High-resolution imaging of electron beam-sensitive materials is one of the most difficult applications of transmission electron microscopy (TEM). The challenges are manifold, including the acquisition of images with extremely low beam doses, the time-constrained search for crystal zone axes, the precise image alignment, and the accurate determination of the defocus value. We develop a suite of methods to fulfill these requirements and acquire atomic-resolution TEM images of several metal organic frameworks that are generally recognized as highly sensitive to electron beams. The high image resolution allows us to identify individual metal atomic columns, various types of surface termination, and benzene rings in the organic linkers. We also apply our methods to other electron beam-sensitive materials, including the organic-inorganic hybrid perovskite CHNHPbBr.
The shuttling effect of polysulfides severely hinders the cycle performance and commercialization of Li−S batteries, and significant efforts have been devoted to searching for feasible solutions to mitigate the effect in the past two decades. Recently, metal−organic frameworks (MOFs) with rich porosity, nanometer cavity sizes, and high surface areas have been claimed to be effective in suppressing polysulfide migration. However, the formation of large-scale and grain boundary-free MOFs is still very challenging, where a large number of grain boundaries of MOF particles may also allow the diffusion of polysulfides. Hence, it is still controversial whether the pores in MOFs or the grain boundaries play the critical role. In this study, we perform a comparative study for several commonly used MOFs, and our experimental results and analysis prove that a layer of MOFs on a separator did enhance the capacity stability. Our results suggest that the chemical stability and the aggregation (packing) morphology of MOF particles play more important roles than the internal cavity size in MOFs.
is currently based on structures floating on water. [11,13,17,[19][20][21][22] By using graphite membranes, the highest solar thermal efficiency (see Equation (4)) of 85% has been reported under an equivalent solar intensity of 10 suns. [13] One of the main drawback of this approach, besides the large light intensity requirement, lies in the fact that carbon-based systems (both graphite and graphene) are vulnerable to the contamination of pollutants or salt in the water, thus limiting the recyclability of the membrane after prolonged use.In this article, we developed a different approach, which makes use of a flat-optics metasurface [23][24][25][26][27][28] composed of suitably engineered plasmonic nanoparticles. [29,30] Plasmonics structures, thanks to the possibility of localizing light energy at the nanoscale, have demonstrated a great potential in converting light energy into heat for a variety of photothermal applications. [31][32][33][34] In plasmonic steam generation, the best results have been obtained with porous films, which reported efficiencies of ≈60% under 1 sun. [19,20] The efficiency limits of these structures originate from the resonant nature of classical plasmonic materials, which usually harvest energy only at characteristic frequencies of the solar spectrum. In our metasurface, we overcome this problem by using a completely new mechanism of heat generation supported by biomimetic nanoparticles that behave as an almost ideal blackbody. These nanoparticles mimic the shell of an Asian specie of beetle that possesses an exceptional ability in controlling light reflection. [29] Even when these nanoparticles are used in extremely small volumes, they completely absorb input photons at all frequencies and polarizations. By suitably dispersing these nanoparticles in a paper film, we created a metasurface with a remarkable ability in transforming light energy into heat, leading to a dramatic increase of solar thermal generation efficiency if compared to classical structures. Our nanoparticles are fully recyclable from the paper substrate and invulnerable to saline water corrosion, representing an ideal system for solar steam generation. [35] 2. Results
Sample Design and Fabrication
Mixed-matrix membranes composed of mechanically strong, solution-processable polymers and highly selective ultramicroporous fillers (pore size < 7 Å) are superior candidate membrane materials for a variety of energy-intensive gas separation applications because of their structural tunability to achieve enhanced gas permeability and gas-pair selectivity. However, their industrial implementation has been severely hindered because inefficient compatibility of the polymer matrices and crystalline fillers results in poorly performing membranes with low filler capacity and interfacial defects. Herein, we report for the first time a unique strategy to fabricate highly propylene/propane selective mixed-matrix membranes (MMMs) composed of a hydroxyl-functionalized microporous polyimide (PIM-6FDA-OH) and an ultramicroporous, strongly size-sieving zeolitic imidazolate framework (ZIF-8). Excellent compatibility between PIM-6FDA-OH and ZIF-8 with selective filler loading up to 65 wt% resulted from N…O-H induced hydrogen bonding as evidenced by Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The newly developed MMMs demonstrated unprecedented mixed-gas performance for C 3 H 6 /C 3 H 8 separation and outstanding plasticization resistance of up to at least 7 bar feed pressure. The reported fabrication concept is expected to be applicable to a wide variety of OH functionalized polymers and alternative tailor-made imidazolate framework materials designed for MMMs to achieve optimal gas separation performance.
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