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Research Project Fotokatalitik ve Süreksiz Fiberde Güçlendirilmiş Dental Kompozitlerin Geliştirilmesi(2012) Park, Jongee; Şaşmazel, Hilal Türkoğlu; Öztürk, Abdullah; Bişkin, Erhan-Article Citation - WoS: 4Citation - Scopus: 5In Vitro Evaluation of Tooth-Colored Yttria Stabilized Zirconia Ceramics(Taylor & Francis Ltd, 2021) Akarsu, Melis Kaplan; Basar, Ahmet Ozan; Sasmazel, Hilal Turkoglu; Park, Jongee; Ozturk, AbdullahEffects of MoCl3 and NiCl2, originally incorporated as coloring agent, on the cellular response of 3 mol% yttria stabilized zirconia (3Y-TZP) ceramics was investigated. MoCl3 and NiCl2-MoCl3 incorporated, tooth-colored 3Y-TZP ceramics were produced through cold isostatic pressing at 100 MPa followed by pressureless sintering at 1450 degrees C for 2 h. Aging was performed on the sintered ceramics using distilled water in a reactor at 134 degrees C at 2.3 bar pressure for 2 h. The phases developed during different stages of processing were identified by X-ray diffraction (XRD) analysis. In vitro cell culture studies were carried out using L929 fibroblast cell line. The cell viability and proliferation studies revealed that none of the specimens showed cytotoxicity with respect to coloring. Confocal laser scanning microscope (CLSM) analyses suggested that all of the specimens exhibited good in vitro cytocompatibility. Enhancement in cell attachment, adhesion, and proliferation was observed in all specimens via scanning electron microscope (SEM) analysis. Although the coloring process did not improve the proliferation performance of the aged specimens, the incorporation of transition metals enhanced the in vitro performance of 3Y-TZP ceramics.Article Citation - WoS: 23Citation - Scopus: 27Facile synthesis of CsPbBr3/PbSe composite clusters(Taylor & Francis Ltd, 2018) Thang Phan Nguyen; Ozturk, Abdullah; Park, Jongee; Sohn, Woonbae; Tae Hyung Lee; Jang, Ho Won; Kim, Soo YoungIn this work, CsPbBr3 and PbSe nanocomposites were synthesized to protect perovskite material from self-enlargement during reaction. UV absorption and photoluminescence (PL) spectra indicate that the addition of Se into CsPbBr3 quantum dots modified the electronic structure of CsPbBr3, increasing the band gap from 2.38 to 2.48 eV as the Cs:Se ratio increased to 1:3. Thus, the emission color of CsPbBr3 perovskite quantum dots was modified from green to blue by increasing the Se ratio in composites. According to X-ray diffraction patterns, the structure of CsPbBr3 quantum dots changed from cubic to orthorhombic due to the introduction of PbSe at the surface. Transmission electron microscopy and X-ray photoemission spectroscopy confirmed that the atomic distribution in CsPbBr3/PbSe composite clusters is uniform and the composite materials were well formed. The PL intensity of a CsPbBr3/PbSe sample with a 1:1 Cs: Se ratio maintained 50% of its initial intensity after keeping the sample for 81 h in air, while the PL intensity of CsPbBr3 reduced to 20% of its initial intensity. Therefore, it is considered that low amounts of Se could improve the stability of CsPbBr3 quantum dots.Article Osmanlı ve Joseon Seramik Sanatının Karşılaştırmalı İncelemesi: Kültürel Etkileşimler ve Teknik Yaklaşımlar(2025) Park, Jongee; Özer, Seren; Yu, EunmiBu çalışmada, Osmanlı ve Joseon dönemlerine ait seramiklerin üretim teknikleri ve diğer hanedanlıklarla olan kültürel etkileşimlerinin seramiklerin gelişimine etkisi ayrıntılı olarak incelenmiştir. Her iki dönemin seramik sanatçıları, önceki hanedanlıklardan edindikleri bilgileri kendi kültürel miraslarıyla harmanlayarak özgün eserler yaratmıştır. Erken Osmanlı seramikleri, Selçuklu desenlerini İslam kültürüne uygun şekilde yorumlarken, Erken Joseon Buncheong seramikleri, Goryeo Seladonlarından esinlenmiş, ancak Budizm etkisinden uzaklaşarak minimalist bir tasarıma ve Konfüçyüsçü değerlere yönelmiştir. Zamanla, her iki hanedanlık Çin ile kurdukları ilişkiler doğrultusunda Mavi-beyaz porselenlerden etkilenmiş ve üretimlerini buna göre uyarlamıştır. Osmanlı Mavi-beyaz seramikleri, İznik ve Kütahya merkezlerinde üretilmiş olup, kobalt mavisi başta olmak üzere farklı renk tonlarıyla zenginleştirilmiştir. Joseon dönemi Cheonghwa Baekja seramiklerinde ise, desenler mavi-beyaz paletle birleşerek sade bir estetik anlayışı yaratmıştır. Üretim teknikleri açısından, her iki dönemde de benzer yöntemler kullanılsa da, malzeme ve fırınlama süreçlerinde belirgin farklılıklar bulunmaktadır. Ayrıca, Milet işi ve Sangam teknikleri, sırasıyla Osmanlı ve Joseon’a ait özgün sanatsal yaklaşımlardır.Article Citation - WoS: 6Citation - Scopus: 6Diethanolamine Modified Perovskite-Substrate Interface for Realizing Efficient Esl-Free Pscs(Mdpi, 2023) Sajid, Sajid; Alzahmi, Salem; Wei, Dong; Ben Salem, Imen; Park, Jongee; Obaidat, Ihab M.Simplifying device layout, particularly avoiding the complex fabrication steps and multiple high-temperature treatment requirements for electron-selective layers (ESLs) have made ESL-free perovskite solar cells (PSCs) attractive. However, the poor perovskite/substrate interface and inadequate quality of solution-processed perovskite thin films induce inefficient interfacial-charge extraction, limiting the power conversion efficiency (PCEs) of ESL-free PSCs. A highly compact and homogenous perovskite thin film with large grains was formed here by inserting an interfacial monolayer of diethanolamine (DEA) molecules between the perovskite and ITO substrate. In addition, the DEA created a favorable dipole layer at the interface of perovskite and ITO substrate by molecular adsorption, which suppressed charge recombination. Comparatively, PSCs based on DEA-treated ITO substrates delivered PCEs of up to 20.77%, one of the highest among ESL-free PSCs. Additionally, this technique successfully elongates the lifespan of ESL-free PSCs as 80% of the initial PCE was maintained after 550 h under AM 1.5 G irradiation at ambient temperature.Article Citation - WoS: 20Citation - Scopus: 24Lead-Free Perovskite Homojunction-Based Htm-Free Perovskite Solar Cells: Theoretical and Experimental Viewpoints(Mdpi, 2023) Sajid, Sajid; Alzahmi, Salem; Salem, Imen Ben; Park, Jongee; Obaidat, Ihab M.Simplifying the design of lead-free perovskite solar cells (PSCs) has drawn a lot of interest due to their low manufacturing cost and relative non-toxic nature. Focus has been placed mostly on reducing the toxic lead element and eliminating the requirement for expensive hole transport materials (HTMs). However, in terms of power conversion efficiency (PCE), the PSCs using all charge transport materials surpass the environmentally beneficial HTM-free PSCs. The low PCEs of the lead-free HTM-free PSCs could be linked to poorer hole transport and extraction as well as lower light harvesting. In this context, a lead-free perovskite homojunction-based HTM-free PSC was investigated, and the performance was then assessed using a Solar Cell Capacitance Simulator (SCAPS). A two-step method was employed to fabricate lead-free perovskite homojunction-based HTM-free PSCs in order to validate the simulation results. The simulation results show that high hole mobility and a narrow band gap of cesium tin iodide (CsSnI3) boosted the hole collection and absorption spectrum, respectively. Additionally, the homojunction's built-in electric field, which was identified using SCAPS simulations, promoted the directed transport of the photo-induced charges, lowering carrier recombination losses. Homojunction-based HTM-free PSCs having a CsSnI3 layer with a thickness of 100 nm, defect density of 10(15) cm(-3), and interface defect density of 10(18) cm(-3) were found to be capable of delivering high PCEs under a working temperature of 300 K. When compared to formamidinium tin iodide (FASnI(3))-based devices, the open-circuit voltage (V-oc), short-circuit density (J(sc)), fill factor (FF), and PCE of FASnI(3)/CsSnI3 homojunction-based HTM-free PSCs were all improved from 0.66 to 0.78 V, 26.07 to 27.65 mA cm(-2), 76.37 to 79.74%, and 14.62 to 19.03%, respectively. In comparison to a FASnI(3)-based device (PCE = 8.94%), an experimentally fabricated device using homojunction of FASnI(3)/CsSnI3 performs better with V-oc of 0.84 V, J(sc) of 22.06 mA cm(-2), FF of 63.50%, and PCE of 11.77%. Moreover, FASnI(3)/CsSnI3-based PSC is more stable over time than its FASnI(3)-based counterpart, preserving 89% of its initial PCE. These findings provide promising guidelines for developing highly efficient and environmentally friendly HTM-free PSCs based on perovskite homojunction.Article Tio2 Films With Various Crystal Structures for Single and Bilayer Photoanodes of Dye-Sensitized Solar Cells(2018) Erdoğan, Nursev; Park, Jongee; Öztürk, AbdullahPhase pure and composite TiO2 nanopowders exhibiting various crystal structures (anatase, rutile and brookite) are used asphotoanode in dye-sensitized solar cells. The nanopowders are deposited in paste form onto a conducting oxide glass usingdoctor blade method in single layer and bilayers. The highest solar efficiency achieved by the single layer photoanode composedof > 99 wt % anatase crystals was 2.86 %. The solar efficiency of 4.93 % has been harvested via bilayer photoanode built byapplying a layer consisting 55 wt % anatase and 45 wt % rutile phase nanoparticles on top of the layer composed of a mixtureof > 99 wt % anatase crystals. The improved photovoltaic performance is attributed to anatase dominated bottom layer whichfacilitates electron charge generation with high surface area and charge transport by proper crystal structure as well assynergistic effect of binary phase content of the photoanodes. The porous structure of top layer enhances diffusion of theI−/I3−electrolyte in the bilayer TiO2 photoanode.Research Project Mekanik Bilyalı Öğütmeyle Yüksek Etkinlikte Fotokatalitik $tio_2$ Tozu ve Nano Boyutlu Titanya Sol Üretimi(2012) Öztürk, Abdullah; Timuçin, Muharrem; Karakaş, Gürkan; Park, Jongee-
