Reliable quantitative SERS analysis mediated by Ag nano coix seeds with internal standard molecule

Nanostructure with an interior nanogap has received much attention in surface-enhanced Raman scattering (SERS). However, controllable synthesis of nanostructure with ultrasmall nanogap and innovative morphology still remains a challenge. Herein, we present a facile seed-mediated route to integrate uniform nanogap in novel Ag nano coix seeds and locate Raman molecules in the nanogap at room temperature. After 20-nm Ag nanoparticles (NPs) modified by Raman ligand 2-naphthalenethiol and coated by polymer shells as cores were obtained, outside Ag shells were formed by in situ reduction on the polymer surface. The SERS properties of these resulting Ag nano coix seeds were systematically explored. More importantly, the novel SERS active substrate exhibited ultrahigh homogeneity, reproducibility, stability, and even a reliable quantitative SERS analysis mediated by internal standard molecules.