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Han, Dandan,Park, Changhoon,Oh, Seonghyeon,Jung, Howon,Hahn, Jae W. De Gruyter 2019 Nanophotonics Vol.8 No.5
<P><B>Abstract</B></P><P>Quantitative analysis of line edge roughness (LER) is very important for understanding the root causes of LER and thereby improving the pattern quality in near-field lithography (NFL), because LER has become the main limiter of critical dimension (CD) control as the feature size of nanostructures is scaled down. To address this challenge, the photoresist point-spread function of NFL with a contact plasmonic ridge nanoaperture can be employed to account for the physical and chemical effects involved in the LER-generation mechanism. Our theoretical and experimental results show that the sources of LER in NFL mainly come from the aerial image, material chemistry, and process. Importantly, the complicated decay characteristics of surface plasmon waves are demonstrated to be the main optical contributor. Because the evanescent mode of surface plasmon polaritons (SPPs) and quasi-spherical waves (QSWs) decay in the lateral direction, they can induce a small image log-slope and low photoresist contrast, leading to a large LER. We introduce an analytical model and demonstrate the relationship between LER and CD to estimate the pattern quality in NFL. We expect that these results can provide alternative approaches to further improve pattern uniformity and resolution, which can lead to advanced nanopatterning results in NFL.</P>
Han, Dandan,Zhu, Tao,Row, Kyung-Ho Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.7
An ionic liquid-based ultrasonic-assisted extraction method has been successfully applied to the effective extraction of phenolic compounds from Laminaria japonica Aresch. Three kinds of 1-alkyl-3-methyl-imidazolium with different cations and anions were evaluated for extraction efficiency. The results showed that both the characteristics of anions and cations have remarkable effects on the extraction efficiency. In addition, the ionic liquid-based ultrasonic-assisted extraction procedure was also optimized on some extraction parameters, such as ultrasonic power, extraction time and solid-liquid ratio. Compared with the conventional solvent, the optimum approach gained the highest extraction efficiency within the shortest extraction time. Average recoveries of phenolic compounds were from 75.5% to 88.3% at three concentration levels.
Dandan Han,Tao Zhu,노경호 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.7
An ionic liquid-based ultrasonic-assisted extraction method has been successfully applied to the effective extraction of phenolic compounds from Laminaria japonica Aresch. Three kinds of 1-alkyl-3-methylimidazolium with different cations and anions were evaluated for extraction efficiency. The results showed that both the characteristics of anions and cations have remarkable effects on the extraction efficiency. In addition,the ionic liquid-based ultrasonic-assisted extraction procedure was also optimized on some extraction parameters, such as ultrasonic power, extraction time and solid-liquid ratio. Compared with the conventional solvent, the optimum approach gained the highest extraction efficiency within the shortest extraction time. Average recoveries of phenolic compounds were from 75.5% to 88.3% at three concentration levels.
Dandan Han,Dong Wha Park,최대기,Minglei Tian,노경호 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.5
Ionic liquids (ILs) have gained wide recognition as novel solvents in chemistry. Their application in analytical chemistry, especially in separating analytes, is warranted due to their unique properties such as negligible vapor pressure, good thermal stability, tunable viscosity and miscibility with water and organic solvents, as well as good extractability for various organic compounds and metal ions. Recently, some new chromatographic separation media, formed by combining ILs on silica and polymer surface using covalently or non-covalently interaction, have been developed and applied to biological separation and environment analysis. This review will focus on some of the properties of ILs and their potential application as mobile phase modifier and surface-bonded stationary phase in high-performance liquid chromatography (HPLC) separation.
Han, Dandan,Tian, Minglei,Park, Dong Wha,Row, Kyung Ho Natural Product Communications 2013 Natural product communications Vol.8 No.2
<P>A solid-phase extraction (SPE) method for the determination of procatechuic acid, ferulic acid and caffeic acid in Salicornia herbacea L. (Hamcho) has been developed. The optimal conditions were obtained by using a C18 SPE cartridge. By using ethanol and acetonitrile /water/ trifluoracetic acid as washing and eluting solvents, most interfering compounds originating from the hamcho matrix were eliminated. The extracts were sufficiently clean to be directly injected into the HPLC for further chromatographic analysis. Good linearity was obtained from 0.1 to 200 microg/mL (r > 0.999) for procatechuic acid, 0.2 to 400 microg/mL (r > 0.999) for caffeic acid and 0.3 to 600 microg/mL (r > 0.999) for ferulic acid, with the relative standard deviations being less than 3.6%. The mean recoveries of procatechuic acid, ferulic acid and caffeic acid from hamcho were more than 79.2% and the detection limit (S/N = 3:1) was 0.02 microg/mL for procatechuic acid, 0.01 microg/mL for caffeic acid and 0.04 microg/mL for ferulic acid. This method is a viable alternative to the existing HPLC methods for analyzing the content of procatechuic acid, ferulic acid and caffeic acid in hamcho.</P>
Ye Wang,Dandan Han,Minglei Tian,노경호 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.3
Linear solvation energy relationships (LSERs) are used to investigate the fundamental chemical interactions governing the retention of nine aromatic compounds on a C18 column. The mobile phases studied involve ionic liquids 1-Methyl-3-octylimidazolium tetrafluoroborate ([OMIm][BF4]) (0.003-0.009M), with 5 to 20% acetonitrile in water as mobile phase modifiers. The ability of the LSERs to account for the chemical interactions underlying solute retention is shown. A comparison of predicted and experimental retention factors suggests that LSER formalism is able to reproduce adequately the experimental retention factors of the solutes studied in the different experimental conditions investigated.
Xin Zhao,Dandan Ke,Shumin Han,Yuan Li,Hongming Zhang,Ying Cai 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.11
By adding surfactant polyvinyl alcohol (PVA) and controlling the preparation process, we successfully synthesized Co–Mo catalysts. For further improving the dispersion, reduced graphene oxide sheets as catalyst carrier were introduced to synthesize Co–Mo@rGO composite catalyst as highly efficient catalysts for hydrolytic dehydrogenation of ammonia borane. The introduction of Mo for preparing Co–Mo@rGO catalyst helped to form alloy catalyst with better structure, better dispersity and smaller particle size. When the molar ratio of Co and Mo was 0.75 : 0.25, the bimetallic composite catalyst exhibited superior activity with TOF value of 16.29 mol H2 · min -1 · mol Co-Mo -1. The activation energy of the reaction was calculated to be 43.72 kJ · mol -1. Furthermore, the reusability tests reveal that waxberry-like Co–Mo still show good catalytic activity with 80.3 % of their initial activity in five successive runs. The enhanced catalytic activities were due to the synergistic interaction between graphene sheets and waxberry-like Co–Mo NPs, which was beneficial to improve the dispersion and stability of bimetallic NPs. Also, ligand effects on the formation of waxberry-like structure and amorphous state further promoted the catalytic activity.
Oh, Seonghyeon,Han, Dandan,Shim, Hyeon Bo,Hahn, Jae W IOP 2018 Nanotechnology Vol.29 No.4
<P>Subwavelength features have been successfully demonstrated in near-field lithography. In this study, the point spread function (PSF) of a near-field beam spot from a plasmonic ridge nanoaperture is discussed with regard to the complex decaying characteristic of a non-propagating wave and the asymmetry of the field distribution for pattern design. We relaxed the shape complexity of the field distribution with pixel-based optical proximity correction (OPC) for simplifying the pattern image distortion. To enhance the pattern fidelity for a variety of arbitrary patterns, field-sectioning structures are formulated via convolutions with a time-modulation function and a transient PSF along the near-field dominant direction. The sharpness of corners and edges, and line shortening can be improved by modifying the original target pattern shape using the proposed approach by considering both the pattern geometry and directionality of the field decay for OPC in near-field lithography.</P>