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Kim Jun Hyeong,Kim Hyeonsu,Kim Woo Youn 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.5
Deep learning (DL) can be a useful approach to molecular applications such as the organic light-emitting diode (OLED) development via high-throughput virtual screening. Various representations have been proposed to incorporate molecular structures in DL methods. However, it is yet to be clear which one would be better for accurate prediction of molecular electronic properties. Here, we carried out a comparative study on the performance of four widely used molecular representations to elucidate an optimal solution for DL applications to OLED materials. We implemented six DL models based on the four representations and assessed their accuracies in the prediction of the electronic properties of thermally activated delayed fluorescence (TADF) molecules. The attention gated graph neural network based on molecular graphs showed the highest accuracy for test sets and TADF candidates. Therefore, the molecular graph can be used as an optimal representation to predict the TADF-related molecular properties.
Comparative compressional behavior of Zeolite-W with different extra-framework cations
Hyeonsu Kim,Pyosang Kim,Donghoon Seoung,Yongmoon Lee 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10
Zeolite, one of microporous materials, has been widely studied for industrial application such as catalysts or adsorbent due to its size- and shape-selective property. Many experiments of zeolites have addressed the physio-chemical properties in ambient and non-ambient condition. High-pressure researches have been carried out in the last decades and shedded a new sights into phase stability and elastic behavior in response to adopting pressure and pressure-transmitting media (PTM). Zeolite-W is one of small pore zeolites and synthetic phase which has same framework with natural zeolite, Merlinoite (MER, (K,Na)5Ca,Ba)₂Al9Si23O64·23H₂O). We have prepared several extra-framework cation, EFC, analogues (K<SUP>+</SUP>: K-MER, Na<SUP>+</SUP>: Na-MER, Ag<SUP>+</SUP>: Ag-MER, NH₄<SUP>+</SUP>: NH₄-MER) of Zeolite-W by synthesis and cation-exchange method. Chemical composition of prepared samples was confirmed from Energy dispersive X-ray spectroscopy and Thermal Gravimetric Analysis. Compressional behavior of monovalent cation forms up to 5.22 GPa at room temperature is investigated by synchrotron X ray powder diffraction at 3D and 5A beamlines. We use a diamond-anvil cell as a pressurizing tool and water as PTM. In all cases, unit cell constants slightly increase in wet condition and then gradually decrease by pressure without phase transition. Calculated bulk modulus is 37(3) GPa, 38(4) GPa, 49(2) GPa, 47(3) GPa in order of Na-MER, Ag-MER, K-MER, NH4-MER, and it reveals that (in)compressibility is related to extra-framework cation size. Further understanding in atomic scale, Rietveld refinement is ongoing.
전기화학적 특성 개선을 위해 Pt 나노구조를 가지는 미세전극 제작
우현수(Hyeonsu Woo),김수현(Suhyeon Kim),김강현(Kanghyun Kim),윤승빈(Seungbin Yoon),안태창(Taechang An),김건휘(Geon Hwee Kim),임근배(Geunbae Lim) 대한기계학회 2021 大韓機械學會論文集B Vol.45 No.5
공간해상도가 우수한 미세전극은 그 작은 크기로 인해 임피던스와 노이즈가 증가하는 한계가 있다. 따라서 고성능의 미세전극을 개발하기 위해서는 공간해상도와 임피던스 특성을 동시에 개선할 수 있는 표면처리 기술의 개발이 필요하다. 본 연구에서는 전기화학도금을 이용하여 미세전극 표면에 수십 nm 크기의 Pt 나노구조물을 제작하였다. Pt 나노구조로 표면개질된 미세전극은 개질하기 전의 미세전극과 비교하여 임피던스 수치가 평균 86% 감소하였다. 또한, CSC 측정과 EIS 분석, 임피던스 등가회로 모델링을 통해 Pt 나노구조를 가지는 미세전극의 개선된 전기화학적 특성을 확인하였다. 본 연구에서 제안한 표면개질 기술은 기존의 제작된 전극에도 적용 가능한 후처리 기술로 다양한 구조와 재료를 가진 미세전극에 적용할 수 있다. Microelectrodes with excellent spatial resolution have a limit of large impedance and noise. Therefore, to develop a high-performance microelectrode, it is necessary to develop a surface modification technology that can simultaneously improve spatial resolution and the impedance characteristics. In this study, Pt nanostructures of several tens of nanometers were synthesized on the surface of microelectrodes via electrochemical deposition. The impedance value of the Pt nanostructure-based surface-modified microelectrode was reduced by an average of 86%, compared with that of the bare microelectrode. In addition, through the CSC measurement, EIS analysis, and impedance equivalent circuit modeling, the improved electrochemical properties of Pt nanostructure-based modified microelectrodes were confirmed. The surface modification used in this study is a post-processing technology that is utilized for prefabricated electrodes, and it can be applied to microelectrodes with various structures and materials.