The Building Of Multi-tier Nested Tin Dioxide Nanoparticles And Ag Doped Zinc Oxide And Gas Performance Research

Ethanol?C₂H₅OH?,a gas with stimulating odour,is the most common aliphatic alcohol which has been widely investigated in gas sensing field for its diverse and practical applications in biomedicine,hospital,wine industry,breathalyzers,traffic safety,laboratories,etc.Meanwhile,ethanol can also cause health issues,such as skin and eyes irritation,nausea,vomiting and central nervous system depression.It is the reason why our team focus on the study of ethanol gas sensor in our work.The working mechanism of the gas sensor relies on transport of electrons due to surface reactions such as oxidation or reduction caused by different gas exposures.When the samples are placed in the air,oxygen molecules will be absorbed to the inner and outer surface of sample,trapping electrons from conduction band and creating chemisorbed oxygen species.It will generate an electron depletion layer on the surface,resulting in a high resistance of the material.Both SnO₂ and ZnO are the important gas sensing materials.Due to the advantage of thermostability,anticorrosion and low cost,these materials have been widely studied.Therefore,the study of factors which are affecting sensing properties has guiding significance in the practice.The detailed information of the dissertation is listed as follows.1.Polyhedral-like Tin dioxide?SnO₂?with exposed high-energy was fabricated by a simple hydrothermal route.The structures,morphology and gas sensing properties were characterized by X-ray diffraction?XRD?,scanning electron microscope?SEM?,transmission electron microscopy?TEM?and gas sensing measurement system.The XRD studies indicated that the as-prepared samples had well crystallized,the SEM and TEM studies demonstrated that the sample of multi-tier nested Tin dioxide with polyhedral-like nanoparticles were fabricated successfully.In addition,the present study could be applied to the ethanol detection at a low temperature,because of its unique structures.2.Controllable ZnO architectures nanostructures were synthesized via a facile hydrothermal method and the morphologies achieved included spheres and sea-urchin-like nanostructures with the different reaction time of 16 h and 24 h.The structural,elemental composition and morphology were investigated by X-ray diffraction?XRD?,energy-dispersive X-ray detector?EDX?,scanning electron microscopy?SEM?,transmissionelectronmicroscopy?TEM?and Brunauer–Emmett–Teller?BET?.The XRD studies demonstrated that the these samples had well crystallized and showed that they were composed of ZnO nanoparticles and Ag ions were also successfully doped into the ZnO lattice.The SEM and TEM studies indicated that the samples of spheres and sea-urchin-like nanostructures were obtained successfully.In addition,the sensor based on this sea-urchin-like ZnO nanostructures exhibited perfect sensing performance toward ethanol with high sensitivity,quick response and good selectivity than the sensor based on the ZnO nanosphere sample owing to its larger specific surface area,which were showed by BTE.Furthermore,the samples of Ag doped,which were higher response and lower optimum operating temperature than the previous reports?Table1?.The gas sensing results showed that the sensor response?S=R_a/R_g?reached to be22 to 10 ppm ethanol at the optimum operating temperature of 260^oC.Finally,the possible formation mechanism of sea-urchin-like ZnO nanostructures and the gas-sensing mechanism of sensors were discussed,too.