| The core part of gas sensor is gas-sensitive material.At present,in order to improve its gas-sensitive performance,the development of high-performance gas sensing materials has become a research focus.This article systematically develops research work from the design/preparation/optimization of new sensitive materials to the performance research of sensitive components and the exploration of sensitive mechanisms.The research contents are as follows:(1)In this experiment,graphite oxide-tetracarboxyphenyl porphyrin(GO-TCPP),tetracarboxyphenyl porphyrin-graphite carbon nitride(TCPP-g-C3N4)composite sensitive materials were prepared by SDBS self-asembly method and surface sensitization method,respectively.The prepared samples were characterized and analyzed by scanning electron microscope(SEM),transmission electron microscope(TEM),Raman and fourier transform infrared spectroscopy(FTIR).Gas sensors based on TCPP,GO-TCPP,TCPP-g-C3N4were prepared by spin-coating method.The built-in optical waveguide detection system was used to test the gas-sensitive characteristics of these sensors for variable organic compounds at room temperature.(2)Under the light source of 520 nm,the TCPP sensor detected 18 volatile organic compounds(VOCs),which showed high selectivity to ethylenediamine(EDA),its response recovery time is 5 s and 10 s,can detect EDA of 1×10-7(V/V0),and the mechanism of action may be charge transfer in the form of hydrogen bonds.Under the670 nm light source,the TCPP sensor shows good selectivity for SO2,H2S,but it does not recover.This article used saturated ammonia to help it return to the baseline,and SO2of 1×10-7(V/V0)and H2S of 1×10-6(V/V0)can be detected,and the mechanism of action may be protonation and deprotonation of porphyrin.Regardless of repeatability,stability and linearity,GO-TCPP is higher than TCPP,TCPP-g-C3N4 sensor,and has the best gas sensing performance for SO2,H2S.Its response value is 6times that of TCPP sensor.It also has excellent selectivity and can detect SO2of 1×10-9(V/V0),H2S of 1×10-8(V/V0),the reason may be the huge role of GO transporting electrons.By changing the conditions of mass ratio(TCPP:g-C3N4),rotation speed,p H,free-TCPP-g-C3N4,J-TCPP-g-C3N4,H-TCPP-g-C3N4sensors were prepared,which can detect SO2of 1×10-7(V/V0),1×H2S of 10-6(V/V0),and the morphology of the H-TCPP-g-C3N4 film after interacting with SO2and H2S was observed by SEM.The mechanism is the protonation-deprotonation process,but its gas-sensitivity performance is not as good as the TCPP sensor,and the reason may be that the simple surface sensitization method failed to improve the high carrier recombination rate of g-C3N4.(3)Among the three sensors,the GO-TCPP sensor has the most excellent gas-sensing performance for SO2.In the process of electrochemical gas sensing,it also has good selectivity for SO2.Therefore,it was applied to the detection of actual samples(tremella)containing SO2,and comparison was made using the national standard method.The experimental results show that the GO-TCPP sensor can detect SO2of2.85×10-10(V/V0)in the sample.The national standard method used the iodometric method to measure the SO2in the sample at 0.2059 g/L.The detection method of the optical waveguide sensor is simpler,and the sample does not need to be destroyed.We hope that this sensitive element can have a broad prospect in detecting SO2 in food. |
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