Browsing by Author "Ongun, MZ"

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    Effect on Improving CO2 Sensor Properties: Combination of HPTS and γ-Fe2O3@ZnO Bioactive Glass
    Oguzlar, S; Ongun, MZ; Deliormanli, AM
    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 gamma-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 gamma-Fe2O3@ZnO-based additives into the poly(methyl methacrylate) matrix. The addition of gamma-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 gamma-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.
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    Characterization ofβ-PVDF-based nanogenerators along with Fe2O3NPs for piezoelectric energy harvesting
    Ongun, MZ; Parali, L; Oguzlar, S; Pechousek, J
    beta-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(57)Fe Mossbauer 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 Fe(2)O(3)NPs in PVDF, superparamagnetic behavior of the iron oxide particles in the composite. Utilization of the beta-PVDF along with Fe(2)O(3)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 beta-PVDF in the presence of the 0.4 wt% of Fe(2)O(3)NPs reaches up to 1.39 V by increasing the peak amplitude to almost 50% while the undoped beta-PVDF nanogenerator reveals almost to 0.93 V at the same impact frequency (6-7 Hz).
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    Investigation of the structural, photoluminescence properties, bioactivity and 5-fluorouracil delivery behavior of Dy3+and Dy:Eu3+-doped bioactive glasses
    Deliormanli, AM; Rahman, B; Oguzlar, S; Ongun, MZ
    Nowadays fluorescent biomaterials gained crucial interest in the biomedical field. Here we report the solgel synthesis and characterization of Dy3+ and Dy:Eu3+ co-doped bioactive glass powders. Structural, morphological, and photoluminescence (PL) characteristics of the prepared powders were investigated in detail. Additionally, in vitro hydroxyapatite forming ability and the anticancer drug (5-Fluorouracil) release behavior were investigated with respect to time. The influence of drug loading and delivery on the PL properties was monitored. Results showed that the highest PL intensity was obtained for the 5%Dy:Eu3+ codoped glass samples. The incorporation of rare-earth ions into the glass network did not cause a significant difference in the structural properties. In vitro conversion experiments, performed in simulated body fluid, indicated that the incorporation of Dy3+ to the glass network enhanced the hydroxyapatite deposition however Dy:Eu3+ co-doping slightly decreased the bioactivity. Drug-loaded bioactive glass powders exhibited sustained drug release behavior to the phosphate buffered saline (PBS) medium. An increase was obtained in the fluorescence intensities for 5-FU-loaded samples followed by a further increase in emissions for the powders released drug to the PBS medium. The findings of the study may be useful for monitoring the degradation of bioactive glasses, conversion to hydroxyapatite as well as drug delivery after implantation.
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    Improvement of optical properties of one-dimensional CaAl12O19:Mn4+ phosphor via Er3+- and Tb3+- doped bioactive glass powders
    Oguzlar, S; Ongun, MZ; Deliormanli, AM
    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.