Sensitive SERS detection of Rhodamine 6G based on monodisperse Ag and Ag@SiO2 nanocubes

Abstract

The sensitive detection of dye contaminants in aquatic environments represents a significant concern for both ecological balance and human well-being. Surface enhanced Raman scattering (SERS) from Au or Ag nanospheres is commonly used to analyze pollutants. However, precise control of nanoparticle size and shape during synthesis poses a major challenge. Consequently, the sensitivity and reproducibility of Raman signals from these substrates are often insufficient to detect low-level contaminants. In this study, monodisperse Ag nanocubes (Ag NCs) with uniform size were well controled by the polyol method combined with poly(vinylpyrrolidone). Then, an ultrathin layer of silica was coated on Ag NCs to form Ag@SiO₂ NCs to enhance its chemical durability. The results show that the SERS signal of 10^-5 M Rhodamine 6G (R6G) on Ag@SiO₂ NCs substrate is 3 times higher than that of Ag NCs. The SERS enhancement factor of R6G on Ag@SiO₂ NCs reached 1.3x10⁶. Furthermore, the silica shell of Ag@SiO₂ NCs maintained R6G analytical signal stability even after 12 weeks of storage. The high sensitivity and stability identified in Ag@SiO₂ NCs highlight their potential application in monitoring environmental pollutants.