Study On Dissolved Oxygen Sensor Based On Fluorescence Quenching

Dissolved oxygen refers to molecular oxygen dissolved in water or other solvents.The detection of dissolved oxygen is widely used in medical,chemical,agricultural,environmental protection and industrial production.It develops a fast detection speed,high sensitivity and small volume.A low-cost dissolved oxygen sensor is of great significance.Among them,dissolved oxygen detection methods are mainly divided into iodometric method,electrode method and fluorescence method.After studying the research status at home and abroad,this paper designs a dissolved oxygen sensor based on fluorescence quenching principle.In this thesis,the principle of fluorescence quenching is used as the theoretical basis.The oxygen-sensitive platinum porphyrin is selected as the fluorescent indicator,and the dissolved oxygen concentration is detected by detecting the fluorescence lifetime.The response of the fluorescence system to the sinusoidal excitation light signal is analyzed,and the measurement of the fluorescence lifetime is converted to the measurement of the phase difference between the sinusoidal excitation light signal and the fluorescence signal.The structure of lock-in amplifier r and the principle of phase-sensing detection are introduced.The scheme of measuring the phase difference of dual-phase lock-in amplifier is designed.In this thesis,the dissolved oxygen sensor is designed for each functional module,such as fluorescent probe,signal generator,LED excitation light modulation circuit,photoelectric detection circuit,band pass filter,phase shifter,phase sensitive detection circuit,low pass filter.The schematic,calculation and simulation results are given.The overall circuit design was completed and the PCB diagram was drawn.In this thesis,the designed dissolved oxygen sensor was tested and used in measuring.The optical and electrical properties of the dissolved oxygen sensor were tested,the fluorescence excitation and detection effects were examined,and the effect of the phase difference was measured by a dual-phase lock-in amplifier.Calibration of the sensor was accomplished using a dissolved oxygen sensor to detect dissolved oxygen concentration.The effect of aqueous solution salinity and temperature on fluorescence quenching was investigated.