Browsing by Author "Zeyrek Ongun M."

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    Characterization of β-PVDF-based nanogenerators along with Fe2O3 NPs for piezoelectric energy harvesting
    (Springer, 2020) Zeyrek Ongun M.; Paralı L.; Oğuzlar S.; Pechousek J.
    β-phase polyvinylidene fluoride (PVDF) nanogenerators along with various concentrations (0.2, 0.4, 0.6, and 0.8 wt%) of iron oxide (Fe2O3) nanoparticles were produced using the electrospinning technique. The characterization of the free- and doped-nanogenerators was examined by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and 57Fe Mössbauer spectroscopy, dielectric measurements, and piezoelectric effect analysis. All the analyses demonstrated that the structural transition in the specimens at doping ratios are above the critical concentration of 0.4% by wt. of Fe2O3 NPs in PVDF, superparamagnetic behavior of the iron oxide particles in the composite. Utilization of the β-PVDF along with Fe2O3 NPs (0.4 wt%) exhibited higher piezoelectric properties with respect to the free form and the other additive concentrations. Considering the piezoelectric properties of the nanogenerator, the output voltage of the β-PVDF in the presence of the 0.4 wt% of Fe2O3 NPs reaches up to 1.39 V by increasing the peak amplitude to almost 50% while the undoped β-PVDF nanogenerator reveals almost to 0.93 V at the same impact frequency (6–7 Hz). © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
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    Improvement of optical properties of one-dimensional CaAl12O19:Mn4+ phosphor via Er3+- and Tb3+- doped bioactive glass powders
    (Elsevier B.V., 2021) Oguzlar S.; Zeyrek Ongun M.; Deliormanlı A.M.
    Until now, because of the being a candidate for the red-emitting material the CaAl12O19:Mn4+ phosphor (CAO:Mn) has been widely used especially in white light-emitting diodes (WLEDs). In this study, the emission-based luminescence properties of CaAl12O19:Mn4+ red phosphor synthesized via sol-gel method was studied in the absence and presence of Er3+- and Tb3+-doped 13–93 bioactive glass powders in ethyl cellulose (EC) matrix in detail. Upon the addition of un-doped and Er3+- and Tb3+- doped bioactive glass powders, the CAO:Mn phosphor resulted in 44%, 92% and 88% increase in the emission intensity, respectively. The luminescence and decay time characteristics of the synthesized phosphor were also investigated in terms of microsecond time scale. The proposed material may bring a new inside for the existing problems of the red phosphors regarding the brightness, colour correlation temperature and colour rendering index. © 2021 Elsevier B.V.
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    Effects of Eu3+, Gd3+ and Yb3+ substitution on the structural, photoluminescence, and decay properties of silicate-based bioactive glass powders
    (Springer Nature, 2022) Deliormanlı A.M.; Oguzlar S.; Zeyrek Ongun M.
    Bioactive glass (BG) powders containing europium (Eu3+), gadolinium (Gd3+) and ytterbium (Yb3+) were synthesized through sol–gel process. Effects of the related rare-earth ions on the structural, photoluminescence (PL), and decay characteristics were investigated. In vitro, acellular bioactivity of the synthesized powders was examined in simulated body fluid (SBF). Results revealed that all of the BG powders tested in the study showed PL emission under excitation at 374 nm. Among the rare earth dopants tested in the study, Eu3+-containing samples exhibited the strongest emission intensities and for all the glasses optimum dopant concentration was 3 wt% based on the luminescence properties. The synthesized BG have ability to convert to hydroxyapatite (HA) after immersion in SBF. However, more detailed studies with resolution techniques are needed to confirm these observations, that the BG containing Eu3+, Gd3+, and Yb3+ have the ability to form HA and can be used in biomedical applications. Graphical abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to The Materials Research Society.
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    Effect on Improving CO2 Sensor Properties: Combination of HPTS and γ-Fe2O3@ZnO Bioactive Glass
    (American Chemical Society, 2023) Oguzlar S.; Zeyrek Ongun M.; Deliormanlı A.M.
    8-Hydroxypyrene-1,3,6-trisulfonic acid (HPTS) dye, a fluorescent dye often used as a pH indicator, is embedded within the bioactive glass matrix and undergoes changes in its fluorescent properties when exposed to carbon dioxide (CO2). The aim of the current study is to investigate the use of bioactive glass (BG) particles containing γ-Fe2O3@ZnO to enhance the CO2 sensitivity of HPTS. X-ray diffraction, Fourier transform infrared, scanning electron microscopy, and photoluminescence spectroscopies were used to characterize the sol-gel synthesized powders. The sensing slides were prepared in the form of a thin film by immobilizing the fluorescent dye and γ-Fe2O3@ZnO-based additives into the poly(methyl methacrylate) matrix. The addition of γ-Fe2O3@ZnO nanoparticles with bioactive glass additives to the HPTS improves the performance characteristics of the sensor, including the linear response range, relative signal variation, and sensitivity. Meanwhile, the CO2 sensitivities were measured as 10.22, 7.73, 16.56, 17.82, 19.58, and 42.40 for the undoped form and M, M@ZnO, 5M@ZnO-BG, 10M@ZnO-BG, and 20M@ZnO-BG NP-doped forms of the HPTS-based thin films, respectively. The response and recovery times of the HPTS-based sensing slide along with 20M@ZnO-BG NPs have been measured as 44 and 276 s, respectively. The γ-Fe2O3/ZnO-containing BG particle-doped HPTS composites can be used as a promising sensor agent in the detection of CO2 gas in various fields such as environmental monitoring, medical diagnostics, and industrial processes. © 2023 The Authors. Published by American Chemical Society.
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    Modulation of optical oxygen sensitivity of H2(TPP) by using Eu3+, Gd3+ and Yb3+ ions doped silicate-based bioactive glass powders immersed in simulated body fluid
    (Elsevier GmbH, 2023) Oğuzlar S.; Zeyrek Ongun M.; Deliormanlı A.M.
    Improving the performance of optical oxygen sensors can be accomplished by adding additives to the composition comprising an oxygen-sensitive probe encapsulated in a polymeric matrix. In this study, to advance the oxygen sensing ability, free meso-tetraphenyl porphyrin (H2(TPP)) was chosen as a luminophore. The sol-gel based 13–93 bioactive glass powders (BG) co-doped with ytterbium (Yb3+), gadolinium (Gd3+), and europium (Eu3+) and immersed in simulated body fluids (SBF) were also used as additives. After being immersed in SBF, bioactive glasses containing Eu3+, Gd3+, and Yb3+ were found to be able to convert hydroxyapatite corresponding to in vitro bioactivity tests. The optimum additive concentration for all glass samples is 3 wt%, based on photoluminescence-based properties. The luminescence dye was incorporated into poly(trimethylsilylpropyne) [poly(TMSP)] matrices in the form of a thin film along with bioactive glass additives to improve oxygen sensitivity. Emission-based intensity values of all porphyrin complexes have been followed as a signal drop during oxygen sensing measurements. The H2(TPP) along with the additive of BG:Eu3+ showed a 6.88 fold of I0/I ratio compared to the undoped and Gd3+ and Yb3+-doped BG forms in terms of the relative signal change. Large Stoke's shift (Ksv) values, high luminescence abilities, and linear spectral response make them promising candidates as oxygen sensing agents. It was concluded that prepared bioactive glass powders are suitable to use as additive materials for improving the oxygen sensitivity of meso-tetraphenyl porphyrin dye. © 2023 Elsevier GmbH