Person: ERDEM, MURAT
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ERDEM
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MURAT
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Publication Metadata only Effect of pressure and temperature on the white light produed by Ytterbium (III) doped and undoped Yttrium Silicate nanopowders excited by a laser diode(ELSEVIER SCIENCE BV, 2017) ERDEM, MURAT; Cinkaya, Hatun; Eryurek, Gonul; Bilir, Gokhan; Erdem, Murat; Di Bartolo, BaldassareIn the present study, we have directed our attention to yttrium silicate nanopowders undoped and with different ytterbium (III) dopant concentrations, systems that, when illuminated by a laser diode emit white light. We have investigated the effects that two physical parameters, pressure of the ambient and temperature of the powders have on the emission of the white light. We have observed that low pressure and high temperatures enhance the intensity of the emitted white light. At high pressure, the output from the nanopowder is represented by groups of sharp lines due to ytterbium cooperative emission and unwanted erbium impurities. As the pressure decreases to 0.01 mbar, the spectrum changes to a wide band resembling the white light spectrum. High temperatures of the nanopowders enhance the emission of white light. (C) 2016 Elsevier B.V. All rights reserved.Publication Metadata only Molten salt synthesis and spectral properties of Nd3+ doped CdNb2O6 columbite phosphors(ELSEVIER SCIENCE SA, 2014) EKMEKÇİ, METE KAAN; Ekmekci, Mete Kaan; Erdem, Murat; Mergen, Ayhan; Ozen, Gonul; Di Bartolo, BaldassarePure and Nd-doped CdNb2O6 particles have been prepared by a molten salt method using cadmium nitrate, niobium oxide and Li2SO4-Na2SO4 salt mixture as a flux at a relatively low temperature as compared to solid-state reaction method. X-ray diffraction patterns of the pure CdNb2O6 samples exhibited a single orthorhombic phase. Photoluminescence (PL) properties of all the undoped and Nd-doped samples in visible and near-infrared spectral region were studied in detail. While a strong blue emission band centered at 460 nm at room temperature was observed for the pure CdNb2O6, additional characteristic luminescence of Nd3+ at 1.06 mu m was observed for Nd-doped CdNb2O6. Concentration quenching phenomenon was detected depending on the Nd-doping concentrations at both room and relatively low temperatures. This characteristic of the doped samples may be ascribed to the energy transfer between Nd3+ and niobate groups (NbO6). (C) 2013 Elsevier B. V. All rights reserved.Publication Metadata only Investigation of the Luminescence Spectral Profiles and the Efficiencies of Yb3+, Nd3+, Tm3+ Doped Y2O3-SiO2 Nano-phosphors(SPRINGER, 2017) ERDEM, MURAT; Cinkaya, Hatun; Bilir, Gokhan; Erdem, Murat; Eryurek, Gonul; DiBartolo, B; Collins, J; Silvestri, LAmong various developed UC luminescence materials, rare earth doped yttrium silicates (YSO) exhibit high chemical durability and thermal stability which are suitable for many applications such as lighting, lasers, optical sensors and biological applications. The reduction to nano size of such materials aims to investigate the issue of how the optical properties affected, and thus to further extend the use of these materials in photonic industry. The studies about the effect of nanoscale to the lattice-electron interaction is not yet enough to understand the mechanisms. For this reason, the influence of the various synthesis techniques to the size and the effect of the size of those nano-materials on the optical and thermal properties are basic research areas for various photonic device design and their developments. In most cases, the rare earth ions replace other ions of similar size and same valence state in the host medium. The dopant ions (Tm3+, Nd3+ and Yb3+) replace the Y3+ ions in the host, randomly. Because of the dopant ions have a different ionic radius than the yttrium ions, they distort the lattice around them. As a consequence, the local environment of the different dopants gives different absorption and radiation energies for each single ion in the host. The selection of host material change the luminescent effects on the emission properties such as obtaining different color in emitted light.Publication Metadata only Concentration effect of Er3+ ions on structural and spectroscopic properties of CdNb2O6 phosphors(PERGAMON-ELSEVIER SCIENCE LTD, 2014) EKMEKÇİ, METE KAAN; Ghafouri, Sanaz Aian; Erdem, Murat; Ekmekci, M. Kaan; Mergen, Ayhan; Ozen, GonulThis study is focused on the synthesis and characterization of CdNb2O6 compounds doped with of Er3+ ions. Powders were synthesized by using the molten salt method and annealed at 900 degrees C for 4h. The synthesized particles were structurally characterized by using X-ray diffraction, scanning electron microscopy. A single phase of the CdNb2O6 was determined and the size of the particles was found to be affected by the presence and the concentration of Er3+ ions. Luminescence properties of each sample were investigated by measuring accurately the emission and excitation spectra at room temperature in the wavelength range of 200-1700 nm by exciting the Er3+ ions at 379 nm and 805 nm. Quenching of the luminescence in both visible and near infrared spectral regions was observed to be above 1.0 mol% Er3+ concentration. (C) 2014 Elsevier Ltd. All rights reserved.Publication Metadata only Synthesis and characterization of the novel 4-(1-(pyridin-4-yl) ethoxyl) substituted bis(phthalocyaninato) rare earth complexes and investigation of their two-photon absorption-based third-order non-linear optical properties(ELSEVIER, 2022) GÖRK, GÜLŞEN; Cavus, Aleyna; Gork, Gulsen; Erdem, Murat; Ozer, MetinNovel 4-(1-(pyridin-4-yl) ethoxyl) substituted double-decker rare earth phthalocyanine complexes were synthesized starting from (R)-4-(1-(pyridin-4-yl) ethoxy) phthalonitrile with proper rare earth metal acetates in octanol catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene at 300 degrees C. The new starting phthalonitrile compound was obtained from (R)-1-(pyridin-4-yl) ethan-1-ol and 4-nitrophthalonitrile in acetonitrile at reflux temperature in the presence of potassium carbonate as a catalyst. The characterization of the synthesized and isolated compounds was performed by elemental analysis, infrared, ultraviolet visible, proton and correlation spectroscopy nuclear magnetic resonance, and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopic methods. Nonlinear optical responses of all complexes are investigated using the Z-scan method. The nonlinear absorption coefficient, two-photon absorption cross-section, and the imaginary part of the nonlinear susceptibility of complexes are calculated for each discrete concentration. All these nonlinear parameters of our rare-earth coordinated doubledecker phthalocyanines present a decrement due to the aggregation under high optic powers, which result in sequential two-photon absorption for smaller ionic radii. (c) 2021 Elsevier B.V. All rights reserved.Publication Metadata only Structural and spectroscopic properties of Nd3+:Y2Si2O7 phosphors(ELSEVIER SCI LTD, 2013) TAV, CUMALİ; Erdem, Murat; Ozen, Gonul; Tav, Cumali; Di Bartolo, BaldassarePhosphors of alpha-Y2Si2O7 doped with Nd3+ ions were prepared using the sol gel technique. Nano-sized crystalline phosphor powders were obtained by annealing the dried gels at 960 degrees C. The crystallization properties of the phosphor powders were determined from their XRD patterns. The alpha-Y2Si2O7 phase was the only phase observed in all compositions. As the amount of amorphous SiO2 in the composition was increased, the crystalline sizes and the widths of the size distribution curves were found to decrease from 17.8 nm to 10.6 nm and from 15.6 nm to 12.2 nm, respectively. The spectroscopic properties of the powders were studied by measuring the luminescence and the decay patterns of the F-4(3/2) -> I-4(9/2) and F-4(3/2) -> I-4(11/2) transitions between 50 K and 310 K. No appreciable effect of the crystallite sizes on the average lifetime of the F-4(3/2) level was observed at temperatures below 100 K. The effect of temperature, however, becomes relevant above 100 K as the size of alpha-Y2Si2O7 nano-crystal becomes smaller. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Publication Metadata only Effect of spatial confinement on luminescence of Y3Al5O12 nano-particles doped with chromium ions(ELSEVIER, 2013) ERDEM, MURAT; Ozen, Gonul; Erdem, Murat; Collins, John; Bettinelli, Marco; Di Bartolo, Baldassare; Piccinelli, F.; Speghini, A.We have studied the spectroscopic properties of four nano-powder samples of Y3Al5O12: Cr particles with diameters ranging from 28 nm to 250 nm. For each sample we have measured accurately the emission spectrum in a wide range of temperatures ranging from 30 to more than 600 K. The spectra generally consisted of the R-lines narrow spectral emission and of the accompanying vibronic side-bands. We noted the increase of the vibronic emission intensity with respect to the R-line intensity going from the larger to the shorter diameter powders. For each sample we have also measured the decay patterns of the excited Cr ions following a pulsed excitation. These measurements were conducted in the same temperature range (30-600 K) in order to fully characterize the samples examined. We have confirmed the fact that such patterns vary considerably with the size of the nano-particle, so that they may be considered signatures of these sizes. In the discussion of the experimental results we present some thoughts on the information provided by the data and in the conclusions we elaborate these thoughts and provide a coherent picture of the processes at work. (C) 2013 Elsevier B.V. All rights reserved.Publication Metadata only Change of spectral output with pressure and white light generation in nanoscale Yb3+:Y2Si2O7(ELSEVIER SCIENCE BV, 2015) ERDEM, MURAT; Erdem, Murat; Eryurek, Gonul; Di Bartolo, BaldassareWe report the drastic dependence on pressure of the spectral output of sol-gel derived Yb3+:Y2Si2O7 nanoparticles when excited with the 950 nm emission of a laser diode. The average particle size was estimated 40 nm. The spectrum obtained at atmospheric pressure consisted of an intense blue band. At low pressure the spectrum changed to a wide optical band. (C) 2015 Elsevier B.V. All rights reserved.Publication Metadata only Nonlinear optical behavior and optical power limiting characteristics of peripheral symmetrical and non-symmetrical zinc phthalocyanines with nanosecond pulsed excitation(PERGAMON-ELSEVIER SCIENCE LTD, 2021) GÖRK, GÜLŞEN; Erdem, Murat; Korkmaz, Eda; Kosoglu, Gulsen; Ahmetali, Erem; Farajzadeh, Nazli; Eryurek, Gonul; Kocak, Makbule BurkutIn this study, the optical nonlinear absorption and optical limiting performances of symmetrical and non-symmetrical zinc phthalocyanines in tetrahydrofuran (THF) solution were conducted by the open aperture z-scanning technique. A new non-symmetrically substituted metallophthalocyanine, namely 2(3)-[(4- nitrophenyl)ethynyl]-{9(10),16(17),23(24)-tris-(3,5-bis(trifluoromethyl)phenoxy)-phthalocyani-nato}zinc(II) (1b), was synthesized and then characterized by applying different spectroscopic methods, such as FT-IR, H-1 NMR and MALDI-TOF spectroscopy. According to the literature, {2(3),9(10),16(17),23(24)-tetrakis-(3,5-bis(trifluoromethyl)phenoxy)-phthalocyaninatolzin(II) (1a), {2,3,9,10,16,17,23,24-octakis-(3,5-bis(trifluomethyl)phenoxy)-phthalocyaninato}zinc(II) (2a) and 2(3)-[(4-nitrophenyl)ethynyl]-{9,10,16,17,23,24-hexakis-(3,5-bis(trifluoromethyl)phenoxy)-phthalocyani nato}zinc(II) (2b) were prepared. The effect of the symmetry and substituent's number on the nonlinear behavior was determined. A Nd:YAG laser, nanosecond pulsed at 532 nm, was used as the excitation source. The measurements of the input-output power and the nonlinear transmission properties were carried out for different excitation power values and different concentrations of the phthalocyanines in the THF solution. The nonlinear absorption coefficient of beta and the imaginary part of the third order nonlinear susceptibility of the medium (X-3) were found to be strongly dependent on the concentration. All the zinc phthalocyanine complexes showed good optical limiting performances, attributed to a reverse saturable absorption (RSA) process. The results indicate that the zinc phythcyanine complexes are promising candidates for optical limiting materials. (C) 2020 Elsevier Ltd. All rights reserved.Publication Metadata only Upconversion Yb3+/Er3+:La2Ti2O7 phosphors for solid-state lighting and optical thermometry(Elsevier B.V., 2022) ERDEM, MURAT; Erdem M., Cantürk S.B., Eryürek G.The solid-state reaction was employed as a suitable method to produce orthorhombic Yb3+/Er3+ co-doped La2Ti2O7 phosphors. The pump power and temperature dependencies of spectra of the Yb3+/Er3+ co-doped La2Ti2O7 were studied for color tunability and optical thermometry. The pump power significantly affected the color coordinates of the phosphors. The upconversion green light transformed to the broad white light at higher pump power. A two-photon transition was proposed to explain the upconversion energy transfer process. The fluorescence intensity ratio technique was used to calculate the optical temperature sensor sensitivities. The ΔE energy difference obtained from the intensity ratios of the thermally coupled 2H11/2 and 4I15/2 energy levels of Er3+ are 763.64 ± 76.62 cm−1, 777.77 ± 44.62 cm−1, 640.71 ± 137.39 cm−1 for La1.95Yb0.04Er0.01Ti2O7, La1.94Yb0.04Er0.02Ti2O7, and La1.93Yb0.04Er0.03Ti2O7, respectively. Absolute temperature sensitivities of the phosphors decreased with increasing Er3+ concentration. The maximum absolute sensitivity was determined to be 0.51x10-2 K−1 at 553 K for La1.95Yb0.04Er0.01Ti2O7, 0.64x10-2 K−1 at 571 K for La1.94Yb0.04Er0.02Ti2O7, and 0.38x10-2 K−1 at 457 K for La1.93Yb0.04Er0.03Ti2O7. © 2022 Elsevier B.V.