https://scholarworks.unist.ac.kr/handle/201301/119 Wed, 13 May 2026 04:14:05 GMT 2026-05-13T04:14:05Z https://scholarworks.unist.ac.kr/handle/201301/91560 Title: Surface Modification and Functionalization Of CdSe and InP Quantum Dots Using Multidentate Polymer Ligands For Imaging of Single Protein Molecule Author(s): Kim, Hyerim Abstract: Quantum dots (QDs) exhibit size‐dependent emission wavelengths, high brightness, and excellent photoluminescence quantum yields (PLQY), making them valuable fluorophores for various fields. Although ligand exchange enables QDs surface modification by replacing native hydrophobic ligands with hydrophilic alternatives, conventional monodentate ligands often suffer from poor colloidal stability and weak binding, ultimately limiting their use in biological environments. For reliable bio-applications, QDs must maintain stable aqueous dispersion, possess compact hydrodynamic size, and minimize nonspecific binding (NSB). To address these challenges, we designed and synthesized multidentate polymer ligands consisting of anchor (A), hydrophilic (H), and functional (F) groups. These polymers give good colloidal stability, increasing water solubility and giving bio- functionalization. In Chapter II, we applied this multidentate ligand to CdSe QDs and developed a two-step ligand- exchange procedure to obtain compact, water-soluble QDs with superior properties. The polymer- coated QDs showed excellent resistance to NSB and retained functional azido groups for strain- promoted click chemistry. Furthermore, Efficient antibody conjugation was achieved using DBCO- modified antibodies. Systematic electrophoretic mobility shift assays (EMSA) revealed that PEG itself induces XPA–DNA dissociation, independent of various factors. By tuning the relative fractions of A-, H-, and F-groups on the QD surface, we identified polymer compositions that do not induce XPA dissociation from DNA. Therefore, the optimized QDs enabled single-molecule visualization of XPA recognizing a specific site of DNA in DNA curtain assays. In Chapter III, we further expanded our surface-engineering platform by synthesizing diverse polymer ligands—P[LA-Z], P[LA-Z-PEG COOH], and P[LA-Z-PEG N₃]—for use on InP QDs. And also FT-IR, XPS, DLS, UV–vis, PL, XRD, and TRPL analyses confirmed successful ligand exchange to InP QDs surface, preserved crystal structure, and strong optical properties following surface modification. The preservation of functional groups (azide, carboxylic acid) on the polymer-coated InP QDs further confirms their broad utility as adaptable platforms for diverse bio-conjugation and biological applications. Major: School of Energy and Chemical Engineering Sat, 31 Jan 2026 15:00:00 GMT https://scholarworks.unist.ac.kr/handle/201301/91560 2026-01-31T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/91559 Title: Tailored Electrolyte Design Based on E/S Ratio for Practical Lithium-Sulfur Batteries Author(s): Park, Seeun Abstract: Achieving high energy density in lithium–sulfur batteries (LSBs) requires operating under ultra- lean electrolyte conditions, yet the electrochemical behavior is highly sensitive to the electrolyte-to- sulfur (E/S) ratio. Despite its importance, most previous studies evaluated electrolyte compositions at a single E/S ratio, overlooking the coupled impact of electrolyte quantity and solvation characteristics. In this study, we systematically investigate how the E/S ratio determines cell polarization, sulfur redox kinetics, and lithium metal stability. The solvating power of the electrolyte is subsequently examined as a key factor controlling the solubility of polysulfides and the interfacial chemistry at both electrodes. Strong-solvating electrolytes promote rapid sulfur conversion but accelerate lithium corrosion and electrolyte depletion, while weak-solvating electrolytes suppress parasitic reactions at anode yet induce sluggish redox kinetics at lean conditions. By coupling the effects of E/S ratio and solvating power, we identify the optimal balance between E/S ratio and solvating power required for stable long-term cycling. This work provides a framework for electrolyte design in practical lean-electrolyte LSBs, highlighting the need for co-optimization of E/S ratio and solvating power to simultaneously enhance energy density and durability. Major: School of Energy and Chemical Engineering Sat, 31 Jan 2026 15:00:00 GMT https://scholarworks.unist.ac.kr/handle/201301/91559 2026-01-31T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/91556 Title: Photo-Programmable Semi-IPN Glycol Gels with Microscale Thermal-Mechanical Encoding Author(s): Kim, Ji O Abstract: Organogels, particularly glycol gels, have emerged as promising candidates for flexible electronic substrates due to their inherent stretchability and wide operating temperature range compared to conventional hydrogels. However, their application in next-generation deformable displays is often hindered by insufficient mechanical robustness, thermal dimensional instability, and vulnerability to chemical processing. To address these limitations, this study proposes a robust semi-Interpenetrating Polymer Network (semi-IPN) substrate, wherein a rigid polyimide (PI) network is physically entangled within a tunable glycol gel matrix. The fabrication process was streamlined by leveraging a spatially selective photo-thermal imidization technique, eliminating the need for high-temperature ovens. Optimization of the precursor concentration revealed that a 1 wt% poly(amic acid) loading provides the ideal balance between optical clarity and mechanical reinforcement. The introduction of the PI network significantly enhanced the material’s performance, achieving a 35% reduction in the Coefficient of Thermal Expansion (CTE), superior moisture resistance under accelerated aging conditions (85°C/85% RH), and robust stability against aggressive display process solvents such as D2 and NI555. Furthermore, the developed material demonstrated intrinsic thermo-responsive shape memory capabilities with high fixity (>96%) and recovery rates. Utilizing the photo-thermal patterning capability, a "Rigid Island" architecture was successfully realized. This structure induces a modulus mismatch between the rigid, imidized islands and the compliant matrix, effectively achieving strain isolation to protect integrated electronic components during deformation. Consequently, this study establishes the photo-thermally imidized semi-IPN glycol gel as a versatile and process-compatible platform for advanced form-factor-free electronics. Keywords: Semi-IPN Polymer Gel; Glycol Gel; Polyimide composite; Flexible Substrate; Shape Deformable Substrate; Free-form Display Major: School of Energy and Chemical Engineering Sat, 31 Jan 2026 15:00:00 GMT https://scholarworks.unist.ac.kr/handle/201301/91556 2026-01-31T15:00:00Z https://scholarworks.unist.ac.kr/handle/201301/91557 Title: WS2-Derived Na2S/W Composite Layer for Stable Sodium Metal Batteries Author(s): Yu, Jinyeong Abstract: Sodium metal is an attractive anode for next-generation secondary batteries due to its high theoretical capacity, low redox potential, and cost advantages. However, uncontrolled dendrite growth severely limits its practical implementation. Here, we introduce a scalable, straightforward blade-casting strategy to coat WS2 onto a polypropylene (PP) separator, effectively regulating Na deposition and extending safe battery operation. Upon contact with Na metal, WS2 spontaneously undergoes a conversion reaction to form Na2S and metallic W, generating a stable Na2S/W composite interlayer at the anode interface. This interlayer on a polymeric separator reduces the Na+ diffusion barrier, facilitates fast, uniform ion transport, and serves as a local electrolyte reservoir that homogenizes Na+ flux. Simultaneously, the metallic W phase induced by WS2 enhances the mechanical strength of the separator, providing physical resistance against dendrite penetration. Consequently, Na; Na symmetric cells using the WS2@PP separator deliver highly stable cycling for 1,000 h at 2 mA cm-2 with a low overpotential of ~20 mV. In Na; Na3V2(PO4)3 full cells, the separator enables stable cycling for 200 cycles at 2 C, with excellent capacity retention and no significant alteration. This separator-engineering strategy offers a practical and manufacturable route to stabilize sodium-metal anodes and advance long-life, high-energy sodium-metal batteries. Major: School of Energy and Chemical Engineering Sat, 31 Jan 2026 15:00:00 GMT https://scholarworks.unist.ac.kr/handle/201301/91557 2026-01-31T15:00:00Z