Phd Degree / Doktora
Permanent URI for this collectionhttps://hdl.handle.net/11147/2869
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Doctoral Thesis Development of Plasmonic Nanostructures for Photothermal Therapy of Prostate and Breast Cancer(Izmir Institute of Technology, 2019) Tomak, Aysel; Bulmuş, Volga; Şahin, HasanThe aim of this thesis is to synthesize gold nanorods (AuNRs) and lipid-stabilized nanobubbles containing AuNRs and investigate the potential of these plasmonic nanostructures as photothermal therapy agents for breast and prostate cancer through in vitro cell culture experiments. For this aim, firstly, AuNRs were synthesized at varying aspect ratios (ARs) and characterized via several techniques including UV-Vis/NIR spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), inductively coupled plasma-mass spectroscopy (ICP-MS), electrophoretic light scattering (ELS) and X-ray photoelectron spectroscopy (XPS). The surface of AuNRs was modified with a biocompatible polymer, poly(ethylene glycol) (PEG), via ligand exchange method. Cytotoxicity, cell uptake and photothermal effects of AuNRs were investigated via in vitro cell culture experiments using human prostate cancer (DU 145) and epithelial (RWPE-1), breast cancer (MCF7) and epithelial (MCF 10A) cell lines. It was concluded that AuNRs (AR=4.0) were superior than AuNRs (AR=7.0) in terms of cell viability and photothermal effect. Separately, a non-commercial antibody (Ab) targeting a specific sialic acid derivative on the plasma membrane of DU 145 and MCF7 cancer cells was conjugated to AuNRs. Conjugations were characterized with the same techniques and investigated via in vitro cytotoxicity and cell uptake experiments. The Ab-conjugated AuNRs displayed the capability of selective targeting prostate cancer cells. Additionally, lipid-stabilized AuNRs and lipid-stabilized nanobubbles containing AuNRs (AuNBs) were synthesized for the first time and characterized using UV-Vis/NIR spectroscopy, SEM, ICP-MS and ELS techniques. Lipid-stabilized AuNRs were successfully synthesized using varying lipid mixtures instead of cationic, toxic surfactant. Separately, AuNBs were synthesized by combining PEG modified AuNRs with DPPC: DSPE-PEG lipid film under sonication and gas stream. AuNBs showed the same or significantly lower toxicity depending on the cell types and the same photothermal effect with respect to AuNRs (AR=4.0) upon irradiation under laser at 808 nm.Doctoral Thesis Optical and Electronic Properties of Atomically Thin Layered Materials: First Principles Calculations(Izmir Institute of Technology, 2019) İyikanat, Fadıl; Senger, Ramazan Tuğrul; Şahin, HasanThe extraordinary interest in two-dimensional (2D) materials is increasing day by day. Thanks to advances in the experimental techniques, monolayer form of another material is synthesized every day with features not seen in the bulk form. Ab initio methods provide useful tools for characterizing and functionalizing the various properties of these materials. The results obtained through first principles quantum-mechanical calculations can help to predict and understand the experimental data, such as the position and source of the spectroscopic peaks in the Raman or optical absorption spectra. The aim of this thesis is to predict and functionalize the optical and electronic properties of atomically thin layered materials using density functional theory and approaches beyond. Within the scope of this thesis, possible technological applications of various 2D materials ranging from perovskite crystals to transition metal dichalcogenites are investigated by using several functionalization methods. In order to accurately predict the optical properties of these materials, it is very important to use approaches that take into account the many-body effects. Recent studies have shown that many-body perturbation theory in the form of GW approximation is highly reliable to calculate the quasiparticle properties of materials. By solving the Bethe Salpeter equation on top of GW calculation, the quasiparticle energies and excitonic properties, which have dominant effect in the optical properties of ultra-thin materials are examined in detail.Doctoral Thesis Optical Properties of Ultra-Thin Materials(Izmir Institute of Technology, 2017) Bacaksız, Cihan; Senger, Ramazan Tuğrul; Şahin, HasanMany years of research effort, after the synthesis of graphene, have revealed that atomically thin two-dimensional materials have mechanical, electronic, and optical properties which are different from their bulk counterparts. Thus, the interest in twodimensional materials is growing which is also fueled by fast advances in synthesis and measurement techniques. In this regard, the theoretical and computational simulations provide physical insight to the experiments in this new and demanded field; a tool for characterizing these materials; and also a reliable prediction approach to possible stable structures. The density functional theory (DFT) is one of the most powerful and commonly used methods for such theoretical investigations. The DFT-based computational determination of optical properties, as compared to other usual DFT-based calculations, is in its early stage due to high computational resource requirements and lack of established documentation. Therefore, the present thesis aims at giving the methodology and computing the optical properties of ultra-thin materials by using DFT and beyond-DFT approaches. More precisely, the thesis provides an overview of light matter interaction; basics of DFT, GW approximation for many-body effects, Bethe-Salpeter equation for excitonic effects; and several applications of these on atomically-thin systems.Doctoral Thesis Electronic, Magnetic, and Mechanical Properties of Novel Two Dimensional Monolayer Materials(Izmir Institute of Technology, 2017) Yağmurcukardeş, Mehmet; Senger, Ramazan Tuğrul; Şahin, HasanLayered materials exhibit different properties when they are thinned down to a few monolayers. Following the successful isolation of graphene in 2004, there has been a rapid increase in the number of studies focusing on other novel two dimensional (2D) materials such as hexagonal Boron Nitride (BN), transition metal dichalcogenides (TMDs), post transition metal chalcogenides (PTMCs), and in-plane anisotropic monolayers (Redichalcogenides and blackphosphorus). In addition to their electronic, optical, and magnetic properties, mechanical properties of 2D materials are of fundamental importance. Measurements of elastic constants of 2D materials are still challenging. Therefore, theoretical investigation of the mechanical properties is particularly important. Moreover, investigation of Raman spectra of these materials requires a through understanding of their vibrational properties. In these regards, we investigate the electronic, magnetic, and mechanical properties of some novel monolayer 2D materials (such as, auxetic pentagonal monolayers, flexible monolayers of holey graphene crystals, ultra-flexible monolayers of PTMCs, and in-plane anisotropic monolayers of ReS2 and blackphosphorus) by means of first-principles calculations based on density functional theory (DFT). In addition, tuning electronic properties of a van der Waals heterobilayer structure composed of monolayers of Mg(OH)2 and WS2 upon an external out-of-plane electric field is studied. The effect of biaxial strain on the vibrational properties of novel 2D materials is also studied through their off-resonant Raman activities. Our findings will be useful to clarify several issues related to the experiments of novel 2D materials.