Research On Ultra-fast Humidity Microfiber Sensor Activated By Three Dimensional Graphene

Optical fiber sensor has attracted much attention because of its high temperature resistance,corrosion resistance,anti electromagnetic interference and other advantages.Many optical fiber structures have been used in the field of optical fiber sensing,among which micro/nano optical fiber has become one of the important waveguide structures in the field of optical fiber sensing due to its advantages of evanescent field strength,high stability signal transmission,small volume,light weight and so on.At present,many optical sensors with micro/nano optical fiber as waveguide structure are widely used in humidity,temperature,refractive index,biology and other fields.With the rapid development of science and technology,real-time humidity monitoring is needed in the fields of agriculture,industry,medical treatment,environmental monitoring and so on.Therefore,it is necessary to develop high-precision and rapid response humidity sensor.Combined with the advantages of micro/nano optical fiber,this paper takes three-dimensional graphene as sensitizing material to make and study ultra-fast humidity microfiber sensor activated by three-dimensional graphene.The research content of this paper mainly includes:1.The graphene oxide / polystyrene composite nanospheres(GO / PS)were prepared by electrostatic self-assembly method,and then the GO nanosheets were reduced to graphene(RGO)by hydrazine hydrate,and the graphene / polystyrene(r GO / PS)composite nanospheres were obtained.The PS nanospheres only play the role of supporting the r GO nanosheets here.The Raman and XPS spectra of RGO / PS composite nanospheres were characterized.2.Three-dimensional graphene microstructure was fabricated on the surface of micro/nano optical fiber by suspension deposition,and an independent three-dimensional graphene microstructure optical fiber is obtained and applied to the field of humidity sensing.The three-dimensional graphene microstructure is the effect of the reduction of graphene oxide / polystyrene(r GO / PS)composite nanospheres by self-assembly on the surface of micro/nano optical fiber.Here,PS microspheres are humidity insensitive materials,which play a role in supporting the threedimensional graphene microstructure.As a humidity sensitive layer,the change of humidity will change the effective refractive index of the three-dimensional graphene microstructure,and finally change the transmission power of the sensor.The high specific surface area and microporous structure of three-dimensional graphene microstructure enhance its interaction with water molecules.The independent mode of micro/nano optical fiber sensor accelerates the absorption and release process of water molecules,which makes the humidity sensor show ultra-fast response time and recovery time.3.The humidity response of micro/nano optical fiber humidity sensor with three-dimensional graphene microstructure was measured.The experimental results show that when the humidity increases from 11.6% RH to 90.9% RH,the transmission power of the sensor decreased by 41.39 d Bm.In the range of 11.6% RH-71.3% RH,its humidity sensitivity is-0.172 d B /% RH,its linear correlation coefficient is 94.9% RH.In the high humidity range of 80.3% RH-90.9% RH,its humidity sensitivity is-2.841 d B /% RH,and its linear correlation coefficient is 96.9%.The influence of the three-dimensional graphene microstructure thickness on the humidity sensitivity of the sensor was investigated.The experimental results show that the thicker the threedimensional graphene microstructure is,the higher the humidity sensitivity of the sensor is.4.The response time and recovery time of ultra-fast microfiber humidity sensor based on three-dimensional graphene microstructure were measured,and the influence of the thickness of three-dimensional graphene microstructure wrapped on the surface of micro/nano optical fiber on the response time of sensor was explored.The response time and recovery time of four samples(S1,S2,S3,S4)with different humidity sensitivity were measured.The results show that the lower the humidity sensitivity is,the faster the response time is.Among them,the sample S4 with the lowest humidity sensitivity shows ultra-fast response time and recovery time.When the relative humidity changes between 10% RH and 90% RH instantaneously,S4 achieves 57 ms response time and 55 ms recovery time.