| The research of metal porphyrins compounds has attracted wide attention in recent years.Metalloporphyrins had shown excellent gas-sensing properties due to their superior photoelectric properties and recognition of certain functional groups.Therefore,it has a great significance to apply metalloporphyrins in gas detection.In this paper,metal?Fe,Co,Mn?tetraphenylporphyrin compounds were synthetised and their gas sensitivity properties were systematically studied.The influence of interfering gases on the gas sensitivity of sensitive components was investigated by simulation experiments,and the influence of environmental humidity on the sensing element was discussed.In the introduction part of this paper,the definition and classification of sensors and gas sensors were systematically introduced.Also the development,classification and application of optical waveguide gas sensors were presented.And the material selection of the optical waveguide sensing element was mainly introduced.In the second chapter,the characteristics and synthesis methods of porphyrins and metalloporphyrins were systematically introduced;tetraphenylporphyrins and metal?Fe,Co,Mn?tetraphenylporphyrins were synthesized by the Adler method,of which productions were purified by column chromatography.The effects of reaction solvent and synthetic time on the yield of porphyrin were investigated.The metal porphyrins were characterized by the means of 1H NMR,XPS,FT-IR and UV-Vis spectra.And their structures were discussed.In the third chapter,tetraphenylporphyrin iron/K+exchanged glass optical waveguide elements were fabricated via spin-coating method with tetraphenylporphyrin iron as sensitive reagent,and a variety of volatile gases?saturated steam?were tested many times at room temperature,such as toluene,xylene and ethylenediamine.After determining the main tested gas,the influence of film morphology on the gas sensitivity of FeTPP sensitive materials was investigated.The influence of interfering gases?toluene,ammonia,ethanol gas?on the gas-sensitivity of FeTPP films was researched via simulation experiments and the effect of humidity on the sensitive element was also studied.The experimental results showed that the sensing element exhibited a good selective response to ethylenediamine gas with a detection limit of 1×10-10?V/V0?.Ethylenediamine,of which detction limit was1×10-7?V/V0?in the presence of interfering gas,and the influence of ambient humidity on the sensitive element could be ignored.On the basis of the experiments in Chapter 3,to further explore the different responses of the metal elements,which was in the molecular center of the metalloporphyrin complex,to the measured vapors,a tetraphenylporphyrin cobalt/K+exchanged glass optical waveguide device was prepared,18 types of volatile gases?saturated steam?were tested number of times at room temperature.The effect of environmental humidity on the sensitive element and the influence of interfering gases on the sensitive components were also tested.The experimental results indicated that the prepared element had a good selectivity to ethanol gas and could detect ethanol gas with a concentration of 1×10-6?V/V0?.The sensing element could detect 1×10-4?V/V0?ethanol gas in the presence of interfering gases.When the gas concentrations of interference gases?benzene,toluene and ammonia?were lower than 1×10-5?V/V0?,it displayed a small effect on the sensitivity of sensing element to ethanol,and the influence of environmental humidity on sensitive components could be neglected.On the basis work of the first two chapters,in the fifth chapter,the tetraphenylporphyrin manganese,which had empty orbits in the central ion,was chosen as sensing reagent.Tetraphenylporphyrin manganese/K+exchanged glass optical waveguide elements were prepared,19 kinds of volatile gases?saturated steam?were tested at ambient temperature,such as benzene,amine and ethanol.The effect of interfering gas on the gas sensitivity of sensitive elements was investigated via simulation experiments.There were some differences between the previous two chapters and this chapter:the effect of ambient humidity on the gas sensitivity of sensitive elements was further explored.The results showed that the prepared sensing element had a very good selective response to trimethylamine gas.It could detect pure trimethylamine gas with a concentration of 1×10-8?V/V0?.Detction of trimethylamine was 1×10-7?V/V0?in the presence of interfering gases?dichloromethane,chloroform,carbon tetrachloride?.When the gas concentration of interference gas?methylamine,ammonia,ethanol?was lower than 1×10-4?V/V0?,it displayed a tiny effect on the gas response of TMA gas.And it also showed that humidity had less influence on sensitive elements,but humidity revealed a certain degree of influence on the gas sensitivity of TMA gas.When the ambient humidity was higher than 70%RH,there would be a certain impact on the gas sensitivity of sensing element to trimethylamine gas. |
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