Master Degree / Yüksek Lisans Tezleri

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Publisher: search.filters.publisher.01. Izmir Institute of TechnologySubject: search.filters.subject.2D materials

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  • Master Thesis
    Utilization of Graphene and Mos2 for Volatile Organic Compound Sensor Applications
    (01. Izmir Institute of Technology, 2023) Şahin, Hasan; Büyükçakır, Onur; Büyükçakır, Onur; Şahin, Hasan; 04.04. Department of Photonics; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    The novel 2D materials such as graphene and transition-metal dichalcogenides have already shown impressive volatile organic compound (VOC) gas monitoring performances as in sensitivity, limit of detection and response time. This thesis discusses the experimental-theoretical examination of optical, electronic and morphological properties of novel 2D materials and their utilization in VOC gas sensor field, by means of several characterization techniques and density functional theory (DFT). Aside from the basic familiarization with the experimental and theoretical methodology in Chapter 2, examination of the functionalization of exfoliated MoS2 using DDT (1-Dodecanethiol) in Chapter 3, which eventually led to a research paper. The DDT treatment is incorporated into the NMP (N-methyl pyrrolidone) exfoliation procedure, resulting in successful functionalization as confirmed by optical, morphological, and theoretical analysis. Raman spectroscopy showed the formation of graphitic species on MoS2 sheets, with decreased sulfur-vacant sites as the DDT ratio increased. STEM and AFM data confirmed the presence of graphitic quantum dots (GQDs) on MoS2 nanosheets, while PL intensities demonstrated significant improvements in photoluminescent properties. This study enhances our understanding of surface and edge chemistry in exfoliated MoS2 and expands the possibilities for broader applications of MoS2 and GQD particles. Moreover, the attention was drawn to the investigation of the contrasting responses of graphene gas sensors fabricated using different synthesis methods, in the submitted paper explained in Chapter 4. Exfoliated graphene sensors decrease in current when exposed to methanol, while CVD graphene sensors increase in current. The differences in edge site population and electrical properties contribute to these responses. The study provided theoretical and experimental findings for an understanding of the reasons behind the inverse sensor responses of CVD and exfoliated graphene on an atomic scale.
  • Master Thesis
    Investigation of Electronic, Vibrational, Mechanic and Chemicalproperties of 2d-Dlhc Cui Crystal
    (01. Izmir Institute of Technology, 2023) Demirok, Ali Cem; Şahin, Hasan; Büyükçakır, Onur; Büyükçakır, Onur; Şahin, Hasan; 04.04. Department of Photonics; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    The branch of material science and nanotechnology has recently seen the emergence of a remarkable class of materials known as 2D materials. These materials have unusual features and behaviours because of their special two-dimensional structure that separates them apart from bulk materials. One of the characteristics of 2D materials are related to their capacity to handle large mechanical deformation without fracture. Since the discovery of graphene, researchers have discovered and created an extensive range of additional 2D materials with a variety of chemical compositions and topologies. These materials can be used for energy storage, sensing, catalysis and biomedical applications. In this thesis, electronic, vibrational, mechanic and chemical properties of singlelayer CuI were investigated by using density functional theory (DFT) based first-principles calculations. It is shown that the CuI structure crystallizes in a hexagonal lattice by energy and geometry optimizations. The vibrational properties of the material were examined by phonon and Raman calculations and the structure found to be dynamically stable and there were four Raman active modes. The electronic band dispersions and corresponding density of states showed that the single-layer CuI crystal has semiconductor nature with direct band gap. Strain calculations were performed to examine the mechanical strength of the CuI crystal. Effect of biaxial strain on the electronic band structure of CuI crystal was investigated in the range of 5% and the direct band gap behaviour did not change. Biaxial and uniaxial strain calculations have shown that it is resistant to high stresses.