Study On Optical Waveguide Chemical Sensors For Volatile Organic Compounds Detection

?Atmospheric pollution and indoor air pollution have been one of the most important environmental pollution problems all around the world. Volatile Organic Compounds (VOCs) are other kinds of gaseous pollutants which are second only to particles pollutants. In order 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 attracted considerable attention for monitoring environmental pollution, industrial processes, and biological fields, particularly, for the detection of gaseous elements in trace concentrations. OWG methods for sensing have several merits over other types of sensors, such as the potentials for high sensitivity, fast response time, remote controllability, system compactness, and intrinsically safe detection. Furthermore, they suffer little or no interence in the waveguide element of the sensor and can be made at a very low cost. OWG sensor technology will play an important role in gas detection applications.The article began by describing the source of volatile organic compounds and the poisoning effect of the human body from the grave. A number of developed and developing countries did many works on the detection of volatile organic compounds and control the emissions. We introduced the development of sensor status and importance in the national economy, and then introduced the application, classification, working principles and characteristics of chemical sensors. At last we focused on describing the ??acteristics, classification and working principle of optical waveguide sensors.In this paper, we combined with several merits of optical waveguide sensor to detect volatile organic compounds. Studies are as follows: 1. In this chapter the Nafion solution selected as sensitive material. The highly sensitive element of this sensor was made by coating the copper Nafion film over a single-mode potassium ion (K~+) exchanged glass OWG. We used the optical waveguide (OWG) sensor to detect toluene gas as a typical example BTX gases. The sensor exhibits a linear response to Toluene in the range of 0.96mg/m~3(0.25 ppm) to 16320mg/m~3(4250ppm) with response and recovery times less than 25 s. The sensor has a short response time, high sensitivity and good reversibility.2. In this chapter a novel sensor for gaseous Xylene has been developed using a combination of Nafion-Thionine composite film and optical waveguiding technologies. The sensor was fabricated by coating the polymer composite film over a single-mode planar potassium ion (K~+) exchanged glass optical waveguide (OWG). The sensor exhibits a linear response to Xylene in the range of 4mg/m~3(1ppm) to 6600mg/m~3 (1500ppm) with response and recovery times less than 22 s. Moreover, the developed sensor shows a satisfactory repeatability and a low sensitivity to common interfering gases such as Benzene, Toluene, Acetone, Aether, Ethanol, Methanol, Aammonia and Hydrochloric vapors.3. Study of the metal oxide semiconductor thin film optical waveguide are focused on optical communications and the development of integrated optical device at home and abroad, However, the application of NiO film in OWG sensors is rare,especially for VOC gas detection. In this chapter, we propose a new and simple NiO-based Chlorobenzene vapor optical waveguide (OWG) sensor. NiO powder were synthesized and characterized, sensitivity of the NiO film composite OWG sensor was estimated by the change of absorption properties of the film in dry air at room temperature. The sensor has a linear response to Chlorobenzene concentration, and sensitivity up to 1.8ppm (8.61mg/m~3). Mor??r, the developed sensor shows a desirable repeatability and a low sensitivity to common interfering gases such as benzene, toluene, xylene and ethanol vapors.