Research On Surface Plasmon Resonance Sensors

Surface plasmon polaritons(SPPs)is an evanescent wave that arise from the coupling of light with collective oscillations of the electrons at the surface of a metal,and highly localized to the interface of the metal/dielectric.Based on SPPs principle,surface plasmon resonance biosensor converts the quantity being measured(input)to another quantity(output)by optical means.After contact with the solution containing the analyte molecule,the resonance condition of the surface plasmons changes due to the influence of the refractive index(dielectric constant)on propagation constant.At this time,the sensor can detect the ambient environment changes accurately and timely.Due to a series of advantages,such as real-time,rapid and non-destructive,surface plasmon resonance biosensor has become a research hotspot.In this thesis,at a wavelength of 633 nm,two kinds of surface plasmon resonance biosensor based on Kretschmann configuration are investigated.Firstly,we established the structure model,and then used the transfer matrix method to analyze the reflectance.Secondly,through parameter optimization,we investigated the influence of the metal layer,different dielectric layer and graphene on performance.Finally,compared with the traditonal structure,the sensitivity of the proposed biosensor can be greatly enhanced,meanwhile the other performance also be superior than others,such as FWHM and figure of merit(FOM).So our biosensor is much more suitable for the biosensor.Follow is the main content of this thesis:(1)The 1st Section gave a brief introduction on surface plasmon polaritons about its basic research theory,the derivation process of surface plasmon polaritons as evanescent wave,dispersion relation of surface plasmons and the condition of matching wave vector was obtained.In order to satisfy the matching of wave vectors,several common ways to excite surface plasmon polaritons were also introduced at last.(2)The physical principle and research method of surface plasmon resonance were introduced in the Section 2.In especial,the transfer matrix method was theoretically deduced in detail.Then we obtained the relationship between structural parameters and optical characteristics of surface plasmon resonance biosensor,such as reflectivity and the electric field distribution and so on.Finally,the performance parameters of SPR biosensor were defined.(3)surface plasmon resonance biosensor with graphene sandwiched between two gold films and zinc oxide as recognition substance in contact with the molecule to be measured was designed in Section 3.In this structure,the introduction of graphene and zinc oxide all contributed to enhance sensitivity.Through parameter optimization,results showed that the highest sensitivity with 222°/RIU for three layers of graphene and 15 nm thickness of zinc oxide is obtained.Compared with traditional similar structure,sensitivity improved about 20%.(4)A surface plasmon resonance biosensor based on graphene-barium titanate nanocomposites with Ag-Au bimetallic configuration was proposed in Section 4.The silver-gold bimetallic structure can also prevent the oxidation of silver film besides sensitivity enhancement.Barium titanate can further enhance the sensitivity due to its excellent dielectric properties.In addition,graphene with unique optical and electrical properties,has strong adsorption of biological molecules and improves SPR biosensor performance.Results showed the sensitivity and quality factor of the proposed SPR biosensor can achieve maximum 294°/RIU and 42.13 /RIU,compared with the reported bimetallic structure,the sensitivity of the proposed bimetallic SPR biosensor is nearly four times that of the biosensor.We believe that the emergence of this structure will be conducive to wide application of SPR biosensors.