Surface‐enhanced Raman spectroscopy solution and solid substrates with built‐in calibration for quantitative applications

Abstract

AbstractQuantitative analysis is a significant step forward for expanding the applications of surface‐enhanced Raman spectroscopy (SERS) in various fields. The reproducibility of the SERS measurement relies on the quality of the SERS substrates. Therefore, high enhancement SERS substrate with high uniformity and reproducibility is highly demanded for quantitative analysis. However, it remains a challenge to realize all the requirements of the SERS substrate. Here, we report 2 types (solution and solid) of SERS substrates with built‐in calibration for quantitative analysis. To prepare the substrates, high monodisperse Au@Ag nanocuboids (NCs) with internal standards trapped between the Au core and Ag shell are synthesized through the Au‐nanorod‐mediated method. It is demonstrated that at least 2 types of SERS tags can be trapped to synthesize the core‐internal standard‐shell (CISS) NCs. The SERS quantitative ability of the CISS NCs in solution is proved by detecting Rhodamine 6G, where a good linear relationship in a wide concentration range from 3 × 10−11 M to 1 × 10−8 M is achieved through the built‐in calibration. Besides the solution‐SERS substrate, CISS NCs are self‐assembled at the air–water interface to form uniform monolayer as the solid SERS substrate. SERS mapping reveals that the uniformity of the enhancement is improved through the built‐in calibration. The quantitative detection of concentration of Rhodamine 6G is achieved through the calibrated SERS mapping of the substrate. The internal and external enhancement factor calculation of the 2 types of SERS substrates indicates the promising method to further improve the reliability of the SERS analysis.