TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Kumke, Michael Uwe
A1  - Pârvulescu, Vasile Ion
A1  - Martens, Johan
T1  - Species-related luminescence-structure relationships in europium-exchanged mesoporous material
N2  - 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.
Y1  - 2009
UR  - http://jap.aip.org/
U6  - https://doi.org/10.1063/1.3086634
SN  - 0021-8979
ER  - 
TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Pârvulescu, Victor I.
A1  - Kumke, Michael Uwe
A1  - Dobroiu, Svako
A1  - Geßner, André
A1  - Simon, Simion
T1  - Effects of support and ligand on the photoluminescence properties of siliceous grafted europium complexes
N2  - Europium ions were introduced in SiO2 and MCM-41 via two different pathways: (1) grafting the europium complexes with two alkoxide structures, 3-(2-imidazolin-1-yl)-propyl-triethoxysilane (IPTES) and aminopropyltrimethoxysilane (APTMS), and (2) functionalization of the SiO2 support with silicon 4- carboxylbutyltriethoxide followed by subsequent addition of the europium ions. The new materials were characterized using nitrogen adsorption isotherms at -196 degrees C, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared, NMR, DR-UV-vis, steady-state emission and excitation, and time-resolved photoluminescence spectroscopy. Spectral changes found in the time-resolved photoluminscence spectra strongly point to the distribution of europium ions on a range of environments in both SiO2 and MCM-41 supports. The average europium photoluminescence lifetimes decrease within the order: Eu3+-IPTES/SiO2 (550 mu s) > Eu3+-APTMS/SiO2 (425 mu s) > Eu3+-APTMS/MCM-41 (370 mu s) > Eu3+-IPTES/MCM-41 (320 mu s) > Eu3+-CABES/SiO2 (240 mu s). The photoluminescence quantum efficiency has the largest value, of 22%, for Eu3+-IPTES/SiO2, while the most reduced value, of 9%, was measured for Eu3+-CABES/SiO2.
Y1  - 2009
UR  - http://pubs.acs.org/journal/jpccck
U6  - https://doi.org/10.1021/Jp808411e
SN  - 1932-7447
ER  - 
TY  - JOUR
A1  - Tiseanu, Carmen
A1  - Lorenz-Fonfria, Victor A.
A1  - Geßner, André
A1  - Kumke, Michael Uwe
A1  - Gagea, Bogdan
T1  - Comparative luminescence study of terbium-exchanged zeolites silylated with alkoxysilanes
N2  - Terbium-exchanged ZSM-5, MOR and (H)BEA zeolites were silylated with phenyl-, vinyl- and hexadecyl trimethoxysilanes via a post-synthesis grafting. All samples were investigated by means of PXRD, FT-IR, TGA, physical adsorption, DR-UV-Vis and time-resolved photoluminescence spectroscopy. From the comparison of the photoluminescence decays of terbium-exchanged in parent (non-silylated) and silylated zeolites, it resulted that the silylation efficiency of the various alkoxysilanes is determined by the type of zeolite and follows the sequences: phenyl > vinyl > hexadecyl > parent for ZSM-5, hexadecyl a parts per thousand phenyl a parts per thousand vinyl > parent for MOR and hexadecyl > phenyl a parts per thousand vinyl > a parts per thousand parent for BEA zeolites, respectively.
Y1  - 2009
UR  - http://www.springerlink.com/content/100190
U6  - https://doi.org/10.1007/s10854-008-9597-1
SN  - 0957-4522
ER  -