Fabrication of sea urchin-like Au@SiO2 nanoparticles SERS substrate for the determination of malachite green in tilapia

• SG@SiO 2 NPs were successfully constructed by coating an ultrathin SiO 2 shell on sea urchin-like gold nanoparticles. • SG@SiO 2 NPs have abundant “hot spots”, superior dispersion, high sensitivity and stable signal intensity. • A high SERS reproduced and sensitive detection method for MG in tilapia has been developed. The quantitative determination of malachite green (MG) is of great importance in aquatic product safety. Although it has been testifying that sea urchin-like gold nanoparticles (SGNPs) have good enhancement effect, the practical application remains challenging for surface-enhanced Raman spectroscopy (SERS) due to poor stability. Here, sea urchin-like Au@SiO 2 nanoparticles (SG@SiO 2 NPs) is designed and synthesized through a controllable and surfactant-free hydrothermal method to improve its stability. The morphology of SG@SiO 2 NPs and the SiO 2 shell thickness were adjusted to obtain good SERS performance. The SERS signal intensity was linear for MG, crystal violet (CV) and methylene blue (MB) at 1619 cm −1 , 1623 cm −1 and 1627 cm −1 over the concentration range of 10 −5 -10 −9 M, 10 −5 -10 −9 M and 10 −5 -10 −8 M, respectively. The substrate was easily used for MG detection with limit of detection (LOD) as low as 1.5 × 10 −9 M. The recovery of MG added to several tilapia fillets samples at different concentrations ranged from 90 % to 110 %. Results indicated that SERS substrate can be used for the determination of trace amounts of MG in tilapia and demonstrated the potential of SG@SiO 2 NPs SERS substrate in food analysis fields.