Bowl-like Pore array made of hollow Au/Ag alloy nanoparticles for SERS detection of melamine in solid milk powder

This article presented a facile and productive method to prepare a bowl-like pore array composed of hollow Au/Ag alloy nanoparticles (Au/Ag BPHAN array). It was found that Au/Ag BPHAN array showed the great SERS activity in the detection of melamine molecule. The experimental results for 10 −5 M melamine solution indicated the SERS intensity was about five times larger than that of Ag or Au samples when the ratio of Au to Ag was close to 1:1. Especially, the detection limit was 10 -9 M which was one order of magnitude lower than the reported value in references. SERS enhancement mechanism was the surface plasmon resonance in the alloy nanoparticles as presented in the simulation results by FDTD. To test the performance of the BPHAN arrays in real food samples, the melamine intentionally added to the milk powder was detected. The results showed that the SERS peaks assigned to melamine were very clear and the detection limit was already low to 0.1 ppm, 10 times lower than the tolerance level in infant milk products imposed by FDA of U.S. and 1.5 times lower than the strictest standards in the world, proposed by the Codex Alimentarius Commission in 2012. As far as we know, this was the highest sensitivity record of melamine in solid milk powder by SERS detection.