Study On Graphene Gas Sensors Fabricated By Self-assembly Techniques And Their Sensing Properties

Large surface area,high electron mobility and low internal electronic noise of graphene materials,which makes up for the shortcomings of other gas sensing materials,lead to its great application prospect in the field of gas sensors.In this thesis,we studied two kinds of graphene gas sensors fabricated by self-assembly method and techniques.Details are as follows:Gas sensors based on self-assembled graphene films were fabricated and studied.The negatively charged GO was prepared by the modified Hummers method.The positively changed rGO was fabricated by reduction of GO with PPD.The negatively charged GO and positively charged rGO were assembled on the electrode successively by electrostatic self-assembly method.Followed by reduction of GO by pyrrole vapors,the r?GO/rGO?₁₀ sensor with good response to DMMP was obtained.The results of gas sensing tests reavealed that the r?GO/rGO?₁₀ sensor had good response to DMMP.Meanwhile,the device showed excellent selectivity and stable repeatability.The response of the r?GO/rGO?₁₀ sensor under50 ppm DMMP could reach up to 7.75%.Exccitingly,there was still a 2.18%resistance change when the DMMP concentration was as low as 1 ppm.The repeatability test results of r?GO/rGO?₁₀ sensor under the 50 ppm DMMP indicated that the sensor had good repeatability.As purging of pure air,the resistance of the sensor could be recovered to the initial value within 4 min.In addition,the response of r?GO/rGO?₁₀ sensor to DMMP was more than four times higher than that of other high concentration gases,indicating that the r?GO/rGO?₁₀ gas sensor had excellent selectivity.Gas sensors based on self-assembled porous graphene films were fabricated and studied.The negatively charged holey GO solution was prepared by the UV-catalyzed Fenton reaction.The positively charged holey rGO solution was obtained via reduction of GO.The porous?GO/rGO?₁₂ gas sensors which demonstrated a good response to DMMP was obtained by self-assembly techniques.The resultant sensor exhibited 9.05%and 2.11%resistance variation towards 50 ppm and 1 ppm DMMP respectively.In addition,the porous?GO/rGO?₁₂ gas sensor not only had good repeatability but also had excellent selectivity,the desorption time of 50 ppm DMMP is just about 3 min and the response value to the 50ppm is more than 4 times higher than that of other gases.Above all,the devices demonstrated high responses,good selectivity and repeatability under normal temperature and pressure.Moreover,the preparation of the two types of gas sensors and the concerning gas sensing materials were simple,convenient,and low cost,highlighting the great potentials of the devices in the field of DMMP detection.