Preparation Of ZnO@Co Doped ZIF-71 Composite And Its Gas-sensitive Response To Acetone

In recent years,due to the improvement of living standards and irregular diet,more and more people have started to suffer from diabetes.Diabetes requires early detection and early treatment.However,current diabetes testing devices need to collect patients' blood,which has the risk of cross infection,so a convenient and low-risk detection method is urgently needed.Under this background,the gas sensor has obtained the opportunity of rapid development.As an emerging gas sensor material,MOFs material has become a hot research topic with its unique advantages.This paper mainly studies the gas-sensitivity of Zn O @ ZIF-71 in MOFs to acetone.In this paper,Zn O @ ZIF-71 was synthesized by gas phase transfer method and hydrothermal method.First of all,in the gas-phase transport method,Zn O @ZIF-71 thin films with different thicknesses were prepared by adjusting different heating temperatures and heating times.In this paper,the heating temperature of the sample prepared by gas phase method is controlled within 180 ?,and the heating time is controlled within 24 hours.After characterization and comparison of all samples,it was found that when the control sample was heated at the same heating temperature and only the heating time was increased,the Zn O @ ZIF-71 film of the prepared sample thickened with the extension of the heating time.When the sample is controlled under the same heating duration,the Zn O @ ZIF-71 film of the prepared sample thickens with the increase of heating temperature.The sample with the best shape and performance is the one heated at 130 ? for 4h.The response of the sample to acetone increased by 72%,and the response values to ammonia,hydrogen,ethanol and benzene decreased by 4%,33%,43% and 49%,but the sample had poor crystallinity and low stability The problem.Afterwards,in view of the problem of poor crystallinity of the samples synthesized by the gas-phase transport method,the hydrothermal method was used to improve the crystallization performance of Zn O @ZIF-71.Finally,in this paper,different doping methods were used to study cobalt-doped samples prepared by gas-phase transport and hydrothermal methods,and Zn O @Co-doped ZIF-71 composite was synthesized.SEM characterization of samples doped with different methods can show that samples prepared by different methods have different morphologies after cobalt doping.The samples synthesized by hydrothermal method can see complete cobalt ion polyhedrons on the surface.With the increase of the doping amount,the number of cobalt ion polyhedrons increases;while the samples synthesized by gas phase method will form polyhedron blocks with hybrids.As the amount increases,there will be more hybrids between the polyhedrons.After introducing 20 ppm of acetone gas into the sample synthesized by gas phase transmission method,it can be found that the response value of the sample prepared by gas phase transmission method to acetone gas after adding different concentrations of cobalt nitrate solution increased from 11 to 26,21 and 16.The response value of the material to acetone has been greatly improved by 45%,90% and 136%respectively.At the same time,the results show that when doped with excessive cobalt ions,the gas sensitivity of the material to acetone has a tendency to decline.