State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian Province, P. R. China
基金项目：
the National Natural Science Foundation of China(21273182, 21321062, 512053333)
State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian Province, P. R. China
Abstract:
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.
