| The optical fiber SPR sensor based on surface plasmon resonance(SPR)technology has the advantages of small size,high accuracy,no labeling,anti-electromagnetic interference,etc.It is widely used in the fields of biosensing,food safety,medical diagnosis and so on.In recent years,the combination of metals and 2D materials as the typical sensitive layer has gained increased attention As the most representative available 2D material,graphene has a 2D honeycomb lattice of carbon with a sp2 structure and possesses large surface to volume ratio,which is beneficial to the adsorption of the probe aptamer and will further improve the sensitivity of the biosensor.Reducing detection costs is also the goal that has been pursued in fiber SPR research.Among many optical fibers,plastic optical fiber(POF)is cheap,flexible and easy to operate and connect,making it an ideal optical fiber for low-cost sensing.This paper aims to achieve high-performance,low-cost biosensors.Based on optical fiber SPR sensing technology,the following work is carried out theoretically and experimentally:(1)We use plastic optical fiber(POF)as our sensor substrate.The sensing area is selected as D-type.Au film and graphene are selected as excitation materials.A graphene / Au / D-POF sensing structure is proposed,and theoretical simulation is performed using comsol software.The wavelength modulation is used to characterize the sensor performance.The optimal metal layer thickness and graphene layer number are obtained through calculation.(2)Based on the optimal parameters of the simulation,the experimental fabrication of graphene / gold / D-POF SPR biosensor was carried out.Since the core of D-POF is made of PMMA,the traditional method of transferring graphene is not feasible.Therefore,in this thesis,the role of traditional PMMA was replaced by gold film during the transfer process,and the structure of gold / graphene combination on D-type plastic optical fiber was successfully realized.This operation method makes full use of the characteristic that gold can be used as a self-supporting layer for graphene transfer,and can also make the composite gold film and graphene closely contact,effectively reduce the contact resistance,and get closer to thetheoretical ideal model of the sensitive layer.More importantly,the gold film-assisted graphene transfer method can eliminate the complicated PMMA removal step,effectively avoid PMMA remaining on the graphene surface,and maintain the excellent characteristics of graphene.Compared with other plastic optical fiber experiments,the sensitivity of the sensor has been effectively improved.In a certain range of glucose solutions,the sensitivity is 1227 nm / RIU.?(3)Based on the graphene / gold / D-POF SPR sensor,the surface of graphene was further modified.ss DNA was selected as the specific aptamer for the specific recognition of DNA.By monitoring the amount of change in resonance wavelength,the proposed sensor was obtained It has better DNA-specific recognition results,and the detection limit for complementary DNA is10-10 M.The results can be compared with or even better than that of most plastic optical fiber sensors.It also exhibits a satisfactory linear response(R2= 0.996)to a target DNA solution at a concentration of 0.1n M to 1?M,while real-time monitoring of the DNA reaction without labeling the analyte,which indicates that the Research has broad prospects and cost-effectiveness in medical diagnosis. |
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