title: Investigation of the hydrophobization efficiency of terbium-exchanged BEA zeolites by means of FT-IR, TGA, physical adsorption, and time-resolved photoluminescence.
abstract: Terbium-exchanged BEA zeolites were hydrophobized with phenyl-, vinyl-, and hexadecyltrimethoxysilanes by means of postsynthesis grafting. These materials were investigated using XRD, FT-IR, TGA, physical adsorption, and photoluminescence. Different methods for the analysis of the non-exponential decay of terbium photoluminescence in BEA zeolites were used ranging from discrete exponential to more complex approaches based on maximum entropy and global analysis. Two groups of decay times varying between 480 and 580 micros and 1-1.3 ms were assigned to the lifetimes of terbium exposed to water (unprotected) and protected by the organic groups, respectively. Our results showed that the preservation of terbium PL properties against detrimental effects of moisture adsorption could be ordered in the following sequence: hexadecyl > phenyl approximately vinyl. The photoluminescence results were in good agreement with the FT-IR, TGA, and physical adsorption data.
authors.affiliation: National Institute for Laser, Plasma and Radiation Physics, P.O. Box MG-36, RO 76900, Bucharest-Magurele, Romania. tiseanuc@ yahoo.com
authors.forename: Carmen
authors.initials: C
authors.lastname: Tiseanu
authors.forename: Bogdan
authors.initials: B
authors.lastname: Gagea
authors.forename: Vasile Ion
authors.initials: VI
authors.lastname: Parvulescu
authors.forename: Víctor
authors.initials: V
authors.lastname: Lórenz-Fonfría
authors.forename: André
authors.initials: A
authors.lastname: Gessner
authors.forename: Michael Uwe
authors.initials: MU
authors.lastname: Kumke