Facile periodic hierarchical plasmonic arrays with high-density hotspots for SERS analysis

Engineering high-density hotspots is of crucial importance in surface enhanced Raman scattering (SERS). Herein, based on a self-assembled polystyrene (PS) sphere template, we present a facile and effective fabrication method to construct a large-area hierarchical plasmonic array with rich nanogaps by directly anchoring high-density Ag nanoparticles (NPs) onto the low surface energy perfluorodecanethiol (PFDT)-modified Ag nanocap (ANC) array through simple thermal evaporation. Multiple plasmonic coupling provides high-density hotspots in the proposed Ag NPs@PFDT/ANC hierarchical array, promoting a high SERS performance with remarkable sensitivity (limit of detection∼10^-10 M for R6G), excellent reproducibility (RSD less than 8.6%) and angle-independent in SERS detection. Furthermore, the Ag NPs@PFDT/ANC array can be manufactured on a flexible substrate, demonstrating highly sensitive detection of the toxic organic pollutants in tap water and excellent mechanical stability. These render the Ag NPs@PFDT/ANC array a promising candidate for potential applications in food safety assessment and environment monitoring.