München 2004 – wissenschaftliches Programm

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MO: Molekülphysik

MO 7: Femtosekundenspektroskopie: Protontransfer + Energiefluss

MO 7.3: Vortrag

Montag, 22. März 2004, 14:30–14:45, HS 315

HBT in nanoscaled zeolite: Intrazeolite Femtochemistry — •Uli Schmidhammer, Vincent De Waele, and Eberhard Riedle — Lehrstuhl für BioMolekulare Optik, Sektion Physik Ludwig-Maximilians-Universität München

Nanosized periodic structures of zeolites loaded with photoreactive molecules have a great potential in optoelectronics and the design of functional materials. The investigation of the photochemistry of such host guest systems, that frequently show strong interaction, requires a resolution down to the femtosecond time scale. This is hard to achieve in extended bulk samples.

We report on the photochemical behavior of 2-(2’-hydroxyphenyl)benzothiazole (HBT) in FAU zeolite and demonstrate that the use of a nanoscaled colloidal suspension allows to perform pump-probe experiments without restriction in time resolution. HBT was incorporated during the synthesis of FAU in the presence of the template tetramethylammonium hydroxide (TMA) [1]. The inclusion appears to involve an interaction between the TMA ions and HBT leading to a modification of HBT. The normal enol groundstate is replaced by the trans-keto conformation. Unlike the enol form this isomer shows strong fluorescence around 470 nm. Transient measurements reveal an increase of this emission within 1.5 ps and a decay time of 4 ns. The spectral position and the decay time identify the emissive state as the anion of HBT, formed by excited state proton transfer to the solvent.

[1] S. Mintova, V. De Waele, U. Schmidhammer, E. Riedle and T. Bein, Angew. Chem. Int. Ed. 42 (2003) 1611.