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1.
2.
T. Saraidarov R. Reisfeld A. Sashchiuk E. Lifshitz 《Journal of Sol-Gel Science and Technology》2003,26(1-3):533-540
PbS nanocrystals (NCs) ranging between 4–8 nm were incorporated into Zirconium-Silica-Urethane (ZSUR) matrix obtained by the sol-gel method. The sizes of the particles were controlled by temperature treatment and by concentration of PbS in ZSUR matrix. The sizes of PbS NCs were determined by TEM measurements. The quantum size effect could also be extracted from optical absorption and photoluminescence spectra. The new matrix allows incorporation of up to 40% PbS forming a characteristic structure of dendrite by reacting lead acetate with ammonium thiocyanate in sol-gel matrix. The sol precursors of the matrix for Zirconium-Silica-Urethane contained zirconium oxide (ZrO2) matrix solution, tetramethoxysilane (TMOS), 3-glycid oxypropyl trimethoxysilane (GLYMO) and polyethylene urethane silane (PEUS) synthesized separately. The ZrO2 matrix solution was obtained from zirconium n-tetrapropoxide in propanol and acetic acid was used as a chelating agent to stabilize the zirconium oxide precursor. 相似文献
3.
Absorption and fluorescence spectra of Sm3+ were measured in GeO2, ternary germanate, and borate glasses. From these the intensity parameters were calculated by use of the Judd-Ofelt formula.Visible emission and decay times from the4G5/2 level and its relative quantum efficiencies were measured The quantum efficiencies (QE) of the fluorescence in ternary germanate was higher by a factor of 20 than in GeO2, The small QE in GeO2, is explained by cross-relaxation between neighboring Sm3+ ions. The later process in hindered by the change in glass structure in the presence of modifier ions. A similar effect is observed in other glasses such as borate, where the addition of modifiers increases the QE of fluorescence. 相似文献
4.
Energy transfer from UO22+ to Sm3+ is described. The transfer efficiencies are calculated from the decrease of donor luminescence and lifetimes and from the increase of the acceptor fluorescence. It is shown that the transfer is nonradiative. The energy transfer efficiencies are greater when the donor is excited at higher energy levels due to stronger overlap between electronic levels of donor UO22+ and acceptor Sm3+. From the comparison of energy transfer efficiencies from UO22+ to Sm3+ and Eu3+ it is deduced that the overlap between excitation levels of donor and acceptor is a sufficient condition for the transfer. 相似文献
5.
Energy transfer from Bi3+ to Nd3+ is reported in germanate glass. It was found that the excitation range and intensities of the 4F → 4I, 4I emissions are increased several fold when excited through 1S0 → 3P1 absorption of Bi3+. It is shown that the energy transfer is nonradiative. The energy transfer probability and efficiency were calculated from the Bi3+ fluorescence decay rates and intensities. The Bi3+ → Nd3+ energy transfer may be utilized in Nd3+ glass laser. 相似文献
6.
A study of the energy transfer process between thulium and erbium is presented. From our measurements of fluorescence emissions and decay times the energy transfer efficiencies and probabilities were calculated. In this work the energy transfer which occurs between the upper levels in the UV and VIS regions of the two ions was especially studied. In the Tm-Er system, a mutual migration of energy occurs. The energy transfer from thulium to erbium is a multichannel process in which the energy is transferred from all the metastable levels of thulium to the matching energy levels of erbium. In addition, backtransfer of energy from erbium to thulium occurs by crossrelaxation of respective erbium transitions. The efficiency of energy transfer from thulium to erbium is independent of the levels between which the transfer occurs, but is dependent on the matrix. It is concluded that the energy is transferred via the phonons of the host glass. 相似文献
7.
Quantitative spot tests with a reflectance spectrometer have been developed for chloride (10–320 p.p.m.), sulphate (10–120 p.p.m.), phosphate (2–30 and 10–180 p.p.m.) and nitrite (1–35 and 10–100 p.p.m.). There are few interferences with these tests, and their effects can be overcome by standard techniques except for the interference from phosphate when it is present in the sulphate test, in large concentrations. 相似文献
8.
The features of fluorescent glass solar collectors are discussed. Combination of Nd3+ and Yb3+ in high refractive index glasses is suggested as concentration material. Energy absorbed by Nd3+ is transferred with high efficiency to Yb3+ emitting at 970 nm. The self-absorption of Nd3+ is eliminated and long-wavelength emission at 1.06 μm decreased as a result of energy transfer. 相似文献
9.
R. Reisfeld A. Bornstein J. Flahaut M. Guittard A.M. Loireau-Lozach 《Chemical physics letters》1977,47(3):408-410
Absorption bands of Ho3+ in vitreous La2S3·3Ga2S3 in the range 500 to 2000 nm were assigned. Excitation spectra reveal additional levels 5G6 and 5F3 obscured by the intrinsic absorption of the glass. The Ho3+ emission in chalcogenide glasses is more intense than in oxide glasses due to smaller non radiative relaxation as predicted by the theory of multiphonon relaxation. 相似文献
10.
Absorption and fluorescence spectra of Sn2+ and Sb3+ in borax, phosphate, and germanate glasses were measured in the temperature range 87–295°K. Fluorescence decay times of these ions in borax glass at 87°K was a single exponent with τ ≈ 6–11 μsec. At 293°K, two decay times were resolved in the range of 50–2000 nsec. The nonexponential behavior is interpreted by the repopulation of the 3P1 level from the 3P0 level. The temperature dependence of fluorescence and the low values of quantum efficiencies of fluorescence are explained by means of the configurational coordinate diagram model. 相似文献