Optimized the SiO2 thickness in Ag@SiO2 core–shell nanoparticles for surface-enhanced Raman scattering and fluorescence.

Ag@SiO2 core–shell nanoparticles (NPs) have attracted extensive attention for their excellent surface-enhanced Raman scattering (SERS)-fluorescence (SEF) and their potential applications in sensing, biomedicine, and imaging. The thickness of silica shell plays a crucial role in determining the SERS-SEF properties. However, a few studies have been made to synthesize Ag@SiO2 core–shell NPs with controllable thickness of silica shell and systematic research about the optimized SERS-SEF enhancement. Here, Ag@SiO2 core–shell NPs were prepared by a modified one-pot synthetic method via reducing AgNO3 using formaldehyde in the presence of cetyltrimethylammonium chloride and sequentially hydrolyzing tetraethyl orthosilicate (TEOS). The effects of the type of surfactant and the concentrations of NaOH and AgNO3 on the size and morphology of the resulting Ag@SiO2 core–shell NPs were systematically investigated. The thickness of the silica shell could be finely tuned from 9.3 to 38.9 nm by easily adjusting the amount of TEOS. The crystal violet molecule was used for examining SERS and SEF properties of Ag@SiO2 core–shell NPs with different SiO2 thicknesses. The current work will provide guidance for further understanding the growth mechanism of Ag@SiO2 core–shell NPs and how the thickness of silica shell affects the SERS-SEF properties. [ABSTRACT FROM AUTHOR]