| Zinc stannate(ZnSnO3)is sensitive to the main indoor pollutants(formaldehyde,benzene,ammonia,and carbon dioxide),and is currently the most important semiconductor metal oxide gas sensitive material in experimental research and commercial applications.However,the direct use of ordinary ZnSnO3 materials for the detection of trace gases has disadvantages such as low sensitivity,high working temperature,poor selectivity and stability.Therefore,it is valuable to control the synthesis of highly active ZnSnO3 nanocomposite materials to improve the electrical conductivity of the material and improve its sensitivity and selectivity.In the paper,three different ZnSnO3 nanomaterials were hydrothermally synthesized with different surfactants,rGO-doped ZnSnO3 composite materials were synthesized by one-step hydrothermal method,and ZnFe2O4/ZnSnO3 composite materials were synthesized by two-step hydrothermal method.The chemical composition,morphological structure and gas-sensing mechanism were analyzed and studied.The details are as follows:(1)Three different ZnSnO3 nanocrystals were successfully prepared by one-step hydrothermal method with different surfactants.Using Na F as an auxiliary raw material,ZnSnO3 nanocrystals with a certain layered porous structure were prepared,and it was observed that the nanocrystal material has the best gas sensing response and the largest oxygen vacancy.In addition,compared with the other two nanocrystal sensors,the ZnSnO3 nanocrystal sensor with Na F as the auxiliary raw material has the best gas sensitivity to formaldehyde gas.This ZnSnO3 with a layered porous structure is expected to become a potential gas-sensitive material to detect formaldehyde gas.(2)Different rGO-doped ZnSnO3 composites were successfully synthesized by one-step hydrothermal method.We used the XRD,FTIR,SEM,TGA,XPS and BET methods to characterize the structure,morphology,thermal stability,chemical composition,and specific surface area of composite materials,and the gas sensing properties to different target gases(ethanol,acetone,ammonia,Benzene and formaldehyde)were also investigated.The experimental results showed that the rGO-doped ZnSnO3 can effectively improve the gas sensitivity of ZnSnO3.Among them,the 4% rGO/ZnSnO3composite had the highest sensitivity to 30 ppm formaldehyde gas(38.9),fast response recovery time(112s,15s)and good selectivity and stability.(3)The ZnFe2O4/ZnSnO3 composites were synthesized via a facile two-step hydrothermal method with subsequent heat treatment.The structure,morphology,and composition of the products were confirmed with XRD,XPS,BET,SEM,DR-FTIR and TEM techniques,and the gas-sensing performance of the composites were investigated comprehensively.The ZnFe2O4/ZnSnO3 composite is consisted by the ZnSnO3 cubic and the urchin-like ZnFe2O4.The as-fabricated ZnFe2O4/ZnSnO3-0.25 gas sensor shows excellent gas-sensing performance toward acetone,including fast response-recovery time(9 s/16 s to 30 ppm acetone),low operating temperature(200?),long-term stability and good humidity resistance.The improved gas sensing performance of ZnFe2O4/ZnSnO3-0.25 composite can be due to its large specific surface area,oxygen vacancy and p-n heterojunction.The results indicate that ZnFe2O4/ZnSnO3-0.25 sensor can be a promising candidate for fast and accurate detection of acetone in respects of the environmental monitoring and human health protection.Finally,the sensing properties and sensing mechanism have been investigated in detail.(4)The ZnWO4/ZnSnO3 composite was prepared by one-step hydrothermal method.The structure,morphology and chemical composition of ZnWO4/ZnSnO3 composites were characterized by XRD,SEM,TEM,BET and XPS.The compound of ZnWO4 and ZnSnO3 enhances the gas sensitivity of formaldehyde gas and has a good gas response(73)to 30 ppm formaldehyde gas,a lower operating temperature(180?)and a fast response recovery time(142s/14s).This unique ZnWO4/ZnSnO3 composite material can be used as a potential gas sensitive material for formaldehyde detection. |
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