The Preparation Of Modified Graphene Oxide And Gas Sensitivity Study

As a new type of two-dimensional crystal material,graphene has a unique structure and excellent properties,such as ultra-high specific surface area,excellent electrical conductivity,high surface adsorption capacity and so on.When used for gas molecular detection,graphene has a lot of advantages,such as good electrical characteristics,higher sensitivity and lower detection limit.So it has broad application prospects in gas sensing.In addition,the sensing properties of graphene-based gas sensor could be further improved by combining pure graphene and other functional gas sensing materials.Graphene oxide is an oxide of graphene,and it has good semiconductor properties and rich oxygen-containing functional groups.Compared with graphene,graphene oxide-based sensors have high chemical activity and abundant adsorption sites,which is more conducive to the adsorption of gas molecules.In this paper,the gas sensing material was developed with reduced graphene oxide and metal oxide nano-materials composites.And based on the micro-hybrid electrode,a resistive composite membrane sensor is prepared.The gas-sensing characteristics of devices were systematically studied,and the gas-sensing mechanism model was established.The main contents and results of the study are as follows:1.The graphene oxide and zinc oxide/reduced graphene oxide(ZnO/rGO)composites were prepared by Hummers method and hydro-thermal reaction method respectively.The scanning electron microscopy,transmission electron microscopy,X-ray diffraction and Raman spectroscopy characterization methods were used to do characterization on the morphology and structure.2.Based on resistive ZnO/rGO composite film sensor,the gas sensing properties of ethanol were studied at room temperature,and the dropping amount of ZnO/rGO composite solution was optimized.When the suspension concentration was 5 g/L and 10 ?L solution was added,the composite membrane sensor possessed the best sensing performance.The sensor showed the highest responsivity and the shortest response time and recovery time.When the ethanol vapor concentrations were 25 ppm,50 ppm and 75 ppm,the corresponding responsivities were 10%,26% and 49%,respectively.When the ethanol vapor concentration was higher(eg: 100 ppm),it was difficult to return to the initial state,the material became less stable,the reversibility and recovery performance became worse.3.Microwave-heated ZnO/rGO composite films were used to study the response-recovery characteristics of ethanol.After heated at low fire or medium temperature,it was beneficial to improve the gas sensitivity.Compared with non-microwave heated composite films,the heated composite films had better response-recovery characteristics to ethanol vapors at different concentrations.The limit of the detectable vapor concentration was lower,the responsivity was higher,the recovery and repeatability were better,but the response and recovery time were longer.Among them,the sensing films which were heated at medium temperature had the highest responsivity.When the ethanol vapor concentrations were 10 ppm,25 ppm,50 ppm and 75 ppm,the corresponding responsivities were 21%,34%,44%,and 53%,respectively.The ZnO/rGO composite films treated with different microwave heating times were also usedto investigate the response-recovery characteristics of ethanol.The responsivity of the gas sensor would increase first and then decreased with the increase of the microwave heating time.When the heating time was 4 minutes,the responsivity was the highest,reaching 20%,34.6%,and 46% respectively at the concentrations of 20 ppm,40 ppm,and 60 ppm.When the heating time was longer,the responsivity of the sample would decrease.4.Microwave-heated ZnO/rGO composite films were also used to study the selectivity of ethanol.The response-recovery characteristics for four steams were tested,they were ethanol,methanol,acetone and ether.Composite films had relatively larger responsivities to methanol and ethanol vapors,and their responsivities could reach 10% when the concentration was as low as 10 ppm.For acetone and ether vapors,when the steam concentration was 75 ppm,the responsivities were still less than 10%.Therefore,the composite films had the best selectivity to alcohols.