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51.
Yeon Ui Lee Kanghoon Yim Steven Edward Bopp Junxiang Zhao Zhaowei Liu 《Advanced materials (Deerfield Beach, Fla.)》2020,32(28):2002387
Hyperbolic media strengthen numerous attractive applications in optics such as super-resolution imaging, enhanced spontaneous emission, and nanoscale waveguiding. Natural hyperbolic materials exist at visible frequencies; however, implementations of these materials suffer substantial compromises resulting from the high loss in the currently available candidates. Here, the first experimental and theoretical investigation of regioregular poly(3-alkylthiophenes) (rr-P3ATs), a naturally low-loss organic hyperbolic material (OHM) in the visible frequency range, is shown. These hyperbolic properties arise from a highly ordered structure of layered electron-rich conjugated thiophene ring backbones separated by insulating alkyl side chains. The optical and electronic properties of the rr-P3AT can be tuned by controlling the degree of crystallinity and alkyl side chain length. First-principles calculations support the experimental observations, which result from the rr-P3AT's structural and optical anisotropy. Conveniently, rr-P3AT-based OHMs are facile to fabricate, flexible, and biocompatible, which may lead to tremendous new opportunities in a wide range of applications. 相似文献
52.
Hyeongdo Choi Yong Jun Kim Jinseob Song Choong Sun Kim Gyu Soup Lee Seongho Kim Jiwon Park Se Hwan Yim Sang Hyun Park Hye Rim Hwang Min‐Hee Hong Pandiyarasan Veluswamy Byung Jin Cho 《Advanced functional materials》2019,29(20)
Fabricating thermoelectric generators (TEGs) using the screen‐printing process has advantages, including mass production, device scalability, and system applicability. However, the thick film formed through the process typically has low film density, and reduced performance, because of the presence of pores in the film created by the vaporization of the resin during high‐temperature annealing. During the soldering process used for thermoelectric module fabrication, the printed solder infiltrates into the screen‐printed electrodes through the micropores in the electrodes, causing cracks of the electrode film and an increase in resistivity. In this paper, an ultraviolet radiation (UV)‐curable process for screen‐printed electrodes is reported. The paste for the electrodes is synthesized by mixing Ag flakes that can be cured at low temperature with a UV resin. Scanning electron microscope images show that the UV‐curing process significantly reduces pores and thereby results in a smooth‐surfaced electrode layer. The film density after crystallization is also enhanced. TEGs composed of 72 couples with UV‐curable Ag electrodes generate a high power density of ≈6.69 mW cm?2 at a temperature difference of 25 °C; the device resistance is ≈0.75 Ω, and the figure of merit of the device is recorded to be 0.57, which is the highest among the printed TEGs. 相似文献
53.
Gyeonghye Yim Seounghun Kang Hyungjun Kim Young‐Jin Kim Yeong‐Gyu Gil Young‐Kwan Kim Dal‐Hee Min Hongje Jang 《Advanced functional materials》2020,30(9)
The synthesis of nanostructures using homogeneous precursors in the solution phase is widely used to achieve uniformity and well‐defined morphological control. However, drawbacks such as the lack of diversity due to the limited reaction rate modulation exist. One‐step, core–shell nanorod formation using simultaneous covering synthesis using solid and ionic heterogeneous precursors is proposed in this study. A Te‐Bi2Te3/TeO2 core–shell structure is successfully synthesized by precisely controlling various influencing factors, including concentration, temperature, and pH, and its physicochemical and photochemical properties are thoroughly investigated. The proposed nanostructure overcomes the oxidation susceptibility of Te and can be applied to multipotent cancer theranostics in vitro and in vivo in combination with computed tomography imaging. 相似文献
54.
Hyune‐Jea Lee Robert C. Roberts Do Jin Im Se‐Jun Yim Heejin Kim Ji Tae Kim Dong‐Pyo Kim 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(50)
High‐resolution 3D‐printed stainless steel metal microreactors (3D‐PMRs) with different cross‐sectional geometry are fabricated to control ultrafast intramolecular rearrangement reactions in a comparative manner. The 3D‐PMR with circular channel demonstrates the improved controllability in rapid Fries‐type rearrangement reactions, because of the superior mixing efficiency to rectangular cross‐section channels (250 µm × 125 µm) which is confirmed based on the computational flow dynamics simulation. Even in case of very rapid intramolecular rearrangement of sterically small acetyl group occurring in 333 µs of reaction time, the desired intermolecular reaction can outpace to the undesired intramolecular rearrangement using 3D‐PMR to result in high conversion and yield. 相似文献
55.
Minsu Kim Minkyun Son Dong-Bum Seo Jin Kim Moonjeong Jang Dong In Kim Seunghun Lee Soonmin Yim Wooseok Song Sung Myung Jung-Woo Yoo Sun Sook Lee Ki-Seok An 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(22):2206350
The recent introduction of alkali metal halide catalysts for chemical vapor deposition (CVD) of transition metal dichalcogenides (TMDs) has enabled remarkable two-dimensional (2D) growth. However, the process development and growth mechanism require further exploration to enhance the effects of salts and understand the principles. Herein, simultaneous predeposition of a metal source (MoO3) and salt (NaCl) by thermal evaporation is adopted. As a result, remarkable growth behaviors such as promoted 2D growth, easy patterning, and potential diversity of target materials can be achieved. Step-by-step spectroscopy combined with morphological analyses reveals a reaction path for MoS2 growth in which NaCl reacts separately with S and MoO3 to form Na2SO4 and Na2Mo2O7 intermediates, respectively. These intermediates provide a favorable environment for 2D growth, including an enhanced source supply and liquid medium. Consequently, large grains of monolayer MoS2 are formed by self-assembly, indicating the merging of small equilateral triangular grains on the liquid intermediates. This study is expected to serve as an ideal reference for understanding the principles of salt catalysis and evolution of CVD in the preparation of 2D TMDs. 相似文献
56.
Ilhwan Ryu Geunpyo Choe Hyemin Kwon Dajung Hong Sanggyu Yim 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(20):2207270
It is substantially challenging for transition metal oxide nanoparticle (NP)-based electrodes for supercapacitors to achieve high transparency and large capacity simultaneously due to the inherent trade-off between optical transmittance (T) and areal capacitance (CA). This study demonstrates how this trade-off limitation can be overcome by replacing some electrode NPs with transparent tin oxide (SnO2) NPs. Although SnO2 NPs are non-capacitive, they provide effective paths for charge transport, which simultaneously increase the CA and T550nm of the manganese oxide (Mn3O4) NP electrode from 11.7 to 13.4 mF cm−2 and 82.1% to 87.4%, respectively, when 25 wt% of Mn3O4 are replaced by SnO2. The obtained CA values at a given T are higher than those of the transparent electrodes previously reported. An energy storage window fabricated using the mixed-NP electrodes exhibits the highest energy density among transparent supercapacitors previously reported. The improved energy density enables the window to operate various electronic devices for a considerable amount of time, demonstrating its applicability in constructing a reliable and space-efficient building-integrated power supply system. 相似文献
57.
Dong In Kim Soonmin Yim Seulgi Ji Minsu Kim Seunghun Lee Minkyun Son Da Som Song Wooseok Song Taek-Mo Chung Sun Sook Lee Ki-Seok An 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(41):2301395
The precisely tailored refractive index of optical materials is the key to utilizing and manipulating light during its propagation through the matrix, thereby improving their application performances. In this paper, mesoporous metal fluoride films with engineered composition (MgF2:LaF3) are demonstrated to achieve finely tunable refractive indices. These films are prepared using a precursor-derived one-step assembly approach via the simple mixing of precursor solutions (Mg(CF3OO)2 and La(CF3OO)3); then pores are formed simultaneously during solidification owing to the inherent instability of La(CF3OO)3. The mesoporous structures are realized through Mg(CF3OO)2 and La(CF3OO)3 ions, which interacted with each other based on their electrostatic forces, providing a wide range of refractive indices (from 1.37 to 1.16 at 633 nm). Furthermore, it is systematically several MgF2(1-x)-LaF3(x) layers with different compositions (x = 0.0, 0.3, and 0.5) to form the graded refractive index coating that is optically consecutive between the substrate and the air for broadband and omnidirectional antireflection. An average transmittance of ≈98.03% (400–1100 nm) is achieved with a peak transmittance of ≈99.04% (at 571 nm), and the average antireflectivity is maintained at ≈15.75% even at an incidence of light of 65° (400–850 nm). 相似文献
58.
Effective Polysulfide Rejection by Dipole‐Aligned BaTiO3 Coated Separator in Lithium–Sulfur Batteries
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Taeeun Yim Seung Ho Han Nam Hwan Park Min‐Sik Park Ji Hoon Lee Jaeho Shin Jang Wook Choi Yongju Jung Yong Nam Jo Ji‐Sang Yu Ki Jae Kim 《Advanced functional materials》2016,26(43):7817-7823
Although the exceptional theoretical specific capacity (1672 mAh g?1) of elemental sulfur makes lithium–sulfur (Li–S) batteries attractive for upcoming rechargeable battery applications (e.g., electrical vehicles, drones, unmanned aerial vehicles, etc.), insufficient cycle lives of Li–S cells leave a substantial gap before their wide penetration into commercial markets. Among the key features that affect the cyclability, the shuttling process involving polysulfides (PS) dissolution is most fatal. In an effort to suppress this chronic PS shuttling, herein, a separator coated with poled BaTiO3 or BTO particles is introduced. Permanent dipoles that are formed in the BTO particles upon the application of an electric field can effectively reject PS from passing through the separator via electrostatic repulsion, resulting in significantly improved cyclability, even when a simple mixture of elemental sulfur and conductive carbon is used as a sulfur cathode. The coating of BTO particles also considerably suppresses thermal shrinkage of the poly(ethylene) separator at high temperatures and thus enhances the safety of the cell adopting the given separator. The incorporation of poled particles can be universally applied to a wide range of rechargeable batteries (i.e., metal‐air batteries) that suffer from cross‐contamination of charged species between both electrodes. 相似文献
59.
Kan Zhang Jung Kyu Kim Ming Ma Sang Youp Yim Chang‐Lyoul Lee Hyunjung Shin Jong Hyeok Park 《Advanced functional materials》2016,26(25):4527-4534
Photocatalytic hydrogen (H2) evolution requires efficient electron transfer to catalytically active sites in competition with charge recombination. Thus, controlling charge‐carrier dynamics in the photocatalytic H2 evolution process is essential for optimized photocatalyst nanostructures. Here, the efficient delocalization of electrons is demonstrated in a heterostructure consisting of optimized MoS2 tips and CdS nanorods (M‐t‐CdS Nrs) synthesized by amine‐assisted oriented attachment. The heterostructure achieves photocatalytic H2 activity of 8.44 mmol h?1 g?1 with excellent long‐term durability (>23 h) without additional passivation under simulated solar light (AM 1.5, 100 mW cm?2). This activity is nearly two orders of magnitude higher than that of pure CdS Nrs. The impressive photocatalytic H2 activity of M‐t‐CdS Nrs reflects favorable charge‐carrier dynamics, as determined by steady‐state PL and time‐correlated single photon counting correlation analysis at low temperature. The MoS2 cocatalysts precisely located at the end of the CdS Nrs exhibit ultrafast charge transfer and slow charge recombination via spatially localized deeper energy states, resulting in a highly efficient H2 evolution reaction in lactic acid containing an electrolyte. 相似文献
60.
Surface‐Shielding Nanostructures Derived from Self‐Assembled Block Copolymers Enable Reliable Plasma Doping for Few‐Layer Transition Metal Dichalcogenides
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Soonmin Yim Dong Min Sim Woon Ik Park Min‐Jae Choi Jaesuk Choi Jaebeom Jeon Kwang Ho Kim Yeon Sik Jung 《Advanced functional materials》2016,26(31):5631-5640
Precise modulation of electrical and optical properties of 2D transition metal dichalcogenides (TMDs) is required for their application to high‐performance devices. Although conventional plasma‐based doping methods have provided excellent controllability and reproducibility for bulk or relatively thick TMDs, the application of plasma doping for ultrathin few‐layer TMDs has been hindered by serious degradation of their properties. Herein, a reliable and universal doping route is reported for few‐layer TMDs by employing surface‐shielding nanostructures during a plasma‐doping process. It is shown that the surface‐protection oxidized polydimethylsiloxane nanostructures obtained from the sub‐20 nm self‐assembly of Si‐containing block copolymers can preserve the integrity of 2D TMDs and maintain high mobility while affording extensive control over the doping level. For example, the self‐assembled nanostructures form periodically arranged plasma‐blocking and plasma‐accepting nanoscale regions for realizing modulated plasma doping on few‐layer MoS2, controlling the n‐doping level of few‐layer MoS2 from 1.9 × 1011 cm?2 to 8.1 × 1011 cm?2 via the local generation of extra sulfur vacancies without compromising the carrier mobility. 相似文献