107 results on '"Hyungjun Kim"'
Search Results
2. Anion-Induced Interfacial Liquid Layers on LiCoO2 in Salt-in-Water Lithium-Ion Batteries
- Author
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Hyunjeong Oh, Seung-Jae Shin, Eunjin Choi, Hirona Yamagishi, Toshiaki Ohta, Naoaki Yabuuchi, Hun-Gi Jung, Hyungjun Kim, and Hye Ryung Byon
- Published
- 2023
3. Dysprosium Incorporation for Phase Stabilization of Atomic-Layer-Deposited HfO2 Thin Films
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Yujin Lee, Kangsik Kim, Zonghoon Lee, Hong-Sub Lee, Han-Bo-Ram Lee, Woo-Hee Kim, Il-Kwon Oh, and Hyungjun Kim
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General Chemical Engineering ,Materials Chemistry ,General Chemistry - Published
- 2023
4. Effect of Lithium Substitution Ratio of Polymeric Binders on Interfacial Conduction within All-Solid-State Battery Anodes
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Dong Ok Shin, Hyungjun Kim, Jaecheol Choi, Ju Young Kim, Seok Hun Kang, Young-Sam Park, Maenghyo Cho, Yong Min Lee, Kyeongjae Cho, and Young-Gi Lee
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General Materials Science - Published
- 2023
5. Highly Conductive p-Type Transparent Conducting Electrode with Sulfur-Doped Copper Iodide
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Kyunghan Ahn, Ga Hye Kim, Se-Jun Kim, Jihyun Kim, Gi-Seong Ryu, Paul Lee, Byungki Ryu, Jung Young Cho, Yong-Hoon Kim, Joohoon Kang, Hyungjun Kim, Yong-Young Noh, and Myung-Gil Kim
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General Chemical Engineering ,Materials Chemistry ,General Chemistry - Published
- 2022
6. Ionic Liquid-Mediated Route to Atomic Layer Deposition of Tin(II) Oxide via a C–C Bond Cleavage Ligand Modification Mechanism
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Jingwei Shi, Seunggi Seo, Nathaniel J. Schuster, Hyungjun Kim, and Stacey F. Bent
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Colloid and Surface Chemistry ,General Chemistry ,Biochemistry ,Catalysis - Abstract
Atomic layer deposition (ALD) is a technologically important method to grow thin films with high conformality and excellent thickness control from vapor phase precursors. The development of new thermal ALD processes can be limited by precursor reactivity and stability: reaction temperature and precursor design are among the few variables available to achieve higher reactivity in gas-phase reactions, unlike in solution synthesis, where the use of solvent and/or a catalyst can promote a desired reaction. To bridge this synthesis gap between vapor-phase and solution-phase, we demonstrate the use of an ultrathin coating layer of a vapor phase-compatible solvent─an ionic liquid (IL)─on our growth substrate to perform ALD of SnO. Successful SnO deposition is achieved using tin acetylacetonate and water, a process that otherwise would require a stronger counter-reactant such as ozone. The presence of the layer of IL allows a solvent-mediated reaction mechanism to take place on the growth substrate surface. We report a growth per cycle of 0.67 Å/cycle at a deposition temperature of 100 °C in an IL comprising 1-ethyl-3-methylimidazolium hydrogen sulfate. Characterization of the ALD films confirms the SnO film composition, and
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- 2022
7. GW Quasiparticle Energies and Bandgaps of Two-Dimensional Materials Immersed in Water
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Se-Jun Kim, Sébastien Lebègue, Stefan Ringe, and Hyungjun Kim
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General Materials Science ,Physical and Theoretical Chemistry - Abstract
Computational simulations have become of major interest to screen potential photocatalysts for optimal band edge positions which straddle the redox potentials. Unfortunately, these methods suffer from a difficulty in resolving the dynamic solvent response on the band edge positions. We have developed a computational method based on the GW approximation coupled with an implicit solvation model that solves a generalized Poisson equation (GPE), that is, GW-GPE. Using GW-GPE, we have investigated the band edge locations of (quasi) 2D materials immersed in water and found a good agreement with experimental data. We identify two contributions of the solvent effect, termed a "polarization-field effect" and an "environmental screening effect", which are found to be highly sensitive to the atomic and charge distribution of the 2D materials. We believe that the GW-GPE scheme can pave the way to predict band edge positions in solvents, enabling design of 2D material-based photocatalysts and energy systems.
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- 2022
8. Physicochemical Screen Effect of Li Ions in Oxygen Redox Cathodes for Advanced Sodium-Ion Batteries
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Sangeon Park, Gwanghyeon Choi, Jongbeom Kim, Jaewoon Lee, Hyungjun Kim, Maenghyo Cho, and Duho Kim
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General Chemical Engineering ,Materials Chemistry ,General Chemistry - Published
- 2022
9. Electrospun Nanofibrous Membrane-Based Colorimetric Device for Rapid and Simple Screening of Amphetamine-Type Stimulants in Drinks
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Soojin Jang, Seong Uk Son, Byunghoon Kang, Junseok Kim, Jaewoo Lim, Seungbeom Seo, Taejoon Kang, Juyeon Jung, Kyu-Sun Lee, Hyungjun Kim, and Eun-Kyung Lim
- Subjects
Amphetamine ,Nanofibers ,Central Nervous System Stimulants ,Colorimetry ,Analytical Chemistry - Abstract
With the growth of drug-facilitated crimes, prevention has become increasingly important. Although various drug detection technologies exist, most focus on postconsumption detection. However, the prevention of drug-facilitated crimes requires technology for the quick and easy detection of amphetamine-type stimulants (ATSs) before ingestion. Herein, drug screening kits (DSKs) were developed for the simple detection of ATSs in drinks. The DSKs consisted of polydiacetylene nanofiber-based paper sensors fabricated by electrospinning with 10,12-pentacosadiynoic acid (PCDA) and PCDA-dopamine as sensing materials that can bind ATSs via hydrogen bonding and π-π interactions. Dropping a drink on the DSK provided an immediate visual indication of the presence of ATSs. When ATSs were present in the drink, the color of the DSK clearly changed from blue to red, with the increase in red intensity being more than twofold greater than that observed when water alone was tested. Notably, the result could be confirmed by the naked eye without any analytical instrumentation. A color change indicating the presence of ATSs was successfully observed in various alcoholic and nonalcoholic drinks. These results indicate the potential of DSKs for preventing drug-facilitated crimes caused by unwanted drug intake.
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- 2022
10. Enhanced Light Emission through Symmetry Engineering of Halide Perovskites
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Yoonhoo Ha, Jong-Goo Park, Ki-Ha Hong, and Hyungjun Kim
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Colloid and Surface Chemistry ,General Chemistry ,Biochemistry ,Catalysis - Abstract
Metal-halide perovskites (MHPs) have attracted tremendous attention as active materials in optoelectronic devices. For light-emitting diode (LED) applications, nanostructuring of MHPs is considered to be inevitable, but its light-enhancement mechanism is still elusive because the particle (or grain) size is often beyond the quantum confinement regime. As motivated by the experimental finding that the nanostructuring can change the preferred crystalline symmetry from the orthorhombic phase to the high-symmetric cubic phase, we here investigated the carrier dynamics in various polymorphic phases of CsPbBr
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- 2021
11. In Situ Mapping and Local Negative Uptake Behavior of Adsorbates in Individual Pores of Metal–Organic Frameworks
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Sang Rim Shin, Hae Sung Cho, Yongjin Lee, Suji Gim, Yong Min Jung, Hyungjun Kim, Osamu Terasaki, and Jeung Ku Kang
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Colloid and Surface Chemistry ,General Chemistry ,Biochemistry ,Catalysis - Published
- 2021
12. Optical Reflection from Unforbidden Diffraction of Block Copolymer Templated Gyroid Films
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Taesuk Jun, Seung Gi Seo, Du Yeol Ryu, Hyungjun Kim, Seungwoo Lee, Seungyun Jo, and Hui Il Jeon
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Inorganic Chemistry ,Diffraction ,Materials science ,Polymers and Plastics ,business.industry ,Organic Chemistry ,Materials Chemistry ,Copolymer ,Optoelectronics ,business ,Optical reflection ,Gyroid - Abstract
We present material substitutions and optical characterization of block copolymer (BCP)-templated gyroid structures that are obtained from a volume-asymmetric polystyrene
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- 2021
13. PIM-PI-1 and Poly(ethylene glycol)/Poly(propylene glycol)-Based Mechanically Robust Copolyimide Membranes with High CO2-Selectivity and an Anti-aging Property: A Joint Experimental–Computational Exploration
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Yeonho Kim, Sanggil Park, Tae-Hyun Kim, Hyungjun Kim, Asmaul Husna, and Iqubal Hossain
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chemistry.chemical_classification ,Materials science ,Synthetic membrane ,Polymer ,chemistry.chemical_compound ,Membrane ,Chemical engineering ,chemistry ,PEG ratio ,Copolymer ,General Materials Science ,Gas separation ,Selectivity ,Ethylene glycol - Abstract
Polymer membranes with excellent thermomechanical properties and good gas separation performance are desirable for efficient CO2 separation. A series of copolyimide membranes are prepared for the first time using PIM-PI-1, a hard segment with high CO2 permeability, and poly(ethylene glycol)/poly(propylene glycol) (PEG/PPG), a soft segment with high CO2 selectivity. Two different unit polymers are combined to compensate the limitations of each polymer (e.g., the fast aging and moderate selectivity of PIM-PI-1 and the poor mechanical properties and lower permeability of PEG/PPG). The corresponding PIM-(durene-PEG/PPG) membranes exhibit an excellent combination of mechanical properties and gas separation performance compared to the typical PI-PEG-based copolymer membrane. The improved mechanical property is attributed to the unique chain threading and the reinforcement between the spiro unit of PIM and the flexible PEG/PPG at the molecular level, which has not previously been exploited for membranes. The PIM-(durene-PEG/PPG) membranes show a high CO2 permeability of 350-669 Barrer and a high CO2/N2 selectivity of 33.5-40.3. The experimental results are further evaluated with theoretical results obtained from molecular simulation studies, and a very good agreement between the experimental results and simulation results is found. Moreover, the PIM-(durene-PEG/PPG) copolymer membranes display excellent anti-aging performance for up to 1 year.
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- 2021
14. Reaction Mechanisms of Non-hydrolytic Atomic Layer Deposition of Al2O3 with a Series of Alcohol Oxidants
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Whang Je Woo, Seung Gi Seo, Bonggeun Shong, Hwi Yoon, Yujin Lee, Miso Kim, Hyungjun Kim, Il Kwon Oh, and Seung-Min Chung
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Hydrolysis ,Reaction mechanism ,Atomic layer deposition ,chemistry.chemical_compound ,General Energy ,Materials science ,chemistry ,Series (mathematics) ,Alcohol ,Physical and Theoretical Chemistry ,Photochemistry ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Published
- 2021
15. Femtosecond Quantum Dynamics of Excited-State Evolution of Halide Perovskites: Quantum Chaos of Molecular Cations
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Kyeongjae Cho, Yeonghun Lee, Ki-Ha Hong, and Hyungjun Kim
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Physics ,Chemistry ,Quantum dynamics ,Halide ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Quantum chaos ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,Formamidinium ,General Energy ,Chemical bond ,Chemical physics ,Excited state ,Femtosecond ,Molecule ,Molecular orbital ,Density functional theory ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The excited state quantum dynamics of the organic cation in hybrid perovskites are investigated using the time-dependent density functional theory (TDDFT). The time-dependent non-adiabatic bond fluctuation behaviors reveal that the energy relaxation follows different pathways depending on the chemical bonding characteristics and energy transfer modes within the cation molecule, which can fundamentally affect its photostability. For the ammonium-group-containing cations, such as methylammonium (MA) or ethylammonium (EA), local vibrational modes survive for a long time. However, as their lowest unoccupied molecular orbital (LUMO) having π* characters, the amidinium-group-containing cations, such as formamidinium (FA) or guanidinium (GA), efficiently dissipate deposited energy via chaotic intramolecular vibrational energy redistribution (IVR). The distinct dynamic behaviors of A-site molecular cations are closely related to the quantum ergodicity, which can bring enhanced photochemical stability of FA and GA compared to MA and EA. Our theoretical investigation reveals the quantum chaos origin of better light stability of FA-based perovskites and serves the future research direction of the A-site engineering for better solar cells and light-emitting devices.
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- 2021
16. Hydrogen Barriers Based on Chemical Trapping Using Chemically Modulated Al2O3 Grown by Atomic Layer Deposition for InGaZnO Thin-Film Transistors
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Seongil Im, Seung Gi Seo, Won-Jun Choi, Chong Hwon Lee, Choong-Keun Yoo, Joon Young Yang, Hyukjoon Yoo, Taewook Nam, Hyungjun Kim, Hwi Yoon, Dong Wook Choi, Il Kwon Oh, Yujin Lee, Kim Ho-Jin, and Hyun Jae Kim
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010302 applied physics ,Materials science ,Hydrogen ,Stacking ,chemistry.chemical_element ,02 engineering and technology ,Trapping ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic layer deposition ,Chemical species ,Chemical engineering ,chemistry ,Thin-film transistor ,0103 physical sciences ,Degradation (geology) ,General Materials Science ,0210 nano-technology ,Deposition (law) - Abstract
In this study, the excellent hydrogen barrier properties of the atomic-layer-deposition-grown Al2O3 (ALD Al2O3) are first reported for improving the stability of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). Chemical species in Al2O3 were artificially modulated during the ALD process using different oxidants, such as H2O and O3 (H2O-Al2O3 and O3-Al2O3, respectively). When hydrogen was incorporated into the H2O-Al2O3-passivated TFT, a large negative shift in Vth (ca. -12 V) was observed. In contrast, when hydrogen was incorporated into the O3-Al2O3-passivated TFT, there was a negligible shift in Vth (ca. -0.66 V), which indicates that the O3-Al2O3 has a remarkable hydrogen barrier property. We presented a mechanism for trapping hydrogen in a O3-Al2O3 via various chemical and electrical analyses and revealed that hydrogen molecules were trapped by C-O bonds in the O3-Al2O3, preventing the inflow of hydrogen to the a-IGZO. Additionally, to minimize the deterioration of the pristine device that occurs after a barrier deposition, a bi-layered hydrogen barrier by stacking H2O- and O3-Al2O3 is adopted. Such a barrier can provide ultrastable performance without degradation. Therefore, we envisioned that the excellent hydrogen barrier suggested in this paper can provide the possibility of improving the stability of devices in various fields by effectively blocking hydrogen inflows.
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- 2021
17. Dynamic Transformation of a Ag+-Coordinated Supramolecular Nanostructure from a 1D Needle to a 1D Helical Tube via a 2D Ribbon Accompanying the Conversion of Complex Structures
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Ka Young Kim, Jong Hwa Jung, Shim Sung Lee, Jaeheung Cho, Hyeonju Lee, Jaehyeon Park, Younwoo Park, Sung Ho Jung, Hyungjun Kim, and Jeong Sang Oh
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Circular dichroism ,Nanostructure ,Ligand ,Ribbon diagram ,Supramolecular chemistry ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,Bipyridine ,Colloid and Surface Chemistry ,Monomer ,chemistry ,Ribbon - Abstract
We report a unique dynamic morphology transformation of a Ag+-coordinated supramolecular nanostructure accompanying the conversion of complex structures in aqueous solution. In the presence of AgNO3 (1.0 equiv), the achiral bipyridine-based ligand 1G, possessing hydrazine and glycine moieties, preferentially generated a 1D needle-like structure (nanostructure I) based on the 1GAgNO3 complex (1G:Ag+ = 1:1) as a metastable product. Nanostructure I was then transformed into nanostructure II, which was composed of the 1G3Ag2(NO3)2 complex (1G:Ag+ = 3:2) as the thermodynamically stable product. This nanostructure exhibited a 1D helical tubular structure with a uniform diameter via a 2D ribbon as an intermediator, which led to the generation of a circular dichroism (CD) signal with right-handed (P-type) helicity. The observed dynamic transformation was attributed to formation of the thermodynamically favored helical 1G3Ag2(NO3)2 complex. In addition, the helical 1G3Ag2(NO3)2 complex acted as an initiator in the transformation from the 1D needle-like structure to the 1D helical tube via a 2D ribbon. The enhanced ΔG° value of nanostructure II compared to that of nanostructure I confirmed that nanostructure II is thermodynamically stable. More importantly, the transformation of supramolecular nanostructure I to nanostructure II occurred via an "on" pathway, even though the 1GAgNO3 complex was converted to the 1G3Ag2(NO3)2 complex, which did not involve dissociation from nanostructure I into the monomeric 1GAgNO3 complex species. In the kinetic study, the NO3- anion was found to act as an accelerator for the dynamic transformation from nanostructure I to nanostructure II. This result provides the first example of a dynamic transformation of a 1D needle-like structure into a 1D tubular structure via a 2D ribbon structure, accompanied by the conversion of a complex structure and the generation of a large CD signal for the metallo-supramolecular nanostructure. This study may open up new avenues to the understanding of a dynamic morphology transformation process in biological systems.
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- 2021
18. Spin-Flip Density Functional Theory for the Redox Properties of Organic Photoredox Catalysts in Excited States
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Jiyoon Choi and Hyungjun Kim
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Physics ,010304 chemical physics ,Exciton ,Time-dependent density functional theory ,Electron ,Energy minimization ,01 natural sciences ,Chemical space ,Computer Science Applications ,symbols.namesake ,Chemical physics ,Excited state ,Stokes shift ,0103 physical sciences ,symbols ,Density functional theory ,Physical and Theoretical Chemistry - Abstract
Photoredox catalysts (PCs) have contributed to the advancement of organic chemistry by accelerating conventional reactions and enabling new pathways through the use of reactive electrons in excited states. With a number of successful applications, chemists continue to seek new promising organic PCs to achieve their objectives. Instead of labor-intensive manual experimentation, quantum chemical simulations could explore the enormous chemical space more efficiently. The reliability and accuracy of quantum chemical simulations have become important factors for material screening. We designed a theoretical protocol capable of predicting redox properties in excited states with high accuracy for a selected model system of dihydroquinoxalino[2,3-b]quinoxaline derivatives. Herein, three factors were considered as critical to achieving reliable predictions with accurate physics: the solvent medium effect on excited-state geometries, an adequate amount of Hartree-Fock exchange (HFX), and the consideration of double-excitation character in excited states. We determined that it is necessary to incorporate solvent medium during geometry optimizations to obtain planar excited-state structures that are consistent with the experimentally observed modest Stokes shift. While density functionals belonging to the generalized gradient approximation family perform well for the prediction of photoelectrochemical properties, an incorrect description of exciton boundedness (spontaneous dissociation of excitons or extremely weak boundedness) on small organic molecules was predicted. The inclusion of an adequate amount of Hartree-Fock exchange was suggested as one approach to obtain bound excitons, which is physically reasonable. The last consideration is the double-excitation character in S1 states. As revealed by the second-order algebraic diagrammatic construction theory, non-negligible double excitations exist in S1 states in our model systems. Time-dependent density functional theory (TDDFT) is blind to doubly excited states, and this motivated us to use spin-flip DFT (SF-DFT). We established a theoretical protocol that could provide highly accurate estimations of photophysical properties and ground-/excited-state redox properties, focusing on the three factors mentioned above. Geometry optimization with DFT and TDDFT employing the B3LYP functional (20% HFX) in solution and energy refinement by SF-DFT reproduced the experimental redox properties in the excited and ground states remarkably well with mean signed deviations (MSDs) of 0.01 and -0.15 V, respectively. This theoretical protocol is expected to contribute to the understanding of exciton behavior in organic PCs and to the efficient design of new promising PC candidates.
- Published
- 2021
19. Theoretical Engineering of Singlet Fission Kinetics in Perylene Bisimide Dimer with Chromophore Rotation
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Yongseok Hong, Dongho Kim, Hyungjun Kim, and Juno Kim
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chemistry.chemical_compound ,Chemistry ,Superexchange ,Dimer ,Exciton ,Singlet fission ,Density functional theory ,Physical and Theoretical Chemistry ,Chromophore ,Wave function ,Molecular physics ,Perylene - Abstract
We investigated the potential of chromophore's rotations to tune singlet fission (SF) kinetics in perylene bisimide (PBI) dimers in addition to relative horizontal displacements. The total number of 250 PBI dimers (five displacements along the long and short axis of PBI, respectively, and ten rotation angle changes from parallel to perpendicular alignment) was examined. Ground-state energies showed that dimer formation is favored in all orientations with some differences in interaction strength. Time-dependent density functional theory predicted S1 and T1 excitons' energy, and the thermodynamic feasibility of SF process was judged by the energy difference between a S1 exciton and twice of T1 excitons. In addition, we also estimated the relative rate of multiexciton generation step by the three-state kinetic model with the results of restricted active space employing double spin-flip. Nine promising orientations including two parallel PBI dimers and seven twisted ones were discussed. Wave function composition analysis showed that SF occurs mainly through the superexchange mechanism in various twisted PBI dimers, but the direct two-electron and coherent pathway could be operative at the particular positions. Quantum chemical simulations suggested the rotation as an effective tool to tune SF efficiency in PBI dimers, which is helpful to substantiate more efficient SF material.
- Published
- 2021
20. Identification of Single-Atom Ni Site Active toward Electrochemical CO2 Conversion to CO
- Author
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Min Wook Chung, Sung June Cho, Hyung Suk Oh, Da Hye Won, Junseong Lee, Woojin Yang, Ji Yeon Ryu, Jiwon Seo, Haesol Kim, Dongyup Shin, Hyungjun Kim, Sun Hee Kim, Donghyuk Jeong, Chang Hyuck Choi, and Keun Hwa Chae
- Subjects
Electrolysis ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,Electrochemistry ,01 natural sciences ,Biochemistry ,Redox ,Catalysis ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,law ,Tetraphenylporphyrin ,Atom ,High activity ,Carbon - Abstract
Electrocatalytic conversion of CO2 into value-added products offers a new paradigm for a sustainable carbon economy. For active CO2 electrolysis, the single-atom Ni catalyst has been proposed as promising from experiments, but an idealized Ni-N4 site shows an unfavorable energetics from theory, leading to many debates on the chemical nature responsible for high activity. To resolve this conundrum, here we investigated CO2 electrolysis of Ni sites with well-defined coordination, tetraphenylporphyrin (N4-TPP) and 21-oxatetraphenylporphyrin (N3O-TPP). Advanced spectroscopic and computational studies revealed that the broken ligand-field symmetry is the key for active CO2 electrolysis, which subordinates an increase in the Ni redox potential yielding NiI. Along with their importance in activity, ligand-field symmetry and strength are directly related to the stability of the Ni center. This suggests the next quest for an activity-stability map in the domain of ligand-field strength, toward a rational ligand-field engineering of single-atom Ni catalysts for efficient CO2 electrolysis.
- Published
- 2021
21. Design of an Ultrastable and Highly Active Ceria Catalyst for CO Oxidation by Rare-Earth- and Transition-Metal Co-Doping
- Author
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Myeong Gon Jang, Hyungjun Kim, Dongjae Shin, Jeong Woo Han, Hojin Jeong, and Hyunjoo Lee
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Materials science ,Transition metal ,Chemical engineering ,Doping ,Rare earth ,High activity ,General Chemistry ,Catalysis - Abstract
Catalyst design with good stability beyond simply having high activity is crucial for a variety of reactions. Here, we evaluate the ceria catalyst for CO oxidation as a model reaction to rationally...
- Published
- 2020
22. Unveiling Electrode–Electrolyte Design-Based NO Reduction for NH3 Synthesis
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Monika Sharma, Juheon Heo, Youngkook Kwon, Hankwon Lim, Jung-Ae Lim, Hyungjun Kim, Iljeong Heo, Boreum Lee, Dongyup Shin, Beom-Sik Kim, Hyung Mo Jeong, In-Hwan Oh, Hyungseob Lim, and Dong Yeon Kim
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Materials science ,Renewable Energy, Sustainability and the Environment ,Energy conversion efficiency ,Energy Engineering and Power Technology ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Redox ,0104 chemical sciences ,Reduction (complexity) ,Ammonia ,chemistry.chemical_compound ,Fuel Technology ,chemistry ,Chemical engineering ,Chemistry (miscellaneous) ,Scientific method ,Electrode ,Materials Chemistry ,0210 nano-technology - Abstract
The electrochemical N2 reduction reaction has attracted interest as a potential alternative to the Haber–Bosch process, but a significantly low conversion efficiency and a significantly low ammonia...
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- 2020
23. Origin of Fluoropolymer Affinity toward Water and Its Impact on Membrane Performance
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Jeong F. Kim, Sanggil Park, You-In Park, Hyeon Jun Heo, Hyungjun Kim, Young Hoon Cho, Hosik Park, Eunsung Yi, Aatif Ali Shah, Eun-Ho Sohn, and Seung-Eun Nam
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chemistry.chemical_compound ,Membrane ,Polymers and Plastics ,Chemical engineering ,Chemistry ,Process Chemistry and Technology ,Organic Chemistry ,Fluorine ,Fluoropolymer ,Polar ,chemistry.chemical_element ,Membrane distillation ,Electrospinning - Abstract
Fluoropolymers exhibit very high hydrophobicity because of the presence of fluorine groups. However, they sometimes exhibit peculiar polarity—referred to as “polar hydrophobicity”—depending on thei...
- Published
- 2020
24. FexNi2–xP Alloy Nanocatalysts with Electron-Deficient Phosphorus Enhancing the Hydrogen Evolution Reaction in Acidic Media
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Dongwoo Shin, Hyunjoon Song, Hyungjun Kim, Sang-Il Choi, Heejin Kim, Min-Jun Kim, and Dongyup Shin
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Materials science ,010405 organic chemistry ,Pure metals ,Phosphorus ,Alloy ,chemistry.chemical_element ,General Chemistry ,Electron ,engineering.material ,010402 general chemistry ,01 natural sciences ,Catalysis ,Nanomaterial-based catalyst ,0104 chemical sciences ,Condensed Matter::Materials Science ,Chemical engineering ,chemistry ,engineering ,Hydrogen evolution - Abstract
Alloying is one of the powerful methods to exceed the intrinsic properties of pure metals, however, it is challenging to understand the exact alloying effect without altering other parameters, such...
- Published
- 2020
25. Intermetallic PtCu Nanoframes as Efficient Oxygen Reduction Electrocatalysts
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Minki Jun, Hu Young Jeong, Kwangyeol Lee, Yoonhoo Ha, Taehyun Kwon, Hionsuck Baik, Ho Young Kim, Hyungjun Kim, and Sang Hoon Joo
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Materials science ,Mechanical Engineering ,Alloy ,Intermetallic ,Active surface area ,chemistry.chemical_element ,Bioengineering ,02 engineering and technology ,General Chemistry ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Electrocatalyst ,Oxygen ,Oxygen reduction ,Catalysis ,Chemical engineering ,chemistry ,engineering ,Oxygen reduction reaction ,General Materials Science ,0210 nano-technology - Abstract
Nanoframe alloy structures represent a class of high-performance catalysts for the oxygen reduction reaction (ORR), owing to their high active surface area, efficient molecular accessibility, and nanoconfinement effect. However, structural and chemical instabilities of nanoframes remain an important challenge. Here, we report the synthesis of PtCu nanoframes constructed with an atomically ordered intermetallic structure (
- Published
- 2020
26. Operando Stability of Platinum Electrocatalysts in Ammonia Oxidation Reactions
- Author
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Haesol Kim, Woong Lee, Chang Hyuck Choi, Man Ho Han, Jiwon Seo, Cheolho Jeon, Kug-Seung Lee, Woojin Yang, Joonhee Moon, Hyung Suk Oh, Keun Hwa Chae, Hyungjun Kim, Sang Gu Ji, and Donghyun Kim
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010405 organic chemistry ,business.industry ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Redox ,Catalysis ,0104 chemical sciences ,Ammonia ,chemistry.chemical_compound ,chemistry ,Alternative energy ,Platinum ,business - Abstract
Ammonia has recently received considerable attention as an alternative energy carrier and a carbon-neutral fuel. In this future energy scenario, the ammonia oxidation reaction (AOR) is a pivotal pr...
- Published
- 2020
27. Thermal Transformation of Molecular Ni2+–N4 Sites for Enhanced CO2 Electroreduction Activity
- Author
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Yun Jeong Hwang, Hu Young Jeong, Sang Hoon Joo, Young Jin Sa, Dongyup Shin, Stefan Ringe, Hyejin Jung, and Hyungjun Kim
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inorganic chemicals ,010405 organic chemistry ,Chemistry ,Inorganic chemistry ,Thermal transformation ,chemistry.chemical_element ,General Chemistry ,010402 general chemistry ,Electrochemistry ,01 natural sciences ,Local structure ,Catalysis ,0104 chemical sciences ,Nickel ,Oxidation state ,Carbon ,Electrochemical reduction of carbon dioxide - Abstract
Atomically dispersed nickel sites complexed on nitrogen-doped carbon (Ni–N/C) have demonstrated considerable activity for the selective electrochemical carbon dioxide reduction reaction (CO2RR) to ...
- Published
- 2020
28. Electric Field Mediated Selectivity Switching of Electrochemical CO2 Reduction from Formate to CO on Carbon Supported Sn
- Author
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Seoktae Kang, Mi-Young Lee, Stefan Ringe, Youngkook Kwon, and Hyungjun Kim
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Renewable Energy, Sustainability and the Environment ,Formic acid ,Inorganic chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Reduction (complexity) ,chemistry.chemical_compound ,Fuel Technology ,chemistry ,Chemistry (miscellaneous) ,Electric field ,Materials Chemistry ,Formate ,0210 nano-technology ,Tin ,Selectivity ,Carbon - Abstract
Decades of electrochemical CO2 reduction research have led to established rules about the product selectivity, i.e., bare tin yields formic acid as the main product. Here, we present Sn nanoparticl...
- Published
- 2020
29. Activity–Stability Relationship in Au@Pt Nanoparticles for Electrocatalysis
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Bongjin Simon Mun, Ji Mun Yoo, Kug-Seung Lee, Yung-Eun Sung, Seung Ho Yu, Hyeonju Lee, Sung Jong Yoo, Dong Young Chung, Huanxin Ju, Mahdi Ahmadi, Docheon Ahn, Hyungjun Kim, Héctor D. Abruña, Young Hoon Chung, and Subin Park
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Materials science ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrocatalyst ,01 natural sciences ,0104 chemical sciences ,Fuel Technology ,Chemistry (miscellaneous) ,Materials Chemistry ,Oxygen reduction reaction ,Pt nanoparticles ,0210 nano-technology - Abstract
Despite breakthroughs in the activity of electrocatalysts for the oxygen reduction reaction (ORR), the development of nanoscale ORR electrocatalysts is still hindered by their instability. Here, to...
- Published
- 2020
30. Experimental, Structural, and Computational Investigation of Mixed Metal–Organic Frameworks from Regioisomeric Ligands for Porosity Control
- Author
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Min Kim, Younghu Son, Myung Hwan Park, Dopil Kim, Hyungjun Kim, Youngik Kim, Jiyoon Choi, Dong-Wook Kim, Hyeonbin Ha, Youngjo Kim, and Minyoung Yoon
- Subjects
Materials science ,010405 organic chemistry ,Ligand ,Binding energy ,General Chemistry ,DABCO ,010402 general chemistry ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,Adsorption ,chemistry ,General Materials Science ,Carboxylate ,Porosity ,Porous medium ,Octane - Abstract
Porosity control and structural analysis of metal–organic frameworks (MOFs) can be achieved using regioisomeric ligand mixtures. While ortho-dimethoxy-functionalized MOFs yielded highly porous structures and para-dimethoxy-functionalized MOFs displayed almost nonporous properties in their N2 isotherms after evacuation, regioisomeric ligand-mixed MOFs showed variable N2 uptake amount and surface area depending on the ligand-mixing ratio. The quantity of N2 absorbed was tuned between 20 and 300 cm3/g by adjusting the ligand-mixing ratio. Both experimental analysis and computational modeling were performed to understand the porosity differences between ortho- and para-dimethoxy-functionalized MOFs. Detailed structural analysis using X-ray crystallographic data revealed significant differences in the coordination environments of DMOF-[2,3-(OMe)2] and DMOF-[2,5-(OMe)2] (DMOF = dabco MOF, dabco = 1,4-diazabicyclo[2.2.0]octane). The coordination bond between Zn2+ and carboxylate in the ortho-functionalized DMOF-[2,3-(OMe)2] was more rigid than that in the para-functionalized DMOF-[2,5-(OMe)2]. Quantum-chemical simulation also showed differences in the coordination environments of Zn secondary building unit surrounded by methoxy-functionalized ligands and pillar ligands. In addition, the binding energy differences between Zn2+ and regioisomeric ligands (ortho- and para-dimethoxy-functionalized benzene-1,4-dicarboxylates) explained the rigidity and porosity changes of the mixed MOFs upon evacuation and perfectly matched with experimental N2 adsorption and X-ray crystallography data.
- Published
- 2020
31. Water Slippage on Graphitic and Metallic Surfaces: Impact of the Surface Packing Structure and Electron Density Tail
- Author
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Kang Jin Cho, Hyung-Kyu Lim, Hyungjun Kim, Changho Kim, and Suji Gim
- Subjects
Surface (mathematics) ,Electron density ,Materials science ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Metal ,General Energy ,Chemical physics ,visual_art ,visual_art.visual_art_medium ,Fluid dynamics ,Slippage ,Physical and Theoretical Chemistry ,ComputingMethodologies_COMPUTERGRAPHICS - Abstract
While fluid flow on solid-liquid interfaces has been of great interest, studying its behavior is challenging because it requires a comprehensive understanding of the complex interactions that exist...
- Published
- 2020
32. Thermodynamics of Multicomponent Perovskites: A Guide to Highly Efficient and Stable Solar Cell Materials
- Author
-
Taedaehyeong Eom, Ki-Ha Hong, Sungmin Kim, Ye-Seol Ha, and Hyungjun Kim
- Subjects
Materials science ,General Chemical Engineering ,Nanotechnology ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,law ,Solar cell ,Materials Chemistry ,0210 nano-technology ,Perovskite (structure) - Abstract
With their dramatic improvement of photoconversion efficiency, metal-halide perovskite (MHP) solar cells are receiving great attention. For successful deployment of these materials as next-generati...
- Published
- 2020
33. A General Strategy to Atomically Dispersed Precious Metal Catalysts for Unravelling Their Catalytic Trends for Oxygen Reduction Reaction
- Author
-
Dongyup Shin, Hu Young Jeong, Yong-Tae Kim, Tae Joo Shin, Du San Baek, Ja Hun Kwak, Sang Hoon Joo, Jaekyoung Lee, Hyungjun Kim, and Jae Hyung Kim
- Subjects
Materials science ,General Engineering ,Oxide ,General Physics and Astronomy ,Nanoparticle ,chemistry.chemical_element ,Precious metal ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Water-gas shift reaction ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,General Materials Science ,0210 nano-technology ,Selectivity ,Platinum ,Carbon - Abstract
Atomically dispersed precious metal catalysts have emerged as a frontier in catalysis. However, a robust, generic synthetic strategy toward atomically dispersed catalysts is still lacking, which has limited systematic studies revealing their general catalytic trends distinct from those of conventional nanoparticle (NP)-based catalysts. Herein, we report a general synthetic strategy toward atomically dispersed precious metal catalysts, which consists of "trapping" precious metal precursors on a heteroatom-doped carbonaceous layer coated on a carbon support and "immobilizing" them with a SiO2 layer during thermal activation. Through the "trapping-and-immobilizing" method, five atomically dispersed precious metal catalysts (Os, Ru, Rh, Ir, and Pt) could be obtained and served as model catalysts for unravelling catalytic trends for the oxygen reduction reaction (ORR). Owing to their isolated geometry, the atomically dispersed precious metal catalysts generally showed higher selectivity for H2O2 production than their NP counterparts for the ORR. Among the atomically dispersed catalysts, the H2O2 selectivity was changed by the types of metals, with atomically dispersed Pt catalyst showing the highest selectivity. A combination of experimental results and density functional theory calculations revealed that the selectivity trend of atomically dispersed catalysts could be correlated to the binding energy difference between *OOH and *O species. In terms of 2 e- ORR activity, the atomically dispersed Rh catalyst showed the best activity. Our general approach to atomically dispersed precious metal catalysts may help in understanding their unique catalytic behaviors for the ORR.
- Published
- 2020
34. Reductive Electrophotocatalysis: Merging Electricity and Light To Achieve Extreme Reduction Potentials
- Author
-
Hyunwoo Kim, Song Lin, Tristan H. Lambert, and Hyungjun Kim
- Subjects
Materials science ,business.industry ,Chemistry ,Aryl ,Radical ,Photoredox catalysis ,General Chemistry ,Photochemistry ,010402 general chemistry ,Borylation ,01 natural sciences ,Biochemistry ,Article ,Catalysis ,Ion ,0104 chemical sciences ,Power (physics) ,Reduction (complexity) ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Excited state ,Electricity ,Process engineering ,business - Abstract
We describe a new electrophotocatalytic strategy that harnesses the power of light and electricity to generate an excited radical anion with a reducing potential of –3.2 V vs. SCE, which can be used to activate substrates with very high reduction potentials (Ered ~ –1.9 to –2.9 V). The resultant aryl radicals can be engaged in various synthetically useful transformations to furnish arylboronate, arylstannane, and biaryl products.
- Published
- 2020
35. Size-Controlled Pd Nanoparticles Loaded on Co3O4 Nanoparticles by Calcination for Enhanced CO Oxidation
- Author
-
Rui Huang, Jeong Woo Han, Hyungjun Kim, Kyeounghak Kim, and Myeong Gon Jang
- Subjects
Materials science ,Catalytic oxidation ,Chemical engineering ,law ,Pd nanoparticles ,Nanoparticle ,General Materials Science ,Calcination ,Density functional theory ,Particle size ,Cobalt oxide ,law.invention - Abstract
In accordance with Euro 6 emission standards, exhaust emissions are required to be substantially lowered especially via significant improvement in the efficiency of catalytic oxidation to reduce to...
- Published
- 2019
36. Selectivity Modulated by Surface Ligands on Cu2O/TiO2 Catalysts for Gas-Phase Photocatalytic Reduction of Carbon Dioxide
- Author
-
Gil-Seong Kang, Hyunjoo Lee, Doh C. Lee, Woo Jae Kim, Sungho Lee, Sunil Jeong, Young Lee, Hyung-Kyu Lim, Chanyeon Kim, Gui Min Kim, and Hyungjun Kim
- Subjects
Passivation ,Chemistry ,Nanoparticle ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Catalysis ,chemistry.chemical_compound ,General Energy ,Adsorption ,Nanocrystal ,Carbon dioxide ,Photocatalysis ,Physical and Theoretical Chemistry ,0210 nano-technology ,Selectivity - Abstract
We report gas-phase photocatalytic CO2 reduction with Cu2O/TiO2 photocatalysts of varying surface passivation. With taurine adsorbed on the photocatalyst surface, the CH4 production rate increases ...
- Published
- 2019
37. Activity Origin and Multifunctionality of Pt-Based Intermetallic Nanostructures for Efficient Electrocatalysis
- Author
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Tae Joo Shin, Jinwoo Woo, Jin Young Kim, Hu Young Jeong, Ayoung Byun, Hyungjun Kim, Ho-Young Kim, Yoonhoo Ha, Kang Hyun Park, Jong Min Kim, and Sang Hoon Joo
- Subjects
Materials science ,Nanostructure ,010405 organic chemistry ,Alloy ,Intermetallic ,Proton exchange membrane fuel cell ,General Chemistry ,Mesoporous silica ,engineering.material ,010402 general chemistry ,Electrocatalyst ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Metal ,Chemical engineering ,visual_art ,visual_art.visual_art_medium ,engineering - Abstract
Pt-based intermetallic nanostructures have demonstrated higher electrocatalytic performances compared to random alloy structures. However, the origin of their enhanced catalytic properties remains ...
- Published
- 2019
38. Improved Sensitivity in Schottky Contacted Two-Dimensional MoS2 Gas Sensor
- Author
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Jusang Park, Youngjun Kim, Nan Cho Oh, Hyungjun Kim, Soo Min Lee, Sang Koo Kang, and Hi Deok Lee
- Subjects
Electrode material ,Materials science ,business.industry ,Schottky barrier ,Schottky diode ,02 engineering and technology ,Chemical vapor deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Responsivity ,chemistry.chemical_compound ,chemistry ,Optoelectronics ,General Materials Science ,Electronics ,0210 nano-technology ,business ,Sensitivity (electronics) ,Molybdenum disulfide - Abstract
Two-dimensional (2D) transition-metal dichalcogenides have attracted significant attention as gas-sensing materials owing to their superior responsivity at room temperature and their possible application as flexible electronic devices. Especially, reliable responsivity and selectivity for various environmentally harmful gases are the main requirements for the future chemiresistive-type gas sensor applications. In this study, we demonstrate improved sensitivity of a 2D MoS2-based gas sensor by controlling the Schottky barrier height. Chemical vapor deposition process was performed at low temperature to obtain layer-controlled 2D MoS2, and the NO2 gas responsivity was confirmed by the fabricated gas sensor. Then, the number of MoS2 layers was fixed and the types of electrode materials were varied for controlling the Schottky barrier height. As the Schottky barrier height increased, the NO2 responsivity increased, and it was found to be effective for CO and CO2 gases, which had little reactivity in 2D MoS2-b...
- Published
- 2019
39. Alkali Cation Effect on CO2 Electroreduction to CO: A Local Colligative Property
- Author
-
Seung-Jae Shin, Hansol Choi, Stefan Ringe, Da Hye Won, Chang Hyuck Choi, and Hyungjun Kim
- Abstract
Converting carbon dioxide (CO2) into valuable products is one of the most important processes for a sustainable society. Especially, the electrochemical CO2 reduction reaction (CO2RR) offers an effective means, but its reaction mechanism is not yet fully understood. Here, we demonstrate that cation-coupled electron transfer (CCET) is a rate-determining step in the CO2RR to carbon monoxide. The first-principles-based multiscale simulation identifies a single cation that coordinates a CO2− intermediate adsorbed on Ag electrode. The CCET is experimentally verified by a collapse of the CO2RR polarization curves upon correcting Nernstianly for a bulk cation concentration. As further confirmation, a kinetic study shows that the CO2RR obeys first-order kinetics on a local cation concentration. Finally, this work unveils that the cation effect on CO2RR originates from the local colligative property, and further highlights the importance of ion-pairing tendency for electrochemical interface design to achieve high-performance CO2 electrolysis.
- Published
- 2021
40. Improved CO Oxidation via Surface Stabilization of Ceria Nanoparticles Induced by Rare-Earth Metal Dopants
- Author
-
Kyeounghak Kim, Kyung-Jong Noh, Hyungjun Kim, Dongjae Shin, and Jeong Woo Han
- Subjects
Metal ,Materials science ,Dopant ,Chemical engineering ,Intrinsic activity ,visual_art ,Specific surface area ,Rare earth ,visual_art.visual_art_medium ,Nanoparticle ,General Materials Science ,Catalysis - Abstract
Rare earth (RE) metals have often been used as dopants to improve the catalytic activity of ceria. However, their exact role in the activity of ceria catalyst has not been clearly identified. Combining experimental and theoretical approaches, we extensively investigate CO oxidation as a model reaction on RE-doped ceria (REC). The apparent activity is linearly proportional to the specific surface area (AS), which is enlarged by RE dopants as a consequence of surface stabilization. To decouple the effect of each RE dopant on the surface inherent activity, we set AS of REC to be almost constant by adjusting the pH during synthesis. In this case, however, pure ceria shows higher activity than any REC. We therefore conclude that although the RE dopants have lower intrinsic activity than that of Ce, they have an important effect of increasing AS to a level that pure ceria can never attain synthetically, thereby increasing their catalytic activity.
- Published
- 2019
41. Metal–Oxide Interfaces for Selective Electrochemical C–C Coupling Reactions
- Author
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Si Young Lee, Seung-Jae Shin, Hyung Suk Oh, Da Hye Won, Hyejin Jung, Byoung Koun Min, Min Gyu Kim, Yun Jeong Hwang, Woong Lee, Chan Woo Lee, Dang Le Tri Nguyen, Hyungjun Kim, and Taehwan Jang
- Subjects
Materials science ,Oxide ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Chemical interaction ,010402 general chemistry ,Electrochemistry ,01 natural sciences ,Catalysis ,Metal ,C c coupling ,chemistry.chemical_compound ,Hardware_INTEGRATEDCIRCUITS ,Materials Chemistry ,Renewable Energy, Sustainability and the Environment ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Fuel Technology ,chemistry ,Chemistry (miscellaneous) ,visual_art ,visual_art.visual_art_medium ,0210 nano-technology ,Platinum - Abstract
Metal–oxide interfaces provide a new opportunity to improve catalytic activity based on electronic and chemical interactions at the interface. Constructing a high density of interfaces is essential...
- Published
- 2019
42. Sensor-Instrumented Scaffold Integrated with Microporous Spongelike Ultrabuoy for Long-Term 3D Mapping of Cellular Behaviors and Functions
- Author
-
Min Ku Kim, Chi Hwan Lee, Hanmin Jang, Dong Rip Kim, Hyungjun Kim, and Bongjoong Kim
- Subjects
Scaffold ,Surface Properties ,Computer science ,Cell Culture Techniques ,Cellular functions ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,In vivo tests ,3d mapping ,Tissue engineering ,Long period ,Electric Impedance ,Human Umbilical Vein Endothelial Cells ,Humans ,General Materials Science ,Particle Size ,Cell Engineering ,Tissue Scaffolds ,Electric Conductivity ,General Engineering ,Hydrogen-Ion Concentration ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Oxygen ,visual_art ,Electronic component ,MCF-7 Cells ,visual_art.visual_art_medium ,0210 nano-technology ,Porosity ,Relevant information ,Biomedical engineering - Abstract
Real-time monitoring of cellular behaviors and functions with sensor-instrumented scaffolds can provide a profound impact on fundamental studies of the underlying biophysics and disease modeling. Although quantitative measurement of predictive data for in vivo tests and physiologically relevant information in these contexts is important, the long-term reliable monitoring of cellular functions in three-dimensional (3D) environments is limited by the required set under wet cell culture conditions that are unfavorable to electronic instrument settings. Here, we introduce an ultrabuoyant 3D instrumented scaffold that can remain afloat on the surface of culture medium and thereby provides favorable environments for the entire electronic components in the air while the cells reside and grow underneath. This setting enables high-fidelity recording of electrical cell-substrate impedance and electrophysiological signals for a long period of time (weeks). Comprehensive in vitro studies reveal the utility of this platform as an effective tool for drug screening and tissue development.
- Published
- 2019
43. Experimental and Density Functional Theory Corroborated Optimization of Durable Metal Embedded Carbon Nanofiber for Oxygen Electrocatalysis
- Author
-
Hyungjun Kim, Yoonhoo Ha, Jaeyoung Lee, Sinwoo Kang, and Kahyun Ham
- Subjects
Materials science ,Hydrogen ,Carbon nanofiber ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrocatalyst ,01 natural sciences ,Oxygen ,0104 chemical sciences ,Metal ,chemistry ,visual_art ,visual_art.visual_art_medium ,General Materials Science ,Density functional theory ,Physical and Theoretical Chemistry ,0210 nano-technology ,Platinum ,Realization (systems) - Abstract
There is a growing need for widespread deployment of hydrogen and fuel cell technology for the realization of a sustainable energy landscape. However, due to the high price of platinum (Pt) catalysts, it is necessary to develop highly active and stable non-Pt oxygen reduction reaction (ORR) catalysts. Here, we describe a rational design of nonnoble metal-embedding and nitrogen-containing carbon nanofiber (M-CNF) catalysts. Using a combined experimental and computational approach, we establish an ORR activity volcano of M-CNF using the work function of the embedded metal as the descriptor. Near the top of the activity volcano, the embedded metal is further optimized by tuning the Fe
- Published
- 2019
44. Light Emission Enhancement by Tuning the Structural Phase of APbBr3 (A = CH3NH3, Cs) Perovskites
- Author
-
L. Debbichi, Nam-Gyu Park, Y. Choi, Do-Kyoung Lee, Dongho Kim, and Hyungjun Kim
- Subjects
Structural phase ,Materials science ,business.industry ,Photovoltaic system ,Halide ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Active layer ,law.invention ,law ,Optoelectronics ,General Materials Science ,Light emission ,Physical and Theoretical Chemistry ,0210 nano-technology ,business ,Light-emitting diode ,Diode ,Perovskite (structure) - Abstract
Lead halide perovskite (APbX3) has recently emerged as a promising active layer in light-emitting diodes (LEDs) as well as an absorber for photovoltaic devices. For better LED properties, it is imp...
- Published
- 2019
45. Probing Surface Chemistry at an Atomic Level: Decomposition of 1-Propanethiol on GaP(001) (2 × 4) Investigated by STM, XPS, and DFT
- Author
-
Minho Kim, Peter Doak, Hyungjun Kim, Harry A. Atwater, and Seokmin Jeon
- Subjects
Propanethiol ,Thermal decomposition ,chemistry.chemical_element ,Dissociation (chemistry) ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,General Energy ,chemistry ,X-ray photoelectron spectroscopy ,law ,Physical chemistry ,Molecule ,Density functional theory ,Physical and Theoretical Chemistry ,Scanning tunneling microscope ,Gallium - Abstract
The adsorption and decomposition mechanisms for 1-propanethiol on a Ga-rich GaP(001) (2 × 4) surface are investigated at an atomic level using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy, and density functional theory (DFT) calculations. Using a combination of experimental and theoretical tools, we probe the detailed structures and energetics of a series of reaction intermediates in the thermal decomposition pathway from 130 to 773 K. At 130 K, the propanethiolate adsorbates are observed at the edge gallium sites, with the thiolate–Ga bonding configuration maintained up to 473 K. Further decomposition produces two new surface features, Ga–S–Ga and P-propyl species at 573 K. Finally, S-induced (1 × 1) and (2 × 1) reconstructions are observed at 673–773 K, which are reportedly associated with arrays of surface Ga–S–Ga bonds and subsurface diffusion of S. To understand the observed site-selectivity on the hydrogen dissociation of the thiol molecule at 130 K, the two most likely dissociation pathways (Ga–P vs Ga–Ga dimer sites) are investigated using DFT Gibbs energy calculations. While the theory predicts the kinetic advantage for the dissociation reaction occurring on the Ga–P dimer (Lewis acid–base combination), we only observed dissociation products on the Ga–Ga dimer (Lewis acid). The DFT calculations clarify that the reversible thiolate diffusion along the Ga dimer row prevents recombinative desorption, which is probable on the Ga–P dimer. Together with experimental and theoretical results, we suggest a thermal decomposition mechanism for the thiol molecule with atomic-level structural details.
- Published
- 2019
46. Antibody-Assisted Delivery of a Peptide–Drug Conjugate for Targeted Cancer Therapy
- Author
-
Sangyong Jon, Dobeen Hwang, So-Young Lee, Yonghyun Lee, Junho Chung, Sunghyun Kim, Minsuk Choi, Sukmo Kang, and Hyungjun Kim
- Subjects
Immunoconjugates ,Cancer therapy ,Mice, Nude ,Pharmaceutical Science ,Antineoplastic Agents ,02 engineering and technology ,Irinotecan ,030226 pharmacology & pharmacy ,Antibodies ,Mice ,03 medical and health sciences ,Drug Delivery Systems ,0302 clinical medicine ,In vivo ,Cell Line, Tumor ,Drug Discovery ,In Situ Nick-End Labeling ,Animals ,Humans ,Cytotoxicity ,Peptide drug conjugates ,Mice, Inbred BALB C ,biology ,Chemistry ,Assisted delivery ,hemic and immune systems ,Glioma ,021001 nanoscience & nanotechnology ,Fibronectin ,biology.protein ,Cancer research ,Molecular Medicine ,Female ,Antibody ,Peptides ,0210 nano-technology ,Conjugate - Abstract
A number of cancer-targeting peptide-drug conjugates (PDCs) have been explored as alternatives to antibody-drug conjugates (ADCs) for targeted cancer therapy. However, the much shorter circulation half-life of PDCs compared with ADCs in vivo has limited their therapeutic value and thus their translation into the clinic, highlighting the need to develop new approaches for extending the half-life of PDCs. Here, we report a new strategy for targeted cancer therapy of a PDC based on a molecular hybrid between an antihapten antibody and a hapten-labeled PDC. An anticotinine antibody (Abcot) was used as a model antihapten antibody. The anticancer drug SN38 was linked to a cotinine-labeled aptide specific to extra domain B of fibronectin (cot-APTEDB), yielding the model PDC, cot-APTEDB-SN38. The cotinine-labeled PDC showed specific binding to and cytotoxicity toward an EDB-overexpressing human glioblastoma cell line (U87MG) and also formed a hybrid complex (HC) with Abcot in situ, designated HC[cot-APTEDB-SN38/Abcot]. In glioblastoma-bearing mice, in situ HC[cot-APTEDB-SN38/Abcot] significantly extended the circulation half-life of cot-APTEDB-SN38 in blood, and it enhanced accumulation and penetration within the tumor and, ultimately, inhibition of tumor growth. These findings suggest that the present platform holds promise as a new, targeted delivery strategy for PDCs in anticancer therapy.
- Published
- 2018
47. Investigating the Optical Properties of Thiophene Additions to s-Indacene Donors with Diketopyrrolopyrrole, Isoindigo, and Thienothiophene Acceptors
- Author
-
Deqing Zhang, Bradley Keller, Angelar K. Muthike, Zhengxu Cai, Theodore Goodson, Paul M. Zimmerman, Prabhat Kumar Sahu, Audrey Eshun, and Hyungjun Kim
- Subjects
chemistry.chemical_classification ,Quantum chemical ,Chemistry ,02 engineering and technology ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Acceptor ,Fluorescence ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,Thiophene ,Steady state (chemistry) ,Physical and Theoretical Chemistry ,0210 nano-technology ,Enhanced absorption - Abstract
New donor–acceptor light harvesting polymers with either a 4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene or a 4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithienothiophene donor subunit and either a 2-(nonadecan-9-yl)-5-(2-octyldodecyl)-3,6-di(thiophen-2-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione, (E)-1,1′-bis(2-octyldodecyl)-[3,3′-biindolinylidene]-2,2′-dione, or 3-ethyl-1-(thieno[3,4-b]thiophen-2-yl)heptan-1-one acceptor were synthesized. In this study, the effects of donor conjugation length and donor-acceptor combination on the optical properties of the synthesized polymers were investigated using steady state, up-conversion, quantum chemical simulations and ultrafast and transient spectroscopic techniques. At high energies, it was observed that polymers with extended donor conjugation had significantly enhanced absorption, whereas those with stronger acceptors showed higher extinction coefficients at lower energies. Fluorescence up-convers...
- Published
- 2018
48. Effects of Ar Addition to O2 Plasma on Plasma-Enhanced Atomic Layer Deposition of Oxide Thin Films
- Author
-
Ohyung Kwon, Il Kwon Oh, Se-Hun Kwon, Woo-Jae Lee, Sanghun Lee, Woo-Hee Kim, Hyungjun Kim, Hanearl Jung, Bo Eun Park, and Chang Mo Yoon
- Subjects
010302 applied physics ,Materials science ,Oxide ,Analytical chemistry ,02 engineering and technology ,Plasma ,Electron ,Dielectric ,021001 nanoscience & nanotechnology ,01 natural sciences ,Ion ,chemistry.chemical_compound ,Atomic layer deposition ,chemistry ,0103 physical sciences ,General Materials Science ,Thin film ,0210 nano-technology ,Saturation (magnetic) - Abstract
A method for significantly increasing the growth rates (GRs) of high- k oxide thin films grown via plasma-enhanced atomic layer deposition (PE-ALD) by enhancing the plasma density through the addition of Ar gas to the O2 plasma oxidant was developed. This approach led to improvements of ∼60% in the saturation GRs of PE-ALD ZrO2, HfO2, and SiO2. Furthermore, despite the significantly higher GR enabled by PE-ALD, the mechanical and dielectric properties of the PE-ALD oxide films were similar or even superior to those of films grown via the conventional O2 plasma process. Optical emission spectroscopy analyses in conjunction with theoretical calculation of the electron energy distribution function revealed that adding Ar gas to the O2 plasma increased the density of high-energy electrons, thereby generating more O2 plasma species, such as ions and radicals, which played a key role in improving the GRs and the properties of the films. This promising approach is expected to facilitate the high-volume manufacturing of films via PE-ALD, especially for use as gate insulators in thin-film transistor-based devices in the display industry.
- Published
- 2018
49. Roles of SnX2 (X = F, Cl, Br) Additives in Tin-Based Halide Perovskites toward Highly Efficient and Stable Lead-Free Perovskite Solar Cells
- Author
-
Sang Hwa Moon, Jongseob Kim, Hyungjun Kim, Ki-Ha Hong, Sang Hyuk Im, and Jin Hyuck Heo
- Subjects
Materials science ,Passivation ,Energy conversion efficiency ,Photovoltaic system ,chemistry.chemical_element ,Halide ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry ,Chemical engineering ,Phase (matter) ,General Materials Science ,Physical and Theoretical Chemistry ,0210 nano-technology ,Tin ,Performance enhancement ,Perovskite (structure) - Abstract
Preserving the stability of Sn-based halide perovskites is a primary concern in developing photovoltaic light-absorbing materials for lead-free perovskite solar cells. Whereas the addition of SnX2 (X = F, Cl, Br) has been demonstrated to improve the photovoltaic performance of Sn halide perovskite solar cells, the mechanistic roles of SnX2 in the performance enhancement have not yet been studied appropriately. Here we perform a comparative study of CsSnI3 films and devices and examine how SnX2 additives affect their stability, and the results are corroborated by first-principles-based theoretical calculations. Unlike the conventional belief that the additives annihilate defects, we find that the additives effectively passivate the surface and stabilize the perovskite phase, promoting the stability of CsSnI3. Our mechanism suggests that SnBr2, which shows ca. 100 h of prolonged stability along with a high power conversion efficiency of 4.3%, is the best additive for enhancing the stability of CsSnI3.
- Published
- 2018
50. High-Performance Gas Sensor Using a Large-Area WS2xSe2–2x Alloy for Low-Power Operation Wearable Applications
- Author
-
Jeong Gyu Song, Kyunam Park, Jusang Park, Kyung Yong Ko, Whang Je Woo, Sangyoon Lee, Zonghoon Lee, Dong-Hyun Kim, Hyungjun Kim, Jung Hwa Kim, and Youngjun Kim
- Subjects
Materials science ,business.industry ,Alloy ,Wearable computer ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Power (physics) ,engineering ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business - Abstract
Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have attracted considerable attention as promising building blocks for a new generation of gas-sensing devices because of their excellent electrical properties, superior response, flexibility, and low-power consumption. Owing to their large surface-to-volume ratio, various 2D TMDCs, such as MoS2, MoSe2, WS2, and WSe2, have exhibited excellent gas-sensing characteristics. However, exploration toward the enhancement of TMDC gas-sensing performance has not yet been intensively addressed. Here, we synthesized large-area uniform WS2 xSe2-2 x alloys for room-temperature gas sensors. As-synthesized WS2 xSe2-2 x alloys exhibit an elaborative composition control owing to their thermodynamically stable sulfurization process. Further, utilizing uniform WS2 xSe2-2 x alloys over a large area, we demonstrated improved NO2-sensing performance compared to WSe2 on the basis of an electronic sensitization mechanism. The WS0.96Se1.04 alloy gas sensor exhibits 2.4 times enhanced response for NO2 exposure. Further, we demonstrated a low-power wearable NO2-detecting wristband that operates at room temperature. Our results show that the proposed method is a promising strategy to improve 2D TMDC gas sensors and has a potential for applications in advanced gas-sensing devices.
- Published
- 2018
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