Master Degree / Yüksek Lisans Tezleri

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Author: search.filters.author.Yalçın, Şerife HanımSubject: search.filters.subject.Laser-induced breakdown spectroscopy

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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
    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
    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.