Master Degree / Yüksek Lisans Tezleri

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Author: search.filters.author.Yalçın, Şerife HanımPublisher: search.filters.publisher.01. Izmir Institute of Technology

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  • 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.