Design Of Gas Sensor Based On Optical Fiber SPR And Its Application In Hydrogen Sulfide Gas Monitoring

With the rapid development of industrial society,sensor technology plays a more and more important role in people’s life.The core function of sensor technology is to indirectly convert the direct changes of external physical quantity,chemical quantity and biomass into the changes of digital signal through the sensor.People can detect the changes of external parameters by establishing the sensing equation between the two changes.Among them,optical fiber surface plasmon resonance(SPR)sensing technology has developed into a very efficient and advantageous technology.Optical fiber SPR technology has the characteristics of fast response,high sensitivity,anti electromagnetic interference and online real-time detection.This technology has been widely studied in the field of biochemical detection,but there is relatively little research on optical fiber SPR sensor in the field of gas detection,especially in the detection of toxic and harmful gases such as hydrogen sulfide.In this paper,the coreless optical fiber SPR refractive index sensor is studied theoretically,and two kinds of optical fiber SPR gas sensors are prepared to detect hydrogen sulfide.The main research work is as follows:(1)The simulation model of transmission coreless optical fiber SPR sensor is established,and the effects of single incident mode,multi-mode incident mode,metal layer thickness distribution and sensing area length on the performance of optical fiber SPR sensor are studied.The results show that when the incident angle is greater than the total reflection angle,the smaller the incident angle,the greater the sensitivity and the lower the quality factor.When the thickness of the uniform metal layer is constant,the sensitivity and quality factor decrease with the increase of the length of the sensing area.When the length of the sensing area is certain,the sensitivity and quality factor increase with the increase of the uniform metal layer.In addition,the linear change rate of sensing area length and non-uniform metal layer thickness increases gradually,which also increases the influence on sensitivity and quality factor.(2)Silver/3-Aminpropyltriethoxysilane/modified graphene composite cuprous oxide(Ag/APTES/Cu_xO(x=1,2)-MGS)coated coreless optical fiber SPR hydrogen sulfide gas sensor was prepared and characterized.The experimental results show that in the range of10-100 ppm,the resonance wavelength shifts red with the increase of hydrogen sulfide concentration.The total wavelength shift is 132.6425 nm.In the range of 10-40 ppm,the linearity is 0.99594 and the detection limit is about 0.56±0.12 ppm.The response time is about 27 s.The sensor has excellent selectivity,temperature and humidity stability,and continuous stability up to 12 h.(3)Silver/3-Aminpropyltriethoxysilane/copper modified multi walled carbon nanotubes(Ag/APTES/Cu-MWCNT)coated single-mode optical fiber SPR hydrogen sulfide gas sensor was prepared and characterized.The test results show that in the range of 10-100ppm,the resonance wavelength shifts red with the increase of hydrogen sulfide concentration,and the total wavelength shift is 126.465 nm.The relationship between the resonance wavelength shift and hydrogen sulfide concentration is logarithmic.In the range of 1-10ppm,the total wavelength drift is 117.421 nm,the resonance wavelength drift meets the linear relationship with the concentration of hydrogen sulfide,the linearity is 0.99422,the sensitivity is 12.9849 nm/ppm,and the detection limit is about 0.146±0.031 ppm.The response time is about 28 s.The sensor has good time,temperature and hμmidity stability and excellent selectivity for hydrogen sulfide.