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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 Pro Jet 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.

The realisation of an opto-chemical ammonia sensor suitable for personal monitoring tasks is described, comprising a cyanine dye immobilised in a microporous glass thin film. The fabrication of sensor platforms incorporating embossed grating couplers provides a compact optical design with effective waveguiding characteristics, resulting in reversible ammonia sensitivity in the 5-100 ppm range in under 2 min. Cross-sensitivity of sensor response with water and other potential interferents is considered.

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