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Published on: March 2, 2016
Dual Optimization of Shell and Interparticle Gaps in Plasmonic Au@Ag Nanocubes Assembly for Hot Spot-Driven SERS
Sajid Muhammad1, Sidra Shujah1, Shanqing Gao2
1Beijing Key Laboratory of Construction-Tailorable Advanced Functional Materials and Green Applications, School of Materials Science & Engineering, Beijing Institute of Technology, Beijing 100081, China.
Abstract:
Surface-enhanced Raman scattering (SERS) allows sensitive detection of low-concentration biomolecules by amplifying Raman signals through plasmonic nanoparticles (NPs) such as Au@Ag nanostructures possessing tailorable surface plasmon resonance (SPR). This study presents a seed-mediated growth approach for the synthesis of monodisperse Au@Ag core-shell nanocubes. Their tunable cubic shell thickness (ts) and self-assembly-induced controlled interparticle gaps (IPG) could act as dual optimization for SPR-enabled SERS enhancement. The thickness of the Ag shell is precisely controlled by varying the AgNO3 concentration. Structural and optical characterizations were conducted by using UV-visible spectroscopy, high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). The uniform assembly-produced IPG was regulated and achieved by tailoring the concentration of the surfactant CTAB. The SERS performance was evaluated using novel antibodies (aCD47) as a probe molecule, demonstrating that SERS intensity can be effectively optimized by tuning the core-shell composition and IPG. The SERS enhancement factor (EF) of ∼5 × 106 was achieved from Au@Ag nanocubes assembly with ts and IPG below 10 nm, highlighting strong electromagnetic hotspot formation. The experimentally observed hotspot generation at different ts and IPG was further backed by numerical simulations using COMSOL Multiphysics.
