Design and preparation of a recyclable microfluidic SERS chip with integrated Au@Ag/TiO2 NTs

Abstract

In the present paper, we report on the design and fabrication of a recyclable microfluidic SERS chip with an integrated Au@Ag/TiO₂ NTs (gold core silver shell nanoparticles (NPs) with decorated TiO₂ nanotube arrays (NTs)) composite SERS substrate. The stripped TiO₂ NTs with regularly arranged pore structures were prepared on a Ti foil by easy tape lithography followed by anodic oxidation. The Au@Ag NPs were fabricated on the mouth surface and the inner walls of the TiO₂ NTs within a microchannel without clogging via a facile self-assembly chemical plating composite method. Under optimized conditions, the microfluidic SERS chip provided excellent sensitivity to R6G molecules with a detection limit of 10⁻¹⁰ M and a SERS enhancement factor (EF) of 1.15 × 10⁸. Versus single Au NPs, Au@Ag NPs and the Au@Ag/TiO₂ plate, the optimized Au@Ag/TiO₂ NTs showed improved SERS peak intensities for the C–C–C bending (613 cm⁻¹) of 20, 2.3 and 1.6 times enhancement, respectively. The enhancement effect was attributed to both electromagnetic and chemical enhancement. The photocatalytic performance of the Au@Ag/TiO₂ NTs was exploited to recycle the microfluidic SERS chip through UV light photocatalytic purification. The experimental result shows that the microfluidic SERS chip featured high reproducibility and could be used as an efficient SERS detector for many biochemical molecules.