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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
Yue Shao, Kenichiro Taniguchi, Katherine Gurdziel, Ryan F Townshend, Xufeng Xue, Koh Meng Aw Yong, Jianming Sang, Jason R Spence, Deborah L Gumucio, Jianping Fu
Amniogenesis-the development of amnion-is a critical developmental milestone for early human embryogenesis and successful pregnancy. However, human amniogenesis is poorly understood due to limited accessibility to peri-implantation embryos and a lack of in vitro models. Here we report an efficient biomaterial system to generate human amnion-like tissue in vitro through self-organized development of human pluripotent stem cells (hPSCs) in a bioengineered niche mimicking the in vivo implantation environment...
December 12, 2016: Nature Materials
Mark Nikolka, Iyad Nasrallah, Bradley Rose, Mahesh Kumar Ravva, Katharina Broch, Aditya Sadhanala, David Harkin, Jerome Charmet, Michael Hurhangee, Adam Brown, Steffen Illig, Patrick Too, Jan Jongman, Iain McCulloch, Jean-Luc Bredas, Henning Sirringhaus
Due to their low-temperature processing properties and inherent mechanical flexibility, conjugated polymer field-effect transistors (FETs) are promising candidates for enabling flexible electronic circuits and displays. Much progress has been made on materials performance; however, there remain significant concerns about operational and environmental stability, particularly in the context of applications that require a very high level of threshold voltage stability, such as active-matrix addressing of organic light-emitting diode displays...
December 12, 2016: Nature Materials
Vladimir A Kolesov, Canek Fuentes-Hernandez, Wen-Fang Chou, Naoya Aizawa, Felipe A Larrain, Ming Wang, Alberto Perrotta, Sangmoo Choi, Samuel Graham, Guillermo C Bazan, Thuc-Quyen Nguyen, Seth R Marder, Bernard Kippelen
Solution-based electrical doping protocols may allow more versatility in the design of organic electronic devices; yet, controlling the diffusion of dopants in organic semiconductors and their stability has proven challenging. Here we present a solution-based approach for electrical p-doping of films of donor conjugated organic semiconductors and their blends with acceptors over a limited depth with a decay constant of 10-20 nm by post-process immersion into a polyoxometalate solution (phosphomolybdic acid, PMA) in nitromethane...
December 5, 2016: Nature Materials
S Weimann, M Kremer, Y Plotnik, Y Lumer, S Nolte, K G Makris, M Segev, M C Rechtsman, A Szameit
Parity-time (PT)-symmetric crystals are a class of non-Hermitian systems that allow, for example, the existence of modes with real propagation constants, for self-orthogonality of propagating modes, and for uni-directional invisibility at defects. Photonic PT-symmetric systems that also support topological states could be useful for shaping and routing light waves. However, it is currently debated whether topological interface states can exist at all in PT-symmetric systems. Here, we show theoretically and demonstrate experimentally the existence of such states: states that are localized at the interface between two topologically distinct PT-symmetric photonic lattices...
December 5, 2016: Nature Materials
Hyung-Seok Kim, John B Cook, Hao Lin, Jesse S Ko, Sarah H Tolbert, Vidvuds Ozolins, Bruce Dunn
The short charging times and high power capabilities associated with capacitive energy storage make this approach an attractive alternative to batteries. One limitation of electrochemical capacitors is their low energy density and for this reason, there is widespread interest in pseudocapacitive materials that use Faradaic reactions to store charge. One candidate pseudocapacitive material is orthorhombic MoO3 (α-MoO3), a layered compound with a high theoretical capacity for lithium (279 mA h g(-1) or 1,005 C g(-1))...
December 5, 2016: Nature Materials
Paolo Falcaro, Kenji Okada, Takaaki Hara, Ken Ikigaki, Yasuaki Tokudome, Aaron W Thornton, Anita J Hill, Timothy Williams, Christian Doonan, Masahide Takahashi
The fabrication of oriented, crystalline films of metal-organic frameworks (MOFs) is a critical step toward their application to advanced technologies such as optics, microelectronics, microfluidics and sensing. However, the direct synthesis of MOF films with controlled crystalline orientation remains a significant challenge. Here we report a one-step approach, carried out under mild conditions, that exploits heteroepitaxial growth for the rapid fabrication of oriented polycrystalline MOF films on the centimetre scale...
December 5, 2016: Nature Materials
Eléonore Mourad, Laura Coustan, Pierre Lannelongue, Dodzi Zigah, Ahmad Mehdi, André Vioux, Stefan A Freunberger, Frédéric Favier, Olivier Fontaine
Kinetics of electrochemical reactions are several orders of magnitude slower in solids than in liquids as a result of the much lower ion diffusivity. Yet, the solid state maximizes the density of redox species, which is at least two orders of magnitude lower in liquids because of solubility limitations. With regard to electrochemical energy storage devices, this leads to high-energy batteries with limited power and high-power supercapacitors with a well-known energy deficiency. For such devices the ideal system should endow the liquid state with a density of redox species close to the solid state...
November 28, 2016: Nature Materials
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