Study On The Synthesis Of Zinc Metastannate Composite Material Assisted By Sodium Alginate And The Gas-sensing Properties Of Formaldehyde

Formaldehyde is extremely harmful to the human body.Short-term exposure to formaldehyde can cause discomfort to the human body,irritate the respiratory organs,and long-term exposure to formaldehyde-exceeding environments will cause liver and kidney poisoning,increasing the possibility of cancer,leukemia and even death.Zn Sn O₃,as a typical multi-metal oxide with a perovskite structure,shows good gas-sensing performance in the detection of formaldehyde compared with a single metal oxide,but most of the current research in this area requires a higher working temperature.In this paper,sodium alginate-assisted synthesis of Zn Sn O₃ is used as the main research object.Based on this,composite materials are modified to improve the gas-sensitive properties.The thesis mainly includes the following:1.Zn Sn O₃ microspheres were prepared by a simple hydrothermal synthesis method with the assistance of biopolymer sodium alginate（SA）.From the scanning electron microscopy（SEM）test chart,it can be analyzed that the addition of SA changes the structure of the microspheres,and the addition amount affects the size distribution of the microspheres.In addition,the product was analyzed by thermogravimetry（TG-DTG）,X-ray diffraction（XRD）and X-ray energy spectroscopy（EDS）.The material was sprayed on the interdigitated electrode for gas-sensitive detection.Under the excitation of ultraviolet light,the sensor based on Zn Sn O₃@4g/L SA（ZS4）responds to 20ppm formaldehyde at room temperature with a value of 12.3,while showing excellent linearity response and good long-term stability.2.Alginate-assisted Zn Sn（OH）₆ precursor was prepared by hydrothermal method,and then Ni O was modified on the surface of ZS4 microspheres through simple solution reaction and heat treatment.Through the adjustment of factors such as modification with different metal oxides,different synthesis methods and different Ni O content,combined with the characterization of the product and the analysis of the gas sensitivity test results,the optimal sample was finally determined as 0.5wt%Ni O-ZS4 composite material obtained by secondary annealing.The gas sensor based on composite material has a response value of about 14.2 at 20 ppm formaldehyde,has good repeatability and certain selectivity.3.Surface-modified Au-ZS4 microspheres were successfully synthesized by hydrothermal method,solution reaction and heat treatment.Through XRD and SEM tests,it can be seen that Au is only deposited on the surface of microspheres as elemental metal and will not be incorporated into the lattice of ZS4,and the appropriate amount of Au modification will not change the overall morphology and structure and will cause the microspheres surface rougher,thus providing more active adsorption sites.The gas sensitivity test results show that the sensor based on the0.2wt%Au-ZS4 sample has the best response characteristics,the response value can reach 18.8 in HCHO at 20 ppm,and it shows good linearity in the range of 5-20ppm,and has good repeatability.