The Preparation And Sensitive Properties Of Metal Sulfides For Rapid Detection Of VOCs Based On Cataluminescence

Volatile organic compounds（VOCs）can cause human health problems,such as nausea,headache and dry heaving,etc..In severe cases,it can lead to cancer and respiratory diseases,etc.In the past decades,environmental VOCs pollution has become a major environmental problem in urban areas,and achieving the detection of these hazardous gases is of great significance and has been a research hotspot in recent years.At present,the common techniques for the detection of VOCs include gas chromatography,spectrophotometry,high performance liquid chromatography,gas chromatography and mass spectrometer,etc.However,these detection techniques mostly have the disadvantages of large size of instruments and equipment,expensive,complicated and time-consuming instrument operation process.Therefore,the development of a rapid and convenient means to detect VOCs has become a current research hotspot.Cataluminescence（CTL）is an important tool for the detection of organic pollutants that has emerged in recent years,with high sensitivity,fast detection,good selectivity and stability.As a widely used catalytic material,metal sulfides have the advantages of strong catalytic properties,large specific surface area,and excellent adsorption performance,but little research has been reported on the detection of gases by CTL method.In this thesis,a variety of metal sulfides were explored and it was found that VOCs such as acetaldehyde,ether,n-hexane,and carbon disulfide can produce CTL on the surface of metal sulfides.Therefore,four CTL gas sensors for detecting VOCs based on metal sulfide materials were developed and the sensitive characteristics of the sensors were investigated.The details of the study are as follows.1.Flower-like MoS₂ was successfully prepared by hydrothermal method and used as CTL method to detect the gas.It was found that among all the VOCs tested,only when acetaldehyde gas passed through the catalyst surface would produce obvious CTL signal.It has high sensitivity and selectivity for acetaldehyde,and good signal intensity.The response and recovery times are 3 s and 40 s,respectively,which have the advantage of fast response.The optimum operating temperature is 174℃,which is lower than most sensors.The gas sensor system has a linear detection range of 40mg/L to 2000 mg/L with a fitted equation of y=29.825x+127.42（R~2=0.9991）and a detection limit of 3.75 mg/L.In addition,10 common VOCs were repeatedly tested in the selectivity experiments,and only ethyl acetate,acetone,and ammonia showed slight interference,and the remaining gases in the catalyst indicated no CTL response,indicating that this MoS₂ sensor has good selectivity for acetaldehyde.2.Four materials with different ratios of SnS were prepared by controlling the amount of thiourea added so that the tin-sulfur ratios were 1:2,1:3,1:4,and 1:5,respectively.The synthetic materials with different SnS ratios were also tested for their ether CTL performance,and the test results were averaged over the four measurements.It was found that the CTL performance to ether became weaker as the tin-sulfur ratio became larger,and the two-dimensional nanomorphic SnS synthesized under 1:2conditions showed the best CTL performance to ether.In the range of 1.5～60 mg/L,the CTL intensity showed a good linear relationship（R~2=0.9931）with the concentration of ether to be measured,and the detection limit was 0.15 mg/L.In addition,only ethyl acetate,toluene and butanone slightly interfered with it in the selectivity experiments,which proved that the sensor had good selectivity for ether.3.The MoS₂/Bi₂S₃composite nanomaterials were successfully prepared by hydrothermal method and used as sensitive materials for the detection of n-hexane by CTL method.The results showed that the MoS₂ modification can effectively enhance the catalytic luminescence of Bi₂S₃,and the sensitive material has high sensitivity,good selectivity and fast response and recovery for n-hexane,with a response time of 3s and a recovery time of 16 s.In the concentration range of 12～480 mg/L,the CTL signal intensity showed a good linear relationship with the concentration of n-hexane:y=909.18x+1533（R~2=0.9865）,and the detection limit was 1.81 mg/L.In addition,it was used for the detection of 10 different VOCs,and the results showed that except for toluene,isoamyl alcohol,isobutyraldehyde and ethyl acetate,which had weak sensitive signals,it had obvious response signals for hexane,but not for other VOCs,thus indicating that the sensor has good selectivity for hexane.4.The CdS was synthesized by hydrothermal method first,and then the CdS-modified SnS two-dimensional composites were synthesized by water bath method.It was also used as a sensitive material for carbon disulfide detection by CTL method.The results showed that the maximum response to carbon disulfide was improved by a factor of about 2 for the sensor based on the CdS/SnS composite compared with the sensor based on pure SnS.The gas sensor system exhibited a good linearity of CTL intensity versus gas concentration（R~2=0.9974,n=6）with a detection limit of 0.96 mg/L（S/N=3）in the linear detection range of 6.75 mg/L to168.75 mg/L.As a sensitive material for CTL gas sensors,this CdS-modified SnS material exhibits excellent CTL behavior,good selectivity for carbon disulfide,and fast response and recovery,and good sensor stability,proving that the sensor has good application prospects for detecting carbon disulfide.