Fiber optic evanescent sensing of gaseous ammonia with a near infrared dye for leak detection.

The authors report here the detection of gaseous NH3 with the methylated and ethylated forms of dyes that were originally developed in a CEC program to produce spectral changes in the near IR (NIR) region on exposure to NH3. In contrast with pH sensitive dyes, these new dyes are suited for the detection of gaseous NH3 both in moist and dry air. The dyes were immobilized in the cladding material of com. available plastic-clad SiO2 fibers and the evanescent detection of gaseous NH3 was achieved with the limit of detection in dry air being 100 ppm for 2m length of the sensing fiber. [on SciFinder (R)]