https://scholar.dgist.ac.kr/handle/20.500.11750/69 2026-04-04T12:47:53Z https://scholar.dgist.ac.kr/handle/20.500.11750/60022 Title: Comparative analysis of macroscopic and microscopic optical absorbance in hemagglutination assay Author(s): Jeon, Dong-Gyu; Lee, Chung-Young; Cho, Chang-Hee; Lee, Gang Ho; Chang, Yongmin; Nam, Sung-Wook Abstract: We report a comparative study of macroscopic and microscopic optical absorbance in hemagglutination (HA) assay. Red blood cells (RBCs) exhibit unique optical absorbance properties with characteristic peaks including Soret, Qv, and Qo. In addition, RBCs absorb light and appear as dark contrast in bright-field microscopy images, indicating an increase in local optical density (OD). By systematic analysis of macroscopic and microscopic OD measurements and UV-Visible (UV-Vis) spectroscopy, we developed a phenomenological model of RBC agglutination and non-agglutination. The antigen-antibody reaction in RBC agglutination behaves as a catastrophic event such that networking of RBC clumps is initiated at a critical RBC concentration. We analyzed the dependence of OD on RBC concentration. At the critical RBC concentration, OD values are dropped or saturated for RBC agglutination, on the other hand, ODs keep increasing as the increase of RBC concentration for RBC nonagglutination. By the analysis of UV-Vis spectroscopy for HA assay, we provide an optimal wavelength range as 480-520 nm, away from RBC characteristic absorption peaks. For further validation, we demonstrated the ODbased HA assay for the detection of H1N1 influenza A virus. Our investigation provides insights into how to utilize the physical properties of RBCs for novel HA assay platforms. 2025-11-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/59984 Title: Enhancing CO2-to-CH4 conversion efficiency of TiO2 through synergistic morphology tuning, defect engineering, and heterojunction formation Author(s): Kim, Dongyun; LEE, Kyuseok; Park, Young Ho; Lee, Junho; Murali, Guntakrinda; In, Insik; In, Su-Il; Lee, Jeonghyeon; Shin, Chaelin; Jeong, Hyeonjong; Cho, Chang-Hee; Lee, Seung Jun Abstract: The photocatalytic reduction of CO2 into valuable fuels represents a promising pathway toward sustainable energy solutions. In this study, the CO2-to-CH4 conversion efficiency of TiO2 is enhanced by implementing synergistic strategies, including morphology tuning, defect engineering, and composite construction. Reduced TiO2 nanosheet (2D-RT) morphology is employed to construct the ternary composite photocatalyst, Cu/reduced graphene oxide/2D-RT (Cu/G/2D-RT), which outperforms 2D-RT, P25 derived reduced TiO2 (P-RT), and Cu/G/P-RT. The CH4 production rate of Cu/G/2D-RT is nearly 62 times that of P-RT and 3.4 times that of Cu/G/P-RT. The optimal defect concentration in 2D-RT improves visible light absorption and charge separation, while the 2D structure enhances interaction with rGO, leading to better charge transport. Additionally, single-electron-trapped oxygen vacancies accelerate water oxidation, producing more protons to enhance the CO2 reduction on Cu cocatalyst. The CO2 reduction significantly improved under multi-sun illumination. However, the repeated cycling led to catalyst degradation, primarily driven by partial reduction of Cu. The in-situ diffuse reflectance infrared Fourier transform spectroscopy reveals the CO2 conversion pathway. Importantly, the results demonstrate that while a high defect concentration in TiO2 enhances visible light absorption, it does not necessarily ensure enhanced charge separation, optimal band alignment in heterojunctions, and improved CO2 reduction efficiency. 2025-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58261 Title: Charge carrier localization in monolayer WS2 influenced by hBN microbubbles Author(s): Lee, Taegeon; Lee, Young-Jun; Cho, Chang-Hee; Rho, Heesuk Abstract: The energy landscapes of two-dimensional heterostructures are strongly localized by interfacial defects, which often introduce unique characteristics that can be exploited for advanced nanodevice applications. This study investigates how hBN microbubbles affect the optical and electronic properties of hBN-encapsulated monolayer WS2 using spatially resolved photoluminescence and Raman spectroscopy. Photoluminescence spectral analysis reveals a significant increase in electron density in monolayer WS2 within the region where hBN microbubbles form above WS2. The increased electron density in WS2 is attributed to the flexoelectric effect of the deformed hBN layer. Additionally, the WS2 monolayer exhibited reduced tensile strain in the bubble region compared to the fully encapsulated area, leading to an increase in exciton energy. Raman analysis, which correlates the frequencies of the in-plane and out-of-plane optical phonons in WS2, confirms the changes in strain and electron density observed in the photoluminescence results, highlighting excellent agreement between the two techniques. These findings provide valuable insights into the interplay of strain and charge doping in tuning the electronic properties of monolayer WS2 and emphasize the pivotal role of the flexoelectric effect in modulating charge doping in two-dimensional heterostructures. 2025-02-28T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58210 Title: Tunable Polariton Rabi Oscillation in Phase-Changing Perovskite Microcavities Author(s): Choi, Hyeon-Seo; Ko, Minjee; Lee, Taejin; Jung, Jin-Woo; Lee, Young-Jun; Jeong, Hyeonjong; Kim, Youngjae; Kim, Dongha; Heo, Jinhee; Lee, Shinbuhm; Lee, JaeDong; Cho, Chang-Hee Abstract: Exciton-polaritons are composite quasiparticles hybridized between excitons and photons, which are very promising to develop quantum information devices such as entangled photon pair sources and polariton qubit devices by utilizing the fascinating properties of strong nonlinearity, Bose-Einstein condensation, and superfluidity. Organic-inorganic hybrid lead halide perovskites have attracted much interest in cavity quantum electrodynamics due to their excellent excitonic properties, including strong exciton binding energy and high oscillation strength. Here, tunable Rabi oscillation of exciton-polaritons in the lead halide perovskite microcavity is demonstrated, which experiences a phase transition between orthorhombic, tetragonal, and cubic phases by varying the temperature. Over the phase transition, the Rabi frequency is probed by tracing the dispersion relation of the exciton-polaritons using Fourier plane spectroscopy. Due to the emergence of ferroelectricity in the tetragonal phase of the perovskites, the Rabi splitting can be tuned by approximate to 20%, while the corresponding exciton oscillator strength is varied by approximate to 44%. These results provide insight into novel functionalities of polariton devices by utilizing ferroic semiconductors, which can facilitate the development of tunable quantum devices. 2025-04-30T15:00:00Z