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Öğe Cytotoxic effect of silica nanoparticles on human retinal pigment epithelial cells(Academic Press Inc Elsevier Science, 2023) Kaynar, Ayse Humeyra; Comelekoglu, Ulku; Kibar, Deniz; Yildirim, Metin; Yildirimcan, Saadet; Yilmaz, Sakir Necat; Erat, SelmaIn recent years, the use of nanotechnology-based methods has become widespread in the treatment of ocular diseases. Silica nanoparticles (SiO2 NPs) are most common used NPs in medical field due to their physicochemical properties. SiO2 NPs can easily cross biological membranes and interact with basic biological structures, causing structural and functional changes in cells. In this study, it was aimed to investigate the dose dependent effect of SiO2 NPs on retinal pigment epithelium (RPE) in vitro using electrobiophysical, biochemical and histological methods. A commercially purchased human RPE (hARPE-19) cell line was used in this study. Cells were divided into four groups as control, 50 mg/mL SiO2, 100 mg/mL SiO2 and 150 mg/mL SiO2 groups. Cell index, apoptotic activity, cell cycle and oxidative stress markers were measured in all groups. Findings in the present study showed that SiO2 nanoparticles reduced cell proliferation, increased oxidative stress, apoptosis and arrest in the G0/G1 phase of the cell cycle as dose dependent manner in ARPE-19 cells. In conclusion, SiO2 exposure can induce cytotoxic effects in RPE cell line. The results of this study provide clues that exposure to SiO2 nanoparticles may impair visual function and reduce quality of life. However, further studies are needed in this regard.& COPY; 2023 Elsevier Inc. All rights reserved.Öğe Solution-Processable Growth and Characterization of Dandelion-like ZnO:B Microflower Structures(Mdpi, 2022) Erat, Selma; Braun, Artur; Cetinkaya, Samed; Yildirimcan, Saadet; Kasapoglu, Ahmet Emre; Gur, Emre; Harputlu, ErsanIntrinsic and dandelion-like microflower nano-rod structures of boron-doped ZnO thin films were synthesized with an ecofriendly and cost-effective chemical bath deposition technique from an aqueous solution of zinc nitrate hexahdyrate [Zn(NO3)(2).6H(2)O] as a precursor solution and boric acid as a doping solution. The boron concentrations were 0.1, 0.3, 0.5, 1.0, 3.0, 5.0, and 7.0 by volume. Scanning electron micrographs showed that doping with boron appears to hinder the vertical alignment of crystallites. Additionally, independent hexagonal nano-rod structures were observed to coalesce together to form dandelion-like structures on the film's surface. The atomic ratio of the elements was determined via the X-ray photoemission spectrum technique. There were no substantial changes in the vibration structure of the film upon doping in terms of the Raman spectra. The optical band gap of ZnO (3.28 eV) decreased with B doping. The band gap of the ZnO:B film varied between 3.18 and 3.22 eV. The activation energy of the ZnO was calculated as 0.051 eV, whereas that of the ZnO:B film containing 1.0% B was calculated as 0.013 eV at low temperatures (273-348 K), versus 0.072 eV and 0.183 eV at high temperatures (348-523 K), respectively. Consequently, it can be interpreted that the 1% B-doped ZnO, which has the lowest activation energy at both low and high temperatures, may find some application areas such as in sensors for gases and in solar cells.Öğe Study on crystallographic and electronic structure of micrometre-scale ZnO and ZnO:B rods via X-ray absorption fine-structure spectroscopy(Int Union Crystallography, 2021) Erat, Selma; Ozkendir, Osman Murat; Yildirimcan, Saadet; Gunaydin, Selen; Harfouche, Messaoud; Demir, Bunyamin; Braun, ArturX-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectra were recorded to investigate the electronic structure and local crystal structure of ZnO and ZnO:B powders produced via hydrothermal synthesis. ZnO and ZnO:B grow as micrometre-scale rods with hexagonal shape, as confirmed by scanning electron microscopy micrographs. The number of broken ZnO:B rods increases with increasing B concentration, as observed in the images, due to B atoms locating in between the Zn and O atoms which weakens and/or breaks the Zn-O bonds. However, no disorder within the crystallographic structure of ZnO upon B doping is observed from X-ray diffraction results, which were supported by EXAFS results. To determine the atomic locations of boron atoms in the crystal structure and their influence on the zinc atoms, EXAFS data were fitted with calculated spectra using the crystal structure parameters obtained from the crystallographic analysis of the samples. EXAFS data fitting and complementary k-weight analysis revealed the positions of the B atoms - their positions were determined to be in between the Zn and O atoms.Öğe Turkey's energy transition from fossil-based to renewable up to 2030: milestones, challenges and opportunities(Springer, 2021) Erat, Selma; Telli, Azime; Ozkendir, Osman Murat; Demir, BunyaminThe energy demand of Turkey has been increasing along with increasing life standards and population and growing economy particularly since the 1980s. Most of the oil and natural gas have been imported by Turkey due to insufficient domestic reserves. Nowadays, the population of Turkey is about 83 million. The Turkish economy grew by 3% in the last 30 years and became the 18th largest economy in the world and the 6th one in Europe. Turkey aims to use energy resources efficiently, effectively and eco-friendly. Concerning climate change, Turkey signed the Paris Agreement and pledged a 21% reduction in greenhouse gas emission by the year 2030. While the energy world is in an inevitable transition to green energy, Turkey, which has a huge potential to achieve 100% energy transition in renewable energy, is still the 17th largest country in the utilization of renewable energy. Although Turkey has already reached the 2023 targets concerning the utilization of renewable energy, there is a long path to reach the target of reducing greenhouse gas emissions. The 2030 targets of Turkey are to increase the installed solar capacity up to 38,000 MW, wind capacity up to 25,000 MW and geothermal capacity up to 4000 MW. Turkey officially announced that the utilization of renewable energy will be 32%. However, taking into account the potential and success in 2023 targets, it was seen that 2030 targets should be revised and increased from 32% to at least 50%. This study presents the milestones, challenges and opportunities of Turkey on the way of the energy transition toward renewable up to 2030. The energy goals of Turkey which are to use domestic energy resources efficiently and effectively were discussed and presented in detail. The aim of Turkey is to reduce the energy import dependency (76%). The installed energy capacities, energy consumption and projections, energy security and energy policies of Turkey were also presented. [GRAPHICS] .
