Study on PTA Thin Film and Its Adulterant Thin Films Glass Optical Waveguide Sensing Element
|Keywords||Optical waveguide (OWG) gas sensor Peroxide Decatungstate Volatile organic vapors Methyl violet Acid gases|
With the rapid development of the national economy, timely, accurate of flammable, explosive, toxic, hazardous gas detection, the forecast and automatic control has become an important issue for people to urgent. The gas sensor detects more optical waveguide (Optical Waveguide OWG) gas sensor is a new research direction at home and abroad. Compared with other sensing technologies, the optical waveguide sensor has a resistance to electromagnetic interference, electrical insulation, ease of integration, easy miniaturization, high sensitivity, fast response and low cost, and many other features, gradually become a hot gas sensor research. Has a broad application prospects in the field of environmental monitoring, industrial process control, biochemical detection and homeland security. Optical waveguide sensor technology to play a better value for the gas detection. This paper combines the superior characteristics of the optical waveguide sensing element laboratory conditions, screening of different substances that are sensitive to volatile organic vapors and acid gases work as follows: 1. The peroxide Decatungstate (Peroxopolytungstic Acid, PTA) has optical transparent, for good adhesion properties of the substrate, and easy film-forming characteristics. The synthetic peroxide Decatungstate powder by spin coating method, and peroxide Decatungstate as sensitive reagents fixed in K-exchanged glass optical waveguide surface, developed the optical waveguide gas sensing sensing element. The results indicate that the sensor element on the benzene volatile organic compounds having a better response, particularly a response maximum chlorobenzene, can detect the volume ratio of 4 × 10-7 chlorophenyl vapor. Of alcohols, formaldehyde and acetone vapors are almost no response. 2 on the basis of the work in the first chapter of the peroxide Decatungstate sensitive film modified; in peroxide Decatungstate solution doped with the right amount of methyl green solution and spin coating method PTA- MG film is fixed in the K exchange surface of the glass optical waveguide, developed a waveguide sensing element one can detect xylene vapor. The sensing element to low concentrations of xylene vapor has a good selectivity and a reversible response, and good reproducibility, response and recovery time is short, it is possible to detect a volume ratio of 1 × 10-6 xylene vapor. . Methyl violet sensitive film, the sensitive film with HCl, H2S, and S02 before and after the visible absorption spectrum changes, and on this basis the development of glass optical waveguide and composite optical waveguide acidic gases (HCl, The sensing element of H2S, SO2), and analysis of sensitive mechanism. Wavelength of 532nm laser as a light source using a flow injection of acid gas detection. When the acidity of the gas the greater the (same concentration), the greater the intensity of the output light (signal) change, that is, the pure methyl violet film sensitive element can detect the volume ratio of 4 × 10-6 HCl gas, 25 × 10-6 H2S gas and 8 × 10-5 SO2 gas, volatile organic vapor response can be ignored without taking into account the NO2 gas sensitivity is irreversible, and therefore its not detect. Developed out of the composite waveguide in this experiment failed to achieve the effect of improving the sensitivity. 4. Nickel-doped PTA as sensitive reagents using the dip-coating method will be fixed in a mixed solution of tin-doped glass optical waveguide surface, developed a method for detecting BTX-CB (Benzene, Toluene, Xylene, Cholorobenzene) vapor waveguide gas-sensitive element, and detects a volume ratio of 1 × 10-6 (1ppm) xylene vapor, the volume ratio of 1 × 10-5 (10ppm) of chlorobenzene vapor, 5 × 10-5 (50 ppm) of toluene vapor and 2.5 × 10-4 benzene vapor. The gas sensing element has a good reversibility, response and recovery time is short.