The embedding of nanoscopic metal structures into polymeric matrices represents a convenient way to stabilise a controlled dispersion of protected nanoparticles whilst taking advantage of their physical characteristics. Supercritical carbon dioxide (scCO2) has been used to produce silver nanoparticles in optically transparent polycarbonate (PC) matrices allowing fine scale dispersions of particles to be produced within a prefabricated polymer component. Characterization of these nanocomposites has been performed using transmission electron microscopy (TEM) and UV-vis spectroscopy. The substrates give excellent responses in surface-enhanced Raman spectroscopy (SERS) for both 4-aminothiophenol and rhodamine 6G target molecules. They offer significant benefits over more conventional SERS substrates in that they are cheap, flexible, mechanically robust and temporally stable. Post-processing the films via simple etching techniques, provides an additional degree of design control and the potential to fabricate devices with unique excitation and detection geometries for a wide range of applications.