A small glass capillary tube was fitted with a light-emitting diode and a phototransistor detector to form a multiple-reflecting optical waveguide device. When the capillary was coated with a thin solid film composed of an oxazine perchlorate dye, the device was demonstrated to be capable of reversibly sensing ammonia vapors. Ammoniavapor concentrations from 1000 parts in 10(6) (ppm) to less than 60 ppm were easily and reproducibly detected. A preliminary qualitative kinetic model is proposed to describe the vapor-film interaction.
A two-layer model for the analysis of an optical waveguide chemical vapor sensor is developed using a program written for a low-cost (PC) computer, which takes into account a nonadsorbing glass-fluid interface, the number of optical reflections, and probe beam divergence, for angles of incidence which are skewed about the critical angle for total internal reflection. This model is applied in the analysis of condensed organic vapors employing an uncoated optical thin walled glass capillary device developed at NRL. Reasonable agreement is obtained between the experimental results and model predictions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.