| Air is one of the main factors on which human existence depend on. The amount of pollutants are becoming more along with the development of national economy, acidic gases and vapor of volatile organic compounds (VOCs) are the main cause that accrue pollution in human living area.Therefore to effectively detect and prevent disasters, it is important to study new sensors which are safe, reliable, continuous, rapid, and in-stiu detection of remnant gases. The optical waveguide (OWG) sensor has many characters such as:high sensitivity, rapid response, easy micromation, easy realization for on-line continuous monitoring, anti-disturbance of electromagnetism, good insulation, low cost etc, therefore it has extensive application foreground in the area of environmental monitoring, industrial process control, biochemical detection and homeland security. In this dissertation, high sensitive OWG chemical sensors for detection of hazardous gases such as xylene,SO2,chlorobenzene, formaldehyde and toluene have been developed by immobilizing SnO2,Fe2O3-SnO2,fuchsin basic and SnCl2.2H2O-fuchsin basic onto the surface of tin-diffused glass optical waveguide.The article began by describing the source of atmospheric pollution and indoor air pollution, species and the direct hazard to human health. The sensor technology and its applications, chemical sensors and its classification were introduced.The developments of OWG sensors were reviewed and the characters and classification of OWG sensors were mainly introduced. At last the purpose and the main content of the dissertation are put forward. In this dissertation some research work were done on planar OWG sensor system described below:1.(In chapter three)SnO2 is one of the semi-conducting metal oxides sensitive element which widly used and it has a high sensitivity, physical and chemical stability and low cost. In this chapter the SnO2 selected as sensitive material, the highly sensitive element of this sensor was made by coating the SnO2 film over a tin-diffused glass OWG. We used the optical waveguide (OWG) sensor to detect xylene gas as a typical example VOCs gases. The sensor exhibits a linear response to xylene in the range of 2.5×10-7 (0.25 ppm) to 1×10-3 (1000ppm) volume fraction with response time less than 5 s and other gases for this sensor have less obstruction.2.(In chapter four),becouse of the difference of the adulterate measurements lead to Fe2O3-SnO2 composite film have the different selectivity and sensitivity for the gases. In this chapter the Fe2O3-SnO2 selected as sensitive material and adulterate measurements 5%,0.8%,0.3%,respectively. The highly sensitive element of this sensor was made by coating the Fe2O3-SnO2 composite film over a tin diffused glass OWG. We used the Fe2O3-SnO2 composite film/tin diffused glass OWG sensor to detect SO2, formaldehyde and chlorobenzene, and the sensor has the good selectivity, and respond to the volume fraction are 1×10-6, 1×10-7,2×10-6 (1ppm, 0.1ppm, 2ppm),respectively.3.Fuchsin basic is one of the alkalescence dye.When the oxidize attitude it shows red, and when the reductive attitude it shows pale yellow. When in the strong acid medium fuchsin molecule easy reduced and changed red into the pale yellow. We set off this point, fuchsin basic selected as sensitive material, and developed the fuchsin basic thin film/tin-diffused glass OWG. At the same time we start to study film/tin-diffused glass OWG for SO2 gas detection and investigate the sensitive principle.The research results shows that, the optical waveguide sonsor has the good sensitivity to SO2 gas, and it can be detect lower than 5×10-7(0.5ppm)volume fraction the SO2 gas.4. In this chapter we developt the SnCl2.2H2O-fuchsin basic film/tin-diffused glass OWG, and detect to the volatile organic compounds(VOCs).The results shows that,the sensor has a linear response to toluene concentration,and sensitivity up to 5×10-5(50ppm) volume fraction.This OWG system proved to be fast in response, reversible, and highly sensitive good recurrence, for VOCs and SO2 gases, and Current results indicates parts-per-billion detection could be achieved by controlling the adsorption properties of the sensing layer, and the sensor has the useful value.
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