| 1. |
- Cossu, Fabrizio, et al.
(författare)
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Strain-induced stripe phase in charge-ordered single layer NbSe2
- 2020
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Ingår i: NPG ASIA MATERIALS. - : NATURE PUBLISHING GROUP. - 1884-4049 .- 1884-4057. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Charge density waves are ubiquitous phenomena in metallic transition metal dichalcogenides. In NbSe2, a triangular 3x3 structural modulation is coupled to a charge modulation. Recent experiments reported evidence for a triangular-stripe transition at the surface, due to strain or accidental doping and associated to a 4x4 modulation. We employ ab initio calculations to investigate the strain-induced structural instabilities in a pristine single layer and analyse the energy hierarchy of the structural and charge modulations. Our results support the observation of phase separation between triangular and stripe phases in 1H-NbSe2, relating the stripe phase to compressive isotropic strain, favouring the 4x4 modulation. The observed wavelength of the charge modulation is also reproduced with a good accuracy.
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| 2. |
- Jiang, Wei, et al.
(författare)
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Room-temperature broadband quasistatic magnetic cloak
- 2017
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Ingår i: NPG ASIA MATERIALS. - : Nature Publishing Group. - 1884-4049 .- 1884-4057. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- In the past decade, invisible cloaks have experienced rapid research development in the metamaterial community driven by their revolutionary practical potentials. Among them, magnetic cloaks, which are able to conceal metallic or magnetic objects from electromagnetic induction detection, have attracted a great amount of attention. However, applications of these reported devices are limited by their low-temperature environment requirement because of the involvement of superconductors to acquire the perfect diamagnetic response. In this work, we remove this temperature hurdle by fully taking the diamagnetic features of usual metals and demonstrate a three-dimensional room temperature quasistatic magnetic cloak using a ferromagnetic metallic bilayer structure. Experimentally, our device exhibits a prominent cloaking effect in a wide frequency range from 5 to 250 kHz with a maximum field disturbance ratio < 0.5%. The practical potential is verified through a commercial handheld metal probe working at 25 kHz. Our results unambiguously show that an invisible cloak may be realized in the low-frequency region for scenarios where screening an external magnetic field without disturbance is specifically demanded.
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| 3. |
- Kim, Jae-Kwang, 1978, et al.
(författare)
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Rechargeable-hybrid-seawater fuel cell
- 2014
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Ingår i: NPG Asia Materials. - : Springer Science and Business Media LLC. - 1884-4049 .- 1884-4057. ; 6:11, s. Article number e144-
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Tidskriftsartikel (refereegranskat)abstract
- A novel energy conversion and storage system using seawater as a cathode is proposed herein. This system is an intermediate between a battery and a fuel cell, and is accordingly referred to as a hybrid fuel cell. The circulating seawater in this opencathode system results in a continuous supply of sodium ions, which gives this system superior cycling stability that allows the application of various alternative anodes to sodium metal by compensating for irreversible charge losses. Indeed, hard carbon and Sn-C nanocomposite electrodes were successfully applied as anode materials in this hybrid-seawater fuel cell, yielding highly stable cycling performance and reversible capacities exceeding 110 mAh g-1 and 300 mAh g-1, respectively.
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| 4. |
- Kim, Seong-Min, et al.
(författare)
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High-performance, polymer-based direct cellular interfaces for electrical stimulation and recording
- 2018
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Ingår i: NPG ASIA MATERIALS. - : NATURE PUBLISHING GROUP. - 1884-4049 .- 1884-4057. ; 10, s. 255-265
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Tidskriftsartikel (refereegranskat)abstract
- Due to the trade-off between their electrical/electrochemical performance and underwater stability, realizing polymer-based, high-performance direct cellular interfaces for electrical stimulation and recording has been very challenging. Herein, we developed transparent and conductive direct cellular interfaces based on a water-stable, high-performance poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) film via solvent-assisted crystallization. The crystallized PEDOT:PSS on a polyethylene terephthalate (PET) substrate exhibited excellent electrical/electrochemical/optical characteristics, long-term underwater stability without film dissolution/delamination, and good viability for primarily cultured cardiomyocytes and neurons over several weeks. Furthermore, the highly crystallized, nanofibrillar PEDOT:PSS networks enabled dramatically enlarged surface areas and electrochemical activities, which were successfully employed to modulate cardiomyocyte beating via direct electrical stimulation. Finally, the high-performance PEDOT:PSS layer was seamlessly incorporated into transparent microelectrode arrays for efficient, real-time recording of cardiomyocyte action potentials with a high signal fidelity. All these results demonstrate the strong potential of crystallized PEDOT:PSS as a crucial component for a variety of versatile bioelectronic interfaces.
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| 5. |
- Lagerwall, Jan P. F., et al.
(författare)
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Cellulose nanocrystal-based materials : from liquid crystal self-assembly and glass formation to multifunctional thin films
- 2014
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Ingår i: NPG Asia materials. - : Springer Science and Business Media LLC. - 1884-4049 .- 1884-4057. ; 6
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Forskningsöversikt (refereegranskat)abstract
- Cellulose nanocrystals (CNCs), produced by the acid hydrolysis of wood, cotton or other cellulose-rich sources, constitute a renewable nanosized raw material with a broad range of envisaged uses: for example, in composites, cosmetics and medical devices. The intriguing ability of CNCs to self-organize into a chiral nematic (cholesteric) liquid crystal phase with a helical arrangement has attracted significant interest, resulting in much research effort, as this arrangement gives dried CNC films a photonic band gap. The films thus acquire attractive optical properties, creating possibilities for use in applications such as security papers and mirrorless lasing. In this critical review, we discuss the sensitive balance between glass formation and liquid crystal self-assembly that governs the formation of the desired helical structure. We show that several as yet unclarified observations-some constituting severe obstacles for applications of CNCs-may result from competition between the two phenomena. Moreover, by comparison with the corresponding self-assembly processes of other rod-like nanoparticles, for example, carbon nanotubes and fd virus particles, we outline how further liquid crystal ordering phenomena may be expected from CNCs if the suspension parameters can be better controlled. Alternative interpretations of some unexpected phenomena are provided, and topics for future research are identified, as are new potential application strategies.
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| 6. |
- Ma, Yungui, et al.
(författare)
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A transient thermal cloak experimentally realized through a rescaled diffusion equation with anisotropic thermal diffusivity
- 2013
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Ingår i: NPG Asia Materials. - : Springer Science and Business Media LLC. - 1884-4049 .- 1884-4057. ; 5:11, s. e73-
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Tidskriftsartikel (refereegranskat)abstract
- Transformation optics has made a major contribution to the advancement of modern electromagnetism and related research assisted by the development of metamaterials. In this work, we applied this concept to the thermodynamics using the coordinate transformation to the time-dependent heat diffusion equation to manipulate the heat flux by predefined diffusion paths. Experimentally, we demonstrated a transient thermal cloaking device engineered with effective thermal materials and successfully hid a centimeter-sized vacuum cavity. A rescaled heat equation accounting for all the pertinent parameters of various ingredient materials was proposed to greatly facilitate the fabrication. Our results unambiguously demonstrate the practical possibility of implementing complex transformed thermal media with high accuracy and acquiring several unprecedented thermodynamic functions, which we believe will help to broaden the current research and pave a new path to manipulate heat for novel device applications.
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| 7. |
- Tian, Yuxi, et al.
(författare)
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Watching two conjugated polymer chains breaking each other when colliding in solution
- 2014
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Ingår i: NPG Asia Materials. - : Springer Science and Business Media LLC. - 1884-4049 .- 1884-4057. ; 6, s. 134-134
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Tidskriftsartikel (refereegranskat)abstract
- While collision theory successfully describes the kinetics of chemical reactions, very little is known about the processes at the molecular level, especially if the reacting molecules are large. In this study, using single-molecule spectroscopy, we visually observed that collision between two conjugated polymer (CP) molecules in solution leads to simultaneous rupture of both chains. In addition to opening up the possibility of monitoring chemical processes in solution at the single-molecule level, these results demonstrate that mechanical bending of two stiff conjugated backbones against each other (the effect of leverage) by Brownian motion can weaken the chemical bond and markedly accelerate photochemical oxygen-induced chain scission by at least 20 times. The catalytic effect of the chain bending is also enhanced by a prolonged interaction between the chains owing to their entanglement. These findings are important for the solution processing of CPs in their application in organic electronics, for understanding the degradation mechanisms in CPs and for the development of new catalysts based on mechanical interactions with target molecules.
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| 8. |
- Wang, Baoyuan, et al.
(författare)
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Fast ionic conduction in semiconductor CeO2-delta electrolyte fuel cells
- 2019
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Ingår i: NPG ASIA MATERIALS. - : Nature Publishing Group. - 1884-4049 .- 1884-4057. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Producing electrolytes with high ionic conductivity has been a critical challenge in the progressive development of solid oxide fuel cells (SOFCs) for practical applications. The conventional methodology uses the ion doping method to develop electrolyte materials, e.g., samarium-doped ceria (SDC) and yttrium-stabilized zirconia (YSZ), but challenges remain. In the present work, we introduce a logical design of non-stoichiometric CeO2-delta based on non-doped ceria with a focus on the surface properties of the particles. The CeO2-delta reached an ionic conductivity of 0.1 S/cm and was used as the electrolyte in a fuel cell, resulting in a remarkable power output of 660 mW/cm(2) at 550 degrees C. Scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) clearly clarified that a surface buried layer on the order of a few nanometers was composed of Ce3+ on ceria particles to form a CeO2-delta@CeO2 core-shell heterostructure. The oxygen deficient layer on the surface provided ionic transport pathways. Simultaneously, band energy alignment is proposed to address the short circuiting issue. This work provides a simple and feasible methodology beyond common structural (bulk) doping to produce sufficient ionic conductivity. This work also demonstrates a new approach to progress from material fundamentals to an advanced low-temperature SOFC technology.
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| 9. |
- Zhang, Xudong, et al.
(författare)
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C-60/Na4FeO3/Li3V2(PO4)(3)/soft carbon quaternary hybrid superstructure for high-performance battery-supercapacitor hybrid devices
- 2020
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Ingår i: NPG ASIA MATERIALS. - : NATURE PUBLISHING GROUP. - 1884-4049 .- 1884-4057. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- To develop battery-supercapacitor hybrid devices with high energy and power densities, we propose a rational design of a quaternary hybrid superstructure by using a high-energy biotemplate. This new superstructure is composed of stable fullerene C-60 nanocages, electroactive Na4FeO3, high-energy Li3V2(PO4)(3) and soft carbon as well as tubular ordered mesoporous channels. This design takes advantage of the unique properties of each component, resulting in nanocomposites with synergistic effects to improve the charge transfer and energy storage. We found that this quaternary hybrid electrode has both high energy and power densities as well as a long cycling life in a Li/Na mixed-ion electrolyte, outperforming a multitude of other battery-supercapacitor hybrid devices reported thus far. The charge storage mechanisms of this hybrid superstructure are proposed for optimizing the electrode design.
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| 10. |
- Zheng, Jiapeng, et al.
(författare)
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Hybrid optofluidics and three-dimensional manipulation based on hybrid photothermal waveguides
- 2018
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Ingår i: NPG Asia Materials. - : Nature Publishing Group. - 1884-4049 .- 1884-4057. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Despite enormous breakthroughs in lab-on-a-chip techniques, light-driven manipulation faces two long-standing challenges: the ability to achieve both multiform manipulation and tunable manipulation range and the means to avoid potential thermal damage to the targets. By harnessing the optical heating of hybrid photothermal waveguides (HPW), we develop a hybrid optofluidic technique involving buoyancy and thermocapillary convection to achieve fluid transport with controllable modes and tunable strength. Switching of the optofluidic mode from buoyancy to thermocapillary convection, namely, from vertical to horizontal vortices, is employed for three-dimensional manipulation. The strong confinement and torque in the vortices are capable of trapping and rotating/spinning particles at the vortex centers rather than the HPW. Buoyancy convection provides a trapping circle to achieve collective trapping and vertical rotation/spin, while thermocapillary convection offers a trapping lattice to achieve distributed trapping and horizontal rotation/spin. By integrating micro/nanoparticles with various properties and sizes, further investigations of the optofluidic arrangement, mixing, and synthesis will broaden the potential applications of the hybrid optofluidic technique in the fields of lab-on-a-chip, materials science, chemical synthesis and analysis, photonics, and nanoscience.
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