Showing papers in "Nature Communications in 2014"
TL;DR: Experimental evidence is presented that the threshold pressure of ~120 GPa induces in molecular ammonia the process of autoionization to yet experimentally unknown ionic compound--ammonium amide, opening new possibilities for studying molecular interactions in hydrogen-bonded systems.
Abstract: Ionization of highly compressed ammonia has previously been predicted by computation. Here, the authors provide experimental evidence for this autoionization process at high pressures, showing the transformation of molecular ammonia into ammonium amide.
3,638 citations
TL;DR: A detailed theoretical investigation of the atomic and electronic structure of few-layer black phosphorus (BP) is presented to predict its electrical and optical properties, finding that the mobilities are hole-dominated, rather high and highly anisotropic.
Abstract: Two-dimensional crystals are emerging materials for nanoelectronics. Development of the field requires candidate systems with both a high carrier mobility and, in contrast to graphene, a sufficiently large electronic bandgap. Here we present a detailed theoretical investigation of the atomic and electronic structure of few-layer black phosphorus (BP) to predict its electrical and optical properties. This system has a direct bandgap, tunable from 1.51 eV for a monolayer to 0.59 eV for a five-layer sample. We predict that the mobilities are hole-dominated, rather high and highly anisotropic. The monolayer is exceptional in having an extremely high hole mobility (of order 10,000 cm(2) V(-1) s(-1)) and anomalous elastic properties which reverse the anisotropy. Light absorption spectra indicate linear dichroism between perpendicular in-plane directions, which allows optical determination of the crystalline orientation and optical activation of the anisotropic transport properties. These results make few-layer BP a promising candidate for future electronics.
3,622 citations
TL;DR: The data suggest that radiomics identifies a general prognostic phenotype existing in both lung and head-and-neck cancer, which may have a clinical impact as imaging is routinely used in clinical practice, providing an unprecedented opportunity to improve decision-support in cancer treatment at low cost.
Abstract: Human cancers exhibit strong phenotypic differences that can be visualized noninvasively by medical imaging. Radiomics refers to the comprehensive quantification of tumour phenotypes by applying a large number of quantitative image features. Here we present a radiomic analysis of 440 features quantifying tumour image intensity, shape and texture, which are extracted from computed tomography data of 1,019 patients with lung or head-and-neck cancer. We find that a large number of radiomic features have prognostic power in independent data sets of lung and head-and-neck cancer patients, many of which were not identified as significant before. Radiogenomics analysis reveals that a prognostic radiomic signature, capturing intratumour heterogeneity, is associated with underlying gene-expression patterns. These data suggest that radiomics identifies a general prognostic phenotype existing in both lung and head-and-neck cancer. This may have a clinical impact as imaging is routinely used in clinical practice, providing an unprecedented opportunity to improve decision-support in cancer treatment at low cost.
3,473 citations
TL;DR: The proposed approach drastically reduces the coherence time requirements and combines this method with a new approach to state preparation based on ansätze and classical optimization, enhancing the potential of quantum resources available today and in the near future.
Abstract: Quantum computers promise to efficiently solve important problems that are intractable on a conventional computer. For quantum systems, where the physical dimension grows exponentially, finding the eigenvalues of certain operators is one such intractable problem and remains a fundamental challenge. The quantum phase estimation algorithm efficiently finds the eigenvalue of a given eigenvector but requires fully coherent evolution. Here we present an alternative approach that greatly reduces the requirements for coherent evolution and combine this method with a new approach to state preparation based on ansatze and classical optimization. We implement the algorithm by combining a highly reconfigurable photonic quantum processor with a conventional computer. We experimentally demonstrate the feasibility of this approach with an example from quantum chemistry--calculating the ground-state molecular energy for He-H(+). The proposed approach drastically reduces the coherence time requirements, enhancing the potential of quantum resources available today and in the near future.
3,114 citations
TL;DR: Black phosphorus (BP), the most stable allotrope of phosphorus with strong intrinsic in-plane anisotropy, is reintroduced to the layered-material family and shows great potential for thin-film electronics, infrared optoelectronics and novel devices in which anisotropic properties are desirable.
Abstract: The applications of graphene and transition metal dichalcogenides in electronics are limited by their zero-bandgap and low mobility, respectively. Here, the authors demonstrate the potential of an emerging layered material—black phosphorous—for thin film electronics and infrared optoelectronics.
2,983 citations
TL;DR: The uncovered aggregation and design rules yield three high-efficiency (>10%) donor polymers and will allow further synthetic advances and matching of both the polymer and fullerene materials, potentially leading to significantly improved performance and increased design flexibility.
Abstract: Although the field of polymer solar cell has seen much progress in device performance in the past few years, several limitations are holding back its further development For instance, current high-efficiency (>90%) cells are restricted to material combinations that are based on limited donor polymers and only one specific fullerene acceptor Here we report the achievement of high-performance (efficiencies up to 108%, fill factors up to 77%) thick-film polymer solar cells for multiple polymer:fullerene combinations via the formation of a near-ideal polymer:fullerene morphology that contains highly crystalline yet reasonably small polymer domains This morphology is controlled by the temperature-dependent aggregation behaviour of the donor polymers and is insensitive to the choice of fullerenes The uncovered aggregation and design rules yield three high-efficiency (>10%) donor polymers and will allow further synthetic advances and matching of both the polymer and fullerene materials, potentially leading to significantly improved performance and increased design flexibility
2,839 citations
TL;DR: The trap states on the surface and grain boundaries of the perovskite materials are demonstrated to be the origin of photocurrent hysteresis and that the fullerene layers deposited onperovskites can effectively passivate these charge trap states and eliminate the notorious photocurrent Hysteresi.
Abstract: The large photocurrent hysteresis observed in many organometal trihalide perovskite solar cells has become a major hindrance impairing the ultimate performance and stability of these devices, while its origin was unknown. Here we demonstrate the trap states on the surface and grain boundaries of the perovskite materials to be the origin of photocurrent hysteresis and that the fullerene layers deposited on perovskites can effectively passivate these charge trap states and eliminate the notorious photocurrent hysteresis. Fullerenes deposited on the top of the perovskites reduce the trap density by two orders of magnitude and double the power conversion efficiency of CH(3)NH(3)PbI(3) solar cells. The elucidation of the origin of photocurrent hysteresis and its elimination by trap passivation in perovskite solar cells provides important directions for future enhancements to device efficiency.
2,440 citations
TL;DR: The results indicate that with proper device interface design, perovskite materials are promising candidates for low-cost, high-performance photodetectors.
Abstract: Organic–inorganic hybrid perovskite materials are attracting great interest for their applications in photovoltaics where they have demonstrated excellent efficiency. Here, Dou et al. demonstrate room temperature, solution-processed hybrid perovskite photodetectors with fast response and high detectivity.
2,086 citations
Journal Article•
2,042 citations
TL;DR: This work demonstrates the promising catalytic activity of single-layered double hydroxides for the oxygen evolution reaction and reports an orthogonal approach to improve the activity of catalysts without alternating their compositions or structures.
Abstract: The oxygen evolution reaction is a key reaction in water splitting. The common approach in the development of oxygen evolution catalysts is to search for catalytic materials with new and optimized chemical compositions and structures. Here we report an orthogonal approach to improve the activity of catalysts without alternating their compositions or structures. Specifically, liquid phase exfoliation is applied to enhance the oxygen evolution activity of layered double hydroxides. The exfoliated single-layer nanosheets exhibit significantly higher oxygen evolution activity than the corresponding bulk layered double hydroxides in alkaline conditions. The nanosheets from nickel iron and nickel cobalt layered double hydroxides outperform a commercial iridium dioxide catalyst in both activity and stability. The exfoliation creates more active sites and improves the electronic conductivity. This work demonstrates the promising catalytic activity of single-layered double hydroxides for the oxygen evolution reaction.
1,816 citations
TL;DR: This work couple graphitic-carbon nitride with nitrogen-doped graphene to produce a metal-free hybrid catalyst, which shows an unexpected hydrogen evolution reaction activity with comparable overpotential and Tafel slope to some of well-developed metallic catalysts.
Abstract: Electrocatalytic reduction of water to molecular hydrogen via the hydrogen evolution reaction may provide a sustainable energy supply for the future, but its commercial application is hampered by the use of precious platinum catalysts. All alternatives to platinum thus far are based on nonprecious metals, and, to our knowledge, there is no report about a catalyst for electrocatalytic hydrogen evolution beyond metals. Here we couple graphitic-carbon nitride with nitrogen-doped graphene to produce a metal-free hybrid catalyst, which shows an unexpected hydrogen evolution reaction activity with comparable overpotential and Tafel slope to some of well-developed metallic catalysts. Experimental observations in combination with density functional theory calculations reveal that its unusual electrocatalytic properties originate from an intrinsic chemical and electronic coupling that synergistically promotes the proton adsorption and reduction kinetics.
TL;DR: By utilizing dual excitation of plasmons at metal-fluid interface, this work creates interacting assemblies of metal nanoparticles, which may be further harnessed in dynamic lithography of dispersed nanostructures and have implications in realizing optically addressable, plasmofluidic, single-molecule detection platforms.
Abstract: Single-molecule surface-enhanced Raman scattering (SM-SERS) is one of the vital applications of plasmonic nanoparticles. The SM-SERS sensitivity critically depends on plasmonic hot-spots created at the vicinity of such nanoparticles. In conventional fluid-phase SM-SERS experiments, plasmonic hot-spots are facilitated by chemical aggregation of nanoparticles. Such aggregation is usually irreversible, and hence, nanoparticles cannot be re-dispersed in the fluid for further use. Here, we show how to combine SM-SERS with plasmon polariton-assisted, reversible assembly of plasmonic nanoparticles at an unstructured metal–fluid interface. One of the unique features of our method is that we use a single evanescent-wave optical excitation for nanoparticle assembly, manipulation and SM-SERS measurements. Furthermore, by utilizing dual excitation of plasmons at metal–fluid interface, we create interacting assemblies of metal nanoparticles, which may be further harnessed in dynamic lithography of dispersed nanostructures. Our work will have implications in realizing optically addressable, plasmofluidic, single-molecule detection platforms. Plasmonic hot-spot generation in solution is not reversible for single-molecule surface-enhanced Raman scattering, which limits its applications. Patra et al.tackle this problem by integrating this technique with thermo-plasmon-assisted reconfiguration of nanoparticles at a metal–fluid interface.
TL;DR: An efficient, low-cost fabrication strategy to construct a highly sensitive, flexible pressure sensor by sandwiching ultrathin gold nanowire-impregnated tissue paper between two thin polydimethylsiloxane sheets is reported, enabling facile large-area integration and patterning for mapping spatial pressure distribution.
Abstract: Flexible electronics hold great promise for wearable biomedical sensors. Here, the authors report a pressure sensor composed of gold nanowire-impregnated tissue paper, sandwiched between polydimethylsiloxane sheets, and demonstrate that the design is appropriate for large-area flexible electronics.
TL;DR: With the discovery of hexagonal boron nitride as an ideal dielectric, the materials are now in place to advance integrated flexible nanoelectronics, which uniquely take advantage of the unmatched portfolio of properties of two-dimensional crystals, beyond the capability of conventional thin films for ubiquitous flexible systems.
Abstract: The unique electrical, mechanical and physical properties of two-dimensional materials make them attractive candidates in flexible nanoelectronic systems. Here Akinwande et al. review the literature on two-dimensional materials in flexible nanoelectronics, and highlight barriers to their full implementation.
TL;DR: Development of an approach and corresponding material structure for solar steam generation while maintaining low optical concentration and keeping the bulk liquid at low temperature with no vacuum, which provides a novel approach to harvesting solar energy for a broad range of phase-change applications.
Abstract: Currently, steam generation using solar energy is based on heating bulk liquid to high temperatures. This approach requires either costly high optical concentrations leading to heat loss by the hot bulk liquid and heated surfaces or vacuum. New solar receiver concepts such as porous volumetric receivers or nanofluids have been proposed to decrease these losses. Here we report development of an approach and corresponding material structure for solar steam generation while maintaining low optical concentration and keeping the bulk liquid at low temperature with no vacuum. We achieve solar thermal efficiency up to 85% at only 10 kW m(-2). This high performance results from four structure characteristics: absorbing in the solar spectrum, thermally insulating, hydrophilic and interconnected pores. The structure concentrates thermal energy and fluid flow where needed for phase change and minimizes dissipated energy. This new structure provides a novel approach to harvesting solar energy for a broad range of phase-change applications.
TL;DR: Optical spectroscopy is used to estimate the exciton binding energy in the mixed-halide crystal to be in the range of 50 meV, and it is shown that such a value is consistent with almost full ionization of the excitonic population under photovoltaic cell operating conditions.
Abstract: Excitonic solar cells, within which bound electron-hole pairs have a central role in energy harvesting, have represented a hot field of research over the last two decades due to the compelling prospect of low-cost solar energy. However, in such cells, exciton dissociation and charge collection occur with significant losses in energy, essentially due to poor charge screening. Organic-inorganic perovskites show promise for overcoming such limitations. Here, we use optical spectroscopy to estimate the exciton binding energy in the mixed-halide crystal to be in the range of 50 meV. We show that such a value is consistent with almost full ionization of the exciton population under photovoltaic cell operating conditions. However, increasing the total photoexcitation density, excitonic species become dominant, widening the perspective of this material for a host of optoelectronic applications.
TL;DR: A one-step, scalable approach for producing and patterning porous graphene films with 3-dimensional networks from commercial polymer films using a CO2 infrared laser to provide a rapid route to polymer-written electronic and energy storage devices.
Abstract: The straightforward and scalable synthesis and patterning of graphene-based nanomaterials remains a technological challenge. Here, the authors use a CO2 infrared laser, under ambient conditions, to directly produce and pattern porous graphene films with three-dimensional networks from commercial polymer films.
TL;DR: Expanded graphite is reported as a Na-ion battery anode, prepared through a process of oxidation and partial reduction on graphite, which has an enlarged interlayer lattice distance yet retains an analogous long-range-ordered layered structure to graphite.
Abstract: Graphite, as the most common anode for commercial Li-ion batteries, has been reported to have a very low capacity when used as a Na-ion battery anode. It is well known that electrochemical insertion of Na(+) into graphite is significantly hindered by the insufficient interlayer spacing. Here we report expanded graphite as a Na-ion battery anode. Prepared through a process of oxidation and partial reduction on graphite, expanded graphite has an enlarged interlayer lattice distance of 4.3 A yet retains an analogous long-range-ordered layered structure to graphite. In situ transmission electron microscopy has demonstrated that the Na-ion can be reversibly inserted into and extracted from expanded graphite. Galvanostatic studies show that expanded graphite can deliver a high reversible capacity of 284 mAh g(-1) at a current density of 20 mA g(-1), maintain a capacity of 184 mAh g(-1) at 100 mA g(-1), and retain 73.92% of its capacity after 2,000 cycles.
TL;DR: The versatility and flexibility of the developed bioprinting process using tissue-specific dECM bioinks, including adipose, cartilage and heart tissues, capable of providing crucial cues for cells engraftment, survival and long-term function are shown.
Abstract: The ability to print and pattern all the components that make up a tissue (cells and matrix materials) in three dimensions to generate structures similar to tissues is an exciting prospect of bioprinting. However, the majority of the matrix materials used so far for bioprinting cannot represent the complexity of natural extracellular matrix (ECM) and thus are unable to reconstitute the intrinsic cellular morphologies and functions. Here, we develop a method for the bioprinting of cell-laden constructs with novel decellularized extracellular matrix (dECM) bioink capable of providing an optimized microenvironment conducive to the growth of three-dimensional structured tissue. We show the versatility and flexibility of the developed bioprinting process using tissue-specific dECM bioinks, including adipose, cartilage and heart tissues, capable of providing crucial cues for cells engraftment, survival and long-term function. We achieve high cell viability and functionality of the printed dECM structures using our bioprinting method.
TL;DR: N nanoscale nickel oxide/nickel heterostructures formed on carbon nanotube sidewalls as highly effective electrocatalysts for hydrogen evolution reaction with activity similar to platinum are reported.
Abstract: There is ongoing research into new electrocatalysts for hydrogen production from water splitting. Here, the authors report the electrocatalytic performance of nickel/nickel oxide heterostructures on carbon nanotubes, and are able to assemble a water electrolyzer operated by a single-cell 1.5 V battery.
TL;DR: In this paper, the authors synthesize graphene analogous with high nitrogen content using a zeolitic imidazolate framework, which shows exceptional battery performances, but the nitrogen content is often quite low.
Abstract: Nitrogen-doped graphene can be used for lithium storage, but the nitrogen content is often quite low. Here, the authors synthesize graphene analogous with high nitrogen content using a zeolitic imidazolate framework, which show exceptional battery performances.
TL;DR: An ultra-sensitive resistive pressure sensor based on an elastic, microstructured conducting polymer thin film that enables the detection of pressures of less than 1Pa and exhibits a short response time, good reproducibility, excellent cycling stability and temperature-stable sensing.
Abstract: Pressure sensing is an important function of electronic skin devices. The development of pressure sensors that can mimic and surpass the subtle pressure sensing properties of natural skin requires the rational design of materials and devices. Here we present an ultra-sensitive resistive pressure sensor based on an elastic, microstructured conducting polymer thin film. The elastic microstructured film is prepared from a polypyrrole hydrogel using a multiphase reaction that produced a hollow-sphere microstructure that endows polypyrrole with structure-derived elasticity and a low effective elastic modulus. The contact area between the microstructured thin film and the electrodes increases with the application of pressure, enabling the device to detect low pressures with ultra-high sensitivity. Our pressure sensor based on an elastic microstructured thin film enables the detection of pressures of less than 1Pa and exhibits a short response time, good reproducibility, excellent cycling stability and temperature-stable sensing.
TL;DR: It is shown that deep-learning methods need no manually constructed inputs and yet improve the classification metric by as much as 8% over the best current approaches, demonstrating that deep learning approaches can improve the power of collider searches for exotic particles.
Abstract: Collisions at high-energy particle colliders are a traditionally fruitful source of exotic particle discoveries. Finding these rare particles requires solving difficult signal-versus-background classification problems, hence machine-learning approaches are often used. Standard approaches have relied on 'shallow' machine-learning models that have a limited capacity to learn complex nonlinear functions of the inputs, and rely on a painstaking search through manually constructed nonlinear features. Progress on this problem has slowed, as a variety of techniques have shown equivalent performance. Recent advances in the field of deep learning make it possible to learn more complex functions and better discriminate between signal and background classes. Here, using benchmark data sets, we show that deep-learning methods need no manually constructed inputs and yet improve the classification metric by as much as 8% over the best current approaches. This demonstrates that deep-learning approaches can improve the power of collider searches for exotic particles.
TL;DR: A three-dimensional holey graphene framework with a hierarchical porous structure as a high-performance binder-free supercapacitor electrode that can deliver gravimetric and volumetric energy densities approaching those of lead acid batteries is reported.
Abstract: Carbon-based materials are promising supercapacitor electrodes, but suffer from limited energy densities. Here, the authors report a holey graphene framework with hierarchical porous structures and fully accessible surface areas, leading to high energy densities comparable to lead-acid batteries.
TL;DR: In-situ transmission electron microscopy and continuum media mechanical calculations are combined to demonstrate that large (>20 μm) mesoporous silicon sponge prepared by the anodization method can limit the particle volume expansion at full lithiation to ~30% and prevent pulverization in bulk silicon particles.
Abstract: Silicon is a promising anode material for lithium ion batteries, but suffers from poor cyclability especially at high mass loading. Here, Li et al. synthesize mesoporous silicon sponge-like structures, which show promising performance at the deep lithiation and high loading conditions required for practical applications.
TL;DR: A nanoporous silver electrocatalyst is reported that is able to electrochemically reduce carbon dioxide to carbon monoxide with approximately 92% selectivity at a rate over 3,000 times higher than its polycrystalline counterpart under moderate overpotentials of <0.50 V.
Abstract: Electrochemical reduction of carbon dioxide to more useful products is an industrially important process. Here, the authors report a nanoporous silver catalyst that efficiently and selectively reduces carbon dioxide due to its high surface area and intrinsically high activity.
TL;DR: The growth of a highly aligned meta-stable structure of 2,7-dioctyl[1]benzothieno[3,2-b][1] Benzothiophene (C8-BTBT) is described from a blended solution of C8- BTBT and polystyrene by using a novel off-centre spin-coating method, indicating their potential for transparent, high-performance organic electronics.
Abstract: One of the advantages of organic over inorganic semiconductors is they can be grown from solution, but their electrical mobility is often poor. Yuan et al. report a technique for fabricating organic transistors with mobilities far beyond that of amorphous silicon and close to that of polycrystalline silicon.
TL;DR: Smart prosthetic skin instrumented with ultrathin, single crystalline silicon nanoribbon strain, pressure and temperature sensor arrays as well as associated humidity sensors, electroresistive heaters and stretchable multi-electrode arrays for nerve stimulation are demonstrated.
Abstract: Sensory receptors in human skin transmit a wealth of tactile and thermal signals from external environments to the brain. Despite advances in our understanding of mechano- and thermosensation, replication of these unique sensory characteristics in artificial skin and prosthetics remains challenging. Recent efforts to develop smart prosthetics, which exploit rigid and/or semi-flexible pressure, strain and temperature sensors, provide promising routes for sensor-laden bionic systems, but with limited stretchability, detection range and spatio-temporal resolution. Here we demonstrate smart prosthetic skin instrumented with ultrathin, single crystalline silicon nanoribbon strain, pressure and temperature sensor arrays as well as associated humidity sensors, electroresistive heaters and stretchable multi-electrode arrays for nerve stimulation. This collection of stretchable sensors and actuators facilitate highly localized mechanical and thermal skin-like perception in response to external stimuli, thus providing unique opportunities for emerging classes of prostheses and peripheral nervous system interface technologies.
TL;DR: This work reports a different strategy based on an inherently polar, high surface area metallic oxide cathode host and shows that it mitigates polysulphide dissolution by forming an excellent interface with Li2S and provides experimental evidence for surface-mediated redox chemistry.
Abstract: In lithium-sulfur batteries, many porous conductive carbon materials are proposed to confine soluble polysulfides, but the efficiency is generally low. Here, the authors use a Magneli phase of titanium oxide as the cathode host and electron conduit, which binds the lithium (poly)sulfides well, leading to excellent battery performance.
TL;DR: This work presents a new PDT agent based on graphene quantum dots (GQDs) that can produce 1O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents.
Abstract: Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen ((1)O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce (1)O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of (1)O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility.