A semi-automated routine for continuous rotation electron diffraction has been developed, enabling high-throughput data collection. Serial electron crystallography combined with a deep convolutional network are used to screen for suitable crystals.

Two-dimensional monolayer transition metal dichalcogenides (TMdCs), driven by graphene science, revisit optical and electronic properties, which are markedly different from bulk characteristics. These properties are easily modified due to accessibility of all the atoms viable to ambient gases, and therefore, there is no guarantee that impurities and defects such as vacancies, grain boundaries, and wrinkles behave as those of ideal bulk. On the other hand, this could be advantageous in engineering such defects. Here, we report a method of observing grain boundary distribution of monolayer TMdCs by a selective oxidation. This was implemented by exposing directly the TMdC layer grown on sapphire without transfer to ultraviolet light irradiation under moisture-rich conditions. The generated oxygen and hydroxyl radicals selectively functionalized defective grain boundaries in TMdCs to provoke morphological changes at the boundary, where the grain boundary distribution was observed by atomic force microscopy and scanning electron microscopy. This paves the way toward the investigation of transport properties engineered by defects and grain boundaries.

The oxygen reduction reaction (ORR) is central in carbon-neutral energy devices. While platinum group materials have shown high activities for ORR, their practical uses are hampered by concerns over deactivation, slow kinetics, exorbitant cost, and scarce nature reserve. The low cost yet high tunability of metal–organic frameworks (MOFs) provide a unique platform for tailoring their characteristic properties as new electrocatalysts. Herein, we report a new concept of design and present stable Zr-chain-based MOFs as efficient electrocatalysts for ORR. The strategy is based on using Zr-chains to promote high chemical and redox stability and, more importantly, tailor the immobilization and packing of redox active-sites at a density that is ideal to improve the reaction kinetics. The obtained new electrocatalyst, PCN-226, thereby shows high ORR activity. We further demonstrate PCN-226 as a promising electrode material for practical applications in rechargeable Zn-air batteries, with a high peak power density of 133 mW cm –2 . Being one of the very few electrocatalytic MOFs for ORR, this work provides a new concept by designing chain-based structures to enrich the diversity of efficient electrocatalysts and MOFs.

Whether and how fracture mechanics needs to be modified for small length scales and in systems of reduced dimensionality remains an open debate. Here, employing in situ transmission electron microscopy, atomic structures and dislocation dynamics in the crack tip zone of a propagating crack in two-dimensional (2D) monolayer MoS 2 membrane are observed, and atom-to-atom displacement mapping is obtained. The electron beam is used to initiate the crack; during in situ observation of crack propagation the electron beam effect is minimized. The observed high-frequency emission of dislocations is beyond previous understanding of the fracture of brittle MoS 2 . Strain analysis reveals dislocation emission to be closely associated with the crack propagation path in nanoscale. The critical crack tip plastic zone size of nearly perfect 2D MoS 2 is between 2 and 5 nm, although it can grow to 10 nm under corrosive conditions such as ultraviolet light exposure, showing enhanced dislocation activity via defect generation.

A new medium-pore germanosilicate, denoted IM-18, with a three-dimensional 8 × 8 × 10-ring channel system, has been prepared hydrothermally using 4-dimethylaminopyridine as an organic structure-directing agent (OSDA). Due to the presence of stacking disorder, the structure elucidation of IM-18 was challenging, and a combination of different techniques, including electron diffraction, high-resolution transmission electron microscopy (HRTEM), and Rietveld refinement using synchrotron powder diffraction data, was necessary to elucidate the details of the structure and to understand the nature of the disorder. Rotation electron diffraction data were used to determine the average structure of IM-18, HRTEM images to characterize the stacking disorder, and Rietveld refinement to locate the Ge in the framework and the OSDA occluded in the channels.

The dynamic interaction of methanol and its derivatives with Cu-exchanged ZSM-5 during methanol temperature programmed desorption from 30 to 450 C has been investigated using in situ di↵use reflectance infrared Fourier transform spectroscopy and first-principles calculations. The results emphasize that defects in the framework structure of the zeolite and Brønsted acid sites constitute ion-exchange sites for Cu 1 ions. The Cu sites introduced in ZSM-5 actively interact with methanol adsorbed at moderate temperature, i.e. below 250 C, and take roles in further oxidation of the adsorbed species to formate and CO. Moreover, spectra recorded at higher temperatures, i.e. above 300 C, after adsorption of methanol show strong interaction between methoxy groups and the zeolite framework, suggesting that under mild conditions proton extraction for methanol production during direct partial oxidation of methane to methanol over Cu-ZSM-5 is necessary.

No abstract

Layered materials (LMs) such as graphene or MoS2 have recently attracted a great deal of interest. These materials offer unique functionalities due to their structural anisotropy characterized by weak van der Waals bonds along the out-of-plane axis and covalent bonds in the in-plane direction. A central requirement to access the structural information of complex nanostructures built upon LMs is to control the relative orientation of each sample prior to their inspection e.g. with Transmission Electron Microscopy (TEM). However, developing sample preparation methods that result in large inspection areas and ensure full control over the sample orientation while avoiding damage during the transfer to the TEM grid is challenging.Here we demonstrate the feasibility of deploying ultramicrotomy for the preparation of LM samples in TEM analyses. We show how ultramicrotomy leads to the reproducible large-scale production of both in-plane and out-of-plane cross-sections, with bulk vertically-oriented MoS2 and WS2 nanosheets as proof of concept. The robustness of the prepared samples is subsequently verified by their characterization by means of both high-resolution TEM and Raman spectroscopy measurements. Our approach is fully general and should find applications for a wide range of materials as well as of techniques beyond TEM, thus paving the way to the systematic large-area mass-production of cross-sectional specimens for structural and compositional studies.