| 1. |
- Alling, Björn, 1980-, et al.
(författare)
-
Questionable collapse of the bulk modulus in CrN
- 2010
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Ingår i: Nature Materials. - London, UK : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 9:4, s. 283-284
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this comment we show that the main conclusion in a previous article, claiminga drastic increase in compressibility of CrN at the cubic to orthorhombic phasetransition, is unsupported by first-principles calculations. We show that if thecubic CrN phase is considered as a disordered magnetic material, as supported bydifferent experimental data, rather then non-magnetic, the bulk modulus is almostunaffected by the transition.
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| 2. |
- Argyriou, Dimitri
(författare)
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Reinventing neutron science in Europe
- 2014
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 13:8, s. 767-768
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Neutron science has been a remarkable success story for European research. For this to continue, scientists need to be prepared to forge new networks and technologies.
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| 3. |
- Babin, Charles, et al.
(författare)
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Fabrication and nanophotonic waveguide integration of silicon carbide colour centres with preserved spin-optical coherence
- 2022
-
Ingår i: Nature Materials. - : NATURE PORTFOLIO. - 1476-1122 .- 1476-4660. ; 21, s. 67-73
-
Tidskriftsartikel (refereegranskat)abstract
- Colour centres are a promising quantum information platform, but coherence degradation after integration in nanostructures has hindered scalability. Here, the authors show that waveguide-integrated V-Si centres in SiC maintain spin-optical coherences, enabling nuclear high-fidelity spin qubit operations. Optically addressable spin defects in silicon carbide (SiC) are an emerging platform for quantum information processing compatible with nanofabrication processes and device control used by the semiconductor industry. System scalability towards large-scale quantum networks demands integration into nanophotonic structures with efficient spin-photon interfaces. However, degradation of the spin-optical coherence after integration in nanophotonic structures has hindered the potential of most colour centre platforms. Here, we demonstrate the implantation of silicon vacancy centres (V-Si) in SiC without deterioration of their intrinsic spin-optical properties. In particular, we show nearly lifetime-limited photon emission and high spin-coherence times for single defects implanted in bulk as well as in nanophotonic waveguides created by reactive ion etching. Furthermore, we take advantage of the high spin-optical coherences of V-Si centres in waveguides to demonstrate controlled operations on nearby nuclear spin qubits, which is a crucial step towards fault-tolerant quantum information distribution based on cavity quantum electrodynamics.
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| 4. |
- Baeumer, Christoph, et al.
(författare)
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Tuning electrochemically driven surface transformation in atomically flat LaNiO3 thin films for enhanced water electrolysis
- 2021
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 20:5, s. 674-682
-
Tidskriftsartikel (refereegranskat)abstract
- Structure–activity relationships built on descriptors of bulk and bulk-terminated surfaces are the basis for the rational design of electrocatalysts. However, electrochemically driven surface transformations complicate the identification of such descriptors. Here we demonstrate how the as-prepared surface composition of (001)-terminated LaNiO3 epitaxial thin films dictates the surface transformation and the electrocatalytic activity for the oxygen evolution reaction. Specifically, the Ni termination (in the as-prepared state) is considerably more active than the La termination, with overpotential differences of up to 150 mV. A combined electrochemical, spectroscopic and density-functional theory investigation suggests that this activity trend originates from a thermodynamically stable, disordered NiO2 surface layer that forms during the operation of Ni-terminated surfaces, which is kinetically inaccessible when starting with a La termination. Our work thus demonstrates the tunability of surface transformation pathways by modifying a single atomic layer at the surface and that active surface phases only develop for select as-synthesized surface terminations.
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| 5. |
- Baranov, Denis, 1990, et al.
(författare)
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Nanophotonic engineering of far-field thermal emitters
- 2019
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 18:9, s. 920-930
-
Forskningsöversikt (refereegranskat)abstract
- Thermal emission is a ubiquitous and fundamental process by which all objects at non-zero temperatures radiate electromagnetic energy. This process is often assumed to be incoherent in both space and time, resulting in broadband, omnidirectional light emission toward the far field, with a spectral density related to the emitter temperature by Planck’s law. Over the past two decades, there has been considerable progress in engineering the spectrum, directionality, polarization and temporal response of thermally emitted light using nanostructured materials. This Review summarizes the basic physics of thermal emission, lays out various nanophotonic approaches to engineer thermal emission in the far field, and highlights several applications, including energy harvesting, lighting and radiative cooling.
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| 6. |
- Berggren, Magnus, 1968-, et al.
(författare)
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Commentary: Organic materials for printed electronics : Editorial in Nature Materials, vol 6, pp 3-5
- 2007
-
Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 6, s. 3-5
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Organic materials can offer a low-cost alternative for printed electronics and flexible displays. However, research in these systems must exploit the differences - via molecular-level control of functionality - compared with inorganic electronics if they are to become commercially viable
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| 7. |
- Berggren, Magnus, 1968-, et al.
(författare)
-
Organic materials for printed electronics
- 2007
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 6:1, s. 3-5
-
Tidskriftsartikel (refereegranskat)abstract
- Organic materials can offer a low-cost alternative for printed electronics and flexible displays. However, research in these systems must exploit the differences — via molecular-level control of functionality — compared with inorganic electronics if they are to become commercially viable. Introduction Conducting and semiconducting organic materials, both polymers and molecules, are being considered for a vast array of electronic applications. The first examples, such as displays in mobile appliances, have found their way to market as replacements for traditional components in existing products. Organic electronics distinguishes itself from traditional electronics because one can define functionality at the molecular level, process the materials from solution, and make displays and circuits that are completely flexible. So far, very little of the uniqueness of organic electronics is expressed in the products promoted as manufacturable; why? One important opportunity for organic electronics is the area of radiofrequency identification (RFID) manufactured using an all-in-line printing process. This technology comprises fast-switching transistors, antennas operating at frequencies above 100 kHz, memory, and so on, all integrated into a plastic foil. The present target in many organic electronics labs around the world is to develop the high-speed (>10 kHz) transistors critical for such devices. The use of organic transistors instead of their inorganic equivalents is motivated by cost. So far, little effort has been devoted to exploring organic electronics in terms of its true unique electronic functionality and the possibility to add electronics to surfaces previously considered electronically inactive. For instance, paper is produced at speeds exceeding 100 km h-1 and is converted into packages and printed media at manufacturing flows typically above 100 m min-1. Adding organic electronics onto, for instance, the paper surface during the paper conversion process would demonstrate the true uniqueness of organic electronics, both from a manufacturing and an application point of view. Retail chains and transportation companies desperately seek a printed electronic technology to provide better safety and security features on packages and automatically track and trace products all the way from the manufacturer to the end customer. The financial losses related to counterfeiting, failure in transportation and damaged packages is comparable to the overall profits made on the product contained in the package. In addition, printed electronics could potentially guide the end-user to properly use the product and to guarantee brand authenticity, for example through an interactive user's guide, and electronic features to replace existing security devices such as the holographic stickers commonly used in packages and bank notes today. It turns out that, for many of these applications, high-frequency signal-processing is not required; 10 ms to 1 s response times are appropriate. These are goals that a very simple printed electronics technology may be able to fill. Silicon-based RFID devices are currently used in high-end products, but are prohibitively expensive for commodities such as food at the consumer package level. Thus, the potential value for printed organic electronics seems to exist if the expense can be kept down. For instance, TetraPak, who produces more than 100 billion packages every year, estimates that the costs for additional security and safety features cannot exceed about 0.2 Eurocents per package (Istvan Ulvros, TetraPak, private communication). Much of the research in organic electronics aims to optimise inherent charge transport and efficiency characteristics of the materials already in use in individual devices. This work has pushed the solar energy-to-electricity power-conversion efficiency in organic solar cells close to 5% (ref. 1) and the luminous efficiency of plastic luminescent devices to around 25 cd A-1 (ref. 2). Organic electrochromic displays now perform extraordinarily well in terms of colour contrast, memory and stability3, and polymer transistors easily run at speeds beyond 100 kHz (ref.4). These results have been achieved by improving the performance at the individual device level. Rarely are integrated circuits or high-volume manufacturing conditions considered in the research. Typically, a series of more than ten patterning, material deposition and post-processing steps are required to make one kind of device. The tradition has been to develop specific materials that exclusively function well in only one device type. RFID circuits (for example) typically require rectifiers, antennas, powering devices, transistors for signal processing, encapsulation layers and in some cases also displays. Merging today's efforts conducted at the organic electronics device level would then result in a production route that would include perhaps 50 (or even more) discrete manufacturing steps. Unfortunately, the cost for a label requiring several tens of patterning steps including exotic organic electronic materials is not compatible with the value and costs of packages. In traditional printers, typically five to ten printing stations are available in series (Fig. 1). Each station also includes one or two convection, infrared or ultraviolet curing steps. At ordinary printing speeds (10 to 200 m min-1) the substrate spends on the order of a tenth to several seconds in each printing station. During this time, registration, material deposition and post-processing must take place. The value structure in printing technology means that the cost for printing scales at least linearly with the number of printing steps. The yield and systematic errors in printing technology becomes a nightmare beyond ten printing steps. The cost for materials such as inks, substrates and coatings is a considerable part of the entire product value. Our own calculations indicate that each individual RFID label would cost more than 10 Eurocents (Lars-Olov Hennerdal, Acreo, private communication).
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| 8. |
- Bourassa, Alexandre, et al.
(författare)
-
Entanglement and control of single nuclear spins in isotopically engineered silicon carbide
- 2020
-
Ingår i: Nature Materials. - : NATURE RESEARCH. - 1476-1122 .- 1476-4660. ; 19:12, s. 1319-1325
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Tidskriftsartikel (refereegranskat)abstract
- Isotope engineering of silicon carbide leads to control of nuclear spins associated with single divacancy centres and extended electron spin coherence. Nuclear spins in the solid state are both a cause of decoherence and a valuable resource for spin qubits. In this work, we demonstrate control of isolated(29)Si nuclear spins in silicon carbide (SiC) to create an entangled state between an optically active divacancy spin and a strongly coupled nuclear register. We then show how isotopic engineering of SiC unlocks control of single weakly coupled nuclear spins and present an ab initio method to predict the optimal isotopic fraction that maximizes the number of usable nuclear memories. We bolster these results by reporting high-fidelity electron spin control (F = 99.984(1)%), alongside extended coherence times (Hahn-echoT(2) = 2.3 ms, dynamical decouplingT(2)(DD) > 14.5 ms), and a >40-fold increase in Ramsey spin dephasing time (T-2*) from isotopic purification. Overall, this work underlines the importance of controlling the nuclear environment in solid-state systems and links single photon emitters with nuclear registers in an industrially scalable material.
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| 9. |
- Boyd, IW, et al.
(författare)
-
The next twenty years
- 2003
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 2:9, s. 563-565
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Tidskriftsartikel (refereegranskat)
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| 10. |
- Bubnova, Olga, et al.
(författare)
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Corrigendum: Semi-metallic polymers
- 2014
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 13, s. 662-662
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Tidskriftsartikel (refereegranskat)
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| 11. |
- Bubnova, Olga, et al.
(författare)
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Optimization of the thermoelectric figure of merit in the conducting polymer poly(3,4-ethylenedioxythiophene)
- 2011
-
Ingår i: NATURE MATERIALS. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 10:6, s. 429-433
-
Tidskriftsartikel (refereegranskat)abstract
- Thermoelectric generators (TEGs) transform a heat flow into electricity. Thermoelectric materials are being investigated for electricity production from waste heat (co-generation) and natural heat sources. For temperatures below 200 degrees C, the best commercially available inorganic semiconductors are bismuth telluride (Bi2Te3)-based alloys, which possess a figure of merit ZT close to one(1). Most of the recently discovered thermoelectric materials with ZT andgt; 2 exhibit one common property, namely their low lattice thermal conductivities(2,3). Nevertheless, a high ZT value is not enough to create a viable technology platform for energy harvesting. To generate electricity from large volumes of warm fluids, heat exchangers must be functionalized with TEGs. This requires thermoelectric materials that are readily synthesized, air stable, environmentally friendly and solution processable to create patterns on large areas. Here we show that conducting polymers might be capable of meeting these demands. The accurate control of the oxidation level in poly(3,4-ethylenedioxythiophene) (PEDOT) combined with its low intrinsic thermal conductivity (lambda = D 0.37W m(-1) K-1) yields a ZT = 0.25 at room temperature that approaches the values required for efficient devices.
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| 12. |
- Bubnova, Olga, et al.
(författare)
-
Semi-metallic polymers
- 2014
-
Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 13:2, s. 190-194
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Tidskriftsartikel (refereegranskat)abstract
- Polymers are lightweight, flexible, solution-processable materials that are promising for low-cost printed electronics as well as for mass-produced and large-area applications. Previous studies demonstrated that they can possess insulating, semiconducting or metallic properties; here we report that polymers can also be semi-metallic. Semi-metals, exemplified by bismuth, graphite and telluride alloys, have no energy bandgap and a very low density of states at the Fermi level. Furthermore, they typically have a higher Seebeck coefficient and lower thermal conductivities compared with metals, thus being suitable for thermoelectric applications. We measure the thermoelectric properties of various poly( 3,4-ethylenedioxythiophene) samples, and observe a marked increase in the Seebeck coefficient when the electrical conductivity is enhanced through molecular organization. This initiates the transition from a Fermi glass to a semi-metal. The high Seebeck value, the metallic conductivity at room temperature and the absence of unpaired electron spins makes polymer semi-metals attractive for thermoelectrics and spintronics.
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| 13. |
- Castelletto, S., et al.
(författare)
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A silicon carbide room-temperature single-photon source
- 2014
-
Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 13:2, s. 151-156
-
Tidskriftsartikel (refereegranskat)abstract
- Over the past few years, single-photon generation has been realized in numerous systems: single molecules(1), quantum dots(2-4), diamond colour centres5 and others(6). The generation and detection of single photons play a central role in the experimental foundation of quantum mechanics(7) and measurement theory(8). An efficient and high-quality single-photon source is needed to implement quantum key distribution, quantum repeaters and photonic quantum information processing(9). Here we report the identification and formation of ultrabright, room-temperature, photostable single-photon sources in a device-friendly material, silicon carbide (SiC). The source is composed of an intrinsic defect, known as the carbon antisite-vacancy pair, created by carefully optimized electron irradiation and annealing of ultrapure SiC. An extreme brightness (2 x 10(6) counts s(-1)) resulting from polarization rules and a high quantum efficiency is obtained in the bulk without resorting to the use of a cavity or plasmonic structure. This may benefit future integrated quantum photonic devices(9).
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| 14. |
- Chang, Guoqing, et al.
(författare)
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Topological quantum properties of chiral crystals
- 2018
-
Ingår i: Nature Materials. - : NATURE PUBLISHING GROUP. - 1476-1122 .- 1476-4660. ; 17:11, s. 978-
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Tidskriftsartikel (refereegranskat)abstract
- Chiral crystals are materials with a lattice structure that has a well-defined handedness due to the lack of inversion, mirror or other roto-inversion symmetries. Although it has been shown that the presence of crystalline symmetries can protect topological band crossings, the topological electronic properties of chiral crystals remain largely uncharacterized. Here we show that Kramers-Weyl fermions are a universal topological electronic property of all non-magnetic chiral crystals with spin-orbit coupling and are guaranteed by structural chirality, lattice translation and time-reversal symmetry. Unlike conventional Weyl fermions, they appear at time-reversal-invariant momenta. We identify representative chiral materials in 33 of the 65 chiral space groups in which Kramers-Weyl fermions are relevant to the low-energy physics. We determine that all point-like nodal degeneracies in non-magnetic chiral crystals with relevant spin-orbit coupling carry non-trivial Chern numbers. Kramers-Weyl materials can exhibit a monopole-like electron spin texture and topologically non-trivial bulk Fermi surfaces over an unusually large energy window.
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| 15. |
- Chen, H., et al.
(författare)
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Unprecedented non-hysteretic superelasticity of [001]-oriented NiCoFeGa single crystals
- 2020
-
Ingår i: Nature Materials. - : Nature Research. - 1476-1122 .- 1476-4660.
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Tidskriftsartikel (refereegranskat)abstract
- Superelasticity associated with the martensitic transformation has found a broad range of engineering applications1,2. However, the intrinsic hysteresis3 and temperature sensitivity4 of the first-order phase transformation significantly hinder the usage of smart metallic components in many critical areas. Here, we report a large superelasticity up to 15.2% strain in [001]-oriented NiCoFeGa single crystals, exhibiting non-hysteretic mechanical responses, a small temperature dependence and high-energy-storage capability and cyclic stability over a wide temperature and composition range. In situ synchrotron X-ray diffraction measurements show that the superelasticity is correlated with a stress-induced continuous variation of lattice parameter accompanied by structural fluctuation. Neutron diffraction and electron microscopy observations reveal an unprecedented microstructure consisting of atomic-level entanglement of ordered and disordered crystal structures, which can be manipulated to tune the superelasticity. The discovery of the large elasticity related to the entangled structure paves the way for exploiting elastic strain engineering and development of related functional materials.
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| 16. |
- Chen, Jianhua, et al.
(författare)
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Highly stretchable organic electrochemical transistors with strain-resistant performance
- 2022
-
Ingår i: Nature Materials. - : NATURE PORTFOLIO. - 1476-1122 .- 1476-4660. ; 21, s. 564-571
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Tidskriftsartikel (refereegranskat)abstract
- Realizing fully stretchable electronic materials is central to advancing new types of mechanically agile and skin-integrable optoelectronic device technologies. Here we demonstrate a materials design concept combining an organic semiconductor film with a honeycomb porous structure with biaxially prestretched platform that enables high-performance organic electrochemical transistors with a charge transport stability over 30-140% tensional strain, limited only by metal contact fatigue. The prestretched honeycomb semiconductor channel of donor-acceptor polymer poly(2,5-bis(2-octyldodecyl)-3,6-di(thiophen-2-yl)-2,5-diketo-pyrrolopyrrole-alt-2,5-bis(3-triethyleneglycoloxy-thiophen-2-yl) exhibits high ion uptake and completely stable electrochemical and mechanical properties over 1,500 redox cycles with 10(4) stretching cycles under 30% strain. Invariant electrocardiogram recording cycles and synapse responses under varying strains, along with mechanical finite element analysis, underscore that the present stretchable organic electrochemical transistor design strategy is suitable for diverse applications requiring stable signal output under deformation with low power dissipation and mechanical robustness. Highly stretchable organic electrochemical transistors with stable charge transport under severe tensional strains are demonstrated using a honeycomb semiconducting polymer morphology, thereby enabling controllable signal output for diverse stretchable bioelectronic applications.
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| 17. |
- Chen, Yang, et al.
(författare)
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Compact spin-valley-locked perovskite emission
- 2023
-
Ingår i: Nature Materials. - : NATURE PORTFOLIO. - 1476-1122 .- 1476-4660.
-
Tidskriftsartikel (refereegranskat)abstract
- Circularly polarized light sources with free-space directional emission play a key role in chiroptics(1), spintronics(2), valleytronics(3) and asymmetric photocatalysis(4). However, conventional approaches fail to simultaneously realize pure circular polarization, high directionality and large emission angles in a compact emitter. Metal-halide perovskite semiconductors are promising light emitters(5-8), but the absence of an intrinsic spin-locking mechanism results in poor emission chirality. Further, device integration has undermined the efficiency and directionality of perovskite chiral emitters. Here we realize compact spin-valley-locked perovskite emitting metasurfaces where spin-dependent geometric phases are imparted into bound states in the continuum via Brillouin zone folding, and thus, photons with different spins are selectively addressed to opposite valleys. Employing this approach, chiral purity of 0.91 and emission angle of 41.0 degrees are simultaneously achieved, with a beam divergence angle of 1.6 degrees. With this approach, we envisage the realization of chiral light- emitting diodes, as well as the on-chip generation of entangled photon pairs.
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| 18. |
- Christle, David J., et al.
(författare)
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Isolated electron spins in silicon carbide with millisecond coherence times
- 2015
-
Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 14:2, s. 160-163
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Tidskriftsartikel (refereegranskat)abstract
- The elimination of defects from SiC has facilitated its move to the forefront of the optoelectronics and power-electronics industries(1). Nonetheless, because certain SiC defects have electronic states with sharp optical and spin transitions, they are increasingly recognized as a platform for quantum information and nanoscale sensing(2-16). Here, we show that individual electron spins in high-purity monocrystalline 4H-SiC can be isolated and coherently controlled. Bound to neutral divacancy defects(2,3), these states exhibit exceptionally long ensemble Hahn-echo spin coherence times, exceeding 1 ms. Coherent control of single spins in a material amenable to advanced growth and microfabrication techniques is an exciting route towards wafer-scale quantum technologies.
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| 19. |
- Corbae, Paul, et al.
(författare)
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Observation of spin-momentum locked surface states in amorphous Bi2Se3
- 2023
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 22:2, s. 200-206
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Tidskriftsartikel (refereegranskat)abstract
- Crystalline symmetries have played a central role in the identification and understanding of quantum materials. Here we investigate whether an amorphous analogue of a well known three-dimensional strong topological insulator has topological properties in the solid state. We show that amorphous Bi2Se3 thin films host a number of two-dimensional surface conduction channels. Our angle-resolved photoemission spectroscopy data are consistent with a dispersive two-dimensional surface state that crosses the bulk gap. Spin-resolved photoemission spectroscopy shows this state has an anti-symmetric spin texture, confirming the existence of spin-momentum locked surface states. We discuss these experimental results in light of theoretical photoemission spectra obtained with an amorphous topological insulator tight-binding model, contrasting it with alternative explanations. The discovery of spin-momentum locked surface states in amorphous materials opens a new avenue to characterize amorphous matter, and triggers the search for an overlooked subset of quantum materials outside of current classification schemes.
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| 20. |
- Crispin, Xavier, et al.
(författare)
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Semiconducting Polymers : Probing the solid-liquid interface
- 2017
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Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 16:7, s. 704-705
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Exploring the minute mechanical deformations induced by electrical bias at the interface with electrolytes allows the identification of local crystallinity and distinguishing adsorption and intercalation of ions in electroactive polymers.
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| 21. |
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| 22. |
- Dai, Heng, et al.
(författare)
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Finned zeolite catalysts
- 2020
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 19:10, s. 1074-1080
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Tidskriftsartikel (refereegranskat)abstract
- Nanosized zeolites enable better catalytic performance; however, their synthesis is non-trivial. Here, a simple treatment is presented that enables the growth of nanosized fins on zeolites that act as pseudo-nanoparticles, reducing deactivation rates for methanol-to-hydrocarbon catalysis. There is growing evidence for the advantages of synthesizing nanosized zeolites with markedly reduced internal diffusion limitations for enhanced performances in catalysis and adsorption. Producing zeolite crystals with sizes less than 100 nm, however, is non-trivial, often requires the use of complex organics and typically results in a small product yield. Here we present an alternative, facile approach to enhance the mass-transport properties of zeolites by the epitaxial growth of fin-like protrusions on seed crystals. We validate this generalizable methodology on two common zeolites and confirm that fins are in crystallographic registry with the underlying seeds, and that secondary growth does not impede access to the micropores. Molecular modelling and time-resolved titration experiments of finned zeolites probe internal diffusion and reveal substantial improvements in mass transport, consistent with catalytic tests of a model reaction, which show that these structures behave as pseudo-nanocrystals with sizes commensurate to that of the fin. This approach could be extended to the rational synthesis of other zeolite and aluminosilicate materials.
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| 23. |
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| 24. |
- Dick Thelander, Kimberly, et al.
(författare)
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Synthesis of branched 'nanotrees' by controlled seeding of multiple branching events
- 2004
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 3:6, s. 380-384
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Tidskriftsartikel (refereegranskat)abstract
- The formation of nanostructures with controlled size and morphology has been the focus of intensive research in recent years(1-10). Such nanostructures are important in the development of nanoscale devices and in the exploitation of the properties of nanomaterials(9). Here we show how tree-like nanostructures ('nanotrees') can be formed in a highly controlled way. The process involves the self-assembled growth of semiconductor nanowires via the vapour-liquid-solid(11) growth mode. This bottom-up method uses initial seeding by catalytic nanoparticles(12) to form the trunk, followed by the sequential seeding of branching structures. Each level of branching is controlled in terms of branch length, diameter and number, as well as chemical composition. We show, by high-resolution transmission electron microscopy, that the branching mechanism gives continuous crystalline (monolithic) structures throughout the extended and complex tree-like structures. The controlled seeding method that we report here has potential as a generic means of forming complex branching structures, and may also offer opportunities for applications, such as the mimicking of photosynthesis in nanotrees.
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| 25. |
- Dou, Jin-Hu, et al.
(författare)
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Atomically precise single-crystal structures of electrically conducting 2D metal-organic frameworks
- 2021
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 20, s. 222-228
-
Tidskriftsartikel (refereegranskat)abstract
- Electrically conducting 2D metal-organic frameworks (MOFs) have attracted considerable interest, as their hexagonal 2D lattices mimic graphite and other 2D van der Waals stacked materials. However, understanding their intrinsic properties remains a challenge because their crystals are too small or of too poor quality for crystal structure determination. Here, we report atomically precise structures of a family of 2D pi-conjugated MOFs derived from large single crystals of sizes up to 200 mu m, allowing atomic-resolution analysis by a battery of high-resolution diffraction techniques. A designed ligand core rebalances the in-plane and out-of-plane interactions that define anisotropic crystal growth. We report two crystal structure types exhibiting analogous 2D honeycomb-like sheets but distinct packing modes and pore contents. Single-crystal electrical transport measurements distinctively demonstrate anisotropic transport normal and parallel to the pi-conjugated sheets, revealing a clear correlation between absolute conductivity and the nature of the metal cation and 2D sheet packing motif. Two-dimensional MOFs can possess porosity and electrical conductivity but are difficult to grow as single crystals. Here, by balancing in-plane and out-of-plane interactions, single crystals of sizes up to 200 mu m are grown, allowing in-plane transport measurements and atomic-resolution analysis.
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| 26. |
- Dziawa, P., et al.
(författare)
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Topological crystalline insulator states in Pb1-xSnxSe
- 2012
-
Ingår i: Nature Materials. - 1476-1122 .- 1476-4660. ; 11:12, s. 1023-1027
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Tidskriftsartikel (refereegranskat)abstract
- Topological insulators are a class of quantum materials in which time-reversal symmetry, relativistic effects and an inverted band structure result in the occurrence of electronic metallic states on the surfaces of insulating bulk crystals. These helical states exhibit a Dirac-like energy dispersion across the bulk bandgap, and they are topologically protected. Recent theoretical results have suggested the existence of topological crystalline insulators (TCIs), a class of topological insulators in which crystalline symmetry replaces the role of time-reversal symmetry in ensuring topological protection(1,2). In this study we show that the narrow-gap semiconductor Pb1-xSnxSe is a TCI for x = 0.23. Temperature-dependent angle-resolved photoelectron spectroscopy demonstrates that the material undergoes a temperature-driven topological phase transition from a trivial insulator to a TCI. These experimental findings add a new class to the family of topological insulators, and we anticipate that they will lead to a considerable body of further research as well as detailed studies of topological phase transitions.
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| 27. |
- Edwards, B., et al.
(författare)
-
Giant valleyZeeman coupling in the surface layer of an intercalated transition metal dichalcogenide
- 2023
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 22:4, s. 459-465
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Tidskriftsartikel (refereegranskat)abstract
- Spin–valley locking is ubiquitous among transition metal dichalcogenides with local or global inversion asymmetry, in turn stabilizing properties such as Ising superconductivity, and opening routes towards ‘valleytronics’. The underlying valley–spin splitting is set by spin–orbit coupling but can be tuned via the application of external magnetic fields or through proximity coupling. However, only modest changes have been realized to date. Here, we investigate the electronic structure of the V-intercalated transition metal dichalcogenide V1/3NbS2 using microscopic-area spatially resolved and angle-resolved photoemission spectroscopy. Our measurements and corresponding density functional theory calculations reveal that the bulk magnetic order induces a giant valley-selective Ising coupling exceeding 50 meV in the surface NbS2 layer, equivalent to application of a ~250 T magnetic field. This energy scale is of comparable magnitude to the intrinsic spin–orbit splittings, and indicates how coupling of local magnetic moments to itinerant states of a transition metal dichalcogenide monolayer provides a powerful route to controlling their valley–spin splittings.
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| 28. |
- Elgazzar, S, et al.
(författare)
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Hidden order in URu2Si2 originates from Fermi surface gapping induced by dynamic symmetry breaking
- 2009
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Ingår i: Nature Materials. - 1476-1122 .- 1476-4660. ; 8:4, s. 337-341
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Tidskriftsartikel (refereegranskat)abstract
- Spontaneous, collective ordering of electronic degrees of freedom leads to second-order phase transitions that are characterized by an order parameter driving the transition. The notion of a 'hidden order' has recently been used for a variety of materials where a clear phase transition occurs without a known order parameter. The prototype example is the heavy-fermion compound URu2Si2, where a mysterious hidden-order transition occurs at 17.5 K. For more than twenty years this system has been studied theoretically and experimentally without a firm grasp of the underlying physics. Here, we provide a microscopic explanation of the hidden order using density-functional theory calculations. We identify the Fermi surface 'hot spots' where degeneracy induces a Fermi surface instability and quantify how symmetry breaking lifts the degeneracy, causing a surprisingly large Fermi surface gapping. As the mechanism for the hidden order, we deduce spontaneous symmetry breaking through a dynamic mode of antiferromagnetic moment excitations.
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| 29. |
- Erhart, Paul, 1978, et al.
(författare)
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The Wulff construction goes low-symmetry
- 2023
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 22:8, s. 941-942
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Tidskriftsartikel (refereegranskat)
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| 30. |
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| 31. |
- Eschenlohr, A., et al.
(författare)
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Ultrafast spin transport as key to femtosecond demagnetization
- 2013
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Ingår i: Nature Materials. - 1476-1122 .- 1476-4660. ; 12:4, s. 332-336
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Tidskriftsartikel (refereegranskat)abstract
- Irradiating a ferromagnet with a femtosecond laser pulse is known to induce an ultrafast demagnetization within a few hundred femtoseconds. Here we demonstrate that direct laser irradiation is in fact not essential for ultrafast demagnetization, and that electron cascades caused by hot electron currents accomplish it very efficiently. We optically excite a Au/Ni layered structure in which the 30 nm Au capping layer absorbs the incident laser pump pulse and subsequently use the X-ray magnetic circular dichroism technique to probe the femtosecond demagnetization of the adjacent 15 nm Ni layer. A demagnetization effect corresponding to the scenario in which the laser directly excites the Ni film is observed, but with a slight temporal delay. We explain this unexpected observation by means of the demagnetizing effect of a superdiffusive current of non-equilibrium, non-spin-polarized electrons generated in the Au layer.
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| 32. |
- Fashandi, Hossein, et al.
(författare)
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Synthesis of Ti3AuC2, Ti3Au2C2 and Ti3IrC2 by noble metal substitution reaction in Ti3SiC2 for high-temperature-stable Ohmic contacts to SiC
- 2017
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Ingår i: Nature Materials. - : NATURE PUBLISHING GROUP. - 1476-1122 .- 1476-4660. ; 16:8, s. 814-818
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Tidskriftsartikel (refereegranskat)abstract
- The large class of layered ceramics encompasses both van der Waals (vdW) and non-vdW solids. While intercalation of noble metals in vdW solids is known, formation of compounds by incorporation of noble-metal layers in non-vdW layered solids is largely unexplored. Here, we show formation of Ti3AuC2 and Ti3Au2C2 phases with up to 31% lattice swelling by a substitutional solid-state reaction of Au into Ti3SiC2 single-crystal thin films with simultaneous out-diffusion of Si. Ti3IrC2 is subsequently produced by a substitution reaction of Ir for Au in Ti3Au2C2. These phases form Ohmic electrical contacts to SiC and remain stable after 1,000 h of ageing at 600 degrees C in air. The present results, by combined analytical electron microscopy and ab initio calculations, open avenues for processing of noble-metal-containing layered ceramics that have not been synthesized from elemental sources, along with tunable properties such as stable electrical contacts for high-temperature power electronics or gas sensors.
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| 33. |
- Forsblom, Mattias, et al.
(författare)
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How superheated crystals melt
- 2005
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 4:5, s. 388-390
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Tidskriftsartikel (refereegranskat)abstract
- The melting of superheated crystalline solids through the penetration of intense radiation within at a temperature above the equilibrium melting temperature was investigated. The atomistic simulations, relevant for aluminum, was used to show that the thermal fluctuation initiating melting is an aggregate typically with 6-7 interstitials and 3-4 vacancies. Vacancy-interstital pairs were created through thermal fluctuation and interstitial-vacancy pairs were created close to the interstitial aggregate. It was found that when a defect aggregate contains more than about 10 point defects, it usually grows rapidly and irreversibly.
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| 34. |
- Gambardella, P., et al.
(författare)
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Supramolecular control of the magnetic anisotropy in two-dimensional high-spin Fe arrays at a metal interface
- 2009
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Ingår i: Nature Materials. - 1476-4660 .- 1476-1122. ; 8:3, s. 189-193
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic atoms at surfaces may provide the ultimate paradigm of a solid-state magnetic memory exhibiting either classical , or quantum , behaviour. Individual atoms, however, are difficult to arrange in regular patterns1,2,3,4, . Moreover, their magnetic properties are dominated by interaction with the substrate, which, as in the case of Kondo systems, often leads to a decrease or quench of their local magnetic moment , . Here we show that the supramolecular assembly of Fe and 1,4-benzenedicarboxylic acid molecules on a Cu surface results in ordered arrays of high-spin mononuclear Fe centres on a 1.5 nm square grid. Lateral coordination with the molecular ligands yields unsaturated yet stable coordination bonds, which allow for the chemical modification of the electronic and magnetic properties of the Fe atoms independently from the substrate. The easy magnetization direction of the Fe centres can be switched by oxygen adsorption, thus opening a way to control the magnetic anisotropy in supramolecular layers akin to that employed in metallic thin films , , , .
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| 35. |
- Gözen, Irep, 1980, et al.
(författare)
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Fractal avalanche ruptures in biological membranes
- 2010
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Ingår i: Nature Materials. - 1476-4660 .- 1476-1122. ; 9:11, s. 908-912
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Tidskriftsartikel (refereegranskat)abstract
- Bilayer membranes envelope cells as well as organelles, and constitute the most ubiquitous biological material found in all branches of the phylogenetic tree. Cell membrane rupture is an important biological process, and substantial rupture rates are found in skeletal and cardiac muscle cells under a mechanical load(1). Rupture can also be induced by processes such as cell death(2), and active cell membrane repair mechanisms are essential to preserve cell integrity(3). Pore formation in cell membranes is also at the heart of many biomedical applications such as in drug, gene and short interfering RNA delivery(4). Membrane rupture dynamics has been studied in bilayer vesicles under tensile stress(5-8), which consistently produce circular pores(5,6). We observed very different rupture mechanics in bilayer membranes spreading on solid supports: in one instance fingering instabilities were seen resulting in floral-like pores and in another, the rupture proceeded in a series of rapid avalanches causing fractal membrane fragmentation. The intermittent character of rupture evolution and the broad distribution in avalanche sizes is consistent with crackling-noise dynamics(9). Such noisy dynamics appear in fracture of solid disordered materials(10), in dislocation avalanches in plastic deformations(11) and domain wall magnetization avalanches(12). We also observed similar fractal rupture mechanics in spreading cell membranes.
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| 36. |
- Hamedi, Mahiar, et al.
(författare)
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Towards woven logic from organic electronic fibres
- 2007
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 6:5, s. 357-362
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Tidskriftsartikel (refereegranskat)abstract
- The use of organic polymers for electronic functions is mainly motivated by the low-end applications, where low cost rather than advanced performance is a driving force. Materials and processing methods must allow for cheap production. Printing of electronics using inkjets1 or classical printing methods has considerable potential to deliver this. Another technology that has been around for millennia is weaving using fibres. Integration of electronic functions within fabrics, with production methods fully compatible with textiles, is therefore of current interest, to enhance performance and extend functions of textiles2. Standard polymer field-effect transistors require well defined insulator thickness and high voltage3, so they have limited suitability for electronic textiles. Here we report a novel approach through the construction of wire electrochemical transistor (WECT) devices, and show that textile monofilaments with 10–100 m diameters can be coated with continuous thin films of the conducting polythiophene poly(3,4-ethylenedioxythiophene), and used to create micro-scale WECTs on single fibres. We also demonstrate inverters and multiplexers for digital logic. This opens an avenue for three-dimensional polymer micro-electronics, where large-scale circuits can be designed and integrated directly into the three-dimensional structure of woven fibres.
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| 37. |
- Hou, Jianhui, et al.
(författare)
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Organic solar cells based on non-fullerene acceptors
- 2018
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Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 17:2, s. 119-128
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Forskningsöversikt (refereegranskat)abstract
- Organic solar cells (OSCs) have been dominated by donor: acceptor blends based on fullerene acceptors for over two decades. This situation has changed recently, with non-fullerene (NF) OSCs developing very quickly. The power conversion efficiencies of NF OSCs have now reached a value of over 13%, which is higher than the best fullerene-based OSCs. NF acceptors show great tunability in absorption spectra and electron energy levels, providing a wide range of new opportunities. The coexistence of low voltage losses and high current generation indicates that new regimes of device physics and photophysics are reached in these systems. This Review highlights these opportunities made possible by NF acceptors, and also discuss the challenges facing the development of NF OSCs for practical applications.
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| 38. |
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| 39. |
- Iota, Valentin, et al.
(författare)
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Six-fold coordinated carbon dioxide VI
- 2007
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 6, s. 34-38
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Tidskriftsartikel (refereegranskat)abstract
- Under standard conditions, carbon dioxide (CO2) is a simple molecular gas and an important atmospheric constituent, whereas silicon dioxide (SiO2) is a covalent solid, and one of the fundamental minerals of the planet. The remarkable dissimilarity between these two group IV oxides is diminished at higher pressures and temperatures as CO2 transforms to a series of solid phases, from simple molecular to a fully covalent extended-solid V, structurally analogous to SiO2 tridymite. Here, we present the discovery of an extended-solid phase of CO2: a six-fold coordinated stishovite-like phase VI, obtained by isothermal compression of associated CO2-II (refs 1,2) above 50 GPa at 530–650 K. Together with the previously reported CO2-V (refs 3–5) and a-carbonia6, this extended phase indicates a fundamental similarity between CO2 (a prototypical molecular solid) and SiO2 (one of Earth's fundamental building blocks). We present a phase diagram with a limited stability domain for molecular CO2-I, and suggest that the conversion to extended-network solids above 40–50 GPa occurs via intermediate phases II (refs 1,2), III (refs 7,8) and IV (refs 9,10). The crystal structure of phase VI suggests strong disorder along the c axis in stishovite-like P42/mnm, with carbon atoms manifesting an average six-fold coordination within the framework of sp3 hybridization.
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| 40. |
- Isaksson, Joakim, et al.
(författare)
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Electronic Control of Ca2+ Signalling in Neuronal Cells using an Organic Electronic Ion Pump
- 2007
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 6:9, s. 673-679
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Tidskriftsartikel (refereegranskat)abstract
- Cells and tissues use finely regulated ion fluxes for their intra- and intercellular communication. Technologies providing spatial and temporal control for studies of such fluxes are however, limited. We have developed an electrophoretic ion pump made of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulphonate) (PEDOT:PSS) to mediate electronic control of the ion homeostasis in neurons. Ion delivery from a source reservoir to a receiving electrolyte via a PEDOT:PSS thin-film channel was achieved by electronic addressing. Ions are delivered in high quantities at an associated on/off ratio exceeding 300. This induces physiological signalling events that can be recorded at the single-cell level. Furthermore, miniaturization of the device to a 50-um-wide channel allows for stimulation of individual cells. As this technology platform allows for electronic control of ion signalling in individual cells with proper spatial and temporal resolution, it will be useful in further studies of communication in biological systems.
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| 41. |
- Isberg, Jan, et al.
(författare)
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Generation, transport and detection of valley-polarized electrons in diamond
- 2013
-
Ingår i: Nature Materials. - 1476-1122 .- 1476-4660. ; 12:8, s. 760-764
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Tidskriftsartikel (refereegranskat)abstract
- Standard electronic devices encode bits of information by controlling the amount of electric charge in the circuits. Alternatively, it is possible to make devices that rely on other properties of electrons than their charge. For example, spintronic devices make use of the electron spin angular momentum as a carrier of information. A new concept is valleytronics in which information is encoded by the valley quantum number of the electron. The analogy between the valley and spin degrees of freedom also implies the possibility of valley-based quantum computing. In this Article, we demonstrate for the first time generation, transport ( across macroscopic distances) and detection of valley-polarized electrons in bulk diamond with a relaxation time of 300 ns at 77 K. We anticipate that these results will form the basis for the development of integrated valleytronic devices.
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| 42. |
- Johansson, Jonas, et al.
(författare)
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Structural properties of (111)B-oriented III-V nanowires
- 2006
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 5:7, s. 574-580
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Tidskriftsartikel (refereegranskat)abstract
- Controlled growth of nanowires is an important, emerging research field with many applications in, for example, electronics, photonics, and life sciences. Nanowires of zinc blende crystal structure, grown in the left fence111right fenceB direction, which is the favoured direction of growth, usually have a large number of twin-plane defects. Such defects limit the performance of optoelectronic nanowire-based devices. To investigate this defect formation, we examine GaP nanowires grown by metal-organic vapour-phase epitaxy. We show that the nanowire segments between the twin planes are of octahedral shape and are terminated by {111} facets, resulting in a microfaceting of the nanowires. We discuss these findings in a nucleation context, where we present an idea on how the twin planes form. This investigation contributes to the understanding of defect formation in nanowires. One future prospect of such knowledge is to determine strategies on how to control the crystallinity of nanowires.
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| 43. |
- Jowett, Geraldine M., et al.
(författare)
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ILC1 drive intestinal epithelial and matrix remodelling
- 2021
-
Ingår i: Nature Materials. - : Springer Nature. - 1476-1122 .- 1476-4660. ; 20:2, s. 250-259
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Tidskriftsartikel (refereegranskat)abstract
- Organoids can shed light on the dynamic interplay between complex tissues and rare cell types within a controlled microenvironment. Here, we develop gut organoid cocultures with type-1 innate lymphoid cells (ILC1) to dissect the impact of their accumulation in inflamed intestines. We demonstrate that murine and human ILC1 secrete transforming growth factor β1, driving expansion of CD44v6+ epithelial crypts. ILC1 additionally express MMP9 and drive gene signatures indicative of extracellular matrix remodelling. We therefore encapsulated human epithelial–mesenchymal intestinal organoids in MMP-sensitive, synthetic hydrogels designed to form efficient networks at low polymer concentrations. Harnessing this defined system, we demonstrate that ILC1 drive matrix softening and stiffening, which we suggest occurs through balanced matrix degradation and deposition. Our platform enabled us to elucidate previously undescribed interactions between ILC1 and their microenvironment, which suggest that they may exacerbate fibrosis and tumour growth when enriched in inflamed patient tissues.
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| 44. |
- Kang, Chengjun, et al.
(författare)
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Covalent organic framework atropisomers with multiple gas-triggered structural flexibilities
- 2023
-
Ingår i: Nature Materials. - 1476-1122 .- 1476-4660. ; 22:5, s. 636-643
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Tidskriftsartikel (refereegranskat)abstract
- Covalent organic frameworks (COFs) are emerging crystalline porous polymers, showing great potential for applications but lacking gas-triggered flexibility. Atropisomerism was experimentally discovered in 1922 but has rarely been found in crystals with infinite framework structures. Here we report atropisomerism in COF single crystals. The obtained COF atropisomers, namely COF-320 and COF-320-A, have identical chemical and interpenetrated structures but differ in the spatial arrangement of repeating units. In contrast to the rigid COF-320 structure, its atropisomer (COF-320-A) exhibits unconventional gas sorption behaviours with one or more sorption steps in isotherms at different temperatures. Single-crystal structures determined from continuous rotation electron diffraction and in situ powder X-ray diffraction demonstrate that these adsorption steps originate from internal pore expansion with or without changing the crystal space group. COF-320-A recognizes different gases by expanding its internal pores continuously (crystal-to-amorphous transition) or discontinuously (crystal-to-crystal transition) or having mixed transition styles, distinguishing COF-320-A from existing soft/flexible porous crystals. These findings extend atropisomerism from molecules to crystals and propel COFs into the covalently linked soft porous crystal regime, further advancing applications of soft porous crystals in gas sorption, separation and storage.
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| 45. |
- Kiefer, David, 1989, et al.
(författare)
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Double doping of conjugated polymers with monomer molecular dopants
- 2019
-
Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 18:2, s. 149-155
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Tidskriftsartikel (refereegranskat)abstract
- Molecular doping is a crucial tool for controlling the charge-carrier concentration in organic semiconductors. Each dopant molecule is commonly thought to give rise to only one polaron, leading to a maximum of one donor:acceptor charge-transfer complex and hence an ionization efficiency of 100%. However, this theoretical limit is rarely achieved because of incomplete charge transfer and the presence of unreacted dopant. Here, we establish that common p-dopants can in fact accept two electrons per molecule from conjugated polymers with a low ionization energy. Each dopant molecule participates in two charge-transfer events, leading to the formation of dopant dianions and an ionization efficiency of up to 200%. Furthermore, we show that the resulting integer charge-transfer complex can dissociate with an efficiency of up to 170%. The concept of double doping introduced here may allow the dopant fraction required to optimize charge conduction to be halved.
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| 46. |
- Korzhavyi, Pavel A., et al.
(författare)
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Oxidation of plutonium dioxide
- 2004
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 3:4, s. 225-228
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Tidskriftsartikel (refereegranskat)abstract
- The physics and chemistry of the actinide elements form the scientific basis for rational handling of nuclear materials(1-3). In recent experiments(4), most unexpectedly, plutonium dioxide has been found to react with water to form higher oxides up to PuO2.27, whereas PuO2 had always been thought to be the highest stable oxide of plutonium(2,3). We perform a theoretical analysis of this complicated situation on the basis of total energies calculated within density functional theory(5,6) combined with well-established thermodynamic data. The reactions of PuO2 with either O-2 or H2O to form PuO2+delta are calculated to be endothermic: that is, in order to occur they require a supply of energy. However, our calculations show that PuO2+delta can be formed, as an intermediate product, by reactions with the products of radiolysis of water, such as H2O2.
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| 47. |
- Käll, Mikael, 1963
(författare)
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Plasmonic nanosensors: Inverse sensitivity
- 2012
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 11:7, s. 570-571
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 48. |
- Li, Biao, et al.
(författare)
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Capturing dynamic ligand-to-metal charge transfer with a long-lived cationic intermediate for anionic redox
- 2022
-
Ingår i: Nature Materials. - : Springer Nature. - 1476-1122 .- 1476-4660. ; 21:10, s. 1165-1174
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Tidskriftsartikel (refereegranskat)abstract
- Reversible anionic redox reactions represent a transformational change for creating advanced high-energy-density positive-electrode materials for lithium-ion batteries. The activation mechanism of these reactions is frequently linked to ligand-to-metal charge transfer (LMCT) processes, which have not been fully validated experimentally due to the lack of suitable model materials. Here we show that the activation of anionic redox in cation-disordered rock-salt Li1.17Ti0.58Ni0.25O2 involves a long-lived intermediate Ni3+/4+ species, which can fully evolve to Ni2+ during relaxation. Combining electrochemical analysis and spectroscopic techniques, we quantitatively identified that the reduction of this Ni3+/4+ species goes through a dynamic LMCT process (Ni3+/4+–O2− → Ni2+–On−). Our findings provide experimental validation of previous theoretical hypotheses and help to rationalize several peculiarities associated with anionic redox, such as cationic–anionic redox inversion and voltage hysteresis. This work also provides additional guidance for designing high-capacity electrodes by screening appropriate cationic species for mediating LMCT.
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| 49. |
- Li, Biao, et al.
(författare)
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Decoupling the roles of Ni and Co in anionic redox activity of Li-rich NMC cathodes
- 2023
-
Ingår i: Nature Materials. - : Springer Nature. - 1476-1122 .- 1476-4660. ; 22:11, s. 1370-1379
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Tidskriftsartikel (refereegranskat)abstract
- Li[LixNiyMnzCo1−x−y−z]O2 (lithium-rich NMCs) are benchmark cathode materials receiving considerable attention due to the abnormally high capacities resulting from their anionic redox chemistry. Although their anionic redox mechanisms have been much investigated, the roles of cationic redox processes remain underexplored, hindering further performance improvement. Here we decoupled the effects of nickel and cobalt in lithium-rich NMCs via a comprehensive study of two typical compounds, Li1.2Ni0.2Mn0.6O2 and Li1.2Co0.4Mn0.4O2. We discovered that both Ni3+/4+ and Co4+, generated during cationic redox processes, are actually intermediate species for triggering oxygen redox through a ligand-to-metal charge-transfer process. However, cobalt is better than nickel in mediating the kinetics of ligand-to-metal charge transfer by favouring more transition metal migration, leading to less cationic redox but more oxygen redox, more O2 release, poorer cycling performance and more severe voltage decay. Our work highlights a compositional optimization pathway for lithium-rich NMCs by deviating from using cobalt to using nickel, providing valuable guidelines for future high-capacity cathode design.
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| 50. |
- Li, Youbing, et al.
(författare)
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A general Lewis acidic etching route for preparing MXenes with enhanced electrochemical performance in non-aqueous electrolyte
- 2020
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Ingår i: Nature Materials. - : NATURE PUBLISHING GROUP. - 1476-1122 .- 1476-4660. ; 19:8, s. 894-899
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional transition metal carbides and nitrides, known as MXenes, are currently considered as energy storage materials. A generic Lewis acidic etching route for preparing high-rate negative-electrode MXenes with enhanced electrochemical performance in non-aqueous electrolyte is now proposed. Two-dimensional carbides and nitrides of transition metals, known as MXenes, are a fast-growing family of materials that have attracted attention as energy storage materials. MXenes are mainly prepared from Al-containing MAX phases (where A = Al) by Al dissolution in F-containing solution; most other MAX phases have not been explored. Here a redox-controlled A-site etching of MAX phases in Lewis acidic melts is proposed and validated by the synthesis of various MXenes from unconventional MAX-phase precursors with A elements Si, Zn and Ga. A negative electrode of Ti3C2 MXene material obtained through this molten salt synthesis method delivers a Li+ storage capacity of up to 738 C g(-1) (205 mAh g(-1)) with high charge-discharge rate and a pseudocapacitive-like electrochemical signature in 1 M LiPF6 carbonate-based electrolyte. MXenes prepared via this molten salt synthesis route may prove suitable for use as high-rate negative-electrode materials for electrochemical energy storage applications.
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