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

Computer simulation of high resolution images of crystal defects

Vibrational spectroscopy in the electron microscope [1], which was made possible by combining stable monochromators with ultra-stable electron energy loss (EEL) spectrometers, continues to progress rapidly. The Nion Iris spectrometer [2], incorporated into the Nion High Energy Resolution Monochromated EELS-STEM (HERMES) system [3] has led to an EELS era in which 5 meV energy resolution can be attained at 30 keV primary energy, and combined with atom-sized electron probes. The progress in energy resolution is illustrated in Fig. 1, which compares a recent spectrum of guanine (EELS 1) with one published in 2016 (EELS 2), and an FTIR spectrum of the same sample [4]. Reduced tails of the zero loss peak and better energy resolution make the information content of the more recent spectrum resemble the FTIR spectrum more than the older EELS spectrum, especially in the spectrum region between 50 and 220 meV.

Progress in Ultra-High Energy Resolution EELS

Extended abstract of a paper presented at Microscopy and Microanalysis 2005 in Honolulu, Hawaii, USA, July 31--August 4, 2005

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Nion UltraSTEM: An Aberration-Corrected STEM for Imaging and Analysis

Applications of Electron Energy Loss Spectroscopy in Materials Science

A high resolution energy-selecting electron beam apparatus and method for improving the energy resolution of electron-optical systems by restricting the energy range of admitted electrons, and optionally also for improving the spatial resolution by correcting chromatic and geometric aberrations. The apparatus comprises a plurality of magnetic or electrostatic prisms that disperse an electron beam according to the energies of the electrons into an energy spectrum, a plurality of magnifying lenses such as electromagnetic or electrostatic quadrupoles that increase the energy dispersion of the energy spectrum, an energy-selecting slit that selects a desirable range of energies of the electrons, and optionally also sextupole, octupole and higher-order lenses that correct chromatic and geometric aberration of the electron-optical system. The apparatus also comprises further magnetic or electrostatic prisms and electron lenses arranged such that the energy dispersion of the electron beam emerging from the apparatus is cancelled.

Ondrej L. Krivanek

Papers

Computer simulation of high resolution images of crystal defects

Progress in Ultra-High Energy Resolution EELS

Nion UltraSTEM: An Aberration-Corrected STEM for Imaging and Analysis

Applications of Electron Energy Loss Spectroscopy in Materials Science

High resolution energy-selecting electron beam apparatus