• 한국진공학회지
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• 제15권2호
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• pp.139-144
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• 2006

Scanning tunneling microscopy (STM)를 이용하여 Si(111)$4{\times}1$-In 표면에의 수소원자 흡착의 영향을 고찰하였다. STM 이미지에서 수소원자는 $4{\times}1$-In chain의 한 쪽 줄에 있는 두개의 연속된 밝은 부분 사이에 위치한다. 이 H 원자는 두 줄의 zigzag subchain 중의 한 쪽에만 선택적으로 흡착되는 경향성을 보이며 이는 수소원자의 흡착에 표면 밑의 구조가 영향을 미침을 시사한다. 표면에 흡착된 수소원자는 흡착위치 주위의 국소적 변형 뿐 만 아니라 chain 방향으로 멀리 떨어진 곳에도 영향을 미쳐서 STM 이미지에 두 배 주기의 modulation이 나타나게 한다. 수소흡착에 의해 유도되는 두 배 주기의 modulation은 기존에 보고된 Na 원자 흡착에 의해 유도되는 상과 다름을 확인하였다.

• 전기화학회지
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• 제10권2호
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• pp.73-81
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• 2007

This review article considered the electrochemical reduction of uranyl ions on a Pt surface. Specifically, we focussed on the improvement in its reduction current efficiency. First, this article briefly explained the fundamentals of the reduction of uranyl ($UO_2^{2+}$) ions on a Pt surface. Namely, they involved the electrochemical behaviour of uranium species, and electrochemical cell configurations for the reduction of $UO_2^{2+}$ ions. In addition, the effects of adsorbed hydrogen atoms were investigated on the reduction of $UO_2^{2+}$ ions. Finally, this article presented the methods for improving current efficiency of the reduction of $UO_2^{2+}$ ions on a Pt surface. Three different kinds of methods are introduced, which include electrochemical surface treatments of Pt electrode involving hydrogenation and anodisation, the use of catalyst poisons, and formation of thin mercury film on a Pt electrode. Moreover, this article provided some clues about how hydrogenation and catalyst poisons work on the reduction of $UO_2^{2+}$ ions.

• 대한화학회지
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• 제14권3호
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• pp.213-219
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• 1970

In the presence of hydrogen peroxide, the effects of temperature and pH to the catalytic reaction velocity of cupric -thiocyanate and the quantities of reduction products adsorbed on the D.M.E. have been studied by polarographic method. According to these experiments, the following empirical equation has been derived for the relation among temperature $T_i$, concentration of hydrogen ion $pH_i$ and adsorbed cuprous-thiocyanate in moles/$cm^2Z_{ij}$, and rate constant log$K_{ij}$ $$log\;K_{ij}=\frac{1}{T_i}\{A(pH_j)+B\}+C(pH_j)+D$$ $$Z_{ij}=\frac{1}{T_i}\{{\alpha}(pH_j)^{\frac{1}{2}}+{\beta}\}+{\gamma}(pH_j)^{\frac{1}{2}}+{\delta}$$ where, A,B,C,D and {$\alpha},{\beta},{\gamma},{\delta}$ are constants. The Calculated values by both equations are well agreed with empirical values within 8% in the error.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.25-25
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• 2000

In this talk we discuss the dynamics of hydrogen on the Si(100)-2xl surface. At room temperature the sticking coefficient for molecular hydrogen on this surface is less than 10sup-12. However, hydrogen molecules desorbing from the surface do not have an excess of energy, suggesting at best a small barrier on the exit channel. These observations have led to speculation about the validity of detailed balance in this system. Here we show that this discrepancy can be explained by considering both the surface-molecule co-ordinate and that associated with the Si-Si dimer bond tiltangle. By preparing the surface dimers with a specific tiltangle we demonstrate that the barrier to adsorption is a function of this angle and that the sticking coefficient dramatically increase for certain angles. The adsorption-desopption dynamics can then be described in terms of a common potential energy hypersurface involving both of these co-ordinates. The implications of these observations are also discussed. The dynamics of adsorbed hydrogen atoms on the Si(100) surface is also described. Paired dangling bonds produced following recombinative hydrogen desorption are mobile at elevated temperatures. Pairs of dangling bonds are observed to dissociate, diffuse, and ultimately recombine. At sufficiently elevated temperatures dangling bond exchange reactions are observed. These data are analyzed in terms of an attractive zone and an effective binding interaction between dangling bonds. Insights that this provides into the nature of surface defects and the localized chemistry that occurs on this surface, are also discussed.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.214-214
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• 2011

The adsorption and reactions of methanol and methyl iodide on ZnO(0001) and ZnO(11-20) single crystal surfaces have been investigated using the temperature programmed desorption (TPD) technique. The interaction of methanol and methyl iodide with ZnO is stronger on the polar ZnO(0001) surface than the non-polar ZnO(11-20) surface. On ZnO(0001), methanol is decomposed to produce formaldehyde and hydrogen. Two desorption features of formaldehyde and hydrogen are observed at around 500 and 580 K. The interaction of methanol and pre-adsorbed hydrogen has been also investigated. The reaction mechanism of methanol on ZnO will be proposed.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2004년도 수소연료전지공동심포지움 2004논문집
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• pp.287-292
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• 2004

In order to understand the relationship between molecular structure of Metal-Organic Framework(MOF) and capacity of hydrogen absorption, quantum mechanical calculations and grand canonical Monte Carlo simulations have been carried out on a series of MOF-5 having various organic linkers. The calculation results about specific surface area and electron density for various frameworks indicated that the capacity of the hydrogen storage is largely dependent on effective surface area rather than the free volume. Based on the iso-electrostatic potential surface from density functional calculation and the amount of adsorbed hydrogens from grand canonical Monte Carlo calculation, it was also found that the electron localization ground organic linker plays an important role in hydrogen capacity of MOFs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.151-151
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• 2000

We have studied the atomic structure of Si(100)-c(4$\times$4) reconstruction using scanning tunneling microscopy(STM). The c(4$\times$4) reconstruction can be formed by annealing the hydrogen exposured surface at temperatures between 850 and 960 K. At this temperature ranges, adsorbed hydrogen atoms are all desorbed. Therefore, the c(4$\times$4) reconstruction is due to the Si dimers on surface. The filled and empty state images of the STM were interpreted in terms of Si dimers in c(4$\times$4) primitive cell forming the reconstruction. Based on the STM images and hydrogen adsorption experiment on c(4$\times$40 surface, we suggest that Si dimers in c(4$\times$40 unit cell are perpendicular ad-dimer to the underlying Si dimer rows.

• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1543-1550
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• 2010

This work presents oxidation of formic acid on Bi-modified Pt nanoparticles of various sizes. The sizes of the studied Pt nanoparticles range from 1.5 to 5.6 nm (detailed in Rhee, C. K.; Kim, B.-J.; Ham, C.; Kim, Y.-J.; Song, K.; Kwon, K. Langmuir 2009, 25, 7140-7147), and the surfaces of the Pt nanoparticles are modified with irreversibly adsorbed Bi. The investigated coverages of Bi on the Pt nanoparticles are 0.12 and 0.25 as determined by coulometry of the oxidation of adsorbed hydrogen and Bi, and X-ray photoelectron spectroscopy. The cyclic voltammetric behavior of formic acid oxidation reveals that the adsorbed Bi enhances the catalytic activity of Pt nanoparticles by impeding a poison-forming dehydration path with a concomitant promotion of a dehydrogenation path. The chronoamperometric results indicate that elemental Bi and partially oxidized Bi are responsible for the catalytic enhancement, when the Bi coverages on Pt nanoparticles are 0.12 and 0.25, respectively. The size effect of Bi-modified Pt nanoparticles in formic acid oxidation is discussed in terms of specific activity (current per unit surface area) and mass activity (current per unit mass).

• 한국수산과학회지
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• 제43권5호
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• pp.400-405
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• 2010

This study investigated lead adsorption by carboxylated alginic acid and its application in cleansing cosmetics. Carboxylated alginic acid showed the highest lead adsorptivity after oxidation in a 4-6 mM hydrogen peroxide solution at $20-30^{\circ}C$ for 30-40 min. Carboxylated alginic acid adsorbed $648.1{\pm}2.8-653.0{\pm}2.9$ mg/g of lead dry mass at pH 4-6. Carboxylated alginic acid modified by hydrogen peroxide and potassium permanganate adsorbed $651.3{\pm}3.8$ and $639.9{\pm}4.0$ mg/g of lead dry mass, respectively. Carboxylated alginic acid showed higher lead adsorptivity after modification by hydrogen peroxide than by potassium permanganate, with an increase of ~30% compared with raw alginic acid. To access the potential application of carboxylated alginic acid in cleansing cosmetics, we investigated the lead adsorptivity, conditions of the cosmetics procedure, and cytotoxicity of various concentrations of cleansing cosmetics added to 5% carboxylated alginic acid. The ideal cosmetic concentrations combined with 5% carboxylated alginic acid were 70% for peeling gel, 20% for massage cream, 20% for foam cleansing and 40% for cleansing cream. There was no cytotoxicity in cleansing cosmetics combined with 5% carboxylated alginic acid.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.125.2-125.2
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• 2016

Semiconductor nanowires are essential building blocks for various nanotechnologies including energy conversion, optoelectronics, and thermoelectric devices. Bottom-up synthetic approach utilizing metal catalyst and vapor phase precursor molecules (i.e., vapor - liquid - solid (VLS) method) is widely employed to grow semiconductor nanowires. Al has received attention as growth catalyst since it is free from contamination issue of Si nanowire leading to the deterioration of electrical properties. Al-catalyzed Si nanowire growth, however, unlike Au-Si system, has relatively narrow window for stable growth, showing highly tapered sidewall structure at high temperature condition. Although surface chemistry is generally known for its role on the crystal growth, it is still unclear how surface adsorbates such as hydrogen atoms and the nanowire sidewall morphology interrelate in VLS growth. Here, we use real-time in situ infrared spectroscopy to confirm the presence of surface hydrogen atoms chemisorbed on Si nanowire sidewalls grown from Al catalyst and demonstrate they are necessary to prevent unwanted tapering of nanowire. We analyze the surface coverage of hydrogen atoms quantitatively via comparison of Si-H vibration modes measured during growth with those obtained from postgrowth measurement. Our findings suggest that the surface adsorbed hydrogen plays a critical role in preventing nanowire sidewall tapering and provide new insights for the role of surface chemistry in VLS growth.