Preparation Of Core-shell Particles Assembled System And Its Application In Metal Nano SERS Spectrum

Surface-enhanced Raman scattering （SERS） spectroscopy is mainly used tostudy the phenomena of surface adsorbed molecules to obtain their structuralinformation. Now it has been developed into a very important analytical tool forsurface or interface. According to the electromagnetic enhancement mechanism inSERS theory, unique nanostructures used as SERS substrate play an important role inSERS signal generation. Therefore, novel preparation procedures for SERS substrateshave become an important part in the field of SERS study. Recently, the shell-isolatednanoparticle enhanced Raman spectroscopy （SHINERS） technology has beendeveloped and the SERS technique can be applied conveniently and effectively forvarious surface analyses by using inert shell（eg.SiO₂） coated gold nanoparticles. Atpresent, the technology has been widely used in many fields such as material science,life science, food safety, environmental monitoring and so on.In this paper, Au@SiO₂shell-isolated nanoparticles （SHINs） preparation andcharacterization were presented. As for the silicon source used in the nanoparticlepreparations, Na2SiO3and TEOS were compared. Then Au@SiO₂nanoparticles wereapplied to SHINERS study of4-mercaptopyridine （4-Mpy） molecules adsorbed on thesurface of ZnO powder.Next by combination of wet chemical preparation, chemical self-assembly andseed-mediated electrochemical deposition of metallic nanoparticles, a desired unifomgold nanoparticle array with a proper grain size and distribution could be obtainedconveniently. Furthermore, by using a silane coupling agent to functionalize the goldnanoparticle surface and sodium silicate solution as the precursor of silica, the goldnanoparticle array was coated with an ultrathin silica shell （ca.2⁵nm） by carefullycontrolling the preparation conditions. Such nanostructure holds characteristics ofSHINs. Shell-isolated nanoparticle assembled structure（SHINAS） concept is proposedhere in order to show the difference when compared with SHINs. Stability andrecyclability of the as-prepared SHINAS structure can be improved. It was applied toSHINERS study of4-MPy molecules adsorbed on the surface of ZnO powder similarly.In addition, monodisperse spherical Au@Ag core-shell nanoparticles with Agnanoparticle-like local surface plasmon resonance properties were prepared byseed-mediated growth method. SERS effect of the as-prepared sol was investigated byadding different kinds of electrolyte. Then Au@Ag nanoparticles were modified on asilylation reagent modified ITO surface by self-assembly technique. Its SERSperfromance was evaluated by using it as a SERS substrate for the studies of someamino acids.Novel SERS or SHINERS substrate preparation is very important in SERS field.The work mentioned as above is significant for the exploration of new types of SERSor SHINERS substrates with high stablity and reproducibility, especially for thedevelopment of unique nanostructures suitable for SERS study with moleculesadsorbed on the material surface with weak or non-SERS effect.