Study On Improving The Acetone Sensing Performance Of ZnO Nanoparticles

ZnO is a kind of important n-type semiconductor sensing material,which has the advantages of low cost,non-toxic availability and good biocompatibility.It has been widely used in many fields,especially in gas sensing.In order to find an effective method to improve the gas sensitivity of ZnO nanomaterials and solve the problems of low gas response value and high operating temperature of ZnO semiconductor sensors in practical application,we prepared Fe-ZnO,In₂O₃/ZnO and Fe₂O₃/ZnO nanomaterials by sol-gel method,and we also prepared Zn Fe₂O₄/(Fe-ZnO)and In-ZnO nanomaterials,which are derived from MOF-5 by solvothermal method.Then we studied the above preparation methods on the acetone gas sensitivity of ZnO semiconductor.The main conclusions of this paper are as follows:1.Fe-ZnO nanoparticles were prepared by sol-gel method according to the molar ratios of Fe and Zn(0,1 mol%,5 mol%and 10 mol%).Compared with pure ZnO,the gas response of Fe-ZnO nanoparticles was improved.The response values of 5 mol%Fe-ZnO to 100 ppm acetone gas was the highest at220?.The main reason may be that the doping of Fe³⁺increases the concentration of electrons on ZnO surface and enhances its oxygen adsorption capacity.On the other hand,Fe enter ZnO lattice and destroy the original lattice arrangement of ZnO,forming a mismatch lattice with higher energy and increasing the adsorption sites.So the surface adsorption oxygen coverage increases,the gas response increases.2.In₂O₃/ZnO nanoparticles were prepared by sol-gel method according to the molar ratios of In and Zn(0,1 mol%,5 mol%and 10 mol%).(x)Fe₂O₃/(1-x)ZnO(x=0,5 mol%,10 mol%,15 mol%,20 mol%and 100mol%)was prepared by sol-gel method.The results of gas sensitivity test showed that compared with pure ZnO,the 5 mol%In₂O₃/ZnO and5%Fe₂O₃/95%ZnO nanometer materials had lower resistance,larger gas response value,faster response speed,and showed excellent selectivity of acetone.The reasons for the enhanced gas response may be related to the formation of n-n heterojunction at the interface.3.MOF-5 was prepared by solvent heat method.The gas response value of the pure ZnO calcined by MOF-5 was higher than that of the pure ZnO nanoparticles prepared by sol-gel method.Meanwhile,the response recovery rate and selectivity of acetone were better than that of the pure ZnO prepared by sol-gel method.It indicates that this preparation method may adjust the morphology and structure of ZnO,and it is an effective way to improve the gas sensing characteristics of semiconductor ZnO.4.According to the molar ratio of Fe and Zn(x=0,0.05,0.10,0.15,0.20,0.25 and 0.30),MOF-5 was hydrolyzed in an iron nitrate solution and calcined to obtain Zn Fe₂O₄/(Fe-ZnO)nanoparticles.The response value of Zn Fe₂O₄/(Fe-ZnO)nanoparticles at x=0.15 to 100 ppm acetone gas at the optimal operating temperature is four times that of the maximum response value of MOF-5 calcined ZnO nanoparticles,and it has excellent stability and selectivity.Through SEM,XPS and XRD,it was concluded that the introduction of iron ions in Zn Fe₂O₄/(Fe-ZnO)resulted in ZnO defect lattice,the interface between zinc oxide and Zn Fe₂O₄,and the grain boundary between Zn Fe₂O₄ nanoparticles were conducive to the adsorption of oxygen and acetone,and the Fe atoms on the ZnO surface also promoted the adsorption of oxygen.In accordance with the same method and the molar ratio of elements,MOF-5 was placed into indium nitrate aqueous solution for hydrolysis and calcination,and the product was proved to be In-ZnO nanoparticles after XRD.Compared with the MOF-5 calcined pure ZnO nanoparticles,the In-ZnO nanoparticles with x=0.05 have higher acetone gas response value and shorter response recovery time,and the device also has better stability and selectivity.The reason for the increase gas response value may be that the introduction of In leads to ZnO lattice defect,which produces more adsorption sites and increases the oxygen adsorption capacity.