SERS Characteristics Of Metal/Semiconductor Nanocomposites And Their Application In Immunoassay

Surface-Enhanced Raman Scattering?SERS?with the advantages of ultra-high sensitivity,nondestructive and rapid detection has been widely used in the analysis of detection,physics,chemistry,biomedicine and other aspects.Among them,the SERS-based immunoassay was initially used in clinical trials screening for early cancer.At present,the SERS immunoassay mainly includes both labeled and unlabeled immunoassay.And the labeled immunoassay is mainly based on the sandwich structure of"immune substrate-tumor marker-labeled immune probe".Traditionally,substrates and probes are mainly based on noble metal nanostructures,such as gold,silver and copper,which exhibit good SERS activity,but has the disadvantages of shortage of resources,high cost and instability.To further broaden the application of SERS spectroscopy,researchers used metal-semiconductor composites as SERS substrates and obtained more ideal Raman signals,which not only improved the substrate stability,extended the application range of SERS spectra,but also enriched SERS substrate types,which is significant to the exploration of the SERS mechanism.The thesis mainly focuses on the study of SERS characteristics of metal-semiconductor hybrid nanostructures and their application in immunoassays.Firstly,the Au-Ag alloy nanoparticles were prepared by reducing the mixed solution of silver nitrate?AgNO₃,99.5%?and tetra-chloroauric acid?HAuCl₄·3H₂O?and explored their SERS activity.In addition,Ag/AgBr hybrid nanostructure substrates were prepared using the electric displacement method and their SERS activity and stability were studied.Finally,the preparation of Au-Ag alloy nanoparticle immune probes and Ag/AgBr nanostructures immune substrates was performed,and they were successfully applied to the immunoassays of AFP.The thesis mainly consists of five chapters,the first chapter mainly introduces the Raman scattering effect,the SERS effect and its enhancement mechanism,the research on SERS substrate and probe,the application of SERS in molecular detection,and the significance of the topic and the main contents of this thesis are summarized.In the second chapter,the Au-Ag alloy nanoparticles with different compositions of gold and silver were prepared based on the reduction of mixed solution of AgNO₃ and HAuCl₄·3H₂O by sodium citrate.And alloy nanoparticles were modified successfully with Raman-labeled molecules 4MBA on the surface of alloy nanoparticles for SERS detection.In the third chapter,Ag/AgBr hybrid nanostructures were prepared by galvanic replacement reaction.By changing the placement direction and reaction time of silver thin films,Ag/AgBr hybrid nanostructure substrates with different morphologies were obtained and explored their SERS activity and stability.The experimental method overcome the instability of Ag nanostructure in air.The fourth chapter introduces AFP sandwich immunoassay,based on Au-Ag alloy nano-immune probe and Ag/AgBr hybrid nanostructure immune substrates.This experimental result showed that Au-Ag alloy nanoprobes presented good monodispersity,which is significance to the uniformity of SERS signal in detection.And the immunoassay of tumor markers based on the proposed proposal exhibited good specificity,wide dynamic detection range and high detection sensitivity.Compared to AFP immune detection by clinical chemiluminescence immunoassay?CLIA?,test result is very close and only a small error,and it also showed more wide detection range and better detection sensitivity.Last,the fifth chapter summarizes the research work and prospects.