Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, ChemistrySubject: search.filters.subject.Volatile organic compounds

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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
    Fabrication of Thin Layer Polymer-Based Biointerphase for Biosensing Application
    (İzmir Institute of Technology, 2016) Yücel, Müge; Yıldız, Ümit Hakan; Yıldız, Ümit Hakan; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    This study aims to fabricate polymer-carbon nanotube composite as a bioelectronic interface for sensing volatile organic compounds (VOCs) in exhaled breath. Sensor platform is made of two layers i) polymeric membranes and ii) conducting layer. Poly(vinylidene fluoride) (PVDF), polystyrene (PS), and poly(methyl methacrylate) (PMMA) are selected as model polymers that are processed by electrospinning to utilize polymeric membranes. Multi-walled carbon nanotubes (MWCNTs) are used to fabricate conducting layer on top of PVDF, PS, PMMA polymer membranes. Aqueous solution of well-dispersed MWCNTs are obtained by several purification and filtration steps and conductivity of working MWCNT solution is adjusted about 120 μS/cm for whole study. This solution is further used to impregnate PVDF, PS, PMMA membrane. The PVDF-MWCNT, PS-MWCNT and PMMA-MWCNT sensor platforms are tested by electrochemical station that recording electrical resistivity change by time. All sensors platforms, made of three polymeric membranes-MWCNT, are found to be a responsive upon applying the toluene and acetone vapor. The sensing mechanism is hypothesized as the adsorption of VOCs onto the conducting CNT layer blocking electron stream on CNT network and causing resistivity change. The sensitivity of PVDF-MWCNT sensing platform is exceedingly higher with respect to other two candidates due to solvent vapor- polymeric membrane interactions. This contribution changes sensor platform characteristics and make them quite sensitive to trace amount of VOCs. Acetone and toluene are detected from ppm to ppb range and reproducible responses are recorded. As a result, acetone and toluene, biomarkers of diabetes and lung cancer, can be differentiated with produced sensor.