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RISS 인기검색어
- 검색키워드
- 저자 : Lee Hangil (검색결과 97 건)
- 무료
- 기관 내 무료
- 유료
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Electronic Structure and Bonding Configuration of Histidine on Ge(100)
Hangil Lee,윤영상,Sena Yang,Soon Jung Jung,김세훈 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.11
The electronic structures and bonding configuration of histidine on Ge(100) have been investigated with various sample treatments using core-level photoemission spectroscopy (CLPES). Interpretation of the Ge 3d, C 1s, N 1s, and O 1s core level spectra being included in these systems revealed that both the imino nitrogen in the imidazole ring and the carboxyl group in the glycine moiety concurrently participate in the adsorption of histidine on a Ge(100) surface at 380 K. Moreover, we could clearly confirm that the imino nitrogen with a free lone pair in the imidazole group adsorbs on Ge(100) more strongly than the carboxyl group in the glycine moiety by examining systems annealed at various temperatures.
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Comparison of the Catalytic Oxidation Reaction on Graphene Oxide and Reduced Graphene Oxide
Lee, Myungjin,Yang, Sena,Kim, Ki-jeong,Kim, Sehun,Lee, Hangil American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.2
<P>The capacities of graphene oxide (GO) and reduced graphene oxide (rGO) films grown on silicon substrate to cause the aniline to azobenzene oxidation reaction were compared by using Raman spectroscopy, high-resolution photoemission spectroscopy (HRPES), and work function measurements as well as scanning electron microscopy (SEM). The oxygen carriers’ existence on GO film, which includes a lot of oxygen carriers, can facilitate the aniline to azobenzene oxidation reaction with slightly partial conversion of aniline to nitrobenzene, as determined by the Raman shifts and core-level spectra resulting from exposure to aniline. The work function of the GO film was found to change dramatically in comparison with rGO film, indicating that aniline exposed to a GO film produced n-type doping characteristics by electron charge transfer from GO to aniline. These results indicate that the oxygen carriers on a GO film oxidize aniline to azobenzene and show that GO film prefers to act as a reaction reagent rather than rGO.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-2/jp411682b/production/images/medium/jp-2013-11682b_0008.gif'></P>
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Inter-row Adsorption Configuration and Stability of Threonine Adsorbed on the Ge(100) Surfaces
Lee, Myungjin,Park, Youngchan,Jeong, Hyuk,Lee, Hangil Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.4
The adsorption structures of threonine on the Ge(100) surface were investigated using core-level photoemission spectroscopy (CLPES) in conjunction with density functional theory (DFT) calculations. CLPES measurements were performed to identify the experimentally preferred adsorption structure. The preferred structure indicated the relative reactivities of the carboxyl and hydroxymethyl groups as electron donors to the Ge(100) surface during adsorption. The core-level C 1s, N 1s, and O 1s CLPES spectra indicated that the carboxyl oxygen competed more strongly with the hydroxymethyl oxygen during the adsorption reaction. Three among six possible adsorption structures were identified as energetically favorable using DFT calculation methods that considered the inter- and intra-bonding configurations upon adsorption onto the Ge(100) surface. These structures were O-H dissociated N dative inter bonding, O-H dissociated N dative intra bonding, O-H dissociation bonding. One of the adsorption structures: O-H dissociated N dative inter bonding was predicted to be stable in light of the transition state energies. We thus confirmed that the most favorable adsorption structure is the O-H dissociated N dative-inter bonding structure using CLPES and DFT calculation.
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The Study of Adsorption Structures of 3-Methyl-5-Pyrazolone on the Ge(100) Surface
Lee, Myungjin,Lee, Hangil Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.12
The most stable adsorption structures and energies of four tautomers of 3-methyl-5-pyrazolone (keto-1, enol-1, keto-2, and enol-2) on Ge(100) surfaces were investigated using density functional theory (DFT) calculations. The enol-1, keto-2, and enol-2 tautomers, but not the keto-1 tautomer, were found to exhibit stable adsorption structures on the Ge(100)-$2{\times}1$ surface. Of these three adsorption structures, that of enol-2 is the most stable.
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Lee, Myungjin,Kim, Kijeong,Lee, Hangil Springer 2013 NANOSCALE RESEARCH LETTERS Vol.8 No.1
<P>The oxidation of aniline to azobenzene was conducted in the presence of either monolayer graphene (EG) or graphene-oxide-like surface, such as GOx, under ultra-high vacuum conditions maintaining a 365-nm UV light exposure to enhance the oxidation reaction. The surface-bound products were investigated using micro Raman spectroscopy, high-resolution photoemission spectroscopy, and work function measurements. The oxygen carriers present on the GOx surfaces, but not on the EG surfaces, acted as reaction reagents to facilitate the oxidation reaction from aniline to azobenzene. Increasing the aniline concentration at 300 K confirmed that the exchange ratio from the aniline to the azobenzene was enhanced, as determined by the intensity ratio between the aniline- and azobenzene-induced N 1 <I>s</I> core-level spectra. The work function changed dramatically as the aniline concentration increased, indicating that the aniline on the GOx surface conveyed <I>n</I>-type doping characteristics at a low coverage level. A higher aniline concentration increased the <I>p</I>-type doping character by increasing the azobenzene concentration on the GOx surface. A comparison of the oxidation reactivity of aniline molecules on the EG or GOx surfaces revealed the role of the oxygen carriers on the GOx surfaces in the context of catalytic oxidation.</P>
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Photo-oxidation activities on Pd-doped TiO<sub>2</sub> nanoparticles: critical PdO formation effect
Lee, Hangil,Shin, Minjeong,Lee, Myungjin,Hwang, Yun Jeong Elsevier 2015 Applied Catalysis B Vol.165 No.-
<P><B>Abstract</B></P> <P>The catalytic activities of three distinct Pd-doped TiO<SUB>2</SUB> (PdTiO<SUB>2</SUB>) nanoparticle samples, post-annealed (at 700, 800, and 900°C) after fabrication on silicon substrates, were analyzed with respect to the photo-oxidation of aniline and 2-thiophenecarboxaldehyde. Through a combination of Raman spectroscopy and high-resolution photoemission spectroscopy (HRPES), we demonstrated that the photocatalytic oxidation occurred only when the PdTiO<SUB>2</SUB> nanoparticles were annealed at temperatures above 800°C, that is, when PdO and Ti<SUP>3+</SUP> had partially formed on the PdTiO<SUB>2</SUB> nanoparticles, which indicates that the presence of PdO and Ti<SUP>3+</SUP> is critical for the photocatalytic oxidation. Additionally, we determined the decrease in the band gaps to visible region with PdTiO<SUB>2</SUB> nanoparticles annealed above 800°C from their valence-band spectra, which resulted in photocatalytic activities even under visible light, <I>λ</I> =540nm.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Enhanced photocatalytic oxidation activity of PdTiO<SUB>2</SUB> nanoparticles with existence of PdO. </LI> <LI> PdO formation in PdTiO<SUB>2</SUB> nanoparticles by thermal annealing above 800°C. </LI> <LI> Capability for photo-oxidation of aniline and 2-thiophenecarboxaldehyde under visible light. </LI> <LI> Decrease of PdTiO<SUB>2</SUB> band gap to visible region (1.92eV) by thermal annealing at 900°C. </LI> </UL> </P>
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