Preparation and analysis of the Au-SiO2 multi-layer nanospheres as high SERS resolution substrate

Metallic nanocomposite material is widely used in Surface Plasmon Resonance (SPR) due to its high stability and special optical features which enhance the Surface Enhanced Ramon Scattering (SERS) effect. A novel multi-layered Au-dielectric core-shell structural SERS substrate is proposed. Finite Element Analysis (FEA) simulation shows multi-layer shell-core nanosphere (SiO₂@Au, SiO₂@Au@SiO₂...) can improve Local Field Enhancement (LFE), comparing to Au single-layer nanosphere. That is because multi-layer nanoshpere exists intra-layer coupling besides cavity coupling. Moreover, red-shift can be observed via tuning the thickness of multi-layer nanospheres, which is greatly beneficial to biological detection in near infrared region (NIR). Lastly, these multi-layer nanospheres are synthesised by liquid phase reduction. And high absorbance and red-shift effect are verified with UV-vis absorption spectrum.