Study On Gas Sensing Capability Of Titanium Sulfide Nanocoated Thin Core Fiber-Mach-Zehnder Interferometric Gas Sensor

Sensor is the tool for ascertaining and understanding the nature,and it is applied to all areas of life.With the popularity of optical fiber in recent years,the characteristics of optical fiber was applied to sensing direction in more and more cases.Among them,the application of fiber-optic sensor which based on gas sensing is particularly prominent,especially the sensitivity and detection limit of the toxic and harmful gases which are H₂S,CO,CO₂,NH₃,SO₂.In order to avoid the serious harm to production and life which is caused by poisonous and harmful gas,so it is very important to research and manufacture more accurate and reliable optical fiber gas sensors.By understanding the frontier research directions in recent years,we can see that the researchers construct the optical fiber interferometer by welding special fibers or using special welding technology so that the original light source waveform can be transformed into an interferogram capable of having external information through an interferometer structure,so the interference spectrum will change while external information changing,and finally the sensor can measure the external information.In addition,the application of such optical fiber interferometer to the detection of refractive index,pressure,gas and other material information has emerged in recent years.Lamellar tungsten disulfide is a two-dimensional structural material,when the bulk tungsten disulfide into two-dimensional structure,the electronic band structure from indirect band gap to direct band gap so that its light,electricity and other properties occur a big change.Two-dimensional transition metal disulfides have many similar or even superior properties to graphene,especially in the field of electronic devices,and the prospects of their applications in transistors,lithium-ion batteries,sensors and photocatalysis are also very broad,known as the"graphene"in the semiconductor industry,will surely become the focus of research for some time in the future.The main research work of this paper is as follows:1.Through the use of Furukawa S178A fusion splicer,the best parameters of the lowest splice loss of special thin-core optical fiber and ordinary single-mode optical fiber were studied.The construction that single-mode optical fiber did not match the core of the special thin-core optical fiber was welded successfully.Mismatched Mach-Zehnder Fiber Interferometer is constructed.2.The theoretical mode field analysis of optical fiber interferometer is carried out,and the thin-core optical fibers of different lengths are welded to compare the variation rules of their waveforms.The optical interferometer with the proper length is obtained as the experimental interferometer through theoretical analysis.3.The flake tungsten disulfide is formulated into a dispersion liquid and is coated on the outer surface of the thin-core optical fiber with the coating removed.The hydrogen sulfide gas sensor is obtained by single-calcination and multiple-calcination respectively.The film thickness was characterized as 2.5?m and 320nm respectively.4.Different concentrations of hydrogen sulfide gas are arranged by dilution method,and different concentrations of hydrogen sulfide gas are introduced into the gas chamber to make full contact with the gas tungsten disulfide gas sensing film.Corresponding relations between changes of interference spectra and different gas concentrations are observed,The sensitivities obtained from single calcination and multiple calcination were 3.47 pm/ppm and 18.37 pm/ppm,respectively.5.Cu nanoparticles were deposited on the surface of the gas-sensitive tungsten disulfide film,and the sensitization of the previous hydrogen sulfide optical fiber interference sensor was successfully achieved with the catalytic adsorption of hydrogen sulfide gas by Cu nanoparticles with a sensitivity of 29.30pm/ppm.6.The first principle was used to calculate the adsorption energy of flaky tungsten disulfide on four kinds of gases,including hydrogen sulfide gas.The specific selectivities of the gas sensors to tungsten sulfide gas in the previous sections were verified.