title: Effect of Au and Au@Ag core-shell nanoparticles on the SERS of bridging organic molecules.
abstract: Gold nanoparticles (AuNPs) with about 6 nm size were produced and stabilized with mercaptopropionic acid (MPA) film to produce a monolayer protected cluster (MPC) of AuS(CH(2))(2)COOH. 4-Aminothiophenol (ATP) molecules were introduced to the activated carboxylic acid ends of the film surrounding the AuNPs to produce AuS(CH(2))(2)CONHPhSH MPC. These modified AuNPs were again self-assembled with Au@Ag core-shell bimetallic nanoparticles via the -SH groups to produce an organic bridge between Au and Au@Ag metallic nanoparticles. An unusually strong enhancement of the Raman signals was observed and assigned to the plasmon coupling between the AuNPs and Au@Ag NPs bridged assembly. Formation of AuS(CH(2))(2)COOH and AuS(CH(2))(2)CONHPhSH clusters and AuS(CH(2))(2)CONHPhS(Au@Ag) assembly is confirmed by UV-Vis, reflection-absorption IR spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS), as well as by TEM analysis. The SERS activity of the AuNPs and Au@Ag NPs was tested using the HS(CH(2))(2)CONHPhSH molecule as a probe to compare the effectiveness of monometallic and bimetallic systems. SERS spectra show that Au@Ag bimetallic nanoparticles are very effective SERS-active substrates.
authors.affiliation: Dicle University, Faculty of Arts and Sciences, Dept. of Chemistry, Diyarbakir, Turkey.
authors.forename: Remziye
authors.initials: R
authors.lastname: Güzel
authors.forename: Zafer
authors.initials: Z
authors.lastname: Ustündağ
authors.forename: Haslet
authors.initials: H
authors.lastname: Ekşi
authors.forename: Selda
authors.initials: S
authors.lastname: Keskin
authors.forename: Bilge
authors.initials: B
authors.lastname: Taner
authors.forename: Zeynep Gülşah
authors.initials: ZG
authors.lastname: Durgun
authors.forename: Aybüke A Isbir
authors.initials: AA
authors.lastname: Turan
authors.forename: Ali Osman
authors.initials: AO
authors.lastname: Solak
mesh_terms: D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D015394:Molecular Structure; D050607:Organogold Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010316:Particle Size; D012834:Silver / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013499:Surface Properties
chemical_list: D050607:Organogold Compounds; D012834:Silver; D006046:Gold