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Nature Materials

M Mogi, M Kawamura, R Yoshimi, A Tsukazaki, Y Kozuka, N Shirakawa, K S Takahashi, M Kawasaki, Y Tokura
The axion insulator which may exhibit an exotic quantized magnetoelectric effect is one of the most interesting quantum phases predicted for the three-dimensional topological insulator (TI). The axion insulator state is expected to show up in magnetically doped TIs with magnetizations pointing inwards and outwards from the respective surfaces. Towards the realization of the axion insulator, we here engineered a TI heterostructure in which magnetic ions (Cr) are modulation-doped only in the vicinity of the top and bottom surfaces of the TI ((Bi,Sb)2Te3) film...
February 13, 2017: Nature Materials
Yoon Hwa Kim, Paulraj Arunkumar, Bo Young Kim, Sanjith Unithrattil, Eden Kim, Su-Hyun Moon, Jae Young Hyun, Ki Hyun Kim, Donghwa Lee, Jong-Sook Lee, Won Bin Im
Phosphor-converted white light-emitting diodes (pc-WLEDs) are efficient light sources used in lighting, high-tech displays, and electronic devices. One of the most significant challenges of pc-WLEDs is the thermal quenching, in which the phosphor suffers from emission loss with increasing temperature during high-power LED operation. Here, we report a blue-emitting Na3-2xSc2(PO4)3:xEu(2+) phosphor (λem = 453 nm) that does not exhibit thermal quenching even up to 200 °C. This phenomenon of zero thermal quenching originates from the ability of the phosphor to compensate the emission losses and therefore sustain the luminescence with increasing temperature...
February 13, 2017: Nature Materials
S Eley, M Miura, B Maiorov, L Civale
Superconductors are excellent testbeds for studying vortices, topological excitations that also appear in superfluids, liquid crystals and Bose-Einstein condensates. Vortex motion can be disruptive; it can cause phase transitions, glitches in pulsars, and losses in superconducting microwave circuits, and it limits the current-carrying capacity of superconductors. Understanding vortex dynamics is fundamentally and technologically important, and the competition between thermal energy and energy barriers defined by material disorder is not completely understood...
February 13, 2017: Nature Materials
Ryo Ohshima, Yuichiro Ando, Kosuke Matsuzaki, Tomofumi Susaki, Mathias Weiler, Stefan Klingler, Hans Huebl, Eiji Shikoh, Teruya Shinjo, Sebastian T B Goennenwein, Masashi Shiraishi
A d-orbital electron has an anisotropic electron orbital and is a source of magnetism. The realization of a two-dimensional electron gas (2DEG) embedded at a LaAlO3/SrTiO3 interface surprised researchers in materials and physical sciences because the 2DEG consists of 3d-electrons of Ti with extraordinarily large carrier mobility, even in the insulating oxide heterostructure. To date, a wide variety of physical phenomena, such as ferromagnetism and the quantum Hall effect, have been discovered in this 2DEG system, demonstrating the ability of d-electron 2DEG systems to provide a material platform for the study of interesting physics...
February 13, 2017: Nature Materials
Jin-Sil Choi, Soojin Kim, Dongwon Yoo, Tae-Hyun Shin, Hoyoung Kim, Muller D Gomes, Sun Hee Kim, Alexander Pines, Jinwoo Cheon
Nanoscale distance-dependent phenomena, such as Förster resonance energy transfer, are important interactions for use in sensing and imaging, but their versatility for bioimaging can be limited by undesirable photon interactions with the surrounding biological matrix, especially in in vivo systems. Here, we report a new type of magnetism-based nanoscale distance-dependent phenomenon that can quantitatively and reversibly sense and image intra-/intermolecular interactions of biologically important targets. We introduce distance-dependent magnetic resonance tuning (MRET), which occurs between a paramagnetic 'enhancer' and a superparamagnetic 'quencher', where the T1 magnetic resonance imaging (MRI) signal is tuned ON or OFF depending on the separation distance between the quencher and the enhancer...
February 6, 2017: Nature Materials
Chiara Malinverno, Salvatore Corallino, Fabio Giavazzi, Martin Bergert, Qingsen Li, Marco Leoni, Andrea Disanza, Emanuela Frittoli, Amanda Oldani, Emanuele Martini, Tobias Lendenmann, Gianluca Deflorian, Galina V Beznoussenko, Dimos Poulikakos, Kok Haur Ong, Marina Uroz, Xavier Trepat, Dario Parazzoli, Paolo Maiuri, Weimiao Yu, Aldo Ferrari, Roberto Cerbino, Giorgio Scita
Dynamics of epithelial monolayers has recently been interpreted in terms of a jamming or rigidity transition. How cells control such phase transitions is, however, unknown. Here we show that RAB5A, a key endocytic protein, is sufficient to induce large-scale, coordinated motility over tens of cells, and ballistic motion in otherwise kinetically arrested monolayers. This is linked to increased traction forces and to the extension of cell protrusions, which align with local velocity. Molecularly, impairing endocytosis, macropinocytosis or increasing fluid efflux abrogates RAB5A-induced collective motility...
January 30, 2017: Nature Materials
William J Koros, Chen Zhang
Materials research is key to enable synthetic membranes for large-scale, energy-efficient molecular separations. Materials with rigid, engineered pore structures add an additional degree of freedom to create advanced membranes by providing entropically moderated selectivities. Scalability - the capability to efficiently and economically pack membranes into practical modules - is a critical yet often neglected factor to take into account for membrane materials screening. In this Progress Article, we highlight continuing developments and identify future opportunities in scalable membrane materials based on these rigid features, for both gas and liquid phase applications...
January 23, 2017: Nature Materials
A Ulvestad, M J Welland, W Cha, Y Liu, J W Kim, R Harder, E Maxey, J N Clark, M J Highland, H You, P Zapol, S O Hruszkewycz, G B Stephenson
Crystallographic imperfections significantly alter material properties and their response to external stimuli, including solute-induced phase transformations. Despite recent progress in imaging defects using electron and X-ray techniques, in situ three-dimensional imaging of defect dynamics remains challenging. Here, we use Bragg coherent diffractive imaging to image defects during the hydriding phase transformation of palladium nanocrystals. During constant-pressure experiments we observe that the phase transformation begins after dislocation nucleation close to the phase boundary in particles larger than 300 nm...
January 16, 2017: Nature Materials
Alessandro Molle, Joshua Goldberger, Michel Houssa, Yong Xu, Shou-Cheng Zhang, Deji Akinwande
Silicene, germanene and stanene are part of a monoelemental class of two-dimensional (2D) crystals termed 2D-Xenes (X = Si, Ge, Sn and so on) which, together with their ligand-functionalized derivatives referred to as Xanes, are comprised of group IVA atoms arranged in a honeycomb lattice - similar to graphene but with varying degrees of buckling. Their electronic structure ranges from trivial insulators, to semiconductors with tunable gaps, to semi-metallic, depending on the substrate, chemical functionalization and strain...
January 16, 2017: Nature Materials
H Chu, L Zhao, A de la Torre, T Hogan, S D Wilson, D Hsieh
Layered perovskite iridates realize a rare class of Mott insulators that are predicted to be strongly spin-orbit coupled analogues of the parent state of cuprate high-temperature superconductors. Recent discoveries of pseudogap, magnetic multipolar ordered and possible d-wave superconducting phases in doped Sr2IrO4 have reinforced this analogy among the single layer variants. However, unlike the bilayer cuprates, no electronic instabilities have been reported in the doped bilayer iridate Sr3Ir2O7. Here we show that Sr3Ir2O7 realizes a weak Mott state with no cuprate analogue by using ultrafast time-resolved optical reflectivity to uncover an intimate connection between its insulating gap and antiferromagnetism...
January 16, 2017: Nature Materials
Tuan Anh Pham, Yuan Ping, Giulia Galli
The generation of hydrogen from water and sunlight offers a promising approach for producing scalable and sustainable carbon-free energy. The key of a successful solar-to-fuel technology is the design of efficient, long-lasting and low-cost photoelectrochemical cells, which are responsible for absorbing sunlight and driving water splitting reactions. To this end, a detailed understanding and control of heterogeneous interfaces between photoabsorbers, electrolytes and catalysts present in photoelectrochemical cells is essential...
January 9, 2017: Nature Materials
Xiaoming He, Ming-Siao Hsiao, Charlotte E Boott, Robert L Harniman, Ali Nazemi, Xiaoyu Li, Mitchell A Winnik, Ian Manners
The creation of shaped, uniform and colloidally stable two-dimensional (2D) assemblies by bottom-up methods represents a challenge of widespread current interest for a variety of applications. Herein, we describe the utilization of surface charge to stabilize self-assembled planar structures that are formed from crystallizable polymer precursors by a seeded growth approach. Addition of crystallizable homopolymers with charged end-groups to seeds generated by the sonication of block copolymer micelles with crystalline cores yields uniform platelet micelles with controlled dimensions...
January 9, 2017: Nature Materials
Hao Yan, J Nathan Hohman, Fei Hua Li, Chunjing Jia, Diego Solis-Ibarra, Bin Wu, Jeremy E P Dahl, Robert M K Carlson, Boryslav A Tkachenko, Andrey A Fokin, Peter R Schreiner, Arturas Vailionis, Taeho Roy Kim, Thomas P Devereaux, Zhi-Xun Shen, Nicholas A Melosh
Controlling inorganic structure and dimensionality through structure-directing agents is a versatile approach for new materials synthesis that has been used extensively for metal-organic frameworks and coordination polymers. However, the lack of 'solid' inorganic cores requires charge transport through single-atom chains and/or organic groups, limiting their electronic properties. Here, we report that strongly interacting diamondoid structure-directing agents guide the growth of hybrid metal-organic chalcogenide nanowires with solid inorganic cores having three-atom cross-sections, representing the smallest possible nanowires...
December 26, 2016: Nature Materials
Rui Kuai, Lukasz J Ochyl, Keith S Bahjat, Anna Schwendeman, James J Moon
Despite the tremendous potential of peptide-based cancer vaccines, their efficacy has been limited in humans. Recent innovations in tumour exome sequencing have signalled the new era of personalized immunotherapy with patient-specific neoantigens, but a general methodology for stimulating strong CD8α(+) cytotoxic T-lymphocyte (CTL) responses remains lacking. Here we demonstrate that high-density lipoprotein-mimicking nanodiscs coupled with antigen (Ag) peptides and adjuvants can markedly improve Ag/adjuvant co-delivery to lymphoid organs and sustain Ag presentation on dendritic cells...
December 26, 2016: Nature Materials
Ji Woong Yoon, Hyunju Chang, Seung-Joon Lee, Young Kyu Hwang, Do-Young Hong, Su-Kyung Lee, Ji Sun Lee, Seunghun Jang, Tae-Ung Yoon, Kijeong Kwac, Yousung Jung, Renjith S Pillai, Florian Faucher, Alexandre Vimont, Marco Daturi, Gérard Férey, Christian Serre, Guillaume Maurin, Youn-Sang Bae, Jong-San Chang
Selective dinitrogen binding to transition metal ions mainly covers two strategic domains: biological nitrogen fixation catalysed by metalloenzyme nitrogenases, and adsorptive purification of natural gas and air. Many transition metal-dinitrogen complexes have been envisaged for biomimetic nitrogen fixation to produce ammonia. Inspired by this concept, here we report mesoporous metal-organic framework materials containing accessible Cr(III) sites, able to thermodynamically capture N2 over CH4 and O2. This fundamental study integrating advanced experimental and computational tools confirmed that the separation mechanism for both N2/CH4 and N2/O2 gas mixtures is driven by the presence of these unsaturated Cr(III) sites that allows a much stronger binding of N2 over the two other gases...
December 19, 2016: Nature Materials
Xiaogang Han, Yunhui Gong, Kun Kelvin Fu, Xingfeng He, Gregory T Hitz, Jiaqi Dai, Alex Pearse, Boyang Liu, Howard Wang, Gary Rubloff, Yifei Mo, Venkataraman Thangadurai, Eric D Wachsman, Liangbing Hu
Garnet-type solid-state electrolytes have attracted extensive attention due to their high ionic conductivity, approaching 1 mS cm(-1), excellent environmental stability, and wide electrochemical stability window, from lithium metal to ∼6 V. However, to date, there has been little success in the development of high-performance solid-state batteries using these exceptional materials, the major challenge being the high solid-solid interfacial impedance between the garnet electrolyte and electrode materials...
December 19, 2016: Nature Materials
Paul J Ackerman, Ivan I Smalyukh
Three-dimensional (3D) topological solitons are continuous but topologically nontrivial field configurations localized in 3D space and embedded in a uniform far-field background, that behave like particles and cannot be transformed to a uniform state through smooth deformations. Many topologically nontrivial 3D solitonic fields have been proposed. Yet, according to the Hobart-Derrick theorem, physical systems cannot host them, except for nonlinear theories with higher-order derivatives such as the Skyrme-Faddeev model...
December 19, 2016: Nature Materials
Branko Zugic, Lucun Wang, Christian Heine, Dmitri N Zakharov, Barbara A J Lechner, Eric A Stach, Juergen Biener, Miquel Salmeron, Robert J Madix, Cynthia M Friend
Bimetallic, nanostructured materials hold promise for improving catalyst activity and selectivity, yet little is known about the dynamic compositional and structural changes that these systems undergo during pretreatment that leads to efficient catalyst function. Here we use ozone-activated silver-gold alloys in the form of nanoporous gold as a case study to demonstrate the dynamic behaviour of bimetallic systems during activation to produce a functioning catalyst. We show that it is these dynamic changes that give rise to the observed catalytic activity...
December 19, 2016: Nature Materials
R O Behunin, P Kharel, W H Renninger, P T Rakich
Optomechanics, nano-electromechanics, and integrated photonics have brought about a renaissance in phononic device physics and technology. Central to this advance are devices and materials supporting ultra-long-lived photonic and phononic excitations that enable novel regimes of classical and quantum dynamics based on tailorable photon-phonon coupling. Silica-based devices have been at the forefront of such innovations for their ability to support optical excitations persisting for nearly 1 billion cycles, and for their low optical nonlinearity...
December 12, 2016: Nature Materials
K Wang, P Murahari, K Yokoyama, J S Lord, F L Pratt, J He, L Schulz, M Willis, J E Anthony, N A Morley, L Nuccio, A Misquitta, D J Dunstan, K Shimomura, I Watanabe, S Zhang, P Heathcote, A J Drew
Photochemical reactions are essential to a large number of important industrial and biological processes. A method for monitoring photochemical reaction kinetics and the dynamics of molecular excitations with spatial resolution within the active molecule would allow a rigorous exploration of the pathway and mechanism of photophysical and photochemical processes. Here we demonstrate that laser-excited muon pump-probe spin spectroscopy (photo-μSR) can temporally and spatially map these processes with a spatial resolution at the single-carbon level in a molecule with a pentacene backbone...
December 12, 2016: Nature Materials
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