively; the highest values reported to date and equivalent to the performance of a thermoelectric with an effective ZT ≈ 1.16 for a temperature change of 10 K. Our findings suggest that pyroelectric devices may be competitive with thermoelectric devices for low-grade thermal harvesting.
More power to pyroelectrics Nat. Mater. (IF 39.737) Pub Date : 2018-04-16 Joseph P. Feser, Jayakanth Ravichandran
More power to pyroelectrics More power to pyroelectrics, Published online: 16 April 2018; doi:10.1038/s41563-018-0065-x Using a thin-film geometry and electric-field-driven enhancement of pyroelectric response, a relaxor ferroelectric is shown to display superior power densities for thermal harvesting.
Room-temperature ductile inorganic semiconductor Nat. Mater. (IF 39.737) Pub Date : 2018-04-09 Xun Shi, Hongyi Chen, Feng Hao, Ruiheng Liu, Tuo Wang, Pengfei Qiu, Ulrich Burkhardt, Yuri Grin, Lidong Chen
Ductility is common in metals and metal-based alloys, but is rarely observed in inorganic semiconductors and ceramic insulators. In particular, room-temperature ductile inorganic semiconductors were not known until now. Here, we report an inorganic α-Ag2S semiconductor that exhibits extraordinary metal-like ductility with high plastic deformation strains at room temperature. Analysis of the chemical bonding reveals systems of planes with relatively weak atomic interactions in the crystal structure. In combination with irregularly distributed silver–silver and sulfur–silver bonds due to the silver diffusion, they suppress the cleavage of the material, and thus result in unprecedented ductility. This work opens up the possibility of searching for ductile inorganic semiconductors/ceramics for flexible electronic devices.
Large local lattice expansion in graphene adlayers grown on copper Nat. Mater. (IF 39.737) Pub Date : 2018-04-09 Chaoyu Chen, José Avila, Hakim Arezki, Van Luan Nguyen, Jiahong Shen, Marcin Mucha-Kruczyński, Fei Yao, Mohamed Boutchich, Yue Chen, Young Hee Lee, Maria C. Asensio
Variations of the lattice parameter can significantly change the properties of a material, and, in particular, its electronic behaviour. In the case of graphene, however, variations of the lattice constant with respect to graphite have been limited to less than 2.5% due to its well-established high in-plane stiffness. Here, through systematic electronic and lattice structure studies, we report regions where the lattice constant of graphene monolayers grown on copper by chemical vapour deposition increases up to ~7.5% of its relaxed value. Density functional theory calculations confirm that this expanded phase is energetically metastable and driven by the enhanced interaction between the substrate and the graphene adlayer. We also prove that this phase possesses distinctive chemical and electronic properties. The inherent phase complexity of graphene grown on copper foils revealed in this study may inspire the investigation of possible metastable phases in other seemingly simple heterostructure systems.
Electrostrain in excess of 1% in polycrystalline piezoelectrics Nat. Mater. (IF 39.737) Pub Date : 2018-04-09 Bastola Narayan, Jaskaran Singh Malhotra, Rishikesh Pandey, Krishna Yaddanapudi, Pavan Nukala, Brahim Dkhil, Anatoliy Senyshyn, Rajeev Ranjan
Piezoelectric actuators transform electrical energy into mechanical energy, and because of their compactness, quick response time and accurate displacement, they are sought after in many applications. Polycrystalline piezoelectric ceramics are technologically more appealing than single crystals due to their simpler and less expensive processing, but have yet to display electrostrain values that exceed 1%. Here we report a material design strategy wherein the efficient switching of ferroelectric–ferroelastic domains by an electric field is exploited to achieve a high electrostrain value of 1.3% in a pseudo-ternary ferroelectric alloy system, BiFeO3–PbTiO3–LaFeO3. Detailed structural investigations reveal that this electrostrain is associated with a combination of several factors: a large spontaneous lattice strain of the piezoelectric phase, domain miniaturization, a low-symmetry ferroelectric phase and a very large reverse switching of the non-180° domains. This insight for the design of a new class of polycrystalline piezoceramics with high electrostrains may be useful to develop alternatives to costly single-crystal actuators.
Deformable inorganic semiconductor Nat. Mater. (IF 39.737) Pub Date : 2018-04-09 Dae-Hyeong Kim, Gi Doo Cha
Deformable inorganic semiconductor Deformable inorganic semiconductor, Published online: 09 April 2018; doi:10.1038/s41563-018-0066-9 Unlike conventional inorganic semiconductors, which are typically brittle, α-Ag2S exhibits room-temperature ductility with favourable electrical properties, offering promise for use in high-performance flexible and stretchable devices.
Collapse of superconductivity in cuprates via ultrafast quenching of phase coherence Nat. Mater. (IF 39.737) Pub Date : 2018-04-02 F. Boschini, E. H. da Silva Neto, E. Razzoli, M. Zonno, S. Peli, R. P. Day, M. Michiardi, M. Schneider, B. Zwartsenberg, P. Nigge, R. D. Zhong, J. Schneeloch, G. D. Gu, S. Zhdanovich, A. K. Mills, G. Levy, D. J. Jones, C. Giannetti, A. Damascelli
The possibility of driving phase transitions in low-density condensates through the loss of phase coherence alone has far-reaching implications for the study of quantum phases of matter. This has inspired the development of tools to control and explore the collective properties of condensate phases via phase fluctuations. Electrically gated oxide interfaces1,2, ultracold Fermi atoms3,4 and cuprate superconductors5,6, which are characterized by an intrinsically small phase stiffness, are paradigmatic examples where these tools are having a dramatic impact. Here we use light pulses shorter than the internal thermalization time to drive and probe the phase fragility of the Bi2Sr2CaCu2O8+δ cuprate superconductor, completely melting the superconducting condensate without affecting the pairing strength. The resulting ultrafast dynamics of phase fluctuations and charge excitations are captured and disentangled by time-resolved photoemission spectroscopy. This work demonstrates the dominant role of phase coherence in the superconductor-to-normal state phase transition and offers a benchmark for non-equilibrium spectroscopic investigations of the cuprate phase diagram.
Ambipolar Landau levels and strong band-selective carrier interactions in monolayer WSe2 Nat. Mater. (IF 39.737) Pub Date : 2018-03-26 Martin V. Gustafsson, Matthew Yankowitz, Carlos Forsythe, Daniel Rhodes, Kenji Watanabe, Takashi Taniguchi, James Hone, Xiaoyang Zhu, Cory R. Dean
Monolayers (MLs) of transition-metal dichalcogenides (TMDs) exhibit unusual electrical behaviour under magnetic fields due to their intrinsic spin–orbit coupling and lack of inversion symmetry1,2,3,4,5,6,7,8,9,10,11,12,13,14,15. Although recent experiments have also identified the critical role of carrier interactions within these materials11,15, a complete mapping of the ambipolar Landau level (LL) sequence has remained elusive. Here we use single-electron transistors (SETs)16,17 to perform LL spectroscopy in ML WSe2, and provide a comprehensive picture of the electronic structure of a ML TMD for both electrons and holes. We find that the LLs differ notably between the two bands, and follow a unique sequence in the valence band (VB) that is dominated by strong Zeeman effects. The Zeeman splitting in the VB is several times higher than the cyclotron energy, far exceeding the predictions of a single-particle model and, moreover, tunes significantly with doping15. This implies exceptionally strong many-body interactions, and suggests that ML WSe2 can serve as a host for new correlated-electron phenomena.
The effective way Nat. Mater. (IF 39.737) Pub Date : 2018-03-26 Michel Fruchart, Vincenzo Vitelli
The effective way The effective way, Published online: 26 March 2018; doi:10.1038/s41563-018-0050-4 A theoretical framework for the design of so-called perturbative metamaterials, based on weakly interacting unit cells, has led to the experimental demonstration of a quadrupole topological insulator.
All-organic superhydrophobic coatings with mechanochemical robustness and liquid impalement resistance Nat. Mater. (IF 39.737) Pub Date : 2018-03-26 Chaoyi Peng, Zhuyang Chen, Manish K. Tiwari
Superhydrophobicity is a remarkable evolutionary adaption manifested by several natural surfaces. Artificial superhydrophobic coatings with good mechanical robustness, substrate adhesion and chemical robustness have been achieved separately. However, a simultaneous demonstration of these features along with resistance to liquid impalement via high-speed drop/jet impact is challenging. Here, we describe all-organic, flexible superhydrophobic nanocomposite coatings that demonstrate strong mechanical robustness under cyclic tape peels and Taber abrasion, sustain exposure to highly corrosive media, namely aqua regia and sodium hydroxide solutions, and can be applied to surfaces through scalable techniques such as spraying and brushing. In addition, the mechanical flexibility of our coatings enables impalement resistance to high-speed drops and turbulent jets at least up to ~35 m s−1 and a Weber number of ~43,000. With multifaceted robustness and scalability, these coatings should find potential usage in harsh chemical engineering as well as infrastructure, transport vehicles and communication equipment.
Multilevel robustness Nat. Mater. (IF 39.737) Pub Date : 2018-03-26 Henri-Louis Girard, Sami Khan, Kripa K. Varanasi
Multilevel robustness Multilevel robustness, Published online: 26 March 2018; doi:10.1038/s41563-018-0051-3 A combination of hard, soft and nanoscale organic components results in robust superhydrophobic surfaces that can withstand mechanical abrasion and chemical oxidation, and exhibit excellent substrate adhesion.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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