Papers by Keyword: Luminescence Spectra

Abstract: Pr³⁺-doped Li₂O – Gd₂O₃ – B₂O₃ glasses (LGBO glass) with the formula 60Li₂O:10Gd₂O₃:(30-x)B₂O₃:xPrO₃ were fabricated using melt quenching technique. The five glass samples with different concentrations of Pr₂O₃ were prepared under atmospheric pressure. The samples were investigated on their properties: absorption and photoluminescence. All absorption bands are increase with increasing of Pr³⁺ content. The emission spectra were measured with 446 nm light pumped by xenon lamp. The maximum luminescence intensity was observed at x = 0.50 mol% andthe CIE color coordinates showed the bluish purple emission light for this concentration.

Abstract: Melt quenching technique have been used to prepare the dysprosium-doped lithium-gadolinium borate glasses, which have the composition [60Li₂O:10Gd₂O₃:(30-x) B₂O₃:xDy₂O₃] (LGBO:Dy³⁺), under atmospheric pressure. Some properties: density, molar volume, absorption spectra and photoluminescence of the LGBO:Dy³⁺ glasses were investigated and discussed. The density of glasses drops to the minimum point at 0.05 mol% and swings after that point. The molar volume of the glasses does not depend on Dy₂O₃ concentration. In absorption spectra for the range of visible to near infrared wavelengths, there are 5 obvious peaks indicating the Dy³⁺ in glass network. The intensity of each peak at certain wavelength increases with concentration of the Dy₂O₃. Whereas the excitation spectra show 7 obvious peaks representing the transitions from the ground state ⁶H_15/2 to various excited states. The Xenon compact arc lamps were used to measure the emission spectra with 388 nm light. As the result, the LGBO:Dy³⁺ glass sample with 0.50 mol% of Dy³⁺ shows the highest intensity in the emission spectra.

Abstract: In this paper for investigation of the medicine «Lactobacterin» containing lactic acid bacteria was used luminescence method. It is shown, that spectrum of the Lactobacilli has 3 peaks from different substances. It is shown that during 2 hours the bacterial cells are alive.

Abstract: The samarium-doped lithium-gadolinium borate [60Li₂O:10Gd₂O₃:(30-x) B₂O₃:xSm₂O₃] (LGBO:Sm³⁺) glasses have been melted and quenched in stainless plate under an air atmosphere. Some physical and optical properties within wavelength concerned and photoluminescence of the LGBO:Sm³⁺ glasses were measured and discussed. The density of glasses dropped until 0.10 mol% and tends to increase after that point, while molar volume of the glasses tends to increase with concentration of Sm₂O_3.. In absorption spectra, there are 2 obvious peaks in UV-VIS range and 6 peaks in NIR range indicating the Sm³⁺ in glass matrices. The sharpness of a peak, in the absorption spectra, also increases with concentration of the dopant. The 7 obvious peaks in excitation spectra represent the transitions from the ground state ⁶H_5/2 to various excited states. Furthermore, The emission spectra were observed under 404 nm light from the Xenon compact arc lamps, and showed the concentration quenching effect (CQE) at 1.00 mol% of Sm³⁺. Additional, The lifetimes showed decreasing trend with concentration of Sm₂O_3.. As the result, The LGBO:Sm³⁺ glass doped with 1.00 mol% of Sm³⁺ gives the highest result for luminescence properties.

Abstract: In the present work the influence of neodymium concentration (0-1at-%) and sintering conditions on 8/65/35 PLZT:Nd³⁺ ceramics were studied. All ceramic powders were synthesized by MOM technique from high purity raw materials (>99,9%), and subsequently sintered by free sintering and hot uniaxial pressing method. To analyze the powders and ceramics more the XRD, EDS SEM, and ferroelectric measurements were performed. Optical spectra were examined for all prepared samples, and their optical properties were analyzed using reflectance, excitation and luminescence measurements. The study gives a detailed account of the relationships between doping and preparing conditions on the basic physical and dielectric and optical properties of obtained ceramic materials.

Abstract: A series of lanthanide complexes with acetylacetonate and a new asymmetrical 5-[p-(4-fluorobenzoyloxy)-m-ethyloxy]phenyl-10,15,20-triphenylporphyrin were prepared and characterized by elemental analyses, molar conductance, UV-Vis, IR, 1H NMR, luminescence spectra and themal analysis. Quantum yields of Q band fluorescence are in the region 0.073-0.097 at room temperature. Complexes have higher stability (decompose until 211°C). The structure that both the porphyrin behaved as a tetradentate ligand and acetylacetonate as a bidentate ligand are coordinated to a rare earth ion also has been proposed.

Abstract: The structure and photoluminescence (PL) of ZnO films deposited on Si (111) substrates by chemical spray deposition using aqueous solution of zinc acetate [Zn (CH3 CO2)2 , 2H2O] was investigated. It was found that these properties depend strongly on growth temperature and grain size. The samples grown at the optimum deposition conditions can generate stronger luminescence. It was revealed by X-ray diffraction that the preferred orientation of poly-crystals is along C-axis, with hexagonal wurtzite structure. PL spectroscopy results shows an evident ultra-violet (UV) emission observed near 380 nm with a broad low intensity band centred at 430 nm. The band was reported as being caused by the defects in the grain boundaries of ZnO. Under optimum deposition conditions a low resistivity and a high optical transmittance of the order of 2.8×10−4 Ω cm and 90%, respectively, were obtained.

Abstract: Material defects such as Si-core and C-core partial dislocations (PDs) and threading screw dislocations (TSDs) and threading edge dislocations (TEDs) are being investigated for their contributions to device performances in 4H-SiC. Non-destructive electroluminescence and photoluminescence techniques can be powerful tools for examining these dislocations. In this report, these techniques were used to reveal the different spectral characteristics for the mentioned dislocations. At higher injection levels, both the Si-core and C-core PDs possessed a spectral peak at 700 nm. However, at lower injection levels, the spectral peak for the Si-core PD remained at 700 nm while the peak for the C-core moved to longer wavelengths. For the threading dislocations, TSDs possessed a peak between 800 and 850 nm while the TEDs possessed a peak at 600 nm independent of the injection levels.

Abstract: MWO4 (M = Ca, Sr, Ba and Pb) was solvothermally prepared using metallic nitrates and sodium tungstate in 25/5 volume ratios of glycerol/water (SGL) and propylene glycol/water (SPG) at 160 oC for 6 h. XRD revealed the presence of MWO4 single phase with tetragonal scheelite structure. The strong W-O stretching band of WO4 tetrahedrons was detected at 705-875 cm-1. The product images show nano-sized particles in basic SGL and SPG solvents and flower-like particles in SPG solvent with pH of 6.7. Central peaks of the luminescent spectra are 445, 446, 443 and 440 nm, respectively.