Immobilization of metal nanoparticles (NPs) on flexible substrates for surface-enhanced Raman scattering (SERS) has received great attention. Anchoring NPs on substrates generally involves the process of surface modification, thanks to its simple, universal, and nondestructive features. 2-Hydroxy-1,4-naphthoquinone (HNQ), a plant-derived compound used to dye hairs and nails, may interact with polyamine or metal ions to form a surface coating. Here, we report the formation of amino-quinone coatings via the co-deposition of HNQ and polyethyleneimine, which provides a functionalized platform to rapidly immobilize Ag NPs on substrates such as a poly(dimethylsiloxane) (PDMS) film to fabricate Ag-PDMS substrates for SERS detection. The detection concentrations are down to 10-8 M for rhodamine 6G. This work expands the system of surface co-deposition and further provides a facile route to prepare a highly efficient SERS substrate.