Multiple Simultaneous Detection of Dyes Using Gold–Silver Core–Shell Structures via Surface-Enhanced Raman Scattering in River Water

The rapid development of the textile industry has led to the discharge of large amounts of dyes into aquatic environments, such as rivers and lakes. Long-term exposure to these substances causes many adverse health effects. Therefore, compact, highly sensitive sensors that enable rapid, on-site assessment of water quality have received significant attention. High-performance SERS substrates were successfully fabricated by optimizing and controlling the thickness of the shell of core-shell Au@Ag NPs by using both experimental and FDTD calculations. Results on the individual and simultaneous detection of dyes demonstrate the potential of Au@Ag NPs as substrates for environmental applications, where dyes exist in complex forms. Detection limits for the three organic substances, rhodamine B, crystal violet, and methyl orange, were 1.89 × 10^-12, 6.57 × 10^-13, and 1.08 × 10^-9 M, respectively, demonstrating a significant improvement in sensitivity compared to single Au and Ag NPs. At the same time, tests in Han River water also demonstrated the high applicability of the SERS Au@Ag NP substrate in real samples. This is one of the advances in the development of SERS-based sensors for environmental applications. For the first time, the core-shell Au@Ag NPs were evaluated for their capabilities, including simultaneous detection and sensing in real water samples. This is of great significance in the application of this technique beyond the laboratory scale.