Effect of Au and Au@Ag core-shell nanoparticles on the SERS of bridging organic molecules

Güzel R., Üstündaĝ Z., Ekşi H., Keskin S., Taner B., Durgun Z. G., ...More

Journal of Colloid and Interface Science, vol.351, no.1, pp.35-42, 2010 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 351 Issue: 1
  • Publication Date: 2010
  • Doi Number: 10.1016/j.jcis.2010.07.039
  • Journal Name: Journal of Colloid and Interface Science
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.35-42
  • Keywords: Bimetallic nanoparticles, Clusters, Surface-enhanced Raman spectroscopy, Transmission electron microscopy, X-ray photoelectron spectroscopy
  • Middle East Technical University Affiliated: Yes

Abstract

Gold nanoparticles (AuNPs) with about 6nm size were produced and stabilized with mercaptopropionic acid (MPA) film to produce a monolayer protected cluster (MPC) of AuS(CH2)2COOH. 4-Aminothiophenol (ATP) molecules were introduced to the activated carboxylic acid ends of the film surrounding the AuNPs to produce AuS(CH2)2CONHPhSH 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(CH2)2COOH and AuS(CH2)2CONHPhSH clusters and AuS(CH2)2CONHPhS(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(CH2)2CONHPhSH 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. © 2010 Elsevier Inc.