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| Open AccessZigzag line defects and manipulation of colloids in a nematic liquid crystal in microwrinkle grooves
Understanding defects in liquid crystals is important for controlling their structure and self-assembly properties. Here, nematic liquid crystals confined in microwrinkle grooves show new periodic arrangements and zigzag line defects that can trap particles, offering a method for colloid manipulation.
- Takuya Ohzono
- & Jun-ichi Fukuda
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| Open AccessRepeated growth and bubbling transfer of graphene with millimetre-size single-crystal grains using platinum
Grain boundaries in graphene degrade its properties, and large single-crystal graphene is desirable for electronic applications of graphene. Gaoet al. develop a method to produce millimetre-sized hexagonal single-crystal graphene grains, and films composed of the grains, on platinum by chemical vapour deposition.
- Libo Gao
- , Wencai Ren
- & Hui-Ming Cheng
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Article
| Open AccessResolving the electromagnetic mechanism of surface-enhanced light scattering at single hot spots
Light scattering from nanoscale objects can be dramatically enhanced in the proximity of optical antennas. Here, by studying the amplitude and phase of the light scattered from a tip located at the hot spot of an antenna, the underlying electromagnetic mechanism of this enhancement is resolved.
- P. Alonso-González
- , P. Albella
- & R. Hillenbrand
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Fully inorganic oxide-in-oxide ultraviolet nanocrystal light emitting devices
Light-emitting diodes in the form of nanocrystals offer promise for environmental and biomedical diagnostics. Brovelliet al. present a method for realizing mechanically robust and chemically stable nanocrystals emitting light in the ultraviolet range.
- Sergio Brovelli
- , Norberto Chiodini
- & Alberto Paleari
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Wide bandgap tunability in complex transition metal oxides by site-specific substitution
Tuning the bandgap of complex transition metal oxides in a manner that preserves their intrinsic properties has so far remained elusive. Choiet al. demonstrate that the bandgap of bismuth titanate can be varied by substitutional alloying with lanthanum cobaltate, without altering its ferroelectric properties.
- Woo Seok Choi
- , Matthew F. Chisholm
- & Ho Nyung Lee
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Emergence of non-centrosymmetric topological insulating phase in BiTeI under pressure
The spin–orbit interaction affects the electronic structure of many solids to give rise to a host of unusual phenomena. Bahramyet al.theoretically examine its role in the non-centrosymmetric compound BiTeI, and find that under the application of pressure, it leads to topologically insulating behaviour.
- M.S. Bahramy
- , B.-J. Yang
- & N. Nagaosa
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| Open AccessCMOS-based carbon nanotube pass-transistor logic integrated circuits
Field-effect transistors fabricated from carbon nanotubes have been investigated extensively over the past two decades. This study demonstrates a nanotube-based integrated circuit design that substantially improves the speed and power consumption with respect to silicon-based integrated circuits.
- Li Ding
- , Zhiyong Zhang
- & Lian-Mao Peng
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Broadband light management using low-Q whispering gallery modes in spherical nanoshells
Control of light absorption in optical devices, such as solar cells, can be achieved through resonant features like whispering gallery modes. Here, these modes are exploited in spherical silicon nanoshells to enhance absorption over a broad spectral range in nanometre-scale flexible layers.
- Yan Yao
- , Jie Yao
- & Yi Cui
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Article
| Open AccessSynergistic toughening of composite fibres by self-alignment of reduced graphene oxide and carbon nanotubes
Composite fibres made of polymers reinforced by carbon nanotubes are known for their exceptional toughness. Shinet al. make these composites even tougher, by self-aligning carbon nanotubes and reduced graphene oxide flakes within the polymer matrix.
- Min Kyoon Shin
- , Bommy Lee
- & Seon Jeong Kim
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Atom-specific spin mapping and buried topological states in a homologous series of topological insulators
Strategies to tune the surface properties of topological insulators are essential, if they are to find use in applications. Using a combination of theoretical and experimental techniques, this study examines how the properties of ordered ternary topological insulators vary with the content of group IV elements.
- Sergey V. Eremeev
- , Gabriel Landolt
- & Evgueni V. Chulkov
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Tunable Dirac cone in the topological insulator Bi2-xSbxTe3-ySey
The surface electronic structure of topological insulators is characterized by a so-called Dirac cone energy dispersion. This study shows that by tuning the compositions in the compound Bi2−xSbxTe3−ySeyone can control the precise features of its Dirac cone structure while keeping it a bulk insulator.
- T. Arakane
- , T. Sato
- & Yoichi Ando
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Chemical structures of hydrazine-treated graphene oxide and generation of aromatic nitrogen doping
Parket al. use 13C and 15N solid-state NMR and X-ray photoelectron spectroscopy to study the chemical structure of hydrazine-treated graphite oxide. Hydrazine treatment is shown to lead to the incorporation of aromatic N2moieties at the graphene edges and restore graphitic networks on the basal planes.
- Sungjin Park
- , Yichen Hu
- & Rodney S. Ruoff
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Near room-temperature synthesis of transfer-free graphene films
Current methods for fabricating graphene rely on its transfer from metal surfaces to substrates suitable for device applications. This study demonstrates a transfer-free approach for growing graphene on substrates such as thermally oxidized silicon and plastic that forms the material underneath a nickel film, at the nickel–substrate interface.
- Jinsung Kwak
- , Jae Hwan Chu
- & Soon-Yong Kwon
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| Open AccessGeometry analysis and systematic synthesis of highly porous isoreticular frameworks with a unique topology
Zhanget al. show that simple geometry analysis can be used to predict how linker length and length ratios affect pore shape and size of porous coordination polymers. The accuracy of the predictions is confirmed by the synthesis of a series of 13 highly porous isoreticular frameworks.
- Yue-Biao Zhang
- , Hao-Long Zhou
- & Xiao-Ming Chen
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| Open AccessObservation of the inverse spin Hall effect in silicon
The spin Hall effect is a spin current induced by an electric current, and its occurrence in semiconductors is a promising route to controlling spins and their transport. Here, the inverse spin Hall effect, in which an electric current is induced by a spin current, is observed in silicon for the first time.
- Kazuya Ando
- & Eiji Saitoh
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| Open AccessA cobalt complex redox shuttle for dye-sensitized solar cells with high open-circuit potentials
Dye-sensitized solar cells are a promising alternative to traditional inorganic semiconductor-based solar cells. Yumet al. use a molecularly engineered cobalt complex as a redox mediator to achieve an open-circuit voltage of over 1,000 mV in a mesoscopic dye-sensitized solar cell.
- Jun-Ho Yum
- , Etienne Baranoff
- & Michael Grätzel
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Momentum-dependent multiple gaps in magnesium diboride probed by electron tunnelling spectroscopy
The electronic structure of superconducting magnesium diboride is predicted theoretically to have a distribution of energy gap values. Chenet al. observe this distribution of values experimentally, by means of high-resolution electron tunnelling spectroscopy.
- Ke Chen
- , Wenqing Dai
- & X. X. Xi
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Mechanism of supercooled droplet freezing on surfaces
The mechanism through which ice forms on surfaces is of broad technological relevance. This study examines the manner in which ice forms on so-called 'icephobic' surfaces, and demonstrates that simple changes in the environmental conditions can render the icephobicity ineffective.
- Stefan Jung
- , Manish K. Tiwari
- & Dimos Poulikakos
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| Open AccessPhotoswitchable gel assembly based on molecular recognition
Self-assembly through molecular recognition events is used in the production of functionalized materials. This study shows that macroscopic gel assembly can be regulated through photoisomerization of an azobenzene moiety that interacts differently with two host molecules.
- Hiroyasu Yamaguchi
- , Yuichiro Kobayashi
- & Akira Harada
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| Open AccessApproaching the ideal elastic limit of metallic glasses
The elastic limit represents the maximum stress and strain a material can withstand and is well characterized in many crystalline solids, yet remains elusive for metallic glasses. Here, this limit is investigated in submicron metallic glass structures and is found to be twice as high as that of bulk samples.
- Lin Tian
- , Yong-Qiang Cheng
- & Evan Ma
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Metal-adeninate vertices for the construction of an exceptionally porous metal-organic framework
Metal‐organic framework (MOFs) with metal‐carboxylate cluster vertices and long, branched organic linkers are highly porous. Anet al. develop an alternative route to MOFs in which metal‐biomolecule clusters are used as vertices to construct a mesoporous MOF.
- Jihyun An
- , Omar K. Farha
- & Nathaniel L. Rosi
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Revealing the role of defects in ferroelectric switching with atomic resolution
Ferroelectric materials are characterized by a spontaneous polarization, which in practical applications is manipulated by an electric field. This study examines how defects affect the switching with atomic resolution, by usingin situaberration-corrected transmission electron microscopy.
- Peng Gao
- , Christopher T. Nelson
- & Xiaoqing Pan
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| Open AccessExtraordinary carrier multiplication gated by a picosecond electric field pulse
Studying carrier multiplication in materials is important to understand their transport properties and interaction with light. Hiroriet al. show that intense terahertz pulses can generate electron-hole pairs in GaAs quantum wells that then emit infrared light, contrary to the effect with a DC field.
- H. Hirori
- , K. Shinokita
- & K. Tanaka
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Inverse barocaloric effect in the giant magnetocaloric La–Fe–Si–Co compound
When materials change temperature as a result of the application of pressure or a change in the magnetization, they are said to display a barocaloric or magnetocaloric effect, respectively. This study reports a substantial barocaloric effect in the giant magnetocaloric material LaFe11.33Co0.47Si1.2.
- Lluís Mañosa
- , David González-Alonso
- & Subham Majumdar
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Interface engineering of quantum Hall effects in digital transition metal oxide heterostructures
Topological insulators are a class of materials with an unusual band structure that makes them metallic at the surface and insulating in the bulk. Okamoto and co-workers use electronic structure calculations to predict a new family of possible topological insulators based on transition-metal oxides.
- Di Xiao
- , Wenguang Zhu
- & Satoshi Okamoto
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Article
| Open AccessStable prenucleation mineral clusters are liquid-like ionic polymers
Prenucleation clusters have been observed during the early stages of calcium carbonate formation, contrary to classical models. Here, computer simulations indicate that the clusters are composed of an ionic polymer with alternating calcium and carbonate ions, and a dynamic topology of chains, branches and rings.
- Raffaella Demichelis
- , Paolo Raiteri
- & Denis Gebauer
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Low-power nano-optical vortex trapping via plasmonic diabolo nanoantennas
Optical vortex traps are appealing for handling delicate particles, but conventional techniques are challenging with objects smaller than the diffraction limit of light. By exploiting plasmonic resonances in gold diabolo nanoantennas, Kanget al. demonstrate low-power vortex trapping of nano-scale objects.
- Ju-Hyung Kang
- , Kipom Kim
- & Hong-Gyu Park
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Article
| Open AccessTandem synthesis of alternating polyesters from renewable resources
Biomass-derived monomers are a renewable resource for the production of polymers. Robertet al. develop an auto-tandem catalytic transformation for the synthesis of aliphatic polyesters—'activated' monomers are prepared from dicarboxylic acids, which can be copolymerized with epoxides.
- Carine Robert
- , Frédéric de Montigny
- & Christophe M. Thomas
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Rebalancing of internally generated carriers for mid-infrared interband cascade lasers with very low power consumption
Mid-infrared semiconductor lasers suffer from a high threshold power density, but interband cascade lasers may offer a more efficient alternative. Here, theory and experiments on such emitters demonstrate remarkably low thresholds and power consumption compared to state-of-the-art quantum cascade lasers.
- I. Vurgaftman
- , W.W. Bewley
- & J.R. Meyer
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Band structure engineering in (Bi1−xSbx)2Te3 ternary topological insulators
The unique band structure of topological insulators gives rise to insulating bulk and unusual metallic surface properties. By tuning the content of Sb in the ternary compound (Bi1–xSbx)2Te3, Wang and collaborators show it is possible to control the precise features of the band structure in a continuous fashion.
- Jinsong Zhang
- , Cui-Zu Chang
- & Yayu Wang
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Spin waves and magnetic exchange interactions in insulating Rb0.89Fe1.58Se2
Unlike the other iron-based superconductors, the parent compounds of the alkaline iron selenide superconductors are insulators. Dai and colleagues examine the spin-wave excitations in these materials and uncover evidence for a common magnetic origin for all iron-based superconductors.
- Miaoyin Wang
- , Chen Fang
- & Pengcheng Dai
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Article
| Open AccessGraphene chiral liquid crystals and macroscopic assembled fibres
Chiral liquid crystals of two-dimensional colloids have not been extensively investigated. Xu and Gao show that graphene oxide can form chiral liquid crystals, and demonstrate that they can be spun into macroscopic fibres, and that subsequent chemical reduction provides graphene fibres with high conductivity.
- Zhen Xu
- & Chao Gao
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Plasmon resonance enhanced multicolour photodetection by graphene
Among the wide range of potential applications of graphene, photodetection is believed to be among the most promising. By combining graphene with plasmonic nanostructures, Duan and colleagues observe dramatic improvements in the efficiency and spectral sensitivity of graphene-based photodetectors.
- Yuan Liu
- , Rui Cheng
- & Xiangfeng Duan
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Article
| Open AccessGate-tuned normal and superconducting transport at the surface of a topological insulator
Topological insulators are a unique class of materials characterized by exotic metallic states at their surface, while remaining insulated in the bulk. Sacépéet al. show how to manipulate normal and superconducting electronic transport at the surface of the topological insulator Bi2Se3, by tuning a gate-voltage to vary the electronic density.
- Benjamin Sacépé
- , Jeroen B. Oostinga
- & Alberto F. Morpurgo
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Charge density waves in the graphene sheets of the superconductor CaC6
Charge density waves in the structure and electron density of layered materials are closely linked to superconductivity. Using scanning tunnelling techniques, Rahnejatet al. demonstrate the occurrence of such waves in the doped graphene sheets of the superconductor CaC6.
- K.C. Rahnejat
- , C.A. Howard
- & M. Ellerby
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Three-dimensional high-resolution quantitative microscopy of extended crystals
X-ray ptychography has been used to extend the field of view in high-resolution quantitative imaging. Godardet al. develop Bragg-mode ptychography to reconstruct, in three dimensions, a crystalline specimen that is too large to be studied as a single object with a coherence-limited X-ray beam.
- P. Godard
- , G. Carbone
- & V. Chamard
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| Open AccessSuppression of the intrinsic stochastic pinning of domain walls in magnetic nanostripes
The propagation of magnetic domain walls in nanowires offers promise as the basis of future memory storage technologies. Muñoz and Prieto show that the random pinning of domain walls to structural defects in the nanowires can be suppressed at low fields, thus improving the reliability of the transmission of the domain walls substantially.
- Manuel Muñoz
- & José L. Prieto
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Towards hybrid superlattices in graphene
The controllable modification of graphene by chemical functionalization can modulate its optical and electronic properties. Sunet al. devise a functionalisation-based method to pattern graphane/graphene superlattices within a single sheet of graphene.
- Zhengzong Sun
- , Cary L. Pint
- & James M. Tour
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Concurrent transition of ferroelectric and magnetic ordering near room temperature
Magnetoelectric materials combine ferroelectric and magnetic properties through a coupling of the spin and lattice degrees of freedom. Here, magnetoelectric bismuth ferrite is found to simultaneously undergo both a magnetic and a ferroelectric transition at the same temperature.
- Kyung-Tae Ko
- , Min Hwa Jung
- & Chan-Ho Yang
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| Open AccessA new regime for mechanical annealing and strong sample-size strengthening in body centred cubic molybdenum
Mechanical annealing is a process through which the dislocation density in submicrometre metal crystals can be removed purely by applying a mechanical stress. This study shows that mechanical annealing occurs in body centred cubic molybdenum, and not only in face centred crystals as previously thought.
- Ling Huang
- , Qing-Jie Li
- & Evan Ma
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Copper hexacyanoferrate battery electrodes with long cycle life and high power
Batteries that operate at high power and cycling efficiencies could facilitate the development of large-scale energy storage systems. Wessellset al.report a metal–organic framework electrode that operates in an inexpensive aqueous electrolyte with excellent capacity retention over a very large number of cycles.
- Colin D. Wessells
- , Robert A. Huggins
- & Yi Cui
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| Open AccessHigh-density magnetoresistive random access memory operating at ultralow voltage at room temperature
Magnetoresistive random access memory offers significant promise as a next-generation memory technology. Nan and colleagues present a design concept for a device that simultaneously possesses ultrahigh storage capacity, ultralow power dissipation, and high-speed operation at room temperature.
- Jia-Mian Hu
- , Zheng Li
- & Ce-Wen Nan
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Ultrafast direct modulation of a single-mode photonic crystal nanocavity light-emitting diode
Photonic alternatives to electrical circuits require low energy demand and fast modulation speed, which has proven difficult for on-chip devices. Using quantum dot photonic crystal nanocavities, Vučkovićet al. demonstrate an electrically-switchable light-emitting diode with such capabilities.
- Gary Shambat
- , Bryan Ellis
- & Jelena Vučković
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| Open AccessPore surface engineering in covalent organic frameworks
Covalent organic frameworks form a porous skeleton with a precise pore size and geometry, but control of the pore surface is challenging. Here, a protocol is introduced for pore surface engineering of covalent organic frameworks, allowing the control of composition and density of organic groups in the pores.
- Atsushi Nagai
- , Zhaoqi Guo
- & Donglin Jiang
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Self-assembly of DNA nanotubes with controllable diameters
DNA nanotubes could be used to transport nano-cargo and incorporated into nano-devices. In this study, rolling circle amplification is used to generate DNA subunits, and their thermodynamic growth results in the formation of nanotubes with a controlled diameter.
- Ofer I. Wilner
- , Ron Orbach
- & Itamar Willner
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Selective dispersion of high purity semiconducting single-walled carbon nanotubes with regioregular poly(3-alkylthiophene)s
Metallic and semiconducting carbon nanotubes generally coexist in 'as-grown' materials. In this study, single-walled nanotubes are sorted using regioregular poly(3-alkylthiophene)s; rational selection of polymers, solvent and temperature allows the selective dispersion of semiconducting carbon nanotubes.
- Hang Woo Lee
- , Yeohoon Yoon
- & Zhenan Bao
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Differentially photo-crosslinked polymers enable self-assembling microfluidics
Leaves and tissues contain three-dimensional networks of fluidic channels, but similar artificial self-assembling systems have not yet been produced. Jamalet al. develop methods to produce three-dimensional microfluidic networks with curved geometries from the self-assembly of photopatterned polymers.
- Mustapha Jamal
- , Aasiyeh M. Zarafshar
- & David H. Gracias
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| Open AccessA guideline for atomistic design and understanding of ultrahard nanomagnets
Controlling the magnetic properties of nanoparticles is important to enable their widespread use in applications. Antoniaket al. combine X-ray absorption spectroscopy and density functional theory calculations to uncover the origin of these properties in order to appropriately tailor nanoparticle design.
- Carolin Antoniak
- , Markus E. Gruner
- & Heiko Wende
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Broadband polarization-independent resonant light absorption using ultrathin plasmonic super absorbers
Plasmonic nanostructures and metamaterials can augment the performance of photovoltaic and thermophotovoltaic cells by enhancing their absorption properties. Aydinet al. demonstrate a broadband, ultrathin plasmonic super absorber using crossed trapezoids as part of a metal–insulator–metal stack.
- Koray Aydin
- , Vivian E. Ferry
- & Harry A. Atwater