연구성과 게시판목록 | 기초과학 자율운영 중점연구소

Total 83건, 7/9

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[논문] Abbas Ahmad Khan - Effect of Fe doping on the structural and optical properties of ZnS macro-spheres 위치 확인

Effect of Fe doping on the structural and optical properties of ZnS macro-spheres by Saima Zafar;Muhammad Zubair;Syed Mujtaba Shah;Muhammad Imtiaz Khan;Abbas Ahmad Optik 2022, 262(0); https://doi.org/10.1016/j.ijleo.2022.169342 Abstract Objective Doping of ZnS by the transition metal ions has perceived considerable attention in industrial applications in light-emitting displays and optical sensors. Herein, we have studied the effect of Fe doping on structural and optical properties of ZnS macro-spheres. Methods ZnS macro-sphere with and without Fe doping are synthesized by a simple and cost-effective co-precipitation method and characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR) spectroscopy to study the structural properties. Moreover, UV-Vis spectroscopy was performed to investigate the optical properties of un-doped and Fe-doped ZnS macro-spheres. Results XRD confirms the polycrystalline nature of single-phase cubic structure of as-grown and Fe-doped ZnS macro-spheres. Moreover, the Fe substitute in ZnS inter-layer space thickness decreased and the crystallite size increased. FESEM shows the morphology of semi-spherical macro-spheres with wide micrometer-size distribution (~ 7–8 µm), agglomerated from several closely embedded primary nano-grains. FTIR spectra found that the specific functional groups associated with the vibrational modes of samples present in the range of 400–800 cm−1. UV-Visible spectroscopy shows that the absorption maximum is red-shifted in the case of Fe-doped ZnS. The band gap of as-grown ZnS macro-sphere was found to be 3.46 eV, which was significantly tuned to 3.22 eV by Fe dopant. Conclusions The synthesized Fe-doped ZnS macro-spheres show improved structural and optical properties and potential optoelectronic device applications. Keywords Fe-doped ZnSMacro-spheresCubic structureBand gapOptical property
- 22
- 작성자박은영
- 작성일2023-01-16
- 333
- 동영상동영상
E-House 301동 기숙사식당

02-3277-5910
21
[논문] 이순일, 안영환 - Effects of Oxygen Vacancies in a Zinc Oxide Electron Transport Layer on Long-Term Degradation 위치 확인

Effects of Oxygen Vacancies in a Zinc Oxide Electron Transport Layer on Long-Term Degradation by Shin Young Ryu;Na Young Ha;Yeong Hwan. Ahn;Ji-Yong Park;Soonil Lee ACS Applied Energy Materials 2022, 5(8); https://doi.org/10.1021/acsaem.2c01325 Abstract We studied changes in current density–voltage (J–V) characteristics of organic solar cells (OSCs) with a ZnO electron-transport layer (ETL) with respect to illumination intensity and aging time. Unlike an encapsulated OSC that remained almost intact up to 195 h, an unsealed OSC showed steady degradation. To elucidate the origin of long-term degradation, we carried out systematic simulations and identified six parameters that were responsible for aging effects in dark J–V curves. Among these six parameters, additional adjustments were necessary only for donor density and energy-barrier height, both of which were linked to a ZnO ETL, to reproduce a set of J–V curves concomitantly measured at 12 illumination conditions. We note that oxygen vacancies in ZnO behave as electron donors and, additionally, result in dipole-moment losses. Consequently, reoxidation of a ZnO ETL resulted from slow diffusion of ambient oxygen or water, lowered the electron quasi-Fermi level, and increased the energy-barrier height. On the contrary, light-induced generation of oxygen vacancies, a short-term effect that disappears after turning illumination off, shifted the electron quasi-Fermi level upward and decreased the energy-barrier height. Because light-induced effects counteracted those of long-term reoxidation, light intensity-dependent variations in J–V curves became more prominent with aging. KEYWORDS: organic solar cell zinc oxide oxygen vacancy long-term degradation photo-induced effects
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- 작성자박은영
- 작성일2023-01-16
- 314
- 동영상동영상
E-House 301동 기숙사식당

02-3277-5910
19
[논문] 김승주 - Polymorphism and sodium-ion conductivity of NaTa2PO8 synthesized via the Li+/Na+ ion-exchange reaction of LiT 위치 확인

Polymorphism and sodium-ion conductivity of NaTa2PO8 synthesized via the Li+/Na+ ion-exchange reaction of LiTa2PO8 by Jaegyeom Kim;Junho Ha;Fouzia Khefif;Jong-Young Kim;Jae-Hwan Pee;Seung-Joo Kim Ceramics International, 2022, 48(14); https://doi.org/10.1016/j.ceramint.2022.04.052 Abstract Ion exchange reaction is a promising method to explore metastable compounds that could not be synthesized by conventional high-temperature solid-phase reactions. Herein, a new sodium tantalum phosphate, NaTa2PO8 was synthesized via the Li+/Na+ ion-exchange reaction of the parent compound, LiTa2PO8 in molten NaNO3 medium. NaTa2PO8 underwent an irreversible phase transition from the low- (LT-NaTa2PO8 to the high-temperature polymorph (HT-NaTa2PO8) at approximately 1000 °C. The crystal structures were solved using an ab initio structural determination method based on synchrotron X-ray powder diffraction data. The LT-NaTa2PO8 presented an orthorhombic structure, closely related to that of the parent LiTa2PO8 structure. In contrast, the HT-NaTa2PO8 was found to adopt a monoclinic structure, belonging to a family of monophosphate tungsten bronzes with pentagonal tunnels. The ionic conductivities of LT-NaTa2PO8 (σ = 5 × 10−5 S/cm at 309 °C) and HT-NaTa2PO8 (σ = 2 × 10−7 S/cm at 300 °C) exhibited Arrhenius behavior with activation energies of 0.49 and 0.79 eV, respectively. Bond valence energy landscape (BVEL) calculations indicated that a three-dimensional (3D) conduction pathway is formed in LT-NaTa2PO8 structure, while the conduction pathway in HT-NaTa2PO8 shows a two-dimensional (2D) character. Keywords Ion-exchangePolymorphismX-ray diffractionIonic conductivity
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- 작성자박은영
- 작성일2023-01-16
- 335
- 동영상동영상
E-House 301동 기숙사식당

02-3277-5910
17
[논문] 박대찬 - PHF20 is crucial for epigenetic control of starvation-induced autophagy through enhancer activation 위치 확인

PHF20 is crucial for epigenetic control of starvation-induced autophagy through enhancer activation by Se Won Park;Jaehoon Kim;Sungryong Oh;Jeongyoon Lee;Joowon Cha;Hyun Sik Lee;Keun Il Kim;Daechan Park;Sung Hee Baek Nucleic Acids Research, 2022, 50(14); https://doi.org/10.1093/nar/gkac584 Abstract Autophagy is a catabolic pathway that maintains cellular homeostasis under various stress conditions, including conditions of nutrient deprivation. To elevate autophagic flux to a sufficient level under stress conditions, transcriptional activation of autophagy genes occurs to replenish autophagy components. Thus, the transcriptional and epigenetic control of the genes regulating autophagy is essential for cellular homeostasis. Here, we applied integrated transcriptomic and epigenomic profiling to reveal the roles of plant homeodomain finger protein 20 (PHF20), which is an epigenetic reader possessing methyl binding activity, in controlling the expression of autophagy genes. Phf20 deficiency led to impaired autophagic flux and autophagy gene expression under glucose starvation. Interestingly, the genome-wide characterization of chromatin states by Assay for Transposase-Accessible Chromatin (ATAC)-sequencing revealed that the PHF20-dependent chromatin remodelling occurs in enhancers that are co-occupied by dimethylated lysine 36 on histone H3 (H3K36me2). Importantly, the recognition of H3K36me2 by PHF20 was found to be highly correlated with increased levels of H3K4me1/2 at the enhancer regions. Collectively, these results indicate that PHF20 regulates autophagy genes through enhancer activation via H3K36me2 recognition as an epigenetic reader. Our findings emphasize the importance of nuclear events in the regulation of autophagy.
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- 작성자박은영
- 작성일2023-01-16
- 347
- 동영상동영상
E-House 301동 기숙사식당

02-3277-5910
15
[논문] 안영환, Khan - Orientation-Mediated Luminescence Enhancement and Spin-Orbit Coupling in ZnO Single Crystals 위치 확인

Orientation-Mediated Luminescence Enhancement and Spin-Orbit Coupling in ZnO Single Crystals by Ali Hassan;Abbas Ahmad Khan;Yeong Hwan Ahn;Muhammad Azam;Muhammad Zubair;Wei Xue;Yu Cao Nanomaterials, 2022, 12(13); https://doi.org/10.1063/5.0092654 Abstract Temperature-, excitation wavelength-, and excitation power-dependent photoluminescence (PL) spectroscopy have been utilized to investigate the orientation-modulated near band edge emission (NBE) and deep level emission (DLE) of ZnO single crystals (SCs). The near-band-edge emission of ZnO SC with orientation exhibits strong and sharp emission intensity with suppressed deep level defects (mostly caused by oxygen vacancies Vo). Furthermore, Raman analysis reveals that orientation has dominant E2 (high) and E2 (low) modes, indicating that this direction has better crystallinity. At low temperature, the neutral donor-to-bound exciton (DoX) transition dominates, regardless of the orientation, according to the temperature-dependent PL spectra. Moreover, free-exciton (FX) transition emerges at higher temperatures in all orientations. The PL intensity dependence on the excitation power has been described in terms of power-law (I~Lα). Our results demonstrate that the α for , , and is (1.148), (1.180), and (1.184) respectively. In short, the comprehensive PL analysis suggests that DoX transitions are dominant in the NBE region, whereas oxygen vacancies (Vo) are the dominant deep levels in ZnO. In addition, the orientation contains fewer Vo-related defects with intense excitonic emission in the near band edge region than other counterparts, even at high temperature (~543 K). These results indicate that growth direction is favorable for fabricating ZnO-based highly efficient optoelectronic devices. Keywords: zinc oxide; single crystal; photoluminescence; exciton; impurities and defects
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- 작성자박은영
- 작성일2023-01-16
- 306
- 동영상동영상
E-House 301동 기숙사식당

02-3277-5910
13
[논문] 유성주 - Hot carrier extraction from plasmonic–photonic superimposed heterostructures 위치 확인

Hot carrier extraction from plasmonic–photonic superimposed heterostructures by Sanghyuk Lee;Sungju Yu Journal of Chemical Physics, 2022 https://doi.org/10.1063/5.0092654 Abstract Plasmonic nanostructures have been exploited in photochemical and photocatalytic processes owing to their surface plasmon resonance characteristics. This unique property generates photoinduced potentials and currents capable of driving chemical reactions. However, these processes are hampered by low photon conversion and utilization efficiencies, which are issues that need to be addressed. In this study, we integrate plasmonic photochemistry and simple tunable heterostructure characteristics of a dielectric photonic crystal for the effective control of electromagnetic energy below the diffraction limit of light. The nanostructure comprises high-density Ag nanoparticles on nanocavity arrays of SrTiO3 and TiO2, where two oxides constitute a chemical heterojunction. Such a nanostructure is designed to form intense electric fields and a vectorial electron flow channel of Ag → SrTiO3 → TiO2. When the plasmonic absorption of Ag nanoparticles matched the photonic stopband, we observed an apparent quantum yield of 3.1 × 10−4 e− per absorbed photon. The contributions of light confinement and charge separation to the enhanced photocurrent were evaluated.
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- 작성자박은영
- 작성일2023-01-13
- 305
- 동영상동영상
E-House 301동 기숙사식당

02-3277-5910
11
[논문] 유영동 - Enhanced Optical Third-Harmonic Generation in Phase-Engineered MoTe2 Thin Films 위치 확인

Enhanced Optical Third-Harmonic Generation in Phase-Engineered MoTe2 Thin Films by Seongju Ha;Hyeonkyeong Kim;Hyunjun Nam;Jungseok Choi;Kwanbyung Chae;Jae-Ung Lee;Ji-Yong Park;Youngdong Yoo;Dong-Il Yeom ACS Photonics, 2022 https://doi.org/10.1021/acsphotonics.2c00222 Abstract Molybdenum ditelluride (MoTe2) is a relatively unexplored layered transition metal dichalcogenide in nonlinear optics. Several recent studies have shown that MoTe2 has strong second-order optical nonlinearities originating from tellurium atoms. However, the third-order optical nonlinearities of MoTe2 have not been explored yet, except for the nonparametric saturable absorption process. Here we report the enhanced optical third-harmonic generation in phase-engineered MoTe2 thin films. MoTe2 films, including 2H and 1T′ phases simultaneously, are synthesized by the flux-controlled phase-engineering method, and their nonlinear response is characterized. We observe that the 2H-MoTe2 film exhibits up to a 15-fold stronger nonlinear signal than that of the 1T′-phase film. The estimated third-order effective nonlinear susceptibility of 2H-MoTe2 is 9.3 × 10–19 m2 V–2 maximum, which is larger than highly nonlinear layered materials such as molybdenum disulfide. Our MoTe2 film synthesized with the desired phase over a large area will be a potential building block for ultrathin nonlinear photonics.
- 10
- 작성자박은영
- 작성일2023-01-13
- 323
- 동영상동영상
E-House 301동 기숙사식당

02-3277-5910
9
[논문] 안영환 - Terahertz thermal curve analysis for label-free identification of pathogens 위치 확인

Terahertz thermal curve analysis for label-free identification of pathogens by S. W. Jun;Y. H. Ahn Nature Communications, 2022 https://doi.org/10.1038/s41467-022-31137-2 Abstract In this study, we perform a thermal curve analysis with terahertz (THz) metamaterials to develop a label-free identification tool for pathogens such as bacteria and yeasts. The resonant frequency of the metasensor coated with a bacterial layer changes as a function of temperature; this provides a unique fingerprint specific to the individual microbial species without the use of fluorescent dyes and antibodies. Differential thermal curves obtained from the temperature-dependent resonance exhibit the peaks consistent with bacterial phases, such as growth, thermal inactivation, DNA denaturation, and cell wall destruction. In addition, we can distinguish gram-negative bacteria from gram-positive bacteria which show strong peaks in the temperature range of cell wall destruction. Finally, we perform THz melting curve analysis on the mixture of bacterial species in which the pathogenic bacteria are successfully distinguished from each other, which is essential for practical clinical and environmental applications such as in blood culture.
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- 작성자박은영
- 작성일2023-01-13
- 330
- 동영상동영상
E-House 301동 기숙사식당

02-3277-5910
7
[논문] 김유권 - WS2/p-Si-based photocathodes with high activity originated from the unique vertical geometry of the 2D WS2 위치 확인

WS2/p-Si-based photocathodes with high activity originated from the unique vertical geometry of the 2D WS2 nanoplatelets by Malkeshkumar Patel;Thanh Tai Nguyen;Jina Kim;Joondong Kim;Yu Kwon Kim FlatChem, 2022 https://doi.org/10.1016/j.flatc.2022.100361 Abstract Earth-abundant two-dimensional (2D) materials-based photocathodes for solar hydrogen production may replace conventional noble metal-based ones when they can be grown with a proper orientation and dimension for efficient charge transfer and catalytic reactions. Here, we show that WS2 films can be grown as wafer-scale films with unique vertically aligned 2H-WS2 nanoplatelets using a single-step vacuum deposition process directly on substrates such as Si wafer and F-doped tin oxide (FTO)/glass. The as-grown WS2/p-Si shows enhanced photocathode performances that are attributed to the unique vertical WS2 nanoplatelet structure, which endows excellent antireflection properties (reflectance as low as ∼ 4%) for enhanced absorption, high photocurrent density (ca. 37 mA cm−2) at low overpotential optimized by controlled vertical length, and catalytically active WS2 edge-sites exposed to the surface for excellent catalytic hydrogen evolution reaction (HER). The results suggest that the nanostructured WS2/p-Si heterostructures are promising multi-functional photocathodes for solar hydrogen production with excellent stability for long-term operation in ambient condition.
- 6
- 작성자박은영
- 작성일2023-01-13
- 324
- 동영상동영상
E-House 301동 기숙사식당

02-3277-5910
5
[논문] 안수현 - Percutaneous radiofrequency ablation of hepatocellular carcinoma in a recent cohort of a tertiary cancer cent 위치 확인

Percutaneous radiofrequency ablation of hepatocellular carcinoma in a recent cohort of a tertiary cancer center: Incidence and factors associated with major complications and unexpected hospitalization events by Min Geun Jo;Min Woo Lee;Soohyun Ahn;Tae Wook Kang;Kyoung Doo Song;Dong Ik Cha;Ji Hye Min;Hyunchul Rhim ultrasonography, 2022 https://doi.org/10.14366/usg.22041 Abstract Purpose This study aimed to assess the incidence of and factors associated with major complications, delayed discharge, and emergency room (ER) visits or readmission after percutaneous radiofrequency ablation (RFA) for single hepatocellular carcinoma (HCC) Methods A total of 188 patients with treatment-naïve single HCCs Results Major complications occurred in 3.2% (6/188) of the patients. The longest diameter of the ablation zone was significantly larger in patients with major complications (P=0.023). Delayed discharge occurred in 5.8% (9/188) of the patients, for which albumin-bilirubin grade 3 was identified as an important determinant. No variables other than major complications were significantly associated with ER visits or readmission, which occurred in 7.0% (13/188) of the patients. Major complications, delayed discharge, and ER visits or readmission were not substantially related to the post-treatment outcomes of LTP and overall survival. Conclusion This study confirmed RFA as a highly safe procedure for single HCCs Keywords: Hepatocellular carcinoma; Radiofrequency ablation; Complications
- 4
- 작성자박은영
- 작성일2023-01-13
- 319
- 동영상동영상
E-House 301동 기숙사식당

02-3277-5910