New photoluminophore nanocomposite based on organic compound with Eu ions and copolymer styrene-butylmethacrilate

New nanocomposite (NC) material on the base of thenoyltrifluoroacetone (TTA) coordinated with trivalent europium ions and structured with phenantroline (Eu(TTA)₃Phen) and copolymer from styrene and butylmethacrylate (1:1) (SBMA) was prepared. The visible photoluminescence spectra of composites excited with N₂-laser (λ = 0.337 μm) at room and T = 78 K temperatures were studied. For the Eu(TTA)₃Phen/SBMA nanocomposite material emission bands located at 578, 590, 612, 675 and 705 nm can be attributed to the spin forbidden f–f transitions ⁵D₀ → ⁷F_i (i = 0,1,2,3 and 4), respectively. The more intensive luminescence band situated at 612 nm with the half width of 3 nm is connected to the Eu³⁺ ion electronic transition ⁵D₀ → ⁷F₂. It was shown that the maximum intensity of photoluminescence occurs at the concentration of 15% of the Eu(TTA)₃Phen in the SBMA polymer matrix.     

Fluorescence enhancement of europium complex co-doped with terbium complex in a poly(methyl methacrylate) matrix

The enhanced fluorescence of Eu(DBM)₃Phen(DBM: dibenzoylmethide; Phen: phenanthroline) by Tb(DBM)₃Phen in a poly(methyl methacrylate) (PMMA) has been studied. A combinatorial methodology was adopted to allow rapid optimization of the fluorescence enhancement conditions of thin-film samples in arrays of microwells. Based on Eu(DBM)₃Phen doped PMMA, three material libraries were generated in order to compare the effects of species identity and Tb(DBM)₃Phen content to the effect of other complexes containing enhancing ions (La³⁺, Gd³⁺, Dy³⁺, Y³⁺, Ce³⁺) on the luminescence efficiency of the Eu³⁺ complex in PMMA. The fluorescence enhancement of Eu(DBM)₃Phen in PMMA is considered to originate from intramolecular and intermolecular energy transfer processes.     

Peculiarities of photoluminescence excited by 157 nm wavelength F2 excimer laser in fused and unfused silicon dioxide

Photoluminescence (PL) spectra and kinetics of high purity amorphous silicon dioxide with ultra low hydroxyl content is studied under the excitation by F₂ excimer laser (157 nm wavelength) pulses. Materials synthesized in the SPCVD plasma chemical process are studied before and after fusion. Two bands are found in the PL spectra: one centered at 2.6–2.9 eV (a blue band) and the other at 4.4 eV (a UV band). Luminescence intensity of unfused material is found to increase significantly with exposure time starting from a very small level, whereas in fused counterpart it does not depend on irradiation time. Both bands show complicated decay kinetics, to which add exponential and hyperbolic functions. The UV band of the unfused material is characterized by decay with exponential time constant τ  4.5 ns and hyperbolic function t⁻ⁿ, where n = 1.5 ± 0.4. For the blue band the hyperbolic decay kinetics with n  1.5 extends to several milliseconds, gradually transforming to the exponential one with τ = 11 ± 0.5 ms. In fused glass relative contribution of the fast component to the UV band is small whereas for the blue one it is great, that allows one to more accurately determine the hyperbolic law factor n = 1.1 ± 0.1 typical for tunneling recombination. Simultaneous intracenter and recombination luminescence, the later occurring with the participation of laser radiation induced defects, add particular features to the decay kinetics. Spectra of the above luminescence processes are different. A less sharp position of bands is associated with the recombination luminescence. The origin of the observed PL features we attribute to the presence of oxygen deficient centers in glass network in the form of twofold coordinated silicon. Such centers being affected by network irregularities can be responsible for the recombination PL component. A great variety of network irregularities is responsible for centers’ structural inequivalence, which causes a non-uniform broadening of PL spectral and kinetic parameters.