Phd Degree / Doktora

Permanent URI for this collectionhttps://hdl.handle.net/11147/2869

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Author: search.filters.author.Ebil, Özgenç

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  • Doctoral Thesis
    Chemical Vapor Deposited Reusable Fluorescent Thin Film Sensor Nanoprobes for the Detection of Heavy Metal Ions
    (01. Izmir Institute of Technology, 2023) Karabıyık, Merve; Ebil, Özgenç
    Heavy metal pollution has made a serious threat to the environment and human health day by day due to developing science, technology and industrial activities, therefore, the importance of selective detection of heavy metals has increased. Heavy metals gradually accumulate in the human body, especially via water sources. Among heavy metals, cadmium is one of the most carcinogenic ones and has harmful effects even in trace amounts. Despite it, detection studies of cadmium ion are very few. This thesis study focuses on the development of Initiated Chemical Vapor Deposition (iCVD) synthesized polymer thin film based quantum dot-nitroxide radical fluorescence sensor nanoprobe, which has a multi-use property and high durability, unlike sensor probes developed for single use in liquid media, and selective detection of Cd2+ ions in real water sources. By examining the effects of pH, concentration, solvent type and reaction time, the most suitable conditions to improve the interaction between Cd2+ ion and the newly developed sensor nanoprobe were investigated. The results proved that it is possible to detect the target ion easily even in complex environments where other heavy metal ions are present. Cd2+ ion detection limit with this proposed nanoprobe was found as 0.195 μM and high recovery percentage (>90%) obtained in standard addition method. In the multi-use study, it was confirmed that nanoprobe could be used repeatedly for the selective and sensitive detection of Cd2+ ion without being influenced by the content of daily water samples. This thesis is a great guide for new fluorescent sensor applications.
  • Doctoral Thesis
    Electrochemical and Oxygen/Water Permeation Behavior of Fluorinated Siloxane Copolymers Synthesized Via Initiated Chemical Vapor Deposition
    (Izmir Institute of Technology, 2021) Cihanoğlu, Gizem; Ebil, Özgenç
    Metal-air batteries are considered as one of the best alternatives to current Li-ion batteries with their high energy densities (1000-13000 Wh/kg) also, they are lightweight, cheap, and safe. However, secondary alkaline metal-air batteries suffer from catalyst corrosion, anode passivation and corrosion, electrolyte loss, and pore-clogging leading to performance loss and reduced cycle life. This thesis aims to evaluate the feasibility of highly cross-linked, hydrophobic, and oxygen selective thin homopolymers and copolymers films as potential candidates for Gas Diffusion Layer (GDL) materials in Gas Diffusion Electrodes (GDEs) for alkaline metal-air batteries. Homopolymers of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (V4D4), 2-(perfluorohexyl)ethyl acrylate (PFHEA) and 2-(perfluoroalkyl)ethylmethacrylate (PFEMA) and their copolymers were synthesized via initiated chemical vapor deposition (iCVD). iCVD deposited fluoropolymer thin films exhibited low water transmission rates and excellent oxygen diffusion with a high oxygen/water selectivity up to 13.6. GDEs with iCVD GDLs exhibited higher oxygen reduction current density (228.2 mA cm-2) when compared to commercial counterparts (132.7 mA cm-2). In addition, the chemical stability, durability and corrosion protection aspects of these films were investigated by substrate adhesion and immersion tests in organic solvents and NaCl solution. The results of the corrosion test together with chemical stability and durability evaluation indicate that iCVD deposited copolymers exhibit excellent adhesion, good solvent resistance and offer effective physical and chemical protection without the need for surface pretreatment. iCVD copolymer films provide better anti-corrosion barriers with lower corrosion efficiency (85-99 %) for metal surfaces compared to homopolymer counterparts. By combining siloxane and fluorinated matrix, the copolymer films provide enhanced oxygen transport and reduce moisture entrance significantly as a GDLs and also improve physical, chemical, corrosion protection.
  • Doctoral Thesis
    Experimental and Computational Investigation of Transport Phenomena in Initiated Chemical Vapor Deposition (icvd) Process
    (Izmir Institute of Technology, 2017) Ateş, Selcan; Ebil, Özgenç; Ebil, Özgenç
    As a polymer thin-film deposition technique, initiated CVD (iCVD) is a heterogeneous process involving gas phase precursors and solid film formation on a solid/liquid substrates at different temperature regions. Obtaining fine-tuned film properties over different substrate geometries at different process conditions is a challenging tasks and requires experimental trials. The major goal of this study is to develop a computational model which describes all relevant transport phenomena occurring in iCVD process, and which is capable to predict the polymer film thickness at different deposition conditions for flat and/or non-flat substrates in a 3D reactor geometry. A Finite Element Analysis (FEA)-based 3D computational model, which can be applied to a variety number of iCVD reactor and substrate geometries, has been developed in the study. To validate the model, reported experimental conditions of 1H,1H,2H,2Hperfluorodecyl acrylate (PFDA) deposition with t-butyl peroxide (TBPO) initiator, and butyl acrylate (BA) deposition with t-amyl peroxide (TAPO) initiator, are applied to the model, respectively. The simulation results of both deposition processes show good agreement with experimental results reported in literature. Presented model successfully describes the relevant transport phenomena, and provides a priori predictions on polymerization rate, and film thickness on complex substrate geometries for a polymerization reaction with known kinetic data. For further studies, presented model can be modified or used as an approach for modeling of other types of CVD systems as well as facilitating process scale-up. The model can also extract valuable polymerization kinetics data provided that a sufficient number of experiments are performed at a specified substrate temperature, and process parameters and measured final film thicknesses are entered to the model.