Preparation Of Toluene Gas Sensors

VOCs (volitile organic compounds) gases have become one of the pollutants in air.As one of VOCs gases, toluene was a serious threat to human health and naturalenvironment. The main gas-sensing material for VOCs gases were as follows: metaloxides, polymers and polymer/inorganic composites. Polymer/inorganic composites cannot only be modified, designed and synthesized for gas sensors, but also can becombined with inorganic materials to improve the selectivity, sensitivity, stability andother parameters. As one kind of the gas-sensing materials, it can be used at roomtemperature. With the increasingly serious air pollution problems, a toluene gas sensorwith low-cost, intelligent, high sensitivity and stability is required to be developed.Polymer/inorganic sensitive materials were deposited on interdigitated electrodes byspraying process to construct the resistant gas sensors to detect toluene vapor at roomtemperature.The main research was as follows:Polymer/inorganic composite film had be prepared by spraying and spin coatingmethod respectively, and they were used to detect the toluene gas vapor at roomtemperature. It was found that the gas sensor with P4VP/MWNTs composite filmprepared by spaying process has better sensing properties compared with thecounterpart prepared by spin coating. The P4VP/MWNTs composite film has bettersensing properties compared with the P4VP/CB composite film. The experimentalresults was also discussed combined with the microstructures of the films characterizedby scanning electron microscopy (SEM).Gas sensors with polymer/inorganic multi-layer films had been prepared, and theirsensing properties to toluene gas vapor at room temperature had been discussed. Theresults showed that the response of the polymer/inorganic multilayer films had a goodlinearity with the concentration of toluene. The PEO/MWNTs bilayer films have bettersensing properties compared with the P4VP/MWNTs bilayer films. The PEO/MWNTsbilayer films have better sensing properties compared with the PEO/MWNTs compositefilms. Both the PEO/MWNTs three layer films and the P4VP/MWNTs three layer films have better sensing properties compared with their bilayer films. The results showedthat PEO film was more sensitive to toluene gas than P4VP film with the same filmstructure. The selectivity of the three-layer film sensor was further investigated bycomparing responses upon exposure to different interference vapors with the responseto toluene exposure, and much higher response was observed in the case of toluene.Good repeatability of the PEO/MWNTs three layer films sensor was also observed,while the P4VP/MWNTs three layer films almost kept stable with a little decay. Therelated sensing mechanism was also studied in detail combined with the SEM andvisible spectroscopy.