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. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN USA. 2. Materials Physics Center, CSIC-UPV/EHU, 20018 Donostia-San Sebastián, Spain. 3. Institut de Ciència de Materials de Barcelona, Campus de la UAB, 08193 Bellaterra, Spain 4 Nion Company, 11511 NE 118th St, Kirkland, WA USA. 5. ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain. 6. ICREA-Institucó Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Spain. 7. Laboratoire de Physique des Solides, Bâtiment 510, CNRS UMR 8502, Université Paris Sud XI, F 91405 Orsay, France. 8. Donostia International Physics Center DIPC, 20018 Donostia-San Sebastián, Spain.

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EELS in STEM: the ``Swiss Army Knife'' of Spectroscopy

'A Priori' synthesis of electron energy-loss spectra for detection limit quantification

Transition metal oxides revisited: ELNES of metal L2,3 and oxygen K edges

Imperfections such as stacking faults and interfaces are recognized as decisive factors in modifying thermal properties and heat transport in crystal materials by scattering phonon and changing vibrational structure [1]. However, the effect of crystal defects on thermal conductivity is being theoretically treated by perturbation methods without taking into account the local change of phonon dispersion relation [2]. Direct observation of local vibrational structure at single crystal defect has not been realized until now. The main issue is the spatial resolution required to resolve individual defects is not achievable for most of phonondetecting techniques including optical, and inelastic X-ray and neutron spectroscopies [3]. Here we demonstrate that spaceand angle-resolved vibrational spectroscopy in a transmission electron microscope (TEM) enables the study of the vibrational structure of individual crystal defects. At a single stacking fault in a cubic silicon carbide, the acoustic vibration modes at X point undergo a red shift of several millielectronvolts, become enhanced, and are confined to within a few nanometers of the stacking fault. The detection of interfacial modes at an atomically thin Si-Ge interface will be discussed as well [4]. Our work opens the door to investigating phonon propagation around crystal defects, and provides guidance to the engineering of desired thermal performance for semiconductor and power electronic devices.

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Probing Local Vibration Modes at Single Planar Defects by Vibrational Spectroscopy

MSA – the Microscopy Society of America – was founded in 1942 as EMSA, with the extra “E” standing for “Electron”. The first delivery of RCA’s transmission electron microscope (TEM, to American Cyanamid) took place in December 1940, and the society’s mission was to advance electron microscopy and especially specimen preparation [1]. The resolution of the first TEMs was about 10 nm – significantly better than the 200 nm resolution possible at that time with light microscopes, but a far cry from the 0.1 nm (1 Å) resolution needed to resolve individual atoms in a wide range of materials.

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Ondrej L. Krivanek

Papers

EELS in STEM: the ``Swiss Army Knife'' of Spectroscopy

'A Priori' synthesis of electron energy-loss spectra for detection limit quantification

Transition metal oxides revisited: ELNES of metal L2,3 and oxygen K edges

Probing Local Vibration Modes at Single Planar Defects by Vibrational Spectroscopy

Smarter than an iPhone: the emergence of the modern electron microscope