Optical fiber gas sensor

Pannell and coworkers34 described the use of poly(ferrocenylsilanes) as coatings in optical fiber gas sensors. In these devices a small change in refractive index of the polymer film results in a large change in the optical transmission of a tapered optical fiber. This is useful for remote sensing of ammonia or carbon dioxide. Polymers of type 6.20 with R/R = Me/Ph and copolymers from monomers with R/R = Me/Ph and Me/Me were found to be effective for this application. 

The synthesis and properties of poly(ferrocenylsilanes) have been extensively reviewed (7,11,96). Thermal, anionic, and transition-metal-catalyzed ROP of [IJsilaferrocenophanes has led to the prodnction of polymers containing a variety of functional groups attached to the sihcon atoms (96-102). The structures and morphologies of this class of polymer have been examined using X-ray diffraction, optical, atomic force, and scanning electron microscopy as well as other techniques (103-107). Pannell and co-workers have recently tested these materials as coatings for tapered optical-fiber gas sensors (108). 

Zhang, Y., Zhao, Y., Bai, L and Zhang, F. (2013) High-sensitivity optical fiber gas sensors based on novel optical devices. Instrum. ScL Technol., 41,187 201. 

Resonant photoacoustic gas spectrometry was adapted to fiber optic sensor technology32 as early as in 1984. A Mach-Zehnder arrangement was combined with a resonant photoacoustic cell for gap analysis. The pollutant gas NO2 was detectable in a concentration of 0.5 ppm. In a smart optical fiber hydrogen sensor, the fiber is coated with palladium metal which expands on exposure to hydrogen. This changes the effective optical path length of the fiber, which is detected by interferometry33. 

Inaba H., Chan K., Ito H., All-optical remote gas sensor system over a 20 km range based on low-loss optical fibers in the near infrared region, Proc. SPIE-Int. Soc. Opt. Eng. 1984 514 211. 

Hansmann D.R., Gehrich G.L., Practical perspectives on the in-vitro and in-vivo evaluation of a fiber optic blood gas sensor, Proc. SPIE 906 4 (1988). 

Martin R.C., Malin S.F., Bartnik D.J., Schilling A.M., Furlong S.C., Performance and use of paracorporeal fiber optic blood gas sensors, Proc. SPIE 2131 426 (1994). 

An optical-fiber CL sensor is reported for trichlorethylene assay [87], The sensor consists of a glass fiber bundle and a transducer consisting of three components (i) a gas-permeable membrane to separate trichlorethylene from water, (ii) H2S04-NaN03 mixture as oxidizing agent, and (iii) a luminol solution. The assay of trichloroethylene can be done in the 0.05-0.6- J,g/mL concentration range with a detection limit of 0.03 J.g/mL. 

Seller B R 1994 Design of intravascular fiber optic blood gas sensors IEEE Eng. Med. Biol. EMB-13 327-35... 

Scientists investigated on optical inteferometric stmctures that can be applied in toxic gas sensors. The sensor head consists of PANi and nafion layers deposited on the face of the telecommunication optical fiber. Humidity sensors are useful for the detection of the relative humidity (RH) in various environments. Polymer composites and modified polymers with hydrophilic properties have been used in humidity sensor devices. Researchers prepared nanocomposite pallets of iron oxide and PPy for humidity and gas sensing by a simultaneous gelation and polymerization process. This resulted in the formation of a mixed iron oxide phase for... 

In context with methane detection during offshore oil drilling, another infrared fiber optic methane sensor was reported25. The detector comprises 3 main units a microcomputer-based signal processing and control unit, a nonconducting fiber optic gas sensor, and an optical fiber cable module. The system operates at an absorption line of methane where silica fibers have very low losses. 

Grant S.A., Sateher Jr. J.H., Bettencourt K., Development od sol-gel based fiber optic nitrogen dioxide gas sensors, Sens. Actuat B 2000 69 132-137. 

A particularly difficult problem in microwave processing is the correct measurement of the reaction temperature during the irradiation phase. Classical temperature sensors (thermometers, thermocouples) will fail since they will couple with the electromagnetic field. Temperature measurement can be achieved either by means of an immersed temperature probe (fiber-optic or gas-balloon thermometer) or on the outer surface of the reaction vessels by means of a remote IR sensor. Due to the volumetric character of microwave heating, the surface temperature of the reaction vessel will not always reflect the actual temperature inside the vessel [7]. 

Miniaturized and robust optical fiber sensors capable of accurate and reliable measurement of refractive index of the surrounding environment have attracted tremendous interest in recent years. One of the driving forces for the development of these fiber optic devices is their broad applications in chemical sensing. When placed in the liquid solution or gas mixture, these fiber sensors can detect the chemical composition change by monitoring its refractive index variation. These... 

S. Sekimoto, H. Nakagawa, S. Okazaki, K. Fukuda, S. Asakura, T Shigemori, and S. Takahashi, A fiber-optic evanescent-wave hydrogen gas sensor using palladium-supported tungsten oxide. Sensors Actuators B 66(1-3), 142-145 (2000). 

Related to the plasmon resonance physics is the micromirror optical sensor for hydrogen (Butler, 1991). Like gold and silver, palladium is a free-electron gas metal in which charge groupings such as phonons or plasmons are likely to occur. As we have seen already, palladium has a natural selectivity due to its sorption of monoatomic hydrogen. In that sensor, the reflectivity of the thin Pd film mirror mounted at the end of cladded optical fiber (Fig. 9.19) is modulated by absorption of hydrogen. 

Luminescent evanescent wave-based sensors use optical fibers and planar waveguides [105,106] as fight-guiding structures, and they are more complex than the absorbance ones. However, such optodes have been satisfactorily applied to measure fluorescence of indicators or labels for the measurement of gas molecules, proteins or labeled antigen-antibody interactions as well as directly in solution [24,107] when immobilized in matrices [23,109]. 

FIGURE 10.30 Scanning electron microscopy (SEM) images of cross section of a commercial optical fiber coated with a NaA zeoUte thick layer (a) total cross section and (b) magnification view of the NaA zeolite layer. (From Lopez, J., Pina, M.P., Coronas, J., Pelayo, J., and Santamaria, J., A novel optical device for gas sensor applications based on zeolitic materials. Books of abstracts of the 1st NanoSpain Workshop, San Sebastian, 2004.)... 

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