Plasmonic filter paper for preconcentration, separation and SERS detection harmful chemicals in chili product by fluid flow.

We proposed a triple functional SERS substrate by immobilized Ag nanoparticles on the surface of filter paper. The high dense Ag nanoparticles were distributed on the SERS substrate via in-situ growth process. By optimizing the parameter in preparation process, the optimal filter paper SERS substrate was fabricated by using 30 mM of AgNO3 with 20 S growth time. Due to capillary-effect wicking of cellulose fiber, the paper SERS substrate provide simple, fast and pump-free function for transferring analyte onto sharp tip through development of fluid. The fluid flow also brings target concentrate effect within the tip area. Furthermore, the separation feasibility was obtained during the development process of fluid. The preconcentrated effects not only enhanced the SERS signal of analyte, but also improve the fluorescence visible effect. The filter paper SERS substrate was successfully used for separating, concentrating and detecting Sudan dye from chili product, the detection limit could achieve 10-6 M. This study developed a portable, cost-effective and eco-friendly SERS substrate for separating and detecting trace chemical in food.