Study On Gold Nanoparticles Immobilized Excessively Tilted Fiber Grating For Glucose Biosensing

Surface plasmons(SPs)sensors have been widely used in the fields of clinical medicine,food safety,and bio-chemical sensing due to its high sensitivity,rapid-real time and simple preparation.The SPs sensors include surface plasmon resonance(SPR)and localized surface plasmon resonance(LSPR)sensors based on the different modes of SPs.LSPR,is different from SPR,shows the local resonance mode of metal nanostructures(such as particles)and has a high specific surface area,which can provide more opportunities for detecting the binding of low concentrations analytes and metals.At the same time,the interaction between metal nanoparticles and molecules can be detected by the resonance peak shift of the LSPR spectrum.Compared with other sensors,fiber Bragg grating have many advantages such as small size,low cost and excellent biological compatibility.In addition,the excessively tilted fiber grating(Ex-TFG)shows higher surrounding refractive index(SRI)sensitivity and better linear response than other kinds of fiber gratings.Therefore,in this thesis,the biosensor based on the gold nanoparticles/Ex-TFG micro-nano coupling structure was fabricated by combination of the LSPR effect and the Ex-TFG,which can greatly improve the sensitivity of biosensors and reduce the limit of detection(LOD).The main research contents and results are as follows:Firstly,the coupled mode theory of tilted fiber grating was analyzed in detail,and the phase matching conditions and refractive index sensing principle of the Ex-TFG were studied.Finally,the different fiber grating structures were used for detection of different SRI environments.The experimental results indicate that the Ex-TFG is so sensitive to changes of SRI environment,providing foundation for subsequent sensing experiments.Secondly,fabrication and refractive index sensing of the gold nanoparticles/Ex-TFG micro-nano coupling structure.We prepared gold nanoparticles by the a liquid phase method,and fabricated the gold naonparticles/Ex-TFG micro-nano coupling structure by immobilization of the gold nanoparticles onto the surface of Ex-TFG.The SRI sensitivity of the sensor was tested by different refractive index solutions,the results show that the refractive index sensitivity of Ex-TFG after immobilization of gold nanoparticles are significantly improved in comparision to the bare Ex-TFG,which confirms that the SRI sensitivity of sensor can be enhanced significantly by combination of the LSPR effect and the Ex-TFG.Thirdly,investigation on glucose biosensing of the gold nanoparticles/Ex-TFG biosensor.The Ex-TFG based LSPR biosensor was prepared by combining gold nanoparticles and concanavalin A(Con A),wherein the polydopamine(PDA)as an intermediate layer due to its strong adhesive ability.Furthermore,the different concentration of glucose molecules in PBS buffered solution and artificial urine were monitored by the Ex-TFG based LSPR biosensor.The experimental results indicate that the resonance peak of the biosensor exhibits a redshift of about 0.82 nm for glucose detection in PBS environment,and the LOD of the biosensor is as low as about 2.5 n M.The resonance peak has a redshift of about 1.55 nm for glucose detetion in the artificial urine environment,the LOD of the biosensor is as low as about 0.17 n M.Finally,the specificity of the biosensor was verified by comparative experiments.The experimental results show that the biosensor has high specificity for glucose and exhibit potential applications in clinical medicine.