Fabrication And Study Of Gas-Sensing Properities Of Octaethylporphyrin And Zinc Complexes Film Optical Waveguide Elements

With the rapid development of science and technology,continuous improvement of people's living standards,human beings have paid more and more attention to the timely and accurate detection standards for flammable,explosive,toxic and harmful gases.In order to prevent and effectively control the harm of pollutants to the environment and human body,it has great application value to develop a gas sensor that has highly sensitivity,can detect harmful gases in real time,and is portable and easy to operate.In this dissertation,a series of gas sensors were developed using octaethylporphyrin and octaethylporphyrin zinc as sensitive materials.Gas sensitivity tests were performed on mixed gases produced by the main raw materials of indoor pollution,achieving good results.In the preface of the first chapter,starting from the sources of volatile gases and their harms to human health,the importance of sensors in modern information technology was described.The sensor definition,classification,principle,characteristics,performance evaluation,future development,practical application prospects,and sensitive materials were given in detail.In the second chapter,an octaethylporphyrin film/K⁺exchanged glass optical waveguide sensing element was prepared by spin-coating method with octaethylporphyrin as sensitive reagent.The thin film surface was characterized by film thickness gage?SGC-10?,atomic force microscope?AFM?and scanning electron microscope?FE-SEM?.The thickness and refractive index of the film were measured,and the preparation conditions of the sensor were optimized.At the same time,the preparation conditions of the sensor were optimized.The results showed that the surface roughness of the film was about 35.6 nm,the refractive index was 1.7890,and the film thickness was within 114±5 nm.The sensor element had good response to methylamine gas with a concentration lower than 1×10^-8 V/V₀,response time was 2 s,recovery time was 7 s,detection limit?signal to noise ratio S/N=5.1?was 1×10^-8V/V₀,the relative standard deviation was 1.11%,and it showed good reversibility and stability.In order to deeply explore the nature of octaethylporphyrin,octaethylporphyrin's aggregation behavior was studied.The pH value of octaethylporphyrin solution was controlled by adding inorganic acid to octaethylporphyrin solution.The peak position of free base octaethylporphyrin and protonated octaethylporphyrin was compared,and the aggregation type of the protonated octaethylporphyrin was determined,that was,J type aggregates.The gas sensing element based on J aggregate was fabricated,and its gas sensitivity was studied.The gas sensing mechanism was preliminarily discussed.The third chapter was about the preparation and gas sensitivity of highly sensitive octaethylporphyrin-TiO₂ strip composite film/tin doped glass waveguide sensor.In this chapter,the TiO₂ was synthesized by the sol-gel method?sol-gel?,and the TiO₂ was fixed on the surface of the Sn doped glass waveguide element by the dip coating method.The TiO₂/Sn doped glass waveguide was obtained.Then the sensitive material was fixed on the TiO₂ with spin coating method to obtain the sensitive element.Gas sensing tests were carried out on the sensitive components at room temperature.The experimental results showed that the sensing element had a good selective response to methylamine and could detect the methylamine gas with a volume ratio of 1 x 10^-10 V/V₀,response time was 2 s,recovery time was 9 s,and the detection limit was 2 times higher than that of the general planar optical waveguide.The fourth chapter was the preparation and gas sensing properties of the octaethylporphyrin zinc film/K⁺exchanged glass optical waveguide sensor.In this chapter,the surface of the sensitive film was characterized by FE-SEM.The thickness and refractive index of the film were measured.The response to VOCs gas was studied.The experimental results showed that the sensor element had a better selective response to toluene gas with a volume ratio of less than 1×10^-9 V/V₀.After many parallel experiments,the octaethylporphyrin zinc film/K⁺exchange glass optical waveguide sensor displayed the advantages of easy preparation,simple operation,fast detection speed,low detection limit,short response and short recovery period.In the fifth chapter,octaethylporphyrin zinc was used as a sensitive reagent,octaethylporphyrin zinc-TiO₂ strip composite film/tin doping was prepared by immersing-draw method and spin-dip coating method,and its response to VOCs gas was studied.It could be seen from the experimental results that the sensor element developed in this chapter has higher sensitivity and could detect toluene gas with a concentration lower than 1×10^-11 V/V₀.Based on this research,the sensor was used to test the gas sensitivity of the mixed gas produced by indoor pollution.The experimental results showed that the sensor showed a fast response-recovery time,good reproducibility,high stability,when detecting the mixed gas produced by the paint.The ingredient of the paint was analyzed by gas chromatography mass spectrometry?GC-MS?to prove that it contained benzene and its homologs.The use of the sensitive element to detect indoor pollutants provided a certain basis,and had great application prospects.The sixth chapter was the conclusion part,summarizing all the research contents in the master's stage.