Sensing Mechanism And Inspecting Properties Of Metal Porphyrin Room Temperature Phosphorescence Oxygen

The accurate detection of oxygen content has great strategic significance in environmental monitoring,clinical medicine and food packaging.Room temperature phosphorescence（RTP）oxygen sensing technology based on dynamic quenching mechanism has been widely used in many fields due to its strong oxygen response ability,high accuracy and easy automation.However,the single wavelength mode RTP oxygen measurement method is seriously disturbed by the fluctuation of laser and detector increases the system error greatly.There is a lack of knowledge about the influencing factors and regulation methods of oxygen quenching constant K_SV,which limits the further development of RTP technology.The influence of external environment such as temperature and photobleaching phenomenon on oxygen sensing materials are rarely studied,which seriously reduces the accuracy of oxygen content detection.In order to solve the above problems,this dissertation takes metalloporphyrin RTP materials as the research object,and explores the corresponding oxygen sensing mechanism in detail,so as to realize the accurate oxygen detection.In this dissertation,the influence on oxygen quenching constant K_SV value and its adjusting methods on metalloporphyrin oxygen sensing materials were studied.The ratiometric oxygen sensing material uses octaethylporphyrin platinum（PtOEP）and coumarin 6（C6）as oxygen sensitive and reference indicators,fluoropolymer of Poly（St-co-TFEMA）as the matrix material,and PtOEP-C6/Poly（St-co-TFEMA）ratiometric oxygen sensing film was prepared by solvent evaporation method;Distributed oxygen sensing material of Gd-HMME solution was prepared via solvent-thermal method by using Gd Cl₃and hematoporphyrin monomethyl ether（HMME）as reactants.For ratiometric oxygen sensing,the influence of monomer ratio TFEMA/St,indicator PtOEP concentration and film thickness on Stern-Volmer equation and K_SV value were investigated.The K_SV value increases first and then decreases with the increase of TFEMA/St and PtOEP concentration,and the increase of film thickness decreases the K_SV value monotonically.In view of Gd-HMME solution,the mechanism of the variation in spectral properties were revealed by combining the chemical structure and energy level structure of porphyrins.The regulation rules of oxygen sensing ability based on Gd-HMME solution were explored by re-adding imidazole into the purified Gd-HMME solution.The linearity of the Stern-Volmer equations were not affected,and the K_SVvalues were decrease sharply first and then leveling off gradually.The K_SV values of 2.5μmol/L and 1.0 mmol/L Gd-HMME solution were enhanced by 46 and 100 times by adjusting the concentration of imidazole.The maximum K_SV values were 576.1 k Pa^-1 and89.2 k Pa^-1,with the oxygen detection range of 0-8 k Pa and 0-100 k Pa respectively,and the limit of detection（LOD）was determined to be 6.6 ppm.The effects of the variation of temperature and photobleaching problem on oxygen sensing ability of PtOEP-C6/Poly（St-co-TFEMA）oxygen sensing film were studied.The phosphorescence intensity and lifetime of PtOEP decrease linearly with the increase of temperature,while the signal of C6 remained stable,while and the corresponding mechanism were analyzed.The Stern-Volmer equations exhibit high linearity in the range of 32-60℃;the calculated K_SV and k_q value increases monotonously with change of temperature.Furthermore,the accurate detection of oxygen content were obtained by using the temperature corrected Stern-Volmer calibration curve,which enabled us successfully develop a temperature correction method to achieve the detection of real oxygen content.In light of the the anti-photobleaching ability,the fluorine-containing film is a suitable matrix material was verified by comparing the photostability of different matrix materials.Moreover,the effects of excitation light intensity,ambient oxygen concentration,indicator concentration and film thickness on photobleaching ability were investigated.It was found that the phosphorescence intensity decreases exponentially with time in the absence of oxygen,while in the presence of oxygen,the phosphorescence intensity and time meet the double exponential decay model.The e attenuation model reflects the two action mechanisms of fast process and slow process contained in photobleaching.The ratiometric oxygen sensor was prepared based on PtOEP-C6/Poly（St-co-TFEMA）film combined with the Labview program for realizing real-time automatic and precise monitoring of oxygen concentration.The linear calibration curve of OP-DO oxygen content was given by defining the optical parameter OP（Optical Parameter）.The influence of the change of excitation intensity and the fluctuation of laser and detector on the OP and direct luminescence signals were compared,which verifies that the oxygen sensor has strong anti-interference ability.Other performance indicators of the sensor were evaluated,including the quenching and recovery time of the sensor were t _Q=0.4 s and t _R=1.3 s,respectively;the detection range was 0-40 mg/L with the accuracy of0.5%F.S.,LOD of system was LOD=0.10 mg/L.Finally,the oxygen sensor was applied to analyze the dynamic process of the variation of dissolved oxygen content in water,and it was found that the dissolved oxygen content increases exponentially with time.