Recently, a large family of 2D materials called MXenes have attracted much attention in the field of supercapacitors, thanks to the excellent performance demonstrated by Ti3C2 MXene-based electrodes. ...However, research on MXenes for supercapacitor applications has been primarily focused on Ti3C2, even though there are more than 20 other members of this large family of materials already available. Studies on other MXenes are emerging, with promising results already achieved by Ti2C, Mo2C, and Mo1.33C in aqueous electrolytes. Yet, many other MXenes remain unexplored in aqueous supercapacitor applications. In this work, we report on the electrochemical behavior of a vanadium carbide MXene, V2C, in three aqueous electrolytes. Excellent specific capacitances were achieved, specifically 487 F/g in 1 M H2SO4, 225 F/g in 1 M MgSO4, and 184 F/g in 1 M KOH, which are higher than previously reported values for few micrometer-thick delaminated MXene electrodes. This work shows the promise of V2C MXene for energy storage using aqueous electrolytes.
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•A flexible freestanding film was prepared from MXene V2C nanosheets.•V2C MXene was investigated as electrode for supercapacitors with three aqueous electrolytes.•The best performance, 487 F/g, was obtained in 1 M H2SO4.•V2C exhibited higher specific capacitance than previously reported MXenes.
The fundamental properties and ultimate performance limits of organolead trihalide MAPbX3 (MA = CH3NH3+; X = Br– or I–) perovskites remain obscured by extensive disorder in polycrystalline MAPbX3 ...films. We report an antisolvent vapor-assisted crystallization approach that enables us to create sizable crack-free MAPbX3 single crystals with volumes exceeding 100 cubic millimeters. These large single crystals enabled a detailed characterization of their optical and charge transport characteristics. We observed exceptionally low trap-state densities on the order of 109 to 1010 per cubic centimeter in MAPbX3 single crystals (comparable to the best photovoltaic-quality silicon) and charge carrier diffusion lengths exceeding 10 micrometers. These results were validated with density functional theory calculations.
Graphene kirigami Blees, Melina K; Barnard, Arthur W; Rose, Peter A ...
Nature (London),
08/2015, Letnik:
524, Številka:
7564
Journal Article
Recenzirano
For centuries, practitioners of origami ('ori', fold; 'kami', paper) and kirigami ('kiru', cut) have fashioned sheets of paper into beautiful and complex three-dimensional structures. Both techniques ...are scalable, and scientists and engineers are adapting them to different two-dimensional starting materials to create structures from the macro- to the microscale. Here we show that graphene is well suited for kirigami, allowing us to build robust microscale structures with tunable mechanical properties. The material parameter crucial for kirigami is the Föppl-von Kármán number γ: an indication of the ratio between in-plane stiffness and out-of-plane bending stiffness, with high numbers corresponding to membranes that more easily bend and crumple than they stretch and shear. To determine γ, we measure the bending stiffness of graphene monolayers that are 10-100 micrometres in size and obtain a value that is thousands of times higher than the predicted atomic-scale bending stiffness. Interferometric imaging attributes this finding to ripples in the membrane that stiffen the graphene sheets considerably, to the extent that γ is comparable to that of a standard piece of paper. We may therefore apply ideas from kirigami to graphene sheets to build mechanical metamaterials such as stretchable electrodes, springs, and hinges. These results establish graphene kirigami as a simple yet powerful and customizable approach for fashioning one-atom-thick graphene sheets into resilient and movable parts with microscale dimensions.
Graphene-based materials can have well-defined nanometer pores and can exhibit low frictional water flow inside them, making their properties of interest for filtration and separation. We investigate ...permeation through micrometer-thick laminates prepared by means of vacuum filtration of graphene oxide suspensions. The laminates are vacuum-tight in the dry state but, if immersed in water, act as molecular sieves, blocking all solutes with hydrated radii larger than 4.5 angstroms. Smaller ions permeate through the membranes at rates thousands of times faster than what is expected for simple diffusion. We believe that this behavior is caused by a network of nanocapillaries that open up in the hydrated state and accept only species that fit in. The anomalously fast permeation is attributed to a capillary-like high pressure acting on ions inside graphene capillaries.
Expansion microscopy Chen, Fei; Tillberg, Paul W.; Boyden, Edward S.
Science (American Association for the Advancement of Science),
01/2015, Letnik:
347, Številka:
6221
Journal Article
Recenzirano
Odprti dostop
In optical microscopy, fine structural details are resolved by using refraction to magnify images of a specimen. We discovered that by synthesizing a swellable polymer network within a specimen, it ...can be physically expanded, resulting in physical magnification. By covalently anchoring specific labels located within the specimen directly to the polymer network, labels spaced closer than the optical diffraction limit can be isotropically separated and optically resolved, a process we call expansion microscopy (ExM). Thus, this process can be used to perform scalable superresolution microscopy with diffraction-limited microscopes. We demonstrate ExM with apparent ∼70-nanometer lateral resolution in both cultured cells and brain tissue, performing three-color superresolution imaging of ∼107 cubic micrometers of the mouse hippocampus with a conventional confocal microscope.
Displays are basic building blocks of modern electronics
. Integrating displays into textiles offers exciting opportunities for smart electronic textiles-the ultimate goal of wearable technology, ...poised to change the way in which we interact with electronic devices
. Display textiles serve to bridge human-machine interactions
, offering, for instance, a real-time communication tool for individuals with voice or speech difficulties. Electronic textiles capable of communicating
, sensing
and supplying electricity
have been reported previously. However, textiles with functional, large-area displays have not yet been achieved, because it is challenging to obtain small illuminating units that are both durable and easy to assemble over a wide area. Here we report a 6-metre-long, 25-centimetre-wide display textile containing 5 × 10
electroluminescent units spaced approximately 800 micrometres apart. Weaving conductive weft and luminescent warp fibres forms micrometre-scale electroluminescent units at the weft-warp contact points. The brightness between electroluminescent units deviates by less than 8 per cent and remains stable even when the textile is bent, stretched or pressed. Our display textile is flexible and breathable and withstands repeated machine-washing, making it suitable for practical applications. We show that an integrated textile system consisting of display, keyboard and power supply can serve as a communication tool, demonstrating the system's potential within the 'internet of things' in various areas, including healthcare. Our approach unifies the fabrication and function of electronic devices with textiles, and we expect that woven-fibre materials will shape the next generation of electronics.
In the search for improved energy storage, rechargeable metal-oxygen batteries are very attractive owing to their reliance on molecular oxygen, which forms oxides on discharge that decompose ...reversibly on charge. Much focus has been directed at aprotic Li-O2 cells, but the aprotic Na-O2 system is of equal interest because of its better reversibility. We report here on the critical role and mechanism of phase-transfer catalysis in Na-O2 batteries. We find that it is solely responsible for the growth and dissolution of micrometre-sized cubic NaO2 crystals and for the reversible cell capacity. In the absence of phase-transfer catalysis, quasi-amorphous NaO2 films are formed and cells exhibit negligible capacity. Electrochemical investigations provide a measure of the transportation of superoxide from the carbon electrode to the electrolyte phase by the phase transfer catalyst. This leads to a new understanding of the mechanism of Na-O2 batteries that, significantly, extends to Li-O2 cells and explains their different behaviour.
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