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1,295 results on '"Kim, Il‐Doo"'

457. Single-Atom Pt Stabilized on One-Dimensional Nanostructure Support viaCarbon Nitride/SnO2Heterojunction Trapping

Author

Shin, Hamin, Jung, Wan-Gil, Kim, Dong-Ha, Jang, Ji-Soo, Kim, Yoon Hwa, Koo, Won-Tae, Bae, Jaehyeong, Park, Chungseong, Cho, Su-Ho, Kim, Bong Joong, and Kim, Il-Doo

Abstract

Catalysis with single-atom catalysts (SACs) exhibits outstanding reactivity and selectivity. However, fabrication of supports for the single atoms with structural versatility remains a challenge to be overcome, for further steps toward catalytic activity augmentation. Here, we demonstrate an effective synthetic approach for a Pt SAC stabilized on a controllable one-dimensional (1D) metal oxide nano-heterostructure support, by trapping the single atoms at heterojunctions of a carbon nitride/SnO2heterostructure. With the ultrahigh specific surface area (54.29 m2g–1) of the nanostructure, we obtained maximized catalytic active sites, as well as further catalytic enhancement achieved with the heterojunction between carbon nitride and SnO2. X-ray absorption fine structure analysis and HAADF-STEM analysis reveal a homogeneous atomic dispersion of Pt species between carbon nitride and SnO2nanograins. This Pt SAC system with the 1D nano-heterostructure support exhibits high sensitivity and selectivity toward detection of formaldehyde gas among state-of-the-art gas sensors. Further ex situTEM analysis confirms excellent thermal stability and sinter resistance of the heterojunction-immobilized Pt single atoms.

Published
2020
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458. Hydrogen Sensors Based on MoS2Hollow Architectures Assembled by Pickering Emulsion

Author

Park, Chan Ho, Koo, Won-Tae, Lee, Young Jun, Kim, Yoon Hwa, Lee, Jiyoung, Jang, Ji-Soo, Yun, Hongseok, Kim, Il-Doo, and Kim, Bumjoon J.

Abstract

For rapid hydrogen gas (H2) sensing, we propose the facile synthesis of the hollow structure of Pt-decorated molybdenum disulfide (h-MoS2/Pt) using ultrathin (mono- or few-layer) two-dimensional nanosheets. The controlled amphiphilic nature of MoS2surface produces ultrathin MoS2NS-covered polystyrene particles viaone-step Pickering emulsification. The incorporation of Pt nanoparticles (NPs) on the MoS2, followed by pyrolysis, generates the highly porous h-MoS2/Pt. This hollow hybrid structure produces sufficiently permeable pathways for H2and maximizes the active sites of MoS2, while the Pt NPs on the hollow MoS2induce catalytic H2spillover during H2sensing. The h-MoS2/Pt-based chemiresistors show sensitive H2sensing performances with fast sensing speed (response, 8.1 s for 1% of H2and 2.7 s for 4%; and recovery, 16.0 s for both 1% and 4% H2at room temperature in the air). These results mark the highest H2sensing speed among 2D material-based H2sensors operated at room temperature in air. Our fabrication method of h-MoS2/Pt structure through Pickering emulsion provides a versatile platform applicable to various 2D material-based hollow structures and facilitates their use in other applications involving surface reactions.

Published
2020
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459. Pore-Size-Tuned Graphene Oxide Membrane as a Selective Molecular Sieving Layer: Toward Ultraselective Chemiresistors

Author

Jang, Ji-Soo, Lee, Jiyoung, Koo, Won-Tae, Kim, Dong-Ha, Cho, Hee-Jin, Shin, Hamin, and Kim, Il-Doo

Abstract

Conventional graphene oxide (GO)-based gas membranes, having a narrow pore-size range of less than 0.3 nm, exhibit limited gas molecular permeability because of the kinetic diameters of most volatile organic and sulfur compound (VOCs/VSCs) molecules being larger than 0.3 nm. Here, we employ GO nanosheets (NSs) with a tunable pore-size distribution as a molecular sieving layer on two-dimensional (2D) metal oxide NSs-based gas sensors, i.e., PdO-sensitized WO3NSs to boost selectivity toward specific gas species. The pore size, surface area, and pore density of GO NSs were simply manipulated by controlling H2O2concentration. In addition, the pore size-tuned GO NSs were coated on cellulose filtering paper as a free-standing nanoporous membrane. Holey GO membrane showed a highly selective H2S permeability characteristic, exhibiting superior cross-selectivity to CH3COCH3(0.46 nm), C2H5OH (0.45 nm), and C7H8(0.59 nm) with larger kinetic diameters compared with H2S (0.36 nm). Such pore-size-tuned GO nanoporous layer is scalable and robust, highlighting a great promise for designing low cost and highly efficient gas-permeable membrane for outstanding selective gas sensing platform.

Published
2020
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460. Recent advances in ABO3perovskites: their gas-sensing performance as resistive-type gas sensors

Author

Bulemo, Peresi Majura and Kim, Il-Doo

Abstract

Perovskite-type oxides with general stoichiometry ABO3(A is a lanthanide or alkali earth metal, and B is transition metal) constitute a rich material playground for application as resistive-type gas-sensing layers. Immense interest is triggered by, among other factors, stability of abundant elements (˜?90% in the periodic table) in this stoichiometry, relatively easy tunability of structure and chemical composition, and their off-stoichiometry stability upon doping. Moreover, their capability to host cationic and abundant oxygen vacancies renders them with excellent electrical and redox properties, and synergistic functions that influence their performance. Herein, we present an overview of recent development in the use of ABO3perovskites as resistive-type gas sensors, clearly elucidating current experimental strategies, and sensing mechanisms involved in realization of enhanced sensing performance. Finally, we provide a brief overview of limitations that hamper their potential utilization in gas sensors and suggest new pathways for novel applications of ABO3materials.

Published
2020
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462. Effect of annealing temperature on the interfacial interaction of LiNi0.5Mn1.5O4 thin film cathode with stainless-steel substrate.

Author

Kim, Jong Heon, Park, Jozeph, Park, Kyung, Cho, Su-Ho, Park, Yun Chang, Kim, Chunjoong, Kim, Il-Doo, Park, Kyusung, and Kim, Hyun-Suk

Abstract

LiNi0.5Mn1.5O4 thin films were coated on stainless steel substrates by radio-frequency sputtering at room temperature for a lithium-ion battery. The cathode films were post-annealed at 500, 600 and 700 °C to study (i) the impact of annealing temperature on the crystallization of the cathode film and (ii) the reactivity between the cathode film and the stainless steel substrate. X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy were adopted to characterize the thin films. The electrochemical properties of the LiNi0.5Mn1.5O4 cathodes were investigated with cyclic voltammetry and galvanostatic charge/discharge tests. As the annealing temperature increased from 500 to 600 °C, the crystallinity and electrochemical characteristics of LiNi0.5Mn1.5O4 both improved. However, as the annealing temperature further increased to 700 °C, the phase purity and the electrochemical performance were greatly deteriorated. Combined chemical analyses with time-of-flight secondary ion mass spectrometry depth profiling and energy-dispersive X-ray spectroscopy in scanning transmission electron microscopy mapping have indicated that the cross-diffusion of metal ions between LiNi0.5Mn1.5O4 and the stainless steel substrate takes place at a temperature higher than 600 °C, which was attributed as a main origin of the phase change in the LiNi0.5Mn1.5O4 cathode layer and electrochemistry degradations of lithium-ion battery. [ABSTRACT FROM AUTHOR]

Published
2019
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463. Bio-inspired heterogeneous sensitization of bimetal oxides on SnO2 scaffolds for unparalleled formaldehyde detection.

Author

Jeong, Yong Jin, Kim, Dong-Ha, Jang, Ji-Soo, Kang, Joon-Young, Kim, Rheehyun, and Kim, Il-Doo

Subjects
FORMALDEHYDE, OXIDES, NANOSTRUCTURES, CATALYSTS
Abstract

Multi-heterogeneous oxide sensing layers, i.e., NiO/Fe2O3 catalyst loaded SnO2 fiber-in-tube nanostructures (NiO/Fe2O3–FITs), were rationally synthesized from an electrospinning solution containing a bio-inspired chitosan–bimetal complex template. The NiO/Fe2O3–FITs showed remarkably enhanced sensing properties and superior cross-sensitivity toward sub-ppm levels of formaldehyde. [ABSTRACT FROM AUTHOR]

Published
2019
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465. Highly efficient and stable solid-state Li–O2 batteries using a perovskite solid electrolyte.

Author

Le, Hang T. T., Ngo, Duc Tung, Didwal, Pravin N., Fisher, John G., Park, Choong-Nyeon, Kim, Il-Doo, and Park, Chan-Jin

Abstract

The solid-state Li–O2 battery is considered an ideal candidate for high-performance energy storage because of its high safety, due to use of non-flammable and non-volatile electrolytes, and high specific energy, as it uses Li metal and O2 gas as active materials. We present an original solid-state Li–O2 cell composed of a Li metal anode, a flexible polymer interlayer, a perovskite-structured Al-doped Li–La–Ti–O (A-LLTO) solid electrolyte, and an integrated cathode in which a porous A-LLTO solid electrolyte frame was covered with a carbon layer and CoO nanoparticles as the catalyst for the cyclic oxygen evolution and reduction reactions. The designed solid-state cell operated safely in pure O2 atmosphere at temperatures from 25 °C to 100 °C and delivered the first discharge capacity from 796 mA h gC+CoO−1 to 4035 mA h gC+CoO−1, respectively, at a current density of 0.05 mA cm−2. Notably, at 50 °C, the cell was maintained for 132 cycles under a limited capacity mode of 500 mA h gC+CoO−1 at a high current density of 0.3 mA cm−2, demonstrating the first step of success towards realizing Li batteries with high energy and cyclability, as well as safety. [ABSTRACT FROM AUTHOR]

Published
2019
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466. Gastrodin exerts robust neuroprotection in the postischemic brain via its protective effect against Zn2+-toxicity and its anti-oxidative effects in astrocytes.

Author

Luo, Lidan, Kim, Seung-Woo, Lee, Hye-Kyung, Kim, Il-Doo, Lee, Hahnbie, and Lee, Ja-Kyeong

Subjects
ASTROCYTES, NEURONS, CELLS, NEUROPROTECTIVE agents, DRUGS
Abstract

Gastrodin (GAS) is a predominant bioactive constituent of the Chinese herbal medicine Tianma (Gastrodia elata Blume). Many authors have reported GAS has the beneficial effect on diverse diseases of the CNS, including epilepsy, Alzheimer's disease, Parkinson's disease, and cerebral ischemia. Here, we report GAS exhibited a robust neuroprotective effect in an Sprague-Dawley rat model of stroke (transient middle cerebral artery occlusion, tMCAO), and show that the underlying molecular mechanism involves its protective effect against Zn2+-toxicity and its anti-oxidative effects in astrocytes. Intraperitoneal administration of GAS (40 mg/kg) after MCAO reduced mean infarct volume to 30.1 ± 5.9% of that of MCAO controls and this neuroprotective effect was accompanied by neurological function recoveries which was measured using modified neurological severity score (mNSS). Interestingly, GAS induced up-regulation and nuclear translocation of Nrf2, and subsequently increased the expressions of anti-oxidative genes, such as, HO-1 and GCLM, in astrocytes. Furthermore, GAS co- or pre-treatment markedly suppressed Zn2+-induced cell death caused by excessive ROS production and PARP-1 induction. We found that GAS suppressed p67 expression and PAR formation in astrocytes, which might underlie the anti- Zn2+-toxicity and anti-oxidative effects of GAS in astrocytes. These findings indicate GAS protects astrocytes from Zn2+-induced toxicity and oxidative stress and these effects contribute to its neuroprotective effects in the postischemic brain. [ABSTRACT FROM AUTHOR]

Published
2018
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467. Flash-Induced High-Throughput Porous Graphene via Synergistic Photo-Effects for Electromagnetic Interference Shielding

Author

Lee, Jin Soo, Kim, Jeong-Wook, Lee, Jae Hee, Son, Yong Koo, Kim, Young Bin, Woo, Kyoohee, Lee, Chanhee, Kim, Il-Doo, Seok, Jae Young, Yu, Jong Won, Park, Jung Hwan, and Lee, Keon Jae

Abstract

Highlights:

Flash-induced porous graphene (FPG) was synthesized via a broad-spectrum flash lamp that induced synergistic photo-effects between ultraviolet and visible-near-infrared wavelengths, resulting in large-area synthesis in just a few milliseconds.

A hollow pillar graphene with low sheet resistance of 18 Ω sq−1was produced, exhibiting low density (0.0354 g cm−3) and outstanding absolute electromagnetic interference shielding effectiveness of 1.12 × 105dB cm2g−1.

A lightweight, flexible, and high-throughput FPG is applied for electromagnetic interference shielding of a drone radar system and the human body. Abstract: Porous 2D materials with high conductivity and large surface area have been proposed for potential electromagnetic interference (EMI) shielding materials in future mobility and wearable applications to prevent signal noise, transmission inaccuracy, system malfunction, and health hazards. Here, we report on the synthesis of lightweight and flexible flash-induced porous graphene (FPG) with excellent EMI shielding performance. The broad spectrum of pulsed flashlight induces photo-chemical and photo-thermal reactions in polyimide films, forming 5 × 10 cm2-size porous graphene with a hollow pillar structure in a few milliseconds. The resulting material demonstrated low density (0.0354 g cm−3) and outstanding absolute EMI shielding effectiveness of 1.12 × 105dB cm2g−1. The FPG was characterized via thorough material analyses, and its mechanical durability and flexibility were confirmed by a bending cycle test. Finally, the FPG was utilized in drone and wearable applications, showing effective EMI shielding performance for internal/external EMI in a drone radar system and reducing the specific absorption rate in the human body.

Published
2023
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490. Hybrid crystalline-ITO/metal nanowire mesh transparent electrodes and their application for highly flexible perovskite solar cells

Author

Im, Hyeon-Gyun, primary, Jeong, Seonju, additional, Jin, Jungho, additional, Lee, Jaemin, additional, Youn, Doo-Young, additional, Koo, Won-Tae, additional, Kang, Sin-Bi, additional, Kim, Hyo-Joong, additional, Jang, Junho, additional, Lee, Daewon, additional, Kim, Han-Ki, additional, Kim, Il-Doo, additional, Lee, Jung-Yong, additional, and Bae, Byeong-Soo, additional

Published
2016
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