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Kahraman, Zeynep
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04.04. Department of Photonics
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
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Scholarly Output
7
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5
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12425/1906
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1
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1
WoS Citation Count
109
Scopus Citation Count
113
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WoS Citations per Publication
15.57
Scopus Citations per Publication
16.14
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3
Supervised Theses
2
| Journal | Count |
|---|---|
| Applied Surface Science | 1 |
| Dalton Transactions | 1 |
| Journal of Materials Research | 1 |
| Journal of Physical Chemistry C | 1 |
| Materials Science & Engineering B: Solid - State Materials for Advanced Technology | 1 |
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Now showing 1 - 7 of 7
Article Citation - WoS: 3Citation - Scopus: 4A Facile Method for Boosting the Graphitic Carbon Nitride's Photocatalytic Activity Based on 0d/2d S-Scheme Heterojunction Nanocomposite Architecture(Elsevier, 2024) Kartal, Uğur; Kahraman, Zeynep; Genç, Aziz; Alp, Emre; 03.09. Department of Materials Science and Engineering; 04.04. Department of Photonics; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyGraphitic carbon nitride (g-C 3 N 4 ) has received significant interest as a metal -free photocatalyst. The S -scheme photocatalytic system has great potential to improve the charge separation in semiconductor photocatalysts. In this study, we have fabricated non-toxic and low-cost photocatalytic nanocomposites of 0D/2D S -scheme heterojunction composed of iron oxide and graphitic carbon nitride by a facile method. The developed facile method provides a sustainable way with a high atom economy to further enhance the photocatalytic performance of exfoliated g-C 3 N 4 . The 0D -iron oxide/2D-C 3 N 4 exhibited nearly 10 times better than bulk g-C 3 N 4 and almost 60 % better than exfoliated g-C 3 N 4 under simulated solar light irradiation. The experimental results demonstrated that the effective charge -carrier mechanism led to an improved generation of reactive oxygen species (ROSs), resulting in an impressive photocatalytic performance. A serial photocatalytic test was also conducted to understand photocatalytic reaction mechanisms with various scavengers.Doctoral Thesis Synthesis, Properties and Applications of Tungsten Oxide Nanostructures(01. Izmir Institute of Technology, 2023) Genç, Aziz; Balcı, Sinan; Kahraman, Zeynep; Balcı, Sinan; Genç, Aziz; 04.04. Department of Photonics; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn this study, tungsten oxide nanostructures, which are n-type semicon ductors with a band gap between 2.6-2.8, have been studied extensively. The hydrothermal method was used as the synthesis technique and the phases and morphologies were optimized in a stable and controllable manner. Firstly, sto ichiometric tungsten oxide nanowires with certain ratios were synthesized, and then cobalt doping was made using this synthesis technique. Subsequently, sub-stoichiometric tungsten oxide nanowires, which have oxygen gaps and can show plasmonic properties due to the increased carrier density, were synthe sized, and tungsten oxides with a flower-like hierarchical structure with oxygen gaps were synthesized and grouped according to possible application areas. Accordingly, how oxygen vacancies and hierarchical structures affect pho tocatalysis applications have been examined and it has been seen that ub stoichiometric tungsten oxide works faster until it reaches a certain saturation than stoichiometric tungsten oxide. According to this study, how the system can be manipulated by adding low pH to the system and hydrogen peroxide as an electron acceptor, respectively. It has been observed that it can be done. Hierarchical tunsten oxide has been found to be an ideal catalyst that can work quickly in photocatalysis studies due to its hierarchical structure, which has oxygen vacancies and can absorb light well. Additionally, tungsten oxide attracts attention as a material used in su percapacitor applications. Supercapacitors are long-lasting and fast-reacting electrochemical devices that can provide high power in energy storage and dis charge processes. The use of tungsten oxide in supercapacitor applications can be summarized as follows: when nanoparticles with large surface area are used as electrode material, they increase the interaction with the electrochemical surface and can increase the energy storage capacity. It shows high electro chemical activity as an electrode material. This feature contributes to the high performance of the supercapacitor. Tungsten oxide has a structure suitable for electron and ion conduction. This allows the supercapacitor to have fast charge/discharge capabilities and low internal resistance. Tungsten oxide can show stable performance during electrochemical cycles. This feature ensures the long life of the supercapacitor. In supercapacitor applications, in addition to these features, the electrical conductivity of the material can be increased by increasing the number of electrons carried in the material due to its oxygen gap. Accordingly, we investigated the comparative electrochemical properties and cycling stability of stoichiometric and sub-stoichiometric nanowires. Thanks to its electrochromic properties, the latest application has observed electrochromic changes of oxygen vacancies and cobalt dopingArticle Citation - WoS: 7Citation - Scopus: 8Stable janus TaSe2 single-layers via surface functionalization(Elsevier Ltd., 2021) Kahraman, Zeynep; Şahin, Hasan; Başkurt, Mehmet; Kahraman, Zeynep; Yağmurcukardeş, Nesli; Chaves, A.; Şahin, Hasan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of TechnologyFirst-principles calculations are performed in order to investigate the formation of Janus structures of single-layer TaSe2. The structural optimizations and phonon band dispersions reveal that the formation and stability of hydrogenated (HTaSe2), fluorinated (FTaSe2), and the one-side hydrogenated and one-side fluorinated (Janus-HTaSe2F) single-layers are feasible in terms of their phonon band dispersions. It is shown that bare metallic single-layer TaSe2 can be turned into a semiconductor as only one of its surface is functionalized while it remains as a metal via its two surfaces functionalization. In addition, the semiconducting nature of single-layers HTaSe2 and FTaSe2 and the metallic behavior of Janus TaSe2 are found to be robust under applied uniaxal strains. Further analysis on piezoelectric properties of the predicted single-layers reveal the enhanced in-plane and out-of-plane piezoelectricity via formed Janus-HTaSe2F. Our study indicates that single-layer TaSe2 is a suitable host material for surface functionalization via fluorination and hydrogenation which exhibit distinctive electronic and vibrational properties. © 2020 Elsevier B.V.Article Citation - WoS: 1Citation - Scopus: 1Phase-Dependent Optical, Photocatalytic and Capacitive Properties of Tungsten Oxide Nanowires(Royal Soc Chemistry, 2025) Genç, Aziz; Kahraman, Zeynep; Buldu-Akturk, Merve; Tan, Metin; Alp, Emre; Erdem, Emre; Genc, Aziz; 03.09. Department of Materials Science and Engineering; 04.04. Department of Photonics; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyTransition metal oxides hold great promise across a wide range of applications due to favorable properties such as high abundance, low toxicity, and excellent stability. Nanoengineering approaches are essential for controlling the structural, optical, and electronic properties of these materials, enabling the achievement of desired characteristics in a cost-effective and environmentally friendly manner. In this study, we synthesize stoichiometric (WO3) and sub-stoichiometric (WO3-x) tungsten oxide nanowires by controlling their phases and morphologies through the hydrothermal method. This approach allows us to systematically investigate the effects of different phases and oxygen vacancies on the optical properties, as well as on photocatalytic and supercapacitance applications. We use the photodegradation of RhB as a benchmark for photocatalytic activity under various experimental conditions, revealing that oxygen vacancies significantly influence photocatalytic behavior. For example, WO3-x nanowires adsorb/degrade a substantial amount of RhB within short durations under ambient conditions, where WO3 nanowires are mostly inactive. The addition of H2O2 enhances the photocatalytic performance of WO3 nanowires over 30 minutes, with even better results under low pH conditions with H2O2. This study also explores the phase-dependent electrochemical properties of WO3 and WO3-x nanowires, providing insights into their potential for improved supercapacitor performance by leveraging their complementary properties in symmetric and asymmetric configurations. WO3-x, with a higher density of oxygen vacancies and thinner structure, offers enhanced conductivity and increased active sites for charge storage, resulting in superior specific capacitance and charge retention.Article Citation - WoS: 5Citation - Scopus: 5Functionalization of Single-Layer Tas2 and Formation of Ultrathin Janus Structures(Cambridge University Press, 2020) Kahraman, Zeynep; Kahraman, Zeynep; Yağmurcukardeş, Mehmet; Yağmurcukardeş, Mehmet; Şahin, Hasan; Şahin, Hasan; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of TechnologyAb initio calculations are performed to investigate the structural, vibrational, electronic, and piezoelectric properties of functionalized single layers of TaS2. We find that single-layer TaS2 is a suitable host material for functionalization via fluorination and hydrogenation. The one-side fluorinated (FTaS2) and hydrogenated (HTaS2) single layers display indirect gap semiconducting behavior in contrast to bare metallic TaS2. On the other hand, it is shown that as both surfaces of TaS2 are saturated anti-symmetrically, the formed Janus structure is a dynamically stable metallic single layer. In addition, it is revealed that out-of-plane piezoelectricity is created in all anti-symmetric structures. Furthermore, the Janus-type single-layer has the highest specific heat capacity to which longitudinal and transverse acoustical phonon modes have contribution at low temperatures. Our findings indicate that single-layer TaS2 is suitable for functionalization via H and F atoms that the formed, anti-symmetric structures display distinctive electronic, vibrational, and piezoelectric properties.Article Citation - WoS: 93Citation - Scopus: 95Single-Layer Janus-Type Platinum Dichalcogenides and Their Heterostructures(American Chemical Society, 2019) Kahraman, Zeynep; Kandemir, Ali; Yağmurcukardeş, Mehmet; Şahin, Hasan; Şahin, Hasan; Kahraman, Zeynep; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of TechnologyUltrathin two-dimensional Janus-type platinum dichalcogenide crystals formed by two different atoms at opposite surfaces are investigated by performing state-of-the-art density functional theory calculations. First, it is shown that single-layer PtX2 structures (where X = S, Se, or Te) crystallize into the dynamically stable IT phase and are indirect band gap semiconductors. It is also found that the substitutional chalcogen doping in all PtX2 structures is favorable via replacement of surface atoms with a smaller chalcogen atom, and such a process leads to the formation of Janus-type platinum dichalcogenides (XPtY, where X and Y stand for S, Se, or Te) which are novel single-layer crystals. While all Janus structures are indirect band gap semiconductors as their binary analogues, their Raman spectra show distinctive features that stem from the broken out-of-plane symmetry. In addition, it is revealed that the construction of Janus crystals enhances the piezoelectric constants of PtX2 crystals significantly both in the in plane and in the out-of-plane directions. Moreover, it is shown that vertically stacked van der Waals heterostructures of binary and ternary (Janus) platinum dichalcogenides offer a wide range of electronic features by forming bilayer heterojunctions of type-I, type-II, and type-III, respectively. Our findings reveal that Janus-type ultrathin platinum dichalcogenide crystals are quite promising materials for optoelectronic device applications.Master Thesis Functionalization and Thickness Dependent Properties of Single Layer Dichalcogenides(Izmir Institute of Technology, 2019) Kahraman, Zeynep; Akdoğan, Yaşar; Kahraman, Zeynep; Şahin, Hasan; Şahin, Hasan; Akdoğan, Yaşar; 03.09. Department of Materials Science and Engineering; 04.04. Department of Photonics; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyAfter successful isolation of graphene in 2004, it was found that the layered materials showed different properties when diluted to the monolayer. The layer dependent structural, electronic and vibrational properties of the 1T phase of two dimensional (2D) platinum diselenide are investigated by means of state-of-the-art first-principles calculations. In addition ultra-thin two-dimensional Janus type platinum dichalcogenide crystals formed by two different atoms at opposite surfaces are investigated by performing state-of-the-art density functional theory calculations. While all Janus structures are indirect band gap semiconductors as their binary analogs, their Raman spectra show distinctive features that stem from broken out-of-plane symmetry. Moreover, it was shown that vertically stacked van der Waals heterostructures of binary and ternary (Janus) platinum dichalcogenides offer wide-range electronic features by forming bilayer heterojunctions of type-I, type-II and type-III. On the other hands, Ab initio calculations are performed in order to investigate the structural, vibrational, electronic, and piezoelectric properties of both bare TaS2 and its functionalized structures. Furthermore, the elastic and piezoelectric properties of TaS2 and its derivatives are analyzed. It is revealed that the in-plane piezoelectricity of TaS2 can be enhanced via one-surface fluorination while an additional degree of freedom for the piezoelectricity can be added in all Janus structures due to the broken out-of-plane symmetry. This thesis provides some important results understanding of thickness and functionalization dependent mechanics, vibrational, electronic properties of 2D materials.