Shell thickness-dependent Au@Ag nanoparticles aggregates for high-performance SERS applications.

Abstract Plasmonic core-shell nanomaterials have attracted great attention and offered wide applications in surface-enhanced Raman spectroscopy (SERS) due to their unique localized surface plasmon resonance (LSPR) characteristics. In this study, the SERS performance of Ag coated Au nanoparticles aggregates (Au@AgNAs) substrate was explored. The fabrication of Au@AgNAs involved using spherical Au nanocrystals of 32 nm in diameter as the seeds, and ascorbic acid was used as the reductant. The thickness of the Ag shell deposited onto the Au surface was finely tuned from 3 to 13 nm by changing the amount of AgNO 3 precursor. Results in this study suggested that the LSPR of the Au core was rapidly attenuated with increasing Ag shell thickness, while the LSPR bands for Ag shell blue-shifted from 390 to 420 nm. Au@AgNAs with the Ag shell thickness of 8.5 nm exhibited excellent SERS activity, which could realize detecting R6G at an ultralow concentration of 1 × 10−12 M. Besides, the prepared Au@AgNAs showed well homogeneity and reproducibility, and the limit of detection of thiram was calculated as 1.09 × 10−9 M, indicating that the Au@AgNAs substrate could be potentially used for high-performance SERS sensing applications. Graphical abstract fx1 Highlights • SERS performance of Au@Ag nanoparticles aggregates (Au@AgNAs) was evaluated. • Conjunction of Au@Ag nanoparticles can generate a large amount of SERS hot spots. • The Au@AgNAs substrate showed excellent SERS sensitivity and reproducibility. • The detection of limit of thiram was down to 1.09 × 10−9 M using Au@AgNAs. [ABSTRACT FROM AUTHOR]