다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Platinum-based heterogeneous catalysts are critical to many important commercial chemical processes, but their efficiency is extremely low on a per metal atom basis, because only the surface active-site atoms are used. Catalysts with single-atom dispersions are thus highly desirable to maximize atom efficiency, but making them is challenging. Here we report the synthesis of a single-atom catalyst that consists of only isolated single Pt atoms anchored to the surfaces of iron oxide nanocrystallites. This single-atom catalyst has extremely high atom efficiency and shows excellent stability and high activity for both CO oxidation and preferential oxidation of CO in H-2. Density functional theory calculations show that the high catalytic activity correlates with the partially vacant 5d orbitals of the positively charged, high-valent Pt atoms, which help to reduce both the CO adsorption energy and the activation barriers for CO oxidation.

Single-atom catalysis of CO oxidation using Pt1/FeOx

Graphene’s success has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials, and also that these materials can exhibit fascinating and technologically useful properties. Here we review the state-of-the-art of 2D materials beyond graphene. Initially, we will outline the different chemical classes of 2D materials and discuss the various strategies to prepare single-layer, few-layer, and multilayer assembly materials in solution, on substrates, and on the wafer scale. Additionally, we present an experimental guide for identifying and characterizing single-layer-thick materials, as well as outlining emerging techniques that yield both local and global information. We describe the differences that occur in the electronic structure between the bulk and the single layer and discuss various methods of tuning their electronic properties by manipulating the surface. Finally, we highlight the properties and advantages of single-, few-, and many-layer 2D materials in...

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Progress, Challenges, and Opportunities in Two-Dimensional Materials Beyond Graphene

Graphene-Like Two-Dimensional Materials

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

1. Nion R&D, Kirkland, WA, USA. 2. Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin, Germany. 3. Department of Physics, Arizona State University, Tempe, AZ, USA. 4. Helmholtz Zentrum Berlin for Materials and Energy, Berlin, Germany. 5. Institut de Minéralogie, Physique des Matériaux et Cosmochimie, Sorbonne Université, Paris, France. 6. Pacific Northwest National Laboratory, Richland, WA, USA. * Corresponding authors: krivanek@nion.com and haas@physik.hu-berlin.de

Probing Biological Materials by Vibrational Analysis in the Electron Microscope

The Nion UltraSTEM aberration-corrected cold field emission scanning transmission electron microscope (AC-CFE-STEM) can focus a beam current of about 0.2 nA into an atom-sized (~1.5 Å large) electron probe at a primary energy of 60 keV (and about 1 nA at 200 keV). Using such an electron probe with an ultra-thin window silicon drift detector (SDD) of 30 mm (0.1 sr solid angle) in a Mark I system at 60 keV allowed energy dispersive X-ray spectroscopy (EDXS) to identify individual atoms while tracking their occasional hops to neighboring lattice sites [1]. Here we report on the design and performance of a Mark II STEM-EDXS system with about 10x higher efficiency, which allows single impurity atoms to be identified even when they are very mobile.

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STEM-EDXS System for Atomic-Sensitivity Elemental Mapping

Automatische Justierung eines Ladungsträgerteilchen-Sondenerzeugungsgerätes

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John C.H. Spence – friend, teacher, mentor, scientific pioneer and visionary

Extended electron energy loss fine structure (EXELFS) spectra obtained with a transmission electron microscope (TEM) are well suited to studies of core edges in the soft x-ray region[ 11. Transmission EXELFS data offer structural measurements localized within microscopic (< 100 nm diameter) regions of interest. Growth in this area of analysis has been slow because of low inelastic scattering cross-sections for 100 kV to 300 kV accelerating voltage electrons and limitations in the statistical quality of spectra attainable with serial acquisition systems. Parallel detection EXELFS experiments are expected to show statistical quality and radiation damage effects similar to those obtained in EXAFS spectra for samples which cannot be examined by transmission x-ray absorption[2]. In the present study, we demonstrate the excellent quality of the parallel detection EXELFS signal by examining the variation of the EXELFS amplitude with temperature for a thin aluminum foil.

Ondrej L. Krivanek

Papers

Probing Biological Materials by Vibrational Analysis in the Electron Microscope

STEM-EDXS System for Atomic-Sensitivity Elemental Mapping

Automatische Justierung eines Ladungsträgerteilchen-Sondenerzeugungsgerätes

John C.H. Spence – friend, teacher, mentor, scientific pioneer and visionary

Transmission EXELFS: Temperature dependence