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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
Tony Low, Andrey Chaves, Joshua D Caldwell, Anshuman Kumar, Nicholas X Fang, Phaedon Avouris, Tony F Heinz, Francisco Guinea, Luis Martin-Moreno, Frank Koppens
In recent years, enhanced light-matter interactions through a plethora of dipole-type polaritonic excitations have been observed in two-dimensional (2D) layered materials. In graphene, electrically tunable and highly confined plasmon-polaritons were predicted and observed, opening up opportunities for optoelectronics, bio-sensing and other mid-infrared applications. In hexagonal boron nitride, low-loss infrared-active phonon-polaritons exhibit hyperbolic behaviour for some frequencies, allowing for ray-like propagation exhibiting high quality factors and hyperlensing effects...
November 28, 2016: Nature Materials
Li Zhong, Frederic Sansoz, Yang He, Chongmin Wang, Ze Zhang, Scott X Mao
Nanoscale metallic crystals have been shown to follow a 'smaller is stronger' trend. However, they usually suffer from low ductility due to premature plastic instability by source-limited crystal slip. Here, by performing in situ atomic-scale transmission electron microscopy, we report unusual room-temperature super-elongation without softening in face-centred-cubic silver nanocrystals, where crystal slip serves as a stimulus to surface diffusional creep. This interplay mechanism is shown experimentally and theoretically to govern the plastic deformation of nanocrystals over a material-dependent sample diameter range between the lower and upper limits for nanocrystal stability by surface diffusional creep and dislocation plasticity, respectively, which extends far beyond the maximum size for pure diffusion-mediated deformation (for example, Coble-type creep)...
November 28, 2016: Nature Materials
Jian-Wen Dong, Xiao-Dong Chen, Hanyu Zhu, Yuan Wang, Xiang Zhang
Photonic crystals offer unprecedented opportunity for light manipulation and applications in optical communication and sensing. Exploration of topology in photonic crystals and metamaterials with non-zero gauge field has inspired a number of intriguing optical phenomena such as one-way transport and Weyl points. Recently, a new degree of freedom, valley, has been demonstrated in two-dimensional materials. Here, we propose a concept of valley photonic crystals with electromagnetic duality symmetry but broken inversion symmetry...
November 28, 2016: Nature Materials
Marçal Capdevila-Cortada, Núria López
Surface structure controls the physical and chemical response of materials. Surface polar terminations are appealing because of their unusual properties but they are intrinsically unstable. Several mechanisms, namely metallization, adsorption, and ordered reconstructions, can remove thermodynamic penalties rendering polar surfaces partially stable. Here, for CeO2(100), we report a complementary stabilization mechanism based on surface disorder that has been unravelled through theoretical simulations that: account for surface energies and configurational entropies; show the importance of the ion distribution degeneracy; and identify low diffusion barriers between conformations that ensure equilibration...
November 21, 2016: Nature Materials
Derya Baran, Raja Shahid Ashraf, David A Hanifi, Maged Abdelsamie, Nicola Gasparini, Jason A Röhr, Sarah Holliday, Andrew Wadsworth, Sarah Lockett, Marios Neophytou, Christopher J M Emmott, Jenny Nelson, Christoph J Brabec, Aram Amassian, Alberto Salleo, Thomas Kirchartz, James R Durrant, Iain McCulloch
Technological deployment of organic photovoltaic modules requires improvements in device light-conversion efficiency and stability while keeping material costs low. Here we demonstrate highly efficient and stable solar cells using a ternary approach, wherein two non-fullerene acceptors are combined with both a scalable and affordable donor polymer, poly(3-hexylthiophene) (P3HT), and a high-efficiency, low-bandgap polymer in a single-layer bulk-heterojunction device. The addition of a strongly absorbing small molecule acceptor into a P3HT-based non-fullerene blend increases the device efficiency up to 7...
November 21, 2016: Nature Materials
S O Hruszkewycz, M Allain, M V Holt, C E Murray, J R Holt, P H Fuoss, V Chamard
Coherent X-ray microscopy by phase retrieval of Bragg diffraction intensities enables lattice distortions within a crystal to be imaged at nanometre-scale spatial resolutions in three dimensions. While this capability can be used to resolve structure-property relationships at the nanoscale under working conditions, strict data measurement requirements can limit the application of current approaches. Here, we introduce an efficient method of imaging three-dimensional (3D) nanoscale lattice behaviour and strain fields in crystalline materials with a methodology that we call 3D Bragg projection ptychography (3DBPP)...
November 21, 2016: Nature Materials
Can Onur Avci, Andy Quindeau, Chi-Feng Pai, Maxwell Mann, Lucas Caretta, Astera S Tang, Mehmet C Onbasli, Caroline A Ross, Geoffrey S D Beach
The spin Hall effect in heavy metals converts charge current into pure spin current, which can be injected into an adjacent ferromagnet to exert a torque. This spin-orbit torque (SOT) has been widely used to manipulate the magnetization in metallic ferromagnets. In the case of magnetic insulators (MIs), although charge currents cannot flow, spin currents can propagate, but current-induced control of the magnetization in a MI has so far remained elusive. Here we demonstrate spin-current-induced switching of a perpendicularly magnetized thulium iron garnet film driven by charge current in a Pt overlayer...
November 21, 2016: Nature Materials
Stephen Dongmin Kang, G Jeffrey Snyder
The growing technological importance of conducting polymers makes the fundamental understanding of their charge transport extremely important for materials and process design. Various hopping and mobility edge transport mechanisms have been proposed, but their experimental verification is limited to poor conductors. Now that advanced organic and polymer semiconductors have shown high conductivity approaching that of metals, the transport mechanism should be discernible by modelling the transport like a semiconductor with a transport edge and a transport parameter s...
November 14, 2016: Nature Materials
Tadej Rojac, Andreja Bencan, Goran Drazic, Naonori Sakamoto, Hana Ursic, Bostjan Jancar, Gasper Tavcar, Maja Makarovic, Julian Walker, Barbara Malic, Dragan Damjanovic
Mobile charged defects, accumulated in the domain-wall region to screen polarization charges, have been proposed as the origin of the electrical conductivity at domain walls in ferroelectric materials. Despite theoretical and experimental efforts, this scenario has not been directly confirmed, leaving a gap in the understanding of the intriguing electrical properties of domain walls. Here, we provide atomic-scale chemical and structural analyses showing the accumulation of charged defects at domain walls in BiFeO3...
November 14, 2016: Nature Materials
Jeffrey J Urban
No abstract text is available yet for this article.
November 14, 2016: Nature Materials
H Hussain, G Tocci, T Woolcot, X Torrelles, C L Pang, D S Humphrey, C M Yim, D C Grinter, G Cabailh, O Bikondoa, R Lindsay, J Zegenhagen, A Michaelides, G Thornton
The interaction of water with TiO2 is crucial to many of its practical applications, including photocatalytic water splitting. Following the first demonstration of this phenomenon 40 years ago there have been numerous studies of the rutile single-crystal TiO2(110) interface with water. This has provided an atomic-level understanding of the water-TiO2 interaction. However, nearly all of the previous studies of water/TiO2 interfaces involve water in the vapour phase. Here, we explore the interfacial structure between liquid water and a rutile TiO2(110) surface pre-characterized at the atomic level...
November 14, 2016: Nature Materials
Mengxia Liu, Oleksandr Voznyy, Randy Sabatini, F Pelayo García de Arquer, Rahim Munir, Ahmed Hesham Balawi, Xinzheng Lan, Fengjia Fan, Grant Walters, Ahmad R Kirmani, Sjoerd Hoogland, Frédéric Laquai, Aram Amassian, Edward H Sargent
Bandtail states in disordered semiconductor materials result in losses in open-circuit voltage (Voc) and inhibit carrier transport in photovoltaics. For colloidal quantum dot (CQD) films that promise low-cost, large-area, air-stable photovoltaics, bandtails are determined by CQD synthetic polydispersity and inhomogeneous aggregation during the ligand-exchange process. Here we introduce a new method for the synthesis of solution-phase ligand-exchanged CQD inks that enable a flat energy landscape and an advantageously high packing density...
November 14, 2016: Nature Materials
Jinhui Yang, Jason K Cooper, Francesca M Toma, Karl A Walczak, Marco Favaro, Jeffrey W Beeman, Lucas H Hess, Cheng Wang, Chenhui Zhu, Sheraz Gul, Junko Yano, Christian Kisielowski, Adam Schwartzberg, Ian D Sharp
Artificial photosystems are advanced by the development of conformal catalytic materials that promote desired chemical transformations, while also maintaining stability and minimizing parasitic light absorption for integration on surfaces of semiconductor light absorbers. Here, we demonstrate that multifunctional, nanoscale catalysts that enable high-performance photoelectrochemical energy conversion can be engineered by plasma-enhanced atomic layer deposition. The collective properties of tailored Co3O4/Co(OH)2 thin films simultaneously provide high activity for water splitting, permit efficient interfacial charge transport from semiconductor substrates, and enhance durability of chemically sensitive interfaces...
November 7, 2016: Nature Materials
Li-Na Niu, Sang Eun Jee, Kai Jiao, Lige Tonggu, Mo Li, Liguo Wang, Yao-Dong Yang, Ji-Hong Bian, Lorenzo Breschi, Seung Soon Jang, Ji-Hua Chen, David H Pashley, Franklin R Tay
Mineralization of fibrillar collagen with biomimetic process-directing agents has enabled scientists to gain insight into the potential mechanisms involved in intrafibrillar mineralization. Here, by using polycation- and polyanion-directed intrafibrillar mineralization, we challenge the popular paradigm that electrostatic attraction is solely responsible for polyelectrolyte-directed intrafibrillar mineralization. As there is no difference when a polycationic or a polyanionic electrolyte is used to direct collagen mineralization, we argue that additional types of long-range non-electrostatic interaction are responsible for intrafibrillar mineralization...
November 7, 2016: Nature Materials
Onur Ergen, S Matt Gilbert, Thang Pham, Sally J Turner, Mark Tian Zhi Tan, Marcus A Worsley, Alex Zettl
Organic-inorganic halide perovskite materials have emerged as attractive alternatives to conventional solar cell building blocks. Their high light absorption coefficients and long diffusion lengths suggest high power conversion efficiencies, and indeed perovskite-based single bandgap and tandem solar cell designs have yielded impressive performances. One approach to further enhance solar spectrum utilization is the graded bandgap, but this has not been previously achieved for perovskites. In this study, we demonstrate graded bandgap perovskite solar cells with steady-state conversion efficiencies averaging 18...
November 7, 2016: Nature Materials
Li Ji, Hsien-Yi Hsu, Xiaohan Li, Kai Huang, Ye Zhang, Jack C Lee, Allen J Bard, Edward T Yu
Silicon-based photoelectrodes for solar fuel production have attracted great interest over the past decade, with the major challenge being silicon's vulnerability to corrosion. A metal-insulator-semiconductor architecture, in which an insulator film serves as a protection layer, can prevent corrosion but must also allow low-resistance carrier transport, generally leading to a trade-off between stability and efficiency. In this work, we propose and demonstrate a general method to decouple the two roles of the insulator by employing localized dielectric breakdown...
November 7, 2016: Nature Materials
Min Hao Wong, Juan P Giraldo, Seon-Yeong Kwak, Volodymyr B Koman, Rosalie Sinclair, Tedrick Thomas Salim Lew, Gili Bisker, Pingwei Liu, Michael S Strano
Plant nanobionics aims to embed non-native functions to plants by interfacing them with specifically designed nanoparticles. Here, we demonstrate that living spinach plants (Spinacia oleracea) can be engineered to serve as self-powered pre-concentrators and autosamplers of analytes in ambient groundwater and as infrared communication platforms that can send information to a smartphone. The plants employ a pair of near-infrared fluorescent nanosensors-single-walled carbon nanotubes (SWCNTs) conjugated to the peptide Bombolitin II to recognize nitroaromatics via infrared fluorescent emission, and polyvinyl-alcohol functionalized SWCNTs that act as an invariant reference signal-embedded within the plant leaf mesophyll...
October 31, 2016: Nature Materials
Qing Lin He, Xufeng Kou, Alexander J Grutter, Gen Yin, Lei Pan, Xiaoyu Che, Yuxiang Liu, Tianxiao Nie, Bin Zhang, Steven M Disseler, Brian J Kirby, William Ratcliff Ii, Qiming Shao, Koichi Murata, Xiaodan Zhu, Guoqiang Yu, Yabin Fan, Mohammad Montazeri, Xiaodong Han, Julie A Borchers, Kang L Wang
Magnetic topological insulators such as Cr-doped (Bi,Sb)2Te3 provide a platform for the realization of versatile time-reversal symmetry-breaking physics. By constructing heterostructures exhibiting Néel order in an antiferromagnetic CrSb and ferromagnetic order in Cr-doped (Bi,Sb)2Te3, we realize emergent interfacial magnetic phenomena which can be tailored through artificial structural engineering. Through deliberate geometrical design of heterostructures and superlattices, we demonstrate the use of antiferromagnetic exchange coupling in manipulating the magnetic properties of magnetic topological insulators...
October 31, 2016: Nature Materials
Angelo S Mao, Jae-Won Shin, Stefanie Utech, Huanan Wang, Oktay Uzun, Weiwei Li, Madeline Cooper, Yuebi Hu, Liyuan Zhang, David A Weitz, David J Mooney
Existing techniques to encapsulate cells into microscale hydrogels generally yield high polymer-to-cell ratios and lack control over the hydrogel's mechanical properties. Here, we report a microfluidic-based method for encapsulating single cells in an approximately six-micrometre layer of alginate that increases the proportion of cell-containing microgels by a factor of ten, with encapsulation efficiencies over 90%. We show that in vitro cell viability was maintained over a three-day period, that the microgels are mechanically tractable, and that, for microscale cell assemblages of encapsulated marrow stromal cells cultured in microwells, osteogenic differentiation of encapsulated cells depends on gel stiffness and cell density...
October 31, 2016: Nature Materials
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