| Nitrogen dioxide?NO2?is a typical threatening atmospheric pollutant,which is seriously harmful to the environment and human health.Moreover,NO2 could be used to diagnose the asthma by measuring the patient`s exhaled concentration level of NO2?ppb?in the medical field.Therefore,many researchers have been working on the development of high-performance NO2 gas sensor for accurate detection of low concentration NO2 at low temperature.Gas sensor based on semiconductor metal oxide have been widely studied due to the advantages of low cost,small size and high response.However,it is still difficult to develop NO2 gas sensor with high response and low detection limit at low operating temperature.Receptor function,transducer function and utility factor are the main factors that can determine the sensing performance of semiconductor metal oxide.These factors are strongly affected by the specific surface area of the sensing material,the gas diffusion rate and the interaction of the semiconductor surface and the target gas.Therefore,it is a good method to improve sensitive characteristics by designing microstructure of material and modifying surface of material to enlarge the specific surface area and improve the reactivity.In this paper,we firstly prepared ordered mesoporous indium trioxide?In2O3?to improve specific surface area,increase the active site and accelerated speed of the diffusion rate.Then,Au nanoparticles were employed to Au modify mesoporous In2O3.The chemical and electronic sensitization effects of noble metal Au were used to enhance the interaction of In2O3 surface and target gas,and thus the sensing performance of gas sensor was improved.The main contents are as follows:1.The highly ordered mesoporous structure of SBA-15 silicon oxide,which was used as hard template,had been successfully replicated by simple nanocoating method.The prepared mesoporous In2O3 were characterized by the XRD,BET,TEM.Characterization results showed that the prepared materials had large specific surface area with 42.32 m2/g,small grain size and good ordered mesoporous structure.Moreover,compared with the In2O3 material prepared by the conventional method,mesoporous In2O3 exhibited better gas sensitivity characteristics in terms of both response and operating temperature.For 500 ppb NO2,the response of gas sensor based on mesoporous In2O3 is 62.5,and the response is 9.7 times than that of conventional In2O3.In addition,the optimum operating temperature of mesoporous In2O3 is reduced to 75?.The ordered mesoporous structure enlarged the specific surface area of the material,the porous structure facilitated the diffusion of gas,and framework structure of mesoporous material inhibited the growth of In2O3 grains,which are the main reasons for improving the gas sensing performance of sensitive materials.The experimental results showed that the ordered mesoporous structure is beneficial to improve the performance of NO2 sensor based on In2O3.2.On the basis of mesoporous In2O3,noble metal Au nanoparticles with different mass rations were successfully modified on the surface of the material by impregnation method,and the effect of Au mass on the sensing performance toward NO2 was also investigated.The results of system`s sensitivity test showed that gas sensor based on the mesoporous In2O3 modified with 0.5wt%Au exhibited the best sensing performance.For 500 ppb NO2,the sensor based on 0.5wt%Au-In2O3displayed the best response as highest as 472.4,and the detection limit as low as10 ppb at optimal operating temperature of 65?.The chemical and electronic sensitization effect of the Au promotes promoted the interaction of gas and sensitive materials,which is the main reason for further improving the sensing performance of sensitive materials.Therefore,the modification of noble metal Au on the surface of In2O3 can be an effective means to improve the performance of NO2 sensors. |
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