Search

Near-infrared induced CuAAC click reaction using an interdependent heterogeneous catalytic system.

Er3+ and Yb3+/Er3+ doped TeO2–ZnO–BaO glasses were synthesized using the melt quenching technique with two different Er3+ concentrations. The refractive index was calculated to be around 2.14 from the optical band gap energies of the glasses. Under 975 nm laser excitation, weak blue, strong green and red emissions were observed in the visible region, while broadband emission around 1530 nm was recorded in the near infrared region. The increase in red emission intensity as a result of energy transfer from Yb3+ ions to Er3+ ions in Yb3+/Er3+ co-doped glasses is clearly reflected in the change in color coordinates. The temperature sensing abilities of the glasses were determined from the intensity ratios of light emitted from thermally coupled energy levels (2H11/2 and 4S3/2) of Er3+ ions. The highest absolute sensitivity was determined as 0.0046 K−1 at 453 K for Er3+ doped glass and 0.0067 K−1 at 353 K for Yb3+/Er3+ co-doped glass. These results show that Er3+ and Yb3+/Er3+ doped TeO2–ZnO–BaO glasses are promising candidates for both lighting and optical temperature sensors.

The fabrication of size-dependent rare earth ion-doped materials for photonic devices has attracted interest in the search for color tunability and noncontact temperature sensing properties with high sensitivity. Sol-gel Pechini is an appropriate method compared to other methods to prepare Yb3+/Er3+:gadolinium gallium garnet (GGG) crystals at the nanoscale. This work presents a study of white-light emission and optical thermometry properties of Yb3+/Er3+:GGG nanocrystals based on the upconversion (UC) blue, green, and red emissions observed under 975 nm laser excitation. The color coordinates of the studied nanocrystals were affected by the crystalline size. Yb3+ (2 mol %)/Er3+(1 mol %):GGG nanocrystals have the highest maximum absolute sensitivities of 0.0028 K-1 at 378 K and 0.0041 K-1 at 561 K for 17 and 45 nm crystalline sizes, respectively. In light of the observations, Yb3+/Er3+:GGG may be a good candidate material for use in white light and optical temperature sensing., Marmara University Scientific Research Projects Commission [FEN-E-090517-0276]; Ege University Scientific Research Projects Coordination Unit [14FEN-027], Marmara University Scientific Research Projects Commission funded the study with a FEN-E-090517-0276 grant number. Ege University Scientific Research Projects Coordination Unit supported the synthesis of GGG nanophosphors with a 14FEN-027 project number.

Yb3+,Er3+,Tm3+:Y2Si2O7 nanopowders were fabricated by a sol–gel method and then annealed at two different temperatures of 1050 °C and 1480 °C for 12 h to investigate the phase effect on the structural and optical properties. X-ray diffraction patterns (XRD) of all powders revealed that most of the peaks were in good harmony with the standard JCPDS cards of Y2Si2O7 (PDF #38-0223 and PDF #38-0440). SEM images of the powders were taken to examine the morphology and chemical composition of the powders. Diffuse reflection spectra of Y2Si2O7 exhibited varying number of transitions depending on the dopant ion in all powders in the range of 400–1050 nm. The spectral properties of the powders were investigated to identify the possible up-conversion (UC) emission mechanism in the range between 400 and 900 nm under 975 nm excitation. A broadening white light emission was observed with increasing laser pumping power at room temperature as well. Spectral profiles of the transitions observed in both reflectance and up-conversion luminescence spectra were found to be crystalline phase dependent.

In the present study, white light emission based on both upconversion and thermal processes from single-phase yttrium silicate nanopowder doped with Neodymium (III) (Nd3+) was investigated at both room pressure and vacuum (0.01 mbar) with a diode laser excitation of 808 nm. 1% Nd3+ doped (per mole) yttrium silicate (Y2O3:SiO2) nanopowder was synthesized by using the sol-gel method and annealed at 1250 °C for 12 h to obtain the powder form. Emission for upconverted white light mainly due to the transitions of Nd3+ ions was obtained below ~ 5.79 W of the laser beam power at atmospheric pressure. For powers exceeding ~ 5.79 W, the powder emitted a thermal white light (WL) due to the photon avalanche mechanism together with thermal processes. The threshold power to obtain thermal white light with the transitions of Nd3+ ions was decreased to ~ 3.51 W at the vacuum condition. These processes were investigated in detail by studying the spectral differences of the rise and decay patterns at atmospheric pressure and vacuum conditions.

PMMA matrices were doped with nano-crystalline neodymium oxides synthesized by thermal decomposition process. X-ray diffraction and high-resolution transmission electron microscopy measurements were carried out to investigate the structure, phase, and the morphology of the Nd2O3 nanocrystals and those embedded in the PMMA matrix. The average grain sizes were estimated 35 ± 6 nm and 46 ± 4 nm for non-annealed and annealed Nd2O3 particles, respectively. The grain size distributions (GSD) were calculated from the diffraction peaks of the annealed and non-annealed Nd2O3 powders and doped PMMA samples. The mass density, refractive index, UV–Visible absorption spectra were measured and the data were analyzed using the Judd–Ofelt approach to determine the oscillator strengths, the spontaneous emission probabilities and the branching ratios as a function of the nano-crystalline Nd2O3 content in the range of 0.1 wt.%–20 wt.% of MMA. Luminescence spectra upon 808 nm diode laser excitation were carried out in the wavelength range of 850–1550 nm at room temperature. The photoluminescence study has shown that the reasonably sharp emission peaks were observed upon heat treatment at 800 °C for 24 h for all concentrations of Nd2O3 nanopowders in PMMA. The infrared laser transition of Nd3+ ions at about 1.06 μm due to the 4F3/2 → 4I11/2 transition was analyzed and discussed in Nd2O3 system for their possible applications in the photonic technology.

The upconversion emission spectra of Yb3+/Ho3+co-doped TeO2-ZnO-BaO glasses were studied for solid-state lighting and optical thermometry. The studied glasses were prepared using the melt quenching technique. The green and red UC emissions of Ho3+ions are due to two-photon absorptions, which cause the various energy transfer processes. The studied glasses show tunable color properties and high-temperature sensor sensitivity. Color coordinates on the CIE chromaticity diagram of those were affected by the pump power and shifted from green to red region at higher Ho3+concentrations. The 5F5 level and (3F4,5S2) levels of Ho3+ are found to be thermally coupled levels. The energy difference (ΔE) between these levels is calculated as 2463.66 cm−1. Among the studied glasses, Yb3+(3.0 mol%)/Ho3+(0.15 mol %) co-doped TeO2-ZnO-BaO show the highest absolute sensitivity of 0.011K−1 at 503K. In the light of conducted observations, the studied glasses are proposed as a good candidate material for lighting and optical temperature sensing.

A method is presented for the initiation of free-radical and free-radical-promoted cationic photopolymerizations by in-source lighting in the near-infrared (NIR) region using upconverting glass (UCG). This approach utilizes laser irradiation of UCG at 975 nm in the presence of fluorescein (FL) and pentamethyldiethylene triamine (PMDETA). FL excited by light emitted from the UCG undergoes electron-transfer reactions with PMDETA to form free radicals capable of initiating polymerization of methyl methacrylate. To execute the corresponding free-radical-promoted cationic polymerization of cyclohexene oxide, isobutyl vinyl ether, and N-vinyl carbazole, it was necessary to use FL, dimethyl aniline (DMA), and diphenyliodonium hexafluorophosphate as sensitizer, coinitiator, and oxidant, respectively. Iodonium ions promptly oxidize DMA radicals formed to the corresponding cations. Thus, cationic polymerization with efficiency comparable to the conventional irradiation source was achieved.

Phosphors of Er 2 O 3 nano-crystalline powders were synthesized by the thermal decomposition method. The structural properties of the nano-powders were investigated with XRD and HRTEM measurements. The cubic phase with a = 10.540 A was the only phase observed. The average crystalline sizes and the widths of the grain size distribution curves were determined to be 27.2, 18.7 and 9.7 nm, respectively. The spectroscopic properties of the Er 2 O 3 nano-powder were studied by measuring the luminescence, decay and rise patterns under 808 and 975 nm diode laser excitations. A peculiar effect of the pressure was observed since an optically active ion (Er) is part of the complex and not a dopant. A broad band of the white light emission combined with blue, green and red up-conversion emission bands of Er 3+ ions were observed at 0.03 mbar pressure under both excitation wavelengths. Only, an intense broad band white light emission was observed from these nanocrystals at atmospheric pressure. Rising patterns show that the white light intensity reaches its maximum value more rapidly under 975 nm excitation although it decays slower than that of 808 nm excitation. The color quality parameters such as the color coordinate (CRI), correlated color temperature and the color rendering index were found to vary with both the excitation wavelength and the ambient pressure indicating that these nanocrystals could be considered good white light emitting source under the infrared excitations.

Yttria (Y 2 O 3 ) nano-powders doped with various concentrations of Er 3+ were synthesized using thermal decomposition method and annealed at 800 °C. Annealed powders were doped in PMMA with 2.0 weight% of MMA by free radical polymerization. The crystalline structures of the powders and those embedded in PMMA matrix were identified as the cubic (BCC) Y 2 O 3 phase using X-ray diffraction technique. According to the Scherer equation, the average crystallite sizes were found to be 32 ±3 nm and 20 ±3 nm for the powders and those embedded in the PMMA matrix, respectively. The transmission electron micrographs of samples were also taken and found to be consistent with the results obtained using X-ray diffraction measurements. Upconversion emission spectra of the Y 2 O 3 :Er 3+ powders were measured in the 400–850 nm wavelength range under the excitation of a diode laser operated at 975 nm and, compared with the results obtained for Y 2 O 3 :Er 3+ in PMMA. Spectral profiles of the emissions remain unchanged for different Er 3+ concentrations and excitation powers. The doping of the nanopowders into the PMMA matrix did also not change the spectral profile, but only enhanced the intensity of the upconversion emission. Measurements of the emission intensity dependence on the pumping power under atmospheric conditions were performed to provide a possible explanation for the mechanisms responsible for the upconversion luminescence. Relative intensities for all the luminescence transitions were found to vary with Er 3+ concentration resulting in the possible control of both color tuning and the color quality parameters.

We have studied nanophosphors of yttrium silicate (YSO) undoped and doped with different concentration of ytterbium (Yb 3+ ) synthesized by using the sol-gel method. Structural and luminescence properties of the nanophosphors were studied experimentally by using different analytical techniques. For the structural analysis, we performed X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectrometry (EDS) measurements. Upconversion (UC) and the white light (WL) emission properties were investigated by using the near infrared cw laser excitation of 975 nm. The spectral properties have been found to depend on several physical parameters.

In 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.

This paper presents a detailed spectroscopic investigation of zinc tellurite glasses with the compositions (0.80-x-y) TeO2+(0.20) ZnO+xEr2O3+yYb2O3 (x=0, y=0; x=0.004, y=0; x=0, y=0.05 and x=0.004, y=0.05 per moles). The samples were synthesized by the conventional melt quenching method. The optical absorption and emission measurements were conducted at room temperature to determine the spectral properties of lanthanides doped zinc tellurite glasses and, to study the energy transfer processes between dopant lanthanide ions. The band gap energies for both direct and indirect possible transitions and the Urbach energies were measured from the absorption spectra. The absorption spectra of the samples were analyzed by using the Judd-Ofelt approach. The effect of the ytterbium ions on the emission properties of erbium ions was investigated and the energy transfer processes between dopant ions were studied by measuring the up-conversion emission properties of the materials. The color quality parameters of obtained visible up-conversion emission were also determined as well as possibility of using the Er(3+) glasses as erbium doped fiber amplifiers at 1.55μm in infrared emission region.

We report on the role played by dopant ions to create broadband white light emission from metal oxide nano-powders. Y 2 O 3 was doped with different rare earth ions (Nd 3+ , Er 3+ , Yb 3+ ) and Cr 3+ ion to investigate their role on the production of white light emission. We have determined that the dopant ions have a facilitator but not a decisive role on the production of the white light emission by doing measurements such as reflectance, white light emission, excitation power dependency and color quality parameters. All measurements showed that the production of white light does not depend on the amount and the type of the dopant ions.

In 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)-phthalocyaninato}zinc(II) (1b), was synthesized and then characterized by applying different spectroscopic methods, such as FT-IR, 1H NMR and MALDI-TOF spectroscopy. According to the literature, {2(3),9(10),16(17),23(24)-tetrakis-(3,5-bis(trifluoromethyl)phenoxy)-phthalocyaninato}zin(II) (1a), {2,3,9,10,16,17,23,24-octakis-(3,5-bis(trifluoromethyl)phenoxy)-phthalocyaninato}zinc(II) (2a) and 2(3)-[(4-nitrophenyl)ethynyl]-{9,10,16,17,23,24-hexakis-(3,5-bis(trifluoromethyl)phenoxy)-phthalocyaninato}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 β 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.

In this work, new non-symmetrical, peripherally substituted metallophthalocyanines, namely 2(3)-[(4-nitrophenyl)ethynyl]-{9,10,16,17,23,24-hexakis-(4-(trifluoromethoxy)phenoxy)-phthalocyaninato}zinc (1b) and 2(3)-[(4-nitrophenyl)ethynyl]-{9(10),16(17),23(24)-tris-(4-(trifluoromethoxy)phenoxy)-phthalocyaninato}zinc (2b) were prepared. Structural elucidation of the novel zinc phthalocyanines was carried out with well-known spectroscopic methods. The solubility of the phthalocyanines was investigated in organic solvents like tetrahydrofuran, dichloromethane, and dimethyl sulfoxide. The effect of concentration on aggregation behavior of the resulting phthalocyanines (1b and 2b) was examined in a wide area ranging from 4 × 10−6 to 14 × 10−6 M in tetrahydrofuran. Aggregation properties of the macrocyclic molecules (1b and 2b) were also investigated in many organic solvents. Based on the data existing in the literature, peripherally octa- and tetra-substituted zinc phthalocyanines (1a and 2a) with 4-(trifluoromethoxy)phenoxy moieties were synthesized. Optical limiting and the third-order nonlinear properties of symmetrically and non-symmetrically substituted phthalocyanines were determined and compared with each other.

Er3+ and Er3+/Yb3+ doped zinc tellurite (ZnO/TeO2) glasses were prepared using melt quenching technique. Spectroscopic properties of the glasses were studied by absorption spectroscopy, luminescence spectroscopy, and color chromaticity coordinates (CIE-1931) measurements. Upconverted-emission intensities and the CIE-1931 coordinates were strongly affected by the presence of Yb3+ ion, as well as the excitation power density of 975 nm laser light. Effect of temperature on green upconverted-emissions from two thermally coupled H-2(11/2) and S-4(3/2) levels of Er3+ ions were measured and fluorescence intensity ratio technique was applied to investigate the temperature sensing properties. High sensitivity and short response time properties make ZnO/TeO2 glasses a very good candidate for non-contact optical temperature sensor applications. The maximum sensitivity of the glasses doped with Er3+ and Er3+/Yb3+ were found to be 72 x 10(-4) K-1 and 120 x 10(-4) K-1 at 429 K, respectively which are much higher than previously reported temperature sensors based on Er3+ ion doped materials. Hence, Er3+/Yb3+ doped zinc-tellurite glass can be more suitable than that of doped with Er3+ ions only for color tunable solid-state lighting and non-contact optical thermometry applications. (C) 2018 Elsevier B.V. All rights reserved.

Y2O3 nanocrystals triply doped with Yb3+, Er3+, Tm3+ ions were synthesized via alginic acid-assisted gelation using thermal decomposition method and annealed at 800 °C for 24 h. Nanopowders were embedded into PMMA matrix via free-radical polymerization in an ultrasonic bath. X-ray diffraction and transmission electron microscopy measurements have shown that the crystal grain sizes decreased significantly with the narrow size distributions of the nanocrystals in PMMA matrix. A diode laser at 975 nm was used to measure the upconversion luminescence of the annealed nanopowders and those embedded in PMMA between the 400–850 nm wavelength region. The Er3+ concentration and the excitation power density dependencies of the relative intensities for red, green and blue upconversion luminescence in the nanopowder and PMMA nanocomposites are found to be different. The measured CIE-1931 color coordinates of the upconversion luminescence in PMMA nanocomposites show appreciable color stability under different excitation power densities, which is required for potential applications in the field of photonics.

Cooperative emission has been observed in sol–gel derived nano-powders doped with yitterbium ions when excited with the 950 nm emission of a laser diode. Measurements of the sample emission intensity dependence on the pumping power under atmospheric pressure condition were performed to provide possibly an explanation for the cooperative emission mechanism. The emission intensities of each nano-powder increased when the pressure was increased from 0.01 mbar to 1 atm with the observation of the bright blue emission. When the powders were subject to very low pressure at 0.01 mbar, the blue emission intensities decreased and green emission intensities increased. The CIE coordinates (x, y) for YSY1 were found to be (0.187, 0.196) under 1 atm. with a color rendering index (CRI) of 67 under the 950 nm laser diode excitation.

Bright white up conversion emission has been observed in sol–gel derived Yb3+/Er3+/Tm3+: Y2SiO5 nanocrystalline powders when excited with the 950 nm emission of a laser diode. Measurements of the sample emission intensity dependence on the pumping power were performed to explain the up conversion mechanism. The CIE chromaticity coordinates (x, y) for white emission in X2–Y2SiO5 nanocrystalline form were found to be (0.334, 0.332) under 950 nm laser diode excitation.

We 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.

We report the generation of wideband white light with a spectrum ranging from 400 to 800 nm obtained from sol–gel derived γ-Y2Si2O7 nano powders with average particle size under 100 nm when excited with the 803.5 nm emission of a laser diode. The white light intensity was found to increase with decreasing environment pressure and increasing laser pumping power. The International Commission on Illumination coordinates were found to be x = 0.3408 and y = 0.3100 under 803.5 nm excitation. These values lie in the yellowish region and correspond to color temperature values of 5030 K with a color rendering index of 85. The illuminance value was found to be 1456 lux.

In this work, Yb3+∕Er3+ co-doped and Yb3+∕Tm3+∕Er3+ tri-doped La2Ti2O7 phosphors were synthesized by solid-state reaction method. The phases of the powders were identified using the X-Ray Diffraction (XRD) technique. The purity of the La2Ti2O7 phosphors were tested by energy dispersive spectroscopy (EDS). The photoluminescence properties of La2Ti2O7 phosphors were investigated in the range of 400–850 nm wavelength under 975 nm laser excitation at room temperature. Presence of Tm3+ ion in the tri-doped powder effects the UC-emission processes observed in the powders co-doped with Yb3+∕Er3+.

Trivalent rare earth ions doped materials can convert near infrared photons to different visible emissions and Yb3+ rare earth ions have only two levels of 2F7/2 and 2F5/2 in the near infrared region. Yb3+ ions are generally used as sensitizer to obtain high emissions from other rare earths by using ∼975 nm laser and the near infrared photon energy can be transferred from Yb3+ to other ions. The energy level 4F3/2 of Nd3+ is little higher than the 2F5/2 level of Yb3+, so Nd3+ emission may be sensitized by energy transfer from Yb3+ ion. In this work, we studied the luminescence properties of Nd3+/Yb3+ co-doped yttrium silicate (Y2O3:SiO2) nanopowder with a 975 nm diode laser excitation. The emission properties and spectral changes were analyzed at atmospheric pressure and vacuum. The decay and rise patterns were carried out under vacuum (0.01 mbar) and atmospheric pressures.

Thermal decomposition technique was employed to synthesize of phosphors of yttria (Y2O3) doped with erbium (Er3+) ions. After the synthesized procedure, the nano-sized crystalline powders were annealed at 800oC for 24 h. Annealed powders were embedded in poly(methyl methacrylate) (PMMA) by free radical polymerization to fabricate nanocomposite polymer materials. The crystalline structure of the powder and doped PMMA nanocomposite samples were determined using X-ray diffraction technique. Scherrer’s equation and the FW1/5/4/5M method were used to determine average crystalline size and grain size distributions, respectively. The spectroscopic properties of the powders and doped PMMA nanocomposites were studied by measuring the upconversion emission spectra under near-infrared laser excitation at room temperature. The laser-induced photo thermal behaviors of Er3+:Y2O3 nano-powders and doped PMMA nanocomposite were investigated using the fluorescence intensity ratio (FIR) technique.Thermal decomposition technique was employed to synthesize of phosphors of yttria (Y2O3) doped with erbium (Er3+) ions. After the synthesized procedure, the nano-sized crystalline powders were annealed at 800oC for 24 h. Annealed powders were embedded in poly(methyl methacrylate) (PMMA) by free radical polymerization to fabricate nanocomposite polymer materials. The crystalline structure of the powder and doped PMMA nanocomposite samples were determined using X-ray diffraction technique. Scherrer’s equation and the FW1/5/4/5M method were used to determine average crystalline size and grain size distributions, respectively. The spectroscopic properties of the powders and doped PMMA nanocomposites were studied by measuring the upconversion emission spectra under near-infrared laser excitation at room temperature. The laser-induced photo thermal behaviors of Er3+:Y2O3 nano-powders and doped PMMA nanocomposite were investigated using the fluorescence intensity ratio (FIR) technique.

Y2O3 nanocrystalline phosphors doped with Er3+/Yb3+/Tm3+ ions were prepared using thermal decomposition technique at 500 degrees C. Pure cubic phase of Y2O3 with an average crystallite size similar to 29 +/- 4 nm was determined from x-ray diffraction and high-resolution transmission electron microscope measurements. Their upconversion luminescence spectra were measured under 975-nm laser diode excitation at room temperature. A bright blue emission was simultaneously observed at 480 nm due to the (1)G(4) -> H-3(6) transition of Tm3+ ions, with the green (550 nm) and red (670 nm) emissions due to the H-2(11/2), S-4(3/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2) transitions of Er3+ ions, respectively. Relative emission intensities of these colors were significantly affected by the Er3+ concentration as well as the excitation power density of 975-nm laser light. Color quality parameters and the color tuning abilities were determined from the Commission International de I'Echairage 1931 chromaticity diagram analysis, color rendering index, and their correlated color temperature values. A careful color tuning from cool to warm white light in Y2O3:Er3+/Yb3+/Tm3+ phosphors was achieved by controlling both the doping concentration of Er3+ ions and the excitation power density of the 975-nm laser light. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)

We present the production of white light emission with the monochromatic infrared light excitation of erbium oxide (Er2O3), ytterbium oxide (Yb2O3), and neodymium oxide (Nd2O3) nano-crystalline powders at atmospheric (1 Atm) and vacuum (0.03 mbar) pressures. We synthesized the rare-earth oxide nano-crystalline powders by thermal decomposition technique. The crystal structure and morphological properties were determined by X-Ray Diffraction (XRD) and high-resolution transmission electron microscope (HRTEM). The optical region emission spectra of rare earth oxide powders measured in the 400–900 nm wavelength region at 1 atm and 0.03 mbar pressure. Luminescence spectra upon 808 nm, and/or 975 nm diode laser excitation were carried out at room temperature. The white light (WL) emission properties, color quality parameters were investigated at atmospheric and vacuum pressures. Synthesis Procedure We synthesized the rare-earth oxide nano-crystalline powders by thermal decomposition technique. For synthesis, rare-earth nitrate salts were used as precursors. Alginic acid sodium salt was used for gelation [1]. Details on the preparation method were described in some previous works [2, 3]. Results and Discussion Structural and Morphological Properties X-ray diffraction (XRD) patterns were collected by Bruker AXS D8 diffractometer. According to JCPDS (Joint Committee for Powder Diffraction Data), the peak positions observed in the XRD pattern of Yb2O3, Nd2O3, and Er2O3 powders corresponded well with Card# 01-074-1981, Card# 01-070-2152, Card# 01-074-1983, respectively. The peak positions of Nd2O3 powder correspond well with Nd2O2(CO3) crystalline phase is originated from the combination of alginic acid and nitrate salt of neodymium during the synthesis process [3, 4]. The morphological properties were investigated by a Jeol 2100F model high resolution transmission electron microscope (HRTEM). The particle sizes are in good agreement with the results obtained from XRD measurements. Spectroscopic Measurements The optical region emission spectra upon 808 nm, and/or 975 nm diode laser excitation were carried out at room temperature. For vacuum pressure, the samples were mounted in a closed chamber pumped by a vacuum pump. Both at vacuum and atmospheric pressures, bright white light was observed under 808 nm laser excitation for Nd2O3, Er2O3 nano powder, and under 975 nm laser excitation for Yb2O3, Er2O3. We also observed some additional overlapping anti-Stokes type emissions at vacuum pressure. The white emission behavior of Nd2O3 at two different pressures are given as an example in Fig. 1.

In this work, (90-x-y)TeO2-10GeO2-(x)Tm2O3-(y)Er2O3 composition of germano-tellurite glasses were synthesized by traditional melting and quenching technique and the spectroscopic properties of synthesized glasses were investigated. The values of Judd-Ofelt (JO) intensity parameters (Ωt(t = 2, 4, 6)), spontaneous transition probabilities (Α), branching ratios (β) and radiative lifetimes (τR) were obtained by using the Judd-Ofelt (JO) theory and absorption spectra. The stimulated emission cross-sections of TG:Tm and TG:Er glasses in 1.47 μm and 1.53 μm wavelength regions were calculated by Fuchtbauer-Ladenburg formula and McCumber theory, respectively. The gain bandwidth-cross section product of TGTm0.5 and TGEr1 glasses was found to be 445.76 × 10−28 cm3 and 849 × 10−28 cm3, respectively. The fluorescence lifetime measurements were done for the 3F4 and 4I13/2 levels to compare with the radiative lifetimes. These results suggest that the TG:Tm and TG:Er studied glasses can potentially possess wider gain bandwidth for S-band amplifier and broadband optical amplifier WDM at 1.53 μm, respectively.

Among 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.

[No abstract available]

We report the luminescence properties of undoped and 10% Yb3+-doped Y2Si2O7 nanopowders under the infrared excitation of 975-nm laser diode. A broadband white light (WL) emission is observed in the undoped powder, and its intensity becomes stronger with increasing excitation power. A blue emission centered at ∼475 nm is observed below the excitation power of ∼2 W in the Yb3+-doped sample. The blue emission intensity dependence on the excitation power suggests that this emission is a two-photon absorption process known as the cooperative luminescence of Yb3+ ions. When the excitation power is increased above 2 W, a broadband “white” emission extending from blue into the near infrared appears while the blue cooperative emission band of Yb3+ ions disappears. The excitation power dependence of the WL intensity at 758 nm is due to a multiphoton process that may be attributed to the thermal radiation mechanism. The International Commission on Illumination coordinates (x,y) for the WL emission in the Yb3+-doped Y2Si2O7 nanocrystalline sample is found to be (0.4503, 0.3999) and (0.5035, 0.4096) for 2.005- and 3.68-W excitation powers, respectively. These values lie in the yellowish region and correspond to the color temperature value of 5030 K, with a color rendering index of 85.