Study On Fiber Optical Oxygen Sensor Based On Fluorescence Quenching

The detection of the gaseous oxygen and the dissolved oxygen is very important in many fields such as medicine, industrial analysis and environmental monitoring. Therefore, the researches of fiber optical oxygen sensors have gotten attention of people in recent years. Fiber optic oxygen sensor have many advantages such as intrinsic safety and high sensitivity, high detection precision, quick response, anti-disturbance of electromagnetism, and it can be used for long-distance, successive and on-line monitoring of the gaseous oxygen and the dissolved oxygen in dangerous environment. In this thesis, Ru(bpy)3Cl2 is used as fluorescent indicator and cellulose acetate (CA) as the matrix to form the fiber optic oxygen sensing membrane. Using the lock-in technology, a fiber optic oxygen sensor based on fluorescence quenching has been developed, for the detection of the concentration of the gaseous oxygen and the dissolved oxygen.Major contents of this paper include four aspects: the synthesis of fluorescent indicator, the preparation of oxygen sensing membrane, the design of fiber optic oxygen sensor and the detections of the dissolved oxygen and the gaseous oxygen.(1) RuCl3 3H2O and 2, 2 '- bipyridine are used as raw materials to synthesize the fluorescent indicator, we prepare a kind of new fluorescentindicator-Ru(bpy)3Cl2, which is then characterized by IR and XRD, Because ofits excellent fluorescent performance, Ru(bpy)3Cl2 is the good indicator of fiber optic oxygen sensor.(2) Using the cellulose acetate as matrix, the indicator is immobilized in CA membrane and a sensing membrane is formed. By adjusting the proportion of cellulose acetate, acetone and H2O, the network size of cellulose acetate membrane can be controlled and the leaking of fluorescent indicator in water is prevented.(3) The fiber optic oxygen sensor based on fluorescence quenching has been designed. Because the fluorescent signal is weak, the lock-in amplifyingtechnology is used to measure the concentration of the gaseous oxygen and the dissolved oxygen.(4) For the detection of gaseous oxygen, the respond time of the sensor isless than 20s, detection limit is 5 ppm and detection precision is 0.5%. The sensor has good repeatability and stability. Various factors influence the sensor performance has been studied.(5) For the detection of dissolved oxygen, the respond time of the sensor is less than 60 seconds, detection limit of 0.5 mg/1, and detection precision of 0.2 mg/1, good repeatability and stability. Especially, the sensor has the strong ability of anti-disturbance and is not affected by ions, pH value in water as well as water temperature. The sensor has been used to detect the dissolved oxygen in the water sample of Eastern Lake. There is no obvious difference between the results got by the sensor and the tradition method, Winkler method, and the measure deviation of the sensor is less than 2%. Which indicates that it will be possible for this sensor to be used for the on-line monitoring of water quality.