| Surface plasmon polariton(SPP)and localized surface plasmon(LSP)are surface electromagnetic oscillation modes formed by the interaction of free electrons on metal surfaces with external photons.It has wide applications in many fields,such as,improving detection sensitivity,surface enhanced Raman scattering and biochemical sensing.In this thesis,the coupling effect between SPP and LSP was studied to enhance the local electromagnetic field intensity and the sensitivity of optical fiber sensor.The main contents of this thesis are listed as follows:(1)The current research status of optical fiber SPR biosensor was described,and the research status of plasma polariton coupling effect and immunoglobulin detection in biomedical field was analyzed.In view of the limitations of optical fiber sensor in detecting small molecules and lower concentration samples,the SPP/LSP coupling effect was proposed to enhance the sensing performance of optical fiber sensor.(2)The coupling effect between SPP/LSP and LSP/LSP was studied by using the theory of mirror field and the model of dipole electric field distribution.The enhancement of local electromagnetic field caused by the coupling effect was deeply explored from the aspect of electromagnetic field.The causes of the coupling effect excited and the sensitivity enhancement effect were analyzed theoretically.(3)Based on the coupling effect between the gold film and gold nanoparticles,a photonic crystal fiber sensor modified by the gold film and gold nanoparticles was proposed and fabricated.The coupling effect between SPP and LSP was simulated by finite element analysis software COMSOL Multiphysics.The coupling effect between the gold film and gold nanoparticles was explored experimentally.The sensitivity of the sensor is 3915 nm/RIU in the refractive index range of 1.33-1.37.Then the surface of the sensor was biofunctionalized to modify the goat anti-human IgG for the detection of human IgG.The minimum detection limit of 37 ng/mL is obtained.(4)A self-compensating photonic crystal fiber SPR biosensor was designed and fabricated.The sensor is consist of two section of photonic crystal fibers that as a reference channel and a detection channel,respectively.The surface of the detection channel was coated with gold film,graphene oxide film and goat anti-human IgG from inside to outside,to detect the human IgG labeled with gold nanoparticles.The surface of the reference channel was coated with silver film to detect the non-specific adsorption in the experiment,so as to improve the detection accuracy.The refractive index sensitivity is 13592 nm/RIU.The temperature sensitivity of the reference channel and the detection channel are 5.1 pm/? and 8.5 pm/?,respectively.The minimum detection limit of human IgG is 15 ng/mL.(5)The coupling effect between gold nanorods and the gold film was studied.Compared with gold nanoparticles,gold nanorods can generate stronger local electromagnetic fields.The refractive index sensitivity of the sensor is 23205 nm/RIU.The double-channel sensor was used to detect the wavelength shift caused by specific adsorption and non-specific adsorption,respectively.It reduces the detection error caused by non-specific adsorption,improving the detection accuracy.The sensor achieves the minimum detection limit of 8.8 ng/mL.(6)The coupling effect between multi-layer nanoparticles was further explored.Compared with single-layer metal nanoparticles,the coupling effect between double-layer metal nanoparticles plays a more important role in improving sensitivity.The refractive index sensitivity of the sensor modified by double-layer gold nanoparticles and gold nanorods is 15747 nm/RIU and 25642 nm/RIU,respectively.The lowest detection limit of 10 ng/mL and 4.6 ng/mL are obtained,respectively.This thesis mainly explores the coupling effect between SPP and LSP.The plasma coupling model is established through COMSOL Multiphysics,which theoretically illustrates the effect of local electromagnetic field enhancement in improving sensing performance.The photonic crystal fiber is used as the sensing region in the experiment,and the detection performance is improved based on the coupling effect between metal nanoparticles and gold film.At the same time,graphene oxide is introduced to improve the binding amount of biomolecules on the sensor surface.In order to improve the detection accuracy,a selfcompensating structure is proposed to reduce the negative influence of non-specific adsorption on the measurement.Finally,the coupling effect between multi-layer nanoparticles is simulated and analyzed.The influence of multi-layer nanoparticles on the sensing performance is analyzed experimentally.The innovations of this thesis are listed as follows:(1)A photonic crystal fiber sensor based on the co-modification of gold nanoparticles and graphene oxide is fabricated to reduce the influence of temperature fluctuation on the detection.At the same time,gold nanoparticles and graphene oxide can enhance the coupling effect and increase the binding amount of antibodies on the sensor surface.(2)A dual-channel optical fiber sensing structure with self-compensation function is proposed.The detection channel is used for specific detection,and the reference channel is used to reduce the detection error caused by non-specific adsorption,so as to improve the detection accuracy.(3)The coupling effect between gold nanorods and the gold film is investigated.The coupling effect between multi-layer gold nanoparticles is also studied,which further improves the detection sensitivity and reduced the detection limit. |
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