Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Investigation of a Novel Personal Sampler Material for the Identification of Human Exposure To Semivolatile Organic Compounds(2024) Akmermer, Zülfikar; Demirtepe, Hale; Sofuoğlu, Sait CemilSVOCs are widespread indoors, where they occur at high levels. Humans spend most of their time indoors and are regularly exposed to these compounds. Various methods exist to assess human exposure to SVOCs. However, a novel personal sampler material, i.e. silicone wristband, has been used for the last decade. Due to its commencing use, the uptake capacity of silicone wristbands for SVOCs still needs to be discovered. This study aims to investigate the SVOC uptake rate and equilibrium partitioning coefficients of silicone wristbands. To achieve this aim, an analysis method for determining SVOCs in silicone wristbands was developed and validated with wristbands worn by academic personnel of IZTECH. The results showed that among polycyclic aromatic hydrocarbons (PAHs) acenaphthylene, among organophosphate esters (OPEs), tris (2-butoxyethyl) phosphate and among phthalate esters, di(2- ethylhexl) phthalate were found as the dominant SVOCs in silicone wristbands. Then, the uptake capacity of silicone wristbands for PAHs was investigated by deploying them in a school environment for 36 days, together with polyurethane foam passive air samplers. The uptake rates varied three orders of magnitude for compounds reaching equilibrium, i.e. acenaphthene, acenaphthylene, fluorene, phenanthrene, and anthracene (0.010 – 25.93 m3/day), while for fluoranthene, chrysene, and pyrene uptake rates were close to each other (0.17 – 0.50 m3/day). Furthermore, silicone wristband-air partitioning coefficients were in the range of 5.93 to 7.43 for acenaphthene, acenaphthylene, fluorene, phenanthrene, and anthracene. Lastly, daily and chronic toxic exposures and lifetime cancer risk for school children were assessed using PUF-PAS concentrations, and no significant risk was identified.Master Thesis Utilization of Graphene and Mos2 for Volatile Organic Compound Sensor Applications(01. Izmir Institute of Technology, 2023) Duran, Tuna; Büyükçakır, Onur; Şahin, HasanThe 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 HakanThis 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.Master Thesis Catalytic Surface Coatings for Household Ovens(Izmir Institute of Technology, 2016) İzer, Alaz; Şeker, Erol; Şeker, ErolThe emission of harmful volatile compounds, such as aldehydes, and also carbon monoxide could occur during cooking processes at home or industry due to the combustion and cracking of spilled vegetable oil on the walls of an oven. It is known that the by-products generated during cooking could affect human health and environment if they are properly vented or removed. To eliminate the health and environmental problems related to oven emission, self-cleaning catalytic materials coated walls for ovens seem to be viable alternative to the toxic and time consuming chemical cleaning solutions. In this project, a sol-gel method and also the dip coating technique was used to produce a catalytic material coated aluminum plates. Specifically, the calcination time and the temperature were studied to better understand the relationship between the textural/chemical properties of the catalyst coated metal plates and their catalytic activities. The studied calcination temperatures were 450°C, 500°C and 550°C whereas the calcination time were 10 min, 30 min and 60 min for each type of catalyst. Aluminum oxide supported nickel and also aluminum oxide - manganese oxide supported nickel catalysts were prepared as the catalyst that were used in coating. The catalytic activities of the catalyst coated plates were determined using canola oil as a function of reaction time which were 1h at 170°C and 200°C. The results have been shown that the most convenient calcination conditions for the canola oil combustion were 500°C for 30 minutes by using aluminum oxide – manganese oxide supported nickel catalyst.Master Thesis Monitoring and Assessment of Indoor Air Volatile Organic Compound Concentrations in Primary Schools(Izmir Institute of Technology, 2008) Aslan, Güler; Sofuoğlu, Sait CemilIndoor air quality (IAQ) is important mainly because, poor IAQ may cause variety of adverse health effects and people spend majority of their time indoors. One of the most susceptible groups to air pollution is considered as children. Children spend approximately six to eight hours a day in school buildings, therefore the indoor air quality of school buildings should be given utmost importance. Formaldehyde and volatile organic compounds (VOCs) have been receiving considerable interest in indoor air field studies because of their high emission rates from products used indoor environments. Thus, their concentrations have been measured in school buildings in many different countries.Indoor and outdoor air samples were collected from three primary schools in İzmir (School 1, School 2, and School 3). Sampling was performed in spring and winter terms. Active sampling was applied for VOCs and formaldehyde by using Tenax TA and DNPH silica gel sorbent tubes, respectively. VOCs were analyzed by using a thermal desorption - gas chromatography - mass spectrometry (TD-GC-MS) system.Formaldehyde analysis was performed by using an HPLC instrument.Benzene, toluene, ethyl benzene and xylenes, which have high toxicity, were detected at high concentrations. In addition, the indoor/outdoor (I/O) concentration ratios of VOCs were investigated. Mean Total VOC (TVOC) and formaldehyde concentrations were calculated for the three schools in winter and spring terms. TVOC and formaldehyde concentrations were 104 .g/m3 and 44.36 ./m3 in winter, and 66.42 .g/m3 and 43.73 .g/m3 in spring terms for School 1; and 50.86 .g/m3 and 30.78 .g/m3 in winter, and 32.1 .g/m3 and 35.82 .g/m3 in spring term for School 2, and 51.09 .g/m3 and 36.53 .g/m3 in spring term for School 3 primary schools, respectively. These concentration values are generally higher than or parallel to the values reported in the literature. The TVOC concentrations in kindergartens were higher than the concentrations in classrooms.