Triethylamine Gas Sensitive Properties Of Noble Metal Pt Modified Oxide Semiconductor

Triethylamine（TEA）is a colorless,irritating odor,flammable poisonous and harmful gas.Long-term exposure to a certain concentration of TEA or short-term exposure to a high concentration of TEA can cause dizziness,nausea,cough,fainting and even death.In recent years,oxide semiconductor gas sensors have made some progress in the detection of TEA.The oxide semiconductor gas sensor has some problems,such as high operating temperature,low selectivity and poor moisture resistance.Noble metal modification is one of the effective ways to improve the gas sensitivity of MOS sensor.In this paper,TEA gas sensor is prepared with Pt as surface modifier.Specific work contents are as follows:（1）TEA gas sensor based on Pt modified MoO₃Molybdenum trioxide（MoO₃）is a common oxide of Mo element with a band gap of 3.2e V.It is found that MoO₃,as an acidic oxide,has a specific surface interaction with alkaline TEA,which makes it have excellent reaction and good selectivity to TEA gas.MoO₃ nanorods with diameters of 160-220nm were prepared by hydrothermal method.Pt/MoO₃ nanomaterials were prepared by sodium borohydride reduction method.The Pt nanoparticles obtained by reduction method are small in size and uniformly distributed on the surface of MoO₃.According to the gas-sensitive test results,in the test process of triethylamine gas,MoO3-0.2wt%Pt has significantly improved gas sensitivity compared with MoO₃.It showed higher response value of 7.87 to100ppm TEA,lower detection limit of 10ppm,better selectivity,better moisture resistance,good long-term stability,faster response time（11s）.The gas-sensitive properties of MoO3-0.2wt%Pt are attributed to the Schottky barrier formed by Pt and MoO₃,the change of electron depletion layer and the catalytic action of Pt.（2）TEA gas sensor based on Pt modified Cr₂O₃Although the Pt/MoO₃ sensor has good response value,selectivity and stability,the material’s poor moisture resistance makes it unable to be used in a wide range of humidity environments.Compared with n-type oxides,p-type oxide semiconductors mostly have good moisture resistance.Cr₂O₃,as a wide-band gap（Eg=3.4e V）p-type semiconductor,is easily bonded with the amino group in the gas containing ammonia.So Cr₂O₃ is a promising triethylamine sensing material.We use Cr₂O₃ instead of MoO₃to make sensors for sensitive materials.Cr₂O₃ nanoparticles were synthesized by water bath method,and Pt nanoparticles were grown by the same method described above.Electron microscope results show that Cr₂O₃ is a nanoparticle with a diameter of 40-60 nm,Pt is distributed on the surface of Cr₂O₃ in the form of nanoparticles with diameters of about 3～5.5nm.According to the gas sensitive test results,Cr₂O₃-2wt%Pt has higher gas sensitive performance.Its response to 100ppm TEA reaches 200 at the working temperature of 160°C,which is68 times of Cr₂O₃.It also has a lower detection limit～10ppm,good selectivity,stability and other advantages.It is worth mentioning that the response value of Cr2O3 at90%RH is 87%of that at 30%RH.However,the response value of Cr₂O₃-2wt%Pt is almost unchanged when the humidity is between 30%RH and 80%RH,and slightly increases when the humidity is higher than 90%RH.This work provides a feasible scheme for the detection of triethylamine under high humidity conditions.In conclusion,the TEA gas sensor based on Pt modified metal oxide prepared in this paper has low maximum temperature,good selectivity and stability,excellent moisture resistance,and has a good application prospect in the detection of triethylamine in the environment.The improved sensing performance is attributed to the electron and chemical sensitization of Pt and the Schottky barrier formed between Pt and oxide.