Study On Surface Plasmon Polaritons Biosensors Based On Excessively Tilted Fiber Grating

The peculiar optical properties of Surface Plasmon Polaritons?SPPs?make it widely used in various fields such as biomedical imaging,sensing,electrochemistry,optoelectronic devices,etc.The Surface Plasmon Resonance?SPR?is the research hotspot which is induced by SPPs.There are two types of surface plasmon resonance in terms of the dispersion relationship,the one is Localized Surface Plasmon Resonance?LSPR?and the other one is Propagating Surface Plasmon Resonance?PSPR?.Traditional SPPs-based sensors have some defects such as low sensitivity and bulkiness.Among the fiber grating sensors at present,the tilted fiber grating?TFBG?has absolute advantage in the sensing field due to its high sensitivity,label-free detection,and device simplification.Specially,the Excessively Tilted fiber grating?ExTFG?has stronger polarization and higher sensitivity than the Tilted fiber Bragg grating?TFBG?.In this paper,the combination of the ExTFG and SPPs to fabricate biosensors with high sensitivity is the research theme.The following three portion are studied:?1?The refractive index sensing characteristics based on ExTFG-LSPR.The ExTFG-LSPR sensor was fabricated by modifying the surface of ExTFG with gold nanoshells and star-sharped gold nanoparticles respectively.By comparing the refractive index sensing characteristics of two types of ExTFG-LSPR sensors,the wavelength refractive index sensitivity of the TM and TE mode of ExTFG-LSPR sensor modified by star-sharped gold nanoparticles were increased by¹5.52nm/RIU and¹2.8nm/RIU,respectively,but the resonance absorption effect was not obvious.However,under the effect of LSPR,the wavelength refractive index sensitivity of the TM and TE mode of ExTFG-LSPR sensor modified by the large-size gold nanoshells were improved by³1.1nm/RIU and²6.99nm/RIU respectively.At the same time,the TM and TE mode exhibited strong resonance absorption in the C-L band,and the intensity refractive index sensitivity is¹0.17dB/RIU and¹3.1dB/RIU,respectively.In addition,after studying the Short-band spectrum of sensor,near the absorption peak of gold nanoshell,the intensity refractive index sensitivity of TM and TE mode was²3.8dB/RIU,³2.98dB/RIU,respectively,which indicated that the position closer to the absorption peak of gold nanoparticle,the more significant the LSPR resonance absorption.?2?BSA molecular detection based on ExTFG-LSPR biosensor.On the basis of the prepared ExTFG-LSPR sensor,the surface modified with the specific anti-BSA-MAb to constitute the specific biosensor,which is used to detect different concentrations of BSA solution.The experimental results show that the LOD of the sensor reached to⁰.075pM,and the Langmuir adsorption model was satisfied between the resonance wavelength offset and the BSA concentration level.According to this model,the dissociation coefficient and the affinity coefficient of the biosensor are calculated to be¹.6×10^-1414 M,⁶.25×10¹33 M^-1,respectively.In addition,though the specific experiment studied,the sensor has good specific recognition ability for BSA molecules.The research in this experiment provides a new method for bioassay.?3?Sensing performance and biomolecular detection of ExTFG-PSPR sensor.The refractive index sensing experiment was carried out by coating the gold film on the surface of ExTFG with a small scale sputtering chamber.By comparing the spectra of bare ExTFG and ExTFG-PSPR,it demonstrates that only TM mode can unite the surface plasma wave on gold film to excite the PSPR effect.Meanwhile,the wavelength refractive index sensitivity of the TM and TE mode of ExTFG-PSPR after gold deposited were increased by¹6.2 nm/RIU,¹2.5 nm/RIU.The surface of prepared ExTFG-PSPR sensor modified with anti-BSA-MAb was used to detect different concentrations of BSA,during the whole detection process,it preliminarily proved the feasibility of specific detection of the biomolecules.