Studies On Morphology And Structure Control Of In₂O₃ And Gas Sensing Properties

Nanomaterials and nanostructures are very important research target in present fields of materials,especially they have become research hot spot in fields of nanotechnology nowdays because of their novel physical,chemical,biological characteristics and novel potential applications in nanometer devices.For the synthesis of nanomaterials,liquid-phase method has been widely used in the preparation of nanoparticles because it is easy to control nucleation,uniform composition and component,and can be obtained high purity nano-oxides.In this paper,In₂O₃ nanostructures,including nanorods,nanowires,and mesoporous morphology and structure were prepared by liquid-phase method with different surfactants.The morphology and structure of the materials synthesized were characterized.Various reaction parameters,such as morphological controlling agents, reaction temperature and time,were studies in this work.The growth mechanism of In₂O₃ with different nanostructures was discussed.The gas-sensing properties of In₂O₃ with different morphology were studied by using the side-heated gas sensors.The relationship between structure of In₂O₃ materials and gas-sensing properties was discussed.Main achievements of this paper:1.In₂O₃ nanorods were prepared by controlling the kinetics parameters in reaction process and using polyethylene octyl phenyl(OP-10) as a controlling agent of morphology,InCl₃·4H₂O and ammonia as the raw materials.The results indicated that In₂O₃ nanorods had the length of about 120nm and the diameter of about 20nm.Studies on the factors influencing growth of In₂O₃ nanorods showed that reaction temperature played a key role in controlling the length of In₂O₃ nanorods,and the concentration of morphological controlling agents affected the dispersion of nanorods.Discussion of the formation mechanism showed that the geometric arrange parameter of OP-10 was in 1/3-1/2,it could form claviform micelle.So at the appropriate reaction temperature and concentration,In₂O₃ nanorods were prepared. 2.The gas sensing properties of In₂O₃ nanorods were measured by mixing detected gas and air in static state.The testing results showed that In₂O₃ nanorods had higher sensitivity and selectivity to trimethylamine(TMA) at 130℃;good sensitivity to C₂H₅OH,CH₃OH,CH₃COCH₃,HCHO at 260℃but low selectivity;higher sensitivity and selectivity to H₂ at much higher temperature;then little response to NH₃ and C₄H₉. The analysis of gas-sensing mechanism was indicated that In₂O₃ nanorods had higher sensitivity and selectivity to trimethylamine at low temperature due to its strong ability to supply electrons.3.Multi-dimensional compound In₂O₃ materials with porous overhead structure were first prepared by dopping In₂O₃ nanorods with 5wt.%ZnO,SnO₂ and In₂O₃ nanoparticles and controlling the sintering conditions.The results of gas-sensing test showed that multi-dimensional compound In₂O₃ materials could improve the sensitivity and selectivity,and decrease the power consumption;especially had good response to trimethylamine which make it possible to develop trimethylamine sensor with high sensitivity and selectivity.Analysis of gas-sensing mechanism for the compound showed that porous overhead structure could enlarge effectively specific surface area,and form support of adsorption reaction,overcome resistance of eiectronic migration so it could improve gas sensing properties.4.Mesoporous indium oxide were prepared by simple sol-gel technique with three block copolymer PE6800 as a agent of controlling their morphology,H₂O as a solvent and indium chloride as a precursor.The decomposition process,crystal structure and micro-morphology of samples were characterized by TG-DSC,XRD,SEM,TEM and BET.The influence factors of forming mesoporous In₂O₃ were discussed.The results of gas-sensing test showed that In₂O₃ nanorods had good sensitivity to C₂H₅OH, CH₃OH,HCHO,NO₂;especially except for good sensitivity to C₂H₅OH and had better response-recovery properties,so they were promising to be used in C₂H₅OH detection. The effects of reaction temperature and porous structure on gas-sensing properties were discussed.Compared with In₂O₃ nanoparticles,we found that gas response of the sensor based on mesoporous In₂O₃ materials was higher than that of In₂O₃ nanoparticles.5.In₂O₃ nanowires with high aspect ratios(＞40) were synthesized via hydrothermal-annealing route.The gas-sensing measurement showed that the sensor based on In₂O₃ nanowires had excellent gas-sensing properties to NO₂ which make it favorable to be used in environmental protection,exhausting gas monitor and so on.