Synthesis Of ZnSnO₃ Hollow Microspheres-based Composites Materials And Their Applications In Acetone Detection

With the development of industrialization and urbanization,environmental problems become more serious and attract contract attention from people due to the increasing number of toxic volatile organic compounds?VOCs?.Acetone,as one kind of VOCs,is flammable,explosive and toxic.When its concentration reaches a certain value,it is dangerous for the health and property of people.Additionally,acetone is also an essential organic chemical raw material solvent,which is widely used in many fields.Thus it is vital to realize the real-time online acetone detection.Moreover,acetone is also deemed to biomaker for diabetic patients,and the detection of acetone also plays a significant role in the treatment of diabetes.Gas sensors are cheap,portable,real-time,fast and so on in practical applications.Thus they will play a more and more important role in the acetone detection.Gas sensing materials are a key part of gas sensors,thus their design and regulation are vital in applications of gas sensors.Currently,the main approaches of regulation include the doping of precious metals,the preparation of multicomponent composites and the hollow and hierarchical structure.In this topic,we focus on the preparation of multicomponent composites with hierarchical structure based on the ZnSnO₃ hollow microspheres.It is mainly related to the fact that ZnSnO₃,as one kind of typical calcium and titanium mineral,possesses excellent electrical and chemical properties,and the gas sensors based on its hollow structure shows better gas sensitivity.However,gas sensors fabricated by single metal oxide still exist limitations in the gas sensing performance.Therefore we adopt the ZnSnO₃ hollow microspheres as a substrate,then dope with different metal oxides?SnO₂,?-Fe₂O₃?to prepare by multicomponent hierarchical structure,and investigate their gas sensing properties,especially acetone gas sensing performance.It will be potentially applied for acetone detection in the future.The main research contents are as follow:?1?A kind of novel ZnSnO₃/SnO₂ hollow urchin nanostructure was prepared by a facile,eco-friendly hydrothermal method.The results revealed that many SnO₂nanowires with the average diameter of 5 nm uniformly grew on the surface of the as-prepared ZnSnO₃/SnO₂ hollow urchin nanostructure.Via adjusting the doping ratio of SnO₂,ZnSnO₃/SnO₂ hollow urchin nanostructures with different SnO₂ content also were successfully prepared.After changing the experimental parameters and analyzing characterization data,the possible growth mechanism of ZnSnO₃/SnO₂hollow urchin nanostructures was also put forward.Moreover,the gas-sensing performance of as-prepared samples was investigated.The ZnSnO₃/SnO₂ hollow urchin nanostructures showed high response,enhanced selectivity,satisfying repeatability,and good long-term stability for acetone detection.Specially,the 10wt%ZnSnO₃/SnO₂ hollow urchin nanostructure exhibited the best gas sensitivity?17.03 for 50 ppm acetone?,may be a suitable biomarker for the diabetes patients.It could be attributed to its large specific surface area,complete pore permeability,and increase of chemisorbed oxygen due to the doping of SnO₂.?2?The unique ZnSnO₃/SnO₂ concave micrcubes with different amount of SnO₂ were prepared via a simple hydrothermal reaction.The results showed that many SnO₂ nanoparticles were uniformly anchored in the harsh surface of concave microcubes and the number of chemisorbed oxygen species increased.In order to explore the formation of ZnSnO₃/SnO₂ concave microcubes,we adjusted experiment parameters,presenting the important role of Na₃C₆H₅O₇·2H₂O and Sn⁴⁺in formation of concave microcubes.In applications,The acetone sensing performance of ZnSnO₃hollow microspheres and ZnSnO₃/SnO₂ concave microcubes were tested,which showed the 10 wt%ZnSnO₃/SnO₂ concave microcubes exhibited the highest response?18.24?to 50 ppm acetone at 260°C,which is 2.3 times higher than that of ZnSnO₃hollow microspheres.Additionally,the obtained results also displayed its fast response/recovery time?3 s/15 s?,good reproducibility and selectivity,and long-term stability.It is believed that 10 wt%ZnSnO₃/SnO₂ concave microcubes are suitable candidate for the acetone detection.The reasons for enhancement in acetone sensing properties are also discussed according to the gas sensing mechanism.?3?The double-shell ZnSnO₃/?-Fe₂O₃ hollow microspheres were prepared by a simple two-step liquid-phase reaction.The results revealed that many?-Fe₂O₃nanowires with diameter of about 2.5 nm and length of about 30 nm,were anchored on the surface of microspheres,and the diameter of double-shell ZnSnO₃/?-Fe₂O₃hollow microspheres was 1.1±0.1?m.Moreover,the acetone gas sensing performance of ZnSnO₃ hollow microspheres,pure Fe₂O₃ and double-shell ZnSnO₃/?-Fe₂O₃ hollow microspheres was tested.The obtained results indicated that the gas sensing properties of double-shell ZnSnO₃/?-Fe₂O₃ hollow microspheres enhanced compared to ZnSnO₃hollow microspheres and pure Fe₂O₃.To 50 ppm acetone at their optimal working temperature,the response of double-shell ZnSnO₃/?-Fe₂O₃ hollow microspheres was up to 14.24,which was 1.7 times and 3.8 times higher than ZnSnO₃ hollow microspheres and pure Fe₂O₃,respectively.The enhancement in gas sensing performance may be ascribed to high surface area,porous and loose nanostructure and the Schottky junctions between ZnSnO₃ and?-Fe₂O₃.