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Pressure-induced chemistry in a nitrogen-hydrogen host–guest structure
There is extensive research in the topochemistry of molecular systems at high pressure, although studies of binary gas mixtures are rarer. Here, the authors study a nitrogen/hydrogen mixture under pressure, identifying new van der Waals compounds and probing the room-temperature, high-pressure chemistry.
- Dylan K. Spaulding
- , Gunnar Weck
- & Michael Hanfland
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| Open AccessObserving classical nucleation theory at work by monitoring phase transitions with molecular precision
Many nanoscale systems can form ordered microphases through non-classical multistep nucleation. Here, the authors report that glucose isomerase, which is known to exhibit the characteristics of multi-step nucleation in 3D, nucleates along the pathway predicted by classical nucleation theory in 2D.
- Mike Sleutel
- , Jim Lutsko
- & Dominique Maes
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| Open AccessX-ray imaging of chemically active valence electrons during a pericyclic reaction
X-ray scattering experiments give details of the electrons in a system, although typically this is dominated by core and inert valence electrons. Here, the authors report a method to follow changes in the chemically active valence electrons, and use it to study the reaction mechanism of a pericyclic reaction.
- Timm Bredtmann
- , Misha Ivanov
- & Gopal Dixit
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| Open AccessNon-additivity of molecule-surface van der Waals potentials from force measurements
Van der Waals interactions are difficult to calculate at an atomistic level for moderate sized structures due to the many distinct atoms involved. Here, the authors measure the van der Waals force between an organic molecule and a metal surface, examining the non-additive part of these interactions.
- Christian Wagner
- , Norman Fournier
- & F. Stefan Tautz
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Deciphering the scaling of single-molecule interactions using Jarzynski’s equality
Adhesion forces depend on the strength and density of the individual molecular interactions of which they are composed. Here, the authors use surface force apparatus and atomic force microscopy to experimentally probe the scaling of single-molecule interactions into macroscopic properties.
- Sangeetha Raman
- , Thomas Utzig
- & Markus Valtiner
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Ostwald’s rule of stages governs structural transitions and morphology of dipeptide supramolecular polymers
Suparmolecular polymers are built by monomers via non-covalent bonds, whilst the pathway of their nucleation processes is not yet clear. Here, Levin et al.show that the self-assembly of monomers proceeds through a series of metastable states, which are energetically governed by Ostwald’s rule of stages.
- Aviad Levin
- , Thomas O. Mason
- & Ehud Gazit
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| Open AccessUnravelling the multilayer growth of the fullerene C60 in real time
Despite the technological relevance of molecular thin films, there is limited understanding of their growth on a molecular level. Here, the authors characterize the relevant processes in real time and determine energy parameters using a combination of X-ray techniques and kinetic Monte Carlo simulations.
- S. Bommel
- , N. Kleppmann
- & S. Kowarik
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Fingering versus stability in the limit of zero interfacial tension
Complex patterns arise in the non-linear growth regime upon the injection of a less viscous fluid into a more viscous one. Here, the authors show that the viscosity ratio between the two fluids controls a transition from branched fingers to blunt structures, and then eventually to a stable displacement.
- Irmgard Bischofberger
- , Radha Ramachandran
- & Sidney R. Nagel
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The unlikely Carnot efficiency
Carnot efficiency is the highest theoretically possible efficiency that a heat engine can have. Verley et al.use the fluctuation theorem to show that the Carnot value is the least likely efficiency in the long time limit.
- Gatien Verley
- , Massimiliano Esposito
- & Christian Van den Broeck
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Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina
There has been a great deal of interest in single-atom heterogeneous catalysis recently. Here, the authors show that industrially relevant lanthanum oxide-doped alumina supports are capable of stabilizing atomically dispersed palladium species, which are evaluated for low-temperature carbon monoxide oxidation.
- Eric J. Peterson
- , Andrew T. DeLaRiva
- & Abhaya K. Datye
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Vibrational coherence probes the mechanism of ultrafast electron transfer in polymer–fullerene blends
Dissociation of excitons at the donor/acceptor interface in organic solar cells occurs on fast timescales. Here, the authors apply two-dimensional electronic spectroscopy to study the electron transfer process in a polymer blend, reporting dynamic maps for the charge-transfer pathways.
- Yin Song
- , Scott N. Clafton
- & Gregory D. Scholes
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| Open AccessPolymer collapse in miscible good solvents is a generic phenomenon driven by preferential adsorption
Smart polymers exhibit a swelling–collapse–swelling transition in mixed (co)solvents and the underlined mechanism remains a matter of debate. Mukherji et al. explain this transition using a generic model based purely on a thermodynamic treatment of preferential polymer–cosolvent interaction.
- Debashish Mukherji
- , Carlos M. Marques
- & Kurt Kremer
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Chemo-mechanics of salt damage in stone
Growth of salt crystals in pores is one of the most damaging weathering mechanisms for stone in ornamental structures and historical buildings. Here, the authors present a simple yet powerful treatment for predicting when salt damage will occur, quantifying this susceptibility to salt crystallization.
- Robert J. Flatt
- , Francesco Caruso
- & George W. Scherer
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| Open AccessEnergy-filtered cold electron transport at room temperature
Electrons can behave as if they are at a temperature different from that of the solid in which they are embedded. Here, the authors demonstrate a room temperature device that can generate electrons with an effective temperature of 45 K by using quantum wells to filter out energetic particles.
- Pradeep Bhadrachalam
- , Ramkumar Subramanian
- & Seong Jin Koh
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Pressure-stabilized lithium caesides with caesium anions beyond the −1 state
In chemical compounds, alkali metal ions typically assume a positive oxidation state where they lose an electron, and only rarely are in a charge state where they receive an electron. Here, the authors predict lithium cesides with oxidation states where caesium receives more than one electron.
- Jorge Botana
- & Mao-Sheng Miao
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Evidence of Stranski–Krastanov growth at the initial stage of atmospheric water condensation
Water condensation on surfaces occurs in nature everywhere, but the study of its initial stage at ambient conditions is very challenging. Here, Song et al.address this issue using thermal controlled atomic force microscopy and identify a mixture of layer-by-layer and island-like modes.
- Jie Song
- , Qiang Li
- & Mingdong Dong
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Diffraction using laser-driven broadband electron wave packets
Developments in ultrafast optical science bring the promise of being able to directly monitor atomic motions during various physical processes. Towards this end, Xu et al.present fixed-angle broadband laser-induced electron scattering as a method to image molecular structures from photoelectron spectra.
- Junliang Xu
- , Cosmin I. Blaga
- & Louis F. DiMauro
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A structural signature of liquid fragility
Glass fragility characterises the rate of change in viscosity as a liquid is cooled towards the glass transition temperature. Here, the authors demonstrate via neutron diffraction that the rate at which structural ordering occurs within the melt correlates with kinetic fragility in a range of metallic glass samples.
- N. A. Mauro
- , M. Blodgett
- & K. F. Kelton
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| Open AccessFrom molecular spectra to a density shift in dense Rydberg gases
Ultracold Rydberg atoms — atoms with highly excited electrons — can form molecules with ground state atoms. By tuning the principal quantum number of the Rydberg state, Gaj et al.study the transition from resolvable molecular lines to the mean shift regime, where indistinguishable lines form a band.
- A. Gaj
- , A. T. Krupp
- & T. Pfau
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Anisotropic thermal conductivity in uranium dioxide
Uranium dioxide fuels the world’s nuclear-power reactors, and so a full understanding of its thermal properties is essential. Gofryk et al. now demonstrate that, despite its cubic atomic structure, the thermal conductivity of uranium dioxide is anisotropic owing to phonon-spin scattering.
- K. Gofryk
- , S. Du
- & D. A. Andersson
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Stabilizing colloidal crystals by leveraging void distributions
It is challenging to prepare colloidal crystals with long-range order for their applications. Mahynski et al. propose a method to achieve this goal through tailoring energy loss of absorbed polymers in crystal voids to selectively stabilize one crystal structure among its competing polymorphs.
- Nathan A. Mahynski
- , Athanassios Z. Panagiotopoulos
- & Sanat K. Kumar
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Tabletop imaging of structural evolutions in chemical reactions demonstrated for the acetylene cation
Femto-chemistry allows researchers to probe the individual transitions in a molecule during a chemical reaction. Here, the authors show that a relatively simple tabletop experiment is capable of capturing the dynamics of isomerization and fragmentation of the acetylene cation to record a molecular movie.
- Heide Ibrahim
- , Benji Wales
- & François Légaré
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Multiple reentrant glass transitions in confined hard-sphere glasses
Wall–fluid interactions are known to have a large influence on the physics of confined glasses. Here, the authors observe a multiple re-entrant glass transition for a polydisperse hard-sphere system confined between two surfaces, when the wall separation distance is of the order of a few particle diameters.
- Suvendu Mandal
- , Simon Lang
- & Fathollah Varnik
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| Open AccessGrain rotation mediated by grain boundary dislocations in nanocrystalline platinum
Grain rotation is proposed as an active deformation mechanism in nanocrystalline metals at room temperature. Here, during in-situatomic scale experimentation, the authors observe that grains with a size <6 nm deform by coordinated rotation of multiple grains, associated with dislocation climb at grain boundaries.
- Lihua Wang
- , Jiao Teng
- & Xiaodong Han
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Water-induced correlation between single ions imaged at the solid–liquid interface
The organization of ions at solid–liquid interfaces is of interest in many fields, but little information at the nanoscale is available. Here, the authors report atomic-level observations of ordering of ions at surfaces in solutions, which is driven by water instead of the conventional electrostatic correlations.
- Maria Ricci
- , Peter Spijker
- & Kislon Voïtchovsky
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Momentum-resolved hidden-order gap reveals symmetry breaking and origin of entropy loss in URu2Si2
URu2Si2 undergoes a prominent phase transition to an ordered state of unknown nature. Using high-resolution 3D ARPES, Bareille et al. image an abrupt symmetry reconstruction of its heavy-fermion electronic structure that could explain the origin of the ordered state and its missing entropy.
- C. Bareille
- , F. L. Boariu
- & A. F. Santander-Syro
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The key role of vibrational entropy in the phase transitions of dithiazolyl-based bistable magnetic materials
Some organic radicals are diamagnetic at low temperatures but switch to a paramagnetic state at higher temperatures. Vela at al. now present computer simulations that indicate this phase change is a result of vibrational entropy, which causes the radicals to organize into neat stacks.
- Sergi Vela
- , Fernando Mota
- & Jordi Ribas-Arino
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Casimir–Polder interactions in the presence of thermally excited surface modes
It is a huge challenge to measure long-range atom–surface interactions, the Casimir–Polder effects, at elevated temperatures. Here, Laliotis et al.report a spectroscopic measurement on caesium atoms approximately 100 nm away from a hot sapphire surface, influenced by the thermal excitation of surface modes.
- Athanasios Laliotis
- , Thierry Passerat de Silans
- & Daniel Bloch
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Giant negative linear compression positively coupled to massive thermal expansion in a metal–organic framework
Negative linear compressibility in materials is usually accompanied by a thermal contraction upon heating. Here, the authors report a metal organic framework that breaks this rule, exhibiting large intrinsic negative linear compressibility coinciding with strong positive thermal expansion.
- Weizhao Cai
- & Andrzej Katrusiak
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Water clustering on nanostructured iron oxide films
It is not well-understood how nanoscale variations in surface structures impact the ordering of the first few wetting layers on oxide surfaces. Here, the authors employ a model surface, a hydroxylated iron oxide film, which allows direct probing of the impact of hydroxyl groups on the adsorbed water molecules.
- Lindsay R. Merte
- , Ralf Bechstein
- & Flemming Besenbacher
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Femtosecond X-ray-induced explosion of C60 at extreme intensity
Understanding the dynamics of molecules exposed to intense X-ray beams is crucial to ongoing efforts in biomolecular imaging with free-electron lasers. Here, the authors study C60molecules interacting with femtosecond X-ray free-electron laser pulses and present a model based on classical and quantum physics.
- B. F. Murphy
- , T. Osipov
- & N. Berrah
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Single-molecule chemical reaction reveals molecular reaction kinetics and dynamics
Chemical reactions are typically composed of a number of elementary steps, but elucidating these steps is a challenge, particularly in the condensed phase. Here, the authors use quantum chemical calculations and single-molecule spectroscopy to unravel the details of a reversible redox process.
- Yuwei Zhang
- , Ping Song
- & Weilin Xu
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| Open AccessEncapsulation kinetics and dynamics of carbon monoxide in clathrate hydrate
Carbon monoxide clathrate hydrate has been widely studied and although the structure-II gas hydrate is predicted to be thermodynamically favourable, it is the structure-I hydrate that has been observed. Here, the authors synthesize the structure-II carbon monoxide hydrate and probe its structure and formation.
- Jinlong Zhu
- , Shiyu Du
- & Yusheng Zhao
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Interfacial mobility scale determines the scale of collective motion and relaxation rate in polymer films
Interfacial mobility in thin polymer films is crucial for their technological applications. Here, Hanakata et al.provide computational evidence for a general relationship between the scale of interfacial mobility and collective motion within the films, which explains their glass transition behaviour.
- Paul Z. Hanakata
- , Jack F. Douglas
- & Francis W. Starr
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Direct observation of spin-forbidden transitions through the use of suitably polarized light
The study of excited triplet states in molecular systems is in some cases hindered by the difficulty in accessing them and the intense signals of singlet states. Here, the authors show that the combination of polarized light and molecular alignment can enhance the triplet absorption for sulphur dioxide.
- Camille Lévêque
- , Daniel Peláez
- & Richard Taïeb
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Isolation and reversible dimerization of a selenium–selenium three-electron σ-bond
Three-electron σ-bonds are known as intermediates in chemical reactions, but they typically are unstable and transient. Here, the authors observe, isolate and characterize a room-temperature-stable organic compound with a three-electron selenium–selenium σ-bond.
- Senwang Zhang
- , Xingyong Wang
- & Xinping Wang
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Collective fluorescence switching of counterion-assembled dyes in polymer nanoparticles
Fluorescent organic nanoparticles are attractive alternatives to quantum dots for imaging applications. Here, the authors assemble dyes with bulky counterions inside polymer nanoparticles to achieve high fluorescence brightness, as well as a photoinducible and reversible on/off switching.
- Andreas Reisch
- , Pascal Didier
- & Andrey S. Klymchenko
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Roaming dynamics in radical addition–elimination reactions
Roaming dynamics have been shown to be important in unimolecular decompositions, but the relevance to bimolecular reactions has been less clear. Here, the authors study radical addition/elimination reactions and implicate a roaming transition state in a bimolecular reaction.
- Baptiste Joalland
- , Yuanyuan Shi
- & Alexander M. Mebel
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Extreme surface propensity of halide ions in water
The surface chemistry of aqueous solutions plays a ubiquitous role in many chemical and biological processes. Here, the authors probe the surfaces of sodium halide solutions with surface-specific femtosecond vibrational spectroscopy, and observe surface concentrations of halide ions several times greater than in the bulk.
- Lukasz Piatkowski
- , Zhen Zhang
- & Mischa Bonn
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Electrochemically tunable thermal conductivity of lithium cobalt oxide
Materials with variable and reversible thermal conductivities are important in technologies, and yet such materials are rare. Here, Cho et al. report in situmeasurements of thermal conductivity of lithium cobalt oxide, and show how to reversibly modulate thermal conductivities over a considerable range.
- Jiung Cho
- , Mark D. Losego
- & Paul V. Braun
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Nanotechnology makes biomass electrolysis more energy efficient than water electrolysis
Electrolytic water splitting requires high electrical energy consumption. Here, the authors report a new type of electrolyser that thanks to palladium-doped titania nanotubes oxidizes bio-alcohols, resulting in energy-convenient hydrogen generation as well as valuable chemical production.
- Y. X. Chen
- , A. Lavacchi
- & F. Vizza
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Oxidation-assisted ductility of aluminium nanowires
The mechanical properties of small volumes are often studied but rarely are the effects of surface oxidation considered. Here, the authors perform a simulation of an aluminium nanowire with an oxide shell deforming in oxygen, finding that the oxide demonstrates superplastic deformation under load.
- Fatih G. Sen
- , Ahmet T. Alpas
- & Yue Qi
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An unconventional bilayer ice structure on a NaCl(001) film
The complication of water adsorption on surfaces goes well beyond a simple hexagonal bilayer model predicted by the ice rule. Chen et al.observe an extended cyclical pattern of water tetramers on an insulator surface, which is attributable to the formation of periodic Bjerrum defects at high density.
- Ji Chen
- , Jing Guo
- & En-Ge Wang
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| Open AccessMapping the force field of a hydrogen-bonded assembly
Hydrogen bonding is an important force in nature, directing and controlling the assembly of numerous natural and synthetic structures. Here the authors show that the interpretation of intermolecular contrast in atomic force microscope images of hydrogen-bonded assemblies necessitates detailed consideration of the coupled tip-molecule system.
- A. M. Sweetman
- , S. P. Jarvis
- & P. Moriarty
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An electrochemical system for efficiently harvesting low-grade heat energy
Thermoelectric devices can convert low-grade heat sources into electricity, but suffer from low efficiency. Here, Lee et al.present a thermally regenerative electrochemical device with copper hexacyanoferrate electrode material, which enables efficient heat-to-electricity energy conversion.
- Seok Woo Lee
- , Yuan Yang
- & Yi Cui
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Enolate chemistry with anion–π interactions
Interactions between anions and π-systems are possible with electron-poor aromatic surfaces. Here the authors show that anion-π interactions can stabilize enolates—lowering the pKa of the carbonyl compound by almost two units—and likewise accelerate the addition of enolates to electrophiles.
- Yingjie Zhao
- , Naomi Sakai
- & Stefan Matile
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Cold ablation driven by localized forces in alkali halides
Cold laser material processing has relied on the use of high-peak-power lasers in order to reach the universal threshold for plasma formation of ~1 J cm−2in most solids. Here, the authors show a cold ablation process that takes off below both the threshold for plasma formation and that of the melting point of alkali halides.
- Masaki Hada
- , Dongfang Zhang
- & R.J. Dwayne Miller
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Desorption kinetics from a surface derived from direct imaging of the adsorbate layer
Desorption kinetics cannot be simply described by the standard method, the temperature-programmed desorption. Here, Günther et al.use low-energy electron microscopy to image an adsorbate layer during desorption, and propose a model that quantitatively explains the complex desorption process.
- S. Günther
- , T. O. Menteş
- & J. Wintterlin
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Solvent-induced immiscibility of polymer brushes eliminates dissipation channels
Interdigitation between polymer brushes decorated on two sliding surfaces induces low friction, which needs to be minimized for bio-lubricant applications. Here the authors show that this friction can be substantially reduced in the systems where immiscible polymer brushes are in contact.
- Sissi de Beer
- , Edit Kutnyanszky
- & Martin H. Müser