Construction Of PEDOT Based Composite Film Sensor And Its Application For Gaseous H₂O₂ Detection

Hydrogen peroxide（H₂O₂ aqueous solution）is one of the most commonly used reagents in medical sterilization,environmental disinfection,food storage and other fields,but improper use will also cause serious harm to biological health and environmental safety.There are many detection methods for H₂O₂,including colorimetric method,electrochemical method,enzymatic chemical method and fluorescence analysis method.However,these methods are mostly based on the detection of H₂O₂ in liquid phase system,and lack of simple,convenient,real-time and efficient gas phase H₂O₂（HPV）detection technology.At present,the detection of H₂O₂ in the gas phase system is mainly based on fluorescence/colorimetric sensors,which have high sensitivity and selectivity.However,there are great challenges in the molecular synthesis of sensing materials and material engineering.In contrast,the chemresistance sensor has the advantages of simple and convenient in the field of gas sensor,and the response mode of its electrical signal is easier to realize real-time monitoring of HPV.However,the current chemresistance sensor of HPV is mainly based on metal oxide semiconductor materials,which usually require high working temperature（usually 200°C～500°C）.For a long time,the development of HPV sensitization detection materials and technologies with high humidity stability,high sensitivity and high selectivity in conventional environment is still the core and a huge challenge in this field.Poly-（3,4-ethylenedioxythiophene）:polystyrene sulfonate（PEDOT:PSS）is one of the most successful commercial and widely used conductive polymers.As a new sensing material,PEDOT:PSS is often combined with other materials to be widely used in the detection of various gases（moisture,ammonia,CO,NOx,etc.）at room temperature,and the sensing of H₂O₂ in liquid phase system.Its powerful processing ability and excellent photoelectric properties will provide great opportunities for HPV detection（coexistence with humidity and oxidation）,but the hygroscopicity of PEDOT:PSS will also affect electronic devices.Therefore,based on the study of PEDOT:PSS film for HPV detection,a series of PEDOT-based composite films were prepared by electrochemical polymerization,self-assembly and other technical methods combined with perylene diimide（PTCDI）with high chemical stability or the characteristic response material ammonium titanate（ATO）for H₂O₂ colorimetric detection.The resistance response,colorimetric response and the influence of humidity components on the sensing process of HPV detection were analyzed.Finally,this paper realizes the high humidity stability,high sensitivity and high selectivity of HPV detection and direct exposure signal acquisition and dual-mode response at room temperature,which provides a new material,theoretical and structural basis for HPV detection.It is believed that it will greatly promote its future development and practicalityIn the specific research content,this paper carried out the following aspects:1.PEDOT:PSS aqueous dispersion was prepared into PEDOT:PSS film by spin-coating method,and its resistance response and colorimetric response to different concentrations of HPV were explored.It was found that the effect of moisture components in HPV on the resistance response process of PEDOT:PSS film would change with time.The first resistance peak value of the film at the concentration of1.9 ppm is about four times that of the initial resistance value,and the response time is 12 min,which can meet the safety threshold（2.0 ppm,15 min）.At the same time,it was found that the film had a colorimetric signal response to HPV in the detection process.With the increase of HPV concentration,the film showed visible color changes,and gradually became transparent and less blue.Among them,at the HPV concentration of 1.9 ppm,the colorimetric response（ΔE）of the film before and after exposure was 3.03,and the color change of the film could be identified by the naked eye.2.In order to improve the moisture stability of PEDOT:PSS film,a series of PEDOT:PSS/PEDOT composite films were finally obtained by electrochemical polymerization in acetonitrile-tetrabutyl ammonium hexafluorophosphate（ACN-Bu₄NPF₆）（0.1 M）system.By studying the sensitization resistance response of the composite film to different concentrations of HPV,it was found that the hydrophobic porous PEDOT layer improved the influence of humidity components in HPV on PEDOT:PSS to a certain extent,and improved the electrical response to HPV.At 1.0ppm HPV concentration,the resistance signal response was increased by nearly 89%compared with the pure PEDOT:PSS film.However,the presence of PEDOT layer showed a negative effect on the colorimetric response of HPV detection.At 10.5 ppm HPV concentration,the colorimetric response of the composite film before and after exposure was only 2.08,and the color change could only be slightly detected by the naked eye.3.In order to improve the sensitivity and reliability of HPV detection,PEDOT:PSS-ATO and PEDOT:PSS-ATO/PEDOT composite films were prepared by adding ATO into PEDOT:PSS aqueous dispersion,and their sensitizing resistance-colorimetric dual-mode signal response to HPV was realized.The addition of ATO makes the color change of the film more abundant before and after HPV exposure.The change of the film from blue to yellow-green can be observed by naked eyes,and the sensitivity is higher.At 1.9 ppm HPV concentration,the resistance value of PEDOT:PSS-ATO/PEDOT composite film at 9 min is more than three times the initial resistance value,which can meet the requirements of safety threshold（2.0 ppm,15 min）.The colorimetric response of the film is 2.55,and the color change at this concentration can be distinguished by naked eyes,which improves the application prospect of HPV detection under the safety threshold.4.In order to better weaken the influence of humidity on the detection of HPV and the influence of oxidation on the stability of the sensing material,PTCDI derivatives PTCDIs（PTCDI-1:N,N-bis（cyclohexyl）-PTCDI,PTCDI-2:N,N-bis（dodecayl）-PTCDI）with non-hygroscopicity and high chemical stability were combined with supramolecular self-assembly technology.Firstly,PTCDIs nanofiber thin film electrodes were prepared on the surface of ITO glass electrodes.Then,PTCDIs@PEDOT composite films were prepared by electrochemical polymerization in ACN-Bu₄NPF₆（0.1 M）electrolyte system.The photocurrent test showed that photoinduced electron transfer and charge separation occurred between PTCDIs nanofibers and PEDOT,which was helpful to improve the sensitization resistance response of the composite film to HPV.The composite film has a nano-sized N-P heterojunction interpenetrating network structure,which is beneficial to the full exposure and contact of HPV.The response time is 5.76 min,the recovery time is5.53 min,and the response to 1.0 ppm concentration of HPV is 1.76.