Synthesis And Application Of Gold-silver Core-shell Nanocomposites In Surface-enhanced Raman Scattering

Surface-enhanced Raman scattering(SERS)is a useful technique which could greatly enhance the Raman signal.It possesses the advantages of high sensitivity,favorable selectivity,non-destructive detection,mild detection conditions and multiple determination objections.Herein,it is an ideal method to analyze and detect biological samples such as cells and some bio-tissues.In this work,gold-silver core-shell nanocomposites are novel nanocomposites which are composed of gold nanomaterials as cores and silver nanomaterials as shells.It not only possesses the advantages including good stability and low bio-toxicity of gold nanoparticles,but also owes excellent SERS enhancement ability of silver nanoparticles.In this thesis,a simple and novel synthesis method was proposed to prepare novel goldsilver core-shell nanocomposites,which possessed a gold nanopyramid core and silver nanorod shell.Based on the gold nanopyramid core and silver nanorod shell nanoparticles(Au NBP@Ag NRs),SERS probes were constructed.The prepares nanoprobes could be applied for rapid identification and Raman imaging of living cancer cells through detection of the SERS signal of nanoprobes rapidly.The specific work carried out in this thesis are as follows:1.Stable gold seeds were obtained by a slight heat treatment,and gold nanopyramid nanoparticles(Au NBPs)were following prepared using above-obtained seeds.The length-diameter ratio of Au NBPs could be regulated by changing the volume of gold seeds added in the reaction system,resulting the adjusting of longitudinal plasma absorption peak of the Au NBPs.The reaction conditions were optimized to obtain Au NBPs with uniform morphology and excellent monodispersity.2.Au NBPs were used as nucleus,and then silver atoms could directly deposite on the surface of Au NBPs to grow silver nanorod shells to obtain Au NBP@Ag NRs.The reaction conditions also were optimized to obtain Au NBP@Ag NRs with uniform morphology,good monodispersity and high SERS activity.3.The Au NBP@Ag NRs were employed as the SERS active substrate to link 4-mercaptobenzoicacid(4-MBA),which were used as Raman signal molecules.Moreover,Bovine serum albumin(BSA)and folic acid(FA)were attached on the surface of the nanoparticles,which act as protective layer and targeting molecules respectively.Finally,Au NBP@Ag NRMBA-rBSA-FA probes(SERS activity nanoprobes)for cell recognition and imaging were prepared.The concentration of Raman signal molecules and the concentration of BSA pre-attached with FA molecules were investigated to obtain optimal SERS activity nanoprobes.In addition,the stability and biocompatibility of SERS activity nanoprobes were investigated.4.SERS activity nanoprobes were utilized for the identification and SERS imaging of human gastric cancer cells(MGC-803)and lung cancer cells(A549).The SERS signal of MGC-803 was much stronger than that of A549 cells,indicating that SERS probes could accurately recognize MGC-803 cells.Referring to SERS technology for cells research,the common used method was using metal nanoparticles as SERS enhancement substrate to construct SERS probes and the prepared probes could recognize cells.Then,we could effectively acquire the molecular information of living cells due to the interaction of SERS probes and cells.With the development of SERS technology,the application research of SERS in the cell field has been rapidly developed and achieved many important results.