Improved Raman and photoluminescence sensitivity achieved using bifunctional Ag@SiO2 nanocubes

Abstract

SiO₂ coated silver nanocubes Ag@SiO₂ with enhanced surface-enhanced Raman scattering (SERS) and metal enhanced photoluminescence (MEPL) sensitivity were synthesized and characterized. The silver nanocubes (NCs) were synthesized by the polyol method and modified, first with different coupling agents, such as 3-mercaptopropyltrimethoxysilane (MPTMS) and 3-aminopropyltrimethoxysilane (APS), and secondly with tetraethylorthosilicate (TEOS) to improve their SERS and photoluminescence (PL) performances. The SERS and PL intensity of rhodamine 6G (R6G) can be manipulated by tuning the Ag nanocube's SiO₂ shell thickness. Modified Ag NCs (with a 2 nm silica layer) were prepared using 1 mM APS and 1 mM TEOS and found to have a SERS intensity 3 fold higher than bare Ag NCs. Additionally, it was found that APS modified Ag@SiO₂ NCs possessed both enhanced SERS and PL intensities.