Near-infrared optical detection of acids in atmospheric air by phthalocyanine dyes in polymer films

Recently available phthalocyanine dyes with absorption bands in the NIR spectral region were investigated as reagents for the detection of vapour leaks of industrial acids such as hydrochloric and acetic acid. The dyes ProJet 830NP and ProJet 860NP (Zeneca Specialities) were entrapped in silicone polymer films. The response of the sensing films to the presence of acids was assessed by absorption spectrometry. The acid concentration in the test atmospheres was approximately 4% m/m. The long-term stability of the phthalocyanine dyes and the reversibility of their optical properties after exposure to acid vapours make these materials suitable for optical sensor applications.