Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (8): 1575-1583.doi: 10.3866/PKU.WHXB201506041

• PHOTOCHEMISTRY AND RADIATION CHEMISTRY • Previous Articles     Next Articles

Spherical Au@Ag Nanoparticles for Localized Surface Plasmon Resonance Scanning Probes: Synthesis and Dielectric Sensitivity

Xi. HE,Tong-Dan. TANG,Jun. YI,Bi-Ju. LIU,Fang-Fang. WANG,Bin. REN,Jian-Zhang. ZHOU*()   

  • Received:2015-03-19 Published:2015-08-12
  • Contact: Jian-Zhang. ZHOU
  • Supported by:
    the National Natural Science Foundation of China(21273182, 21321062, 512053333)


The detection sensitivity of localized surface plasmon resonance (LSPR) microscopic probes is mainly determined by the LSPR property of the modified metal nanoparticle at the end of the probe. In this paper, spherical Au@Ag nanoparticles (NPs) with good size uniformity and a thick Ag shell (≥10 nm) were synthesized using the anion-assisted one-step synthesis method in aqueous solution, and the thickness of the Ag shell can be controlled by simply adjusting the molar ratio of Au to Ag in the solution. We characterized the morphology and composition of Au@Ag NPs with different core-shell ratios by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS) line scanning analyses, which confirmed the controllable synthesis of Au@Ag core-shell NPs by this method. Measurement of the dielectric sensitivity of Au@Ag NPs with different core-shell ratios in different refractive index solutions showed that the core-shell nanostructure of 7.5 nm Au@28 nm Ag has the highest figure of merit for detection. Further investigation of the plasmonic properties of a single Au@Ag NP on nonconductive substrates with different refractive indexes confirmed that 7.5 nm Au@28 nm Ag NPs are one of the most suitable candidates for dielectric sensing in LSPR microscopy among the spherical Au@Ag NPs.

Key words: Au@Ag nanoparticle, Anion-assisted one-step synthesis, Surface plasmon resonance scanning microscopy, Dielectric sensitivity, Dark-filed microscopy of single nanoparticle


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