Tilted Fiber Grating-assisted Surface Plasmon Resonance Biochemical Sensors

There are two increasingly important topics in the 21 st century: life medicine and environmental chemistry,which have spawned the research and development of a series of new functional sensors.Biochemical sensing devices and systems combine the knowledge of many disciplines such as physics,biology,chemistry and information technology,and provide precise detection and analysis data of various physical,biological and chemical quantities for biomedicine and environmental chemistry purposes?including clinical diagnosis,environmental monitoring,food quality control,etc.?.The performance of the sensor is especially important throughout the biochemical detection system.Its performance includes specificity,repeatability,detection sensitivity,and response time.In recent years,due to the flexibility,compact size,corrosion resistance,anti-electromagnetic interferences,multi-point multiplexing and many other advantages of optical fibers,research on optical fiber sensors has attracted more and more attention.Through smart structural design and functional material modification,optical fiber biochemical sensors show great potential for developments in both experimental and field measurements.Tilted fiber Bragg grating?TFBG?-assisted surface Plasmon resonance?SPR?technology has attracted more and more attention in the fields of biology,chemistry and medicine due to its outstanding characteristics for high refractive index?RI?resolution,high RI sensitivity and temperature selfcalibration.In this document,we focus on tilted FBG-SPR sensors and mainly do the following works:1.An estrogen 17?-Estrodiol?E2?sensor based on TFBG-SPR with high sensitivity and label-free was designed and developed.The surface of the gold film was modified with thiol-PEG-Desthiobiotin?SH-PEG-DTB?cross-linking agent.SH can bind to the gold surface.DTB can specifically bind to the streptavidin-E2 conjugate?STV-E2?.The combination of DTB and STV-E2 can be dissociated by sodium dodecyl sulfate?SDS?solution.Finally,the label-free and highly sensitive detection of E2 estrogen was achieved.The detection limit was as low as 10 ng/L and the detection time was 400 s.2.A thickness modulated TFBG-SPR sensor for hydrogen peroxide?H₂O2?and blood sugar?D-glucose?was designed and demonstrated.The silver nano-coating on the surface of optical fibers was corroded by H₂O2,which destroyed the excitation conditions of SPR and weakens the attenuation envelope of SPR.The concentration of H₂O2 and the corresponding D-glucose?adding quantitative glucose oxidase to human serum,which catalyzed the production of H₂O2 from the D-glucose?can be accurately obtained by detecting the change rate of SPR decay envelope.The experimental results showed that the detection limit of H₂O2 is up to 0.2 ?g/L and the detection time was 20 minutes.Moreover,the concentration of D-glucose?0 m M-12 m M?in human serum was determined.The results were in good agreement with the traditional electrochemical method,which verified the feasibility of thickness modulation as a new detection method.3.A palladium?Pd?-coated highly tilted FBG-SPR hydrogen sensor was designed and demonstrated.The tilt angle of the TFBG was 23 °.Cladding mode excitation with effective refractive indeices lower than 1.0 RIU can be realized.High efficiency excitation of SPR can be achieved in air by a nano-gold coating.By further depositing a Pd film on the surface of gold film,the sensor's specific sensitive response to H₂ was characterized.Based on theoretical optimization and experimental verification,when the thickness of the gold and Pd films were respectively 30 nm and 7 nm,the TFBG-SPR sensor can achieve a linear response output in the range of 0 and 1.7% hydrogen concentration.The detection limit of hydrogen was 380 ppm.Moreover,the relationship between the dielectric constant of Pd hydride and H₂ concentration was obtained.