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Öğe Adsorption of thorium (IV) ions by metal ion doped ZnO nanomaterial prepared with combustion synthesis: Empirical modelling and process optimization by response surface methodology (RSM)(Pergamon-Elsevier Science Ltd, 2021) Kaynar, Ümit H.; Kaynar, S. Cam; Karalı, E. Ekdal; Ayvacıklı, M.; Can, N.Environmental problems have reached enormous dimensions, driving efforts to remove and recycle waste from energy and industrial production. In particular, removing the radionuclide contamination that occurs as the nuclear industry grows is difficult and costly, but it is vital. Technologic and economical methods and advanced facilities are needed for the separation and purification of radioactive elements arising from the nuclear industry and uranium and thorium mining. With the adsorption method, which is the most basic separation and recovery method, the use of high-capacity nanomaterials has recently gained great importance in reducing the activity of the waste, reducing its volume by transforming it into solid form, and recovering and removing liquid radioactive wastes that might harm the ecological environment. This study aimed to determine the adsorption properties of metal ion-doped nano ZnO (nano-ZnO:Al) material synthesized by the microwave-assisted gel combustion method for the adsorption of thorium (IV) from aqueous media. First, characterization processes such as XRD, SEM, BET and zeta potential were performed to observe changes in the host ZnO adsorbent structure caused by the doping process. Later, this was optimized via the response surface method (RSM), which is widely used in the characterization of the adsorption properties of thorium (IV) from aqueous solutions. Such characterization is commonly used in industrial research. We tested how pH (3-8), temperature (20-60 degrees C), Th (IV) concentration (25-125 mg/L) and adsorbent amount (0.01-0.1 g) affect adsorption efficiency. The best possible combinations of these parameters were determined by RSM. It was calculated by RSM that the design fits the second order (quadratic) model using the central composite design (CCD) for the design of experimental conditions. R-2 and R-2 adjusted values from the parameters showing the model fit were 0.9923 and 0.9856, respectively. According to the model, the experimental adsorption capacity was 192.3 mg/g for the doped-ZnO nanomaterial under the theoretically specified optimum conditions. Also, the suitability of Th (IV) adsorption to isotherms was examined and thermodynamic parameters were calculated.Öğe Cathodoluminescence and photoluminescence properties of Dy doped La2CaB10O19 phosphor(Elsevier, 2020) Ayvacıklı, M.; Kaynar, Ümit H.; Karabulut, Y.; Guinea, J. Garcia; Doğan, T.; Can, N.In this study, we report a detailed analysis of the photoluminescence (PL) and cathodoluminescence (CL) properties of La2CaB10O19 (LCB) doped with Dy ion. Dy doped LCB materials were successfully synthesized using a sol-gel combustion method. Dy doped LCB has the monoclinic structure with lattice parameters a = 11.02067 angstrom, b = 6.55755 angstrom, c = 9.10541 angstrom and alpha = gamma = 90.00, and 13 = 91.49?. Under the excitation by a low voltage electron beam and pulse laser at 349 nm, the LCB:Dy3+ phosphor produces the characteristic emission bands of Dy3+ due to intra-configuration transitions of F-4(9/2) -> H-6(15/2) (480 nm, blue), F-4(9/2) -> H-6(13/2) (574 nm, yellow), F-4(9/2) -> H-6(11/2) (662 nm, red) and F-4(9/2) -> H-6(9/2) (752 nm, red). The concentration quenching phenomenon was observed in both CL and PL measurements and optimum doping concentration was estimated to be 2%. We suggest that the concentration quenching mechanism of intense yellow emission at 574 nm was attributed to dipole-dipole interaction for both CL and PL.Öğe Cathodoluminescence properties of La2MoO6:Ln3+ (Ln: Eu, Dy, and Sm) phosphors(Elsevier Ltd, 2020) Ayvacıklı, M.; Kaynar, Ümit H.; Karabulut, Y.; Guinea, J.G.; Bulcar, K.; Can, N.La2MoO6 orange-red phosphors with high efficiency incorporated with Eu, Dy and Sm have been synthesized through a gel combustion method. The influences of rare earth doping in synthesized samples were analysed by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and cathodoluminescence. Rare earth doped La2MoO6 samples show strong emission bands in the range of 400–750 nm and optimal doping concentration for all samples was 2 mol%. La2MoO6 host doped Eu ion showed intense and predominant emission peaks in 450–750 nm range. The electrical multipolar interaction contributed to the non-radiative energy transfer between Eu3+ ions in La2MoO6 host matrix. Sm doped La2MoO6 host exhibited orange-red CL emission peaks at 564, 608, 652 and 708 nm La2MoO6:Dy3+ phosphor displayed emissions at 484, 574 and 670 nm, respectively. The observed intense and sharp emission peaks indicate that La2MoO6 is promising host for lanthanides doped phosphor materials in the applications of optoelectronic. © 2020 Elsevier LtdÖğe Comprehensive study of photoluminescence and cathodoluminescence of Eu and Tb doped Mg2SiO4 prepared via a solid-state reaction technique(Elsevier, 2020) Uçar, Z. G. Portakal; Akça, S.; Doğan, T.; Halefoğlu, Y. Z.; Kaynar, Ümit H.; Ayvacıklı, M.; Can, N.We report narrow-band green-red emitting Mg2SiO4 phosphors successfully synthesized through solid-state reaction method, and the cathodoluminescence (CL) and photoluminescence (PL) properties of the samples were investigated in detail. Under electron beam and 275 nm excitation, Mg2SiO4 phosphors doped with various Eu3+ and Tb3+ concentrations in the range of 1 mol % up to 10 mol % exhibit typical green and red emissions, respectively. Tb doped samples were efficiently excited by a low voltage electron beam and UV light, yielding several emission peaks between 370 and 760 nm, and produced a bright green light peaking at 541 nm due to the D-5(4) -> F-7(5) transition. Eu3+ doped samples exhibited CL and PL emission spectra from D-5(0) to F-7(j) manifold transitions of Eu3+. A strong red-light emission peaking at 610 nm also supports the incorporation of Eu3+ ions. A concentration quenching effect was observed and discussed for both phosphors. The optimal doping concentration of Eu3+ and Tb3+ doped phosphors was 7 mol %. In view of the outstanding performance in the PL and CL, the Mg2SiO4:Eu3+, Tb3+ can be considered as a promising green and red phosphor in solid-state lighting applications.Öğe Effect of Sm(3+)and Mn2+ incorporation on the structure and luminescence characteristics of Zn2SiO4 phosphor(Pergamon-Elsevier Science Ltd, 2021) Portakal-Uçar, Z. G.; Doğan, T.; Akça, S.; Kaynar, Ümit H.; Topaksu, M.To evaluate the dopant effect precisely, X-ray diffraction (XRD) for structural, scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDS) analysis for morphological, photoluminescence (PL) and thermoluminescence (TL) characteristics of un-doped, 2.0 mol% Sm3+ doped and 2.0 mol% Sm3+;x mol% Mn2+ (x = 0.5, 1.0, 2.0, 4.0) doped Zn2SiO4 phosphors were tested. PL mechanisms of excitation and emission were discussed together with data on the structure and morphology of the samples. The beta doses from 0.1 to 500 Gy with various steps were applied to observe the glow curve readouts after 200 degrees C preheat at a linear heating rate of 2 degrees C/s from RT to 500 degrees C. Zn2SiO4:2.0%Sm3+;0.5%Mn2+ was chosen for further analysis due to having both the most PL and TL peak area. Various heating rate method was used to determine the kinetic parameters as well as initial rise with T-M-T-stop analysis and computerized glow curve deconvolution methods.Öğe Enhancing the blue luminescence behaviour of the Li co -doped novel phosphor ZnB 2 O 4: Tm 3+(Elsevier Science Sa, 2020) Kücük, N.; Kaynar, Ümit H.; Akça, S.; Alajlani, Y.; Yin, L.; Wang, Y.; Can, N.[No Abstract Available]Öğe Eu3+ and Dy3+ doped La2MoO6 and La2Mo2O9 phosphors: Synthesis and luminescence properties(Pergamon-Elsevier Science Ltd, 2020) Kaynar, Ümit H.; Kaynar, Sermin Çam; Alajlani, Yahya; Ayvacıklı, Mehmet; Karalı, Elçin Ekdal; Karabulut, Yüksel; Can, NurdoğanWe report a detailed structural analysis and properties of the photoluminescence (PL) and thermoluminescence (TL) spectra of Eu3+ and Dy3+ incorporated into novel La2MoO6 and La2Mo2O9 phosphors synthesized successfully through gel combustion synthesis. The formation of a tetragonal phase and a cubic structure were verified for La2MoO6 and La2Mo2O9 phosphors via X-ray diffraction (XRD) studies. Dy doped samples exhibited blue and green emissions at 480 nm (F-4(9/2) -> H-6(15/2)) and 572 nm (F-4(9/2) -> H-6(13/2)), and also Eu doped samples showed a sharp emission peaks at 612 and 619 nm (D-5(0) -> F-7(2)) upon 349 nm pulse laser excitation. Peak shape (PS) technique was utilised to determine activation energy, frequency factor and order of kinetics associated with the main glow curves in undoped and Eu and Dy doped samples after X-ray irradiation. The present findings suggest that Eu and Dy incorporated La2MoO6 and La2Mo2O9 phosphors are highly auspicious candidates for applications in solid-state lighting.Öğe Influence of laser excitation power on temperature-dependent luminescence behaviour of Ce- and Tb-incorporated BaMgAl10O17 phosphors(Pergamon-Elsevier Science Ltd, 2020) Kaynar, Ümit H.; Kaynar, S. Cam; Ayvacıklı, M.; Karabulut, Y.; Souadi, G. O.; Can, N.BaMgAl10O17 (BAM) is a highly suitable host lattice for various rare earth ions with excellent luminescence properties in different spectral regions, including a strong photoluminescence (PL) emission from the visible spectral region. A new Ce- and Tb-incorporated BaMgAl10O17 phase was synthesized successfully using a wet combustion method and it was studied as a function of the temperature and laser excitation power. We further characterize the obtained phosphors with X-ray diffraction at room temperature. Different fuel/oxidant (f/o) ratios were introduced to investigate the optimum synthesis conditions for the BAM phosphors and optimum ratio was found out to be 8. The photoluminescence (PL) spectra were collected under the excitation light generated by a Nd:YLF pulse laser at 349 nm as the temperature was increased from 10 K to 300 K. A strong green emission of Tb3+ was observed in the green region of the spectrum due to the D-5(4)-> F-7(J) transition. We also observed a wide emission band from the Ce3+ ion in the wavelength range of 350-650 nm. The luminescence intensities of all phosphors exhibited different patterns with an increase in the temperature. We also evaluated how the PL spectrum of the rare earth-activated BAM host matrix shifts under various laser excitation powers. The PL intensity of Ce-activated BAM significantly shifted (similar to 30 A) to the blue region of the spectrum with an increase in the laser excitation power, however we did observed no shift forTb(3+) activated BAM. The present findings suggest that Tb-incorporated BaMgAl10O17 can be effective as a green phosphor candidate material with a wide range of applications.Öğe Synthesis and beta particle excited thermoluminescence of BaSiF6 phosphor(Pergamon-Elsevier Science Ltd, 2022) Souadi, G. O.; Akça Özalp, S.; Karalı, E. Ekdal; Kaynar, Ümit H.; Ayvacıklı, M.; Topaksu, M.; Can, N.BaSiF6 phosphor was synthesized by a gel combustion method. The crystalline size was found to be 54.17 +/- 4.36 nm using Williamson-Hall (W-H) approximation. The TL data collected by means of a combination of a commercial BG39 and HC575/25 filters was studied to evaluate basic kinetic parameters. Three TL glow peaks of BaSiF6 phosphors are centered at around 84, 190 and 322 degrees C. T-m-T-stop, various heating rate (VHR) and computerized glow-curve deconvolution (CGCD) method were utilized to analyse collected data. Our findings indicate that luminescence process in scrutinized material may obey second order kinetics. The TL dose response of the TL glow peaks exhibits a linear characteristic up to 100 Gy. Deconvolution of the glow curve reveals that the number of the component TL glow peaks in the complex glow curve is composed of well-isolated six overlapping glow peaks. The FOM value is 2.32.Öğe Synthesis and competitive luminescence quenching mechanism of Ca(3)Al(2)O(6)Ln(3+)(Ln: Dy and Sm) phosphors(Pergamon-Elsevier Science Ltd, 2020) Bakr, M.; Kaynar, Ümit H.; Ayvacıklı, M.; Benourdja, S.; Karabulut, Y.; Hammoudeh, A.; Can, N.Sm3+ and Dy3+ activated Ca3Al2O6 phosphors were produced through a gel combustion method using Urea + beta-Alanine, Urea, and Urea + Glycine as fuels. The crystal structure and the phase purity of the obtained materials were characterized by X-ray powder diffraction (XRD). Ca3Al2O6 :Sm3+ phosphor shows characteristic emission lines (565 nm, 602 nm, 649 nm, and 714 nm) in the orange red region assigned to (4)G(5/2) -> H- 6(J) (J = 5/2, 7/2, 9/2, 11/2) transitions of Sm3+. The strongest peak is located at 602 nm. Emission spectra of Ca3Al2O6 :Dy3+ show that there are two dominant peaks centered at 480 nm and 573 nm emitting blue and yellow light. Optimum doping concentrations of Sm(NO3)(3) and Dy(NO3)(3) are 0.01 % and 0.03 %, respectively. The concentration quenching mechanism is verified to be a dipole-dipole interaction as the type of energy transfer among Sm3+-Sm3+ and Dy3+-Dy3+ ions. The critical distance is also calculated to be 24.19 angstrom and 16.77 angstrom, respectively.Öğe Synthesis and enhanced photoluminescence of the BaSiF6:Dy3+ phosphors by Li+ doping via combustion method(Elsevier, 2022) Souadi, G. O.; Kaynar, Ümit H.; Ayvacıklı, M.; Canımoğlu, A.; Can, N.Undoped BaSiF6, Dy3+ doped BaSiF6, and Dy3+, Li+ co-doped BaSiF6 phosphors were synthesized through a gelcombustion method. The prepared samples were characterized by powder x-ray diffraction (XRD), Fourier transform infrared (FTIR), energy dispersive x-ray spectroscopy (EDS), and photoluminescence (PL) techniques. The XRD data revealed that both the Dy3+ doped and Li+ co-doped BaSiF6 phosphors exhibited a single-phase structure belonging to the space group R (3m) over bar which matched well with the standard JCPDS files (No. 002-6613). FTIR spectra showed absorption bands at 3417 cm -1 , 1640 cm(-1), and 1620 cm(-1) corresponding to water molecules. EDS analysis confirmed the chemical composition of the prepared samples. The PL emission spectra of BaSiF6:Dy3+ by different co-doping concentrations of Li+ exhibited prominent emission peaks at 490 nm, 572 nm, 672 nm and 758 nm. The incorporation of Li+ is beneficial for enhancing the photoluminescence intensity. The optimum Li+ amount was 8% for BaSiF6:Dy3+ and then started to decrease. The enhancement could be due to the occurrence of oxygen vacancies due to the incorporation of Li+ ions. The x = 0.301 and y = 0.361 coordinates of this phosphor with varying Li+ dopant concentration determined by the Commission Internationale de l'Eclairage (CIE - 1931) were in the white range. The present work demonstrates how a simple and effective method can be used to prepare novel nanophosphors for applications in the field of visible light emitting devices with enhanced white emission.Öğe Synthesis and photoluminescence characteristics of a novel Eu and Tb doped Li2MoO4 phosphor(Pergamon-Elsevier Science Ltd, 2021) Souadi, G. O.; Kaynar, Ümit H.; Ayvacıklı, M.; Çoban, M. B.; Oğlakçı, M.; Canımoğlu, A.; Can, N.Li2MoO4:x Eu3+ and Li2MoO4:xTb(3+) phosphors, where x = 0.5, 1, 2, 3, 5 and 7 wt%, were synthesized through a gel-combustion method. The XRD data reveals that Eu3+ and Tb3+ doped Li2MoO4 phosphors exhibit a Rhombohedral structure belonging to the space group R3 which matched well with the standard JCPDS files (No.0120763). We present photoluminescence (PL) spectra from Eu and Tb doped Li2MoO4 under 349 nm Nd:YLF pulses laser excitation over the temperature range of 10-300 K. Undoped Li2MoO4 shows a wide broad band around 600 nm because of the intrinsic PL emission of tetrahedral of MoO42- which was in good agreement with previous findings. Under the excitation of 394 nm, the as-synthesized phosphors exhibited sharp and strong intensity PL emission signals in the red (612 nm, D-5(0) -> F-7(2) transition) and green (544 nm, D-5(4) -> F-7(5) transition), respectively. The critical doping concentration of Eu3+ and Tb3+ ions in the Li2MoO4 were estimated to be 2 wt%. The concentration quenching phenomena were discussed, and the critical distances for energy transfer have also been evaluated by the concentration quenching.Öğe Synthesis and photoluminescence characteristics of Dy incorporated MoO3 phosphor: Suppression concentration quenching(Elsevier Ltd, 2020) Ayvacıklı, M.; Kaynar, Ümit H.; Karabulut, Y.; Canımoğlu, A.; Bakr, M.; Akça, S.; Can, N.A series of MoO3:Dy3+ phosphors have been synthesized via the gel-combustion method. The X-ray and photoluminescence (PL) emission spectra were employed to characterize the obtained phosphors. The prepared samples were characterized through XRD measurements and exhibited that Dy3+ ions can be successfully incorporated into the host material. The PL emission bands of Dy3+ doped MoO3 were observed at 486 nm, 574 nm and 666 nm which are assigned to the transitions of 4F9/2 ? 6H15/2, 4F9/2 ? 6H13/2 and 4F9/2 ? 6H11/2, respectively. Concentration quenching were largely taken into consideration as one of the crucial aspects limiting the application range of phosphors in today's modern world. An abnormal thermal quenching dependence was reported when Dy3+ ions were incorporated into MoO3 host matrix. In order to understand the origin of this beneficial behaviour, energy transfer processes occurring via radiative and nonradiative mechanisms were investigated to elucidate this suppression of the concentration quenching. © 2020 Elsevier LtdÖğe Thermoluminescence behaviour of europium doped magnesium silicate after beta exposure(Elsevier, 2020) Uçar, Z. G. Portakal; Kaynar, Ümit H.; Doğan, T.; Souadi, G. O.; Ayvacıklı, M.; Canımoğlu, A.; Can, N.This article presents a detailed analysis of beta ray exposed thermoluminescence response of a series of Eu3+ doped (0.5-10 mol%) Mg2SiO4 nanocrystalline samples successfully synthesized through solid state reaction method. Optimizing the doping concentration of Eu3+ ion in Mg2SiO4 phosphor was found as 3 mol%. Two main peaks were seen at 246 degrees C and 374 degrees C and also low temperature peak at 78 degrees C. The intensities of these peaks were increased linearly with increasing beta absorbed dose. T-m-T-stop method was used to reveal trap levels. Variable heating rate and computerized glow curve deconvolution methods were also used to evaluate the number of peaks and kinetic parameters, namely activation energy and frequency factor. The results of a series of experiments carried out to investigate some fading characteristics of Mg2SiO4:Eu3+ were also presented. The findings suggest that thermoluminescence properties of Mg2SiO4:Eu(3+ )makes this material suitable and promising dosimetric phosphor material for medical applications.Öğe Thermoluminescence glow curve analysis and evaluation of trapping parameters of dysprosium doped lanthanum calcium borate La2CaB10O19(Elsevier, 2021) Bulcar, K.; Oğlakçı, M.; Kaynar, Ümit H.; Ayvacıklı, M.; Souadi, G. O.; Topaksu, M.; Can, N.The present work elucidates thermoluminescence study of Dy activated lanthanum calcium borate (La2CaB10O19) phosphors and determination of trapping parameters. Two glow curves located at 132 and 295 degrees C were observed and showed a linear TL response. The kinetic parameters of the glow peaks were evaluated using variable heating rate, repeated initial rise method and Computerized Glow Curve Deconvolution. Analysis of the main dosimetric peaks reveals that the values of the activation energy and pre-exponential factor are found to be 0.78-1.145 eV and 8.59 x 10(9)-8.44 x 10(11) s(-1), respectively. The sample doped with 1% Dy3+ exhibits a good stability for the reusability. Besides, the found results indicate that the temperature maximum shifts to the higher temperature side as the heating rate increases. Contrary to previously expressed theoretical expectations, anomalous heating rate dependence was observed in Dy3+ doped La2CaB10O19 sample and a semi-localized transition model explaining the anomalous heating rate effect was employed.Öğe Thermoluminescence properties of beta particle irradiated Ca3Al2O6 phosphor relative to environmental dosimetry(Elsevier, 2020) Bakr, M.; Portakal-Uçar, Z. G.; Yüksel, M.; Kaynar, Ümit H.; Ayvacıklı, M.; Benourdja, S.; Can, N.Undoped Ca3Al2O6 phosphor was successfully synthesized through a gel-combustion method using different fuels. It was characterized by X-ray diffraction (XRD) technique and its cubic phase structure was confirmed from XRD pattern. TL data were recorded from room temperature (RT) to 500 degrees C in the heating rate of 2 degrees C/s. The glow curves of Ca3Al2O6 sample exposed to different beta doses (0-200 Gy) exhibited a significant glow peak at about 184 degrees C. The TL intensity of the glow peak exhibited very good linearity between 0.1 and 10 Gy. Following this, it was decreased at higher doses which was referred to this effect as monotonic dose dependence. Initial rise (IR), peak shape (PS), and variable heating rate (VHR) methods were used to estimate trapping parameters. Computerized glow curve deconvolution (CGCD) method via TLAnal software was also applied to estimate the number of peaks and kinetic parameters corresponding to the main glow curve in Ca3Al2O6 sample. The trapping activation energy of the main dosimetric peak was calculated to be around 1.30 eV for all methods. Present findings confirm that Ca3Al2O6 host is a promising candidate for applications in environmental dosimetry as one depicts good TL dose response with adequate sensitivity and linearity.Öğe Thermoluminescence study and evaluation of trapping parameters of samarium doped barium silicate phosphor(Taylor & Francis Ltd, 2021) Alajlani, Y.; Oğlakçı, M.; Kaynar, Ümit H.; Ayvacıklı, M.; Portakal-Uçar, Z. G.; Topaksu, M.; Can, N.We report the detailed analysis of thermoluminescence (TL) glow curves and the evaluation of kinetic parameters of Sm3+-incorporated BaSi(2)O(5.)The effect of various heating rates on TL kinetics and glow peak temperatures of Sm3+-doped BaSi2O5 phosphors exposed to beta particle irradiation at room temperature are investigated. The glow curve of the phosphor exposed to beta-irradiation consists of two main peaks with maxima at about 91 degrees C and 193 degrees C and exhibits good linearity between 1 and 10 Gy. The activation energies and frequency factors of trap centers involved in the TL emission were calculated from the TL glow curve of the sample by means of variable heating rate (VHR), repeated initial rise (RIR), and computerized glow-curve deconvolution (CGCD). Analysis of the main dosimetric peak techniques indicate that activation energies (E) and pre-exponential factor (s) vary between 0.93 and 1.72 eV, 10(10) and 10(13) s(-1). It is found that the temperature of the glow peaks shifts toward the higher temperatures and the TL intensity smoothly decreases as the heating rate increases. The behavior of the TL intensities and glow peak temperatures as a function of the heating rate are discussed with regards to thermal quenching.
