Structure Design And Performance Study Of Fiber Optic Surface Plasmon Resonance Biosensor Based On Two-Dimensional Material Sensitization

Plasmonic sensing technology,as one of the most practical and promising single-molecule detection technologies,has a wide range of applications in life sciences,clinical diagnostics and food safety.However,the traditional surface plasmon resonance sensor based on prism is not suitable for clinical diagnosis due to its high cost,large size and difficulty in miniaturization.Combining plasmonic sensing technology with fiber-optic provides an alternative for biosensing with high sensitivity,small size,anti-electromagnetic interference and in-situ detection.Surface plasmon resonance sensors can be divided into two categories:surface plasmon resonance sensors based on surface plasmons polaritons(SPPs)and localized surface plasmon resonance sensors based on localized surface plasmons(LSPs).Both SPPs and LSPs sensor measured the variation of surface plasmon resonance frequency caused by the slight variation of refractive index on the metal/dielectric surface and reflected this microscopic variation in the macroscopic wavelength shift.With advances in science and technology,higher demand being placed on the performance of biosensors:higher sensitivity and figure of merit(FOM),accurate selective detection and lower limit of detection(LOD).To meet above requirements,we proposed a method of combining two-dimensional(2D)materials with 3D structure to improve the performance of the sensor.2D materials refer to materials in which electrons can move freely(planar motion)on the nanoscale(1-100 nm)in only two dimensions.Different two-dimensional materials have different electro-optical properties due to the specific nature of their crystal structure.As the most widely used 2D material,graphene(Gr)has attracted much attention due to its large specific surface area,efficient carrier mobility and chemical inertness.It has been found that Gr is an excellent plasmon sensitizer material and has good biocompatibility,which is suitable for biosensing.With the further exploration of 2D materials,an emerging 2D material,the metal-organic frameworks(MOFs),is well suited as a secondary sensitizer material due to its superior electrical conductivity between MOFs and Au film and ultra-thin properties that allow visible light absorption and thus coupling to the surface plasmon.Here,in order to improve the coupling strength of surface plasmon resonance so as to improve performance parameters and detection capabilities.We made localized surface plasmon resonance fiber sensor based on 3D gold nanoparticles and monolayer graphene film to detect glucose molecules and surface plasmon resonance fiber biosensor based on MOFs/Au film to detect small molecular weight dopamine molecules,respectively.(1)We first prepared and studied a kind of localized surface plasmon biosensor based on D-type plastic fiber.Two kinds of three-dimensional gold nanoparticle(Au NPs)composite structures,n~*(Gr_m/Au NPs)and n~*(Au NPs/Gr_m),were constructed using monolayer graphene as a spacer.Through finite element method(FEM)analysis,the electric field intensity and distribution of the three-dimensional composite structure of Au NPs were simulated,and the experimental test was compared.We found that the arrangement of plasmonic structure units and the number of layers were closely related to the performances of the sensor.Meanwhile,the top layer of the n~*(Gr_m/Au NPs)nanostructure was covered by monolayer graphene forming a graphene hot surface,which provides both an effective uniformly adhesion site for the analyte and enhances the coupling strength of the plasmonic structure.Under the optimal arrangement and number of plasmonic layers,we obtained a biosensor with high sensitivity,high stability and repeatability,and successfully realized the detection of glucose molecules.(2)In order to further enhance the sensing performance of the surface plasmon resonance-based biosensors and to improve the LOD of the analyte.A MOFs/Au film sensitization structure was constructed and applied to a single-mode fiber(SMF).Firstly,the ultrathin 2D MOFs material with large area was prepared by hydrothermal method,and it was uniformly deposited on the SMF coated with gold film by light-induction method.Next,the optimal modification conditions were explored by detecting the performance of the sensor.We found that 2D MOFs can greatly improve the performance of sensor due to its large surface area,excellent photoelectric characteristics and highly biocompatibility.Finally,the high sensitivity and low LOD of small molecule weight dopamine(DA)detection was realized by DNA phase transformation amplification method by changing the amount of refractive index of dopamine molecules.