[Self-assembly of two kinds of nanoparticles and their surface enhanced Raman spectroscopic study].

Two kinds of nanoparticles(gold nanoparticles and Au core Pt shell nanoparticles) on silicon surfaces which were silanization were electrostatically self-assembled.The density of nanoparticles was controlled by changing the time of the substrate immersed in colloids.The substrate was characterized by scanning electron microscope(SEM),and the results indicated that Au and Au@Pt particles were dispersed on the substrate with mono/submonolayers.The authors used pyridine(Py) as a probing molecule,and surface enhanced Raman spectroscopy(SERS) effect was investigated on pure Au and Au-Au@Pt mixed nanoparticle surfaces under the excitation line of 632.8 nm.The results revealed that there is a significant shift of the two characteristic peaks of Py,but the enhancement factors of Au dropped off precipitously with the introduction of the Au@Pt nanoparticles.The authors attributed this effect to the introduction of metal d-states from the metal,which would serve effectively to quench the surface plasmon excitation necessary for large(electromagnetic) enhancements in Raman spectroscopy.