Highly Sensitive SERS Substrates Based on Au Nanoscale Convex Polyhedrons with Embedded Standard for Trace Analysis

This study presents a novel strategy for fabricating highly sensitive surface-enhanced Raman scattering (SERS) substrates using Au nanoscale convex polyhedrons (Au NCPs) with an embedded standard. The sensitivity and quantitative accuracy of surface-enhanced Raman scattering (SERS) are the main factors that restrict its application. Here, novel Au nanoscale convex polyhedrons (Au NCPs) were designed and fabricated to solve these problems via an embedded standard, including eight pods and six small protrusions. Spherical Au seeds regrew into different sizes of Au NCPs with a face-centered cubic structure. This morphology is due to the dual mechanism of the 4-aminothiophene (4ATP) molecule that serves as an internal standard and a surface ligand regulator combined with the regulatory role of hexadecyl trimethyl ammonium chloride. The results show that Au NCPs were enclosed by high-index {12 91} facets, which greatly improved the local plasma resonance and reduced the lowest SERS detectable concentration of pyrene in standard seawater to 0.5 nM. An effective reference was produced by embedding 4-ATP with a relative standard deviation value less than 2.97% (in the same batch) and 3.92% (between different batches). Our research offers a new strategy for morphological regulation of metal nanocrystals, which is useful for the preparation of highly sensitive SERS substrates and trace analysis. The synthesis method involves using 4-aminothiophene (4ATP) as an internal standard and a surface ligand regulator, combined with the regulatory role of hexadecyl trimethyl ammonium chloride, to regrow spherical Au seeds into different sizes of Au NCPs with a face-centered cubic structure. This process leads to the formation of Au NCPs enclosed by high-index {12 91} facets, which enhance the local plasma resonance and improve the sensitivity of the SERS substrate.