Master Degree / Yüksek Lisans Tezleri

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Author: search.filters.author.Yalçın, Şerife HanımHas files: Yes

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  • Master Thesis
    Determination of Cadmium Bound To Whey Proteins by Laser-Induced Breakdown Spectroscopy at Low Pressures
    (2023) Yalçın, Şerife; Yaman, İlayda; Yalçın, Şerife Hanım; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this thesis study, a dried-droplet LIBS methodology at reduced pressures for determining cadmium in aqueous media and in biological samples has been developed. With the advantage of the signal enhancement effect at reduced pressures, the optimum pressure for Cd detection was determined. Results were justified with the plasma images taken at different pressures. 100 mbar pressure was found as the optimum for most emission lines of Cd. To find the most suitable substrate onto which analyte droplets will be loaded, silicon wafer-based substrates of different coating types and coating thicknesses were studied. Among them, the c-Si substrate was found to show the highest signal enhancement for Cd detection. The performance of the methodology for quantitative analysis of Cd was shown by standard solutions and certified reference water samples. Calibration curves were constructed, and performance characteristics (limit of detection, accuracy, precision) were evaluated. Detection limits in absolute amounts of 6.8 pg and 1.05 pg were obtained at atmospheric and 100 mbar pressures, respectively. The application studies involve the determination of Cd bound to whey proteins. For this purpose, standard protein (BSA) and whey protein extracted from the milk were incubated in standard Cd solutions for several hours and filtered through cut-off filters via centrifugation. The unreacted cadmium in the filtrate and Cd-bound protein in fraction were analyzed separately. It has been shown that dried-droplet LIBS at reduced pressures is a suitable methodology for identifying and determining Cd and Cd bound to proteins with a picogram amount of detection capability.
  • Master Thesis
    Colloidal Plexcitonic Nanocrystals
    (Izmir Institute of Technology, 2022) Yalçın, Şerife; Yalçın, Şerife Hanım; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Noble metal nanocrystals, especially gold and silver, which have attracted a great deal of attention due to the supporting of surface plasmon polaritons (SPPs), have been extensively investigated and studied. With recent developments in colloid chemistry, synthesis of noble metal nanocrystals with tunable optical properties in the visible region of the electromagnetic spectrum has become easier. Until now, noble metal nanocrystals (NPs) synthesized by using various synthetic methods, have a variety of shapes, such as bipyramid, rod, disk, prism, and ring, etc. In the strong coupling regime, SPPs supported by metal nanocrystals interact strongly with excitons of organic dyes, semiconducting quantum dots (carbon or perovskite quantum dots) to generate a new hybrid optical mode called plexciton (plasmon-exciton). Plexcitonic nanocrystals have received interest owing to their ease of synthesis, scalability, and ability to provide sub-wavelength confinement of incident light and offer promising applications. Plasmon–exciton interaction at nanoscale dimension can be improved by generating new plexcitonic nanoparticles with tunable optical properties, which may be utilized in critical applications such as nanolasers, sensors, nano-optics, solar cells, and light emitting diodes. Therefore, there has been a tremendous amount of interest in the synthesis of new plexcitonic nanocrystals having excellent optical and chemical properties. The main goal of this thesis is to synthesize new plexcitonic nanoparticles with tunable optical properties in the visible spectrum: (i) synthesis of different shaped colloidal monometallic and bimetallic nanocrystals, (ii) synthesis of new colloidal plexcitonic nanocrystals, (iii) synthesis of carbon quantum dots (CDs), (iv) coupling of excitons of CDs and SPPs on the silver thin film.
  • Master Thesis
    Investigating the Effect of Metallic Nanoparticles Presence on Signal Intensity for Dried-Droplet Analysis by Laser-Induced Plasma Spectroscopy
    (01. Izmir Institute of Technology, 2021) Tetik Karabıyık, Özge; Yalçın, Şerife; Yalçın, Şerife Hanım; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    While solid sample analysis by LIBS is more easy and straightforward, liquid analysis is more troubling. One of the studies aimed at removing the problems in liquid analysis is the Nanoparticle Enhanced LIBS technique. This study aims to investigate the effect of the presence of Ag nanoparticles of different shape and absorption wavelengths on the signal strength of heavy metals Pb and Cr. For that purpose, spherical, prism, and disc-shaped silver nanoparticles with an absorption wavelength in the range of 394-761 nm were used. Among all types of NPs with different sizes and shapes, silver nanoparticles with an absorption maximum at 535 nm were found to enhance LIBS signal intensity of Pb element at 405.8 nm 5-6 times, and that of Cr at 428.9 nm 3-3.5 times. Under optimized conditions, a LOD value of 1,16 and 0.69 ppb were obtained for Pb and Cr, respectively. The applicability of the system for the determination of Pb and Cr in aqueous environments has also been tested on reference water samples. The silver nanoparticle with an maximum absorbance wavelength of 535 nm shows the most improvement in signal. The wavelength of the laser used is very close to the absorbance wavelength of the silver nanoparticle, effectively overlapping it. Thanks to the transmitted laser light, plasmons are formed on the nanoparticle surface. These formed surface plasmons interact with the laser electromagnetic field, resulting in an increase in the signal.
  • Master Thesis
    Investigation of the Silicon Nitride Coating Thickness on Silicon Wafer Substrates for Enhanced Sensitivity in Dried Nano-Droplet Analysis by Laser Induced Breakdown Spectroscopy
    (01. Izmir Institute of Technology, 2021) Durkan Kaplan, Dilara; Yalçın, Şerife; Yalçın, Şerife Hanım; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Laser Induced Breakdown Spectroscopy (LIBS) is an atomic emission spectroscopic technique that uses laser beam to generate plasma for detection. Also, LIBS is a fast and non-destructive methodology with the advantage of no sample preparation requirement and easy usage. Surface Enhanced LIBS (SENLIBS) is recently developed version of the LIBS technique that uses some kinds of surface materials for supporting liquids and for the enhancement of LIBS signal intensity. It has been previously shown that silicon nitride coated silicon wafer substrates have some properties to enhance LIBS signal of several metal solutions by dried-droplet analysis methodology. Within the scope of this thesis study, silicon wafers coated with silicon nitride of several thicknesses were utilized for investigating the effect of coating thickness on sensitivity of the LIBS technique for liquids analysis. Heavy metals above a certain concentration have a significant negative impact on the environment and human health. In this context, the chromium, copper and lead metal liquid samples was loaded on 75 nm, 300 nm, 450 nm and 1000 nm silicon nitride coated wafers and dried, then analyzed by LIBS. As a result of this study, it was seen that the 1000 nm coating increased the LIBS signal intensity at the highest degree. The LOD value of the chromium element was improved as 0.56 pg, the lead element as 0.7 pg, and the copper element as 0.42 pg with 1000 nm Si3N4 coated wafers.
  • Master Thesis
    Identification and Detection of Cis-Platin Binding Proteins by Laser Induced Breakdown Spectroscopy
    (Izmir Institute of Technology, 2015) Kaya, İbrahim; Yalçın, Şerife; Yalçın, Şerife Hanım; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this study, an all-optically designed laser plasma spectroscopic technique for rapid identification and detection of cisplatin-binding proteins on electrophoretic gel spots prior to molecular mass spectrometric analysis is demonstrated. For this purpose, human serum albumin, human apo transferrin and horse heart myoglobin standard proteins and protein extracts from HeLa cancer cells were subjected to; incubation with cis-platin solution for several hours. Then, non-reducing polyacrylamide gel electrophoretic separation was applied. Followed by the visualization of proteins in the gel by Coomassie Brilliant Blue staining technique protein spots on the gel were dried between two cellophane sheets and subjected to laser ablation by highly energetic laser pulses. In addition, prior to nr-SDS-PAGE separation cis-platin binding to standard proteins were monitored by ESI-MS with several measurements made in 24 hours of incubation time. Using a Nd:YAG laser at its second harmonic wavelength, 532nm, 10 Hz frequency and 10 ns pulse duration, a micro-plasma was created on dried gel spots. Resulting plasma emission light was collected with collection lenses and transferred to a spectrograph via fiber optic cable. An intensified charge coupled device (ICCD) detector enabled multielemental analysis of platinum binding protein samples. Platinum binding proteins were recognized from the prominent neutral emission line, Pt (I) at 273.3 nm, in a plasma formed by the focused laser pulses on the gel, just in the center or in the vicinity of the electrophoretic spot. Spectral emission intensity of Pt lines from LIBS data has been optimized with respect to laser energy and detector timing parameters. Optimization of LIBS experimental parameters have been studied on polyacrylamide gels soaked in cis-Pt solution for Pt signal. It has been shown that, LIBS is a suitable method for identifying Pt in proteins, in gel medium, with nanogram levels of detection capability. The technique was applied to HeLa (human cervical cancer cells) cells extract for the detection of Pt-binded HSA after standard addition of known amounts of protein.