Detection of trace Rhodamine B using stable, uniformity, and reusable SERS substrate based on Ag@SiO2-Au nanoparticles

Rhodamine B (RhB) is a kind of basic dye that is harmful to human health. Because RhB is cheap and abundant, it is easy to add it illegally to foods as a colorant. This paper used surface-enhanced Raman spectroscopy (SERS) and core-shell satellite structure Ag@SiO2-Au nanoparticles to detect RhB. We used the prepared Ag@SiO2-Au nanoparticles as SERS substrate to detect the ethanol solution of RhB. The silica shell protected Ag from oxidation and agglomeration and provided a large specific surface area for modified Au nanoparticles. The “hot spots” generated between metal nanoparticles can significantly enhance the Raman intensity of RhB. At the excitation wavelength of 532 nm, the SERS intensity of RhB at 1647 cm−1 has a linear relationship with the logarithm of RhB concentration in the range of 10−4-10−7 M and the limit of detection (LOD) can reach 5 × 10−9 M. Experiments verified the uniformity and stability of SERS substrate, ideal intensity can still obtain after SERS substrate stored for four weeks. Finally, we confirmed the reusability of the SERS substrate. After washing with anhydrous ethanol, the reused SERS substrate still had an enhanced effect on RhB. The prepared substrate can be used to detect actual samples with satisfactory recovery. The above results showed that Ag@SiO2-Au NPs could use as a sensitive, uniform, stable, and low-cost SERS substrate to detect trace RhB.