Polyethyleneimine-mediated seed growth approach for synthesis of silver-shell silica-core nanocomposites and their application as a versatile SERS platform

Abstract

We synthesized silver-shell silica-core nanoparticles (SiO₂@PEI@Ag NPs) with complete silver shells through the proposed polyethyleneimine (PEI)-mediated seed growth method. Cationic PEI rapidly self-assembled on the silica spheres through sonication to form a thin multifunctional interlayer, which can adsorb Au seeds densely and uniformly and stabilize the entire structure. Ag shell formation was completed within 2 min, and generated SiO₂@PEI@Ag NPs were highly uniform in size and shape with nanoscale roughness. The improved seed growth method can be generally used to coat Ag shells of different thicknesses on the SiO₂ cores with any particle size to form a well-dispersed core/shell nanostructure with high SERS activity. SiO₂@PEI@Ag NPs of different sizes could be versatile SERS platforms for different applications. The potential of these particles as SERS substrates was verified by detection of the pesticide thiram and potential as SERS tags was verified by detection of human IgG, with detection limits as low as 10⁻⁹ M and 10 pg mL⁻¹, respectively. Hence, SiO₂@PEI@Ag NPs are powerful tools for practical SERS detection.