Active Ion Concentration Research Articles

An Ecological and Identification Study for Algae in Groundwater of Selected Area in Tikrit city and It’s Surrounding Area

The present study is carried out to identify the algae in the groundwater of the three areas of Tikrit city, including (the center of Tikrit , the region of AL-Jazira , Awainat village) by nine wells, a depths ranged between 9 meter at well 8 and 110 meter at wells 3 and 5 . And examined the environmental characteristics of physical, chemical and biological factors during the study period from September 2009 to June 2010. It is obtained that wells in the study area is lower alkalinity, average it ranged (6.448-7.418). It was noted that the values of the dissolved oxygen are few and almost non-existent in some cases it ranged between (6.5-6.3)mg/l , analysis of biological oxygen demand refers to wells water (clean- very clean) average it ranged between (1420-1990)mg/l . Reason of groundwater very hardness due to geological factors of study area, which was mostly the result of ion bicarbonates, and recorded rate values of sulphates (258.2-406.2)mg/l. As for plant nutrients, the values of silica were relatively high (7.07-10.935)mg/l .While the concentration of active nitrite ions and phosphate, were random during the study period, it ranged between(0.128-2.979),(0.564-2.065)mg/l respectively. The biological side of this involved the identifying of algal in the studies wells. Diatoms formed the highest majority of plan plankton in the study area, the ratio of diatoms was 48%, then the Chlorophyceae was 32.4%, and the ratio of Cyanophyceae was 14.2%, and lastly the Euglenophyceae was 5.1%. Chlorophyll values were relatively high , the values of chlorophyll a was lower from chlorophyll b , c values .That’s indicate dominated species of organisms in the study area. The results indicated analysis to limit many effect factors on concentration of chlorophyll in algae in the study area

Synthesis and luminescence properties of ZnAl2O4:RE3+ (RE = Eu, Sm) phosphors

ZnAl2O4:RE3+ (RE = Eu or Sm) phosphor powders were synthesized with different concentrations of activator ions by using the conventional solid-state reaction method. The effects of the concentration of activator ions on the structural, morphological, and luminescent properties of zinc aluminate phosphors were investigated. The X-ray diffraction patterns revealed that the phosphors synthesized with different concentrations of activator ions showed mixed phases of ZnAl2O4, ZnO, and Al2O3. The crystallite size was estimated using the Scherrer formula, and the maximum size was obtained for 0.20 mol of Eu3+ions. The emission spectra of of Eu3+-doped ZnAl2O4 phosphors under excitation at 303 nm exhibited one intense green band at approximately 520 nm and three weak bands centered at 590, 621, and 701 nm, respectively. The intensity of all the emission bands reached a maximum for 0.05 mol of Eu3+ ions. For the Sm3+-doped ZnAl2O4 phosphors, a broad emission band peak at 526 nm and several weak lines in the range 470–700 nm were observed. The results suggest that the luminescent intensity of the phosphors can be enhanced by controlling the amount of activator ions incorporated into the host lattice.

Local Environments of Dilute Activator Ions in the Solid-State Lighting Phosphor Y3–xCexAl5O12

The oxide garnet Y3Al5O12 (YAG), when substituted with a few percent of the activator ion Ce3+ to replace Y3+, is a luminescent material that is nearly ideal for phosphor-converted solid-state white lighting. The local environments of the small number of substituted Ce3+ ions are known to critically influence the optical properties of the phosphor. Using a combination of powerful experimental methods, the nature of these local environments is determined and is correlated with the macroscopic luminescent properties of Ce-substituted YAG. The rigidity of the garnet structure is established and is shown to play a key role in the high quantum yield and in the resistance toward thermal quenching of luminescence. Local structural probes reveal compression of the Ce3+ local environments by the rigid YAG structure, which gives rise to the unusually large crystal-field splitting, and hence yellow emission. Effective design rules for finding new phosphor materials inferred from the results establish that efficient phosphors require rigid, highly three-dimensionally connected host structures with simple compositions that manifest a low number of phonon modes, and low activator ion concentrations to avoid quenching.

A powerful broadband Ho-doped fiber source in the 2 μm region

A broadband continuous wave source of amplified spontaneous emission based on heavily Ho-doped fiber is presented. Maximum output power up to 273 mW was obtained, central wavelength varied from 2.025 to 2.05 μm and full width at half maximum of 54 nm was measured. The influence of the active ion concentration and fiber length on the emission spectrum was studied.

Synthesis and photoluminescent properties of LaPO4:RE3+ (RE = Tb, Ce) phosphors

LaPO4:RE3+(RE = Tb or Ce) phosphor powders were synthesized with different activator ion concentrations by using the solid-state reaction method. The effect of the activator ion concentration on the structural, morphological, and luminescent properties of lanthanide-phosphate phosphors was investigated. XRD patterns revealed that the synthesized phosphors with different activator ions showed a monoclinic structure with a main (120) diffraction peak for both activator ions. The crystallite size was estimated by using the Scherrer formula, and the maximum size was obtained at 0.01 mol of Ce3+ions and at 0 mol of Tb3+ions. The emission spectra of Tb3+-doped LaPO4 phosphors under excitation at 210 nm exhibited one intense green band at 548 nm and three weak lines peaking at 493, 590, and 640 nm, respectively. The intensities of all the emission bands reached their maxima at 0.10 mol of Tb3+ ions. As for the Ce3+-doped LaPO4 phosphors, two strong emission bands were observed, one each at 324 and 340 nm, and the energy difference between the two peaks was 0.18 eV. These results suggest that multicolor emission can be realized by controlling the concentrations of the activator ions incorporated into the host lattice.

Single-nanocrystal sensitivity achieved by enhanced upconversion luminescence

Upconversion nanocrystals convert infrared radiation to visible luminescence, and are promising for applications in biodetection, bioimaging, solar cells and three-dimensional display technologies. Although the design of suitable nanocrystals has improved the performance of upconversion nanocrystals, their emission brightness is limited by the low doping concentration of activator ions needed to avoid the luminescence quenching that occurs at high concentrations. Here, we demonstrate that high excitation irradiance can alleviate concentration quenching in upconversion luminescence when combined with higher activator concentration, which can be increased from 0.5 mol% to 8 mol% Tm(3+) in NaYF₄. This leads to significantly enhanced luminescence signals, by up to a factor of 70. By using such bright nanocrystals, we demonstrate remote tracking of a single nanocrystal with a microstructured optical-fibre dip sensor. This represents a sensitivity improvement of three orders of magnitude over benchmark nanocrystals such as quantum dots.

The role of activator concentration and precipitate formation on optical and dosimetric properties of KCl:Eu2+ storage phosphor detectors

The activator ion (Eu(2+) in KCl:Eu(2+)) plays an important role in the photostimulated luminescence (PSL) mechanism of storage phosphor radiation detectors. In order to design an accurate, effective, and robust detector, it is important to understand how the activator ion concentration affects the structure and, consequently, radiation detection properties of KCl:Eu(2+). Potassium chloride pellets were fabricated with various amounts of europium dopant (0.01-5.0 mol.% Eu(2+)). Clinical radiation doses were given with a 6 MV linear accelerator. Radiation doses larger than 100 Gy were given with a (137)Cs irradiator. Dose response curves, radiation hardness, and temporal signal stability were measured using a laboratory PSL readout system. The crystal structure of the material was studied using x ray diffraction and luminescence spectroscopy. The most intense PSL signal was from samples with 1.0 mol.% Eu. However, samples with concentrations higher than 0.05 mol.% Eu exhibited significant degradation in PSL intensity for cumulated doses larger than 3000 Gy. Structural and luminescence spectroscopy showed clear evidence of precipitate phases within the KCl lattice, especially for high activator concentrations. Analysis of PL emission spectra showed that interactions between Eu-Vc dipoles and Eu-Vc trimers could explain trends in PSL sensitivity and radiation hardness observations. The concentration of the activator ion (Eu(2+)) significantly affects radiation detection properties of the storage phosphor KCl:Eu(2+). An activator concentration between 0.01 and 0.05 mol.% Eu in KCl:Eu(2+) storage phosphor detectors is recommended for linear dose response, good PSL sensitivity, predictable temporal stability, and high reusability for megavoltage radiation detection.

Color tunable green–yellow–orange–red Er3+/Eu3+-codoped PbGeO3:PbF2:CdF2 glass phosphor for application in white-LED technology

Color tunable wide gamut light covering the greenish, yellow–green, yellow, orange, and reddish tone chromaticity region in Er3+/Eu3+-codoped lead–cadmium–germanate PbGeO3:PbF2:CdF2 glass phosphor is presented. The phosphors were synthesized, and their light emission properties examined under UV and blue LED excitation. Luminescence emission around 525, 550, 590, 610, and 660nm was obtained and analyzed as a function of Eu/Er concentration, excitation wavelength, and glass host composition. The color tunability was actually obtained via proper combination of Er3+ and Eu3+ active ions concentration. The combination of the emission tone with blue LEDs in the region of 400–460nm, yielded a mixture of light with color in the white-light region presenting a color correlated temperature in the range of 2000–4000K. Results indicate that the color-tunable fluorolead germanate erbium/europium co-doped glass phosphor herein reported is a promising novel contender for application in LED-based solid-state illumination technology

Random lasing in a nanocomposite medium

The characteristics of a random laser based on a nanocomposite medium consisting of a transparent dielectric and scattering doped nanocrystals are calculated. It is proposed to use ytterbium laser media with a high concentration of active ions as nanocrystals and to use gases, liquids, or solid dielectrics with a refractive index lower than that of nanocrystals as dielectric matrices for nanocrystals. Based on the concept of nonresonant distributed feedback due to the Rayleigh scattering, an expression is obtained for the minimum length of a nanocomposite laser medium at which the random lasing threshold is overcome. Expressions are found for the critical (maximum) and the optimal size of nanocrystals, as well as for the optimal relative refractive index of nanocompositesthat corresponds not only to the maximum gain but also to the minimum of the medium threshold length at the optimal size of nanocrystals. It is shown that the optimal relative refractive index of a nanocomposite increases with increasing pump level, but is independent of the other nanocomposite parameters.

Plasma properties in a large-volume, cylindrical and asymmetric radio-frequency capacitively coupled industrial-prototype reactor

We have developed a large-volume low-pressure cylindrical plasma reactor with a size that matches industrial reactors for treatment of textiles. It was shown that it efficiently produces plasmas with only a small increase in power as compared with a similar reactor with 50 times smaller volume. Plasma generated at 13.56 MHz was stable from transition to streamers and capable of long-term continuous operation. An industrial-scale asymmetric cylindrical reactor of simple design and construction enabled good control over a wide range of active plasma species and ion concentrations. Detailed characterization of the discharge was performed using derivative, Langmuir and catalytic probes which enabled determination of the optimal sets of plasma parameters necessary for successful industry implementation and process control. Since neutral atomic oxygen plays a major role in many of the material processing applications, its spatial profile was measured using nickel catalytic probe over a wide range of plasma parameters. The spatial profiles show diffusion profiles with particle production close to the powered electrode and significant wall losses due to surface recombination. Oxygen atom densities range from 1019 m−3 near the powered electrode to 1017 m−3 near the wall. The concentrations of ions at the same time are changing from 1016 to the 1015 m−3 at the grounded chamber wall.

Optical properties and generation of white light in Dy3+-doped lead phosphate glasses

Dy3+-doped lead phosphate (PbPKANDy: P2O5+K2O+Al2O3+PbO+Na2O+Dy2O3) glasses were prepared by melt quenching technique and their optical properties have been studied. Judd-Ofelt parameters have been evaluated for 1.0mol% Dy2O3-doped lead phosphate glass and inturn derived radiative properties for excited luminescent levels of Dy3+ ions. The yellow-to-blue emission intensity ratios and CIE chromaticity coordinates were calculated which have been used to evaluate white light emission as a function of the activator (Dy3+) ion concentration. The observed non-exponential decay nature and quenching of lifetime for higher Dy3+ ion concentration (≥1.0mol%) have been attributed due to energy transfer of dipole–dipole type between excited and unexcited Dy3+ ions. The PbPKANDy glasses exhibit better luminescence properties which are suitable for generation of white light.

Spectroscopic study and white-light simulation using praseodymium-doped fluorogermanate glass as single phosphor for white LEDs

Praseodymium-doped fluorogermanate 60PbGeO3–20PbF2–20CdF2 nano-structured phosphors were synthesized by thermal treatment of precursor glasses. Luminescence features of praseodymium ions incorporated into low-phonon-energy PbF2 nanocrystals dispersed in the fluorogermanate glass matrix was evaluated. The luminescence spectra exhibited visible emission signals peaked at 490, 525, 613, and 643nm. White-light emission was observed in praeodymium single-doped phosphor excited using a LED at 460nm. The dependence of the luminescence emission intensity upon annealing temperature, and rare-earth concentration was also evaluated. The results indicated the existence of optimum annealing temperature and activator ion concentration to obtain intense emission light with CIE 1931 chromaticity coordinates within the white-light boundary region. Results suggest that the novel nanocomposite glass material herein reported is a promising phosphor for white-light LED applications.

Photoluminescence properties of a novel orange red emitting Sr4Al14O25:Sm3+ phosphor and PL enhancement by Bi3+ co-doping

A novel orange red emitting Sr4Al14O25:Sm3+ and Sr4Al14O25:Sm3+, M3+ (M=Bi, Dy, Nd) phosphors were synthesized by high temperature solid state reaction method. The phosphor samples were characterized by X-ray diffraction and Scanning Electron Microscopy. UV–visible absorption, photoluminescence emission and excitation spectra were investigated for the phosphor with various doped concentrations of Sm3+ and Bi3+ ions and different amount of H3BO3 as a flux. The emission intensity of Sm3+ ions in the Sr4Al14O25 host largely enhanced with the amount of flux, concentration of activator (Sm3+) ion and co-activator (Bi3+) ion. The maximum intensity was observed in the phosphor prepared using 40mol% H3BO3 as a flux and 2at.% Sm3+ ions as an activator sintered at 1350°C. Addition of 2at.% Bi3+ ion drastically enhanced the emission intensity; the increase by Dy3+ ion was not so pronounced but Nd3+ ion largely suppressed the emission intensity. The increase of emission intensity by Bi3+ ion addition was explained on the basis of higher absorption of excitation energy by Bi3+ ions and efficient energy transfer from Bi3+ to Sm3+ emission center.

Radiation Induced Absorption in Rare Earth Doped Optical Fibers

We have investigated the radiation induced absorption (RIA) of optical fibers with high active ion concentration. Comparing our results to the literature leads us to the conclusion that RIA appears to be only weakly dependent on the rare earth dopant concentration. Instead, co-dopants like Al, Ge, or P and manufacturing processes seem to play the major role for the radiation sensitivity. It is also observed that different types of irradiation cause very similar RIA at the same dose applied, with the exception at very high dose rates. It has been studied how RIA can be efficiently reduced via moderate heating. Recovery of up to 70% of the original transmission has been reached after annealing at 450 K. We conclude that radiation induced color centers have weak binding energies between 20 and 40 meV. This suggests that annealing could become a key strategy for an improved survival of rare earth doped fibers in radiative environments, opening up new possibilities for long-term missions in space.

Emission properties of polymer composites doped with Er3+:Y2O3 nanopowders

In this work we report the recent results of our investigation on visible emission properties of the PMMA-based polymer nanocomposites doped with Er3+:Y2O3 nanopowders. The set of active nanopowders, and polymer films, differing in active ions concentration, was characterized with respect of their luminescent properties in the green spectral range, available to a limited extent for semiconductor lasers. In particular – the concentration dependent emission spectra and fluorescence dynamics profiles were measured under direct (single photon) and up-converted excitation, enabling the comparison of luminescent properties of developed nanocomposite materials and original nanopowders, optimization of erbium dopant concentration as well as discussion of excitation mechanisms and analysis of the efficiency of depopulation processes.

Luminescent features of sol–gel derived rare-earth multi-doped oxyfluoride nano-structured phosphors for white LED application

Rare-earth doped oxyfluoride 75SiO 2:25PbF 2 nano-structured phosphors for white-light-emitting diodes were synthesized by thermal treatment of precursor sol–gel derived glasses. Room temperature luminescence features of Eu 3+, Sm 3+, Tb 3+, Eu 3+/Tb 3+, and Sm 3+/Tb 3+ ions incorporated into low-phonon-energy PbF 2 nanocrystals dispersed in the aluminosilicate glass matrix and excited with UV light emitting diode were investigated. The luminescence spectra exhibited strong emission signals in the red (600, 610, 625, and 646 nm), green (548 and 560 nm), and blue (485 nm) wavelength regions. White-light emission was observed in Sm/Tb and Eu/Tb double-doped activated phosphors employing UV-LED excitation at 395 nm. The dependence of the luminescence emission intensities upon annealing temperature and rare-earth concentration was also examined. The results indicated that there exist optimum annealing temperature and activator ion concentration in order to obtain intense visible emission light with high color rendering index. The study suggests that the nanocomposite phosphor based upon 75SiO 2:25PbF 2 host herein reported is a promising contender for white-light LED applications.

Energy transfer between Yb3+ and Er3+ ions in an Er,Yb:YAl3(BO3)4 crystal

The electron-excitation energy transfer between Er3+ and Yb3+ ions in Er,Yb:YAl3(BO3)4 crystals has been investigated. Crystals with different concentrations of active ions have been grown, and their luminescence decay kinetics in the spectral range near 1 μm have been experimentally measured. The energy-transfer microparameters have been calculated. It is shown that, to correctly describe the energy transfer in Er,Yb:YAl3(BO3)4 crystals, one must take into account the interactions of higher orders than dipole-dipole interactions.

Temperature sensor based on the Er 3+ green upconverted emission in a fluorotellurite glass

The temperature dependence of the green upconverted emission from the two thermally coupled 2H 11/2 and 4S 3/2 levels of the Er 3+ ion in a fluorotellurite glass has been analyzed as a function of the optically active ion concentration in order to check its availability as a temperature sensor. The infrared-to-green upconverted emission have been observed by the naked eyes after a cw laser diode excitation at 800 nm. The fluorescence intensity ratio between the thermally coupled emitting levels as well as the temperature sensitivity has been experimentally obtained up to 540 K. A better behaviour as a temperature sensor has been obtained for the less Er 3+ concentrated glass with a maximum sensitivity of 54 × 10 −4 K −1 at 540 K, one of the highest found in rare-earth doped transparent materials.

A practical technique for measuring human biofluid conductivity using high gain-frequency characteristics

Currently, the study of ion composition and performance in human biofluids plays an important role in biomedical engineering research and technology. This field may become universal for human diagnostics; it allows early detection of different diseases in humans by measuring changes in ion behaviour in human biofluids. Practical experiments were conducted to analyse the liquid composite electrolyte conductivity in an alternating electric current field. These experiments allow the contribution of separate types of ions to the overall conductivity to be estimated. The method of estimating the concentration of active ions contained in biofluids is also introduced; it illustrates the possibility of performing qualitative and quantitative analysis over a wide range of concentrations and compositions. The authors present a procedure to determine the concentration of active liquid ions based on conductivity gain-frequency characteristic curve tracing. The experimental results validate the practical use of the proposed method. The results of this research are promising, and further investigation is required to further improve the method.

Luminescence characteristics of Lu 0.8Sc 0.2BO 3:RE 3+ (RE = Eu, Tb) polycrystalline powders

Lu 0.8Sc 0.2BO 3:RE 3+ (RE = Eu, Tb) polycrystalline powders were prepared by high temperature solid state reaction method. The X-ray diffraction measurements confirmed that the doped materials were all monophasic solid solution powders. The influences of activator ion (Eu 3+ or Tb 3+) concentration on the photoluminescence and radioluminescence characteristics were investigated and discussed. The Tb 3+ doped materials showed excellent light yields than Eu 3+ doped materials under X-ray excitation. The fluorescence decay times of the optimal materials excited by UV were measured. Their defect properties were studied by thermoluminescence (TL) as a function of temperature (300–600 K) and the corresponding trap depth, frequency factor and detrapping time were theoretically calculated. The Eu 3+ and Tb 3+ ions were the unique recombination centers in corresponding samples. In addition, considering their attracting luminescence properties and excellent physical properties (high-density and non-hygroscope), the Lu 0.8Sc 0.2BO 3:RE 3+ (RE = Eu, Tb) can be used for X-ray medical imaging system, hence their crystal growth and characterizations deserve further investigation.