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

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.