Study On SnO₂ And Adulterant Composite Film Gas Sensing Properities

Sensor has been become a various information sensing, collection, conversion, transmission and managing equipment on the today's information age and It has already been become indispensable technic facility in the every useful area. Especially, in automatism detection, automatism control system. The sensor that collect various information already has been become life line to these system. At present, many sensors have been developed in the area of industrial produce robotization, energy, transportation, fire forecast, security protect, environmental protection and hospitalization sanitation.The article began by describing sensor and sensor technology, chemical sensors and its classification, kind of gas sensors, operating principles and characters of each type semi-conducting gas sensors 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.The second chapter is part of basic theory of OWG. The theories about total reflection of light, structure of planar OWG, guide mode of planar waveguide, generation of evanescent wave, principle of evanescent wave sensor.In this paper, high sensitive OWG chemical sensors for detection of hazardous gases such as volatile organic compounds (VOCs) and acidic gases have been developed by immobilizing SnO2/La2O3, SnO2/Sb, SnO2/ZnO onto the surface of tin diffused glass optical waveguide. experimental section consists of following three chapters:1. SnO2 incorporated with varying amounts of La2O3 was developed as a sensitive reagent. The structural characteristics have been investigated by X-ray diffraction, FIT-IR spectra. and the optical properties of the thin films exposed to various volatile organic compounds saturated steam were studied by Visable absorption spectra. Experimental results show that, the absorption of the thin film become higher with the increase of mass fraction of Lanthunum at 630-680nm. among them,3.0%La2O3 (mass fraction) SnO2 thin film is more special, so, we chose the composite film over a tin-diffused glass optical waveguide, and discussed sensing mechanism.2. The SnO2Sb composite film was fabricated by dip-coating method. The structural characteristics have been investigated by X-ray diffraction, and the optical properties of the thin films exposed to various volatile organic compounds saturated steam were studied by transmittance spectra. Experimental results show that, the transmittance of the thin film become lower with the increase of mass fraction of antimony at 680nm, among them,0.5% Sb (mass fraction) SnO2 thin film is more special, so, we chose the composite film over a tin-diffused glass optical waveguide, and discussed sensing mechanism. The low concentration of other gases has no interference to detecting Xylene gas.3. The ZnO loading on SnO2 composite film was developed, The structural characteristics have been investigated by X-ray diffraction, and the optical properties of the thin films exposed to various volatile organic compounds saturated steam were studied by transmittance spectra. Experimental results show that, the transmittance of the thin film become lower with the increase of mass fraction of Zinic oxide at 670nm. among them,1.0% ZnO (mass fraction) SnO2 thin film is more special, so, we chose the composite film over a tin-diffused glass optical waveguide. This sensing element can detect volatile organic compounds and acidic gases seperatly. and discussed sensing mechanism.