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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

Metal-organic frameworks (MOFs) are an emerging class of porous materials with potential applications in gas storage, separations, catalysis, and chemical sensing. Despite numerous advantages, applications of many MOFs are ultimately limited by their stability under harsh conditions. Herein, the recent advances in the field of stable MOFs, covering the fundamental mechanisms of MOF stability, design, and synthesis of stable MOF architectures, and their latest applications are reviewed. First, key factors that affect MOF stability under certain chemical environments are introduced to guide the design of robust structures. This is followed by a short review of synthetic strategies of stable MOFs including modulated synthesis and postsynthetic modifications. Based on the fundamentals of MOF stability, stable MOFs are classified into two categories: high-valency metal-carboxylate frameworks and low-valency metal-azolate frameworks. Along this line, some representative stable MOFs are introduced, their structures are described, and their properties are briefly discussed. The expanded applications of stable MOFs in Lewis/Bronsted acid catalysis, redox catalysis, photocatalysis, electrocatalysis, gas storage, and sensing are highlighted. Overall, this review is expected to guide the design of stable MOFs by providing insights into existing structures, which could lead to the discovery and development of more advanced functional materials.

Stable Metal-Organic Frameworks: Design, Synthesis, and Applications.

Graphitic carbon nitride (g-CN) is an emerging metal-free photocatalyst for solar energy conversion via water splitting and CO2 fixation. Herein, we used preheated melamine as a starting material in combination with the salt melt method to synthesize a crystalline tri-s-triazine-based g-CN. The as-obtained sample exhibited high stability and photocatalytic activity toward hydrogen and oxygen production from water splitting. In addition, by adding phosphate to mimic natural photosynthetic environment, the apparent quantum yield (AQY) for the hydrogen production reached 50.7% at 405 nm, which is the highest value ever reported for conjugated carbon nitride polymers in hydrogen evolution photocatalysis. The results of this study demonstrate that crystalline covalent tri-s-triazine frameworks hold great promise for solar energy applications.

Tri-s-triazine-Based Crystalline Graphitic Carbon Nitrides for Highly Efficient Hydrogen Evolution Photocatalysis

Polymeric carbon nitride (PCN), in either triazine or heptazine form, has been regarded as a promising metal-free, environmentally benign, and sustainable photocatalyst for solar hydrogen production. However, PCN in most cases only exhibits moderate activity owing to its inherent properties, such as rapid charge carrier recombination. Herein we present a triazine-heptazine copolymer synthesized by simple post-calcination of PCN in eutectic salts, that is, NaCl/KCl, to modulate the polymerization process and optimize the structure. The construction of an internal triazine-heptazine donor-acceptor (D-A) heterostructure was affirmed to significantly accelerate interface charge transfer (CT) and thus boost the photocatalytic activity (AQY=60 % at 420 nm). This study highlights the construction of intermolecular D-A copolymers in NaCl/KCl molten salts with higher melting points but in the absence of lithium to modulate the chemical structure and properties of PCN.

Ionothermal Synthesis of Triazine-Heptazine-Based Copolymers with Apparent Quantum Yields of 60 % at 420 nm for Solar Hydrogen Production from "Sea Water".

https://pubs.rsc.org/en/content/articlepdf/2015/cc/c5cc90254a

Introduction of a mediator for enhancing photocatalytic performance via post-synthetic metal exchange in metal–organic frameworks (MOFs)

In semiconductor-mediated photocatalysis, the optical property of semiconductors is a key parameter and closely related to the conversion efficiency of solar energy. However, endeavors in achieving...

Activation of n → π* Transitions in Two-Dimensional Conjugated Polymers for Visible Light Photocatalysis

The combination of lone-pair effects on Pb2+ cations and the smaller electronegativity of I− anions into the pentaborate framework generates a phase-matchable material, Pb2B5O9I, with the largest powder SHG response among borates, about 13.5 times that of KDP (KH2PO4), and transparency over the near-UV to middle-IR region. DFT calculations on electronic structure and cutoff-energy-dependent SHG coefficients confirm these origins.

Yongfan Zhang

Papers

Tri-s-triazine-Based Crystalline Graphitic Carbon Nitrides for Highly Efficient Hydrogen Evolution Photocatalysis

Ionothermal Synthesis of Triazine-Heptazine-Based Copolymers with Apparent Quantum Yields of 60 % at 420 nm for Solar Hydrogen Production from "Sea Water".

Introduction of a mediator for enhancing photocatalytic performance via post-synthetic metal exchange in metal–organic frameworks (MOFs)

Activation of n → π* Transitions in Two-Dimensional Conjugated Polymers for Visible Light Photocatalysis

Pb2B5O9I: an iodide borate with strong second harmonic generation.