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Metallo-porphyrins as gas sensing material for colorimetric gas sensors on planar optical waveguides

: Peter, C.; Schmitt, K.; Schiel, M.; Wöllenstein, J.


Schmid, U. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Smart sensors, actuators, and MEMS V : 18-20 April 2011, Prague, Czech Republic
Bellingham, WA: SPIE, 2011 (Proceedings of SPIE 8066)
ISBN: 978-0-8194-8655-4
Paper 80660L
Conference "Smart Sensors, Actuators, and MEMS" <5, 2011, Prague>
Conference Paper
Fraunhofer IPM ()
gasochromic material; chemical gas sensors; colorimetric gas sensors; metallo-porphyrin; optical waveguide

The work presented here focuses on the investigations of metallo-porphyrins and their gasochromic behavior. Gasochromic materials change their color while they are exposed to a certain gas. So they offer the possibility to develop very selective chemical gas sensors. In the focus of this work is the metallo-porphyrin 5, 10, 15, 20- tetraphenylporphyrin-zinc (ZnTPP). When embedded into a polymeric matrix (PVC) the color change to the toxic gas NO2 can be detected. During exposure to NO2 the dye changes its color from bright purple to yellow. To develop a standalone gas sensor, the ZnTPP/PVC matrix is deposited onto a planar optical waveguide. The color change of the porphyrin dye, due to the gas exposure, can be detected in the evanescent field of the optical waveguide. Therefore the light of a high power LED is coupled into the waveguide. The color change of the porphyrin is detectable with photodiodes as variations of the decoupled light intensity. The sensor shows no cross-sensitivities to other gases like CO2, NH3, EtOH, CO or water vapor. NO2 is detectable with a limit of 1 ppm.