Regensburg 2000 – scientific programme

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O: Oberflächenphysik

O 15: Elektronische Struktur (I)

O 15.1: Talk

Tuesday, March 28, 2000, 11:15–11:30, H37

Conducting Polypyrrole doped with Phthalocyaninesulfonates - new materials for chemical sensors — •Ricardo Mikalo, Günter Appel, Patrick Hoffmann, and Dieter Schmeißer — BTU Cottbus, LS Angewandte Physik Sensorik, Erich-Weiner-Str. 1, 03046 Cottbus, Germany

Polypyrrole - a conducting polymer - is used as an active electrode of a quartz micro ballance and considered as a gate electrode in all-polymer field effect transistors used as chemical sensor. We use substituted phthalocyanines as dopants of polypyrrole as they offer the possibility to enhance the dopant concentration as well as to include functionalized groups. We studied these films by photoelectron spectroscopy, NEXAFS, PEEM, and TEM. These investigations revealed that the electronic structure as well as the morphology are highly dependent on the dopant’s structure. We suggest a new charge transport model for 5-ring heterocycle conductive polymers. Whereas in the standard model only the carbon backbone is considered for the charge transport, we found by NEXAFS investigations that the heteroatom has a considerable high participation in the gap states, which are responsible for the charge transport. The dopants π-interactions force the nitrogen lone pair wave functions to contribute to the conducting polymer π-system. This is a novel approach concerning the application as chemical sensors since the reversible interaction of the analyte modifies the dopant and not the matrix.