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

Abstract

We present the development and characterization of a low-cost fiber-optic colorimetric gas sensor for ammonia combined with the electronic circuitry for measurement control and RFID communication. The gas sensor detects ammonia using a 300 μm polyolefin fiber coated with a gas-sensitive polymer film. The spectral and time-dependent sensitivity of various polymer films was tested in transmission measurements at λ = 590 nm. A prototype of the gas sensor was tested under realistic measurement conditions, i.e. battery-driven and in a completely autonomous mode. The sensor system showed good sensitivity to the ammonia concentrations and response times in the order of minutes. The achievable power consumption was below 100 μW. Bromophenol blue-based films showed a strong reaction to ammonia, with saturation concentrations around 1,000 ppm and response times of about 15 s to 100 ppm. The colorimetric reaction was simulated using a simple kinetic model which was in good agreement with the experimental results

E5.1 - Chemosensitive gas detection

“…In this case the specific surface increases due to a complete coverage of the fibre. Our results on the fibrebased detection of ammonia were already shown in [22]. Fig.…”

“…The sensor response times were several minutes. The detection limit of this sensor can be estimated to 5 ppm [22].…”

Gas sensors based on membrane diffusion for environmental monitoring

“…The immersion mode is often used by probe sensors that may be deployed into the grab and pre-treated samples or real samples, such as for direct measurement or in-situ measurement, respectively. Some developed NH 3 sensors [50,96] and CO 2 sensors [48,93] belong to this group. In comparison, the flow sampling mode refers to employing a manifold with a pump and an injector to direct the non-treated or pre-treated sample into the detection device, which is commonly termed to flow injection analysis (FIA).…”

“…Usually, the membranes employed in membrane-diffusion based gas sensors are mainly hydrophobic Polytetrafluoroethylene (PTFE) membranes, also named Teflon membranes, that has been adopted by a wild range of gas sensors, such as CO 2 sensors [48,[92][93], SO 2 sensors [73,84], and NH 3 sensors [79,83,96], mainly because they are inert to permeated gas and sample matrix, permeable to gas analyte and impermeable to liquid sample matrix. The larger pore size of membrane results in larger D e,i value in Equation 7 [122], on the contrary, the larger thickness of membrane d m leads to the slower mass transfer across the membrane [123].…”

Gas sensing demonstration by using silica high-mesa waveguide with amplified cavity ring down spectroscopy technique

“…In order to solve this problem, we have proposed a silica high-mesa waveguide [5] for the gas-cell (breath detection part). The gas-sensing utilizing waveguide have been studied by many research institutes [6,7,8,9,10,11]. Similarly, in measuring method exploiting waveguide, a wide variety of method is also studied such as infrared absorption [6,7,8], Raman scattering [9], surface plasmon [10], and polymer colorimetric analysis [11].…”