@article{TiseanuKumkeParvulescuetal.2009,
  author    = {Tiseanu, Carmen and Kumke, Michael Uwe and P{\^a}rvulescu, Vasile Ion and Martens, Johan},
  title     = {Species-related luminescence-structure relationships in europium-exchanged mesoporous material},
  issn      = {0021-8979},
  doi       = {10.1063/1.3086634},
  year      = {2009},
  abstract  = {Europium exchanged into a mesoporous material (Zeotile-1) was extensively characterized with respect to the Si/ Al ratio and surface silylation by using time-resolved emission spectroscopy. Qualitative as well as quantitative details of the europium species-related luminescence-structure relationships were obtained and discussed such as the decay associated spectra, local distortion and structure of the bonding environment, crystal-field strength, radiative relaxation rates, and the quantum efficiency. Thus, two europium species were found in the parent as well as in the silylated materials: one species located on the internal surface and the second inside the 2-2.5 nm pores. The species located on the internal surface is characterized by photoluminescence decay times of 105 mu s <tau < 125 mu s, an asymmetry value R of 0.6 < R < 0.8, and a quantum efficiency of 2\%-2.5\%. Upon silylation, the photoluminescence decay times, the asymmetry values, and the quantum efficiency were increased to 160 mu s <tau < 180 mu s, 1.7 < R < 2.1, and similar to 4\%, respectively. Following silylation, the number of water molecules is reduced in the first coordination shell of the europium species located on the internal surface from eight to nine to about five. On the other hand, the europium species located inside the pores showed a much longer photoluminescence decay time (460 mu s <tau < 560 mu s) and a much higher asymmetry ratio (5 < R < 6.5). The related photoluminescence efficiency was 26\%-30\%. An average of one up to two water molecules in the first coordination shell of the europium species located inside the pores was estimated for both parent and silylated materials.},
  language  = {en}
}
@article{TiseanuKumkeParvulescuetal.2008,
  author    = {Tiseanu, Carmen and Kumke, Michael Uwe and Parvulescu, Vasile Ion and Geßner, Andre and Gagea, Bogdan and Martens, Johan},
  title     = {Europium(3+) : an efficient luminescence probe for the Si to Al ratio and silylation effect in the microporous- mesoporous Zeogrid materials},
  doi       = {10.1021/Jp711337h},
  year      = {2008},
  language  = {en}
}
@article{TiseanuGessnerKumkeetal.2008,
  author    = {Tiseanu, Carmen and Geßner, Andre and Kumke, Michael Uwe and Gagea, Bogdan and Parvulescu, Vasile Ion and Martens, Johan},
  title     = {Photoluminescence spectra and dynamics of lanthanide-doped microporous materials},
  doi       = {10.1016/j.jlumin.2007.10.018},
  year      = {2008},
  abstract  = {A series of terbium- and europium-exchanged microporous-mesoporous zeolite Socony Mobil Five (MFI)-type materials such as Zeotile-1 and Zeogrid with varying Si/Al ratios was investigated using FTIR, PXRD, adsorption- desorption isotherms of N-2 at 77 K and time-resolved luminescence spectroscopy. Silylation of the lanthanides-exchanged Zeotile-1 and Zeogrid with hexadecyl trimethoxysilanes via post-synthesis grafting was also studied. The results showed that the lanthanide's photoluminescence spectra and decays were modified due to silylation. The different silylation effects in Zeotile-1 and Zeogrid were correlated with the textural properties of the investigated materials. (C) 2007 Elsevier B.V. All rights reserved.},
  language  = {en}
}