D3.3 - Colorimetric Gas Sensors for the Detection of Am¬monia, Nitrogen Dioxide and Carbon Monoxide: Current Status and Research Trends

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
D3 - Gas Sensors I
J. Wöllenstein - Universität of Freiburg, C. Peter, K. Schmitt - Fraunhofer Institute for Physical Measurement, Freiburg (Germany), J. Courbat, D. Briand - Ecole Polytechnique Fédérale de Lausanne (EPFL), Neuchâtel (Switzerland)
135 - 135


Colorimetric detection of gases has been used for years. Colorimetric gas sensors are based on the change in color of a chemochromic reagent incorporated in a porous matrix. Several products are available on the market, such as the well established Dräger gas tubes. When the gas is sucked in the tube a color change occurs and its concentration can be evaluated with a graduation. The talk will be focused on the state-of-the-art of colorimetric gas sensors and current developments for the detection of ammonia, nitrogen dioxide and carbon monoxide.
Colorimetric detection of ammonia might be performed by different types of chemochromic reagents such as porphyrin-based or pH indicatorbased films. We present the evaluation of colorimetric films for the detection of ammonia gas targeting their deposition on optical waveguides. The investigated films are composed of a pH indicator selective to NH3 embedded in a polymeric matrix and deposited on a waveguide to improve the sensitivity. They have been successfully deposited onto glass waveguides to evaluate their optical properties and gas sensing operation. All films exhibited an excellent selectivity towards NH3. A matrix composed of bromphenol blue and PMMA exhibited the best properties. Concentrations as low as 0.25 ppm of NH3 were easily measured and the theoretical limit of detection was evaluated to be of 2 ppb.
For fire detection the detection of gases is of high interest, in particular the detection of CO and NO2 as leading substances during fire events. In special applications CO-sensors are already used to support conventional optical or heat detectors for fire detection. Although CO is a leading gas in many fire events there are other typical fire events emitting – compared to CO - mainly NO2 (for example polyurethane or n-heptane fires). Gas sensors to detect CO or NO2 are available on the market but they are too expensive, the dimensions are too big or the long-term stability is too poor. Additionally the power consumption of most suitable technologies is much too high. We present our work on colorimetric films combined with a MEMS-compatible low-power technology for the CO and NO2-detection in order to overcome these drawbacks of the existing technologies.