| Acetone is a common chemical solvent in industry.Because of its low price and active chemical properties,it has a very wide range of applications in the fields of physics,chemistry and pharmaceuticals.Acetone is volatile,flammable and explosive when exposed to open fire.It has certain toxicity.Long-term contact can cause certain harm to the human body,light dizziness,nausea,weakness,etc.,and heavy injury to the human central nervous system,even permanent injury.As a component of exhaled air,acetone concentration in healthy people is about 300-900 ppb,while in diabetic patients,the concentration is more than 900 ppb,and some even as high as 1800 ppb.Therefore,acetone can be used as a marker to preliminarily determine whether a patient has diabetes or not.Whether it is to detect the concentration of acetone gas around or to judge the existence of diabetes mellitus,it is very important to develop an efficient and accurate method to detect the concentration of acetone.At present,there are several methods to detect acetone concentration,but these methods are very inconvenient.It is necessary to go to a special testing institution or hospital for testing,and the price is expensive.It is impossible to detect acetone around human body at any time and anywhere.According to reports in recent years,we found that gas sensors have the advantages of accurate detection results,low cost,small volume,and can detect the concentration of target gas at any time and anywhere,which is very in line with our requirements.The materials with high sensitivity to acetone,such as TiO2,NiO,SnO2,WO3,ZnO,Co3O4 and Fe2O3 are also very sensitive to acetone.At the same time,we also observed that many oxide materials with perovskite structure are also very sensitive to acetone,such as LaFeO3,SmFeO3,SmMgxFe1-xO3,LaNi1-xTixO3,La0.75Ba0.25FeO3,La1-xPbxFeO3,Yb1-xCaxFeO3 and NdFeO3.On the basis of this,the acetone gas was detected.The main research results of this paper are as follows:1.SmCoxFe1-xO3 was prepared by sol-gel method,and a precious metal Pd element with a mass fraction of 3wt%was doped on this basis.The experimental results show that 3wt%Pd:SmCo0.1Fe0.9O3 has a very high response to acetone,and the detection limit is very low,and acetone with a limit concentration of 0.01 ppm can be detected.In order to reduce the optimum operating temperature of the material for acetone,we introduced UV light during the test with a wavelength of 365 nm,a power of 50 mW and a distance of 15 cm from the sensor element.After testing,we found that the optimum working temperature of the material for acetone was reduced,and the response of the material to acetone was improved.Not only that,the stability of the material to acetone was enhanced during illumination,and the selectivity of the material was also obtained.Strengthened.By testing the exhaled breath of volunteers,we found that 3wt%Pd:SmCo0.1Feo.9O3 can be a potential material for detecting diabetes.2.SmFe1-xMgxO3 was prepared by sol-gel method,and an appropriate amount of Pd element was added in the subsequent sintering process to prepare 3wt%Pd:SmFe1-xMgxO3.Through the test of acetone gas,we found that when the doping concentration x=0.1,3wt%Pd:SmFeo.9Mg0.1O3 has very high sensitivity to trace acetone,the limit concentration of response to acetone can reach 0.01 ppm.In order to reduce the optimum operating temperature of the material,we introduced different wavelengths of illumination,namely 365,410 and 450 nm illumination.We have found that illuminating the sensor with different wavelengths of light during the test will enhance the material's response to acetone and lower the material's operating temperature.Moreover,we have found that different wavelengths of light have different effects on the gas-sensitive response of the material.The shorter the wavelength,the greater the effect on the gas-sensitive performance,and the more the optimal working temperature is reduced.Experiments have shown that the response of materials under illumination is more stable.3.LaFeO3 was prepared by a sol-gel method and tested for its response to acetone gas.In order to enhance the sensitivity of LaFeO3 to acetone,we introduced UV light into the measurement system.The experiment found that the acetone sensitivity of the material was greatly improved during the irradiation.Through the analysis of the dynamic resistance change of the material,we found that when the illumination is introduced,that is,when the gas sensor is irradiated by ultraviolet light,the resistance of the material instantaneously decreases.After a short change,the resistance of the material is maintained at a relatively low level.This is because the forbidden band width of the material is smaller than the photon energy of the incident light,and the material absorbs energy from the light to generate electron-hole pairs,and the increase in the concentration of the holes causes the resistance of the p-type semiconductor to decrease.We also confirmed through the material's response to the exhaled breath of the volunteers that the material can be initially judged to distinguish between healthy people and diabetics.After a month of uninterrupted testing,we found that the material under UV light has very good gas-sensitive stability to acetone.4.SmFe0.9Zn0.1O3 was prepared by sol-gel method,and an appropriate amount of Au element was added in the subsequent sintering process to prepare Xwt%Au:SmFe0.9Zn0.1O3.By XPS characterization,we found that the Au element has two forms of existence in the material,namely Au(4f7/2)and Au(4f5/2).By testing acetone,we found that when X = 2,2 wt%Au:SmFe0.9Zn0.1O3 has the highest response to acetone,and the limit concentration for acetone is 10 ppb.After introducing light of 365,410,450,535,and 590 nm wavelengths in the test environment,we found that the gas-sensitive response of the material was enhanced and the optimal operating temperature was reduced to some extent.The longer the wavelength of the incident light.the weaker the promotion of the gas-sensitive response of the material.When the wavelength is increased to a certain extent,the promotion of the gas-sensitive response of the material is negligible.Through the analysis of the dynamic change of the material resistance,we found that the incident light can reduce the rosistance of the material,which provides a new idea for explaining the reason for the enhancement of the gas sensitivity of the material,and provides a new method for reducing the resistance of the material.Experiments have shown that the gas sensitivity of the material is more stable under light conditions.5.SmFe1-xZnxO3 was prepared by sol-gel method,and an appropriate amount of Pd element was added in the subsequent sintering process to prepare 3wt%Pd:SmFe1-xZnxO3.By testing the acetone gas,we found that when the doping concentration x = 0.1,that is,3 wt%Pd:SmFe0.9Zn0.1O3 has a very high response to a trace amount of acetone,and the limit concentration to the acetone exhibits a concentration of 10 ppb.After comparing the effects of light with wavelengths ?=365,410,450 nm and light with ?=535,590,635 nm on the gas sensitivity of the material,we found light-pair materials with wavelengths ?=365,410,450 nm.The gas-sensitive response has an enhancement effect,which reduces the optimal working temperature of the material;while the light with wavelength ?=535,590,635 nm has little effect on the gas-sensitivity of the material,which is related to the forbidden band width of the material.We conclude that only when the photon energy of the incident light is greater than the forbidden band width of the material,the illumination can affect the various gas sensing parameters of the material,otherwise there is no promotion to the material.Through the detection of exhaled breath of volunteers,we found that 3wt%Pd:SmFe0.9Zn0.1O3 can initially diagnose healthy people and diabetics by detecting the concentration of acetone in exhaled breath.A month's experiment proves that short-wavelength illumination is more conducive to the stability of the gas-sensitive response of the material. |
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