https://scholar.dgist.ac.kr/handle/20.500.11750/69 Fri, 24 Apr 2026 17:33:18 GMT 2026-04-24T17:33:18Z https://scholar.dgist.ac.kr/handle/20.500.11750/60224 Title: Self-Hybridized Multimodal Exciton-Polaritons in All-Inorganic Lead Halide Perovskite Microcrystals Author(s): Maqbool, Faisal; Tahir, Zeeshan; Rashid, Mamoon Ur; Sheeraz, Muhammad; Cho, Chang-Hee; Kim, Yong Soo Abstract: Exciton-polaritons are potential avenues for quantum fluids of light and hold great promise for future all-photonic integrated circuits and devices. Herein, self-hybridized multimodal exciton polaritons are investigated in all-inorganic lead halide perovskite microplatelets grown via the space-limited antisolvent crystallization method. Interestingly, the as-grown microcrystals not only exhibit robust excitons at room temperature but also form a photonic microcavity, providing a self-sufficient platform for strong exciton-photon coupling. Resultantly, multiple parabolic dispersions were observed in the angle-resolved photoluminescence mappings, each with a characteristic curvature flattening at large momentum, signifying multimodal polariton formation. The corresponding theoretical fits reveal considerably large Rabi-splitting values of ∼360, 336, and 320 meV for microplatelets of various thicknesses. Such large splitting is attributed to the high (∼perfect) spatial overlap between the excitonic medium and the photonic mode’s electric field. In addition, the variation in the Rabi-splitting as a function of microcrystal thickness demonstrates the facile modulation of exciton-photon coupling strength in self-hybridized systems. Besides, the distinct excitonic and photonic contents of the individual parabolic dispersions suggest the coexistence of polaritons with different compositions. Thus, our results demonstrate a straightforward platform for the realization and manipulation of strong coupling phenomenon crucial for polariton device applications. Wed, 31 Dec 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/60224 2025-12-31T15:00:00Z 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. Sun, 30 Nov 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/60022 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. Wed, 31 Dec 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/59984 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. Fri, 28 Feb 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/58261 2025-02-28T15:00:00Z