Study On The Gas Sensing Properties Of Noble Metals Modified ?-Fe₂O₃ To DMDS

Semiconductor metal oxide gas sensors have many advantages,namely,higher response,low cost,convenient production,quick response/recovery speed and convenient implement,etc.,so it has important usages in environmental protection,food detection,anti-terrorism activities,industrial and medical diagnosis.Pure semiconductor metal oxide is not excellent enough in terms of the gas sensing characteristics.Therefore,in order to enhance the performance of the gas sensors,many means had been developed.One of the most efficacious ways to enhance the performance of existing gas sensors is to use precious metals to modify the surface of metal oxides.In this work,after a simple hydrothermal and impregnation means treatment,?-Fe₂O₃ nanomaterials modified with precious metal PdO,Pt and Au nanoparticles were harvested.The morphology and composition of the obtained materials were analyzed by X-ray diffraction(XRD)and scanning electron microscopy(SEM).Then study the gas sensing properties of these gas sensors.Studies have shown that these materials all respond best to dimethyl disulfide gas.The main content of this article is as follows:(1)Simple hydrothermal method was used to synthesize?-Fe₂O₃nanomaterial,and then the material was modified with PdO to prepare PdO-modified?-Fe₂O₃ nanoparticles.Characterization methods such as XRD and SEM revealed the successful modification of PdO.The gas-sensing outcome disclosed that PdO-?-Fe₂O₃ gas sensor with 1.0 wt%PdO modification exhibited better response(113.1)in detecting 100 ppm dimethyl disulfide than that of?-Fe₂O₃sensor(11.1).Moreover,the modification of PdO reduced the optimal working temperature from 375 ^oC to 335 ^oC,and its response/recovery time is 1 s/68 s.This made the 1.0 wt%PdO-?-Fe₂O₃gas sensor significantly better than the?-Fe₂O₃ gas sensor.The sensing mechanism of enhanced gas sensitivity caused by the synergistic effect of chemical sensitization and electronic sensitization was studied.(2)Nano-scale Pt-?-Fe₂O₃ materials were prepared by impregnation method,its gas sensing properties were studied,and the optimum amount of Pt modification was also obtained to be 1.0 wt%.XRD,SEM and other technologies showed the successful modification of Pt nanoparticles.Compared with the original?-Fe₂O₃,the 1.0 wt%Pt-?-Fe₂O₃ gas sensor had better selectivity to dimethyl disulfide gas,and showed a higher response value(58.6)at the optimal working temperature of 375 ^oC and its response and recovery time were 1 s and 168 s.The sensing mechanism was attributed to the chemical and electronic sensitization between Pt and?-Fe₂O₃.(3)The dipping method was used to modify Au nanoparticles ona-Fe₂O₃,and characterization analysis such as XRD and SEM proved the successful modification of Au nanoparticles.The gas-sensing detection results indicated that for 100 ppm dimethyl disulfide gas,the Au-a-Fe₂O₃gas sensor with 1.0 wt%Au modification displayed a higher response at 335^oC,with the response value of 98.5.In one word,the optimal working temperature of the 1.0 wt%Au-a-Fe₂O₃ sensor was decreased by 40 ^oC,and the response value was increased by 8.78 times.The main mechanism for the enhancement of gas sensing properties was attributed to the electronic and chemical effects of Au nanoparticles,which added the resistance range of the 1.0 wt%Au-a-Fe₂O₃ gas sensor and enhances the response value.