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Determination of Vitamin D by Sensor Technologies Based on Molecular Imprinted Polymers
(Izmir Institute of Technology, 2022) Ölçer, Yekta Arya; Eroğlu, Ahmet Emin; Demir, Mustafa Muammer
Vitamin D is an essential nutrient in the body; it plays important roles in human health. Both its lack and excess can have health risks. As a consequence, there is a great demand for development of simple and precise detection methods for vitamin D derivatives in different samples. Molecular imprinting polymers (MIPs) are artificial receptors that can recognize target molecules in solution. In this study, two different polymerization techniques were used to obtain MIP/NIP sorbents/films for the detection of vitamin D3. Firstly, molecular imprinted solid phase extraction (MISPE) method was proposed prior to HPLC-DAD analysis. Optimized parameters were as follows; sorbent amount of 5.0 mg for 5.0 mL of 1.0 mg/L vitamin D3 in 90:10 (v/v) ratio of H2O:MeOH solution, 5 hours sorption time and MeOH:HOAc ratio of 90:10 (v/v) as desorption solution. The accuracy of the method was verified with spike recovery test for PBS:MeOH in a ratio of 90:10 (v/v) and overall recovery was found as 85.1 (±4.3, n=3). In latter case, a quartz crystal microbalance (QCM) method was proposed for determination of vitamin D3. Electrochemical polymerization of poly(4-vinylpyridine) MIP/NIP films were achieved on gold working electrode by cyclic voltammetry (CV). Mass-transfer ability of the polymer films were analyzed by electrochemical impedance spectroscopy (EIS). The electrochemical QCM (eQCM) was used to develop thin polymer films on quartz crystals and vitamin D3 determination was achieved by QCM. In a preliminary test, as small a concentration as 0.0100 mg/L vitamin D was detected with the QCM method.
Structural Engineering of Halide Perovskites and Their Association With Organics for Optoelectronic Applications
(Izmir Institute of Technology, 2022) Yüce Çakır, Hürriyet; Demir, Mustafa Muammer; Yüksel Aldoğan, Kıvılcım
Halide perovskites show great potential for next-generation optoelectronic applications due to their unique photophysical properties with low production costs. However, their stability issues still prevent their commercialization on a large scale. The main objective of this dissertation is to understand the additive engineering strategy to improve the quality of halide perovskite films and nanocrystals for solar cells and lightemitting diodes. There are two sections to this dissertation: The first section focuses on halide perovskite films and solar cells while the second one focuses on halide perovskite nanocrystals and white light-emitting diodes. In the first section of this dissertation, in Chapter 2-3, the improvement of Sn-Pb and methylammonium-free Pb-based halide perovskite films by additives are investigated. The suppression of defects via additives is demonstrated through structural, elemental, and optical analyses. The improved performance of perovskite solar cells by decreasing defects is also shown. In Chapter 4-5, the change in stability and optical properties of the halide perovskite nanocrystals by means of additive engineering and their applications in white light-emitting diode are studied. The results in this dissertation represent a new approach to improving the structural and photophysical properties of halide perovskites and introduce a new perspective of additive engineering method in the field of halide perovskite-based optoelectronic applications.

Phd Degree / Doktora

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