The Preparation Of 'Satellite' Like Core Shell Material And Its SERS Application

Surface enhanced Raman scattering?SERS?is a technique that significantly enhances the raman signal of analyte adsorbed on metal nanoparticle.It provides the analytical signals by giving the vibrational spectrum of the analyte structure information.In particular,the SERS enhancement factor contributed by the so-called‘hot spot'effect generated between the adjacent metal nanoparticles can reach a single molecule detection of a test substance of 10¹⁴,thus attracting the attention of a large number of SERS scientists.SERS technology is now favored in chemical analysis of food contaminant detection,biosensing,and environmental monitoring due to its high sensitivity,high accuracy,and ability to quickly obtain fingerprint information of trace substances in complex systems.It is known that the preparation of a suitable SERS substrate material to create more‘hot spots'is an important factor affecting the SERS spectrum signal.Unfortunately,although many metal nanocomposites have been prepared with more‘hot spots'to significantly enhance SERS signals,the accurate location of Paman probes at‘hot spots'is difficult to achieve,thus hampering the application of SERS technology.Aiming to that,novel SERS substrates with the function of accurately positioning of Raman probe at‘hot spots'were designed and synthesized in this thesis.The corresponding research work are summarized as follow.?1?A new type of nanocomposite with core-shell structure was designed and synthesized via the interlinking of polymeric ionic liquids?PILs?.Briefly,the core material of Ag@PILs was firslty prepared using PILs as a modifier.Subsequently,utilizing the unique ion-exhange property of modified PILs,the raw material of AuCl₄^-for the formation of shell material was immobilized onto the outer surface of Ag@PILs.Finally,owning to the in-situ reduction,the core-shell material Ag@PILs@Au with satellite structure was successfully prepared.The corresponding morphology,structure and surface properties of Ag@PILs and Ag@PILs@Au were systematically characterized by UV-vis,XPS and FT-IR.It was found that the modified PILs was not only the important bridging components for the formation of this unique satellite structure assembly,but also played an important role to regulate the overall surface properties of Ag@PILs and Ag@PILs@Au.Due to the anion exchangeability of PILs,the hydrophilicity/hydrophobicity of both Ag@PILs and Ag@PILs@Au can be well controlled.?2?The performance of SERS detection of the as prepared nanocomposites were also investigated.Being an endogenous Raman probe,PILs was found to exhibit the function of expressing‘hot spots'that existed between the inner core of Ag and the outer shell of Au.It was found the SERS signal of Ag@PILs@Au was greatly enhanced in comparision to that of Ag@PILs.More importantly,since the bridged PILs at the‘hot spots'is of reactivity,the exogenous Raman probes,especially those anionic ones can be precisely located at the position of‘hot spot'of Ag@PILs@Au via the anion-exchange reaction.Thereby,the SERS signal could be obtaned with a significant improvement over the traditional SERS signal.Such strategy that locating specific Raman probes precisely at the‘hot spot'may greatly improve the analytical performance of the SERS detection system.