Development of promising surface enhanced Raman scattering substrate: Freckled SiO2@Au nanocomposites

Abstract

This paper describes SiO2@Au core–shell nanocomposites (NCs) as an excellent surface enhanced Raman scattering (SERS) substrate in this emerging field. The network of monodispersed silica (SiO2) core of ~430 and 880nm sizes with varying shell thickness from 12–50nm was synthesized. The synthesized freckled SiO2@Au NCs provide much better surface consistency and in tune generate a huge SERS signals enhancement. The study confirmed that the appropriate shell thickness and core size are responsible for the dramatic enhancement of the SERS signal intensities of the analyte crystal violet (CV) molecule by an order of 1012–109. The SiO2@Au core–shell NCs with 880nm core and 30nm shell thickness showed the maximum enhancement in SERS signals of order 1012 using CV analyte molecule while the NCs with diameter 430nm and 20nm shell thickness produced the maximum enhancement of 109 corresponding to 1620 and 1618cm−1 peaks respectively at the excitation wavelength of 532nm. The advantage of choosing freckled SiO2@Au core–shell NCs instead of nanoparticles (NPs) is that the core being dielectric provides additional electric field to Au nanoshell. Thus it generates more domains on the surface, is responsible for the enhancement of SERS signals and has been shown to be excellent substrate for SERS sensing applications. The results showed that the SiO2@Au core–shell NCs with 880nm core and 30nm shell thickness act as an excellent substrate for SERS sensing.