Design and fabrication of a microfluidic SERS chip with integrated Ag film@nanoAu

Abstract

A “sandwich” microfluidic surface enhanced Raman scattering (SERS) chip with Ag film@nanoAu prepared in a microchannel was proposed and fabricated in situ. The integrated composite Ag film@nanoAu was prepared in situ by way of chemical plating and self-assembly. Firstly, the preparation conditions were optimized. On the basis of that, the influence of the laser focus position along the vertical direction and the materials of the cover plates on the SERS effect were investigated and optimized in detail. The optimized SERS effect was observed when the laser was focused on the interface of the sample and the SERS substrate. The SERS intensity of Rhodamine 6G (R6G) decreased 2.5 times and 2.1 times when PDMS or glass was used as the cover plate separately. Compared to single gold and silver SERS substrates, the composite of Ag film@nanoAu integrated in the microfluidic channel resulted in the peak intensity increasing 3–5 times during the SERS detection of R6G at 1507 cm⁻¹. The enhancing effect could be attributed to the change in the local electromagnetic field which was caused by the synergistic sensitizing effect between the Au nanoparticles and the underlying silver mirror film. It was illustrated that the detection limit for R6G was 10⁻⁸ M and the enhancement factor (EF) was 3.8 × 10⁵ with a relative standard deviation (RSD) of approximately 10% in the as-prepared microfluidic SERS chip.