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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Low-temperature solution-processed photovoltaics suffer from low efficiencies because of poor exciton or electron-hole diffusion lengths (typically about 10 nanometers). Recent reports of highly efficient CH3NH3PbI3-based solar cells in a broad range of configurations raise a compelling case for understanding the fundamental photophysical mechanisms in these materials. By applying femtosecond transient optical spectroscopy to bilayers that interface this perovskite with either selective-electron or selective-hole extraction materials, we have uncovered concrete evidence of balanced long-range electron-hole diffusion lengths of at least 100 nanometers in solution-processed CH3NH3PbI3. The high photoconversion efficiencies of these systems stem from the comparable optical absorption length and charge-carrier diffusion lengths, transcending the traditional constraints of solution-processed semiconductors.

https://dr.ntu.edu.sg/bitstream/10220/16761/1/long-range balanced electron- and hole-transport lengths in organic-inorganic ch3nh3pbi3.pdf

Long-Range Balanced Electron- and Hole-Transport Lengths in Organic-Inorganic CH3NH3PbI3

There is still an ongoing effort to search for sustainable, clean and highly efficient energy generation to satisfy the energy needs of modern society. Among various advanced technologies, electrocatalysis for the oxygen evolution reaction (OER) plays a key role and numerous new electrocatalysts have been developed to improve the efficiency of gas evolution. Along the way, enormous effort has been devoted to finding high-performance electrocatalysts, which has also stimulated the invention of new techniques to investigate the properties of materials or the fundamental mechanism of the OER. This accumulated knowledge not only establishes the foundation of the mechanism of the OER, but also points out the important criteria for a good electrocatalyst based on a variety of studies. Even though it may be difficult to include all cases, the aim of this review is to inspect the current progress and offer a comprehensive insight toward the OER. This review begins with examining the theoretical principles of electrode kinetics and some measurement criteria for achieving a fair evaluation among the catalysts. The second part of this review acquaints some materials for performing OER activity, in which the metal oxide materials build the basis of OER mechanism while non-oxide materials exhibit greatly promising performance toward overall water-splitting. Attention of this review is also paid to in situ approaches to electrocatalytic behavior during OER, and this information is crucial and can provide efficient strategies to design perfect electrocatalysts for OER. Finally, the OER mechanism from the perspective of both recent experimental and theoretical investigations is discussed, as well as probable strategies for improving OER performance with regards to future developments.

Electrocatalysis for the oxygen evolution reaction: recent development and future perspectives

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

Branched nanowires: Synthesis and energy applications

Hollow and hierarchical nanostructures have received wide attention in new-generation, high-performance, lithium ion battery (LIB) applications. Both TiO2 and Fe2O3 are under current investigation because of their high structural stability (TiO2) and high capacity (Fe2O3), and their low cost. Here, we demonstrate a simple strategy for the fabrication of hierarchical hollow TiO2@Fe2O3 nanostructures for the application as LIB anodes. Using atomic layer deposition (ALD) and sacrificial template-assisted hydrolysis, the resulting nanostructure combines a large surface area with a hollow interior and robust structure. As a result, such rationally designed LIB anodes exhibit a high reversible capacity (initial value 840 mAh g−1), improved cycle stability (530 mAh g−1 after 200 cycles at the current density of 200 mA g−1), as well as outstanding rate capability. This ALD-assisted fabrication strategy can be extended to other hierarchical hollow metal oxide nanostructures for favorable applications in electrochemical and optoelectronic devices.

Rationally Designed Hierarchical TiO2@Fe2O3 Hollow Nanostructures for Improved Lithium Ion Storage

Organometal trihalide perovskites have recently emerged as promising materials for low-cost, high-efficiency solar cells. In less than five years, the efficiency of perovskite solar cells (PSC) has been updated rapidly as a result of new strategies adopted in their fabrication process, including device structure, interfacial engineering, chemical compositional tuning, and crystallization kinetics control. To date, the best PSC efficiency has reached 20.1%, which is close to that of single crystal silicon solar cells. However, the stability of PSC devices is still unsatisfactory and is the main bottleneck impeding their commercialization. Here, we summarize recent studies on the degradation mechanisms of organometal trihalide perovskites in PSC devices, and the strategies for stability improvement.

/pdf/recent-advances-in-improving-the-stability-of-perovskite-2ej49y2l6m.pdf

Recent Advances in Improving the Stability of Perovskite Solar Cells

In contemporary years, the increasing demand for high-capacity and safe energy storage has spurred wide attentions in zinc batteries featuring either high voltage, high capacity or both. Despite the extensive research progress, achieving high-energy-density zinc batteries is still challenging and requires a synergy of the multiple factors including reaction mechanisms, electrodes, and electrolytes. In this Review, we comprehensively summarize the rational design strategies, and critically analyze the positive effects and potential issues in optimizing the electrochemistry, cathode materials, electrolytes and device architecture. At the end, the challenges and prospects for the further development of high-energy-density zinc batteries are outlined to guide the research towards new-generation batteries for household appliance, low-speed electric vehicles and large-scale energy storage system.

Design Strategies for High-Energy-Density Aqueous Zinc Batteries.

SnO2 nanowires directly grown on flexible substrates can be a good electrode for a lithium ion battery. However, Sn-based (metal Sn or SnO2) anode materials always suffer from poor stability due to a large volume expansion during cycling. In this work, we utilize atomic layer deposition (ALD) to surface engineer SnO2 nanowires, resulting in a new type of hollowed SnO2-in-TiO2 wire-in-tube nanostructure. This structure has radically improved rate capability and cycling stability compared to both bare SnO2 nanowires and solid SnO2@TiO2 core-shell nanowire electrodes. Typically a relatively stable capacity of 393.3 mAh/g has been achieved after 1000 charge-discharge cycles at a current density of 400 mA/g, and 241.2 mAh/g at 3200 mA/g. It is believed that the uniform hollow TiO2 shell provides stable surface protection and the appropriate-sized gap effectively accommodates the expansion of the interior SnO2 nanowire. This ALD-enabled method should be general to many other battery anode and cathode materials, providing a new and highly reproducible and controllable technique for improving battery performance.

/pdf/highly-stable-and-reversible-lithium-storage-in-sno2-407foh1bz2.pdf

Hong Jin Fan

Papers

Branched nanowires: Synthesis and energy applications

Rationally Designed Hierarchical TiO2@Fe2O3 Hollow Nanostructures for Improved Lithium Ion Storage

Recent Advances in Improving the Stability of Perovskite Solar Cells

Design Strategies for High-Energy-Density Aqueous Zinc Batteries.

Highly Stable and Reversible Lithium Storage in SnO2 Nanowires Surface Coated with a Uniform Hollow Shell by Atomic Layer Deposition