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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

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

Graphene is very popular because of its many fascinating properties, but its lack of an electronic bandgap has stimulated the search for 2D materials with semiconducting character. Transition metal dichalcogenides (TMDCs), which are semiconductors of the type MX2, where M is a transition metal atom (such as Mo or W) and X is a chalcogen atom (such as S, Se or Te), provide a promising alternative. Because of its robustness, MoS2 is the most studied material in this family. TMDCs exhibit a unique combination of atomic-scale thickness, direct bandgap, strong spin–orbit coupling and favourable electronic and mechanical properties, which make them interesting for fundamental studies and for applications in high-end electronics, spintronics, optoelectronics, energy harvesting, flexible electronics, DNA sequencing and personalized medicine. In this Review, the methods used to synthesize TMDCs are examined and their properties are discussed, with particular attention to their charge density wave, superconductive and topological phases. The use of TMCDs in nanoelectronic devices is also explored, along with strategies to improve charge carrier mobility, high frequency operation and the use of strain engineering to tailor their properties. Two-dimensional transition metal dichalcogenides (TMDCs) exhibit attractive electronic and mechanical properties. In this Review, the charge density wave, superconductive and topological phases of TMCDs are discussed, along with their synthesis and applications in devices with enhanced mobility and with the use of strain engineering to improve their properties.

2D transition metal dichalcogenides

Graphene, a single layer of graphite, possesses a unique two-dimensional structure, high conductivity, superior electron mobility and extremely high specific surface area, and can be produced on a large scale at low cost. Thus, it has been regarded as an important component for making various functional composite materials. Especially, graphene-based semiconductor photocatalysts have attracted extensive attention because of their usefulness in environmental and energy applications. This critical review summarizes the recent progress in the design and fabrication of graphene-based semiconductor photocatalysts via various strategies including in situ growth, solution mixing, hydrothermal and/or solvothermal methods. Furthermore, the photocatalytic properties of the resulting graphene-based composite systems are also discussed in relation to the environmental and energy applications such as photocatalytic degradation of pollutants, photocatalytic hydrogen generation and photocatalytic disinfection. This critical review ends with a summary and some perspectives on the challenges and new directions in this emerging area of research (158 references).

Graphene-based semiconductor photocatalysts

High-quality ultrathin single-crystalline SnSe2 flakes are synthesized under atmospheric-pressure chemical vapor deposition for the first time. A high-performance photodetector based on the individual SnSe2 flake demonstrates a high photoresponsivity of 1.1 × 10(3) A W(-1), a high EQE of 2.61 × 10(5)%, and superb detectivity of 1.01 × 10(10) Jones, combined with fast rise and decay times of 14.5 and 8.1 ms, respectively.

Ultrathin SnSe2 Flakes Grown by Chemical Vapor Deposition for High‐Performance Photodetectors

Owing to the unique thickness dependent physical and chemical properties, two-dimensional (2D) layered nanomaterials have received tremendous attention and shown great potential in the fabrication of high-performance electronic/optoelectronic devices. Notably, the implication of 2D nanomaterials in the gas-sensing field has also drawn considerable attention but few related review studies have been reported. This critical review mainly focuses on the current progress of 2D layered nanomaterials in gas-sensing applications. Firstly, we describe the basic attributes of 2D layered nanostructures and discuss the fundamentals of their gas-sensing applications. Secondly, we have numerated recent gas-sensing studies on typical 2D layered nanomaterials, including graphene, MoS2, MoSe2, WS2, SnS2, black phosphorus, and others. Particularly, the optimized strategies for improving their gas-sensing performances are also discussed here. Finally, we conclude this review with some perspectives and the outlook on future advances in this field.

Two-dimensional layered nanomaterials for gas-sensing applications

2D SnS2 nanosheets have been attracting intensive attention as one potential candidate for the modern electronic and/or optoelectronic fields. However, the controllable large-size growth of ultrathin SnS2 nanosheets still remains a great challenge and the photodetectors based on SnS2 nanosheets suffer from low responsivity, thus hindering their further applications so far. Herein, an improved chemical vapor deposition route is provided to synthesize large-size SnS2 nanosheets, the side length of which can surpass 150 μm. Then, ultrathin SnS2 nanosheet-based phototransistors are fabricated, which achieve high photoresponsivities up to 261 A W−1 (with a fast rising time of 20 ms and a falling time of 16 ms) in air and 722 A W−1 in vacuum, respectively. Furthermore, the effects of back-gate voltage and air adsorbates on the optoelectronic properties of the SnS2 nanosheet have been systematically investigated. In addition, a high-performance flexible photodetector based on SnS2 nanosheet is also fabricated with a high responsivity of 34.6 A W−1.

Large‐Size Growth of Ultrathin SnS2 Nanosheets and High Performance for Phototransistors

Subcentimeter single-crystalline graphene grains, with diameter up to 5.9 mm, have been successfully synthesized by tuning the nucleation density during atmospheric pressure chemical vapor deposition. Morphology studies show the existence of a single large nanoparticle (>∼20 nm in diameter) at the geometric center of those graphene grains. Similar size particles were produced by slightly oxidizing the copper surface to obtain oxide nanoparticles in Ar-only environments, followed by reduction into large copper nanoparticles under H2/Ar environment, and are thus explained to be the main constituent nuclei for graphene growth. On this basis, we were able to control the nanoparticle density by adjusting the degree of oxidation and hydrogen annealing duration, thereby controlling nucleation density and consequently controlling graphene grain sizes. In addition, we found that hydrogen plays dual roles on copper morphology during the whole growth process, that is, removing surface irregularities and, at the same...

Turning off hydrogen to realize seeded growth of subcentimeter single-crystal graphene grains on copper.

Hexagonal crystalline ultrathin ReSe2 flakes are synthesized for the first time by a chemical vapor deposition (CVD) method. The as-synthesized ReSe2 flake is revealed as a novel structure, which has mirror-symmetric single-crystal domains inside, by polarization incident Raman and HRTEM. The successful development of the CVD method will facilitate research on the novel anisotropic electronic/optoelectronic properties of ReSe2 in the future.

Lin Gan

Papers

Ultrathin SnSe2 Flakes Grown by Chemical Vapor Deposition for High‐Performance Photodetectors

Two-dimensional layered nanomaterials for gas-sensing applications

Large‐Size Growth of Ultrathin SnS2 Nanosheets and High Performance for Phototransistors

Turning off hydrogen to realize seeded growth of subcentimeter single-crystal graphene grains on copper.

Chemical Vapor Deposition Synthesis of Ultrathin Hexagonal ReSe2 Flakes for Anisotropic Raman Property and Optoelectronic Application