SiO2 Microsphere Array Coated by Ag Nanoparticles as Raman Enhancement Sensor with High Sensitivity and High Stability.

Abstract

In this paper, a monolayer SiO2 microsphere (MS) array was self-assembled on a silicon substrate, and monolayer dense silver nanoparticles (AgNPs) with different particle sizes were transferred onto the single-layer SiO2 MS array using a liquid–liquid interface method. A double monolayer “Ag@SiO2” with high sensitivity and high uniformity was prepared as a surface-enhanced Raman scattering (SERS) substrate. The electromagnetic distribution on the Ag@SiO2 substrate was analyzed using the Lumerical FDTD (finite difference time domain) Solutions software and the corresponding theoretical enhancement factors were calculated. The experimental results show that a Ag@SiO2 sample with a AgNPs diameter of 30 nm has the maximal electric field value at the AgNPs gap. The limit of detection (LOD) is 10−16 mol/L for Rhodamine 6G (R6G) analytes and the analytical enhancement factor (AEF) can reach ~2.3 × 1013. Our sample also shows high uniformity, with the calculated relative standard deviation (RSD) of ~5.78%.