Simultaneous optical and electrical CO2 detection in one sensitive film
We are presenting a combination of two measurement methods for simultaneous generation of optical and electrical signals out of one gasochromic film. For this purpose we combined the UV-vis spectroscopy with the contact potential difference (CPD) measurement. To demonstrate the advantages of this combined measurement we chose a well-known gasochromic system. For testing the benefits and limitations of the concept, we used a phenol red based film with known sensitivity to CO2. Getting in contact with CO2 the phenol red based sensitive layer shows changes in absorption spectra and in contact potential difference (CPD). Due to the combination of both measurement techniques the influence of temperature and humidity, which is always a challenge in gas detection, can be identified and eliminated. We see different signal behaviour of the two measurement methods at humidity and temperature changes. In dry conditions the optical signal response towards CO2 is reduced, whereas the electrical signal is increased. Whereas the optical signal response is strongly dependent on the temperature, the electrical signal seems to be independent. These reactions look promising for future gas sensor applications in the field of gasochromic sensor dye evaluation.