A new absorption based $CO_2$ sensor based on Schiff base doped ethyl cellulose

Abstract

This paper reports absorption-based $CO_2$ sensing of the pH-active Schiff base 2-[(2-hydroxymethylphenylimino) methyl]-5-bromo-phenol (SB) in an ethyl cellulose (EC) matrix with and without Teflon coating. The $CO_2$ sensitivity of the SB dye in the EC matrix was evaluated in the presence of nonadecafluorodecanoic acid and tetrabutyl ammonium hydroxide. When exposed to $CO_2$ , the sensing films exhibited 76% of overall relative signal change and responded to $CO_2$ over a wide range: 1%-100 % (v/v). However, the slope of the spectral response between 1% and 5% (v/v) is more significant. The response time ($tau_{90}$) was 15 s, and limit of detection (LOD) was 0.3% (v/v) $CO_2$ . The stability of SB in the EC matrix was excellent, and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 6 months. Our stability tests are still in progress.