Fabrication Of Tin Oxide Hierarchical Structure And Their Gas-Sensing Characteristics

The highly sensitive gas sensors become necessary equipment more than ever in the areas of environmental monitoring and disease diagnoses at present.The gas sensors with the oxide of tin have always been the hot spot in the research field of highly sensitive gas sensors due to low cost and widefunctions.In this paper,several of tin oxide semiconductor micro-nanostructure materials with unique morphology were prepared by hydrothermal strategy,and measured in terms of gas sensitive properties.According to the law of Gibbs-Wulff crystal growth and adsorption and desorption model,the possible corresponding growth mechanism and sensitive mechanism were proposed,respectively.The influence on the morphology and sensitive response were surveyed by the optimization of structural and components.The main contents are as follow:Firstly,studied on the preparation of aurelia-like SnO₂ hierarchical micro-nanostructures materials and gas sensitive properties of the sensors,which based on it.This paper discussed the geometric parameters of the sample structure optimization in the different growing conditions by hydrothermal method,such as the proportion of PVP and CTAB to join,growth temperature and time etc.,and obtained the sample of aurelia-like SnO₂ hierarchical micro-nanostructures using optimal growth conditions.According to the law of Gibbs-Wulff crystal growth,the growth mechanism of crystal orientation by the similar soft templates was proposed.At low operating temperature?240 oC?,the response values of the special structure sensors endow enhanced acetone gas sensing performance such as a fast response time?2s?/recovery time?23 s?to 10 ppm,high sensitivity?100 ppm,S=30?,good repeatability and good sensing selectivity.Application with the adsorption and desorption model of the superiority geometric parameters explained the gas sensing mechanism of such sensors in this thesis.Secondly,studied on the preparation of cedar-like SnO₂ hierarchical micro-nanostructures materials and gas sensitive properties of the sensors.This thesis discussed the impact in controlling of the sample structure optimization with the sample configuration in the different growing conditions by hydrothermal method and annealing conditions,and obtained the sample of cedar-like SnO₂ hierarchical micro-nanostructures using optimal conditions.According to the law of Gibbs-Wulff crystal growth,the preferred growth mechanism of crystal orientation was put forward.The special structure sensors endow with good gas sensing performances?100 ppm?in terms of a fast response time?<1s?/recovery time?13 s?,high sensitivity?30?,good repeatability,and excellent sensing selectivity at lower working temperatures?200 oC?.Application of adsorption and desorption model of the configurational superiority explained the gas mechanism of such sensors.Thirdly,studied on the preparation of ultrathin nanosheets SnO₂ nanostructure materials and gas sensitive properties of the sensors.By hydrothermal method,this thesis discussed the effect of crystal grain size adjustment of the sample structure optimization with the sample configuration get through changing the crystal surface energy and controlling the growth time,obtained the sample of ultrathin nanosheets SnO₂ nanostructures.According to the law of Gibbs-Wulff crystal growth,the single crystal growth mechanism with adjusted the surface energy was proposed and combined with the Nucleation Controlled mechanism.The ultrathin nanosheets SnO₂ nanostructure materials sensors show with good gas sensing performances?100 ppm?in terms of a fast response time?<1s?/recovery time?6 s?,high sensitivity?7?,good repeatability,and excellent sensing selectivity at lower working temperatures?240 ??.Application of adsorption and desorption model of the grain size advantage explained the gas mechanism of such sensors.Fourthly,studied on the preparation of SnO-SnO₂ p-N heterostructures materials and gas sensitive performances of the sensors at room temperature.By hydrothermal method,this thesis discussed the effect of the sample composition optimization with controlling of the annealing and oxidation temperature,obtained the sample of p-N heterostructures with SnO-SnO₂ hierarchical micro-nanostructures using optimal conditions.According to the law of Gibbs-Wulff crystal growth,the plausible formation growth with the particle concentration fluctuation,preferential crystal growth and the oxidation was proposed and combined with the Multi-core layer and Diffusion control mechanism.The constitution of heterojunction valence state and the heterogeneous interface were confirmed.This sensor with SnO-SnO₂ p-N heterostructures?annealing 500 oC?exhibited excellent performances for NO2 sensing?0.2 ppm?at room temperatureat and atmosphere pressure.in terms of fast response time?<57 s?,relative sensing selectivity,high sensitivity?2.5?,and low LOD?the limit of detection??0.1 ppm?by a stable and repeatable response pattern as same as the humidity sensitive,measuring and comparing the samples of all sensors sensitivity.The variety models with heterogeneous interface,oxygen vacancy and adsorption and desorption model were presented,explaining to the gas mechanism of such sensors.