Study of Temperature Behavior of Luminescence Emission of LaVO4 and La1-xEuxVO4 Powders

2015 ◽  
Vol 230 ◽  
pp. 153-159 ◽  
Author(s):  
Oksana Chukova ◽  
Sergiy G. Nedilko ◽  
Sergiy A. Nedilko ◽  
Tetiana Voitenko ◽  
Olga Gomenyuk ◽  
...  
Keyword(s):  
Emission Spectra ◽  
Spectral Lines ◽  
Temperature Behavior ◽  
Precipitation Method ◽  
Temperature Range ◽  
Luminescence Emission ◽  
Electron Transitions ◽  
The Matrix ◽  
Co Precipitation ◽  
The Eu

The La1‑xEuxVO4 powders were synthesized by co-precipitation method. Emission spectra of the LaEuVO4 and La1‑xEuxVO4 powders consist of wide non-structural bands of the matrix emission and narrow spectral lines caused by inner f-f electron transitions in the Eu3+ ions, respectively. The both types of emission were studied within 8 – 300 K temperature range. Decomposition of spectra of the wide matrix emission on three bands has been carried out and temperature dependencies for each band were studied. Temperature behavior of the Eu3+ emission was investigated for lines assigned to different Eu3+ centres. Obtained dependencies are analyzed and discussed using proposed schemes of transitions in the VO43- groups and structure of the nearest surrounding of the Eu3+ emission centres.

Comparable Structural and Luminescent Characterization of the La1-xEuxVO4 Solid Solutions Synthesized by Solid State and Co-Precipitation Methods

2013 ◽  
Vol 200 ◽  
pp. 186-192 ◽  
Author(s):  
Oksana Chukova ◽  
Sergiy G. Nedilko ◽  
Sergiy A. Nedilko ◽  
Vasyl Sherbatsky ◽  
Tetiana Voitenko
Keyword(s):  
Solid State ◽  
Solid Solutions ◽  
Spectral Lines ◽  
Luminescence Properties ◽  
Luminescence Spectra ◽  
Excitation Spectra ◽  
Electron Transitions ◽  
Charge Transfer Transitions ◽  
The Matrix ◽  
Co Precipitation

Luminescence properties of the two series of the La1-xEuxVO4 (x ranges from to 0.3) solid solutions synthesized by the solid state and co-precipitation methods were investigated.. Luminescence spectra of the investigated samples consist of narrow spectral lines caused by inner f - f electron transitions in the impurity Eu3+ ions. Excitation spectra consist of three main bands those correspond to different types of transitions in the investigated matrices. There are O - Eu3+ charge transfer transitions, band-to-band transitions in the matrix of the vanadate compounds and electron transitions in the VO43- vanadate anion. Dependences of the structure and luminescence properties on rate compositions and method of synthesis were studied. Origins of the observed differences between luminescence characteristics of the samples obtained by two different methods are discussed.

Effect of Fe and Co promoters on CO methanation activity of nickel catalyst prepared by impregnation – co-precipitation method

2020 ◽  
Vol 18 (5-6) ◽  
Author(s):  
Buyan-Ulzii Battulga ◽  
Tungalagtamir Bold ◽  
Enkhsaruul Byambajav
Keyword(s):  
Synergetic Effect ◽  
Space Velocity ◽  
Catalytic Performance ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Alumina Support ◽  
Co Methanation ◽  
Temperature Range ◽  
Co Precipitation ◽  
Catalyst Distribution

AbstractNi based catalysts supported on γ-Al2O3 that was unpromoted (Ni/γAl2O3) or promoted (Ni–Fe/γAl2O3, Ni–Co/γAl2O3, and Ni–Fe–Co/γAl2O3) were prepared using by the impregnation – co-precipitation method. Their catalytic performances for CO methanation were studied at 3 atm with a weight hourly space velocity (WHSV) of 3000 ml/g/h of syngas with a molar ratio of H2/CO = 3 and in the temperature range between 130 and 350 °C. All promoters could improve nickel distribution, and decreased its particle sizes. It was found that the Ni–Co/γAl2O3 catalyst showed the highest catalytic performance for CO methanation in a low temperature range (<250 °C). The temperatures for the 20% CO conversion over Ni–Co/γAl2O3, Ni–Fe/γAl2O3, Ni–Fe–Co/γAl2O3 and Ni/γAl2O3 catalysts were 205, 253, 263 and 270 °C, respectively. The improved catalyst distribution by the addition of cobalt promoter caused the formation of β type nickel species which had an appropriate interacting strength with alumina support in the Ni–Co/γAl2O3. Though an addition of iron promoter improved catalyst distribution, the methane selectivity was lowered due to acceleration of both CO methanation and WGS reaction with the Ni–Fe/γAl2O3. Moreover, it was found that there was no synergetic effect from the binary Fe–Co promotors in the Ni–Fe–Co/γAl2O3 on catalytic activity for CO methanation.

Europium-Doped Hydroxyapatite: Influence of Excitation Wavelength on the Eu3+ Luminescence in the Hydroxyapatite

2015 ◽  
Vol 820 ◽  
pp. 335-340 ◽  
Author(s):  
Flávia R.O. Silva ◽  
Nelson B. de Lima ◽  
Deiby S. Gouveia ◽  
Nildemar A.M. Ferreira ◽  
Valter Ussui ◽  
...  
Keyword(s):  
Precipitation Method ◽  
Excitation Wavelength ◽  
Careful Evaluation ◽  
Lanthanide Ion ◽  
Site Occupation ◽  
Different Temperatures ◽  
Co Precipitation ◽  
The Eu

Hydroxyapatite (HA) doped with europium (HAEu) offers the advantage of making the hydroxyapatite a fluorescent biomarker, allowing their imaging through emissionin vivoandin vitrotests. Several authors had been based their studies about europium site occupation (CaI and CaII) in hydroxyapatite by the lanthanide ion luminescence, verifying the influence of the method of synthesis and concentration of the dopant ion. In this study HA nanoparticles doped with 1.4 mol% of trivalent europium were synthesized by co-precipitation method and thermal treated at different temperatures (600°C and 1200°C). A careful evaluation of the influence of the excitation wavelength of europium luminescence in the HAEu was performed and it has been verified that both the characteristics transitions of europium, at CaI and CaII sites, and the luminescent intensity are dependent on the excitation wavelength. The non-observance of this fact can lead to erroneous conclusions about the site occupation of europium in hydroxyapatites.

scholarly journals Preparation and photoluminescence study of Alumin o-boro silicate YAG fluorescent glass for White LED

2021 ◽  
Author(s):  
Chao Yang ◽  
Guohua Song ◽  
Jianwen Miao ◽  
Tingting Fan
Keyword(s):  
Light Emitting Diode ◽  
Emission Spectra ◽  
Precipitation Method ◽  
Excitation Spectra ◽  
Fluorescence Excitation ◽  
Light Emitting ◽  
White Leds ◽  
Near Ultraviolet ◽  
Fluorescence Excitation Spectra ◽  
Co Precipitation

Abstract The YAG: Eu 3+ fluorescent glass for NUV(near ultraviolet) white LEDs was obtained firstly by synthesizing Y 3 Al 5 O 12 (YAG): Eu 3+ precursors through a simple co-precipitation method, and then mixing precursor with B 2 O 3 -Al 2 O 3 -SiO 2 -Na 2 O-BaO glass powder calcined at 1400°C for 2.5 hours. The as-prepared YAG glass-ceramic phosphor was investigated by DTA, XRD, SEM, and photoluminescence (PL). Influence of YAG: Eu 3+ precursor and Eu 3+ doping on excitation and emission spectra also have been studied. The results show that: the phosphor's emission peak located at 393nm is correspond to the 7 F 0 - 5 L 6 transition of Eu 3+ ions, which matches good with UV LED chips; the phosphor gives intense emission at 593nm originating from the 5 D 0 - 7 F 1 transition of Eu 3+ ions. When the YAG precursor is 0.9g and amount of Eu 3+ doped is 0.08, the fluorescence excitation spectra of glass and emission spectra of the peak intensity reach its maximum value. The YAG: Eu 3+ fluorescence glass could be a promising material for the production of near ultraviolet chip white light-emitting diode.

scholarly journals Synthesis, Structure, Morphology, and Luminescent Properties of Ba2MgWO6: Eu3+ Double Perovskite Obtained by a Novel Co-Precipitation Method

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1614 ◽  
Author(s):  
Thi Hong Quan Vu ◽  
Bartosz Bondzior ◽  
Dagmara Stefańska ◽  
Natalia Miniajluk ◽  
Przemysław J. Dereń
Keyword(s):  
Broad Band ◽  
Emission Spectra ◽  
Double Perovskite ◽  
Luminescent Properties ◽  
Precipitation Method ◽  
High Symmetry ◽  
Cation Site ◽  
Structure Morphology ◽  
Co Precipitation ◽  
First Time

Eu3+ doped Ba2MgWO6 (BMW) double-perovskite was successfully synthesized for the first time by the co-precipitation method. The synthesis procedure, crystal structure, as well as morphology of obtained samples are presented. Domination of the 5D0–7F1 magnetic–dipole over forced electric–dipole transitions in the emission spectra indicates that Eu3+ ions are located in the high symmetry site with inversion center. Only one emission line assigned to the 5D0–7F0 transition was observed, confirming that europium substituted for only one host cation site. The photoluminescence excitation (PLE) spectrum is dominated by a strong and broad band related to the O2− → Eu3+ and O2− → W6+ charge transfer. The decay of the emission from the 5D0 and 5D1 levels was investigated. The temperature-dependent emission spectra showed that the T0.5 is equal to 350 K. Extinguishing mechanisms of the Eu3+ luminescence in the studied host are discussed.

scholarly journals Magnetic Nanoparticles Fishing for Biomarkers in Artificial Saliva

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3968
Author(s):  
Arpita Saha ◽  
Hamdi Ben Halima ◽  
Abhishek Saini ◽  
Juan Gallardo-Gonzalez ◽  
Nadia Zine ◽  
...  
Keyword(s):  
Magnetic Nanoparticles ◽  
Artificial Saliva ◽  
Coupling Reaction ◽  
Interleukin 10 ◽  
Covalent Immobilization ◽  
Precipitation Method ◽  
Necrosis Factor Alpha ◽  
The Matrix ◽  
Co Precipitation ◽  
Detection Of Biomarkers

Magnetic nanoparticles (MNPs) were synthesized using the colloidal co-precipitation method and further coated with silica using the Stöber process. These were functionalized with carboxylic and amine functionalities for further covalent immobilization of antibodies on these MNPs. The procedure for covalent immobilization of antibodies on MNPs was developed using 1-ethyl-3-(dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The evaluation of the efficiency of the coupling reaction was carried out by UV-vis spectrophotometry. The developed antibodies coupled to MNPs were tested for the pre-concentration of two biomarkers tumor necrosis factor alpha (TNF-α) and Interleukin-10 (IL-10). Both biomarkers were assessed in the matrix based on phosphate-buffered saline solution (PBS) and artificial saliva (AS) to carry out the demonstration of the format assay. Supernatants were used to determine the number of free biomarkers for both studies. Reduction of the nonspecific saliva protein adsorption on the surface of the complex antibodies-MNPs to levels low enough to allow the detection of biomarkers in complex media has been achieved.

scholarly journals Particle size-related limitations of persistent phosphors based on the doped Y3Al2Ga3O12 system

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Vitalii Boiko ◽  
Zhengfa Dai ◽  
Marta Markowska ◽  
Cristina Leonelli ◽  
Cecilia Mortalò ◽  
...  
Keyword(s):  
Particle Size ◽  
Surface Defects ◽  
Emission Spectra ◽  
Frequency Factor ◽  
Precipitation Method ◽  
Persistent Luminescence ◽  
Nano Particle ◽  
Yttrium Aluminium ◽  
Decay Times ◽  
Co Precipitation

AbstractCo-doped Ce3+, Cr3+ and Pr3+ yttrium–aluminium–gallium garnet powders of various sizes were obtained by co-precipitation method. The microstructure and morphology were investigated by XRPD, TEM and gas porosimetry. The luminescence properties were studied by excitation and emission spectra, quantum yield and decay times. Thermoluminescence measurements were performed to evaluate the activation energy, traps redistribution and frequency factor. Limitation in the energy transfer between dopant ions in the small particles, traps depth and surface defects were considered and investigated as responsible for the quenching of persistent luminescence. The phosphors annealed at 1100 °C show the optimal persistent luminescence and nano-particle size.

STRUCTURAL AND OPTICAL PROPERTIES OF Eu3+ DOPED CERIUM OXIDE NANOPHOSPHORS

2011 ◽  
Vol 04 (01) ◽  
pp. 13-16 ◽  
Author(s):  
R. SRINIVASAN ◽  
A. CHANDRA BOSE
Keyword(s):  
Grain Size ◽  
Diffuse Reflectance Spectroscopy ◽  
Site Occupancy ◽  
Precipitation Method ◽  
Ceria Nanoparticles ◽  
Doped Ceria ◽  
Red Color ◽  
Average Grain Size ◽  
Co Precipitation ◽  
The Eu

Europium (3%) doped ceria nanoparticles were successfully prepared by 72 h hydrolysis assisted co-precipitation method. The average grain size of the as-prepared sample was 11 nm. The grain sizes were 12 and 18 nm for samples annealed at 500°C and 800°C respectively. The grain size effect on optical bandgap is investigated from diffuse reflectance spectroscopy (DRS). The orange and red color emissions of europium doped ceria nanoparticles were investigated by photoluminescence (PL) spectra under excitation of 330 nm. The high intense orange emission peak was found at 591 nm for as-prepared and annealed nanoparticles. This is the characteristic peak of the Eu 3+ ion corresponding to the parity allowed magnetic dipole transition between the 5 D 0–7 F 1 states. Site occupancy of europium ions was estimated by Red (R)/Orange (O) intensity ratio using PL spectrum.

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