The Preparation,Properties And Application In Biosensoring Of AU-AG Bimetallic Nanoparticles

Au-Ag Bimetallic Nanoparticles is considered to have a broad application prospect in biological detection field because of their excellent properties of surface plasmon resonance(SPR)and Surface enhanced Raman scattering(SERS).Due to controllable preparation,chemical stability,optical properties,Au/Ag nanoparticles have different advantages and disadvantages in applications.Therefore,Au-Ag composite nanomaterials that make best use of the strong points and bypass the weak points have drawn great attention.It has been shown that Au-Ag bimetallic nanoparticles has more excellent optical,electrical,and catalytic properties,and new features in some cases.In this thesis,we prepared many kinds of Au-Ag bimetallic nanoparticles based on seed-mediated growth and Galvanci replacement reaction,investigated their preparation mechanism and optical properties,and achie'ved a high sensitive detection of the biomarkers of myocardial injury(cTnI)with Au-Ag alloy nanoparticles.The following points are mainly involved in the dissertation:1.Preparation of Au-Ag nanoshuttles via seed-mediated growth method.By using gold nanorods as seeds,the deposition rate of gold and silver elements on the surface of gold nanorods can be adjusted by changing the concentration of glycine in reaction solution,leading to the formation of spindle shell.It has been demonstrated that the shell of nanoshuttles is composed of homogeneous Au-Ag alloy through high resolution transmission electron microscopy(HRTEM)and nitric acid corrosion experiment.In addition,the thickness of the alloy shell can be controlled by the reactional temperature,which increases with the reactional temperature.2.Investigation of the SPR refractive index sensitivity and SERS properties of Au-Ag nanoshuttles.The SPR refractive index sensitivity was calculated from the SPR shifts in the mixtures of water and glycerol.Due to the spindle shape and high silver content,the SPR refractive index sensitivity of Au-Ag nanoshuttles is significantly improved compared to gold nanorods.The SERS activity was measured form the monolayer film of nanoparticles on the surface of silicon substracts.The results showed that Au-Ag nanoshuttles have stronger SERS avtivity than gold nanorods,which increased with the shell thickness.3.Improvement of Galvanic replacement reaction method by stable AuBr2-solution.Stable AuBr2-solution was obtained from the reduction of AuBr4-by ascorbic acid,which came from the ligand exchange of AuCl2-with Br-in solution.Only Br-in halogen family has the ability to stabilize AuI,while other elements such as chlorine and iodine ions doesn't have similar effect.On this basis,using citrate-capped silver nanoparticle as the templates,a comparative study was performed on the structural evolution of Au-Ag nanoparticles during the replacement reaction with AuBr2-and AuCl4-.Uniform Au-Ag nanoshells were gradually formed when AuBr2-was employed,while porous Au-Ag nanoframes are generated by using AuCl4-.4.Method improvement of Raman detection of liquid samples for the accuratly evaluting SERS activity of Au-Ag nanoparticles.Samples were measured in solution directly by Raman spectrometer coupled with an inverted optical microscope,which overcomes the disadvantages of the poor uniformity and time-consuming sample pretreatment.SERS properties of Au-Ag alloy nanoparticles obtained form Galvanic replacement reaction were precisely characterized by this improved method.It is found that,under the same amount of Au ions,the Au-Ag alloy nanoshells exhibit stronger SERS activity than the porous and fragile Au-Ag nanoframes.It indicated that SERS activity reduced with the decrease of silver content in nanoparticles,and the structure also played an important role in SERS activity.5.Realization of high sensitive detection of cardiac troponin I(cTnI)by SERS-based lateral flow immunoassay using Au-Ag bimetallic nanoparticles.Four types of nanomaterials was used to compose the SERS probes for cTnI:Au NPs,Au@Ag NPs,Au@Ag-Au yolk-shell NPs and Ag-Au NPs.Among them,Au@Ag-Au yolk-shell NPs have the strongest SERS activity and realized the semi-quantitative high sensitive detection with the help of Raman technology.The detection limit of cTnI has reached 0.09 ng/mL,which is 50 times of optical or naked eye detection.