| Along with the rapid development of national economy, it becomes very urgent mission to detect, predict and auto control the flammable, explosive, deleterious gases in advance and high-precision. At present, sensors are widely adopted in detection of the gases, and it is a new trend to study the Optical Waveguide (OWG) sensor in home and overseas. Moreever,these are gradually become hotspot in gas sensor research. The optical waveguide sensor has several advantageous over other types of sensors, such as anti-electromagnetic interference, electric insulation, easy miniaturization and integration, high sensitivity, quick response and low cost.it has attracted considerable attention for monitoring environmental pollution, industrial processes, and biological fields, particularly, for the detection of gaseous elements in trace concentrations. OWG sensor technology will play an important role in gas detection applications. In this paper,we combined with several merits of optical waveguide sensor to detect volatile organic compounds and acidic gases. Studies are as follows:1.Peroxopolytungstic Acid (PTA) has optical transparency, easy to develop into thin film by various coating techniques. In this chapter, the PTA was selected as sensing film, and immobilized onto a potassium ion (K+)-exchanged glass OWG by spin-coating method.Experimental result shows that PTA film/K+-exchanged glass OWG sensor has strong responses to aromatic hydrocarbon vapors such as benzene, toluene, chlorobenzene, and xylene. But the responses to other VOCs are weaker. Among chlorobenzene, benzene, toluene, and xylene of the same concentration, the sensor has a higher response to chlorobenzene. The sensor can detect chlorobenzene vapor concentrations as low as 4×10-7.2.In this chapter, A xylene vapor sensing device based on planar optical waveguide (OWG) sensor was fabricated by using peroxopolytungstic acid-methyl green(PTA-MG)composite thin film immobilized over a K+-exchanged glass OWG by spin-coating method. The sensor can detect xylene vapor concentrations as low as 1×10-6and has some unique qualities which can be characterized as short response time, higher sensitivity. This sensor exhibits a good linear,reversible response to xylene vapor sensing.3.The methyl violet was selected as sensing film, and immobilized on to tin-doped glass OWG and PTA thin film composite OWG,respectively,by the means of spin coater,and detected the acidic gases (HCl,H2S,SO2)using by flow injection method at 532nm. The signal (output light intensity) increases with the increase of acidity of the gases. When Only the MV thin film as sensing element,it can detect 4×10-6 concentration of HCl,25×10-6 concentration of H2S,8×10-5 concentration of SO2. Its sensitivity to the VOCs can be negligible, and sensitivity to the NO2 is irreversible, therefore, we did not carry out further study on it. However, the fabricated composite OWG did not provide higher sensitivity.4.The nickel doped PTA thin film immobilizing onto the surface of tin-doped glass OWG as sensing element by the means of spin coater and prepared a new sensor for BTX-CB vapors detection. The fabricated sensor element can detect xylene concentrations as low as 1×10-6 (1ppm),chlorobenzene concentrations of 1×10-5 (10ppm),toluene concentration of 5×10-5(50ppm)and benzene concentration of 2.5×10-4(250ppm). The sensor have rapid and reversible sensitivity to the BTX-CB vapors,it can be characterized by reversible,rapid response,good stability and high repeatability.
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