Reversible optical waveguide sensor for ammonia vapors

Abstract

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.

Low-cost fiber-optic waveguide sensor for the colorimetric detection of ammonia

“…They achieved detection limits in the ppb range for gaseous NH 3 , yet the reaction is irreversible. In 1983, Guiliani et al used a capillary as optical waveguide with a pH-sensitive oxazine-perchlorate layer, for the reversible detection of 60-1,000 ppm NH 3 (Guiliani et al 1983). As a result, several substances were implemented in colorimetric sensors; most of them are pH-sensitive and react to the alkalinity of NH 3 (Mills et al 1995;Brandenburg et al 1995).…”

Optical fiber ammonia sensing probes using reagent immobilized porous silica coating as transducers

“…Recently, several techniques have been proposed for continuously monitoring ammonia in gas samples. These include ion mobility spectrometry [5], electrochemical method [6], metal oxide semiconductor detectors [7], deep-UV [8] or near-IR absorption techniques [9], fiber optic sensors [10][11][12][13]. Among these techniques, fiber optic sensors are simple in structure, small in size, low cost in both fabrication and operation.…”

“…This sensor can reversibly detect ammonia in water down to 0.01 g/L [11]. Giuliani et al [12] used a small piece of silica capillary coated on the inner surface with a laser dye (Oxazine 170) as a transducer for sensing ammonia in air gas. They built up a simple sensor using a broadband LED as a light source and a photoresistor as a photodetector.…”

Plastic colorimetric film sensors for gaseous ammonia

“…In recent work we have incorporated hydrophilic anionic dyes and a base into the hydrophobic medium of a plastic thin film to create fast-response colorimetric and fluorimetric plastic thin-film sensors for carbon dioxide in gaseous form [1][2][3][4][5][6][7][8][9][10][11][12]13] and dissolved in aqueous solution [14]. In this latter work, the sensors were long-lived and showed no evidence of dye leaching.…”