Novel Gas/Humidity Sensor Based On Graphene Oxide Composite Materials

The gas/humidity sensor has a wide application prospect in the fiel ds of public safety,human health and environmental monitoring.It is an important research direction to increase the adsorption capacity of testing gas or humidity and improve the sensitivity of the sensor by using the characteristics of large specific su rface area and high reactivity of nanomaterials.Some nanomaterials(especially carbon nanomaterials)are prone to agglomerat e in most solvents(water,ethanol).This makes the actual specific surface area of carbon nanomaterials much lower than their theoretical values,which leads to the limited performance of the sensors based on carbon nanomaterials.Graphene oxide(GO)is a two-dimensional nanomaterial consisting of carbon atoms with large specific surface area.It has good solubility in most aqueous solvents and is a very promising dispersing agent for insoluble carbon nanomaterials.In this dissertation,GO is used as a dispersant to study the dispersibility of several nanocarbon materials in it.We present several types of gas/humidity sensor s based on GO composite films.The synergistic effect between the nanocomposite materials,the ionic conductivity and other sensing mechanism are also discussed.The main content can be summarized as follows:(1)The solubility of fullerene(C60)in GO aqueous solution is studied.We obtain a uniformly dispersed GO /C60 composite solution.Based on this,a GO/C60 humidity sensor is constructed on the interdigital electrodes(IDEs).In this study,the interaction between GO and C60 is used to inhibit the aggregation of C60 and enhance its dispersion in compound solution,so as to increase the specific surface area of GO/C60 composite material and improv e the humidity sensitivity of GO/C60 humidity sensor.The test results show that,com pared with the C60 humidity sensor,the GO/C60 humidity sensor has better sensitivity while maintaining high stability.This part of the work provides a foundation for the research on the humidity sensor which based on nanocarbon materials with GO as a dispersant.(2)The GO/MWCNT dispersion is investigated by using GO aqueous solution as solvent.Then a GO/MWCNT humidity sensor is constructed on the IDEs.The study shows that the GO/MWCNT sensor has the highest sensitivity among the sensors built on the three sensitive membranes(GO,MWCNTs and GO/MWCNT).Combined with the microstructure characteristics of GO/MWCNT sensitive films,the synergistic effect between the two materials in GO/MWCNT composite sensitive films is studied and the response mechanism of the sensor is explained.(3)Based on the quartz crystal microbalance(QCM)technique,a high-sensitive GO/MWCNT modified QCM humidity sensor is presented.The sensor is realized by the change of both the mass and the mechanical modulus of the GO/MWCNT sensitive film.Combined with the impedance test and the change of the equivalent circuit parameters,the influence of the sensing film properties on the characteristics of the sensor is analyzed.(4)A method of adding an electrode isolation layer on QCM gas sensor is proposed.PANI layer works as ammonia sensitive layer while high elastic modulus GO film works as an isolation layer.In this way,a new double-layer structure GOPANI film modified high stability QCM ammonia sensor is prepared.The sensitivity,dynamic response and recovery characteristics of the GO-PANI ammonia sensor are studied by scanning frequency and oscillating circuit method s.Further analysis of the complex impedance equivalent circuit shows that the QCM with double-layer GO-PANI films can maintain a high quality factor in different ammonia concentration.This study provides a new idea for the construction of a high stability QCM ammonia sensor.