Mesostructure Manipulation Of Graphene-mesoporous Metal Oxide Nanocomposite For Gas Sensing

Gas sensors have been used in in wide range of applications including industry,public safety,environmental monitoring and medical diagnosis.Sensing materials with excellent properties are viewed as the key to develop advanced gas sensors.It is of much importance to fabricate the nanocomposite based on mesoporous metal oxide and graphene,which are two types of promising gas-sensing materials.Such the nanocomposite would have some tunable sensing properties related to both the mesostructure,framework composition,surface activity of mesoporous metal oxide and the size,surface functional groups of graphene as well as the ratio of them.A series of ordered mesoporous indium oxide(In2O3)with different mesostructural parameters were prepared through the nanocasting route by using mesoporous silica KIT-6.The effect of the pore size of KIT-6 and the opening size of calcinating containers on the confined growth of indium oxides within two sets of enantiomeric mesopore of KIT-6 were investigated.Indium oxide trend to grow within only one of two sets of enantiomeric mesopores when KIT-6 with small mesopores and calcinating containers with large opening,resulting in mesoporous indium oxide with thin pore walls(5 nm)and large pore size(12 nm),whereas indium oxide trend to grow within both two sets of enantiomeric mesopores when KIT-6 with large mesopores,resulting in mesoporous indium oxide with thick pore walls(9 nm)and small pore size(4 nm).The former exhibited higher response toward formaldehyde than those of the latter.A series of graphene-ordered mesoporous indium oxide nanocomposite were prepared by combining the ultrasonic mixing with the solvothermal reduction.The graphene-ordered mesoporous indium oxide nanocomposite with 0.01%of highly reduced graphene exhibited high response and excellent selective to ethanol.Moreover,the nanocomposite based on mesoporous indium oxide with thin pore walls(5 nm)and large pore size(12 nm)was more sensitive to ethanol than that of the nanocomposite based on the counterpart with thick pore walls(9 nm)and small pore size(4 nm).Mesoporous lanthanum ferrite(LaFeO3)with large pore size of 29 nm was prepared by the sol-gel method and its response toward formaldehyde could be significantly improved by adding 0.01%of graphene.