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338 results on '"Lee, Kang ‐ Bong"'

24. Quantitative Detection of Thitsiol and Urushiol as Markers from the Gluta usitata Lacquer Tree Using HPLC.

Author

Lee, Youngseo, Lee, Jihye, Lee, Kang-Bong, Lee, Won-Yong, and Lee, Yeonhee

Subjects
LACQUER & lacquering, HIGH performance liquid chromatography, CASHEW nuts, CATECHOL
Abstract

Lacquer sap has been traditionally used in coatings and artwork. Suitable types of lacquer are required to preserve and restore artifacts. Recently, unsuitable cashew nut shell liquid (CNSL) has often been mixed with lacquer sap, so it is necessary to identify the characteristics of lacquer sap by the production area. However, research is still focused on urushiol and laccol. In this study, Myanmarese lacquer sap collected from Gluta usitata, which contains thitsiol as the main component, was analyzed by HPLC to quantify thitsiol using the standards 3-(10-phenyldecyl) benzene-1,2-diol (thitsiol 16) and 3-(8Z,11Z-pentadecadienyl)-benzenediol (urushiol 15:2) as markers, and calibration curves were plotted. The coefficients of determination (R2) for thitsiol 16 and urushiol 15:2 were 0.9985 and 0.9983, respectively. In addition, a blind test was conducted to confirm that accurate quantitative analysis was possible even when Myanmarese lacquer was mixed with lacquer from another production area, which contained urushiol as the main component, and CNSL, which contained cardol, a completely different catechol. Quantitative analysis of thitsiol 16 and urushiol 15:2 in Myanmarese lacquer using HPLC can be used to evaluate the quality of lacquer sap and for more sophisticated activities such as restoration by classifying differences in lacquer sap by the production area. [ABSTRACT FROM AUTHOR]

Published
2024
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30. High-sensitivity NH3 gas sensor using pristine graphene doped with CuO nanoparticles.

Author

Tsymbalenko, Oleksandr, Lee, Soyoung, Lee, Yong-Min, Nam, Yun-Sik, Kim, Byoung Chan, Kim, Jin Young, and Lee, Kang-Bong

Subjects
GAS detectors, SURFACE plasmon resonance, GRAPHENE, COPPER oxide, CHARGE carriers, CHEMICAL vapor deposition, NANOPARTICLES
Abstract

A highly sensitive and selective NH3 gas sensor was developed based on single-layer pristine graphene doped with copper(II) oxide (CuO) nanoparticles of a specific size. High-quality single-layer graphene was grown using chemical vapor deposition. Approximately 15 nm-sized CuO colloidal nanoparticles were fabricated by a microwave-assisted thermal method using copper acetate as the precursor, and dimethylformamide as the reducing and stabilizing agent. Pristine graphene was doped with an aqueous suspension of CuO nanoparticles at a coating speed of 1500 rpm using a simple spin coater. CuO nanoparticle doping induces changes in the electronic properties of graphene; in particular, p-type doping significantly altered graphene resistivity in the presence of NH3 gas. Upon exposure of the pristine graphene surface to NH3 gas, NH3 reacted with O2−/ O−/ O2− species on the graphene surface and released electrons into graphene. This caused a change in the concentration of charge carriers in the valence channel of graphene and an increase in graphene resistivity, facilitating real-time NH3 monitoring with quick response and rapid recovery at 25 ℃ and ~ 55% relative humidity. Our results indicated that graphene doped with ~ 15 nm-sized CuO nanoparticles can sense NH3 gas selectively with a resistivity response of ~ 83%. Moreover, the sensor exhibited good reusability, fast response (~ 19 s), and rapid recovery (~ 277 s) with a detection limit of 0.041 ppm and a relative standard deviation of 0.76%. [ABSTRACT FROM AUTHOR]

Published
2023
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48. Quantitative Analysis and Band Gap Determination for CIGS Absorber Layers Using Surface Techniques

Author

Donghwan Kim, Yeonhee Lee, Jihye Lee, Lee Kang Bong, and Yun Jung Jang

Subjects
Materials science, Article Subject, Band gap, General Chemical Engineering, lcsh:Analytical chemistry, Analytical chemistry, 02 engineering and technology, 01 natural sciences, Analytical Chemistry, law.invention, law, 0103 physical sciences, Solar cell, Thin film, Instrumentation, Inductively coupled plasma mass spectrometry, 010302 applied physics, Auger electron spectroscopy, lcsh:QD71-142, 021001 nanoscience & nanotechnology, Copper indium gallium selenide solar cells, Computer Science Applications, Secondary ion mass spectrometry, Inductively coupled plasma atomic emission spectroscopy, 0210 nano-technology, Research Article
Abstract

Recently, Cu(InXGa(1−X))Se2 (CIGS) absorber layers have been extensively studied by many research groups for thin-film solar cell technology. CIGS material is particularly promising due to its exceptionally high absorption coefficient and large band gap range, which is adjustable as a function of alloy stoichiometry. To enhance the conversion performance of CIGS solar cells, understanding the CIGS structure and composition is a crucial challenge. We conducted a quantitative study to determine the bulk composition of the major elements such as Cu, In, Ga, and Se of four different CIGS photovoltaic cells. The compositional information was obtained by X-ray fluorescence (XRF), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and femtosecond laser ablation inductively coupled plasma mass spectrometry (fs-LA-ICP-MS). Then, the XRF concentration ratio was compared with the intensity ratio of fs-LA-ICP-MS to investigate the potential of accurate and rapid analysis using the fs-LA-ICP-MS technique. In contrast to the bulk information, the surface techniques can supply detailed information about the chemical composition across the depth profile. Here, elemental depth distributions of CIGS thin films were investigated using magnetic sector secondary ion mass spectrometry (SIMS) and Auger electron spectroscopy (AES). The atomic distributions of four different CIGS absorber layers exhibited a good agreement although they were obtained using two different surface instruments, AES and SIMS. Comparative analysis results of different CIGS absorber layers using SIMS, AES, and fs-LA-ICP-MS provide us with the appropriate technique for the information of accurate composition in a rapid analysis time. Thanks to a simple approach using the Ga/(In + Ga) ratio, the optical band gap energy of the Cu(InXGa(1−X))Se2 quaternary layer was monitored in the entire CIGS layer. The elemental distribution and the band gap determination were then used to elucidate their relationship to the corresponding CIGS cell efficiency result.

Published
2018

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