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

Lattice Imaging of Stacking Faults in (011) Silicon

1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. 2 Nion Co. Kirkland, Washington, USA. 3 Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. 4 Departamento de Física, Escuela Politécnica Nacional, Quito, Ecuador. 5 LeRoy Eyring Center for Solid State Sciences, Arizona State University, Arizona, USA. 6 Departamento de Física Aplicada III, Universidad Complutense de Madrid, Spain. 7 Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA

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Monochromatic STEM-EELS for Correlating the Atomic Structure and Optical Properties of Two-Dimensional Materials

Aberration-corrected scanning transmission electron microscopes (STEMs) can resolve single atoms, probe them spectroscopically, and produce elemental and chemical maps with atomic resolution in 2D and 3D. When equipped with a monochromator and operating in an aloof mode, STEMs can record vibrational electron energy loss spectra (vib-EELS) to create nm-scale vibrational maps while avoiding radiation damage. These techniques require excellent short-term (vibration) and long-term (drift) stability of the microscope’s sample stage.

Stable and Flexible Side-Entry Stage for Nion STEMs

Aberration-Corrected STEM: the Present and the Future

Among his key accomplishments, Gareth initiated the National Center for Electron Microscopy (NCEM) at Lawrence Berkeley National Laboratory (LBNL). The center has its origins in the mid 1970s, when it became clear that high resolution electron microscopes (HREMs) were capable of giving better than 2 Å resolution, and that this would allow many structures to be solved by direct imaging rather than indirect methods. Gareth organized a workshop on the future of HREM, with international experts giving talks and working groups analyzing the most promising future avenues. The conclusions of the workshop were not altogether unexpected: high voltage HREMs were thought to have the best chance of resolving a wide range of unknown structures, and were likely to be expensive. Quoting from the workshop report [1]: “The conclusion of the workshop was that there is indeed a need for a national facility for high resolution electron microscopy. The facility should be a center of excellence, located at a site with established reputation and dedication to electron microscopy and having existing scientific ... resources.” NCEM was the logical result.

Ondrej L. Krivanek

Papers

Lattice Imaging of Stacking Faults in (011) Silicon

Monochromatic STEM-EELS for Correlating the Atomic Structure and Optical Properties of Two-Dimensional Materials

Stable and Flexible Side-Entry Stage for Nion STEMs

Aberration-Corrected STEM: the Present and the Future

Instrumentation/Technique Developments in Gareth Thomas's Research Group