| Porphyrin and its derivatives are promising gas-sensitive materials.In recent years,in order to better exert their gas-sensitive properties,porphyrin-metal oxide hybrid materials have attracted the interest of researchers at home and abroad.In this thesis,5,10,15,20-(tetra-4-aminophenyl)porphyrin(TAPP)with strong coordination ability was selected as the main gas-sensitive material,and SnO2 and CeO2 nanoparticles were synthesized.(SnO2,CeO2)was composited with 5,10,15,20-(tetra-4-aminophenyl)porphyrin to prepare optical waveguide gas-sensing elements.The gas-sensing performance and the influence of environmental humidity on the sensor was investigated experimentally and discussed.The main research content of this thesis inlcudes three parts:The first part,5,10,15,20-(tetra-4-aminophenyl)porphyrin was utilized as the sensing material,and spin-coating method was used to prepare the TAPP-OWG sensing element.The solidified TAPP film was tested for gas sensitivity to more than a dozen organic volatile gases and several acidic gases(SO2,H2S,CO2,NO2),at room temperature.TAPP-OWG sensitive elements exhibited high sensitivity to SO2 and H2S gases,with short response and recovery time,and it was capable of measuring 1×10-12(V/V0)SO2 and H2S gas respectively at room temperature.The sensor has good repeatability for SO2 and H2S gas with 1×10-11(V/V0)concentration,with short response time(t1)and recovery time(t2)for 1×10-11(V/V0)SO2(t1=4 s,t2=157 s)and H2S(t1=2 s,t2=117 s)gas;The influence of ambient humidity on TAPP-OWG sensitive elements is discussed based on experimental results.In the second part,SnO2 and 5,10,15,20-(tetra-4-aminophenyl)porphyrin(TAPP)were fixed step by step on the surface of K+ion exchanged optical waveguide element by spin coating method,then SnO2/TAPP composite thin film optical waveguide(OWG)gas sensor(SnO2/TAPP-OWG)was achieved.At room temperature,the gas sensitivity of several organic volatile gases,SO2 and H2S gas were studied.The SnO2/TAPP composite thin film optical waveguide sensor prepared under the optimal conditions also has the best gas sensitivity to SO2 and H2S.The sensor can detect SO2 and H2S with a concentration of 1×10-11(V/V0).When the sensor is contacted with SO2 with a concentration of 1×10-9(V/V0)and H2S with a concentration of 1×10-8(V/V0)at room temperature,the response time(t1)and recovery time(t2)of the gas are respectively(t1=2 s,t2=52 s),(t1=3 s,t2=56 s),with good repeatability.The influence of ambient humidity on the gas sensitivity of the sensor is discussed.The experimental results show that the combination of TAPP and SnO2 does not change the selectivity of the sensor,while the sensitivity of the sensor to SO2 and H2S gas is reduced by about 10 times,and the influence range of TAPP sensor on humidity is shortened.In the third part,CeO2 and 5,10,15,20-(tetra-4-aminophenyl)porphyrin suspensions were prepared by blending method,and the suspensions were fixed on the surface of K+ion exchanged optical waveguide element by spin coating method.CeO2/TAPP composite optical waveguide gas sensor(CeO2/TAPP-OWG)was prepared,and the gas sensitivity towards several organic volatile gases,SO2 and H2S gas were tested at room temperature.The experimental results show that after TAPP and CeO2 are composited,the selectivity of the sensor is not changed,and the sensor still has high sensitivity to SO2 and H2S gas.CeO2/TAPP-OWG sensor can detect SO2with a concentration of 1×10-13(V/V0)and H2S with a concentration of 1×10-12(V/V0).when the sensor is contacted with SO2 and H2S with a concentration of 1×10-10(V/V0)at room temperature,the response time(t1)and recovery time(t2)of the sensing device are respectively(t1=3 s,t2=47 s),(t1=4 s,t2=80 s),showing good repeatability.After TAPP and CeO2 are compounded,the sensitivity to SO2 is increased about 10times,and the influence range of TAPP sensor on humidity is shortened. |
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